Effect of surface conditioning and taper angle on the retention of IPS e.max Press crowns

PURPOSE: The objective of this study was to evaluate the retentive strength of single-unit crowns with 10 degrees and 26 degrees taper angles cemented using two surface conditioning methods. MATERIALS AND METHODS: Thirty-two freshly extracted sound human molars were divided into two groups (n = 16) and prepared in a standardized manner with 10 degrees and 26 degrees taper angles. All-ceramic (IPS e.max Press) single crowns were fabricated for the prepared teeth. The crowns were then subdivided into two groups (n = 8), according to type of surface conditioning for the intaglio surfaces. Half the groups were HF acid etched and silanized, and the other half were conditioned with tribochemical silica coating and silanization. The crowns were cemented using adhesive cement (Panavia F 2.0). Retentive strength was measured in a universal testing machine. RESULTS: No significant difference was found between the mean retention forces for both 10 degrees and 26 degrees taper angles when the crowns were conditioned either with silica coating (613 +/- 190 N and 525 +/- 90 N, respectively), or with hydrofluoric (HF) acid etching and silanization (550 +/- 110 N and 490 +/- 130 N for 10 degrees and 26 degrees, respectively) (p= 0.32). CONCLUSION: Neither the surface conditioning type, nor the taper angle affected the retentive strength of IPS e.max Press single-unit crowns when cemented adhesively. Since silica coating and silanization did not show significant differences from HF acid gel and silanization, the former can be preferred for conditioning intaglio surfaces of glass ceramic crowns to avoid the use of the hazardous compound HF acid gel chairside