Factors influencing implant and prosthesis survival in zygomatic implant-supported fixed rehabilitation: a retrospective study.

BACKGROUND: The aim of this retrospective study was to evaluate mid-term implant and prosthesis survival in patients with edentulous atrophic maxillae submitted to zygomatic implant-supported fixed rehabilitation and to identify possible related risk factors. METHODS: Data were collected from records of patients with edentulous atrophic maxillae, in good general health and who were rehabilitated by means of acrylic resin full-arch screw-retained prosthesis supported by at least one zygomatic implant, between the years of 2006-2017. Implant and prosthesis survival rates were calculated. The association between implant and prosthesis loss and quantitative and qualitative variables of interest was verified with t tests and Fisher's exact tests, respectively. For the significant variables in the latter, odds ratio and 95% confidence intervals were additionally calculated. RESULTS: The sample comprised 66 patients in whom 171 zygomatic implants were placed to support maxillary screw-retained full-arch prostheses. Implant and prosthesis survival rates of 94.15% and 92.4%, respectively, were observed in a mean of 3.6 years of follow-up (up to 11.7 years). Implant loss was 4.33 more likely to occur when adverse events were recorded after the procedure of implant placement (P = 0.026) and 10.31 more likely to occur in implants that had their prosthesis repaired during follow-up visits (P = 0.004). Prosthesis loss was 22.00 times more likely to occur when implants were previously lost (P < 0.001). All prostheses that were considered as failures (i.e. were replaced) had been previously submitted to laboratory repair at some point during follow-up. CONCLUSIONS: Zygomatic implant rehabilitation demonstrated to be a reliable method with good mid-term results. The occurrence of post-surgical adverse events and need for laboratory repair of the prosthesis were found to be significant risk factors for implant loss. Previous implant loss was significantly associated with prosthesis loss. These risk factors may be prevented by means of detailed planning of the rehabilitation to be carried out, including post-operative care of the patients, so that treatment success using zygomatic implants can be achieved.

Discrepancies in marginal and internal fits for different metal and alumina infrastructures cemented on implant abutments.

Cemented crowns are increasingly being used on dental implants instead of on screw-retained prostheses because of the reliability of internal Morse taper implant-abutment connections. However, there is a lack of information on the fit of metal ceramic and premachined alumina infrastructures. Therefore, the aim of this study was to evaluate the marginal and internal fits of different metal and alumina infrastructures cemented on universal post abutments. A total of 45 abutments (6 mm in height and 3.3 mm in diameter) were divided into five groups on the basis of their infrastructure material: cobalt-chromium (CoCr), nickel-chromium (NiCr), nickel-chromium-molybdenum-titanium (NiCrMoTi), gold (Au), and premachined alumina. The alumina group showed marginal overextension, and the Au group showed the highest discrepancy in marginal fit among the metal alloys. The CoCr and alumina groups showed the lowest discrepancies in internal fit. In conclusion, the alumina cylinders exhibited the best internal fit, despite their horizontal overextension. Among the metal alloys, CoCr exhibited the best fit at critical regions, such as the cervical and occlusal areas.

Implant stability measurements of two immediate loading protocols for the edentulous mandible: rigid and semi-rigid splinting of the implants.

AIM: Primary and secondary stabilities of immediately loaded mandibular implants restored with fixed prostheses (FP) using rigid or semi-rigid splinting systems were clinically and radiographically evaluated. METHODS: Fifteen edentulous patients were rehabilitated using hybrid FP; each had 5 implants placed between the mental foramens. Two groups were randomly divided: group 1-FP with the conventional rigid bar splinting the implants and group 2-semi-rigid cantilever extension system with titanium bars placed in the 2 distal abutment cylinders. Primary stability was evaluated using resonance frequency analysis after installation of the implant abutments. The measurements were made at 3 times: T0, at baseline; T1, 4 months after implant placement; and T2, 8 months after implant placement. Presence of mobility and inflammation in the implant surrounding regions were checked. Stability data were submitted to statistical analysis for comparison between groups (P < 0.05). RESULTS: Implant survival rate for the implants was of 100% in both groups. No significant differences in the mean implant stability quotient values were found for both groups from baseline and after the 8-month follow-up. CONCLUSION: The immediate loading of the implants was satisfactory, and both splinting conditions (rigid and semi-rigid) can be successfully used for the restoration of edentulous mandibles.