A retrospective radiographic study on the effect of natural tooth-implant proximity and an introduction to the concept of a bone-loading platform switch.

PURPOSE: The aim of this study was to evaluate the effect of tooth-implant proximity using an implant system with a double platform shift that was designed to load bone coronal to the implant-abutment cohort study was conducted between January 2008 and December 2009. The sample was composed of patients who had received at least one 5-mm-wide hydroxyapatite-coated single-tooth Bicon implant that had been placed adjacent to at least one natural tooth. Descriptive statistics and univariate and multivariate linear mixed-effects regression models, adjusted for multiple implants in the same patient, were utilized. The primary predictor variable was the horizontal distance between implant and adjacent tooth, and the primary outcome variable was the change in peri-implant bone levels over time. RESULTS: Two hundred six subjects who received 235 plateau root-form implants were followed for an average of 42 months. Tooth-implant distance ranged between 0 and 14.6 mm. Out of 235 implants, 43 implants were placed < 1 mm to an adjacent natural tooth on mesial and/or distal sides. The proximity of a plateau root-form implant was not associated with complications on the adjacent tooth such as bone loss, root resorption, endodontic treatment, pain, or extraction. The proximity of an adjacent tooth was not a risk factor for the failure of a plateau root-form implant. After adjusting for other covariates in a multivariate model, the proximity of a natural tooth did not have a statistically significant effect on peri-implant bone levels (P = .13). The extraction of an adjacent tooth was associated with a significant increase in peri-implant bone loss (P = .008). CONCLUSION: The placement of a plateau root-form implant with a sloping shoulder in close proximity to an adjacent tooth did not cause damage to that tooth or lead to bone loss or the failure of the implant.

Abutment design for implant-supported indirect composite molar crowns: reliability and fractography.

PURPOSE: To investigate the reliability of titanium abutments veneered with indirect composites for implant-supported crowns and the possibility to trace back the fracture origin by qualitative fractographic analysis. MATERIALS AND METHODS: Large base (LB) (6.4-mm diameter base, with a 4-mm high cone in the center for composite retention), small base (SB-4) (5.2-mm base, 4-mm high cone), and small base with cone shortened to 2 mm (SB-2) Ti abutments were used. Each abutment received incremental layers of indirect resin composite until completing the anatomy of a maxillary molar crown. Step-stress accelerated-life fatigue testing (n = 18 each) was performed in water. Weibull curves with use stress of 200 N for 50,000 and 100,000 cycles were calculated. Probability Weibull plots examined the differences between groups. Specimens were inspected in light-polarized and scanning electron microscopes for fractographic analysis. RESULTS: Use level probability Weibull plots showed Beta values of 0.27 for LB, 0.32 for SB-4, and 0.26 for SB-2, indicating that failures were not influenced by fatigue and damage accumulation. The data replotted as Weibull distribution showed no significant difference in the characteristic strengths between LB (794 N) and SB-4 abutments (836 N), which were both significantly higher than SB-2 (601 N). Failure mode was cohesive within the composite for all groups. Fractographic markings showed that failures initiated at the indentation area and propagated toward the margins of cohesively failed composite. CONCLUSIONS: Reliability was not influenced by abutment design. Qualitative fractographic analysis of the failed indirect composite was feasible.

The effect of implant size 5 × 8 mm on crestal bone levels around single-tooth implants.

BACKGROUND: There is substantial evidence supporting the strain-induced biologic response of bone to mechanical load. Stress-related factors, such as implant size, have been associated with changes in crestal bone levels on dental implants. The purpose of this study is to evaluate the effect of an implant size, specifically 5 mm wide × 8 mm long (5 × 8), on peri-implant bone levels. METHODS: A retrospective cohort study was conducted. The cohort was composed of patients who had ≥1 plateau root-form implant. Descriptive statistics, univariate and multivariate mixed-effects regression models, adjusted for multiple implants in the same patient were used to evaluate the correlation between 5 × 8 implants and other clinically relevant factors on crestal bone levels after insertion of single-tooth replacements. RESULTS: The cohort was composed of 81 individuals who received 326 implants. The average change in crestal bone levels (AvBL) for 5 × 8 maxillary and mandibular implants after 5.9 years of follow-up were -0.36 and -0.04 mm, respectively. In contrast, AvBL for mandibular implants not measuring 5 × 8 was -0.51 mm. Of several different local and systemic factors evaluated, including 10 different implant sizes, 5 × 8 mandibular implants were found to be significantly less likely to lose bone when compared with mandibular implants not measuring 5 × 8 (P = 0.047). CONCLUSIONS: Implants measuring 5 × 8 demonstrated statistically significantly less peri-implant bone loss in the posterior mandible. This finding indicated that a specific implant size may be involved in mandibular bone preservation. However, prospective multicenter clinical trials are needed to validate these findings.