Effect of Cyclic Loading on Cement-retained Crowns on Implant Abutments

Objective: This study examined the effect of cyclic loading on the retention of crowns cemented on implant abutments with temporary cements. Methods: Four commercially available temporary cements [HY-Bond Temporary cement Soft (A, Shofu, polycarboxylate cement); HY-Bond Temporary cement (Hard) (B, Shofu, polycarboxylate cement); Temp Bond NE (C, Kerr, paste-mix type) and Freegenol temporary pack (D, GC, paste-mix type)] were tested. Cast crowns made from Ag-Pd-Au alloy (Kinpara-Ace12S, Tokuriki Honten) were cemented on implant abutments (Easy Abutment, Nobel Biocare, 5mm dia., 5mm high) using one of cements. One hour after the start of cement-mixing, each specimen was subjected to cyclic loading (1Hz and 10kgf) at room temperature up to 100,000 cycles using loading equipment (K655-08, Tokyo-Giken). The retentive force values of each crown on the abutment were determined after cyclic loading by a universal testing machine (Instron 4302). The force values measured one hour after the start of cement-mixing served as baseline data. The results were analyzed using ANOVA/Scheffe's test (α=0.05) and Weibull analysis. Results: The table shows the measured retentive force values (N, mean ± sd, n=10) and the Weibull moduli calculated for each cement. Cement B had the greatest retentive force among the cements tested (p<0.05) at baseline. After cyclic loading, the retentive force of cement B decreased but that of cement D increased (p<0.05). After 100,000 cyclic loadings, no significant differences in retentive force values were found among the cements tested (p>0.05). The Weibull moduli decreased at 100,000 cycles for cements A, B and C, which indicates that the retentive force data varied widely after loading. Conclusion: The retentive force of crowns cemented on implant abutments did not differ after cyclic loading among the temporary cements tested. Except for cement D, the retentive force of the cements appeared to vary widely. Supported by JSPS(C)20592308.