Influence of Vertical versus Horizontal Margin Configuration on Fracture Resistance of Zirconia Copings Restorations with Varied Occlusal Thickness

Abstract

Objectives: To compare the influence of vertical (featheredge) margin configuration versus horizontal (deep chamfer) margin configuration on fracture resistance of zirconia copings with the different occlusal thicknesses (0.5mm and 1mm). Materials and methods:Two stainless steel master dies were designed and then milled to mimic the coping preparation of the upper first premolar tooth and duplicated by means of epoxy resin to yield forty dies. 40 epoxy dies were distributed into two groups (n=20) in relation to the margin configuration types; feather edge (F) group (n=20) and deep chamfer (DC) group (n=20). Each group was subdivided into two subgroups (n = 10) concerning varied occlusal thickness (0.5 and 1 mm). Copings were fabricated from zirconia blank. For the testing of fracture resistance, a universal testing machine was used by subjecting the samples to a fixed load till failure occurred. Statistical analysis was then performed.Results: Feather edge margin with (1mm) occlusal thickness registered the highest mean fracture load (1117.81±124.90N) followed by deep chamfer margin with (1mm) occlusal thickness (1000.73±148.84N). While the feather edge margin with (0.5mm) occlusal thickness registered the lowest mean fracture load (282.31± 45.69N) with no significant difference between groups.Conclusions: Vertical margin configuration margin has a more promising fracture resistance than horizontal margin configuration, especially in (1mm) occlusal thickness. Although (0.5mm) restorations occlusal thickness exceeds the maximum chewing forces reported in the literature.