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Analysis of Stress Distribution in the Photopolymerization of Resins and Subsequent Release of Tensions after Hygroscopic Expansion

Replacing traditional mechanical methods of retaining restorative materials are currently being used conservative methods of adherence. The concept of large preparations is being abolished and replaced by less invasive preparation, with the adhesives methods. You can find bonding agents that adhere to various substrates (dentin, enamel, amalgam, metal and porcelain), being that the adhesiveness to each is distinct.

When using a resin to fill a preparation, this can be cured or not, and that healing can be followed by a contraction of the material. The contraction of a resin is a mechanical property. When applying restrictions on the movement of the material on contraction and phase change, stresses appear in it. Those tensions will remain in the material after its polymerization and may be understood as residual stresses. However, some of these tensions can be released by hygroscopic expansion that occurs in the resin when it comes into contact with water.

This study aims to evaluate the residual stresses developed in the polymerization of photo-activated resins, using different filling techniques, and their subsequent reduction during hygroscopic expansion.

Aiming to better understand and model the proposed problem, we decided to fabricate a three dimensional model of the cavity preparation. Taking into account the effect of contraction of the resin is less significant in a region away from the preparation, was adopted by isolating a portion of biomaterials in the region near the contraction in order to reduce the size of the model. The figure below illustrates the model with the three materials considered: enamel (blue), dentin (red) and resin (orange).




Figure 1


This model has a highly non-linear character. There are two types of non-linearity: the non-linearity introduced by the steps of filling (geometric non-linearity) and the non-linearity from the state of the interface, ie, if this is breached or not.

TEAM: Estevam Barbosa de las Casas, Rodrigo Lambert Or éfice, Elissa Talma and João Batista Novaes Júnior.

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