Double Full-Arch Versus Single Full-Arch, Four Implant-Supported Rehabilitations: A Retrospective, 5-Year Cohort Study.

PURPOSE: To report the 5-year outcome of the All-on-4 treatment concept comparing double full-arch (G1) and single-arch (G2) groups. MATERIALS AND METHODS: This retrospective cohort study included 110 patients (68 women and 42 men, average age of 55.5 years) with 440 NobelSpeedy groovy implants. One hundred sixty-five full-arch, fixed, immediately loaded prostheses in both jaws were followed for 5 years. G1 consisted of 55 patients with double-arch rehabilitations occluded with implant-supported fixed prostheses, and G2 consisted of 55 patients with maxillary single-arch rehabilitations or mandibular single-arch rehabilitations occluded with natural teeth or removable prostheses. The groups were matched for age (±6 years) and gender. Primary outcome measures were cumulative prosthetic (both interim and definitive) and implant survival (Kaplan-Meier product limit estimator). Secondary outcome measures were marginal bone levels at 5 years (through periapical radiographs and using the patient as unit of analysis) and the incidence of mechanical and biological complications. Differences in survival curves (log-rank test), marginal bone level (Mann-Whitney U test), and complications (chi-square test) were compared inferentially between the two groups using the patient as unit of analysis with significance level set at p ≤ 0.05. RESULTS: No dropouts occurred. Prosthetic survival was 100%. Five patients lost 5 implants (G1: n = 3; G2: n = 2) before 1 year, rendering an estimated cumulative survival rate of 95.5% (G1: 94.5%; G2: 96.4%; Kaplan-Meier, p = 0.645, nonsignificant). The average (SD) marginal bone level was 1.56 mm (0.89) at 5 years [G1: 1.45 mm (0.77); G2: 1.67 mm (0.99); p = 0.414]. The incidence rate of mechanical complications (in both interim and definitive prostheses) was 0.16 and 0.13 for G1 and G2, respectively (p = 0.032). The incidence rate of biological complications was 0.06 and 0.05 for G1 and G2, respectively (p = 0.669). CONCLUSIONS: Based on the results, rehabilitating double- or single-arch edentulous patients did not yield significant differences on survival curves. The incidence of mechanical complications was significantly higher for double-arch rehabilitated patients but nevertheless, these mechanical complications did not affect the long-term survival of either the prostheses or the implants.

Preliminary report on the outcome of tilted implants with longer lengths (20-25 mm) in low-density bone: one-year follow-up of a prospective cohort study.

PURPOSE: The aim of this preliminary study was to report on the short-term outcome of tilted implants with 20 to 25 mm of length in immediate function with bicortical anchorage for prosthetic rehabilitation of complete edentulous jaws with low-density bone. MATERIAL AND METHODS: Sixteen patients (with 25 study implants and 43 nonstudy implants) presenting low-density bone were included in a prospective single cohort study to evaluate the short-term outcome of partial and complete edentulous rehabilitations using implants with 20 to 25 mm of length (NobelSpeedy Groovy, Nobel Biocare AB, Gothenburg, Sweden) in immediate function with bicortical anchorage (maxilla: alveolar ridge and nasal corticals; mandible: mandibular corticals). The patients were followed between 6 and 26 months (average of 14 months). Outcome measures were implant survival, marginal bone remodeling, biological and mechanical complications assessed at 10 days, 2, 4, and 6 months, 1-year posttreatment, and thereafter every 6 months. RESULTS: Two patients with four implants were lost to follow-up after 6 and 11 months. There were no implant failures, rendering a cumulative implant survival rate of 100%. The average marginal bone remodeling was 0.50 mm (SD = 0.34 mm) and 0.86 mm (SD = 0.46 mm), after 6 months and 1 year, respectively. There was one mechanical complication in one patient (abutment loosening) 1 month post-surgery. CONCLUSION: Within the limitations of this study, the short-term outcome of prosthetic rehabilitations of patients with low-density bone using implants of 20 to 25 mm in length in immediate function with bicortical anchorage is viable judging by the high implant survival rate, low marginal bone remodeling, and low incidence of complications. Long-term evaluation of these implants through studies using a prospective design is mandatory.