A randomized, clinical study of implant-supported all-ceramic crowns and abutments

Objective: The purpose of this study was to compare the aesthetical results of implant-supported all-ceramic crowns retained on zirconia abutment with porcelain-fused-to-metal crowns retained on titanium abutment. Methods: Twenty five patients with tooth agenesis of one or more premolars were treated with 53 single tooth implants (Astra Tech®, Sweden). The prosthodontic treatments were randomized between all-ceramic crowns on zirconia abutments (AC-group, test, n=27) and conventional porcelain-fused-to-metal (PFM) crowns on titanium abutments (PFM-group, control, n=26). The biological, technical and aesthetical results were evaluated at the baseline examination (1-2 months after crown cementation). The aesthetical outcome was measured using “Copenhagen Index Score” (CIS) including 6 variables: 1. Harmony and symmetry; 2. Color match of the crowns; 3. Crown morphology; 4. Discoloration of buccal mucosa; 5. Papilla level, mesially; 6. Papilla level, distally. Each score ranged between 1 for optimal and 4 for poor aesthetic, resulting in CIS-scores between 6 and 24. Mann-Whitney U test was used to analyse difference in CIS-scores and for each variable. Results: No biological or technical complications were registered. Difference in CIS scores between AC-group and PFM-group wasn't statistic significant (p= 0.087, AC-group median: 11.0, 25% and 75% quartile: 10 and 13, PFM-group median: 12.5, 25% and 75% quartile: 11 and 13). Significant (p= 0.0332) higher discoloration scores were registered in the PFM-group (median: 2) compared to the AC-group (median: 1). The other aesthetic variables demonstrated no significant differences. Conclusion: The overall aesthetical result of the all-ceramic superstructures was almost the same as for the PFM crowns retained on titanium abutments in the premolar region. However, less buccal discoloration was seen at the all-ceramic crowns on zirconia abutments, compared to PFM crowns on titanium abutment.