8/12/2019 Mechanical properties of Resilon and gutta-percha under flexural stresses

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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.