Objectives: to evaluate the effect of the addition of circumferential grooves to the abutments on the retention of cemented crowns in an implant system using two types of cements. Methods: 52 implant abutments (MIS, Israel) were divided into four groups: no grooves, one groove, two grooves and three grooves. Other than the number of grooves, all abutments were identical. 13 NiCr identical casts were prepared to fit all 52 abutments. The casts were cemented to each group of abutments using a temporary cement (Tempbond NE, Peterborough, UK) and a permanent cement (Harvard Cement, Harvard Dental, Germany). The casts were separated from the abutments using an Instron testing machine (crosshead speed of 0.5 cm/min) and the maximum retentive forces were recorded. The data were subjected to one way-ANOVA and Tukey tests. Results:the mean retentive forces for Tempbond NE cement were 168±32 N for no grooves,192±33 N for one groove, 208±23 N for two grooves and 246±17 N for three grooves. The mean retentive forces for Harvard cement were 343±60 N for no grooves, 579±30 N for one groove and 540±38 N for two grooves (results for three grooves have not been obtained yet). For Tempbond cement groups, retention values were increased in accordance to the number of grooves (p<0.001). For Harvard cement, addition of one and two grooves increased retention values, similarly (p<0.001). Conclusions: The findings suggest that addition of circumferential grooves to implant abutments increases the retention of crowns cemented with Tempbond as well as Harvard cements. These grooves can be crucial for the retention of crowns cemented to short abutments of implant systems.

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