Long-Term Bone Stability around 312 Rough-Surfaced Immediately Placed Implants with 2-12-Year Follow-Up

The purpose of this study was to retrospectively evaluate bone stability around implants with anodic oxidized surfaces and correlate this with variables compared in a previous study.

A total of 312 implants with anodic oxidized surfaces were separated from a pool of 1,187 implants placed immediately following tooth extraction. Radiographs made at the time of implant placement were compared to radiographs taken at 2-12 years' follow-up. An independent radiologist used the known distance (mm) between peaks of adjacent threads to calculate actual bone loss measurements. Measurements were evaluated by thread of bone fill on both the mesial and distal of each implant. If <50% of the thread had bone fill, the entire thread was assumed devoid of bone. All 312 implants were measured and a Mann-Whitney rank-sum test performed to test the significance of differences in mean bone loss relative to the factors studied.

The overall mean bone loss of the 312 implants was 0.4 mm (± 0. 80 mm) over a 2-12-year follow-up period with a mean duration of 7.4 years. Bone measurements in 95.5% of the implants were performed 6 years or more post-placement. Bone loss of <1.5 mm was found in 92% of implants. No statistically significant differences were seen in mean bone loss by gender, smokers versus non-smokers, tooth position (except for molars), or immediately loaded or immediate tooth replacement versus two-stage implants. Parameters that demonstrated statistically significant differences were splinted versus non-splinted implants, molars in maxilla versus mandible, regular (3.75-4.0 mm diameter) versus wide (5.0-6.0 mm diameter) platforms, and anodic oxidized surfaces versus other implant surfaces studied.

The mesial-distal bone loss of anodic oxidized surface (TiUnite) implants over a 2-12-year period (mean 7.4 years) was significantly less compared with machined implants placed with the same immediate implant placement protocol (0.4 mm vs 0.6 mm). Although several variables showed statistically significant differences in bone loss, the clinical significance could be questioned, as the maximum mean bone loss was 0.3 mm or less when comparing the various factors. The procedures used to place the implant and the strict maintenance protocol appear to be important aspects of the overall long-term success reported in this study in terms of measuring marginal bone loss around immediately placed implants.