The effect of abutment and crown design on fracture strength and fracture mode of implant-supported prosthesis (ISP)

This in-vitro study aimed to evaluate the fracture strength and fractographic characteristics of CAD/CAM cement-retained (CR) and screw-retrievable cement- retained (SRCR) implant-supported molar crowns bonded to different titanium-based abutments. Material and methods: Sixty implant crowns, comprising monolithic zirconia and bilayer crowns, were assigned into control and test groups. The control group included monolithic cemented crowns bonded to Variobase (MCV, n=10) and NiTium abutments (MCN, n=10). The test groups consisted of monolithic screw- retained crowns bonded to Variobase (MSV, n=10) and NiTium abutments (MSN, n=10), as well as bilayer screw-retained crowns with reinforced access hole bonded to Variobase (BSV, n=10) and NiTium abutments (BSN, n=10). All crowns were cemented onto prefabricated titanium-based abutments. Samples underwent thermal cycling to simulate oral conditions, followed by a single-load fracture test. Fracture modes were examined using Scanning Electron Microscopy (SEM). Fracture strength values were statistically analyzed using the Mann-Whitney U test, with significance set at P < .05.