Background: The biocompatibility and the aesthetic properties of the ceramic materials are the major reasons for using these materials in dental restorations. One of the challenges in implant dentistry is prediction of the aesthetic result. The high strength, yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) implant abutments are developed to fulfill the aesthetic and mechanical demands of prosthodontic treatments (1, 2). However, in vivo studies of ceramic restorations on implants are few, and there is a need to investigate the clinical outcome of these materials (3).

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.

Material and 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) (figure 1). The biological, technical and aesthetical results were evaluated at a baseline examination (1-2 months after crown cementation). The aesthetical outcome was measured using 6 variables compounded to the “Copenhagen Index Score” (CIS) (4): 1) Crown morphology; 2) Color match of the crown; 3) Harmony and symmetry; 4) Discoloration of buccal mucosa (figure 2); 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 analyze difference for each variable and in CIS-scores.

Results: No biological or technical complications were registered. Difference in CIS scores between AC-group and PFM-group was not 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, score 1: 38.46%, score 2: 61.54%) compared to the AC-group (median: 1, score 1: 70.37%, score 2: 25.93%, score 3: 3.70%). 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.

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