Stresses in Cast Metal Inlays Restored Molars

Authors: Sandu L., Topală F., Porojan S.

Abstract:

Cast metal inlays can be used on molars requiring a class II restoration instead amalgam and offer a durable alternative. Because it is known that class II inlays may increase the susceptibility to fracture, it is important to ensure optimal performance in selection of the adequate preparation design to reduce stresses in teeth structures and also in the restorations. The aim of the study was to investigate the influence of preparation design on stress distribution in molars with different class II preparations and in cast metal inlays. The first step of the study was to achieve 3D models in order to analyze teeth and cast metal class II inlays. The geometry of the intact tooth was obtained by 3D scanning using a manufactured device. With a NURBS modeling program the preparations and the appropriately inlays were designed. 3D models of first upper molars of the same shape and size were created. Inlay cavities designs were created using literature data. The geometrical model was exported and the mesh structure of the solid 3D model was created for structural simulations. Stresses were located around the occlusal contact areas. For the studied cases, the stress values were not significant influenced by the taper of the preparation. it was demonstrated stresses are higher in the cast metal restorations and therefore the strength of the teeth is not affected.

Keywords: cast metal inlays, class II restoration, molars, 3D models, structural simulations.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1079424

References:

[1] Fonseca, R.B.; Fernandes-Neto, A.J.; Correr-Sobrinho, L. & Soares, C.J. (2007). The influence of cavity preparation design on fracture strength and mode of fracture of laboratory-processed composite resin restorations. J Prosthet Dent. 98:277-284, ISSN 0022-3913.
[2] Dejak, B.; Mlotkowski, A. & Romanowicz, M. (2003). Finite element analysis of stresses in molars during clenching and mastication. J Prosthet Dent. 90:591-7, ISSN 0022-3913.
[3] Shillingburg, H.T. (1997). Fundamentals of fixed prosthodontics. 3rd ed. Chicago: Quintessence. p.171-9, ISBN 0-86715-201-X.
[4] Dejak, B.; Mlotkowski, A. & Romanowicz, M. (2007). Strength estimation of different designs of ceramic inlays and onlays in molars based on the Tsai-Wu failure criterion. J Prosthet Dent.98: 89-100, ISSN 0022-3913.
[5] Yamanel, K.; Caglar, A.; Gulsahi, K. & Ozden, U.A. (2009). Effects of different ceramic and composite materials on stress distribution in inlay and onlay cavities: 3-D finite element analysis. Dental Materials Journal. 28(6): 661-670, ISSN 0109-5641.
[6] Dejak, B. & Mlotkowski, A. (2008). Three-dimensional finite element analysis of strength and adhesion of composite resin versus ceramic inlays in molars. J Prosthet Dent. 99: 131-140, ISSN 0022-3913.