Morphological analysis of gutta-percha points subjected to ...
Mechanical properties of Resilon and gutta-percha under flexural stresses
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85 D38 - Mechanical properties of Resilon and gutta-percha under flexural stresses IOPPOLO P. 1 , PLOTINO G. 2 , GRANDE N.M. 2 , BEDINI R. 1 , SOMMA F. 2 1 Italia n Nation al Insti tute of He alth, T echnolog y and Hea lth Department, Ro- me; 2 Departme nt of Endodon tics, Cath olic Univer sity of Sacre d Heart, Rome Introduction. A recent paper has shown that canals filled with Resilon increased the in vitro resistance to fracture of endodontically treated single-canal extracted teeth when compared to standard techniques using gutta-percha (1). Nevertheless, it has been shown that Tone, the parent “polymer” of Resilon, is an elastomeric material and its cohe- sive strength is too low to reinforce the roots of endodontically-treat- ed teeth (2). Aim of the present study was to evaluate the Resilon ma- terial mechanical properties, comparing to gutta-percha, under flexur- al stresses. Materials and methods. 20 Resilon pellets (Real Seal, Sybron Endo, Orange, USA) and 20 gutta-percha pellets for use with the Obtura gun were used in this study (Fig. 1). The random selected specimens were taken off from a commercially avaiable box and subjected to failure load with a three-point bending test by means of an electronic dy- namometer (Lloyd Instru- ments Ltd, UK) equipped with a 500 N load cell (Fig. 2). This mechanical test was performed (according to the ISO 10477 standard) with 2 mm cross-sectional diame- ter of loading tip and 10.0 mm grip span-length, at 1.0 mm/min crosshead speed. Specimen flexural modulus and flexural strength values have been obtained after the test. The load-deflection curves were obtained by means of a dedicated PC- software (Nexygen Mt v4.5, Lloyd Instruments Ltd, UK). The obtained values were processed by means of the t- test with a significance level of P < 0.05. Results. There was significant statistically difference (P<0.05) between the flexural modulus values obtained with gutta-percha (285.6±36.6 Mpa) and Re- silon (200.7±17.9 Mpa) pel- let specimens. There was statistically significant dif- ference (P < 0.05) between the flexural strength values of Resilon (29.3±1.6 Mpa) and gutta-percha (20.5±1.0 Mpa) pellet specimens. Conclusions. Endodontic filling materials to strength- en roots have to approach dentine elastic modulus, ranging from 16 to 18 GPa (3). The polymer matrix of Resilon is made up of poly- caprolactone, that is a ther- moplastic polyester, and according to experimental results of this study its elastic modulus is not so different to gutta-percha value, even if statistically difference was found. These results are far from to den- tine elastic modulus performance, therefore Resilon will not reinforce roots any better than gutta-percha. This is in accordance to previous reported results on the Resilon and gutta-percha elastic modulus (2). Clinically, Resilon’s modulus of elasticity is so low that it flows when stressed, instead of resisting stress. Under stress, the polymer chains slide over each other and allow the material to flow (4). This properly permits it to adapt to the irregularities of root canals just like gutta-per- cha. As the root is stressed, even if the self-etching adhesive remains bonded to dentin, the very low modulus of elasticity of Resilon will be unable to resist the stress and the material will strain or elongate (4). References 1. Teix eira FB, Teix eira ECN, T hompson J Y, Trope M. Fracture resistance of roots endodontically treated with a new resin filling material. J Am Dent Assoc 2004; 135:646-652. 2. Pashley DH. Adhes ive Dent istry : Are There Endod onti c Applic atio ns?. www.rxroots.com. 3. Kinney JH, Marshall SJ, Mars hall GW . The mechani cal prope rties of hu man dentin: a critical review and re-evaluation of the dental literature. Crit Rev Oral Biol Med 2003; 14:13-29. 4. Pashl ey DH. Endodont ic Appl icati ons of Adhesive Dentis try . www.rxroots.com. G It Cons - Supplemento vol. IV - n. 1 Gennaio-Marzo 2006 © Copyright 2006, CIC Edizioni Internazionali, Roma. Fig. 1. Resilon (right) and gutta-percha (left) pel- let used in this study. Fig. 2. Three-point bending test system grip used during mechanical test.
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D38 - Mechanical propertiesof Resilon and gutta-perchaunder flexural stressesIOPPOLO P. 1, PLOTINO G. 2, GRANDE N.M. 2,BEDINI R. 1, SOMMA F. 2
1 Italian National Institute of Health, Technology and Health Department, Ro-me; 2 Department of Endodontics, Catholic University of Sacred Heart, Rome
Introduction. A recent paper has shown that canals filled with Resilonincreased the in vitro resistance to fracture of endodontically treatedsingle-canal extracted teeth when compared to standard techniquesusing gutta-percha (1). Nevertheless, it has been shown that Tone, theparent “polymer” of Resilon, is an elastomeric material and its cohe-
sive strength is too low to reinforce the roots of endodontically-treat-ed teeth (2). Aim of the present study was to evaluate the Resilon ma-terial mechanical properties, comparing to gutta-percha, under flexur-al stresses.Materials and methods. 20 Resilon pellets (Real Seal, Sybron Endo,Orange, USA) and 20 gutta-percha pellets for use with the Obtura gunwere used in this study (Fig. 1). The random selected specimens weretaken off from a commercially avaiable box and subjected to failureload with a three-point bending test by means of an electronic dy-
namometer (Lloyd Instru-ments Ltd, UK) equippedwith a 500 N load cell (Fig.2). This mechanical test wasperformed (according to theISO 10477 standard) with 2
mm cross-sectional diame-ter of loading tip and 10.0mm grip span-length, at 1.0mm/min crosshead speed.Specimen flexural modulusand flexural strength valueshave been obtained afterthe test. The load-deflectioncurves were obtained bymeans of a dedicated PC-software (Nexygen Mt v4.5,Lloyd Instruments Ltd, UK).The obtained values wereprocessed by means of the t-
test with a significance level of P < 0.05.
Results. There was significant statistically difference (P<0.05) betweenthe flexural modulus valuesobtained with gutta-percha(285.6±36.6 Mpa) and Re-silon (200.7±17.9 Mpa) pel-let specimens. There wasstatistically significant dif-ference (P < 0.05) betweenthe flexural strength valuesof Resilon (29.3±1.6 Mpa)and gutta-percha (20.5±1.0Mpa) pellet specimens.Conclusions. Endodonticfilling materials to strength-en roots have to approach
dentine elastic modulus,ranging from 16 to 18 GPa(3). The polymer matrix of Resilon is made up of poly-caprolactone, that is a ther-
moplastic polyester, and according to experimental results of thisstudy its elastic modulus is not so different to gutta-percha value, evenif statistically difference was found. These results are far from to den-
tine elastic modulus performance, therefore Resilon will not reinforceroots any better than gutta-percha. This is in accordance to previousreported results on the Resilon and gutta-percha elastic modulus (2).Clinically, Resilon’s modulus of elasticity is so low that it flows whenstressed, instead of resisting stress. Under stress, the polymer chainsslide over each other and allow the material to flow (4). This properlypermits it to adapt to the irregularities of root canals just like gutta-per-cha. As the root is stressed, even if the self-etching adhesive remainsbonded to dentin, the very low modulus of elasticity of Resilon will beunable to resist the stress and the material will strain or elongate (4).
References
1. Teixeira FB, Teixeira ECN, Thompson JY, Trope M. Fracture resistance of rootsendodontically treated with a new resin filling material. J Am Dent Assoc2004; 135:646-652.
2. Pashley DH. Adhesive Dentistry: Are There Endodontic Applications?.www.rxroots.com.
3. Kinney JH, Marshall SJ, Marshall GW. The mechanical properties of humandentin: a critical review and re-evaluation of the dental literature. Crit RevOral Biol Med 2003; 14:13-29.
4. Pashley DH. Endodontic Applications of Adhesive Dentistry.www.rxroots.com.
G It Cons - Supplemento vol. IV - n. 1Gennaio-Marzo 2006
© Copyright 2006, CIC Edizioni Internazionali, Roma.
Fig. 1. Resilon (right) and gutta-percha (left) pel-let used in this study.
Fig. 2. Three-point bending test system grip usedduring mechanical test.
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