Influence of the cavity shape in restorative dentistry on the stress-strain distribution in dentine and enamel caused by polymerization

Abstract

In restorative dentistry it is common practice to replace amalgams with resin based dental composites, with minimal or no additional cavity preparation. Polymerization shrinkage of dental composites causes stress, whose influence is transferred to tooth tissue which may result in the occurrence of micro-cracks and post-operative pain. The aim of this study is to determine the effects of different cavity shapes on stress and strain distribution which occurred due to composite shrinkage. Toward this aim, experimental (Digital Image Correlation method – DIC) and numerical (finite element method – FEM) techniques are used. The numerical model is verified by comparing its results with those obtained by experimental methods. Upon verification, the 3D model of the cavity is modified to develop two new models with the same tooth geometry, but different cavity shapes, in order to determine the effect of their shapes on stress distribution. It is determined that the thickness of dentine around the cavity plays a significant role in stress and strain distribution.

U restorativnoj stomatologiji je učestala praksa zamene amalgama stomatološkim kompozitima na bazi smole, uz minimalnu dodatnu pripremu kaviteta ili bez nje. Polimerizacijsko skupljanje stomatoloških kompozita prouzrokuje napon, čiji se uticaj prenosi na zubno tkivo, što može dovesti do pojave mikroprslina i postoperativnih bolova. Cilj ovog rada je da se odredi uticaj različitih oblika kaviteta na raspodelu napona i deformacija. izazvanih skupljanjem kompozita. U tu svrhu su korišćene eksperimentalna metoda korelacije digitalnih slika (DIC) i numerička metoda konačnih elemenata (FEM). Numerički model je verifikovan poređenjem rezultata proračuna sa rezultatima dobijenim eksperimentalnom metodom. Nakon verifikacije, postojeći 3D model kaviteta je modifikovan u cilju dobijanja dva nova modela sa istom geometrijom zuba i različitim oblicima kaviteta, kako bi se odredio uticaj ovih oblika na raspodelu napona. Utvrđeno je da debljina dentina oko kaviteta igra značajnu ulogu u raspodeli napona i deformacija.