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A comparative study of vertical fracture of rootsobturated with new obturating systems - An in vitro study

ABSTRACTIntroduction : The purpose of this invitro study was to evaluate the post obturation fracture resistance of endodontically

treated teeth obturated with new obturating systems such as Realseal system, GuttaFlow obturation system, conventional

lateral compaction technique and Microseal obturation system.

Materials and Methods : Fifty extracted single rooted teeth were selected and sectioned at the CEJ. The root canals

were instrumented using EasyRace files. The teeth were randomly divided into 5 groups of 10 teeth each. Group I

served as negative control and was instrumented and not obturated. The other groups were obturated with new

obturating systems. The specimens were evaluated for vertical fracture resistance using Instron universal testing machine.

Results : According to the study it was found that the Resilon with Realseal displayed higher mean fracture load in

comparison to other experimental groups.

Conclusion : Obturation of roots with a resin based obturation material increased the fracture resistance of root

canal filled tooth to vertical fracture.

Key words : Vertical fracture, obturation, monoblock, Resilon, GuttaFlow, Microseal

Original Research

# Conservative Dentistry and Endodontics, Nepal, ## Dept. of Conservative Dentistry and Endodontics, Manipal University, Manipal College of Dental Sciences,Mangalore

IntroductionThe objectives of root canal treatment are

removal of diseased pulp, shaping and cleaning of

the root canal and three dimensional obturation with

an inert material to obtain a fluid tight seal to

prevent re-infection.1, 2, 3 Vertical root fractures are

complications that are mostly seen in root canal

obturated teeth and often lead to extractions.4

Schilder 5 suggested that the ideal root canal

obturating material should be well adapted along

the entire length of the root canal walls and produce

a homogenous mass. Currently with the application

of adhesive dentistry in endodontics, the present

concept of obturation of the root canal is not just

the three dimensional filling of root canal and

accessory canals, but also the reinforcement of the

root. The ability of gutta percha to reinforce an

endodontically treated root is still controversial.6 It

is suggested that bonding of endodontic adhesive

sealers to root dentin and also to the obturating

material may enhance the fracture resistance of root

filled teeth, so their use has been suggested to

reinforce the root canal walls.7

The concept of sealing and tooth strengthening

by using adhesive root canal obturating materials

is known as monoblock effect.8,9 To achieve this

monoblock effect ,an obturation system was

introduced in 2004, known as Epiphany (Pentron

clinical Technologies.LLC Wallingford CT.USA)

which contained Resilon cones and resin based

sealer. Resilon cones are thermoplastic synthetic

polymer based root canal filling materials and

polymers of polyester. GuttaFlow (Coltène/

Whaledent Inc. 235 Ascot Parkway Cuyahoga Falls,

Vimmi Singh #Neeta Shetty ##Kundabala M. ##

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Ohio 44223 / USA) is a cold flowable root canal

filling paste system. It is said to offer excellent flow,

good adaptability to root canal walls, ease of use,

low setting time within 10 minutes and slight

expansion on setting (0.2%).10 The Microseal system

(Analytic Endodontics ,Glendora,CA 91740) is a

thermomechanical filling technique that uses a

laterally compacted master gutta-percha cone and

placement of gutta-percha to backfill the canal.

Microseal is a recent obturating system for which

the resistance to vertical fracture is not known.

Hence this study was conducted to evaluate

and compare the effect of different obturation

systems on the fracture resistance of endodontically

treated tooth, such as RealSeal obturating system

(SybronEndo,Orange,CA) GuttaFlow system,

conventional lateral compaction technique and

Microseal system.

Materials and Methods :Preparation of the specimens

Fifty freshly extracted single rooted human teeth

were selected & stored in saline solution. The teeth

were sectioned at the cementoenamel junction with

a diamond wheel saw (Mani,Japan) The sectioned

teeth were randomly divided into 5 groups

consisting of 10 teeth each.Access cavities were

prepared using an airotor hand piece and endo-

access bur. (Dentsply Maillefer CH-1338

Ballaigues). The working length was determined by

according to Ingle’s working length technique . 11

The roots were prepared by using #.04 taper

EasyRaCe nickel-titanium rotary files.(FGK Dentaire

Swiss dental products) according to manufacturers’

instructions along with the use of 1ml of 2.5%

sodium hypochlorite (Novo dental products Ptv .Ltd

,India) and normal saline (Goa Formulation Ltd,

India) as irrigants, and were finally flushed with

17% EDTA (B.N laboratories,India) and dried with

paper points ( DentsplyMaillifer. CH-1338

Ballaigues)

Obturation of the root canals:

Groups I - Served as negative control group.

Roots were not instrumented and not obturated.

Groups II – (Realseal obturation system) A

size 40, #.04 taper Resilon cone was inserted to

the working length with tug-back. The primer and

sealer were applied according to manufacturer’s

instructions. Then, the master Resilon cone of was

gently seated into the canal and obturated with

lateral compaction method. Coronal aspect of

material was light cured for 40 seconds.

Group III- (GuttaFlow obturation system) A master

GuttaFlow gutta percha point of size 40,#.04 taper is

selected and obturated using lateral compaction

method, following manufacturers’ instruction for

manipulating GuttaFlow. Excess obturating material

was removed with a heated hand instrument.12

Group IV – (Conventional lateral compaction

technique.) Canals were obturated using lateral

compaction technique with master gutta percha cone

(SureDent Corporation, Korea) of size 40, #.04 taper

is selected and coated with the zinc oxide eugenol

sealer (Deepti, Vishal Dental products, India).

Group V-( Microseal obturation system) A

Microseal master gutta percha cone of size 40,#.04

taper is selected and obturated using lateral

compaction method, following manufacturers’

instruction for manipulating Microseal compactor.13

The access cavity was sealed with glass

ionomer restorative cement (GC Corporation

Tokyo,Japan).All the specimens were kept at 37°c

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with 100% humidity for at least 72 hours to allow

the sealers to set completely.The roots were fitted

into tight-fitting rubber tubing to simulate the

periodontal ligament Epoxy resin was mixed to a

thin consistency and poured into plastic blocks in

which the roots were vertically placed. Instron

universal testing machine (Model no.3366 U.K). A

special device/Jig (fig 1) was fabricated with stainless

steel to hold the finger spreader with frictional grip

latch, which was attached to the unit of the

universal testing machine with the help of

screw.The access cavity restoration was removed

and then the blocks with embedded roots were

mounted onto the Instron universal testing machine.

A size 40, length 25mm 0.02% taper hand stainless

steel spreader is placed on the universal testing

machine fixture and placed directly above the root

canal orifice,to penetrate through the obturatng

material. The machine was calibrated to vertically

drive the spreader into the root canal at a speed of

10mm/min. Force was applied to the root until it

fractured. The force applied to fracture the tooth

vertically was recorded and data from all

experimental groups were collected and statistiscally

analysed using Kruskal-Wallis test and intergroup

comparison was done by Mann-Whitney U test.

Results :Compressive load at max compressive

extension is shown in table 1. Due to unusual

distribution of the data, nonparametric tests were

applied to check the statistical significance between

the groups. According to the results (graph 1), group

II showed the maximum resistance to fracture

(median value-259.425) and group IVshowed the

minimum resistance to fracture (median value-

28.15).The root canals obturated with Resilon and

RealSeal sealer resulted in significant increase in

the resistance ( p value-0.000) to fracture compared

to other groups. Inter group comparison between

group I and group II is significant with Z value is -

3.908 and (P value 0.000 is significant). Inter group

comparison between group II and group III, group

IV and group V is significant with Z value -3.78

-3.78 and -3.79 respectively . The other groups were

not significantly different from each other.

Compressive Load at Max Compressive Extension

COMPARISON Z P

GI vs. GII -3.908 0.000

GI vs. GIII -0.782 0.434

GI vs. GIV -1.641 0.101

GI vs. GV -2.66 0.008

GII vs. GIII -3.78 0.000

GII vs. GIV -3.78 0.000

GII vs. GV -3.79 0.000

GIII vs. GIV -0.303 0.762

GIII3 vs. GV -1.37 0.170

GIV vs. GV -2.05 0.04

Table1- Inter group comparison performed byMann- Whitney U test. (Z)

Graph 1- Compressive load at maximum compressiveextension for all the experimental groups.

A COMPARATIVE STUDY OF VERTICAL FRACTURE OF ROOTSOBTURATED WITH NEW OBTURATING SYSTEMS - AN IN VITRO STUDY

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Discussion :The present study found that the resistance to

fracture of the obturated teeth was better in case of

teeth obturated with the adhesive obturating system

RealSeal . The traditional obturating material gutta

percha does not provide chemical bonding to the

root canal wall, so recent research in obturation

materials is focused on the introduction of resins

into the cones and the sealer .Inter group

comparison between group I (instrumented and

unobturated root canals) and group II is significant

with Z value is -3.908 and (P value 0.000 is

significant),which shows the importance of

obturating the canals after disinfection .Root canal

instrumentation is an unavoidable step in

endodontic treatment,dentin is removed during this

phase,thus a weaking effect on the root is

inevitable.14 Also clinically one never leaves an

root canal unfilled ,so group I was considered as a

negative control group and showed least resistance

when compared with the other groups.The wedging

forces of the spreader driven into the canal without

resistance could be the reason for the highly

significant values.14

Resilon obturating material - Epiphany as the

bonding agent (sealer) attaches the resin core to the

dentinal wall , thus forms monoblock.9 All the other

materials in the present study created mechanical

bond between the sealer and dentinal wall. The

adhesion and mechanical interlocking between the

material and the root canal dentin prevents

microleakage and reduce the risk of fracture. The

results regarding Resilon in our study were in

accordance with some previous studies.14,15 Sagsen

et.al7, in their study concluded that root canals

obturated with Resilon cones and epiphany sealer

were able to reinforce the prepared root canals.

The bondability of Resilon to methacrylate

resin based root canal sealers is supposed to be

derived from the inclusion of the urethane

dimethacrylate resin. It contains two interface one

Fig 1: Special jig fabricated to hold speraders Fig 2: Specimen mounted on universal testing machine

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between the sealer and primed dentin, another

between the sealer and Resilon, hence may be

classified as a secondary type monoblock.9 So this

property of Resilon could be the reason for the

positive result in our study and the nonadhesive

obturating materials showed poorer result

compared to it. Contrary, Ulusoy etal 16 in their

study found that the use of AH 26 and gutta

.Grande NM etal 17concluded that the currently

available endodontic-filling materials and their

recommended adhesive procedures are not able to

influence the mechanical properties of root canal

dentin and that the flexural properties of Resilon

and gutta-percha are too low to reinforce roots.

According to studies by Tay FR etal Resilon

seems to be biodegradable under the attack of

hydrolytic ester bond cleaving enzymes or as

extracellular enzymes from endodontically relevant

pathogens .Resilon is also susceptible to alkaline

hydrolysis, therefore long term studies are

necessary.18,19

The reason for poor resistance to vertical

fracture of the GuttaFlow system compared to

Resilon could be that there is no chemical union

between the discrete gutta filler particles and the

gutta percha master cone.15,20 Thus the use of a

primer to promote a chemical bond between the

trans1,4-polyisoprene component of the sealer

should be considered. The Microseal system utilizes

alpha form guttaprecha which has lower melting

point, lower viscosity and higher flow when

compared to the beta form gutta-percha. 11

Although recent advances in adhesive

obturating materials have stimulated interest, there

are few studies supporting its ability to reinforce

the endodontically treated tooth and resist vertical

fracture. To reconfirm the result of the present study

further studies have to be undertaken with more

number of samples, under ultrastructural scanning

microscope and also other required properties have

to be confirmed.

Conclusions :The present study concluded-

1. Resilon with RealSeal sealer is the best material

among the experimental groups to resist the post

obturation vertical fracture.

2. Gutta Flow, Microseal and Gutta percha with

zinc oxide sealer cannot resist vertical fracture as

well as Resilon.

References :

1.Walton RE, Torabinejad M. Principal and practice ofendodontics.3rded. Philadelphaia;Saunders ,2002.

2. Schilder H. Cleaning and Shaping the root canal. DentClin North Am 1974;18:269-96.

3.Cohen S ,Burns R .Pathways of the pulp.8th ed.StLouis:Mosby, 2002.

4. Fuss Z,Lustig J,Katz A,Tamse A.An Evaluation ofEndodontically Treated Vertical Root Fractured Teeth: Impactof Operative Procedures.J Endod 2001;27:46-48.

5. Schilder H. Filling root canals in three dimensions. J Endod2006;32:281–90.

6. Schäfer E, Zandbiglari T, Schäfer J. Influence of resin-basedadhesive root canal fillings on the resistance to fracture ofendodontically treated roots: an in vitro preliminary study.Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103: 274-279.

7. Sagsen B, Er O, Kahraman Y, Akdogan G. Resistance tofracture of roots filled with three different techniques.Int EndodJ;2007; I40:31-35.

8. Karapinar Kazandag M, Sunay H, Tanalp J, Bayirli G.Karapinar Kazandag M, Sunay H, Tanalp J, Bayirli G. FractureResistance of Roots using Different Canal Filling Systems. IntEndod J 2009; 42: 705-710.

9.Tay FR,Pashley DH. Monoblocks in root canals:Ahypothetical or a Tangible Goal. J Endod 2007; 33:391-398;

10. Herbert J, Bruder M, Braunsteiner J, Altenburger MJ, WrbasK. Apical quality and adaptation of Resilon, Endorez, and

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11. Ingle JE ,Bakland LK.Endodontics, 5th ed. Hamilton,Ontario,Canada:BC Decker Inc,2002

12.Guttaflow instruction for use.Coltene /WhaledentInc,Cuyahoga Falls ,OH.February 2006.

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14.Teixeira FB,Teixeira EC,Thompson JY,Trope M..Fractureresistance of roots endodontically treated with a new resinfilling material. J Am Dent Assoc May 2004;135: 646652.

15.Hammad M,Qualtrough A,Silikas N.Effect of Newobturating Materials on vertical root fracture resistance ofendodontically treated teeth. J Endod 2007;33:732-36.

16.Ulusoy ÖÏA ,Genc Ö,Alacam T,Görgül G.Fracture reistanceof roots obturated with three different materials.Oral Surg OralMed Oral Pathol Oral Radiol Endod 2007;104:705-8.

17.Grande NM, Plotino G,,Lavorgna L,Ioppolo P,BediniR,Pameijer CH,Somma F. Influence of Different Root Canal–Filling Materials on the Mechanical Properties of Root CanalDentin.J Endod 2007 ;33:859-63.

18.Tay FR,Pashley DH,Yiu CKY,Yau JYY,Yiu-fai M,LoushineRJ,et al .Susceptibility of a polycaprolactone-based root canalfiling material to degradation.II.Gravimetric evaluation ofenzymatic hydrolysis.J Endod 2005;31:737-41.

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VIMMI SINGH, NEETA SHETTY, KUNDABALA M.