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).
Objectives
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.
References
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.
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strength of composite resins submitted to different activation techniques.
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TEAM: Cláudia Machado de Almeida Mattos, Valéria
P. Freitas, Estevam Barbosa de las Casas, Ítalo G. M. R. Dutra and
Ronan Almeida Faustino.
