تأثير مادة وتصميم الحشوات الضّمنيّة والمغطية على توزّع الإجهادات في الأرحاء السفليّة بطريقة العناصر المنتهية

Influence Of Inlay/Onlay Material And Design On Stress Distribution In Mandibular Molars (Finite Element Analysis)

Abstract

Background and aim: Inlays and onlays are considered as conservative restorations for posterior teeth. The aim of this study was to evaluate the influence of inlays/onlays and their material on stress distribution in mandibular molars, using finite element analysis (FEA).

Materials and methods: A mesio-occluso-distal cavity was created using a 3-dimensional model of a first mandibular molar. Then, the mesiobuccal cusp, all buccal cusps and the lingual cusps were reduced by 1.5 mm, 1.5 mm and 1.0 mm, respectively to create prepared tooth models for: inlay (IN), onlay covered one cusp (MB) and onlay covered all cusps (LB). Inlays/onlays were represented by two materials: lithium disilicate ceramic (L) and polymer-infiltrated ceramic network (P). Vertical and oblique loads of 600 N were applied and stresses were calculated.

Results: Stress concentrated in the buccal cusps and the internal buccal wall of the occlusal cavity in inlay and MB onlay models. Stresses in dental structures in inlay and MB onlay models were higher than LB onlay models. Moreover, stresses within PICN inlay/onlay were less than stresses in L inlay/onlay. Oblique load associated with greater stress concentration in restorations as well as tooth structures in all models than vertical load.

Conclusion: 1. Lithium disilicate ceramic LB onlays might provide good protection of tooth structures as they showed the best pattern of stress distribution in dental tissues among the studied models. 2. Inlays and MB onlays caused high stress concentration in dental structures. Thus, inlays and MB onlays may be unsuitable restorations for conservative cavities in molars.

Keywords: inlay; onlay; polymer-infiltrated ceramic network; lithium disilicate ceramic; FEA.