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JCAESOKThe official publication of Conservative and

Endodontic Society of KeralaApril 2011 | Vol. 1 - Issue No. 1

Editor in ChiefDr. Ganesh C.

Associate editorsDr. Rajesh PillaiDr. Jothish Ravi

Business ManagerDr Robin Theruvil

Editorial Advisory boardDr. Ravi Varma

Dr. N.O VargheseDr. Kunjamma Thomas

Dr. Baby JamesDr. Radhakrishnan Nair

Dr. V I PaulDr. Mohammed Sagir

Dr. Romel JosephDr. Gene Jacob

Dr. Josey MathewDr. Mohammed Sadique

Dr. Pramod kumarDr. Satheesh kumar

Dr. Thajuraj

Editorial Review panelDr. Beena Rani Goel

Dr. C.V Pradeep.Dr. Ignatius RexDr. DevadathanDr Shiju Cherian

Dr Prashant Dhanpal T.Dr. Pratap M.S

Dr. Mathew VargheseDr. George Jacob

Editorial Office“Swagat”, T. C 2/3601,

Kesavadasapuram, Trivandrum -695004Ph- 09446557487, 09349457487E-mail: [email protected]

www.caesok.org

Contents

JCAESOK • April 2011, Vol. 1, No. 1 •

Guest article

Clinical steps in reducing polymerization shrinkage 7Deivanayagam Kandaswamy, Nagendrababu Venkateshbabu

Original Scientific Articles

Evaluation of the effect of vectris fibers in reinforcing postendodontic restorations- An Invitro Study 10

Jothish Ravi, Pranau Vanajassan, C V Subba Rao

A comparative evaluation of residual monomer release fromthree different composite resins using high performance liquidchromatography 16

Sujathan U-Nu., Deivanayagam Kandaswamy

Comparison of Anti Fungal Efficacy of Three Root Canal Irrigantson Candida Albicans Biofilm - An Invitro Study 22

Afzal.A, Maya Nandkumar, S.Ignatious Rex

Comparative evaluation of dentin shear bond strength with andwithout Sodium hypochlorite application using two adhesivesystems - An Invitro Study 28

Vijay Mathai, N.O. Varghese, Jolly Mary Varughese

Detection and quantification of hydrogen peroxide penetrationduring intracoronal bleaching and its variation by time andtemperature—An Invitro Study 33

K.C. Mariamma, Kurien K. George, N. O. Varghese

A comparative evaluation of the bond strengths of threedifferent resin cements on root dentin and endodontic posts 37

Eva.C.Das, Jolly Mary Varughese, N O Varghese

Case report

Breaking the Canal Code - The Middle Mesial Canal 42Robin Theruvil

Masterspeak

Single visit endodontics - A bird’s eye view 46K. Ravi Varma

JCAESOK

Designing and PrintingNew Multi Offset Printers

For Private circulation only


2

Conservative and Endodontic Society of Kerala

(CAESOK)

President 1st Vice-President 2nd Vice-President

Dr.Baby James Dr.Mohammed Sagir Dr.Devadathan

President Elect Imm. Past President Secretary Joint Secretary

Dr. Radhakrishnan Nair Dr.Paul V.I Dr. Prasanth Dhanapal Dr.George Jacob

Treasurer Editor

Dr.Romel Joseph Dr.Ganesh C.

OFFICE BEARERS

Dr.Gene Jacob Dr.Pradeep C V

Dr.Josey Mathew Dr.Pramod Kumar AV

Dr.Kunjamma Thomas Dr.Prathap MS

Dr.Mathew Varghese Dr.Rajesh Pillai

Dr.Mohammed Sadique Dr.Robin Theruvil

Dr.Satheesh Kumar Dr.Thajuraj PK

Dr.Varghese NO

Executive Committee Members

The CAESOK came into being as an organization on the

28th September 2002. It was the like minded discussions

among a few Endodontists like Dr.Shiju Cherian, Dr.John

Joseph, Dr.A.K.George, Dr.Rajkrishnan and

Dr.N.O.Varghese during the dental conferences and

meetings that led to the idea of forming a society of

Endodontists from Kerala to share their views and

aspirations. These informal chats were followed up with

numerous telephonic discussions. With the sincere

support of Dr.C.V.Pradeep, Dr.V.I.Paul, Dr.Gene Jacob and

Dr.Sivapriyan, the foundations were laid, with the first

meeting of about 60-70 Endodontists from various parts of

Kerala taking place at Hotel Renaissance, Ernakulam on

3rd February 2002.

The name of the society, CAESOK, was suggested by

Dr.N.O.Varghese and the emblem for the society was

designed in the artistic hands of Dr.Ajith Thomas.

With Dr.Kunjamma Thomas and Dr.Baby James joining

the aforementioned team of dentists, these pioneers

formed the group of office bearers at the official inauguration

of the society by the Hon.Justice M.Ramachandran on the

28th September 2002 held at Riviera Suites, Kochi.

Since its inception the society holds a midterm

conference and an annual conference and family meet every

year to further strengthen the bond of friendship and

fellowship as individuals and as a family.


3

It is with immense pride that I begin to pen this

passage. The joy I feel is something akin to that of a

gardener as he watches the first bloom of spring in his

carefully nurtured garden. The efforts have been

tremendous, trials numerous; but even as we

approach a decade of shared enthusiasm to excel and

exceed every expectation, CAESOK stands tall, a

beacon of promise to every Endodontist in the state.

Where else would one find a better source of

consummate academic and social rejuvenation!! And

now we have taken ourselves up to the next milestone

– our very own journal. As this collective dream of

ours takes form, I must applaud our think-tank headed

by Dr. Ganesh for the great esthetic and intellectual

value that defines JCAESOK. However, it is not merely

a fulfilling moment allowing us to get carried away, but

rather a reminder of the immense responsibility

conferred on each of us, one of consistency in

excellence. May the near future see us together

raising JCAESOK to international standards and glory.

I sincerely congratulate and wish the very bestto the editors’ team and all of us who have dreamt,strived for and realized JCAESOK.

Jai CAESOK!

Dr. Baby JamesPresident, CAESOK

President’s messagePresident’s messagePresident’s messagePresident’s messagePresident’s message


4

CAESOK was started in 2002 with an intention ofproviding a platform for members to interact in afamily environment, at the mean time offering ascope for scientific enrichment and updating.

Every year CAESOK conducts 2 programmes,an annual conference and family meet withscientific programmes and a midterm conferenceexclusively for scientific interactions. Invitedspeakers and our own members are invited tolecture on selected important topics.

Bringing out a journal of our own was in ouragenda and I am happy to report that this dreamis being realised now. I wish the editorial teamgreat success for this endeavour.

In 2003, the annual conference was conductedat Poovar, Trivandrum. Dr Kandaswamy ofGovernment Dental College, Chennai was the keynote speaker. In the same year the midtermconference was conducted at Thrissur and Dr PhilipGuettier from France was the resource person whointroduced Protaper and spoke on “RotaryEndodontics”

The annual conference of 2004 was conductedat Kozhikode. Dr Aravind Shenoy from Mangalorewas the guest speaker on “Full Ceramics”. The3rd midterm conference was conducted on boarda boat at Kochi Backwaters. Dr J.I Chacko, Dr B.R.RVarma and Dr Joseph Varghese were the invitedfaculty and the lectures were on “Synergies inConservative Dentistry and other DentalSpecialities.”

In 2005 CAESOK in association with IndianDental Association conducted special one daycontinuing dental education programme atErnakulam. Internationally renowned EndodontistDr James L Guttmann was brought in for theoration. A lecture on “Basics in Endodontics andmanagement of calcified canals” was well attendedand appreciated.

2005 annual conference was conducted atKumarakom. Dr Satyanarayana and Dr UshaSatyanarayana from Rajah Muthiah Dental College,Annamalai Nagar was the faculty. The same yearthe midterm conference was conducted atPalakkad and Dr Balagopal of SRMC, Chennai wasthe invited speaker. An extensive lecture on“Endodontic Failures and Retreatment” was wellattended.

The 5th annual conference in 2006 wasconducted at Varkala. Dr Kundabala Shenoy from

Mangalore was the faculty and there was a lectureon “Recent Trends in Obturation Techniques”.CAESOK also conducted a panel discussion on“Hand Vs Rotary Instruments” at the conference.The midterm conference in 2006 was conductedat Kannur. Dr Raghu Srinivasan and Dr RemyaRaghu from Bangalore were the faculties. Thelecture was on “Post Endodontic Restorations”

In 2007 we conducted the annual conferenceat Munnar. Dr Gopikrishnan from Chennai was thefaculty and spoke on “Surgical versus Non SurgicalEndodontics”. We also had an international facultyDr Jefrey Chang who lectured on “Retreatmentsin Endodontics”.

The midterm term conference of 2008 wasconducted at Kottayam. Dr Siju Jacob was theresource person, who spoke on “Microscopes inEndodontics”. The midterm conference also had alecture and demonstration of “Basic Life Support”by Dr Pradeep Baskar.

The annual conference of 2008 was conductedat Vythiri. The Key note lecture was on“Radiological Aspects in Endodontics” by Dr BeenaRavi Varma from Mangalore.

The Midterm conference in 2009 was conductedat Guruvayoor. An extensive lecture on “All CeramicRestorations’’ was conducted by Dr Yohan Chackofrom Chennai

The year 2010 was a memorable one forCAESOK. We conducted the 24th FODI and 17thIES National Conference at Cochin. We had anarray of International speakers and Nationalspeakers for the event.

The midterm conference for 2010 was held atChanganaserry. The lecture on “Lasers inOperative Dentistry and Endodontics” was by DrArun Kulandaivelu from Chennai.

The annual conference of 2011 was held atPoovar, Trivandrum. The key note lecture was byDr Aravind Shenoy from Mangalore on“Contemporary Endodontics”.

Taking forward its academic interest and toprovide a platform for our members to upgradetheir scientific pursuit, the planned specialityjournal would definitely help postgraduates,teachers and clinicians to keep abreast in ourspeciality. My best wishes for the endeavour

Jai CAESOK

Dr. Prasanth DhanapalHon. Secretary, CAESOK

Secretarys reportON THE SCIENTIFIC ACTIVITIES OF CAESOK


5

Editorial

faced is that there is a lot of research in

our speciality but the number of published

works is very less. The Heads of

Department should take the initiative to

publish the articles and thesis works of

their post graduate students.

We are privileged to have one of the most

popular academician, speaker and clinician

writing our first invited review.

Dr. Kandaswamy has indeed honoured the

journal. His article, I am sure, will be

invaluable to the post graduates and

clinicians alike. This edition would not

have been possible without the unstinting

support given to me by Dr.Rajesh Pillai,

Dr. Jothish Ravi and Dr Robin Theruvil. The

office bearers of CAESOK were very

supportive and also deserve special

mention for their words of wisdom and

motivation.

Like all new endeavours, there are bound

to be hurdles and obstacles, but with your

support and encouragement we can bring

this journal to International standards. We

welcome constructive criticism from all our

readers to help us better our efforts

because there is always scope for

improvement.

Let us strive to be the leading light for

generations to follow.

Dr. Ganesh C.Editor in Chief

Reader, Dept. of Conservative and Endodontics,PMS College of Dental Sciences and Research,

Trivandrum

“The only thing worse than being blind ishaving sight but no vision.”

-Helen Keller

A journal is the mirror of any association.

CAESOK is a vibrant association of

Conservative Dentists/Endodontist from

Kerala, with eminent academicians and

clinicians par excellence. It has been

growing from strength to strength, but

one thing missing was an Official Journal,

which has been fulfilled with the launch of

JCAESOK. The Vision of CAESOK since its

inception has been to progress knowledge

with a touch of family values and the way

CAESOK has impressively grown in the last

decade is testimonial to the fact that we

are in the right direction. Leadership from

the seniors and dynamism from the young

blood has been extraordinary and

hopefully that will continue to be its forte.

With numerous dental schools in Kerala

now offering post graduate courses in

Conservative Dentistry and Endodontics,

the presence of this Journal should

motivate them to publish more of their

research works. One of the problems


6

Dear friends in CAESOK,

It gives me immense pride and pleasure to address

you as The President of FODI. CAESOK as we all

know has taken its roots in a humble way. We all

watched the congregation grow from strength to

strength as years advanced. We are indebted to all

the members who have strived hard for this. Now

we have reached a stage where we are going to

have our own publication. The strength and integrity

of any association is often declared by its official

publication. I am extremely glad that our

publication “JCAESOK” has become a reality under

the able editorship of Dr. Ganesh. I hope our journal

will maintain high standards and wish the whole

editorial team a very successful tenure.

Dr. CV PradeepPresidentFederation of Operative Dentistry of India (FODI)


7

In this review article we are discussing about the variousclinical techniques to reduce the polymerization shrinkagewhich will be helpful to the practitioner.

Strategies to Reduce polymerization shrinkagein Clinical Procedures

Polymerization shrinkage

Materials Placement technique

1. Flowable composite as liner 1. Incremental2. Bilayered restorations 2. Horizontal

3. Three site4. Successive cusp build5. Vertical layering6. Oblique7. Centripetal build up

MaterialsPlacing Flowable composite: The use of a relatively thick

layer of a viscous bonding agent or a flowable compositehas been advocated to absorb volumetric changesassociated with polymerization. It is assumed that lowviscosity material can fill irregular margins of proximalboxes. Flowable composites are recommended as linersbeneath Class II composite restorations due to their lowviscosity, elasticity and wettability (31, 32). Additionally,these materials have a thermal expansion coefficient similarto tooth tissue. Flowable composites exhibit a substantiallylower modulus of elasticity that enables elastic deformationto absorb polymerization shrinkage stresses, reducing thetendency of open margins. This ability seems to be mostimportant when the gingival margin of a restoration is placedin absence of enamel, where a less stable cementum – dentinsubstrate for bonding is present (32, 33). In weak area,flowable composite permits a better seal, as minimal stressis created at the cervical margin. The use of a flowablecomposite at the gingival margin is claimed to reduce stressby 18 – 50% and limit microleakage (32, 34).

Bilayered: It plays an important role in restorativedentistry, where in Glass Ionomer Cement (GIC) is placed

Clinical Steps in Reducing Polymerization Shrinkage

* Deivanayagam Kandaswamy, ** Nagendrababu Venkateshbabu

Introduction Composite resins have been introduced into the field

of Conservative dentistry to minimize the drawbacks of theacrylic resins that replaced silicate cements (the onlyaesthetic materials previously available) in the 1940s.Besides acceptable aesthetics properties, resin compositescan be directly bonded to tooth structure without removinghealthy tissues (1). Because of its bondability, the compositematerial application has been increased in modernpreventive and Conservative Dentistry (1). As a result, resincomposites can be used for different purposes such as:anterior and posterior teeth injured or diseased by the cariesprocess, occlusion adjustments, cementation of indirectrestorations, bonding orthodontic brackets, and aestheticteeth transformations (1).

A clinician who used composites to restore posteriorteeth experienced poor wear resistance, difficulties inachieving good proximal contact and contour,polymerization shrinkage and poor dentin marginaladaptation(2-7). The improved performance of resin basedcomposites and the increasing demand for esthetics areencouraging more clinicians to select resin-basedcomposites for posterior restorations (8-10).Due to theadvancements in various newer composites and matrixsystems, wear resistance of composites had been improvedsignificantly (11,12) and good proximal contact and contourcan be achieved,(13-15) polymerization shrinkage remainsthe biggest challenge in composite restorations. (16-18)

Polymerization shrinkage:

The clinical success of composite resins is directlyrelated to the polymerization process. (19) Polymerizationshrinkage creates stresses as high as 13 MPa betweencomposite and tooth structure (20). These stresses severelystrain the interfacial bond between the composite and tooth.Resin composite may pull away from the least retentive cavitymargin resulting in gap formation. Stresses also createtensile forces in enamel margin which result in marginaldegradation from mastication, enamel cracking andfractures along the interface.

Factors affecting polymerization shrinkage· Modulus of resin elasticity· Polymerization rate· Cavity configuration· Filler content· Degree of conversion· Water sorption· Clinical technique

* Prof and Head,

** Senior Lecturer, Dept of Conservative Dentistry and Endodontics,

Faculty of Dental Sciences, SRU, Chennai, Tamilnadu.


8

Deivanayagam Kandaswamy

below and a resin composite is placed over it. The superiormicromechanical bond of resin composite to acid etchedenamel, the bond strength of GIC to dentin and the ability ofGIC to release fluoride when in contact with oral fluids,combined with its low solubility, make the combination ofthese two materials a prudent step in improving clinical

success (35, 36). This technique was developed by Mcleanand others in 1985. They used the dentin adhesive propertiesof GIC to seal cavities and reduce microleakage. Thistechnique benefits from the advantages of GIC fluoriderelease combined with esthetic resin material to enhanceclinical serviceability (37, 38).

No Technique Placement Advantages

Incremental(Fig 1)

(2, 21-23)

Placing composite layers less than2 mm in thickness

Good marginal qualityComplete polymerization

Reduces cuspal deflectionReduces cuspal strainComposite layers with high diffusion which

allows optimal light transmission with therestoration thus increasing aesthetics

1

Horizontal

(Fig 2)(2, 21, 23, 24)

Occlusogingival composite layering

is done

Used for small restoration2

Three site technique(Fig3)(2,21, 25, 26)

Uses clear matrix and reflectivewedges

It attempts to guide the polymerization vectorstowards the gingival margin

3

Succesive cusp build

up(Fig 4)(2, 21,27, 28)

First composite increment is

applied to a single dentin surfacewithout contacting the opposingpreparation walls.

After this restoration, built up isdone by placing wedge shapedcomposite increments

Reduces C factor in three dimensional tooth

preparation4

Vertical layering

(Fig 5)(21)

Place small increments in vertical

starting from one wall, buccal orlingual and carried to another wall

Initiate polymerization from be-

hind the wall, if buccal incrementis placed on the lingual wall, it iscured from outside the lingual wall.

Reduces gap at gingival wall which is formed

due to polymerization shrinkage5

Oblique

(Fig 6)(2,21,29)

Wedge shaped composite

increments are placed to preventdistortion of cavity walls.

Reduces C factor

Polymerization started first through thepreparation walls and then from the occlusalsurface to direct vectors of polymeritaion toward

the adhesive surface (indirect polymerizationtechnique)

6

Centripetal buidup

(Fig 7) (30)

First layer of composite (1mm) was

placed towards the matrix band

Subsequent increments (2mm)were applied horizontally towards

the occusal area of the cavity

Thin proximal layer placed towards the matrix

band is cured before adjacent compositeincrements are applied into the cavity. This canreduce the V (cavity volume)/ A (area of the cavity

wall) ratio.

First layer had no contact with the pulpoaxialwalls and thus had less tendency to contract

towards this wall, away from the cervical floorduring polymerization

7

Placement Technique


9

Newer bilayered technique (35): There are two alterna-tive techniques for laminate restorations in lieu of employ-ing the traditional total etch system. A clinician can thusemploy a glass ionomer adhesive systems after initial set ofGICs or the clinician can use a self etch primer over unsetGIC. Clinically the latter technique would be more useful, asit not only does away with the etch and rinse procedure, butalso saves valuable clinical time, as it can be employedimmediately after placement of GIC in the cavity.

References1. Schneider LF, Cavalcante LM, Silikas N. Shrinkage stresses generated during

Resin – composite applications: A review. Jou of Dental Biomechnanics.

2. Deliperi S, Bardwell DN. An alternative method to reduce polymerization shrink-age in direct posterior composite restorations. J Am Dent Assoc 2002;133;1387-1398

3. Wilson NH, Wilson MA, Wastell DG, Smith GA. A clinical trial of a visible lightcured posterior composite resin restorative material: fiveyear results. Quin-tessence Int 1988;19:675-81.

4. Letzel H. Survival rates and reasons for failure of posterior composite restora-tions in multicentre clinical trial. J Dent 1989;17(supplement 1):S26-8.

5. Lundin SA, Koch G. Class I and II composite resin restorations: 4-year clinicalfollow up. Swed Dent J 1989;13:217-27.

6. Raskin A, Michotte-Theall B, Vreven J, Wilson NH. Clinical evaluation of a pos-terior composite: 10 year report. J Dent 1999;27(1): 13-9.

7. Wilder AD Jr, May KN Jr, Bayne SC, Taylor DF, Leinfelder KF. Seventeen-yearclinical study of ultraviolet-cured posterior composite Class I and II restora-tions. J Esthet Dent 1999;11(3):135-42.

8. Jordan RE, Suzuki M. Posterior composite restorations: where and how they

work best. JADA 1991;122(12):30-7.

9. Simonsen RJ. Move over amalgam: at last. Quintessence Int 1995;26(3):157.

10. ADA Council on Scientific Affairs; ADA Council on Dental Benefit Programs.Statement on posterior resin-based composite. JADA 1998;129:1627-8.

11. Christensen GJ. Amalgam vs. composite resin: 1998. JADA 1998;129:1757-9.

12. Gerbo L, Leinfelder KF, Mueninghoff LA, Russell C. Use of optical standards fordetermining wear of posterior composite resins. J Esthet Dent 1990;2(5):148-52.

13. Bertolotti RL. Posterior composite technique utilizing directed polymerisationshrinkage and a novel matrix. Pract Periodontics Aesthet Dent 1991;3(4):53-8.

14. Keogh TP, Bertolotti RL. Creating tight, anatomically correct interproximal con-tacts. Dent Clin North Am 2001;45(1):83-102.

15. Liebenberg WH. Assuring restorative integrity in extensive posterior resin res-torations: pushing the envelope. Quintessence Int 2000;31(3):153-64.

16. Condon JR, Ferracane JL. Assessing the effect of composite formulation onpolymerization stress. JADA 2000;131:497-503.

17. Spreafico RC, Gagliani M. Composite resin restorations on posterior teeth. In:Roulet JF, Degrange M. Adhesion: The silent revolution in dentistry. Chicago:Quintessence; 2000:253-76.

18. Tay FR, Wei SH. Indirect posterior restorations using a new chairside microhybridresin composite system. J Adhes Dent 2001;3(1):89-99.

19. Thome T, Steagall W, Tachibana A, Braga SRM, Turbino Ml. Influence Of TheDistance Of The Curing Light Source And Composite Shade On Hardness OfTwo Composites.J Appl Oral Sci. 2007;15(6):486-91.

20. Cornelis J. Kleverlaan, Albert J. Feilzer.Polymerization shrinkage and contrac-tion stress of dental resin composites. Dental Materials (2005) 21, 1150–1157.

21. Nisha garg & Amit garg. Text book of operative dentistry, Jaypee Publishing, .

22. Davidson CL. Resisting the curing contraction with adhesive composite. J ProsthtDent 1986;55:446-7.

23. Lutz F, Krejci I, Barbakow F. Quality and durability of marginal adaptation inbonded composite restorations. Dent Mater 1991; 7(2): 107-13.

24. Tjan AH, Bergh BH, Lidner C. Effect of various incremental techniques on themarginal adaptation of class II composite resin restorations. J Prosthet Dent1992;67(1):62-6.

25. Lutz F, Krejci I, Luescher B, Oldenburg TR. Improved proximal margin adapta-tion of Class II composite resin restorations by use of light-reflecting wedges.Quintessence Int 1986;17:659-64.

26. Lutz F, Krejci I, Barbakow F. The importance of proximal curing in posteriorcomposite resin restorations. Quintessence Int 1992;23: 605-7.

27. Liebenberg WH. Successive cusp build-up: an improved placement techniquefor posterior direct resin restorations. J Can Dent Assoc 1996;62:501-7.

28. Klaff D. Blending incremental and stratified layering techniques to produce anesthetic posterior composite resin restoration with a predictable prognosis. JEsthet Restor Dent 2001;13(2):101-13.

29. Weaver WS, Blank LW, Pelleu GB. A visible-light-activated resin cured throughtooth structure. Gen Dent 1988;36:236-7.

30. Szep S, Frank H, Kenzel B, Gerhardt T, Heideman D. Comparative study ofcomposite resin placement: Cntripetal buildup versus incremental technique.Pract proced Aesthet dent 2001;13(3): 243 – 250.

31. Attar N, Tam LE, Mccomb D. Flow, strength, stiffness and radiopacity offlowable resin composites . Journal of the Canadian Dental Association2003;69(8),516 -521.

32. Fabianelli et al. Microleakage in class II restorations: open Vs closed centrip-etal build up technique. Operative dentistry 2010, 35(3), 308 – 313.

33. Carvalho RM, Pereria JC, yoshiyama M, Pashley DH. A review of polymeriza-tion contraction: The influence of stress development versus stress relief. OperDent 1996;21(1) 17-24.

34. Korkmaz Y, Ozel E, Attar N. Effect of flowable composite lining on Microleakageand internal voids in class II composite restorations. Jou of Adhes Dent2007;9(2), 189 -194.

35. Gopikrishna V, Abarajithan M, Kirthikadatta J, Kandaswamy D. Shear bondstrength evaluation of resin composite bonded to GIC using three differentadhesives. Oper Dent 2009, 34(4), 467 – 471.

36. Naughton WTand Latta MA. Bondstrength of composite to dentin using selfetching adhesive systems . quintessence International 2005; 36(4), 259 – 262.

37. Sneed WD, Looper SW. Shearbond strength of a composite resin to an etchedglass ionomer. Dent Mater 1985;1(4), 127-128.

38. Magnum FI, Berry EA 3rd, Parikh UK, Ladd D. Optimal etching time of glassionomer cement for maximum bond of composite resin. Journal of the AmerDental Assoc 1990;120(5), 535 – 538.

Clinical steps in reducing polymerization shrinkage


10

IntroductionFracture of endodontically treated teeth (ETT) is one of

the main causes of treatment failures in endodontics.Compared to healthy teeth, root filled teeth are often foundto be more susceptible to fracture. A fractured ETT presents asignificant clinical problem. For these reasons, a successfulroot canal treatment is never considered complete until thecrown is appropriately restored (1)

Root canal treatment results in a reduction in theresilience and fracture resistance of the tooth (2) due toextensive loss of tooth structure to caries, trauma, accesscavity preparation and root canal preparation (3)

Endodontic access preparation is a deep cavity resultingin the extensive reduction of dentin (4). In addition to this,loss of anatomic structures such as cusps, ridges and archedroof of the pulp chamber further weakens the tooth (5). Itwas also hypothesized that root canal treatment could resultin dehydration (6) reduction in dentinal elasticity andincrease in brittility (7). Stresses generated duringendodontic procedure may weaken the tooth resulting in thefracture of unprotected cusps under the forces of mastication(8). In addition, endodontic access preparations result in

increased cuspal deflection during function and increasedthe possibility of cuspal fracture especially in patients withlateral excursive contact (9). It has also been stated thatremoval of pulp from the teeth result in loss of the protectivefeedback mechanism that protects teeth from overloading(10).

The above observations indicate that restorations thatenhance structural integrity would be expected to increasethe fracture resistance of ETT. Complex amalgamrestorations, bonded restorations, inlays, onlays andcomplete cast restorations have been recommended for thispurpose (11). But these restorations can lead to fracture oftooth structure due to wedging effect causing flexure of cusp(12). An in vivo study assessing the influence of cavitypreparation on tooth fracture found that 94% of fracturesoccurred in prepared teeth when the width of the isthmuswas 1/3 or more of the intercuspal distance. Conversely,

Aims and objectives: To evaluate the effect of pre-impregnated glass fibers in reinforcing root filled teeth as a

short term interim post endodontic restoration.

Materials and Methods: 50 extracted human second mandibular molar teeth of comparable size were divided

randomly into 5 groups of 10 each. Group I: Intact natural teeth. Extensive MOD cavity was prepared in all the

samples except Group I. Access to root canals was gained from the floor of the cavity. Group II: Following root

canal treatment, teeth were restored with resin composite. Glass fiber was placed in a buccolingual groove

above the composite restoration; Group III: Following root canal treatment, glass fiber was placed on the floor

of the pulp chamber and resin composite restoration given on it.; Group IV: After RCT teeth were restored with

resin composite; Group V: After RCT, teeth were left unrestored (Positive Control: PC). The specimens were then

loaded to failure using a Universal Testing machine (UTM). The data was subjected to one way ANOVA and

Duncan's post hoc analysis

Results: Mean fracture strength values of the two control groups was Group I (1608.83) and Group V (570.17).

Significant difference was found between the control groups and the three study groups; Group II (1187.00),

Group III (1003.30), Group IV (795.60) (p value < 0.001)

Conclusion: Incorporation of glass fibers into resin composite restorations increased the fracture resistance of

endodontically treated teeth. Teeth were more resistant to fracture when the fibers were placed in a

buccolingual groove prepared on surface of the resin composite restoration.

Key words: Endodontically treated teeth (ETT), fracture resistance, fiber reinforced composite (FRC), pre-im-

pregnated glass fiber

Abstract

Evaluation of the effect of vectris fibers in reinforcingpost endodontic restorations- An Invitro Study

* Jothish Ravi, ** Pranau Vanajassan, *** C V Subba Rao

* Senior Lecturer, Dep of Conservative Dentistry &Endodontics, SreeMookambika Institute of Dental Sciences,Kulasekharam, Kanyakumari Dst, Tamilnadu-629161,

** Senior Lecturer,*** Professor, Dept. of Conservative Dentistry & Endodontics,

Saveetha Dental College & Hospital, Chennai 77


11

Evaluation of the effect of vectris fibers in reinforcing post endodontic restorations

intact teeth and conservative preparations produced fewerfractures (13).

Intracoronal posts were thought to be useful inreinforcing the root filled teeth (14). But it is now known thatposts aids in retention of core materials and does notreinforce ETT (15). Infact early studies show that cementedmetal posts do not strengthen the root (16) (17). Recently,fiber-reinforced composite (FRC) root canal posts that couldbe bonded to the canal walls have been introduced as thealternative. The biomechanical properties of FRC posts havebeen reported to be close to those of dentin (18), so whenbonded in place with resin cement, it was thought that forceswould be distributed more evenly in the root, resulting infewer root fractures. An inherent problem of theseprefabricated FRC posts is that the polymer matrix betweenthe fibers is highly cross-linked and due to the high degree ofconversion; non-reactive, which makes it very difficult tobond the prefabricated FRC posts to composite resin cementand tooth structure (19). So the bonded posts are believed tostrengthen the root initially (20) (21)but this strengtheningeffect is probably lost over time as the tooth is exposed tofunctional stresses and the resin bond to dentin weakens(22).More over a restoration lacking resistance form is not likelyto be a long term success, regardless of the retentivenessand adhesiveness of the post (23). The most frequent modeof failure with posts has been found to be loss of retention ofthe post, while root fracture is the most serious type offailure(18). Teeth restored with less rigid posts such as fiberposts tend to have failures that are more likely to berestorable(24) (25), though this may depend on the ferrulepreparation (26), type of luting material used for cementationof posts (27) and core material used (28). On the contrary,

other studies have shown that FRC posts created less fractureresistance than cast post and cores (29), this could beattributed to the displacement or fracture of the resin cementlayer, composite core or resin post during mechanicaltesting(30).

With more recent advancements in adhesive technology,it could be possible to create conservative, highly estheticrestorations that reinforce the root filled tooth. It has beenreported that root filled premolar teeth restored with dentinbonding system (DBS) showed increased fractureresistance(31). However polymerization shrinkage remainsa problem(32). Several methods are used to reducepolymerization shrinkage and subsequent stresses andreinforce the tooth such as use of improved DBS (33),intermediate layer of low viscosity and low modulus flowablecomposite (34) and insertion of glass fibers (35).

The development of glass fiber has resulted in the use ofcomposite resin in extensive preparations. Resin compositeswhen reinforced with fibers show an increase in flexuralmodulus and fracture resistance (35) and thus would servewell as an interim restoration. This presents the backdropand objective for the present study. This study attempts toevaluate the role of glass fibers in reinforcing postendodontic restoration and critically analyzes two differentfiber insertion techniques used to increase the fractureresistance.

Materials and methods

Intact, non carious human mandibular second molarteeth (n=50) of comparable size, extracted for periodontalreasons were taken up for this study. Attritted teeth were notincluded in this study. Teeth were cleaned and disinfected in

Fig. 1 Fig. 2 Fig. 3 Fig. 4

Fig. 5 Fig. 6 Fig. 7 Fig. 8


12

Jothish Ravi

0.5% chloramines solution for 48 hours and then stored innormal saline. Teeth were randomly distributed into 5 groupsof 10 teeth each.

Group I: 10 intact teeth with out any cavity preparationor root canal treatment; negative control (NC)

Group II: Extensive MOD cavity preparation was donewith gingival cavosurface located 1mm above cemento-enamel junction. The bucco-lingual width of each cavity wassuch that the thickness of buccal wall was 2-2.5mm andlingual wall 1.5mm (Fig 1). Isthmus of width 1/3 inter-cuspaldistance was prepared and this width was maintained tillthe floor of the pulp chamber. Cavities were prepared withrounded internal angles, with a divergence between the wallsof 6 to 150 and with margins with 900 cavosurface angles.The depth of the cavity was 4mm without proximal steps andflat floor. Consistency in cavity preparation was ensured byparallel preparation of the facial and lingual walls of thecavity. Depth of the cavity was measured with periodontalprobe. Width of the cavity and thickness of wall wasmeasured using vernier caliper.

Access cavities were prepared from MOD cavity pulpalfloor using high speed bur (one for each group) and waterspray (NSK, High Speed handpiece, PANA AIR, 400000 rpm) inall the remaining 40 teeth. Canals were instrumented with Kfiles to an apical size 25 using stepback technique. Irrigationwith 1 mL of 5.25% NaOCl preceded each file introduced intothe canal. Following cleaning and shaping, canals were driedand obturated with gutta percha (GP) and an epoxy resinsealer (AH plus, DENTSPLY Maillefer) sealer using cold lateralcompaction. Excess root canal filling material was removedwith a hot excavator at the canal orifice.

After the endodontic procedures, access cavities werecleaned and dried. Cavities were etched with 37% phosphoricacid gel (Total Etch, Ivoclar Vivadent) for 15 sec, rinsed anddried gently before the application of Dentin Bonding agent(Prime& Bond NT, Dentsply) and cured for 20 sec using aQTH light curing unit (Astralis 7,Ivoclar) with wavelength

ranging from 500 - 750 mW/cm-2. The cavities were thenrestored with resin composite (Surefil, Dentsply) using anincremental technique and cured from the occlusal surfacefor 40 sec. After the restoration, grooves of 3 mm width and1mm depth were prepared on the occlusal surface of therestoration between the cusp tips in the buccolingualdirection with high speed bur under water cooling. Thegrooves ended at the occlusal one third of the buccal andlingual walls of the teeth (Fig 2). The grooves were rinsedand dried. Dentin Bonding agent was applied and cured for20 sec. Pre-impregnated translucent glass fiber mesh (Vectris,Ivoclar) (Fig 3) of 3mm width was cut from the mesh andplaced all along the length of the groove over uncuredflowable composite resin (Flowline, Ivoclar), already appliedall along the grooves and polymerized for 40 sec from theocclusal surface.

Group III: After the endodontic procedures, accesscavities were cleaned and dried (as described for Group II).Vectris glass fibers of 3 mm width were adapted over theuncured flowable composite applied on to the buccal wall-floor and lingual wall of the cavities; extending till the cusptips (Fig 4). These glass fibers were sandwiched between theflowable composite and cured for 20 sec. The cavities werethen restored with a resin composite (Surefil) using anincremental technique and cured for 40 sec from the occlusalsurface.

Group IV: After endodontic procedures, the cavities werecleaned, etched, bonded in the same way as it was mentionedfor the other two groups and filled with composite resin(Surefil) using an incremental technique. (Fig 5)

Group V: After the endodontic procedure, the cavitieswere left unrestored; positive control (PC) (Fig 6)

All the procedures were done by the same operator.All the specimens were embedded in acrylic resin till the

cementoenamel junction. The composite restorations werefinished with a scalpel, fine diamond burs, and then polishedwith paper disks (Sof-Lex, 3M ESPE, St Paul, MN, USA). After

Oneway ANOVA

Table 1


13

finishing and polishing, the experimental teeth were placedat 37°C in a water bath for 24 hours. Specimens were mountedin Instron Universal Testing Machine (Lloyds, Fareham, UKwith Nexygen-MT software) for compressive loading of teeth.A 5 mm round metal ball was positioned on the teeth in sucha way that it made contact with the occlusal surface of therestoration and buccal and lingual cusps of the teeth. (Fig 7,8). Vertical compressive force was applied by the upper stageof the Universal Testing Machine, moving at a crossheadspeed of 0.5mm/min. The force necessary to fracture eachtooth was recorded in Newtons (N).

After failure, the specimens were visually inspected forevaluating the fracture lines. The fractures observed wereclassified as restorable or unrestorable. A tooth wasconsidered unrestorable when the fracture line occurredthroughout the vertical extension of the pulp chamber floor,dividing the crown into two pieces. A tooth was consideredrestorable when the fracture line was partial, either verticalor horizontally, without dividing the crown into parts.

Statistical AnalysisData was expressed as mean and standard deviation

and statistically analyzed by One Way ANOVA(Table 1) andpost hoc Duncan’s Multiple Range test (Table 2) to identifythe significant groups at a significant level of p=0.05

Results

Duncan’s Post Hoc Analysis clearly shows that there issignificant difference between the different groups. Group Ishows the highest mean fracture strength (1608.83 +/_109.77) and Group V shows the lowest (570.17 +/- 34.00).Group IV (795.60 +/- 56.19) exhibited higher fractureresistance than Group V, suggesting that adhesive bondedrestorations increase the fracture resistance of ETT. Group II(1187.00 +/- 106.09) and Group III (1003.30 +/- 45.80) showstatistically significant improvement over Group IVemphasizing the fact that incorporation of glass fiber furtherincreases the fracture strength of ETT. When Group II and IIIare compared, Group II show higher fracture strength,indicating the fact that the technique of placing the glassfibers in a groove on the surface of resin compositeperformed better than the technique of placing the fibers at

the floor of the pulp chamber as followed in Group III. Pvalue (< 0.001) indicates that the difference between thegroups is statistically significant.

Data of each group after Oneway ANOVA analysis showvery high standard deviation. The presence of too manyvariables like variation in morphology, angulations of cuspalinclines, thickness of enamel, inherent weaknesses, variationin size and variation in the levels of contact of metal ballwith cuspal inclines during loading could be the reasonbehind the high standard deviation shown in the analysis. Ifstandardized tooth models were used, the standard deviationwould have been reduced.

Graphical representation is given in the bar diagram(Diagram 1).

DiscussionThe success of endodontic treatment ultimately depends

on appropriate and timely coronal restoration of ETT. Postendodontic restoration reinforces the tooth and provideseffective seal. But often patients discontinue treatment afterthe root canal treatment. A solution to this problem, to avertundesired fracture of ETT, is to provide a comparativelyconservative interim resin composite restorationimmediately after root canal treatment.

Resin composites provide a potential interim techniqueof restoring ETT based on their ability to bond to toothstructure. One important drawback of composites ispolymerization shrinkage and consequently, significantstresses are generated within the tooth itself and at the tooth–restoration interface. While composites flow and relieve thestresses within the tooth structure during the pregel phase,this flow ceases after gelation and cannot compensate forthe stresses created at the tooth–restoration interface.Cuspal deflection is the result of interaction between thepolymerization shrinkage stress of composite and thecompliance of the cavity wall. This may compromise thebond at the tooth–restoration interface, possibly leading tobacterial microleakage and recurrent caries. Cuspaldeflection has been reported between 4 and 45 µm dependingon the measurement method, cavity size and extent of resin

Duncan’s Post Hoc Analysis

Mean fracture strength (Newton) of different groups

Group Mean* + SD F value p value

Group I 1608.83a 109.77 175.825 < 0.001

Group II 1187.00b 106.09

Group III 1003.30c 45.80

Group IV 795.60d 56.19

Group V 570.17e 34.00

* a, b, c, d, e – Means with same superscript do not differ each other(Duncan’s Multiple Range Test)


Table 2


14

composite shrinkage (36).Cuspal deflection increases with increasing cavity

dimension. Higher stresses are generated in largerrestorations. At the same time stress is lower within therestoration than at the tooth–restoration interface. Thisstress distribution incurs the risk of tooth fracture (37).Adhesive restorations are preferred in such cases since thestress is better distributed through the bonding interface(38).

Bonded adhesive restoration increased the fractureresistance as evident from the mean fracture strength ofGroup IV. This is in agreement with a previous study thatsuggested that posterior resin composite has great potentialas a cusp reinforcing material (39). Belli et al (2006) hadsuggested that the use of leno weave ultra high molecularweight (LWUHMW) polyethylene fibers to increase thefracture resistance of ETT (40). On similar lines, this studyhas used pre-impregnated glass fiber (Vectris, Ivoclar) toreinforce the ETT. The results are very encouraging as evidentfrom the statistical analysis.

Pre-impregnated Glass fibers had been used in the pastfor the fabrication of prosthesis and periodontal splinting.Glass Fibers are structural materials with atleast two distinctconstituents. The reinforcing component provides strengthand stiffness while the surrounding matrix supports thereinforcement and provides workability. The fibers may bearranged in various configurations: unidirectional fibers of7-10µm in diameter, biaxial or triaxial braided fibers, lenowoven fibers or mesh. Unidirectional fibers providesignificant strength and stiffness in the fiber direction, but ithas poor transverse properties, resulting in premature failure(41). Thus the reinforcing efficiency of unidirectional fiberscould be obtained only in one direction. Continuousbidirectional fibers (woven, mesh type) have reinforcingfibers in two directions, thus reinforcing the polymer equallyin two directions, thus recommended in cases where thedirection of load is unknown. The use of woven fibers givesthe so called orthotropic properties in a plane (42). So meshtype fibers were selected for this study. This mesh could beeasily cut and embedded into dental composite with out anymajor structural alteration; the fiber yarns maintain theirorientation and do not separate from each other when closelyadapted to the contours of the teeth. Thus the favorable elasticmodulus and interwoven nature of the fabric, distributes theload over a wider area, thus decreasing the stress levels(43). The fibers have an inherent crack-stopping property.This was theorized on the concept that the presence of glassfiber network would create a change in the stress dynamicsat the restoration-adhesive resin interface. In addition theglass fibers replace part of the composite increment,resulting in a decrease in the overall volumetricpolymerization shrinkage of the composite. These fibersfurther assist in bonding the initial increment of thecomposite and thereby prevent pulling away of the compositefrom the margins. Thus they have a strengthening effect onthe composite margins. The fibers also increase theresistance to dimensional changes or deformation (44).

The glass fibers material with the polymer matrix usedin this study consisted of both linear and cross-linkedpolymer phases. The linear phase in this material, which isPolymethylmethacrylate (PMMA), can be dissolved if asuitable adhesive resin is added on the surface of the fibers.The suitable adhesive resin should contain monomers,having dissolving parameters equal or close to that of PMMA.BisGMA based adhesive resins have been shown to be capableof dissolving PMMA (18). So in this study flowable compositeresin (FCR) was used in conjunction with glass fibers.Additionally it is known to have a stress modifying effect(45). Flowable resin could easily flow and infuse into themesh thus improving the wetting of resin fibers andmanageability (46). This additional step would reinforce thecomposite resin and connect the pulp floor to the resin andfiber (47).

Incorporation of pre-impregnated glass fiber intocomposite restoration produced similar effect likepolyethylene fibers as shown in previous studies by Belli etal (35) (40). Both techniques of fiber insertion as attemptedin group II and group III increased the fracture resistance ofETT than adhesive restoration alone, ie group IV. Whencompared to each other, pre-impregnated glass fibers asplaced in the groove placed on the resin composite (GroupII) held the cusps together and thus increased fractureresistance than the fibers placed in the floor of the cavity(Group III). Due to their high modulus of elasticity, there isless elastic deformation during load application, and thecompression tension is transferred to the material locatedbelow the fiber, in this case, the flowable composite, resincomposite and its adhesive resin system (48). The fractureresistance increases when fibers are placed close to thepoint where force is exerted because it leads to a shorterworking arm according to levers principle (49). This wasalso in agreement with two studies done by Belli et al usingpolyethylene fibers (35) (40).

Majority of the specimens of the study groups showedrestorable fracture. The fractures observed were horizontalor vertical, partial fractures of the crown. On the basis ofthis finding, fiber reinforced adhesive resin compositerestorations should not be considered a substitute for fullcoverage restoration in posterior teeth, but rather as aninterim short to medium term restoration.

At this point, it is to be reminded that the method ofgradually increasing the load applied to the teeth till itfractures is not typical of loading that occurs clinically.Stresses applied to teeth and dental restoration is generallylow and repetitive rather than being isolated or of impacttype. UTMs employ static loading where as the forces thatwe come across inside oral cavity are more complex anddynamic. Such dynamic forces cause severe effects onrestored teeth and limit the service time of dentalrestorations. Moreover ageing, alternate thermal,mechanical stress and wear should also be taken intoconsideration (50). This would mean that a fatigue resistancetest could be more accurate than fracture resistance test asdone in this study. A 5mm metal sphere was used for

Jothish Ravi


15

transferring the load to the teeth because a previous studyhas shown that it contacts the functional and non functionalcusps in positions close to those found clinically (37).

Another matter of concern is the effect of rigid embeddingmaterial like acrylic on the fracture resistance of ETT (51). Amethod of root embedment that simulate periodontalligament could rectify this situation. These facts would beseriously considered while carrying out further studies.

ConclusionWithin the limitations of this study it is appropriate to

conclude that incorporation of pre-impregnated glass fibersinto bonded adhesive restoration increased the fractureresistance of root filled teeth. Proper placement of theseglass fibers could increase the advantage of using extensivecomposite restorations. This should encourage theclinicians to consider this technique as an interim postendodontic restoration.

References1. Smith CT, Schuman N. Restoration of endodontically treated teeth: A guide for

the restorative dentist, Quintessence Int 1997; 28(7): 457-58.

2. Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result ofendodontic and restorative procedures, J Endodon 1989; 15(11): 512-16.

3. Papa J, Cain C, Messer HH. Moisture content of vital Vs endodontically treatedteeth, Endod Dent Traumatol 1994; 10(2): 91-93.

4. Owen CP. Factors influencing the retention and resistance of preparations forcast intracoronal restorations, J Prosthet Dent 1986; 55(6): 674-77.

5. Mondelli J, Steagall L, Ishikiriama A. Fracture strength of human teeth withcavity preparations, J Prosthet Dent 1980; 43: 418-22.

6. Rosen H. Operative procedures on mutilated endodontically treated teeth, JProsthet Dent 1961 11; 972-86.

7. AssifD, Nissan J, Gafni Y, Gordon M. Assessment of the resistance to fractureof endodontically treated treated molars restored with amalgam, J Prosthetdent 2003; 89: 462-65.

8. Wagnild GW, Mueller KI. Restoration of endodontically treated tooth. In CohenS, Burns RC (eds) Pathways of the pulp 8 th ed Mosby Inc, St Louis, MO, USA765-795.

9. Gutmann JL. The dentin-root complex: Anatomic and biologic considerations inrestoring endodontically treated teeth, J Prosthet Dent 1992; 67(4): 458-67.

10. Randow K, Glantz PO. On cantilever loading of vital and non-vital teeth. Anexperimental clinical study, Acta Odontol Scand 1986; 44(5): 271-77.

11. Smales RJ, Hawthorne WS. Long term survival of extensive amalgam andposterior crowns, J Dent 1997; 25(3-4): 225-27.

12. Nessrin A. Taha, Joseph E.A. Palamara, Harold H. Messer, Cuspal deflection,strain and microleakage of endodontically treated premolar teeth restoredwith direct resin composites, J dent 37(2009)724 – 730.

13. Eackle WS, Maxwell EH, Braly BV. Fractures of posterior teeth in adults. J AmDent Assoc 1986;112:215-218.

14. S Deliperi. Direct fiber reinforced composite restoration in an endodonticallytreated molar: A 3 year case report, Oper Dent 2008; 33-2: 209-14.

15. Karbhari VM, Wang Q. Influence of triaxial braid denier on ribbon based fiberreinforced dental composites, Dent Mater 2006; 23(8): 969-76.

16. Guzy G E, Nichols J I. In vitro comparison of intact endodontically treated teethwith and without endo-post reinforcement. J Prosthet Dent 1979;42: 39-44.

17. Trope M, Maltz D O, Tronstad L. Resistance to fracture of restored endodonticallytreated teeth. Endod Dent Traumatol 1985; 1:108-11.

18. Lippo V.J. Lassila, Johanna Tanner, Anna-Maria Le Bell, Katja Narva, Pekka KVallittu Flexural properties of fiber reinforced root canal posts, Dental Materials(2004) 20, 29–36.

19. Anna-Maria Le Bell, Lippo V.J. Lassila, Ilkka Kangasniemi, Pekka K. Vallittu.Bonding of fibre-reinforced composite post to root canal dentin, Journal ofDentistry (2005) 33, 533–539

20. Mannocci F, Ferrari M, Watson T F. Intermittent loading of teeth restored usingquartz fiber, carbon-quartz fiber and zirconium dioxide ceramic root canal posts.J Adhes dent 1991;1:153-8.

21. Saupe W A, Gluskin A H, Radke R A Jr. A comparative study of fracture resistancebetween morphologic dowel and cores and a resin reinforced do wel system inthe intraradicular restoration of structurally compromised roots. QuintessenceInt 1996;27:483-91

22. Heydecke, Butz F, Strub J R. Fracture strength and survival rate of endodonticallytreated maxillary incisors with approximal cavities after restoration withdifferent post and core systems: an in vitro study. J dent 2001; 29:427-33.,

23. Lambjerg-Hansen H, Asmussen E, Mechanical properties of endodontic posts.J Oral Rehab 1997;24:882-7.

24. Newman M P, Yaman P, Dennison J, Rafter M, Billy E. Fracture resistanceofendodontically treated teeth resyored with composite posts. J Prosthet Dent2003;35:89:360-7.

25. Akkayan B, Gulmez T. Resistance to fracture of endodontically treated teethrestored with different posts system. J Prosthet Dent 2002;87:431-7.

26. Stankiewicz N R, Wilson P R. The ferrule effect: a literature review. Int EndodJ 2002;35:575-81.

27. Pilo R, Cardash HS, Levin E, Assif D. Effect of core stiffness on the in vitro fractureof crowned, endodontically treated teeth. J Prosthet Dent 2002;88:302-6.

28. Katebzadeh N, Dalton B C, Trope M. Strengthening immature teeth during andafter Apexification. J Endod 1998;24:256-9.

29. Tjan AH, Whang SB. Resistance to root fracture of dowel channels with variousthickness of buccal dentin walls. J Prosthet Dent 1985;53:496-500.

30. Maccari PC, Cosme DC, Oshima HM, Burnett LH, Shinkai RS. Fracture strengthof endodontically treated teeth with flared root canals and restored with differentpost systems. J Esthet Res Dent 2007;19:30-6.

31. Rudo DN, Karbhari VM. Physical behaviors of the fiber reinforcements as appliedto tooth stabilization, DCNA 1999; 43(1): 7-35.

32. Sufyan K, Garoushi, Lippo VJ, Lassila, Pekka K Vallittu. Fiber reinforcedcomposite substructure: Load bearing capacity of an onlay restoration, ActaOdontol Scand 2006; 64: 281-85.

33. Cobankara FK, Unlu N, Cetin AR, Ozkan HB. The effect of different restorationtechniques on the fracture resistance of endodontically treated molars, OperDent 2008; 33-5: 526-33.

34. Kemp-Scholte CM, Davidson CL. Marginal integrity related to bond strengthand strain capacity of composite resin restorative systems, J Prosthet Dent1990; 64: 658-64.

35. Belli S, Erdemir A, Ozcopur M, Eskitascioglu. The effect of fiber insertion onfracture resistance of root filled molar teeth with MOD preparations restoredwith composite, Int Endod J 2005; 38(2)73-80.

36. Gonzalez-Lopez S, Lucena-Martin C, de Haro-Gasquet F, Vilchez-Diaz MA, deHaro-Munoz C. Influence of different composite restoration techniques oncuspal deflection: an in vitro study. Operative Dentistry 2004;29:656–60.

37. Visvanathan A, Ilie N, Hickel R, Kunzelmann KH. The influence of curing timesand light curing methods on the polymerization shrinkage stress of a shrinkage-optimized composite with hybrid-type prepolymer fillers. Dental Materials2007;23:777–84.

38. Hurmuzhlii F, Kiremitci A, Serper A. Fracture resistance of endodontically treatedpremolars restored with ormocer and packable composite. J Endod2003;29:838-40.

39. Jagadish S, Yogesh BG. Fracture resistance of teeth with class II silver amalgam,posterior composite and glass cermet restorations, Oper Dent 1990; 15: 42-7.

40. Belli S, Erdemir A, Yildrim C. Reinforcement effect of polyethylene fiber in rootfilled teeth: comparison of two restoration techniques, Int Endod J 2006; 39:136-42.

41. Freilich, Martin A, Meier, Jonathan C.Fiber Reinforced Composites in ClinicalDentistry; Quintessence Publishing.

42. Vallitu PK. Flexural properties of acrylic resin polymers reinforced withunidirectional and woven glass fibers. J Prosthet Dent 1999;81:318-26.

43. S Deliperi. Direct fiber reinforced composite restoration in an endodonticallytreated molar: A 3 year case report, Oper Dent 2008; 33-2: 209-14.

44. O El Mowafy, W El Badrawy, A Eltanty, K Abbasi, N Habib. Gingival microleakageof class II resin composite restorations with fiber inserts, Operative Dentistry,2007, 32(3); 298-305.

45. Karbhari VM, Wang Q. Influence of triaxial braid denier on ribbon based fiberreinforced dental composites, Dent Mater 2006; 23(8): 969-76.

46. Rudo DN, Karbhari VM. Physical behaviors of the fiber reinforcements as appliedto tooth stabilization, DCNA 1999; 43(1): 7-35.

47. Labella R, Lambrechts P, Van Meerbeek B, Vanherle G. Polymerization shrinkageand elasticity of flowable composites and filled adhesives. Dent Materials1999;15:128-37.

48. Hirata R. Three point flexural strength and elastic modulus of resin compositesassociated with polyethylene or glass fibers.(MS Masters-Thesis).Porto Alegre,Brazil:Pontifical catholic University of Rio Grande do Sul

49. ParnianAlizadeh, Amir Ahmad Ajami, Elmira Jafari Navimipour, Siavash Savadi,Jafar Sadjadi. The effect of three composite fiber insertion techniques onfracture resistance of root filed teeth. J Endod 2009;35:413-16.

50. Sufyan K, Garoushi, Lippo VJ, Lassila, Pekka K Vallittu. Fiber reinforcedcomposite substructure: Load bearing capacity of an onlay restoration, ActaOdontol Scand 2006; 64: 281-85.

51. Cobankara FK, Unlu N, Cetin AR, Ozkan HB. The effect of different restorationtechniques on the fracture resistance of endodontically treated molars, OperDent 2008; 33-5: 526-33.



16

IntroductionComposite resins have become the material of choice for

direct restorations as they are able to restore proper toothform, function, and aesthetics. These are polymers havingan inorganic phase consisting of materials like quartz,borosilicate glass, lithium aluminum silicate, bariumaluminum silicate, colloidal silica, strontium zinc glass(1).dispersed in a matrix composed of monomers like BisphenolA glycidyl dimethacrylate (BisGMA) (2,2-bis [4-(2- hydroxyl -3 methacryloxypropoxy) phenyl], UDMA (Urethanedimethacrylate), TEGDMA (triethylene glycoldimethacrylate), as well as minute quantities of opticalmodifiers, activator initiator system and opacifiers(1).

The amount of monomer that got converted to polymerduring polymerization is called degree of conversion(2).Though, complete conversion of monomers is desired, it israrely achieved. Various previous studies have reported thedegree of conversion between 43 to 73% (3,4,5). It is foundthat various properties like wear, hardness, creep, tensilestrength, compressive strength and flexural modulus,discoloration and degradation reaction are affected bydegree of conversion(6,7). Thus a high degree of conversion

Aim and objective: To evaluate monomer release (BisGMA and TEGDMA) from three commonly usedcommercial composite resins

Materials and Methods: Standardized samples of Restorative Z100, Tetric Ceram, SpectrumTPH wereprepared. They were rapidly immersed in 100% ethanol for four minutes and the solvent was evaluated foreluted monomers. A reverse phase High Performance Liquid Chromatography was used to evaluate the solventfor released monomer. The chromatograph obtained were compared to standard chromatograph of BisGMAand TEGDMA.

Results: BisGMA release from Z100 was 1.58%, Tetric Ceram 0.88% and SpectrumTPH had a release of1.61%. TEGDMA release was 1.17%, 0.27%, 0.64% respectively. They showed a significant difference in releaseof monomers.

Conclusion: According to this study, the release of monomer was evident from the composite specimens.The evidence of release of these monomers has to be considered seriously in the light of cytotoxic andcarcinogenic potential of Bisphenol A. Further studies have to be performed to make guidelines for the saferuse of composite resin restoration.

Abstract

A comparative evaluation of residual monomer release from threedifferent composite resins using high performance liquidchromatography

* Sujathan U-Nu., ** Deivanayagam Kandaswamy

is desired.The degree of conversion is influenced by two sets of

factors, those related to the material and those related toclinical handling. The material related factors arecomposition of monomers, viscosity of monomers,concentration of activator and inhibitor present, diffusionlimitation of reactive media present and size, shade, opacityof filler particles(8). The light intensity of the polymerizationunit, duration of light irradiation, temperature producedduring polymerization and thickness of restorative materialcan be controlled by the clinician(8).

Brutscher(9) explained that the remaining unpolymerizedmonomers in a composite restoration are in various stagesof polymerization with reactive free radicals, pendent doublebonds and some amount of free unreacted monomers. Tairaet al(10). found out that upto 6% of the monomer in a BisGMA– TEGDMA based resin are left unreacted.

It has been established that free residual monomers canleach into various aqueous and non aqueoussolutions.(8,11,12,13) The cytotoxic effects of thesemonomers even in low concentration as well as a possibleestrogen like effect at high concentrations have beenreported. (14,15,16,17) This has become a major cause ofconcern, necessitating a quantification of the release ofresidual monomers from composite resins. Hence, this studywas undertaken to evaluate the residual monomers releasedfrom three different commercial composite resins, as wellas to quantitate the amount of principle monomers released.

* Reader, Department of Conservative Dentistry and

Endodontics, PMS College of Dental Science and Research,

Vattappara, Thiruvananthapuram, Kerala - 695 584;

* Prof and Head, Dept of Conservative Dentistry and

Endodontics, Faculty of Dental Sciences, SRU, Chennai,

Tamilnadu.


17

Materials and methodsThree commonly used composite restorative materials

were selected for the study on the basis of composition oftheir monomers. They were Restorative Z 100, Tetric Ceram,Spectrum TPH. Composition of these materials is given inTable – 1.

A Reverse phase High Performance LiquidChromatography (HPLC) was used to detect the release ofmonomers. A standard stock solution of pure monomers BisGMA (Syanolite resin, Batch No. 47948, DSM resins, UnitedKingdom) TEGDMA (Aldrich chemical Co. Cat No. 05201 MP,USA) were prepared for standardizing the identification andquantification of the extracted residual monomers. 100 mgof this BisGMA was weighed and transported into a glasstest tube. 400 ml of 100% ethanol (Hongto IndustriesCorporation, Lot No. 980600) was pipetted into the glass testtube to dissolve the monomer. Once BisGMA was completely

dissolved, 0.1 ml of this solution was pipetted into a 10 mlglass test tube and the solution was made up to 10 ml using100% ethanol. The test tube was covered immediately toprevent any loss of material by evaporation. Similar methodwas followed for TEGDMA also. 20 µl from the solution wasinjected into the HPLC system and the standardchromatograms were obtained for both the monomersindividually.

The size and weight of the samples were standardizedusing a unique plastic transparent mould (Figure - 1). Thecomposite material was dispensed on to a pre weighed glassslide and 200 mg of material was obtained using anelectronic balance. The material was loaded onto the mouldwith the dimensions as given in figure -1. The material waspacked using a Teflon coated cement carrier. The top surfaceof the mould was covered using a polyester film (Unident,Batch No. 1248) to avoid any open contact of the materialwith air during polymerization. The material was polymerizedby a halogen photo polymerizing unit using blue spectrumof visible light (Astralis – 3, Serial No. 011829, Vivadent).Each half of the mould was polymerized separately for 40seconds according to the manufacturer’s instructions. Thecured samples were removed from the mould and weighedonce again by using the same electronic balance to makesure there is no discrepancy in the sample weight.

Using 1 ml glass pipette 400µl of 100% ethanol waspipetted into 5 ml glass test tube. The freshly prepared testsamples were transferred using a tweezers and werecompletely immersed in this solvent. The mouth of the testtube was covered immediately to prevent the evaporation ofthe solvent. The samples were immersed for a period of 4minutes. At the end of 4 minutes the sample was removed.20µl from the remaining solvent was injected into the HPLCsystem and the chromatogram was obtained.

The samples were grouped according to the material usedas follows

Group I - Restorative Z100Group II - Tetric CeramGroup III - Spectrum TPHSeventeen samples were prepared in each group and were

analyzed. Results were tabulated under each group and werestatically analyzed.

Material Composition Manufacturer

Restorative Z100 Monomers: BisGMA, TEGDMA - 17%(wt), 34%(vol) 3M dental CompanyFillers: Zirconia, Silica- 82.5%(wt), 66%(vol) Lot no: 20000712

Others: Plastisizer, Photoinitiater, Stabilizers, Pigments - 0.5% by wt

Tetric Ceram Monomers: BisGMA, TEGDMA, UEDMA - 20.2%(wt), 40%(vol)Fillers: Barium glass, Yetterbium triflouride Ba-Al- fourosilicate glass, Dispersed Vivadent

Silicondioxide Spheroid mixed oxide - 79%(wt), 60%(vol) Lot No: 99050000987Others: Catalysts, stabilizers, Pigments Photoinitiators - 0.8% by wt.

SpectrumTPH Monomers: BisGMA, TEGDMA, BisEMA - 22.5%(wt), 43%(vol)Barium Alumino borosilicate, Highly dispersed Dentsply Detray

Silicon dioxide - 77%(wt), 57%(vol). Lot No: C24714Photo initiators, Stabilizers, Pigments- 0.5% (wt)

Table – 1: Composition of materials as given by the respective manufacturer.

Fig. 1

A comparative evaluation of residual monomer release from three different composite resins

using high performance liquid chromatography


18

ResultsThe amount of monomer release was calculated from

the area under the sample’s peaks, area under the standard’speak, and weights of standard and the sample using thefollowing formula.

Concentration of released monomer (wt)Area of the sample Weight of the Standard

= ————————— x —————————— x Dilution

Area of the Standard Weight of the Sample

Concentration by weight

By percentage/sample = ——————————— x 100

Original net monomer content

The values obtained were tabulated as the amount andpercentage of BisGMA released per group, TEGDMA per group,combined monomer released per group (Tables 2,3&4 andGraphs 1,2&3).

The values were statistically analyzed using anindependent T test. The comparison was made betweenindividual groups for BisGMA, TEGDMA and their combinedrelease separately. The ‘p’ value d” 0.05 was consideredstatistically significant difference.

The mean BisGMA release of Group I was 538.3µgms(1.58%) and of group III was 725.4 µgms (1.61%), which weresignificantly higher than that of group II value 352.2µgms(0.88%). TEGDMA release values were, Group I – 398.8µgms(1.17%), Group III – 289.8µgms (0.64), Group II 109.7µgms(0.27%). Group I value was significantly greater than that ofGroup III. Although Group II value was greater than GroupIII, it was not statistically significant. Combined release ofBisGMA and TEGDMA for individual groups were Group I -937.1 µgms (2.76%), Group III – 1015 µgms (2.26%) whichwere greater than Group III value of 461.4 µgms (1.15%)

This study showed a reduced over all percentage releaseof monomers (BisGMA and TEGDMA) from Group II whereasGroup I material showed a maximum percentage release.

Discussion

Resin composite materials are based on multi-component matrix systems of bifunctional methacrylatemonomers(1). Being bifunctional, these highly reactive

Group No. of samples Release/Group (µgms) Release/Group(%) p.value

Mean SD Mean SD

I 17 538.30 37.78 1.58 0.11

II 17 352.20 22.05 0.88 0.06 p<0.02

III 17 725.40 23.21 1.61 0.05

Table 2: Release of BisGMA

Graph 1: Release of BisGMA Graph – 2: Release of TEGDMA

Graph - 3: Combined Release of BisGMA and TEGDMA

Sujathan U-Nu


19



monomers can activate four adjacent monomers in a threedimensional network forming a polymer chain and crosslinking(9). But, one of the issues related to the polymerizationkinetics has been the lack of complete conversion ofmonomers to polymer during polymerization(18).

It has been noted that, as polymerization reactionproceeds, the diffusion rate of propagating free radicalsdecreases. The unreacted methacrylate molecules andpendent methacrylate molecules are also reduced. Thiscauses a significant percentage of methacrylate groups toremain unreacted(19). Various researchers have reportedthe degree of conversion of composite resins to vary between43.5 to 73.8 percent(3,4,20).

Lack of achieving complete polymerization does notindicate that the remaining amount of monomer is lying freeor unreacted in the polymer network. But they are in variousstages of polymerization with reactive free radicals, pendentdouble bonds and some amount of free unreactedmonomers(9). Taira et al. (10) found out that upto 6% of themonomers in a BisGMA – TEGDMA based resin wereunreacted.

The present study looked into the elution of monomers(BisGMA – TEGDMA), immediately after polymerization, whenimmersed rapidly in a solvent – ethanol. It is an establishedfact that salivary components, food simulating liquids andother organic solutions have varying effect on the solubilityand degradation of various components of compositeresin(21,22,23). Similarly ethanol has shown maximumability to extract residual monomers(11,13,24). This has beenattributed to their ability to penetrate and swell the polymerchains and which in turn can facilitate the release ofentangled free monomers from the set composite(11,24). Inorder to simulate clinical scenario, Ferracane and Condon(11) advocate a rapid immersion of samples in the solvent.

The rapid immersion would have eliminated the effect ofpost irradiation polymerization on the net free monomeravailable for elusion process.

Nathensen et al. (25) studying various sealants showedthat TEGDMA has a maximum release within the first 4 minutesand the release reduced there-after. The results of this studyindicate that all three groups tested had residual monomerswhich leached out during the four minutes immersion period.The percentage of elution varied between these three groups,but the values were in confirmation with previous studies.This variation in elution may be influenced by factors likecomposition and viscosity of the monomer, the strong solventused for this study, rapid immersion and duration used forimmersion.

Various in-vitro studies have shown a negativecorrelation of viscosity of resin with respect to degree ofconversion.(16,26) The Monomers like BisGMA and UEDMAare stiff and viscous.(1) In comparison, the diluent monomerlike TEGDMA has values of molecular weight and viscosityhalf that of BisGMA(1). It has been established that anincrease in the amount of diluents or low viscosity monomers,increases the flexibility of the polymer chain as it progressaway from the light source, which helps in increasing thedegree of polymerization.(18,26) This may be one of thereasons for the variations in the release of monomers fromthe tested materials.

Group I had BisGMA and TEGDMA. They were in a ratio of50:50, Santerre et al. (1999)(27) demonstrated that thismaterial (Z100) is highly susceptible for enzymaticdegradation. Ferracane (1994)(8) stated a poor degree ofconversion in relation to Group I material. These reasonsmay explain the high amount of monomer release for Z 100(2.76%). Group III material (SpectrumTPH) had BisGMA,TEGDMA and BisEMA as monomers. The addition of an extra


Mean SD Mean SD

I 17 398.80 39.14 1.17 0.12

II 17 109.70 6.26 0.27 0.02 p<0.02

III 17 289.80 16.03 0.64 0.05

Table 3: Release of TEGDMA


Mean SD Mean SD

I 17 937.10 72.10 2.76 0.21

II 17 461.40 26.06 1.15 0.07 p<0.02

III 17 1015 31.77 2.26 0.07

Table 4: Combined Release of BisGMA and TEGDMA


20

monomer to the composition increases the reactivity of theresin and this may be the reason for lesser elution ofmonomer from this group (2.26%). Though it could not beconclusively proved, why there was maximum release ofBisGMA (1.61%) in this group, the addition of Bisphenol Abased BisEMA may be stated as the reason for an increase inthe release of base monomer.

Group II material (Tetric Ceram) contained BisGMA,TEGDMA and UEDMA as monomers. Muller et al. (1997)(28)established that BisGMA & TEGDMA based resin leachedtwice the amount of monomers as that of UEDMA & TEGDMAbased resins. UEDMA based resins showed a better degreeof conversion. UEDMA used in dentistry can be of two types,both the varieties are less viscous than BisGMA(29). Thesereasons might have contributed for the significantly lesseramount of monomer release from Group II (Tetric Ceram -1.17%) as compared to the other two groups.

In a clinical scenario the release of monomers couldoccur due to the oxidation of the surface layer and thehydrolytic degradation of the remaining portion by variousenzymes and oral fluids(21,22,23,29). Oxidation occurs inthe unpolymerized surface inhibition layers of the setcomposite restorations. The free unreacted monomers fromthis thin layer can leach out immediately after the restorationis placed(29). The pendent methacrylate groups (unreacteddouble bonds attached to one end of the polymer chain) arenot free to elute. But it has been presumed that the action ofesterase and other oral fluids on these pendent methacrylategroups can lead to the release of these monomers(9).Ferracane and Condon(11) found out that, the elution ofcomponents were rapid and mostly complete within the first24 hours from the placement of the restoration. Yap etal.(2000)(29) suggested that any release that occurred after24 hours of curing has been mainly due to hydrolysis process.

In the light of controversy regarding the possible toxicand carcinogenic effect of Bisphenol A andBisGMA(15,16,17) the release of monomers frompolymerized composite restorations gains significance.Many cytotoxic studies have pointed out Bisphenol A as acytotoxic agent in high doses(16).

Bisphenol A (BPA) a small, estrogenic monomer has widespread uses in routine life. This is polymerized to producepolycarbonate plastics and resins used to line metal cans.BPA is also used as an additive in other types of plastics,such as polyvinyl chloride (PVC), used in medical tubing,toys and water pipes and polyethylene terephthalate (PET),used in soda and mineral water bottles(30).

In dental composites they can exist as an impurity alongwith BisGMA, of which it is a major constituent(31). Thismakes it a possibility for its presence and leaching out fromthe composite resins.

Soderholm and Mariotti (1999)(31) pointed out that theconcentration of BisGMA required for such an effect onhealth is 2500 times the concentration necessary forEstradiol to produce similar effect than what is released

from the normal amount used in the oral cavity.An expert panel for evaluation of BPA expressed some

concerns that exposure to BPA in utero causes neural andbehavioral effects(32). Wade et al. (2010)32 considered thebenefits of resin-based dental materials and the brevity ofBPA exposure, and recommended continued use with strictadherence to precautionary application techniques.Materials should be minimized during pregnancy wheneverpossible. Manufacturers should be required to reportcomplete information on the chemical composition of theproducts and encourage to develop materials with lessestrogenic potential.

ConclusionFrom this study it can be concluded that a definite amount

of monomer was released from all the three materials thatwere tested. The release varied between the three groups.The addition of diluents or part substitution of basemonomers may have affected the release of monomers. Thehigh release of monomers obtained in four minutes ofimmersion suggest the necessity for further long term in-vitro and in-vivo studies to evaluate the release of monomersand their toxic effects.

References1. Craig RG: Restorative Dental Materials. Harcourt Brace & Company Asia

Pvt. Ltd. Mosby year book Inc. USA, 10th Edition pp 244-245; 1996.

2. Lutz F, Phillips RW, Roulet J and Scotts J: In-vivo and in-vitro wear of potential

posterior composites. J Dent Res 63 : 914-918; 1984.

3. Chung K and Greener EH: Degree of conversion of seven visible light cured

posterior composites. J Oral Rehabili : 15 : 555-560; 1988

4. Ferracane JL and Greener EH: Fourier transform infrared analysis of degree

of polymerization in unfilled resins – method comparison. J Dent Res 63(8):

1092-1095; Aug. 1984.

5. Ruyter I.E.: Monomer systems and Polymerization, in posterior composite

resin dental restorative materials, Vanherle G, Smith DC editers, Amsterdam

Peter Szulc Publishing Co. pp 1909-115; 1985.

6. Ferracane JL, Moser EH and Greener EH : Ultraviolet light induced yellwing

of dental restorative resins. J Prosthet Dent 54: 483-487; 1985.

7. Ferracane JL and Greener EH: The effect of resin formulation on the degree

of conversion of mechanical properties of dental restorative resins. J Biomed

Mater Res 20: 121- 131;1986.

8. Ferracane JL: Elusion of leachable components from composites. J Oral

Rehabili 21: 441-452; 1994.

9. Burtscher P: Stability of radicals in cured composite materials. Dent Mater

9: 219-221

10. Taira M, Khan AM, Ohmotok, Satou N, Shintani H, Wakasak et al: Curing

performances of four experimental BisGMA based binary monomer

mixtures for dental visible light cured composite resin inlays. J Mater Sci

Lett l3:1229-1231; 1994.

11. Ferracane JL and Condon JR: Rate of elution of leachable components from

composites . Dent Mater 6: 282-287; Oct.1990.

12. Inoue K and Hayasih I: Residual monomers (BisGMA) of composite resins.

J Oral Rehabili 8: 492-497; 1982.

13. Thompson LR, Miller EG and Bowler WH: Leaching of unpolymerized

materials from Orthodontic bonding Resin. J Dent Res 61(8): 989 - 992;

Aug.1982.

14. Anderson DAF, Ferracane JL, Zimmerman ER: Cytotoxicity of combinations

of dental composite components. J Dent Res 66:133 Abst, No. 214; 1987.

15. Hanks CT, Srawn SE, Watha JC and Craig RG: Cytotoxic effects of resin

components and cultured mammalian fibroblasts. J Dent Res 70(11): 1450-

1455; Nov 1991.

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16. Mariotti A, Soderhorm KJ, Johnson S : The in-vivo effects of BisGMA on

murine uterine weight, nucreic acids and collagen. Eur J Oral Sci106: 1022-

1027; 1998.

17. Olea N, Pulgar R, Perez p et al.: Estrogenicity of resin based composites and

sealants used in dentistry, Environ Health Perspect 104(37): 298-305; 1996.

18. Lovell LG, Newman SM and Bowman CN: The effect of light intensity,

temperature and co-monomer composition on the polymerization behavior

of dimethacrylate Dental resins. J Dent Res 78(8): 1469-1476; Aug. 1999.

19. Cook WO: Polymerization defects, in composite resins. Vanherle G, Smith

DC editors, proceedings of the international symposium on posterior

composite resin dental restorative materials. Utrecht Peter Szulc Publishing

Co. pp 273-286; 1985.

20. Chung KH : The relationship between composition and properties of posterior

resin composites. J Dent Res 69(3): 852-856; March 1990.

21. Chadwik RG, Mc Cabe JF, Walls AWG, Stores R: The effect of storage media

upon the surface microhardness and abrasion resistance of three

composites. Dent Mater 6:123-128; Apr 1990.

22. Larsen IB, Freund M, Munksgard EC: Change in surface hardness of Bis

GMA/TEGDMA polymer due to enzymatic action. J Dent Res 71(11):1851-

1853; Nov.1992.

23. Soderholm KJM, Mukherjee R and Langmare J: Filer leachability of

composite stored in distilled water or artificial saliva. J Dent Res 75(9): 1962-

1699; Sep. 1996.

24. Pilliar RM, Vowles R and Williams DF: The effect of environmental aging in

fracture toughness of Dental Composites. J Dent Res 66(3):722-726: Mar.

1987.

25. Dan Nathensan, Prinda Lertpitayakun, Mark S Lamkin Mahnaz

Edalaptopour, Lee Choul: In-vitro evaluation of leachable components from

dental sealants. J Am Dent Assoc 128: 1517-1523; Nov 1997.

26. Silikas N, Watrs DC: Rheology of urethane dimethacryrate and diluent

formulations. Dent Mater 15 :257-261; 1999.

27. Santerre JP, Shajii L and T Sang H: Biodegradation of commercial dental

composites by cholesterole estrate. J Dent Res 78(8): 1459-1468; Aug.

1999.

28. Muller H, Olsson S Soderholn KJ: The effect of co-monomer composition,

silane healing & filler type on aqueous TEGDMA leachability in resin

composites. Eur J Oral Sci 105(4): 362-8; Aug1997.

29. Yap AUJ, Lee HK and Sabapathy: Release of methacrylic acid from dental

composites. Dent Mater 16: 172-179; 2000.

30. Abby F. Fleisch, Perry E. Sheffield, Courtney Chinn,Burton L. Edelstein,and

Philip J. Landrigan: Bisphenol A and Related Compounds in Dental Materials.

Pediatrics 2010; 126: 760–768

31. Soderholm KJ and Mariotti A: BisGMA - Based resins in dentistry: Are They

Safe? J Am Dent Assoc 130: 201-209: Feb 1999.

32. National toxicology program, Center for the evaluation of risks to human

reproduction: Expert panel evaluation of Bisphenol A, meeting summary

August 6-8, 2007

33. Wade V. Welshons, Susan C. Nagel, and Frederick S. vom Saal: Large

Effects from Small Exposures. III. Endocrine Mechanisms Mediating Effects

of Bisphenol A at Levels of Human Exposure. Endocrinology 147: S56–S69;

2006.


22

A critical objective in endodontic therapy is completeelimination of microorganisms from the root canalsystem(1). In order to accomplish this objective, it is essentialto use an irrigant or combination of irrigants during thebiomechanical preparation of the canal system(1). Rootcanal systems are irregular and complex with many cul-de-sacs, fins and lateral canals. Microorganism present in theroot canal can invade these anatomic irregularities as wellas penetrate the dentinal tubules opening onto the root canalsurface to establish infection(2). Root canal infection canprompt the host to respond with a combination of non specificimmunologic responses, and inflammatory lesions in theperiapical tissues.

Candida Albicans has long been implicated as one ofthe most resistant microorganism infecting the root canalsystem. Even after careful chemo-mechanical debridementit has the ability to survive ‘entombed’ in well obturated root

canals leading to persistence of root canal infection.A biofilm is defined as a microbial community

characterized by cells that are attached to the substratumthat are in a matrix of extracellular polymeric substanceand exhibit altered growth phenotypes. Biofilm protect thefungi from harmful environmental conditions including effectof various antifungal agents(2).

Usage of endodontic irrigant during instrumentation notonly reduces the number of microorganisms from the canalsbut it also flush out the debris from the root canal system.An endodontic irrigant should ideally exhibit powerfulantimicrobial activity, dissolve organic tissue remnants,disinfect the root canal space, flush out debris from theinstrumented root canals, provide lubrication, and have nocytotoxic effects on the periradicular tissues, among otherproperties(2).

Sodium hypochlorite (NaOCl), the most commonly usedendodontic irrigant nowadays, has many of these properties,but it has a cytotoxic effect when comes into contact with theperiapical tissues, a foul smell and taste, a tendency tobleach clothes, and corrosive potential. It is also known toproduce allergic reactions. Therefore, an equally effectivebut safer irrigant is desirable(7).

Chlorhexidine (CHX) is widely used as a mouth rinse in

Aims and objectives: To evaluate quantitatively and qualitatively, the antifungal activity of MTAD, 2% chlorhexidine

gluconate, 5.25% sodium hypochlorite against Candida Albicans biofilm.

Materials and Methods: Freshly extracted intact human single rooted mandibular premolars [40 numbers}were

used for the study. The specimen was stored in normal saline. The selected premolars was cleaned of the

residual tissues and slime layer with the help of a brush with soft bristles. The crowns were sectioned at the

cementoenamel junction with the help of a fine diamond disc at 15mm length. The diameter of the root

samples were standardized using K file size 25 which was binding as well as just appearing at the apex. The

samples were labeled and marked as follows,. Group 1: 10 teeth irrigated with 2% Chlorhexidine gluconate.

Group 2 : 10 teeth irrigated with 5.25% sodium hypochlorite. Group 3 : 10 teeth irrigated with Biopure MTAD.

Group 4: 10 teeth irrigated with distilled water. The anti fungal activity of selected irrigants in removing

Candida albicans biofilm in dentinal tubules was assayed both qualitatively and quantitatively. For qualita-

tive assessment the florescent microscopy and quantitative assessment total viable count was done.

Results: Results clearly showed that Chlorhexidine (Group 1) and Sodium Hypochlorite (Group II) was most

effective in reducing colonies of Candida Albicans. The values of Group I (CHX) and Group II (NaOCl) showed

statically significant difference when compared to Group III(MTAD) and Group IV (Distilled Water).

Conclusion: The study showed that Chlorhexidine 2%, and Sodium hypochlorite 5.25% were equally effective

and significantly superior to MTAD and distilled water in removal of Candida albicans biofilm.

Abstract

Comparison of Anti Fungal Efficacy of Three Root Canal Irrigantson Candida Albicans Biofilm - An Invitro Study

* Afzal.A, ** Maya Nandkumar, *** S.Ignatious Rex

* Senior Lecturer, Dep of Conservative Dentistry &

Endodontics, P.M.S.College of Dental Science and Research,

Vattapara, Trivandrum,

** Head of Microbiology, BMT wing. Sri Chitra Institute,

Trivandrum,

*** Professor and Head of the Department, Department of

Conservative Dentistry and Endodontics, Rajas Dental

College. Triunelveli.


23

the prevention and treatment of periodontal diseases anddental caries, and has been suggested as an irrigatingsolution or intracanal dressing in endodontic therapy.

Biopure MTAD ( Dentsply, Tulsa, OK ) introduced in 2003is a mixture of tetracycline isomer [Doxycycline ), an acid(citric acid ), and a detergent (tween 80) MTAD used as afinal rinse, when used in combination with 1.3% sodiumhypochlorite as root canal irrigant was more effectiveagainst C.albicans than 5.25% sodium hypochlorite with17% EDTA. (Shabahang & Torabinejad).

The aim of this Invitro study is to evaluate quantitativelyand qualitatively, the antifungal activity of MTAD, 2%chlorhexidine gluconate, 5.25% sodium hypochlorite againstCandida Albicans biofilm when used individually.

Materials and Methods40 freshly extracted intact human single rooted

mandibular premolars were used for the study. The specimenwas stored in normal saline. The selected premolars wereimmersed in 5% sodium hypochlorite solution for 30 minutesand cleaned of the residual tissues and slime layer with thehelp of a brush with soft bristles. The crowns were sectionedat the cementoenamel junction with the help of a finediamond disc at 15mm length. The diameter of the root canalswere standardized using K file size 25 which was binding aswell as just appearing at the apex.

The teeth were immersed in 17% EDTA and subjected toultrasonic vibration in ultrasonic cleaner (Cole Palmer 8890)for 10 minutes, then in 5% sodium Hypochlorite for 10minutes followed by washing in distilled water three timeswith 10 minutes of ultrasonic treatment. The procedure wasdone to eliminate the smear layer produced during initialpreparation. All samples were sterilized by auto claving at1210C 15Psi for 15minutes.

The fungal strains used for the study

Candida albicans ATCC 10231. The fungal strain for thestudy was maintained in Sabouraud agar slope, inrefrigerator.

Biofilm formation in prepared tooth samples

Candida albicans were subcultured from stock culturemaintained in Sabouraud agar plate in the laboratory. Singlecolony of the fungal strains was inoculated from these in

Table 1 Viable count in cfu/ ml of ATCC strain of C.albicans after treatment with irrigants used in the study

Irrigant Used Viable count Mean Standard Deviation

2% chlorhexidine tooth 1 to

gluconate tooth 6 No growth 0.00 0.00

5.25% Sodium tooth 1 to

Hypochloride tooth 6 No growth 0.00 0.00

Tooth 1 5500

Tooth 2 4500

Tooth 3 5000

Biocure MTAC Tooth 4 4500 5083 584

Tooth 5 5000

Tooth 6 6000

Tooth1 7500

Tooth 6500

Tooth 8000 7250 689

Distilled water Tooth 7000

Tooth 6500

Tooth 8000

Result of F-Test for Candida albicans Table 1

Sum ofsqmuares df Mean square F Sig

Betweengroups 2.4225E+11 3 80750000 395510

Withingroups 20 204166.667

Total 23

F test shows that there was a statistically significant difference inthe number of colony forming units when different irrigants areused. The P value was 0.00 which is statistically significant

Comparison of Anti Fungal Efficacy of Three Root Canal Irrigants on Candida Albicans Biofilm


24

Sabouraud agar plate cultures into 100ml fluidthioglycollate and incubated at 370C and 150rpm for 2 hours.After two hours when the culture enters the logarithmicphase of growth the prepared teeth specimens were addedand continued incubation at 370C at 60 rpm for 7 days.Every second day 75ml of fresh thioglycollate was addedafter removal of 75ml culture. This ensured sufficient nutrientsupply and prevented accumulation of metabolic waste.

All the procedure were performed under strictly asepticcondition in a biological safety cabinet.

Grouping

The processed specimens of 40 teeth was further dividedinto four groups of ten teeth each according to the selectedirrigants. They were labeled and marked.

Group 1: 10 teeth irrigated with 2% Chlorhexidinegluconate

Group 2 : 10 teeth irrigated with 5.25% sodium hypochlorite

Group 3 : 10 teeth irrigated with Biopure MTADGroup 4: 10 teeth irrigated with distilled water.

Agar diffusion test :5µl of irrigant was impregnated into sterile filter paper

discs and the test was conducted by Agar Diffusion Method.The test fungi were inoculated onto Mueller Hinton agar togive a lawn culture. The test and the control sample discswere placed on the media and incubated at 220C for 48 hours.Standard Amphotericin–B was used as positive control.Negative control was filter paper disk impregnated withsterile distilled water (Fig.1).

Analysis of Candida Albicans biofilm removal.The anti fungal activity of selected irrigants in removing

Graph1 : Evaluation of efficacy of the different irrigants by thetotal viable count. Viable count projected on the Y-axis and

different irrigants on the X-axis

Fig. 2 TSB viable count plate of C.albicans, after irrigation of root canal with:

5.25% sodium Hypochlorite 2% Chlorhexidine Gluconate MTAD Distilled water

Fig 1. Zone of inhibition obtained by the agar diffusion methodfor assay of antifungal sensitivity of various irrigants.

Name of the antimicrobial agent Zone of inhibition

2% Chlorhexidine gluconate 5 µl/disc 18mm

5.25% sodium hypochlorite 5 µl/disc 13mm

Biopure MTAD5 µl/disc nil

Distilled water5 µl/disc nil

Amphotresin- B 17mm

Afzal A.


25


Candida albicans biofilm in dentinal tubules was assayedboth qualitatively and quantitatively. For qualitativeassessment florescent microscopy and for quantitativeassessment total viable count was done.

The canals were flushed with 3ml of sterile phosphatebuffered saline for removing loosely bound fungal cellsfollowed by mechanical preparation. Cleaning and shapingof each group was done using step back technique with 40size file as master apical file. All the specimens were irrigatedusing 5ml syringe. The canals were passively irrigated with1ml of selected irrigants at constant rate of 4-5 secondseach. At the end of the biomechanical preparation all theroot canals were flushed with 3ml of test irrigant and thecanals were then dried with sterile paper points. Forquantitative assessment six teeth from each group were usedfor viable count and for qualitative analysis four teeth fromeach group were sectioned vertically and used for fluorescentmicroscopy.

Quantitative assessment by the total viablecount. (Fig.2)

The tooth samples were aseptically transferred into asterile tube. Sufficient volume (measured) of phosphatebuffered saline (PBS) was added to the tube, so as to immersethe sample completely. The tubes were placed in ultrasoniccleaner and ultrasonicated for 1 min. After ultrasonication,the test tube were vortexed for 1 minute. Ultrasonicationand vortexing was done for three times. The supernatantwas collected. 1 ml of sterile PBS were again added into thetest tube and the steps were repeated and the supernatantwas also collected.. The total supernatant collected wascentrifuged at 300 rpm for 5 minutes. The supernatant wasdiscarded and residual pellet was resuspended in 5 ml ofPBS and 10 µl taken in micropipette and plated in Petridishcontaining Sabouraud dextrose ager. For doing viablecounting of this undiluted sample, 100 µl was added to 4900µl of sterile PBS and mixed for uniformity, giving one in fiftydilution (Fig.2)

From the diluted sample 10 µl, 25 µl and 50 µl wasplated on to SDA and incubated at 22.50C for 48 hours. Each

of this dilute sample was divided into three and viablecounting done in all the Petri dishes. The mean count ofthese Petri dishes was taken as the viable count of the sample.These procedures were done for the entire specimen in allthe groups. The mean of each group was calculated andstandard deviation determined. The tabulated data wasstatistically analyzed with one way analysis of variance(ANOVA), with the help of SPSS software.

Qualitative assessment by fluorescentmicroscopy

Acridine orange staining (Fig.3)Four teeth from each set after the biomechanical

preparation were sectioned vertically with the help ofdiamond disc and kept in a bijoux bottle and washed in PBSto remove loosely bound bacteria and fixed with 5%glutaraldehyde for 1 hour. Then they were washed in PBSand stained with 0.1 % of 5 ml Acridine orange for 15 minutes.Excess stains from the tooth was washed off with PBS. Airdried and examined under fluorescent (Lieica DMR) at 100xmagnification.

ObservationsThe complex anatomy of the root canal makes the

analysis of the effectiveness of these irrigants difficult. Inthis study we have evaluated the three irrigants used inclinical practice for its effectiveness in removing fungalbiofilm formed in dental tubules, in a controlled laboratoryset up.

Agar diffusion method for analysis of antifungalactivity of the different irrigants

Agar diffusion method is a common means of assayingantimicrobial sensitivity for compound or substance. Inthis test the diameter of zone of inhibition formed gives anidea of the sensitivity of the fungi to the compound orsubstance tested. In such a method it is the planktonic formsof the fungi which was used for the test and does not representfungal behavior in the biofilm.

Fig.3 Fluorescent Micrograph of biofilm formed in the root canalby C.Albicans, after irrigation with

Fig 3a Distilled Water Fig 3b MTAD

Fig.3 Fluorescent Micrograph of biofilm formed in the root canalby C.Albicans, after irrigation with

Fig 3c 2% ChlorhexidineGluconate

Fig 3d 5.25% SodiumHypochlorite


26

Results:Among the ATCC strains of C.albicans (Table 1 &2),

Group 1 (2% Chlothexidine gluconate) and Group 2 (5.25%sodium hypochlorite) had a mean of zero colony formingunits. When comparing Group 3 (Biopure MTAD) the meanwas 5083 and for distilled water was 7250 respectively.There was statistically significant difference between MTADand distilled water. There was no significant difference inthe number of bacteria between Group 1 (2% Chlorhexidinegluconate) and Group 2 (5.25% sodium hypochlorite). Whencomparing Group 1 and Group 2 with Group 3 (Biopure MTAD)and Group 4 (distilled water) there was significant differencein the number of bacteria. Chlorhexidine 2% and sodiumhypochlorite 5.25% was effective in removal of biofilm MTADand distilled water was inefficient in destroying C.albicansbiofilms (Graph1).

The teeth samples with biofilm were stained withAcridine orange and examined by fluorescent microscope.The fungi DNA takes up the fluorescent dye and gives orangered fluorescence indicating the presence of bacterial biofilm.The yellowish green is background showing absence ofbiofilm (Fig.3).

Fig. 3c and 3d shows flourescent microscope pictureswhen samples were treated with 2% Chlorhexidine and 5.25%sodium hypochlorite. The microscopic examinations showsthe absence of biofilm.

Fig 3a and 3b are representative picture showing thepresence of fungal biofilm when the samples treated withMTAD and distilled water.

DiscussionIrrigation is an important procedure in eliminating both

planktonic forms of microorganisms and biofilms from theroot canal system. Irrigation should also remove smear layerand dentin debris that occur following instrumentation ofroot canal(3)

A smear layer is produced on instrumented canal wallwhich is comprised of inorganic and organic material. Thisdeposit can be penetrated by fungi and may offer protectionto fungal biofilm, adhering to root canal walls and promotemicro leakage.

Fungi may be found in two basic forms, molds and yeasts.Candida albicans is a dimorphic fungus – exists inblastospore and hyphal forms. Candidate albicans grow ina number of morphogenic forms blastospores, germ tubes,true hyphae, psedohyphae,, depending on environmentalconditions(9)

Candida species can cause a wide variety of infectionsin the human being, ranging from superficial diseases to thelife threatening disseminated mycoses(3). Candida albicansis also one of the main pathogens of hospital acquiredinfection(3). Candida albicans is the fungal species mostcommonly detected in the root canal of both healthy andmedically compromised individuals(4). The inability toeliminate fungi from the root canal results in refractory

endodontic infections and these are caused by fungal biofilm.C. albicans can penetrate into the root canal system either

by contamination during endodontic treatment or by meansof recontamination as a result of coronal leakage. Thetransition of C. Albicans to its pathogenic form appears tobe dependent on variety of virulence factors includingadherence, hyphal formation, thigmotropism, proteasesecretion, and phenotypic switching phenomenon(5).

In the present study the efficiency of these irrigants wasanalyzed. We used the three irrigants 2% Chlorthexidinegluconate. Biopure MTAD, 5.25% sodium hypochlorite andDistilled water as control

Biopure MTAD is a biocompatible material and hasminimal effects on the physical properties of the tooth. Theeffectiveness of Doxycycline is due to its low pH, its anti-collagenase activity and its ability to bind to dentin andrelease gradually overtime(14). Ability to remove organicand inorganic substances from the surface of the root isfacilitated by presence of citric acid. Presence of detergentaids its propensity to diffuse into the root canal and thedentinal tubules(11).

The fungicidal ability of sodium hypochlorite results fromthe formation of hypochlorous acid (HDC) when in contactwith organic debris. Hypochlorouos acid exerts its effectsby oxidizing sulphdryl groups within fungal enzyme systemthere by disrupting the metabolism of the microorganismresulting in killing of the fungal cells. Sodium hypochlorite5.25% was considerably stronger than necessary toeliminate fungal strains, commonly found in infected rootcanals.

Agar diffusion test is a common microbiological studyused in clinical practice for determining the most suitablechoice of antibiotics to be used in treatment of infectiousfungal diseases. Fungi in biofilm are resistant to more thanthousand times the concentration of an antibiotic, which issensitive to the planktonic form. When zone of inhibition isassayed, it showed that both 5.25% sodium hypochloriteand 2% chlorhedixine exhibited anti-bacterial propertyagainst Candida albicans when compared to Biopure MTADand distilled water. Bio-pure MTAD and Distilled watershowed no inhibition zones where as 2% chlorhexidineshowed inhibition zone of 18mm and 5.25% sodiumhypochlorite showed 13mm. (Fig.1)

But this method doesn’t reflect the clinical scenario whenthe irrigants are exposed to fungal biofilm. So we used theboth model described here to evaluate the efficiency of theirrigants to remove the Candida albicans biofilm from thecomplex architecture of the dentinal tubules when usedindividually. Candida albicans was chosen as test fungibecause it has been associated with persistent apicalinflammation in clinical situations.

Among the ATCC strains of C.albicans, (Table1) Group 1(2% Chlothexidine gluconate) and Group 2 (5.25% sodiumhypochlorite) had a mean of zero colony forming units. Whencomparing Group 3 (Biopure MTAD) the mean was 5083 and

Afzal A.


27


for distilled water was 7250 respectively. There wasstatistically significant difference between MTAD anddistilled water. There was no significant difference in thenumber of bacteria between Group 1 (2% Chlorhexidinegluconate) and Group 2 (5.25% sodium hypochlorite). Whencomparing Group 1 and Group 2 with Group 3 (Biopure MTAD)and Group 4 (distilled water) there was significant differencein the number of bacteria. Chlorhexidine 2% and sodiumhypochlorite 5.25% were effective in removal of biofilm whileMTAD and distilled water were inefficient in destroyingC.albicans biofilms. (Graph1)

When antifungal property of the root canal irrigantswas examined using agar diffusion method, 5.25% sodiumhypochlorite had zone of inhibition 13mm, in case of 2%chlorhedixine zone of inhibition was 18mm, while BiopureMTAD had no zone of inhibition. The antifungal property of5.25% sodium hypochlorite is due to the nascent chlorinewhich gets evaporated on drying, leaving the disc free of amajor portion of nascent chlorine and reducing the antifungalproperty. When testing as irrigant we use freshly preparedsolutions of sodium hypochlorite which is the mostactive.(Fig.1)

These results clearly showed that Chlorhexidine 2%, andSodium hypochlorite 5.25% were equally effective andsignificantly superior to MTAD and Distilled water in removalof Candida albicans biofilm.

Conclusion

Under the parameters of this study the followingconclusion were made.

1. Sodium hypochlorite 5.25% and chlorhexidine 2%were the most effective in reducing Candida Albicans biofilm.

2. The study showed that Sodium hypochlorite 5.25%and chlorhexidine 2% were superior to MTAD and distilledwater in controlling Candida albicans biofilm.

References :1. Egan MW, Spratt DA, Ng YL, Lam JM, Moles DR, Gulabivala K. Prevalence

of yeasts in saliva and root canals of teeth associated with apical

periodontitis. Int Endod J 2002;35:321-9.

2.. Sundqvist G. Taxonomy, ecology, and pathogenicity of the root canal flora.

Oral Surg Oral MedOralPathol1994;78:522-30.

3. Nair PN, Sjögren U, Krey G, Kahnberg KE, Sundqvist G. Intraradicular

bacteria and fungi in root-filled, asymptomatic human teeth with therapy-

resistant periapical lesions: a long-term light and electron microscopic

follow-up study. J Endod1990;16:580-8.

4. Sundqvist G. Ecology of the root canal flora. J Endod. 1992 Sep;18(9):427-

30.

5. Baumgartner JC, Watts CM, Xia T. Occurrence of Candida albicans in

infections of endodontic origin. J Endod 2000;26:695-8.

6. Harrison JW. Irrigation of the root canal system. Dent Clin North Am

1984;4:797-808.

7. Senia ES, Marraro RV, Mitchell JL, Lewis AG, Thomas L. Rapid sterilization

of gutta-percha with 5.25% sodium hypochlorite. JEndod 1975;1:136-40.

8. Moorer WR, Wesselink PR. Factors promoting the tissue dissolving

capability of sodium hypochlorite. Int Endod J 1982;15: 187-96.

9. White RR, Hays GL, Janer LR. Residual antimicrobial activity after canal

irrigation with chlorhexidine. J Endod 1997;23:229-21

10. Cervone F, Tronstad L, Hammond B. Antimicrobial effect of chlorhexidine

in a controlled release delivery system. EndodDent Traumatol 1990;1:33-

6.

11. Ferraz CCR, Gomes BPFA, Zaia AA, Teixeira F, Souza-FilhoFJ. In vitro

assessment of the antimicrobial action and the mechanical ability of

chlorhexidine gel as an endodontic irrigant. JEndod 2001;27:452-5.

12. Haapasalo M, Orstavik D. In vitro infection and desinfection of dentinal

tubules. J Dent Res 1987;66:1375–9.

13. Tronstad L, Barnett F, Riso K, Slots J. Extra-radicular endodontic infections.

Endod Dent Traumatol 1987;3:86–90.

14. Sundqvist G, Johansson E, Sjo¨ gren U. Prevalence of black-pigmented

bacteroides species in root canal infections. J Endodon 1989;15:13–9.


28

IntroductionThe clinical success of composite restorations depends onadhesive systems that provide durable bonding of compositeto dentin and effectively seal the dentinal tubules to preventpostoperative sensitivity and microleakage. Most of the one-bottle dentin bonding systems are composed of hydrophilicand hydrophobic resins dissolved in high vapour pressureorganic solvents such as ethanol or acetone that chase thewater and bring the monomers into intimate contact withthe exposed collagen fibers following acid etching ofdentin[1]. Resin penetration into dentin with monomerimpregnation of the exposed collagen resulting in formationof hybrid layer is widely accepted as an efficient method toimprove the resin - composite bond strength to dentin [2].Dissolution of collagen after acid conditioning may resultin better resin diffusion by increasing dentin permeabilityand changing its composition leaving it with a layer ofmineral exposed on its surface. More predictable adhesioncould be obtained directly with hydroxylapatite of partiallydemineralized dentin by removing the collagen [3].

Studies have showed that the layer of collagen does notoffer a direct quantitative contribution to the interfacial bondstrength which is probably due to a complete resin diffusioninto porous demineralized dentin and the collagen layer maynot be crucial to the mechanism of adhesion between resinand dentin [3].

Dissolution and removal of the organic collagen layerafter acid conditioning and subsequent bonding directly tothe partially demineralized layer may produce more durableadhesion to the hydroxylapatite component of the dentinsubstrate. Moreover, absence of a non-encapsulated collagenbond at the dentin-resin interface could prevent degradationof this interface after storage in water for extended periods[2].

This study was done to evaluate the effect on dentin shearbond strength with and without application of 5% Sodiumhypochlorite using two single bottle adhesive systems-anacetone based (Prime and Bond NT) and an ethanol based(Single Bond) system and to examine the ultrastructure ofthe resin-dentin interface using Scanning ElectroMicrograph.

Materials and MethodsThe two single bottle adhesive systems used in this study arePrime and Bond NT (acetone based) and Single Bond (alcohol

Aim: To compare dentin shear bond strengths of two single bottle adhesive systems- Prime and Bond NT and

Single Bond with and without application of 5% Sodium hypochlorite on etched dentin.

Methodology: Dentin surfaces of freshly extracted premolars were exposed and divided into four groups of ten

teeth each. In group I, after acid etching, Prime and Bond NT adhesive was applied on dentin and composite

placed. In group II, after acid etching and 5% Sodium hypochlorite application, Prime and Bond NT adhesive

was applied and composite placed. In group III, after acid etching, Single Bond adhesive was applied on

dentin and composite placed. In group IV, after acid etching and 5% Sodium hypochlorite application, Single

Bond adhesive was applied and composite placed. The dentin shear bond strength of the four groups were

evaluated. Scanning electron micrograph of resin-dentin interfaces were evaluated.

Results: The mean dentin shear bond strength of Prime and Bond NT increased while that of Single Bond

decreased following application of 5% Sodium hypochlorite. Scanning electron micrograph evaluation showed

absence of hybrid layer after Sodium hypochlorite application for both the bonding agents.

Conclusion: 5% Sodium hypochlorite application may increase dentin shear bond strength for Prime and Bond

NT and may decrease dentin shear bond strength for Single Bond. Absence of hybrid layer was noted for both

bonding agents after application of 5% Sodium hypochlorite. But more clinical trials need to be carried out

using several dentin bonding agents.

Key words: Dentin shear bond strength, Sodium hypochlorite, adhesive, resin dentin interfaces, hybrid layer.

Abstract

Comparative evaluation of dentin shear bond strength with andwithout Sodium hypochlorite application using two adhesivesystems - An Invitro Study

* Vijay Mathai, ** N.O. Varghese, *** Jolly Mary Varughese

* Reader, Department of Conservative Dentistry and Endodontics,

Sree Mookambika Institute of Dental Sciences, Kulasekharam,

K.K. District, Tamil Nadu;

** Principal, Government Dental College, Trivandrum;

*** Principal, Government Dental College, Calicut


29

based). Both are fifth generation dentin bonding agents. Thecomposite used is Z-100 (3M). Also a 5% solution of Sodiumhypochlorite is used in this study.

Forty recently extracted premolar teeth for orthodonticpurpose were sectioned at the cementoenamel junction,cleaned of debris and stored in distilled water at roomtemperature. Buccal enamel of teeth were removed to exposedentin using diamond disk. The teeth were embedded in selfcure acrylic resin blocks in such a way that the exposedbuccal dentin surface was facing up and slightly above theresin block. The exposed dentin surfaces were polished usinga wet 600 grit silicon carbide paper. The forty specimenswere divided into four groups of ten specimens each andreceived the following treatments.

Group I (Prime and Bond NT)The dried dentin surface was etched with 36% phosphoric

acid gel for 15 seconds. The etchant gel was removed byrinsing with water for 30 seconds and then the dentin surfacewas blot dried using a moist cotton pellet to remove excesswater and leave back a moist glistening surface with nopooling of water. Prime and Bond NT was dispensed onto aclean disposable brush and the adhesive was applied tothoroughly wet all the dentin surface. The surface wasallowed to remain fully wet for 20 to 30 seconds. Excesssolvent was removed by gentle air drying for atleast 5seconds. The adhesive was light cured for 10 seconds.

Group II (5% Sodium hypochlorite + Prime andBond NT)

The dried dentin surface was etched with 36% phosphoricacid gel for 15 seconds. The etchant gel was removed byrinsing with water for 30 seconds and then the dentin surfacewas blot dried using a moist cotton pellet leaving the surfacemoist. The moist dentin surface was then treated with 5%Sodium hypochlorite for 2 minutes and then rinsed with

water and blot dried. Prime and Bond NT was dispensedonto a clean disposable brush and the adhesive was appliedto thoroughly wet all the dentin surface. The surface wasallowed to remain fully wet for 20-30 seconds. Excess solventwas removed by gently air drying for atleast 5 seconds. Theadhesive was light cured for 10 seconds.

Group III (Single Bond)The dried dentin surface was etched with 36% phosphoric

acid gel for 15 seconds. The etchant gel was removed byrinsing with water for 30 seconds and then the dentin surfacewas blot dried using a moist cotton pellet leaving the surfacemoist. Using a fully saturated brush tip of Single Bondadhesive for each coat, two consecutive coats of adhesivewere applied onto dentin surface and dried gently with airstream for 2 to 5 seconds. The adhesive was light cured for10 seconds.

Group IV (5% Sodium hypochlorite + Single Bond)The dried dentin surface was etched with 36% phosphoric

acid gel for 15 seconds. The etchant gel was removed byrinsing with water for 30 seconds and then the dentin surfacewas blot dried using a moist cotton pellet leaving the surfacemoist. The moist dentin surface was then treated with 5%Sodium hypochlorite for 2 minutes and then rinsed withwater and blot dried. Using a fully saturated brush tip ofSingle Bond adhesive for each coat, two consecutive coats ofadhesive were applied onto dentin surface and dried gentlywith air stream for 2 to 5 seconds. The adhesive was lightcured for 10 seconds.

Following the curing of respective adhesives in eachgroup, brass rings having 4mm internal diameter and 4mmheight were placed over dentin surface and firmly held inposition. Z-100 composite resin was compactly packedagainst the dentin surface to fill the ring in increments. Eachincrement was light cured for 40 seconds. The light source

Fig 1 Shear bond evaluation usingUniversal Testing Machine (Instron,

Model 1011 Instron Co, UK)

Figure III(a): Photomicrograph of resin-dentininterface - Prime and Bond NT ( x1000)

Figure III(b): Photomicrograph of resin-dentininferface-NaOCl+Prime and Bond NT (x1000)

Figure III(c) : Photomicrograph of resin-dentininterface – Single Bond ( x 1000)

Figure III(d) : Photomicrograph of resin-dentininterface - NaOCl + Single Bond ( x 1000)

Fig 2

Comparison of the mean shear bond strength of the two

dentin bonding systems with and without Sodium

hypochlorite application

Comparative evaluation of dentin shear bond strength with and without Sodium hypochlorite

application using two adhesive systems


30

Vijay Mathai

from Astralis 3 (Vivadent) curing light polymerization unithaving 400-500nm wavelength range was used for lightcuring the adhesives and composite resin. The samples werestored at 370C in distilled water for 24 hours prior to testingof shear bond strength.

The samples were mounted horizontally onto the lowerjaw of the Universal Testing Machine (INSTRON, Model 1011Instron Co, UK). The machine was interfaced with a computerthrough which operation of the equipment was controlledand shear bond strength was calculated. A 25 guage stainlesssteel wire loop was hooked around the brass ring andattached to the upper jaw of the Universal testing machinewhich was activated to move upwards at a cross head speedof 1mm/min and was used to shear away the brass ringcontaining the composite adhered to dentinal surface (Fig1). Load at fracture was recorded in Newtons and shear bondstrength calculated from the load to the surface area value.

Preparation of samples for SEMBuccal enamel of freshly extracted premolar teeth were

removed to expose dentin using diamond disk. The root portionof teeth were sectioned at cementoenamel junction. Thedentin surfaces were polished using a wet 600 grit siliconcarbide paper. The flat dentinal surfaces of four teeth weretreated as mentioned in the four groups respectively, ie, Primeand Bond NT (Group I), 5% Sodium hypochlorite + Prime andBond NT (Group II), Single Bond (Group III), 5% Sodiumhypochlorite + Single Bond (Group IV) and composite placedand cured. The specimens were then sectioned to expose theresin-dentin interface. These surfaces were further polishedusing a sequence of wet 600, 800, 1000, 1500 grit siliconcarbide paper. After this the surfaces were treated with 10%phosphoric acid for 5 seconds to remove the smear layer.The specimens were then treated with 6 mole/L HCl acid for30 seconds and then rinsed with distilled water. Thespecimens were then immersed in 1% Sodium hypochloritefor 10 minutes after which they were copiously rinsed withdistilled water. This procedure was done to remove a smallamount of dentin to clearly reveal penetration of resin tagsinto dentin tubules. Fixation was then done with 2%Glutaraldehyde. After fixation the specimens were dehydratedin series of ascending ethanol solution and then transferredto the critical point drying apparatus. The specimens werethen mounted on brass stubs and gold sputtered in an ionsputtering unit (E-101, Hitachi Ion Sputter, Japan) and viewedunder a scanning electron microscope (Hitachi ModelS-2400, Japan).

Results and Observations

The load at break and the resulting shear bond strengthwere recorded during the shear bond testing using the twobonding systems

(Fig II). In order to compare the different groups, thestatistical constants like mean, standard deviation etc. werecomputed. The statistical hypothesis formulated were testedwith the help of student 't' test. Also the 95% confidence

interval was computed to predict the possible interval inwhich the 95% observations may lie. All statisticalcalculations were done through SPSS computer package.

It was observed that the mean load at break of group I(Prime and Bond NT) was 159.47N in place of 269.7N forgroup II (5% Sodium hypochlorite + Prime and Bond NT).Thus the load was 1.7 times more in group II compared togroup I. The difference in the load at break between the twogroups have been tested statistically and is found significantat 1% level (p<.01). Thus group II was found to be havingcomparatively better load at break than group I.

While considering shear bond strength too, the sameresult was repeated. Infact in this case the mean shear bondstrength was estimated at 21.44MPa in group II whereas itwas only 12.69MPa in group I. Even in this case the statisticaltest for equality of means turned out to be highly significant(p<.01).

In table II, the load at break/ shear bond strength wascompared of group I with group III. It was noted from table IIthat the mean load at break was 292.88 N in group IIIcompared to 159.47N in group I. In this case almost two foldincrease in load at break was recorded in group III than thatof group I. Similarly the mean shear bond strength was23.3MPa in group III whereas it was only 12.69 MPa ingroup I. Thus in either case, group III appeared to be superiorto group I. The increased load at break as well as shear bondstrength recorded in group III happened to be highlystatistically significant (p<.001).

While considering the load at break and shear bondstrength of group II and group IV, no appreciable differenceis noted statistically. However numerically group II showedslightly better results (mean load of 269.27N in group II and256.39N in group IV) in the case of load strength as well asin shear bond strength (Mean SBS was 21.44 MPa in group IIand 20.40 MPa in group IV). Even then the improvement notedhappened to be not significant statistically (p>.05). In otherwords, statistically group II and group IV seem to be more orless having the same load and shear bond strength.

The data were further analyzed to compare group III withgroup IV. In this case group III showed better resultscompared to group IV. Regarding load at break, group III hada mean of 292.88 N in place of only 256.39 N in group IV.It has been reflected in the same fashion even in shear bondstrength (Mean of 23.30 MPa in group III and 20.40 MPa ingroup IV). In both the cases the better results noted ingroup III turned out to be significant at 5% level (one tailedtest).

In table V it was attempted to estimate the 95% confidenceinterval of shear bond strength in various groups andcompare it with the minimum and maximum values observed.In group III the 95% confidence interval of shear bondstrength was estimated as 22.89MPa to 23.71 MPa whichwas the maximum followed by 19.32MPa to 23.56MPa ingroup II and 18.93 MPa to 21.87 MPa in group IV. Theminimum interval was noted in group I, i.e, 11.62 MPa to13.76 MPa. The actual observation also showed maximum


31

shear bond strength in group III and group II.It was observed that the bond strength of group II was

increased compared to group I while the bond strength ofgroup IV was decreased compared to group III.

SEM evaluationIn the specimen where the cross section of interface

between Prime and Bond NT and 36% phosphoric acid treateddentin was examined, a distinct hybrid layer was evidentwith the penetration of resin tags into dentin tubules [FigIII(a)]. The specimen where the cross section of interfacebetween Prime and Bond NT and dentin substrate treatedwith 36% phosphoric acid and Sodium hypochlorite wasexamined, no hybrid layer was evident and there waspenetration of resin tags into the dentin tubules [Fig III(b)].In the case of the specimen where the cross section ofinterface between Single Bond and 36% phosphoric acidtreated dentin was examined, a distinct hybrid layer wasevident with penetration of resin tags into the tubules [FigIII(c)] while in the specimen where the cross section ofinterface between Single Bond and dentin substrate treatedwith 36% phosphoric acid and Sodium hypochlorite wasexamined, there was absence of hybrid layer and penetrationof resin tags into tubules was evident [Fig III(d)].

DiscussionDentin priming monomers are usually dissolved in

acetone/ and or ethanol which can displace water from thedentin surface and the moist collagen network thus promotingthe infiltration of the monomers through the nano - spaces

of the dense collagen web and enhancing bond strengths.The resin replaces the water within the pores between thecollagen fibres. The dentin bonding systems combine theprimer with the unfilled resin. The manufacturers includemolecules in the same bottle that are mostly hydrophilicwith other molecules having a more hydrophobic behaviourdissolved in an organic solvent. HEMA is a component ofmost priming resins due to its wetting behaviour and itsaffinity for dentin making it acid resistant after impregnation.The affinity of HEMA for dentin seems to be enhanced whenit is combined with a water displacing solvent such asacetone which facilitates water evaporation [1].

In the acetone based systems, the water chasingcapability of the volatile resin solvent appears to displacewater effectively from the intertubular network resulting inoptimal resin infiltration through the collagen network evenin the overwet condition. Under such circumstances,achieving interfacial integrity depends predominantly uponthe ultimate fate of intratubular permeation which in turnwas governed by the moisture within the dentinal tubulesand on the dentin surface [4].

In conventional hybrid layer formation, the mineralphase of dentin is removed by acid - etching and replaced byresin - infiltration around the exposed collagen fibrils. Inreverse hybrid layer formation, acid - etching removes theswear layer and exposes the collagen fibrils of the dentinmatrix. This is followed by application of Sodiumhypochlorite which not only removes the exposed collagenfibrils but also solubilizes the fibrils down into the underlyingmineralized matrix to create submicron porosities within

TABLE I Mean and Standard deviation of Load at break/ SBS in Group I/

II and level of significance

Load/ Group I (n=10) Group II (n=10) “t” value “p” value

SBS Mean S.D Mean S.D

Load at

break

(Newton) 159.47 32.85 269.72 65.45 3.67 p<.01

SBS

(MPa) 12.69 2.62 21.44 5.2 3.69 p<.01

TABLE II Mean and Standard Deviation of Load at break / SBS in

Group I / III and level of significance

Load/ Group I (n=10) Group III (n=10) “t” value “p” value


Load at

break

(Newton) 159.47 32.85 292.88 12.52 9.30 p<.001

SBS

(MPa) 12.69 2.62 23.30 1.0 9.29 p<.001

TABLE III Mean and Standard deviation of Load at break / SBS in

Group II/ IV and level of significance

Load/ Group I (n=10) Group IV (n=10) “t” value “p” value


Load at 269.72 65.45 256.39 45.24 0.39 p>.05

break (Not signi

(Newton) ficant)

SBS 21.44 5.19 20.40 3.60 0.38 p>.05

(MPa) (Not Signi

ficant)

TABLE IV Mean and Standard deviation of Load at break/ SBS in

Group III/ IV and level of significance

Load/ Group III (n=10) Group IV (n=10) “t” value “p” value


Load at

break

(Newton) 292.88 12.52 256.39 45.24 1.864 *p<.05

SBS

(MPa) 23.30 1.0 20.40 3.60 1.87 *p<.05

* Significant at 5% level (one tailed test)

Comparative evaluation of dentin shear bond strength with and without Sodium hypochlorite

application using two adhesive systems


32

the mineral phase. Cylindrical channels (0.1 m in diameter)previously occupied by collagen fibrils are now availablefor resin infiltration with the mineralized matrix [5].

It is seen that the incomplete resin infiltration ofdemineralized dentin can leave exposed collagen at the dentin- adhesive interface. The exposed collagen could be degradedby bacterial proteases comprising the integrity of the dentin- adhesive bond and ultimately the restoration [6].

The removal of collagen matrix after acid conditioningand subsequent bonding to partially demineralized dentincould eliminate or substantially reduce the microleakageassociated with polymerization shrinkage of composite resin.This could eliminate secondary caries associated withmicroleakage and discolouration [7].

The study shows that the bond strength values for Primeand Bond NT were higher after Sodium hypochloritetreatment while the bond strength values of Single Bonddecreased following Sodium hypochlorite treatment. Thepositive effect of Sodium hypochlorite on bond strength ofPrime and Bond NT may be explained by the higherdiffusibility of acetone as well as its higher capacity todisplace water. These factors could improve the contact ofthe monomer with the irregular dentin structure exposed bySodium hypochlorite treatment. Furthermore removingcollagen could improve the contact of adhesive andhydroxyapatite crystals by enhancing dentin permeability.In the case of Single Bond, as this kind of adhesive systemdiffuses more slowly than acetone based systems, this shortdwell time is insufficient to permit a full diffusion of themonomer into the substrate. In this way nanometricporosities of intertubular dentin created by sodiumhypochlorite treatment were not reached by monomer leavingan adhesive interface with voids. This may explain thelowering of bond strengths in case of Single Bond [2].

Under SEM observations, at the resin - dentin interface,the formation of a hybrid layer was only possible when thecollagen network was left intact. When collagen was removedfollowing Sodium hypochlorite application, no hybrid layerwas observed at the resin - dentin interface [2].

Conclusion

1. The mean shear bond strength of Prime and Bond NT

increased after application of 5% Sodium hypochlorite

2. The mean shear bond strength of Single Bond decreasedafter application of 5% Sodium hypochlorite

3. Single Bond appears to be superior to Prime and BondNT in terms of dentin shear bond strength according tothis study.

4. SEM evaluation of the resin-dentin interface showedpresence of hybrid layer without Sodium hypochloriteapplication while there was absence of hybrid layerafter Sodium hypochlorite application for both thebonding agents.

However this being an invitro study, it cannot mimic theinvivo conditions. Moreover it is still unclear what are thelong term effects of application of Sodium hypochlorite onetched dentin invivo and so its use on a clinical setting isstrongly discouraged. More clinical trials may have to becarried out using several dentin bonding agents to understandthe effectiveness of Sodium hypochlorite on etched dentinand subsequently its effect on dentin shear bond strength.

Acknowledgements

We hereby acknowledge the services rendered by Sree

Chitra Institute of Medical Sciences and Technology,

Trivandrum in successfully completing our study.

References1. Jorge Perdigao, Joao.C. Ramos, Paul Lambrechts. Invitro interfacial

relationship between human dentin and one-bottle dentin adhesives. Dentmaterials 1997; 13:218-227.

2. VdePA Saboia, AL Rodrigues, L.A.F Pimenta. Effect of collagen removal onshear bond strength of two single bottle adhesive systems. Operativedentistry 2000; 25:395-400.

3. Vargas. M.A, Cobb D.S, Armstrong S.R. Resin - Dentin Shear bond strengthand interfacial ultrastructure with and without a hybrid layer. OperativeDentistry 1997; 22:159-166.

4. Franklin.R.Tay, John. A. Gwinnett, Stephen H.Y. Wei. Micromorphologicalspectrum from overdrying to overwetting acid-conditioned dentin in water-free, acetone-based, single-bottle primer/adhesives. Dent materials 1996;12:236-244.

5. Prati.C, Chersoni.S, Pashley D.H. Effect of removal of surface collagen fibrilson resin-dentin bonding. Dent materials 1999; 15:323-331.

6. Paulette Spencer, James.R. Swafford. Unprotected protein at dentin-adhesive interface. Quintessence International 1999; 30:501-507.

7. Wakabayashi.Y, Kondou.Y, Suzuki.K, Yatani. H, Yamashita. A. Effect ofdissolution of collagen on adhesion to dentin. Int. J. Prosthodontics 1994;7:302-306.

TABLE V Range and 95% Confidence Interval of SBS in Group I/II/III/IV

Group Range 95% confidence Interval

Minimum Maximum Low High

I. 9.71 16.97 11.62 13.76

II 15.29 27.54 19.32 23.56

III. 22.48 25.16 22.89 23.71

IV. 15.44 24.67 18.93 21.87

Vijay Mathai


33

Discolouration of pulpless or endodontically treatedteeth is an important concern for both patient and dentistand therefore bleaching of discoloured teeth is a significantphase of endodontic therapy. Bleaching of nonvital teeth is aconservative modality of esthetic treatment for discolouredteeth. Two basic techniques that have been used are thethermocatalytic and walking bleach techniques. Bleachingof nonvital teeth with hydrogen peroxide [H

2O

2] is

occasionally associated with external cervical rootresorption [1]. It has been hypothesized that hydrogenperoxide penetration through patent dentinal tubules intothe periodontal ligament initiates an inflammatory reactionresulting in external cervical root resorption [2]. Anotherhypothesis is that bleaching agents cause dentindenaturation at the cementoenamel junction and thisdenatured dentin may act as a foreign body and besusceptible to resorption [3]. These alterations in the

chemical structure of dentin and cementum by 30% hydrogenperoxide treatment have been verified.

In about 10% of teeth, the enamel and cementum do notmeet and there is no cementoenamel junction. In these teeththere is a zone of the root surface devoid of cementum. Herethe materials could readily diffuse from the pulp chamberand canal into the cervical periodontal ligament. Intraumatized teeth it has been shown that reparativecementum loosely adhers to mechanically exposed dentin.Therefore it is conceivable that these areas of poorly repairedmechanical damage in traumatized teeth may facilitateleakage of bleaching materials into the periodontium.

These resorptive lesions often require complex treatmentand occasionally tooth extraction. Most often cervical rootresorption is reported to occur following thermocatalyticbleaching of nonvital teeth. This bleaching procedure isusually performed by heating an aqueous solution of 30-35% hydrogen peroxide in the pulp chamber with a heatsource for 20-30 minutes. In some reported cases bleachingrelated resorption has occurred when no heat was applied.The purpose of this study is to find out any penetration ofhydrogen peroxide during intracoronal bleaching procedureand if so, how does it vary by time and temperature.

Aim: 1. To find out any penetration of 30% hydrogen peroxide during intracoronal bleaching procedure.

2. How does it vary by time and temperature?

Materials and methods: Root canal treatment was performed in freshly extracted intact, single rooted premolars.

The coronal level of the root canal filling was 3mm short of the CEJ. All surfaces of the teeth were coated with

nail polish except for a circular area of radius 2mm on the proximal aspects of the tooth at the CEJ area.

Samples of teeth were grouped into four main groups, A, B, C and D. Groups B, C and D were again subdivided

into 1, 2, 3 and 4 corresponding to time periods 5, 20, 40 and 60mts. 20µl of 30% hydrogen peroxide were

pipetted into each access cavity and sealed with wax. The teeth were then washed with distilled water, dried

and placed in test tubes containing 1.75ml of bidistilled water and then placed in a dry incubator at tempera-

tures of 24°C, 37°C and 47°C for periods of 5, 20, 40 and 60mts. Quantification of H2O

2 was measured using a

specific assay. Estimation of H2O

2 was done using Colourimetric method.

Result: No H2O

2 penetration was detected after five minutes at any of the temperatures tested. The penetration

increased significantly when the temperature was increased from 24°C to 37°C (P<0.01) or 47°C (P<0.01) and was

also found to be time dependent.

Conclusion: It is better to minimize the use of heat and the duration of the bleaching session.

Key words: hydrogen peroxide penetration, intracoronal bleaching .

Abstract

Detection and quantification of hydrogen peroxide penetrationduring intracoronal bleaching and its variation by time and

temperature —An Invitro Study* K.C. Mariamma, ** Kurien K. George, *** N. O. Varghese

* Reader, Dept. of Conservative Dentistry, Sree Mookambhika

Institute of Dental Sciences, Kulashekaram,

** Former Professor & HOD,Dept.of Conservative

Dentistry,Govt.Dental College,Trivandrum,

*** Principal,Govt.Dental College,Trivandrum.


34

Materials and methodsFreshly extracted intact, single rooted premolars, removed

for orthodontic reasons from young adults were used forthis study. The teeth with out any detectable caries,restorations or fractures were immediately placed in salinesolution, and the soft tissue debris covering the root surfacewas gently removed. Care was taken not to damage theradicular cementum. Teeth without apparent cementumdefects or dentin exposures at the CEJ were included. A totalof one hundred and thirty six teeth were selected for theexperiment, of which six served as control. Root canaltreatment was performed in each tooth which included stepback preparation of root canal followed by an obturationwith lateral condensation technique of gutta-percha and zincoxide sealer.Saline was used as the irrigant.The CEJ referencepoints were either on the buccal or lingual side.Remnants ofgutta-percha and sealer from pulp chamber were removedusing a 28mm round carbide bur, rotated at slow speed.Thiswas followed by thorough rinsing of pulp chamber withbidistilled water. The coronal level of the root canal fillingwas 3mm short of the cementoenamel junction. All surfacesof the teeth was coated with nail polish except for a circulararea of radius 2mm on the mesial and distal aspects of thetooth at the CEJ area, for standardizing the same.

Sample groupingSamples of teeth were grouped into four main groups, A,

B, C and D.Group A - set of ten teeth were tested for any penetration

of 30% hydrogen peroxide at 370c for 20minutes.Test for amount of penetration of 30% hydrogen peroxide.Group B- set of 42 teeth tested at 240C.Group C- set of 42 teeth tested at 370C.Group D- set of 42 teeth tested at 470C.Groups B,C and D were again divided into subgroups

1,2,3 and 4 corresponding to time periods 5,20,40 and60minutes respectively.

Procedure

The sample teeth were incubated for a period of 20minutesat 37°C to simulate body temperature. 20µl of 30% hydrogenperoxide were pipetted into each access cavity of theexperimental teeth and the cavity was sealed with wax. Anadditional two teeth in each group served as controls inwhich 20µl of bidistilled water was used instead of 30%H

2O

2. Coronal seal of wax was tested to reveal no H

2O

2

leakage. The teeth were then washed with distilled water,dried and placed in test tubes containing 1.75ml of bidistilledwater. The test tubes were then placed in a dry incubator attemperatures of 240C, 370C and 470C for periods of 5, 20, 40and 60minutes.

Estimation of hydrogen peroxide

Colourimetric methodAfter the bleaching time periods, aliquots of 0.25ml from

the solution in which the teeth were placed were taken in testtubes containing 0.75ml bidistilled water and were madeupto a volume of 1ml. Quantification of H

2O

2 was measured

using a specific assay. To these samples 2.5ml of 0.5N ferrousammonium sulfate was added. In the presence of H

2O

2, a

ferric iron results and upon the addition of 0.25ml of 0.5Npotassium thiocynate, a ferricthyocynate complex is formedwhich absorbs light at the wavelength of 480nm.The amountof H

2O

2 in the samples tested is determined by comparing

them with a standard curve generated by known amount ofH

2O

2. The reagent's reading served as a negative control while

the reading of pure 30% H2O

2 in 1.75ml of bidistilled water

served as positive control. The statistical analysis was doneusing Wilcoxon matched pairs signed rank test.

ResultsThe results of the study are summarized in table 1 and

shown in figure 1. H2O

2 penetration during intracoronal

bleaching was found in all the sample teeth tested in group

Temp Time Median Interquartile range(°C) (mts) (%) (%)

24 5 020 0.001 0.005-0.00140 0.001 0.001-0.00160 0.0015 0.001-0.0015

37 5 0 0

20 0.0015 0.001-0.00175

40 0.002 0.002-0.002560 0.00275 0.002-0.003

47 5 0 020 0.0015 0.001-0.001540 0.002 0.002-0.0022560 0.003 0.0025-0.003

Figure 1

Table 1: Radicular penetration of 30% hydrogen peroxide

K.C. Mariamma


35

A. The control teeth showed no evidence of H2O

2 penetration.

A correlation for both bleaching time and temperatureand the median H

2O

2 was found. No H

2O

2 penetration was

detected after five minutes at any of the temperatures tested.However, prolonging the bleaching time from five minutes tosixty minutes significantly increased the penetration at eachof the temperatures tested (P<0.01). A rise in the bleachingtemperature also increased the H

2O

2 penetration although

not significantly for all tested time periods. After 20 minutesthere was a significant difference between the teeth bleachedat 240C and those bleached at 370C(P<0.01) or 470C(P<0.01).

DiscussionBleaching of nonvital teeth with H

2O

2 is occasionally

associated with external cervical root resorption. Thisresorption may be arrested or progressive or may result inankylosis. Several authors postulated that bleaching agentssuch as hydrogen peroxide penetrated through the dentinaltubules to initiate an inflammatory reaction which couldcause cervical root resorption. These studies gave onlyindirect evidence as to the leakage capacity of such materialsand did not relate specifically to the presence of bleachingagent in the surrounding medium. This study directlydetermine the penetration of hydrogen peroxide throughdentin and cementum during bleaching and permits thequantification of the amount of hydrogen peroxidepenetrated. Moreover, the effect of bleaching time andtemperature on hydrogen peroxide penetration duringintracornal bleaching was also determined.

Several etiologic mechanisms were proposedassociating bleaching procedures of pulpless teeth withexternal root resorption. After the seepage of hydrogenperoxide and its initial effect on the peridontium, bacteriamay colonize the empty tubules, causing inflammation inthe surrounding tissues as well as progressive rootresorption.The bacteria may originate from the gingivalcrevices or the pulp chamber[4]. To achieve the best aestheticresults from bleaching, the clinician often performs severalprocedures that simultaneously facilitate penetration of theoxidizing agent to the tissues surrounding the root. Theseprocedures include freshening of the dentin tubules,removalof smear layer,the use of acid etchants and the applicationof heat.Temperature increase is reported to enhance dentinpermeability.

The diffusion capacity of different substances such asions, molecules, solutions and drugs through dentin and

cementum is well documented. This capacity depends onvarious factors such as the nature of the penetrating agent,the nature of the dental tissue, the surface area exposed andits location, the remaining dentin thickness, previouslyapplied material, the presence of smear layer, andtemperature[5][6]. The ability of H

2O

2 and other oxygen

radicals to cause cellular and tissue destruction is a knownphenomenon [7]. It was found that H

2O

2 caused irreversible

damage to human fibroblasts [8]. The reason was thatbecause H

2O

2 is a small uncharged molecule it could cross

cell membranes easily. The two general mechanisms by whichH

2O

2 might kill cells are

1) By penetrating the cell and damaging a vital internalcomponent after exhausting the protective mechanisms or

2) By causing a fatal lesion to the external cellmembrane, which is relatively unprotected.

Present study-an evaluation; Hydrogen peroxidepenetration was found in all sample teeth. The variation intooth permeability among the teeth tested could be due tomorphologic and chemical variations and to the differencein the remaining dentin thickness. Recent studies haveindicated the cementum- enamel relationship at the CEJ isdynamic and may vary among different groups of teeth inthe same person and even in the same tooth [9], [10].

In this study, it is found that higher bleaching temperatureincreased the H

2O

2 radicular penetration. When the

temperature was raised from 240C to 370C, it doubled theH

2O

2 radicular penetration. This increase was less significant

when the temperature was raised from 370C to 470C.Interestingly no significant penetration was detected after 5minutes of bleaching time at any of the temperatures tested.But when the time periods were increased penetration alsoincreased. This implied that bleaching time played animportant role in the diffusion of H

2O

2 through the dentin. It

is likely that the expansion of the dentinal tubules is timedependant, being minimal during 5 minutes thus limiting itspermeability to H

2O

2. The exact temperature applied during

thermocatalytic bleaching is often difficult to control. It hasbeen shown that a marked discrepancy may exist betweenthe selected and actual tip temperature of an electricbleaching instrument. Temperature variations are even morelikely to occur when a bleaching lamp or a photoflood lightare used. The use of heat in combination with 30% H

2O

2 has

been suggested as a cause for the initiation of post bleachingroot resorption.

All teeth showed a certain permeability to 30%hydrogen

Detection and quantification of hydrogen peroxide penetration during intracoronal

bleaching and its variation by time and temperature


36

peroxide which could reach upto 82% of the total volumeapplied[11],[12]. No significant difference in the radicularleakage of bleaching agents was observed between teethwith and without IRM bases when obturated with guttapercha and sealer[13]. Cervical root resorption followingbleaching of endodontically treated teeth were studied anddetermined that resorption defects were due to heatapplication with 30% hydrogen peroxide. 2mm Cavit wassufficient to significantly reduce linear leakage and dentinalpenetration [14]. It is recommended that a protective base tobe placed at the CEJ level before intracoronal bleaching toprevent possible hydrogen peroxide hazard.It was alsosuggested that catalase be used as adjunct followingintracoronal bleaching of non vital teeth to effectivelyeliminate the residual hydrogen peroxide from the pulpchamber and from the surrounding periodontaltissues[15].Teeth with a gap between cementum and enamelshowed higher values of penetration when compared withteeth with cementum overlap or edge to edge contact of thetwo tissues [16]. It is also demonstrated that H

2O

2 or heat

alone causes less tissue damage than their combined use.Therefore it is recommended to minimize the use of heat andthe duration of the bleaching sessions. Although thecumulative effect of short consecutive bleaching periods isnot known it may seem to be good clinical practice not toexceed 5 minutes bleaching periods. Also, whenthermocatalytic bleaching is carried out, it may appear thatit should be performed at intervals, allowing the tooth tocool, rather than for a long continuous period.

ConclusionIn this study it was found that there is penetration of

H2O

2 during intracoronal bleaching procedure. This

penetration was absent for 5 minutes of bleaching periodsat any of the temperatures tested. The penetration increasedsignificantly when the temperature was increased from 240Cto 370C. Further increase of temperature to 470C did notincrease penetration significantly. The penetration was foundto be time dependant. The penetration increased significantlywhen the bleaching period was increased from 5minutes to20minutes, 40minutes and 60minutes.

It is better to minimize the use of heat and the duration of

the bleaching session. Although cumulative effect of shortconsecutive periods is not known, it may be good clinicalpractice not to exceed 5minutes of bleaching periods.

References1. Madison S, Walton R. Cervical root resorption following bleaching endodontically

treated teeth J.Endodon. 1990; 16:570-4.

2. Harrington GW, Natkin E. External resorption associated with bleaching pulpless

teeth J. endodon. 1979; 5:344-8.

3. LadoEA, Stanley HR, Weisman MI. Cervical resorption in bleached teeth Oral

Surg. 1983; 55: 78-80.

4. Cvek M,Lindvall AM: External root resorption following bleaching of pulpless

teeth with oxygen peroxide Endod Dent Traumatol 1985; 1: 56-60.

5. Pashley DH, Livingston MJ: Effect of molecular size on permeability, coefficients

in human dentin. Arch. Oral Biol. 1978; 23: 319-5.

6. Pashley DH, Thomson SM, Stewart FP: Dentin permeability, effects of

temperature on hydrautic conductance. J. Dent Res. 1983; 62: 956-9

7. Halliwell B, Gre Heridge JMC: Oxygen toxicity, Oxygen radicals, transaction

metals and disease. Biochem. J. 1989; 219: 1-14.

8. Simon RH, Scoggin CH, Patterson D: Hydrogen peroxide causes the fatal injury

to human fibroblasts exposed to oxygen radicals. J. Biol. Chem. 1981; 256:

7181- 6.

9. Muller CJF, Van Wyk CW: The amelocemental junction. J. Dent. Assoc. S Afr.

1984; 39: 799-803.

10. Schroeder HE, Scherele WF: Cementoenamel junction- revisited. J. Periodont.

Res. 1988; 23: 53-9.

11. Ilan Rostein, Yarom Torek, Lewinstein I: Effect of bleaching time and

temperature on the radicular penetration of hydrogen peroxide. Endod. Dent.

Traumatol.1991; 7:196-198.

12. Ilan Rostein: In vitro determination and quantification of 30% hydrogen peroxide

penetration through dentin and cementum during bleaching. Oral Surg. Oral

Med. Oral Pathol. 1991; 72: 602-6.

13. Alex A.De Peralta,Harry N.Joyner,John O,Burgess,Richard d.Davis:Apical

leakage of bleaching agents through an intermediate dental base material.

General dentistry Nov-Dec1991.

14. J.Smith,J.Cunningham,Montgomery:Cervical canal leakage after internal

bleaching procedures. J. Endodont. 1992; 18: 476-481

15. Ilan Rostein;Role of catalase in the elimination of residual hydrogen peroxide

following tooth bleaching J.Endodont.1993;19:567-569.

16. Kovlaouzidou,Lambrianidis:Role of cementoenamel junction on the radicular

penetration of 30% hydrogen peroxide during intracoronal bleaching in

vitro.J.Endod.Dent.Traumatol.1996;12:146-150.

17. Ilan Rostein, CD: Role of catalase in the elimination of residual hydrogen peroxide

following tooth bleaching J. Endodont. 1993; 19: 567-569.

18. David R. Steiner and John D: A method to determine the location and shape of

an intracoronal bleach barrier. J. Endodont. 1994; 20: 304-306.

K.C. Mariamma


37

Introduction

Restoration of endodontically treated teeth is a routineclinical procedure in restorative dentistry. Endodonticallytreated teeth exhibit a higher risk of fracture than the vitalteeth. Therefore, restorations for endodontically treated teethare designed to protect the remaining tooth structure fromfracture. Factors that may predispose to fracture ofendodontically treated teeth have been identified as changesin the bio mechanical properties of dentin, due to the actionof irrigants, medicaments used or root canal filling materialsas well as the loss of structural integrity because of cariesor access cavity preparations(1,2,3). Furthermore, pulplessteeth present alteration of moisture content of the remainingtooth structure. The cumulative interaction of these factorscan influence the mechanical properties of endodonticallytreated teeth. Post and core systems are frequently used to

restore endodontically treated teeth with extensive loss oftooth structure. But, insertion of a physiochemicallyheterogeneous post with a high elastic modulus (E) may createstress concentrations at the dentin post interface, whichmay result in root fracture(4,5). In an effort to improvefracture resistance of endodontically treated teeth restoredwith post-and-core system, research has been focused onpost materials, post designs, luting agents and ferruleeffect(5,6,7).

Fibre Reinforced Composite (FRC) posts have beenintroduced as an alternative to conventional materials, as

Aims & Objectives: 1. To determine the push out bond strength of Variolink II – a dual polymerizing resin cement

used with a fifth generation bonding agent- Excite DSC. 2. To determine the push out bond strength of Panavia

21 – an auto polymerizing resin cement used with a sixth generation bonding agent-E D Primer. 3. To determine

the push out bond strength of Breeze – a dual polymerizing self adhesive resin cement. 4. To compare the bond

strengths of the three resin cements -Variolink II, Panavia 21 and Breeze self adhesive resin cement.

Materials & Methods: In the present study, thirty single rooted lower premolars extracted for orthodontic pur-

poses were decoronated and obturated, and a uniform post space of 6 mm was created in each teeth. Teeth

were mounted on self cure acrylic. After cutting of apical 3-5 mm of teeth, FRC posts were luted using Variolink

II, Panavia 21 and Breeze. The teeth were divided into three groups of ten each depending on the resin cement

used.

In Group A, the posts were luted with Variolink II, in Group B the posts were luted with Panavia 21 & in Group

C, the posts were luted with Breeze self adhesive resin cement. The push out bond strength values for each

groups were evaluated and compared.

Results: In this study, it was found that the mean push out bond strength value for the resin cement Variolink

II was 12.089 MPa, that for Panavia 21 was 6.793 MPa, and that for Breeze self adhesive resin cement was 8.209

MPa. Comparison of the bond strength values showed statistically significant difference between the three

resin cements.

Conclusions: Within the limitations of this study, it can be concluded that 1) Dual cure resin cement used with

fifth generation dual cure bonding agent is most compatible with a light transmitting FRC posts for post

endodontic restorations. 2) Self adhesive resins can be used for their simplified technique of use, but may

not provide bond strengths similar to those used with a fifth generation bonding agent. 3) The use of a self

cure resin cement, along with a self etch primer may not provide the sufficient bond strength values for post

retention in post endodontic restorations.

Key Words: FRC Posts, Resin Cements, Bonding Agents, Polymerization Modes.

Abstract

A comparative evaluation of the bond strengths of three differentresin cements on root dentin and endodontic posts

* Eva.C.Das, ** Jolly Mary Varughese, ** N O Varghese

* Senior Lecturer, Dept. of Conservative Dentistry and

Endodontics, Sree Mookambika Institute of Dental Sciences,

Kulasekaram, K K District,

** Principal, Govt. Dental College, Kozhikode,

***Principal, Govt. Dental College, Thiruvananthapuram.


38

their biomechanical properties have been reported to beclose to that of dentin. Clinical prospective and retrospectivestudies have given encouraging results(8). The developmentof materials capable of bonding to tooth structure hascreated the potential for rehabilitating compromisedendodontically treated teeth. Two factors that may influencethe quality of a bond are the microstructure of the dentinsubstrate and the type of adhesive system used(9). Sincebonding agent effectiveness is usually evaluated on coronalsubstrates, available knowledge for judging the effectivenessof bonds to root dentin is insufficient. Type of resin cementsalso play a key role in the adhesion of FRC posts to rootdentin. Various resin cements are available which can beused along with a total etch system, self etch system, or areself adhesive resins without etching, priming or bonding,but the strength parameters will be different. Also there aredual polymerized and auto polymerized resin cements.

The bonding effectiveness between dentin, bondingagents, resin luting cements and posts can be evaluated bymicroscopic analysis, by microleakage tests and by bondstrength tests (10, 11, 12). Push out tests is usually used forthe bond strength analysis of endodontic posts (13).

The restoration of an endodontically treated tooth witha Fibre Reinforced Composite (FRC) post luted with resinadhesive cement will depend greatly on the bond strength ofthe resin adhesive system used. This study was conducted toevaluate the bond strengths of three different resin adhesivecements (Variolink II, Panavia 21, and Breeze) with a Fiberreinforced post system (FibreKleer) by a push out bond test.

Materials and MethodsThirty single rooted human permanent teeth (mandibular

first premolars), extracted for orthodontic purposes wereused in the study. The teeth were handled according to theOSHA and CDC standards. The teeth were decoronated at thecementoenamel junction with a slow speed diamond disc.The roots were obturated, and the canals were enlarged tillsize 60 K file. 6 mm of post space were prepared in eachtooth with a No: 3 peezo reamer. The post spaces wereenlarged till a No: 140 K file was just loose in the canal. Theteeth were sectioned 3-5 mm from the apex to obtain a uniform6 mm length of post space in the root canal. The teeth wererinsed thoroughly in distilled water and air dried. The teethwere mounted in self cure acrylic using a circular mold of1.5 cm in diameter.

Thirty parallel sided and serrated glass Fiber ReinforcedComposite Posts (FRC posts - FibreKleer) were luted to theroot canals using three different resin cements. The thirtyteeth were divided into three experimental groups of ten each.

Group A: - The posts were luted using a dual cure resincement and total etch bonding system using variolink II andExcite DSC (Ivoclar Vivadent) following the manufacturer’sinstructions n = 10.

Group B: - The posts were luted with an autopolymerisedresin cement with a self etch no rinse bonding system

supplied by the manufacturer’s - Panavia 21 and E D Primer(Kuraray Japan) n = 10.Group C: - The posts were luted using dual polymerized

self adhesive resin cement (Breeze – Pentron ClinicalTechnologies) without any bonding systems. n = 10.

Before luting, the post surfaces were treated with a silanecoupling agent ((Metabond S – Ivoclar Vivadent) and in groupA and B, with their respective bonding agents, as per themanufacturer’s instructions. In Group C, the post surfaceswere treated with Silane coupling agent alone.

After storing the specimens at room temperaturefor 1 week, each specimen was positioned on the push outjig which was placed on the universal testing machine witha compressive load applied at a crosshead speed of 0.5 mm/min until the post was dislodged.

From the load values, bond strength value was calculatedby the formula:

Bond strength = Load

Surface area

Surface area = 2πrh

r = radius of the post = 0.75mmh = length of the post inside the canal = 6mmStatistical analysis was performed and the data were

analyzed using computer software, Statistical Package forSocial Sciences (SPSS) version 10. Analysis of Variance (OneWay ANOVA) was performed as parametric test to compareobservations at different weeks. Duncan’s Multiple Rangetest was performed as Post hoc comparisons.

ResultsFrom the statistical analysis it was found that there was

significant difference between the three study groups in thepush out bond strengths. (Table 1)

Group A exhibited the maximum mean push out bondstrength value which was significantly higher than the valuesobtained for Group B and Group C.

Between Group B and Group C, Group C showedsignificantly higher mean push out bond strength value thanGroup B.

From the values obtained, the three study groups can bearranged in the descending order of bond strengths as:

Group A > Group C> Group BThat is : Variolink ll > Breeze self adhesive resin cement

> Panavia 21.

Discussion

The structural rehabilitation of a pulp less teeth iscritically important to a successful restorative outcomefollowing endodontic therapy. A post and core is oftenindicated for the retention and reinforcement of the finalrestoration. The clinical situation is significantly morechallenging if the root has extensive structural damage orexhibits immature root development (13). A number ofguidelines have been suggested, for restoring endodonticallytreated teeth and they are supported by research findings,

Eva.C.Das


39

literature reviews and retrospective clinical studies.Traditionally, two types of post and core systems are

there, with different design characteristics. In the first system,there is the cast post and the core that closely reproducesthe morphology of the root canal space. (The custom castpost and core.)

In the second system, the post is prefabricated to providea standardized length and cross section. The retention andresistance to displacement under masticatory loads of theprefabricated posts depends on a combination of canalpreparation, luting agents and surface configurations(14,15).

The major disadvantages with the use of metallic prefabricated posts were their rigidity, which will lead tounfavorable fractures during their clinical course. Non rigidposts are biocompatible, and are composed of Glass, Quartz,or Carbon fibres embedded in a resin matrix. They aredesigned to have physical properties similar to that of dentinthan the rigid posts. In structurally sound teeth, non rigidposts flex with the tooth under functional forces, thusreducing the transfer of forces to the root, reducing the riskof root fracture.

The major breakthrough in non metallic posts came withthe application of carbon fibre reinforcement technology tomake carbon fibre reinforced endodontic posts(16,17). Thecarbon fibre material is structurally anisotropic and themodulus of elasticity would be different if the posts are testedat different angles. Carbon fibre posts exhibited greaterrigidity in earlier studies and so smaller diameter postscould be used. Carbon fibre posts have a Young’ s modulusapproximating that of natural teeth, which results indecreased stress concentrations and therefore an increasedlongevity of the restorations(18).

One major disadvantage of carbon fibre reinforced postswas that it is black in color and is not compatible with allceramic restorations. This lead to the introduction ofaesthetic posts like Quartz coated carbon fibre reinforcedcomposite posts, Quartz fibre reinforced composite posts,and Glass fibre reinforced composite posts, which are moretranslucent and more aesthetic (19). The Glass fibrereinforced composite posts are composed of unidirectionalglass fibres embedded in a resin matrix that strengthen theposts without compromising the modulus of elasticity.

The presence of unidirectional glass fibres embedded inthe resin matrix impart on the posts, the ability to transmitlight through the glass fibre reinforced composite posts, tothe entire length of the post. This feature makes the glassfibre reinforced composite post compatible with the dualcured resin cements, allowing near complete polymerizationof the resin cement in the entire root length during lightapplication for polymerization.

Adhesive resin cements were later developed, and theuse of a modern dentin bonding agent with a comprehensiveadhesive system appeared to become mandatory to improvedentin adhesion(20,21). Thus the use of dentin bondingagents in combination with resin adhesive cements and theuse of fiber posts were proposed in order to reduce stresscreated by post cementation (22).

Adhesive resin cements are now available in Light cure,Dual cure, or Auto cure (Self cure) formulations, and theirselection is based on their intended use (23).

Light cure cements offer the clinical advantages ofextended working time, setting on demand, and improvedcolor stability. But they can be used only in situations suchas cementing veneers or shallow inlays where the thicknessand color of the restoration does not affect the ability of thecuring light to polymerize the luting cement(24).

Dual cure resin cements are indicated when deliveringrestorations where material opacity may inhibit sufficientlight energy from being transmitted to the cement. Here lightenergy reaching the resin cement may be sufficient enoughto begin the polymerization process, but an autopolymerizingcatalyst is needed to ensure maximum cure. Here the autocure system will not be sufficient to achieve maximum cementhardening (25). Variolink II has similar degree of conversionwhen light cured or dual cured, but degree of conversion(DC) was lower when they were allowed to self cure alone(26).

Auto cured resin cements are slower in attaining completestrength than light cured resin cements, but they are superiorto zinc – phosphate cements in luting metallic crowns andposts (27). These can be useful for metallic or non lighttransmitting posts like carbon fibre reinforced compositeposts.

Resin cements bond to the root dentin and to most of thepost materials. Bonding to dentin inside the root canal ismore complex than to coronal dentin. This is particularlyimportant because of the configuration factor or C-factorwhich is the ratio of bonded to unbonded resin surfaces thatare often used as a quantitative measure of the geometry ofthe canal preparation for bonding. The higher the C-factorthe greater the stress from polymerization contraction. Thebest situation is C = 1, but when endodontic posts are cementedinside the root canals, the C-factor may exceed 200(28).

Most of the glass fibre reinforced composite posts cantransmit curing light to the internal area of the root, whichallows the use of dual cure resin cements. The amount oflight transmitted varies significantly among fibre posts from< 0.1mW to >2mW. Light activated resin cements rely on the

Mean bond strength (MPa) values in different groups

Group Mean* + SD F value P value

Variolink ll 12.089c 3.475

Panavia 21 6.793a 1.978 12.812 < 0.001

Breeze 8.209b 1.529

* a, b, c – Means with same superscript do not differ each other(Duncan’s Multiple Range Test)

Table 1

A comparative evaluation of the bond strengths of three different resin cements on root

dentine and endodontic posts


40

Eva.C.Das

translucent posts to transmit curing light to the depths ofthe canal. However light intensity decreases rapidly as thedistance from the light source increases and it may beinsufficient for complete curing of light cure resin cement atthe apical third. Because of this reason, the resin cementsused in this study are either dual cured or self cured.

The posts used in the study are glass fibre reinforcedcomposite posts with unidirectional glass fibres arrangedparallel to the long axis of the posts, so that it is capable oftransmitting light till the apex. Therefore it is compatiblewith the dual cure resin cements used. The posts used in thestudy are parallel so as to facilitate the minimal dentinremoval during post space preparation. The posts areserrated to aid in added mechanical retention with the resincement. The diameter of the posts is 1.5 mm uniformly. Thishelps to calculate the area of the bonded surface more easilythan when using tapered posts.

The specimens where prepared so as to have a uniformpost length of 6 mm within the prepared post space. No thinslice preparation was done as this could reduce the bondstrength during the grinding process. This was done so tosimulate the larger length of the post inside the root canalclinically.

In the present study, the highest bond strength valueswere obtained for Group A that is a dual cure resin cement(Variolink II) used with a dual cure bonding agent (ExciteDSC) along with a two step etch, rinse and bond technique(Total Etch System – fifth generation bonding agent). The micromechanical retention to tooth structure occurs when thedentin bonding agent completely infiltrates demineralizeddentin surfaces and creates a Resin Dentin InterdiffusionZone (RDIZ) or resin reinforced layer. Resin tags resultingfrom adhesive penetration into dentinal tubules have beenreported as an important factor in the adhesive-dentin bond,contributing about 30% to the total bond strength PreviousSEM investigations demonstrated that the mechanism foradhesive bonding to root dentin is based on resin tagformation (29). Previous studies have also shown that theRDIZ of a single bottle bonding agent demonstrated a thickhybrid layer 4-5 micro meter (30). This along with the factthat Variolink ll had a similar degree of conversion whenlight cured or dual cured can explain the higher bond strengthof this resin cement. Light activation increases thepolymerization potential of the resin cement resulting inmore complete polymerization, thus increasing the bondstrength.

It has been demonstrated from the previous studies thatthe bond strength depends on the hybrid layer mechanicalproperties rather than the layer thickness. A hybrid layer isa result of resin monomer penetration into the exposedcollagen network on a conditioned dentin surface. It isgenerally approved that the smear layer that forms on grounddentin surfaces should be removed or altered with an acidicconditioner to obtain good adhesion between thedemineralized dentin substrate and an applied bonding

system. The major concern with self – etching primers is

their efficacy in infiltrating thick smear layers such as those

produced during post space preparation. However, it has

been found that self etching primers can penetrate beyond

the surface in the presence of a thick smear layer formation,

incorporating it into a hybridized smear layer. A very thin

true hybrid layer may also form underneath this layer.

The RDIZ for self etch primers were found to be in the

range of 1-2 micrometers (30). In the present study, the self

cure resin cement Panavia 21 used with self etching primer

(ED Primer), showed the lowest bond strength values. This is

in accordance with the literature which emphasizes that, the

self etch adhesive systems have low bond strengths when

used with self cure resins.

There are two aspects to this problem. The first one is

that the self cured resin cements contain tertiary amines in

the catalyst, which initiate the polymerization reaction and

they have a high pH value. Loss of strength may occur, when

they are used along with an acidic primer that is not rinsed

off after application, as in the self etch primer, and the

residual acid can partially neutralize the high pH amines in

the self cure resins, leading to less effective polymerization

process. The second problem is the self etching adhesives

are highly hydrophilic, and will behave as semi permeable

membranes. This moisture contamination reduces bond

strengths, and facilitates leaching out of soluble components.

This explains the lowest bond strength values for group B.

In Group C, the self adhesive resin cement group, (Breeze

Pentron Clinical Technologies.), the bond strength values

were significantly less than that of Variolink II but greater

than that for the Group B (Panavia 21) and difference is

statistically significant. The higher strength values of Group

C than that of Group B can be attributed to the dual

polymerization capacity of the cement and the presence of

acidic monomers for dentin conditioning and components

such as hydroxyl ethyl methacrylate for priming and bonding.

But, the reduced bond strength values to that of Group A can

be attributed to the lack of a bonding agent and absence of

smear layer removal. In this case the resistance to

dislocation can be attributed mainly to mechanical retention

by frictional forces (31).

ConclusionsWithin the limitations of this study, it can be concluded

that1) Dual cure resin cement used with fifth generation

dual cure bonding agent is most compatible with a lighttransmitting FRC posts for post endodontic restorations.

2) Self adhesive resins can be used for their simplifiedtechnique of use, but may not provide bond strengths similarto those used with a fifth generation bonding agent.

3) The use of a self cure resin cement, along with aself etch primer may not provide the sufficient bond strengthvalues for post retention in post endodontic restorations.


41

References1. R. Sorrentino, R. Aversa, V. Ferro, T. Auriemma, F. Zarone, M.Ferrari,. Apicella

A. Three dimensional finite element analysis of strain and stress distribution inendodontically treated maxillary central incisors restored with different post,core, and crown materials. Dent. Mat 2007 23:983-93.

2. Carlos Jose Soares, Santana FR.,.Silva NR, Pereira JC, Pereira CF. Influence ofthe Endodontic Treatment on Mechanical properties of root dentin. J.Endod.2007 33:603-6.

3. Doyon GE, Dunsha T, Von Fraunhofer JA. Fracture resistance of human rootdentin exposed to intracanal calcium hydroxide. J. Endod. 2005 31: 385-7.

4. Pegoretti A, Fambri.L, Zappini G, Biancheti .M. Finite element analysis of aglass fibre reinforced composite Endodontic post. Biomaterials 2002 23:2667-82.

5. Plotino G,. Grande NM, Bedini R,. Pameijer CH, Somma F. Flexural propertiesof Endodontic posts and human root dentin. Dent Mat 2007 23:1129-35.

6. Martinez Insua A, Da silva .L, Rilo B, Santana M. Comparison of the fractureresistance of pulpless teeth restored with a cast post and core or carbon fibrepost with composite core. J. Prosthetic Dent. 1998 80; 527-37.

7. Pierrisnad L, Bobin F, Renault P, Barquine M. Corono radicular reconstruction ofpulpless teeth: a mechanical study using finite element analysis. J. ProstheticDent. 2002:88: 442-8.

8. Mannocci F, Sheriff M, Watson T.F. Three point bending tests of fibre posts. J.Endod. 2001 27:758-61.

9. Ferrari M, Mannocci F, Vichi A, Cagidiaco MC, Mjor.A . Bonding to root canal:structural characteristics of the substrate. Am. J. Dentistry 2000 13:255-60.

10. Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques onbonding to root canal walls - an SEM investigation. Dent. Mat 2001 17:422-9.

11. Mannocci F, Innocenti M, Ferrari M, Watson T.F. Confocal and Scanning ElectronMicroscopic study of teeth restored with fiber posts, metal posts and compositeresins J. Endod. 1999 25: 789-94.

12. Mannocci F, Ferrari M, Watson T.F. Microleakage of endodontically treatedteeth restored with fibre posts and composite cores after cyclic loading; a Confocalmicroscopic study. J.Prosthetic.Dent 2001 55:284-89.

13. W.A. Saupe, AH Gluskin, R.A. Radka. A comparative study of fracture resistancebetween morphologic dowel and cores and a resin reinforced dowel systemsin the intra radicular restoration of structurally compromised roots.Quintessence international Vol. 27. No:7, 1996,483-91.

14. Duret B, Reynaud M, Duret F. New concept of coronoradicular reconstruction:the composi post. Chir. Dent .Fr. 1990;60:131-141.

15. D.G Purton, J. A. Payne. Comparison of carbon fiber and stainless steel rootcanal posts. Quintessence international Vol.27. No.2, 1996; 93-97

16. G.F Sidoli, P.A King, J. Setchall. An in vitro evaluation of a carbon fiber basedpost and core system. J. Prosthet. Dent. 1997;78:5-9

17. G. Bateman, D.N.J Ricketts & W.B Saunders. Fiber based post systems: a review.British Dental Journal Vol. 195 No:1; (July 2003):43-48.

18. D. Dietschi, M. Romelli, A. Goretti. Adaptation of adhesive posts and cores todentin after fatigue testing. Int. J. Prosthodont. 1997;10:498-507

19. H.S. Chana, R.J. Ibbeston, G. J. Pearson, A. Elder. The influence of cementthickness on the tensile strength of two resin cements Int. J Prosthodont 1997;10:340-344

20. M. Ferrari, F.Mannoci. A ‘one bottle’ adhesive system for bonding a fiber postinto a root canal: an SEM evaluation of the post resin interface. Int. EndodonticJournal 2000;33:397-400

21. Platt J.A, Resin cements into the 21st century compendium of continuededucation in dentistry. 1999; 20:1173-8

22. Breeding L.C, Dixon D.C, Caughman W.F. The curing potential of light activatedcomposite resin luting agents J. Prosthet. Dent. 1997 65:512-18

23. Caughman W.F, Daniel M.E, Chan E.N. Curing potential of dual pol. Resin cementsin sinus din situation J.Prosthet.Dent. 2001 85:429-84

24. T.A Degoraro, N.R.F.A Dasilva. R.M Carvalo. Cements for use in aestheticdentistry DCNA 51 2007 453-71

25. Uy.J.N, Lian J.N, Nichole J.I. Load fatigue performance of gold crowns lutedwith resin cements t.Dent. 2006 95(4):315-22

26. A Mallmann, L.B Jacques, L.F. Valandro, A. Munch. Microtensile bond strengthof photo activated and auto polymerized adhesive systems to root dentin usingtranslucent and opaque fiber reinforced composite posts J. Prosthet. Dent.2007; 97:165-72.

27. Christensen.G Posts: a shift away from metal? Clin. Res. Associates Newsletter.28:1, 2004.

28. Goracci C, Sadek F.T, Fabianelli A, Tay F.R, Ferrari M. Evaluation of the adhesionof fiber posts to intra radicular dentin. Oper. Dent. 2005 30:627-35.

29. R.S. Shwartz. Adhesive Dentistry and Endodontics. Part 2: Bonding in rootcanal system. The promise and problems. A Review. J. Endod. 2006 Vol. 32,No:12; 1125-34

30. Akgungor G, Akkayan B. Influence of dentin bonding agents and polymerizationmodes on the bond strength between translucent fiber posts and three dentinregions within a post space. J. Prosthet. Dent. 2006 95; 368-78.

31. Goracci C, Fabianelli A, Sadek FT, Pappachini F, Tay FR, Ferrari M.Thecontribution of friction to the Dislocation Resistance of Bonded Fiber Posts. J.Endod. 2005 31:8:608-12.

A comparative evaluation of the bond strengths of three different resin cements on root

dentine and endodontic posts


42

Introduction

The primary objective of root canal treatment is the

thorough mechanical and chemical cleansing of the entire

pulp space followed by complete obturation with an inert

filling material.(1) Therefore, it is imperative aberrant

anatomy is identified prior to and during root canal treatment

of teeth for more predictable,symptom free and successful

treatment. With magnification, either by loupes or

microscope, becoming more commonly employed the astute

clinician must be aware of recent literature that states that

the mandibular first molar has a 1–15% chance of a fifth

canal.

This article presents two case reports accompanied by a

review of the literature that shows the unusual anatomy of

the mandibular first molar.

Case report 1

A patient aged 18 was referred by her dentist for

Endodontic treatment of right mandibular first molar.

Clinical examination showed a large carious lesion that had

invaded the pulp. The patient presented with severe pain

and clinical manifestations of acute pulpitis. The tooth

responded to vitality tests. The medical history of the patient

was noncontributory. The involved tooth was tender to

percussion and no periodontal pockets were present.

Radiographs revealed radiolucency involving the pulp and

widening of the periodontal ligament space.(figure1) Root

canal treatment was advised. Under rubber dam isolation

the access cavity was prepared and the chamber irrigated

with 5 % Sodium Hypochlorite (NaOcl). Four root canals

were detected, two mesial and two distal. Exploring the

fissure between the main mesial canals with a sharp

Endodontic explorer (DG 16, Hu Freidy), a middle mesial

canal orifice, which was equidistant from the mesiobuccal

and mesiolingual canal orifices was encountered. A small

pre curved K-file(No.8 Dentsply )was inserted and advanced

through the middle mesial canal orifice till the working length

was reached. Working lengths were estimated using Root ZX

II apex locator(J.Morita, Japan).Three separate root canals

Breaking the Canal Code - The Middle Mesial Canal* Robin Theruvil

* Professor, Dept. Of Conservative Dentistry & Endodontics,

St Gregorios Dental College, Kothamangalam, Ernakulam Dist. Figure 1

Figure2

Figure 3


43

were confirmed with a radiograph(figure 2 ) All canals were

prepared with No: 20 K file and then instrumented with

Protaper Rotary System (Dentsply-Maillefer, Switzerland).All

canals were dried using paper points. A Master cone

radiograph was made (figure 3) and the canals were obturated

using a resin sealer (AH Plus, Dentsply, Germany) and

Protaper Gutta Percha. (figure 4) The patient experienced no

post treatment consequences and was subsequently referred

for appropriate coronal restoration.

Case report 2

A 24 year old male patient was referred to the Department

of Conservative Dentisrty and Endodontics of St Gregorious

Dental College , Kothamangalam with pain in the mandibular

left posterior region for the past 3 weeks. The patient

complained of spontaneous pain on exposure to cold stimuli.

The medical history was non contributory. Clinical

examination revealed a deep carious lesion in relation to

the first mandibular molar on the left side. Radiograph

showed the lesion to extend close to the pulp (figure 5.)After

administering local anesthesia, and rubber dam isolation,

all carious tissue was removed, and an adequate Endodontic

access was made. Clinical examination revealed 5 distinct

orifices-three located mesially (mesiobuccal ,middle mesial

and mesiolingual)and two distally (distobuccal and

distolingual).The canals were explored with a No 15 K file(

Mani,inc Japan)

Working lengths were estimated using an electronic apex

locator (Root ZX II , J Morita. Japan)and confirmed with a

radiograph. The presence of three separate root canals were

confirmed with a radiograph.( figure 6 )All canals were

cleaned and shaped with Protaper system(Dentsply-

Maillefer ,Switzerland) under copious irrigation with 5.25%

Sodium Hypochlorite. The root canals were dried with paper

points. A master cone radiograph (figure 7) was made and

the canals were obturated with Pro taper guttapercha using

Zinc oxide Eugenol sealer (DPI ltd).Post Obturation

radiograph was made The patient experienced no post

operative discomfort.

Discussion

Although all teeth are anatomically complex, the first

lower molars are the first permanent posterior teeth to erupt

and are those that most often suffer from caries, so they are

most likely to require Endodontic treatment. These molars

normally have two roots, one mesial and one distal, and

their usual canal distribution is two in the mesial root and

one or two in the distal root. Nonetheless, other possibilities

exist. The probability of a mandibular first molar having a

fifth canal is 1-15% (2).

Instrumentation is one of the key factors in the success

of Endodontic therapy; therefore, the clinician should be

aware of the incidence of these extra canals in the mandibular

first molar. In a study of 760 mandibular molars, Fabra (3)

found that 20 (2.6%) had three canals in the mesial root. In

13 of these (65%) the third canal joined the mesiobuccal

Figure 4 Figure 5

Figure 6

Breaking the Canal Code - The Middle Mesial Canal


44

canal in the apical third of the root and in 6 (30%) they

converged with the mesiolingual canal, also in the apical

third; the third canal ended as an independent canal in only

1 case. In a clinical evaluation of 145 mandibular first molars

Fabra-Campos (4) found four molars (2.07%) with five canals

– three in the mesial root and two in the distal. In none of

these four cases did the middle mesial canal show an

independent course and foramen, Goel et al.[5] reported that

the mesial root of permanent mandibular first molars

presented two foramina in 60% of the specimens, whereas

6.7% and 3.3% of these molars had three and four foramina

respectively. The occurrence of three independent canals in

the mesial root was reported by Pomeranz et al.(6)and Beatty

and Krell (7) described a mandibular first and second molar

with three independent canals in the mesial root. Martinez-

Berna and Bandanelli(10) showed two cases with six canals.

Pre-operative radiographic analysis is critical for

Endodontics. Multiple angled Periapical views help reveal

the presence of roots and canal systems. However, these

may be of little value in the variations in the mesial root of

mandibular first molars. Buccolingual views, 20° from mesial

and 20° from distal, reveal the basic information on the

tooth’s anatomy and the root canal system that is required

for Endodontic treatment(8). Nance et al.(11 ) showed that

Tuned Aperture Computerized Tomography(TACT) imaging

enabled a significant increase in canal detection as

compared to conventional radiography. Gopikrishna et al

(8) used spiral computerized tomography for the

confirmatory diagnosis of a morphological aberration in

the maxillary first molar.

It has been postulated that secondary dentin apposition

during tooth maturation would form dentinal vertical

partitions inside the root canal cavity, thus creating root

canals. A third root canal may also be created inside the

root canal cavity of mandibular molars by this process. Such

third canals are situated centrally between the two main

root canals, the buccal and lingual root canals. The diameter

of those third middle canals is smaller than that of the other

two.

Summary

Dental clinicians in general perceive that a given tooth

will contain a predetermined number of roots and/or canals.

Careful evaluation of research material has, however, shown

that deviations from the norm in tooth morphology are not

uncommon. This should induce the clinician to accurately

examine the pulp chamber floor to detect possible canal

orifices. This additional canal may be independent with a

separate foramen, or the additional canal may have a

separate foramen and join apically with either the

Figure 7

Prevalence of a third canal in the mesial root of mandibular first molars according to different authors

AUTHORS YEAR NO. OF TEETH METHOD THEE CANALS (%)

Skidmore and Bjorndol 1971 45 in Vitro 0

Pineda and Kuttler 1972 300 in Vitro 0

Vertucci 1974 100 in Vitro 1

Pomeranz 1981 100 in Vitro 12

Martinez-Berna and Badanelli 1983 1418 inVitro 1.5

Fabra-Campos 1985 145 inVitro 2.1

Fabra-Campos 1989 760 inVitro 2.6

Goel 1991 60 inVitro 15

Courtesy: Navarro et al.[9]

Robin Theruvil


45

Breaking the Canal Code - The Middle Mesial Canal - A case report

mesiobuccal or mesiolingual canal. A thorough examination

of the pulp chamber and meticulous instrumentation should

help to increase the chances for successful outcome of

Endodontic therapy.

References1. Vertucci FJ. Root canal anatomy of the human permanent teeth.

Oral Surg Oral Med Oral Pathol.1984 Nov;58(5):589-99.

2. Baugh D, Wallace J. Middle mesial canal of the mandibular first

molar:a case report and literature review. J Endod. 2004

Mar;30(3):185-6

3. Fabra-Campos H. Three canals in the mesial root of mandibular

first permanent molars: a clinical study. Int Endod J. 1989

Jan;22(1):39-43.

4. Fabra-Campos H. Unusual root anatomy of mandibular first

molars. J Endod. 1985 Dec;11(12):568- 72.

5. Goel NK, Gill KS, Taneja JR. Study of root canals configuration in

mandibular first permanent molar. J Indian Soc Pedod Prev Dent.

1991;8:12–4. [PubMed]

6. Pomeranz HH, Eidelman DL, Goldberg MG. Treatment

considerations of the middle mesial canal of mandibular first

and second molars. J Endod. 1981 Dec;7(12):565-8.

7. Beatty RG, Krell K. Mandibular molars with five canals: report of

two cases. J Am Dent Assoc. 1987 Jun;114(6):802-4.

8. Gopikrishna V, Ruben J, Kandaswamy D. Endodontic

management of a maxillary first molar with two palatal roots

and a single fused buccal root diagnosed with spiral

computerized tomography: A case report. Oral Surg Oral Med

Oral pathol Oral Radiol Endod. 2008;105:74–8

9. Navarro LF, Luzi A, Garcia AA, Garcia AH. Third canal in the mesial

root of permanent mandibular first molars: Review of literature

and presentation of 3 clinical reports and 2 in vitro studies. Med

Oral Patol Oral Cir Bucal 2007;12:605-9

10. Martinez-Berna A, Badanelli P. Mandibular first molar with six

root canals. J Endod 1985;8:348-52.

11. Nance R, Tyndall D, Levin LG, Trope M. Identification of root canals

in molars by tuned-aperture computer tomography. Int Endod J.

2000;33:392–6


46

Controversies are in plenty regarding one visit andMultiple Visit Endodontics. From the inception of Endodonticprocedures it was questionable as to the level of anti bacterialeffect provided by single visit Endodontics. Multiple VisitEndodontics had its greatest disadvantage of robbing theclinician as well as the patient valuable and precious timeand monetary loss.

But with the advent of new technologies, materials andmethods single visit Endo is gaining popularity world wide,that too with predictable and acceptable results.

Objective of Endodontic treatment is to remove theinfective micro organisms from the canal system and toprovide a bacteria impermeable seal at the minor diameter.Whether it is achieved in single visit or multiple visits dependson many a factor including the ability of the clinician tohandle various situations.

Why is Single Visit Endodontics (SVE) becoming popular?The answer is1. Economic considerations – both for the clinician and

patient, 2. Saving valuable work time, earnings and travel,3. Elimination of chances of inter appointment flare ups,4. Allows the use of post space immediately for the post andcore fabrication if required

The procedure has its own limitations as well. Flare upswere reported to be very frequent and the studies regardingthe long term success rate of Single Visit Endodontics is stilllacking. The concept followed so far was that in a vital toothif Endodontics has to be done, it can be completed in singlevisit with out much of a flare up or post obturation problems.But in a non vital tooth cleaning and shaping and medicationare also required to kill the micro organisms in the canalsand dentinal tubules. There is no fool proof evidence thatthe medications in between the appointments will kill themicrobes in the canal system. There is not much differencebetween multiple visit Endodontics and Single VisitEndodontics in this aspect.

But there are some conditions which definitely do notwarrant a Single Visit Endodontics e.g.: 1. Acute cellulites’

2. Acute apical abscess requiring drainage3. Tooth with severe pain4. Weeping canalsWhether it is multiple sitting or single sitting one thing is

very important - absolute and thorough shaping and cleaning.Cleaning is one factor without which success is only a dreamand not reality.

Talking about the cleaning and shaping, from the timethe Endodontic treatment was introduced the working length(WL) was considered the prime important factor. But recentconcepts point to another entity which also has to beconsidered with utmost importance which is the workingwidth (WW) or the apical enlargement Working width denotes

Single visit endodontics - A bird’s eye view* K. Ravi Varma

* Retired Deputy Director, Health Services Kerala; Principal,

Professor& H O D, Dept of Conservative & Endodontics,

Jaipur Dental College, Jaipur

the tip size of the last instrument used to the working length.So far importance was given only to the working length, butnow working width also is considered critical. WW is thelast instrument used to WL and it is the same as MAF or MAR.(Master apical file or Master apical rotary). The correct WWcorrelates close to the largest diameter of the original canalsize in the apical 3rd. This principle is applicable both forsingle as well as multiple visit Endodontics. WW should belarge after instrumentation if the apical portion of the canalis large before instrumentation and vice versa in smallercanals. An under sized WW at a correct WL will compromisecleanliness where as oversized WW at correct WL willcompromise root strength. Research has reinforced theconcept that a WW slightly larger than the original canalsize give better results i.e., bigger is better. This concept wasa forlorn fact so far and the WW was a ‘forgotten dimensionin Endodontics’ This concept was not followed for the simplereason that, if canal is to be enlarged, larger instrumentshave to be used, which in turn may produce ledging, zippingor perforation.

"Bigger is Better"means larger instruments at WL cleanbetter than smaller ones. It also means the size of the minordiameter (MD) do not dictate the WW. Slightly coronal to theMD the canal is much larger. So the final apical instrumentsize WW has to be compatible with this larger canaldimension than the minor diameter rotary. Light speed hasbeen designed specifically for this purpose. Light speedinstruments are non tapered, short bladed, with non cuttingpilot – tip and superior flexibility.

A major obstacle in a Single Visit Endodontics is theapprehension of post operative pain, which is legitimate inpatients with less tolerance of the pain perception. So thepatients have to be properly educated regarding the SingleVisit Endodontics. Predicting pain and failure in Endodonticsis difficult, but several investigators concluded that there isno difference between Multiple Visit and Single VisitEndodontics therapy as far as pain is concerned. Thepopularity of Single Visit Endodontics can be credited to thefavourable reports which showed no difference in thecomplications or the successes rates of Single VisitEndodontics compared to Multiple Visit Endodontics

ConclusionSince last 25 yrs – research and developments in materials

and methods have shown that the root canals are muchlarger than once thought of. Yet the popular concept thatinstrumenting to size 20, or 25 in most molar canals issufficient, does not have scientific support. Lots of literaturehas been published to highlight the fact that the number ofintra canal bacteria is reduced if the apical area is enlarged.

New technology has provided the Endodontist with anarray of better instruments and materials. Rotary systemhas revolutionised the canal preparation system to such anextent that the concept of Single Visit Endodontics is gainingroot in the speciality of Endodontics in a very impressiveand successful manner

Master speak


47

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B. Abstract for Original Scientific Articles should be nomore than 250 words giving details of what wasdone using the following structure:

• Aim: Give a clear statement of the main aim of the studyand the main hypothesis tested, if any.

• Methodology: Describe the methods adopted including,as appropriate, the design of the study, the setting, entryrequirements for subjects, use of materials, outcomemeasures and statistical tests.

• Results: Give the main results of the study, including theoutcome of any statistical analysis.

• Conclusions: State the primary conclusions of the studyand their implications.

This section often is written last by many authors since

they can draw on the rest of the manuscript. Write theabstract in past tense since the study has been completed.Three to ten keywords should be listed below the abstract.

C. Main Text of Original Scientific Article should includeIntroduction, Materials and Methods, Results,Discussion, Conclusion and References.

Introduction: The introduction should briefly review thepertinent literature in order to identify the gap inknowledge that the study is intended to address. Thepurpose of the study, the tested hypothesis and its scopeshould be described.

Material and Methods: The objective of the methods sectionis to permit other investigators to study and replicateyour experiments. The three components to this portionare the experimental design, the methods employed, andthe statistical tests used to analyze the results. The vastmajority of manuscripts should cite prior studies usingsimilar methods and succinctly describe the particularaspects used in the present study. If the study utilized acommercial product, the manuscript should state that theyeither followed manufacturer ’s protocol or specify anychanges made to the protocol. Studies on humans shouldconform to the Helsinki Declaration of 1975 and statethat the institutional IRB approved the protocol and thatinformed consent was obtained. Studies involvinganimals should state that the institutional animal careand use committee approved the protocol. The statisticalanalysis section should describe which tests were usedto analyze which dependent measures; p-values shouldbe specified. The soft ware used to analyse the data hasto be mentioned. Additional details may includerandomization scheme, stratification (if any), poweranalysis, drop-outs from clinical trials, etc.

Results: Only experimental results are appropriate in thissection (i.e., neither methods nor conclusions should bein this section). Include only those data that are criticalfor the study. Do not include all available data withoutjustification; any repetitive findings will be rejected frompublication. All F igs./Charts/Tables should be describedin their order of numbering with a brief description of themajor findings.

Discussion: may usefully start with a brief summary of themajor findings, but repetition of parts of the abstract orof the results section should be avoided. The Discussionsection should progress with a review of the methodologybefore discussing the results in light of previous work inthe field. The Discussion should end with a briefconclusion and a comment on the potential clinicalrelevance of the findings. Statements and interpretationof the data should be appropriately supported by originalreferences.

Conclusion: should contain a summary of the findings.

References: The reference style follows Index Medicus. Eg-Mc Cracken MS, Haywood VB. Demineralization effects of10 percent carbamide peroxide. J Dent 1996; 24:395-8. Thereferences are placed in parentheses at the end of asentence or at the end of a clause that requires a literaturecitation. Do not use superscript for references. Originalreports are limited to 35 references. There are no limitsin the number of references for review articles.

Guidelines to Authors


48

ROUTE MAP FOR SUBMISSION TO JCAESOK

Manuscripts submitted for publication must be submittedsolely to the JCAESOK and not published elsewhere.

Manuscript Submission: The prepared article and the coverletter should be sent as separate files [email protected]

Preparation of Manuscript: Manuscripts that do not adhereto the instructions will be returned to the correspondingauthor for technical revision before undergoing peerreview.

Title Page: The title page must be submitted as a separatefile. Include on the title page: a. Complete manuscripttitle; b. Authors’ full names, highest academic degreesand affiliations; c. Name and address for correspondence,including fax number, telephone number and e-mai laddress; (d) address for reprints if different from that ofcorresponding author; and d. All sources of support,including pharmaceutical and industry support that requireacknowledgment.

Abstract: The abstract and text must be submitted as aseparate file. Limit the abstract to 250 words. It must befactual and comprehensive. Limit the use of abbreviationsand acronyms, and avoid general statements (e.g., “thesignificance of the results is discussed”). List three tofive keywords or phrases.

Text: Organize the manuscript into six main headings:Introduction, Materials and Methods, Results, Discussion,Conclusion and References. Define abbreviations at firstmention in text and in each table and figure. If a brandname is cited, supply the manufacturer ’s name andaddress (city and state/country). References follow thestyle of Index Medicus. They must be keyed to the text andnumbered consecutively in the order of appearance.References should be placed inside parentheses at theend of a sentence or a clause, and not placed assuperscripts.

Figures: Art should be created/scanned and saved andsubmitted as either a TIFF (tagged image file format), anEPS (Encapsulated PostScript) file or a PPT (PowerPoint)file. Line art must have a resolution of at least 1200 dpi(dots per inch); all scanned images including electronicphotographs/radiographs, CT scans, etc., must have aresolution of at least 300 dpi. If fonts are used in theartwork, they must be converted to paths or outlines, orthey must be embedded in the files. Publication of colorillustrations is possible and, at the editor’s discretion.

Tables: Tables should be double-spaced with a single boldruling beneath the column titles. Units of measurementsmust be included in the column title.

Figures: All figures should be planned to fit within either1 column width (8.0 cm), 1.5 column widths (13.0 cm) or 2column widths (17.0 cm), and must be suitable forphotocopy reproduction from the printed version of themanuscript. Lettering on figures should be in a clear.Figures should be on a white background, and shouldavoid excessive boxing, and unnecessary colour, shading.

The line spacing should be wide enough to remain clearon reduction to the minimum acceptable printed size.

Figure legends: Figure legends should begin with a brieftitle for the whole figure and continue with a shortdescription of each panel and the symbols used; theyshould not contain any details of methods. Hard copiesof all figures and tables are required when the manuscriptis ready for publication. These will be requested by theEditor when required. Each Figure copy should be markedon the reverse with the figure number and thecorresponding author’s name.

Cover Letter: A cover letter, containing signatures of allauthors and the following information, must be scannedand submitted along with the article word document.a. The manuscript title, name and address (including e-mail) of one author designated as the correspondingauthor. This author will be responsible for editing proofsand ordering reprints when applicable. b. The followingparagraph: “In consideration of the editors of the JCAESOKtaking action in reviewing and editing this submission,the author(s) undersigned hereby transfer, assign orotherwise convey all copyright ownership to the CAESOKin the event that such work is published in that Journal.”c. If the purpose of a paper is to evaluate a commercialproduct, then a separate statement must be included withthe submission, which asserts that the product was usedexactly according to manufacturer ’s instructions. If thiswas not the case, a precise description of any variant usemust be prominently stated in the abstract, methods and,if appropriate, in the title. d. All authors must also signthe following statement, which must accompany themanuscript: “I affirm that I have no financial affiliation(e.g., employment, direct payment, stock holdings,retainers, consultantships, patent licensing arrangementsor honoraria), or involvement with any commercialorganization with direct financial interest in the subjector materials discussed in this manuscript, nor have anysuch arrangements existed in the past three years. Anyother potential conflict of interest is disclosed.” Anyauthor who cannot sign this statement must append aparagraph to the manuscript that fully discloses anyfinancial or other interest that poses a conflict. Thisparagraph should follow the “Discussion” section. e. Ifhuman subjects are used, include the following statement:“ The informed consent of all human subjects whoparticipated in the experimental investigation reportedor described in this manuscript was obtained after thenature of the procedure and possible discomforts andrisks had been fully explained.” If animals are used, astatement on protocol approval by the institutional animalcare and use committee must be included.

Disclaimer: “The statements, opinions and advertisementsin the JCAESOK are solely those of the individual authors,contributors, editors or advertisers, as indicated. Thosestatements, opinions and advertisements do not effectany endorsement by CAESOK or its agents, authors,contributors, editors or advertisers, or the publisher.Unless otherwise specified, the CAESOK and the publisherdisclaim any and all responsibility or liability for suchmaterial.”

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