Effect of Using Different Primary Crown Materials on the Retention of CAD/CAM Telescopic Partial Dentures

Abstract

AIM: This study compared the effect of using different primary crown materials (zirconia and cobalt-chromium) on the retention of telescopic retained removable partial dentures. MATERIALS AND METHODS: A maxillary Kennedy class I stone model was prepared and scanned. The virtual cast was adjusted to create four abutments at the positions of the canines and the first premolars. Primary crowns were designed and then milled. In Group I, seven primary crowns were milled out of zirconia, and in Group II, seven primary crowns were milled from cobalt-chromium blanks. Cobalt-chromium telescopic partial dentures were milled. The universal testing machine was utilized to apply vertically dislodging static forces. Initial retention values were recorded. Then, the chewing simulator (CS) was used to apply dynamic cyclic loading to each partial denture. And after, 50,000 cycles and 270 attempts of insertion and removal final retention values were recorded. The data were collected and statistically analyzed. RESULTS: A significant decrease in retention in both groups after simulation of 3 months of partial denture function was recorded. It was found that after simulation of 3 months of function Group I (zirconia) recorded a statistically significant higher mean value; (1.935 ± 0.268 N) than Group II; (0.583 ± 0.018 N) as indicated by student t-test (p ≤ 0.0001 < 0.05). CONCLUSION: Zirconia primary crowns attain higher retention values than cobalt-chromium with cobalt-chromium telescopic partial dentures after simulation of 3 months of function.