Abstract
The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA) quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram® Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon® Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram® Zirconia (73%) and Cercon® Zirconia (80%) restorations, respectively. Slight color mismatch rate was higher for InCeram® Zirconia restorations (66%) than Cercon® Zirconia (26%) restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05). This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.
Highlights
The traditional metal-fused-to-ceramic crowns have been challenged by the esthetic all-ceramic crown materials over the past decades, and the increasing demands for high esthetics coupled with biocompatibility and strength has resulted in an evolution in all-ceramic restorations[2]
Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05). This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone
Slight marginal discrepancy (SCR) was higher in the InCeram® Zirconia group (26%) than the Cercon® Zirconia (20%) group
Summary
The traditional metal-fused-to-ceramic crowns have been challenged by the esthetic all-ceramic crown materials over the past decades, and the increasing demands for high esthetics coupled with biocompatibility and strength has resulted in an evolution in all-ceramic restorations[2]. The development of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and transformation-toughening has led to a break-through in the field of esthetic full veneer restorations, and allowed the high-strength zirconia to be used for fabrication of fixed partial prostheses even in loadbearing regions[8,26]. In response to mechanical stimuli, the partially stabilized tetragonal phase transforms to monoclinic phase and the accompanying volumetric expansion (4%) results in blunting the propagating crack tip and reduction in the incidence of mechanical failures in zirconia. The InCeram® Zirconia was developed later by incorporation of partially stabilized tetragonal zirconia into InCeram® Alumina to improve the strength of the core material[7]. Similar to InCeram® Alumina, both the block and the slip material are infiltrated with specially developed VITA InCeram® Zirconia glasses and, like all other infiltration ceramics, veneered with VITAVM 7. The clinical outcome of InCeram® Zirconia fixed prostheses is extremely high with very low episodes of failure in such use[10,21,24], the available data for InCeram® Zirconia restorations are still limited to draw reliable conclusions[26]
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