Stress analysis of cemented or resin-bonded loaded porcelain inlays

Ceramic inlays have become an interesting alternative to amalgam fillings. There are two main ways to affix the inlay to the tooth: by use of either a cement or a composite adhesion system. The aim of the investigation was to examine the two methods' influence on stresses in the inlay and the shear-stress state in the gluing materials. The finite element method (FEM) was used to calculate the stresses and displacements. A two-dimensional inlay was modeled with a 200-N point load on the occlusal surface just over the isthmus. Composite and cement linings were stimulated with and without adhesion, and the stresses were calculated. The results showed a marked compression of the dentin below the proximal part of the inlay. The direct effects of the different elastic constants of the two lining materials influenced the stresses in only a minor way. Complete adhesion reduced stresses in the inlay, compared with cemented inlays, with no adhesion along the pulpal wall. Higher shear stresses were also calculated in the cement compared with the composite.