The purpose of this study is to estimate the magnitude of crestal bone loss and to identify factors associated with changes in crestal bone height following placement of dental implants. This was a retrospective cohort study, consisting of a sample derived from the population of patients who had at least 1 dental implant placed in a community practice over a 10-year period. A total of 11 predictor variables were grouped into demographic, related health status, anatomic, implant-specific, and operative categories. The primary outcome variable was a change in crestal bone height (mm) over the course of follow-up. The secondary outcome variable was crestal bone loss at 1 year grouped into 2 categories (bone loss >1.5 mm and ≤1.5 mm). Univariate and multivariate regression mixed-effects models were developed to identify variables associated with crestal bone level changes over time. P values ≤.05 were considered statistically significant. The study sample was composed of 85 subjects who received 148 implants. The mean change of the crestal bone was −2.1 ± 1.5 mm (range = −12.5 to 0.5 mm; median = −1.77 mm). In the multivariate model, none of the variables studied were statistically associated with mean crestal bone loss. Among 84 (66.1%) implants with bone loss >1.5 mm within 1 year, no variables were associated with bone loss in the multivariate model. Of the 11 predictor variables evaluated in this study, none were statistically significant with regard to an increased risk for crestal bone loss or for excessive bone loss within the first year after implant placement.

Excessive crown-implant ratios have been cited in the literature as being detrimental to long-term implant survival. However, unfavorable crown-implant ratios have not yet been established. The primary aim of this study was to determine the crown-implant ratios of single-tooth implant-supported restorations on short-length implants in a clinical practice, and to evaluate the health of these implants via mesial and distal first bone-to-implant contact levels. Additionally, the relationship between crown-implant ratios and proximal first bone-to-implant contact levels will be evaluated. In this retrospective cohort study, the cohort was composed of 194 patients who possessed at least 1 single 5.7 mm or 6 mm length plateau design implant-supported restoration that had been surgically placed between February 1997 and December 2005. A chart review was performed to acquire the most recent radiographs in which both the entire crown and the implant were visible. The length of the crown and implant was measured directly from the radiographs using consistent magnification to calculate the crown-implant ratio. Mesial and distal first bone-to-implant contact levels were measured using 3 times magnification and were mathematically corrected for distortion. The last available radiograph was used to measure bone levels. Follow-up time was calculated from the day of implant placement to the date of the last available radiograph. Statistical analyses with analysis of variance mixed models were used. Data from 309 single implant-supported fixed restorations were tabulated and included in the study. The mean (SD) follow-up time was 20.9 (23.2) months, with a range of 15.6 to 122.8 months. The mean crown length (SD) was 13.4 (2.6) mm, with a range of 6.2 to 21.7 mm. The mean (SD) crown-implant ratio was 2.0 (0.4) and ranged from 0.9 to 3.2. The average mesial and distal first bone-to-implant contact levels (SD) measured from the radiographs were −0.2 (0.7) mm and −0.2 (0.9) mm, respectively. No statistically significant relationship was observed between increasing crown-implant ratios and decreasing mesial and distal first bone-to-implant contact levels around the implant with P values of .94 and .57, respectively. In this investigation, mesial and distal first bone-to-implant contact levels on short-length implants fall within the established guidelines for success. Also, there are no associations between crown-implant ratios and first bone-to-implant contact levels.

The use of mandibular subperiosteal implants was first reported by Dahl in the 1940s. It was followed by a more comprehensive report by Goldberg and Gershkoff, who published the first case series in the United States. We describe a case of an orocutaneous fistula that developed secondary to a chronic infection attributed to a failing subperiosteal implant. Elemental analysis of the metal framework revealed an implant composed of mainly a cobalt-chromium alloy. Cobalt, which was frequently used in subperiosteal implant manufacturing, is associated with a higher corrosion rate than other metals and is no longer used to fabricate subperiosteal implants. The strength of subperiosteal implants is their ability to be used in a mandible with an atrophic alveolar ridge. Unfortunately, this feature of the hardware is also its weakness in that reconstructive procedures after their removal are difficult. The failing subperiosteal implant in our patient was subsequently removed, and primary closure of the intraoral wound and extraoral fistula as well as resolution of the patient's symptoms was obtained with no lasting complications.

Given the predictability of dental implant success, the attention of the scientific community is moving from descriptions of implant success toward a more detailed analysis of factors associated with implant failure. The purposes of this study were (1) to estimate the 1- and 5-year survival of Bicon® dental implants and (2) to identify risk factors associated with implant failure in an objective, statistically valid manner. To address the research purposes, we used a retrospective cohort study design and a study sample composed of patients who had one or more implants placed. The predictor variables were grouped into the following categories: demographic, health status, anatomic, implant fixture-specific, prosthetic, perioperative, and ancillary variables. The major outcome variable of interest was implant failure defined as implant removal. Overall implant survival was estimated using the Kaplan–Meier analysis. Risk factors for implant failure were identified using the Cox proportional hazard regression models. The study sample was composed of 677 patients who had 677 implants randomly selected for analysis. The overall 1- and 5-year survival of the Bicon implant system was 95.2% and 90.2%, respectively. After adjusting for other covariates in a multivariate model, both tobacco use ( P = .0004) and single-stage implant placement ( P = .01) were statistically associated with an increased risk for failure. The results of these analyses suggest that the overall survival of the Bicon dental implant is comparable with other current implant systems. In addition, after controlling for covariates, we identified 2 exposures associated with implant survival, tobacco use and implant staging. Of interest, both of these exposures are under the clinician’s control.