Influence of cement film thickness on the retention of implant-retained crowns.

PurposeThe main goal of this study was to establish a new, high precision procedure to evaluate the influence of cement film thickness on the retention of cemented implant-retained crowns. Materials and MethodsNinety-six tapered titanium abutments (6 degrees taper, 4.3 mm diameter, Camlog) were shortened to 4 mm. Computer-aided design was used to design the crowns, and selective laser sintering, using a cobalt-chromium alloy, was used to produce the crowns. This method used a focused high-energy laser beam to fuse a localized region of metal powder to build up the crowns gradually. Before cementing, preset cement film thicknesses of 15, 50, 80, or 110m were established. Glass ionomer, polycarboxylate, or resin cements were used for cementation. After 3 days storage in demineralized water, the retention of the crowns was measured in tension using a universal testing machine. ResultsThe cement film thicknesses could be achieved with a high level of precision. Interactions between the factors cement and cement film thickness could be found (p 0.001). For all cements, crown retention decreased significantly between a cement film thickness of 15 and 50m (p 0.001). At 15m cement film thickness, the resin cement was the most retentive cement, followed by the polycarboxylate and then the glass ionomer cement (p 0.05). ConclusionsThe results suggest that cement film thickness has an influence on the retentive strength of cemented implant-retained crowns.