Implant rehabilitation of edentulous jaws with predominantly monolithic zirconia compared to metal-acrylic prostheses: a 2-year retrospective clinical study

Limited data are available on the clinical outcomes of patients with edentulism treated with predominantly monolithic zirconia fixed complete dentures (FCDs) compared to traditional restoration materials. The purpose of this study was to analyze the differences in terms of complications and failures of definitive full-arch implant rehabilitations made in metal-acrylic versus those made in monolithic zirconia with porcelain veneering limited to non-functional areas. This retrospective clinical study included 50 patients treated between January 2015 and December 2018, with 222 implants inserted in fifty edentulous jaws. All patients were treated with immediately loaded full-arch fixed prostheses (22 maxillary; 28 mandibular) each supported by four to six implants (two/four axial, two distally tilted). All 25 zirconia prostheses were predominantly monolithic with ceramic veneering limited to non-functional areas. The primary outcome measures were prosthetic success of the definitive restoration and implant survival. The secondary outcome measures were full mouth plaque score, full mouth bleeding score, peri-implant probing depths and periimplant keratinized tissue. All implants and prostheses analyzed had a minimum of 2 years of followup. No chipping of the veneered facial porcelain or other technical complication was observed over the study period achieving a prosthesis survival and success rate of 100%. No implants were lost, achieving a 100% survival rate. Bleeding on probing was positive in 33% and 13% of probing sites for metal-acrylic prosthesis and zirconia prosthesis, respectively (p = 0.0445). Plaque index was positive in 76% and 53% of probing sites for metal-acrylic prosthesis and zirconia prosthesis, respectively (p = 0.0491). Mean probing depth was 1.74mm (SD 0.89mm) for the 106 implants supporting metal-acrylic prosthesis and 1.52mm (SD 0.63mm) for the 116 implants supporting zirconia prosthesis (p=0.0412). No other statistically significant differences were found between the two groups. The results of this retrospective evaluation showed that predominantly monolithic zirconia is a feasible alternative to the conventional metal framework acrylic for full arch implant-supported prosthesis. The restauration material did not influence the failure rate and complication risk of both prosthesis and implants.