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Analysis of Mechanical Behaviour of Root Reinforcement in Weakened Roots by Finite Element Method

The teeth treated endodontically are more prone to root fracture, and this was clinically observed and supported by evidences from retrospectives studies (1, 2). The restoration of these teeth is often a complex task because of the loss of structure caused by caries, trauma or extensive restorations (3). When destruction reaches the root, the canal become very large and the wall become weakened (Figure 1c), hindering the placement of intraradicular pins required for the final tooth restoration in the conventional way. The molten metal pins are very rigid and its conical shape causes a wedge effect, increasing the risk of root fracture (4, 5). Pins nonmetallics prefabricated with parallel walls do not adapt perfectly to the shape of the canal in the cervical region of the roots, leading to a lower retention and a greater instability of the pin, which also predispose to root fracture (6).



Figure 1 - Different stages of root destruction

The cervical portion of the tooth is subjected to forces of compression, tension and torsion significant during chewing. Therefore, the previous structural rehabilitation of weakened root is critical to ensuring the success of restorative treatment of the devitalized tooth. A type of reinforcement intraradicular in the cervical region has been suggested to reinforce clinically roots with thin walls through adhesive materials such as the photopolymerizable composite resin and the glass ionomer cermet type, due to its favorable mechanical properties and the adhesion to dentin walls (7-11).


Given the above this study aims to:

1. Determine, if necessary experimentally, mechanical properties related to contraction, elasticity and adhesion of the materials used in reinforcing root.

2. Compare, numerically, the behavior of root reinforcement with composite resin and with glass ionomer, in the increased of resistance to root fracture of a structurally weakened root.

3. Assess the type of failure of root reinforcements.

Materials and Methods

Will be made a finite element model of a root, to be analyzed by a commercially available software (Abaqus), featuring a loss of structure in the cervical region, reinforced and rebuilt with pin, nucleus and total crown, where it will be a force in the palate, with 45º with the long axis of the tooth, simulating masticatory force.

The two types of material (composite resin and cermet ionomer) will be examined in simulation, as variations of techniques. The results obtained will be confronted with in vitro studies previously published.


1. Gher ME, Jr., Dunlap RM, Anderson MH, Kuhl LV. Clinical survey of fractured teeth. J Am Dent Assoc 1987;114(2):174-7.
2. Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet Dent 1984;51(6):780-4.
3. Johnson ME, Stewart GP, Nielsen CJ, Hatton JF. Evaluation of root reinforcement of endodontically treated teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;90(3):360-4.
4. Leles C, Souza J, Busato A. Princípios das restaurações com retenção intra-radicular. In: Estrela C, editor. Ciência Endodôntica. 1 ed. São Paulo: Artes Médicas
2004. p. 1010.
5. Bonfante G, Kaizer OB, Pegoraro LF, do Valle AL. Fracture strength of teeth with flared root canals restored with glass fibre posts. Int Dent J 2007;57(3):153-60.
6. Assif D, Nevo E, Aviv I, Himmel R. Retention of endodontic posts with a composite resin luting agent: effect of cement thickness. Quintessence Int 1988;19(9):643-6.
7. Calheiros FC, Kawano Y, Stansbury JW, Braga RR. Influence of radiant exposure on contraction stress, degree of conversion and mechanical properties of resin composites. Dent Mater 2006;22(9):799-803.
8. Casselli DS, Worschech CC, Paulillo LA, Dias CT. Diametral tensile strength of composite resins submitted to different activation techniques. Braz Oral Res 2006;20(3):214-8.
9. Lazarchik DA, Hammond BD, Sikes CL, Looney SW, Rueggeberg FA. Hardness comparison of bulk-filled/transtooth and incremental-filled/occlusally irradiated composite resins. J Prosthet Dent 2007;98(2):129-40.
10. Terry DA, Leinfelder KF. Managing stress with composite resin, Part 1: The restorative-tooth interface. Dent Today 2006;25(12):98, 100-4; quiz 104.
11. Tolosa MC, Paulillo LA, Giannini M, Santos AJ, Dias CT. Influence of composite restorative materials and light-curing units on diametrical tensile strength. Braz Oral Res 2005;19(2):123-6.

TEAM: Cláudia Machado de Almeida Mattos, Valéria P. Freitas, Estevam Barbosa de las Casas, Ítalo G. M. R. Dutra and Ronan Almeida Faustino.

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