Retention of Crowns to Implant Abutments Using Experimental Provisional Cements

Objective: This study examined the retentive force of crowns cemented on implant abutments using experimental provisional cements having different powder particle distributions. Methods: Four experimental polyacrylic provisional cements with different particle distributions of the pre-reacted glass particles (S-PRG) [MP10; MP11; MP13 and MP14 (Shofu)] were tested (P/L ratio=1.8g/1.0g). Compressive strength: Cylindrical specimens (4mm in diameter, 6mm high) of each cement were prepared using Teflon molds. One hour after the start of mixing, each specimen was immersed in deionized water at 37°C for 7 days. The compressive strength of each cement was determined using a universal testing machine (Instron 4302). Retentive force: Cast crowns made from Ag-Pd-Au alloy (Kinpara-Ace12S, Tokuriki Honten) were cemented on implant abutments (Easy Abutment, Nobel Biocare, 5mm in diameter, 5mm high) using one of cements. One hour after the start of mixing, each specimen was stored in 100% relative humidity at 37°C for 7 days. The retentive force values of each crown on the abutment were measured in the universal testing machine. The results for compressive strength and retentive force were statistically analyzed using ANOVA/Scheffè's test at α=0.05. Results: The measured compressive strength values (MPa, mean±sd, n=7) and the retentive force values (N, mean±sd, n=7) for each cement are summarized in the table. Cements MP10 and MP11 had greater compressive strength than MP13 and MP14 (p<0.05). There were no significant differences in the compressive strength between MP10 and MP11 or between MP13 and MP14 (p>0.05). The retentive force values¡¡of the crowns ranged from 93 to 123N. However, no statistical differences in retentive force values were found among the cements tested (p>0.05). Conclusion: Under the present experimental conditions, powder particle distribution of cements influenced the compressive strength, but did not substantially affect the retention of crowns to abutments. Supported by JSPS(C)20592308.