Influence of Different Implant Types on Bone Levels After Healing and Peri-implant Tissue Reactions Following Peri-implantitis: A Preclinical Study.

This study evaluated the influence of different implant types on (1) radiographic marginal bone levels after healing and (2) radiographic and histomorphometric tissue levels and characteristics following ligature-induced peri-implantitis. Four implant types (Standard Plus, Straumann [S]; NobelReplace Tapered, Nobel Biocare [N]; In-Kone Universal, Global D [I]; and twinKon, Global D [T]) were randomly placed in the edentulous healed mandibular ridge of six dogs (T0), for a total of 57 implants placed. After 10 weeks, a peri-implantitis was ligature-induced (T1). After 12 weeks, biopsy samples were processed for histomorphometric analysis (T2). Standardized radiographs were taken at T0, T1, and T2 for imaging analysis. Statistical analysis was performed using mixed-effects linear modeling. After healing (T1), the radiographic marginal bone level was more coronal for implants I, T, and S compared to N. Following peri-implantitis (T2), the histologic marginal bone level was more coronal for implants I, T, and S compared to N, and for implants I and T compared to S. Also at T2, the radiographic marginal bone level was more coronal at implants I, T, and S compared to N. Implant type may influence bone remodeling during healing and bone loss during the early stages of experimental peri-implantitis.

4 mm long vs longer implants in augmented bone in posterior atrophic jaws: 1-year post-loading results from a multicentre randomised controlled trial.

PURPOSE: To evaluate whether 4.0 mm short dental implants could be an alternative to augmentation with xenographs in the maxilla and placement of at least 10.0 mm long implants in posterior atrophic jaws. MATERIALS AND METHODS: A group of 40 patients with atrophic posterior (premolar and molar areas) mandibles with 5.0 mm to 6.0 mm bone height above the mandibular canal and 40 patients with atrophic maxillas having 4.0 mm to 5.0 mm below the maxillary sinus, were randomised according to a parallel group design to receive between one and three 4.0 mm long implants or one to three implants of at least 10.0 mm long in augmented bone, at two centres. All implants had a diameter of 4.0 mm or 4.5 mm. Mandibles were vertically augmented with inter-positional equine bone blocks and resorbable barriers. Implants were placed 4 months after the inter-positional grafting. Maxillary sinuses were augmented with particulated porcine bone via a lateral window covered with resorbable barriers, and implants were placed simultaneously. Implants were not submerged and were loaded after 4 months with provisional screw-retained reinforced acrylic restorations replaced after another 4 months by definitive screw-retained metal-composite prostheses. Patients were followed up to 1 year post-loading. Outcome measures were: prosthesis and implant failures, any complication, and peri-implant marginal bone level changes. RESULTS: Three patients dropped out; one from the maxillary augmented group, one from the mandibular augmented group, and one from the maxillary short implant group. In six augmented mandibles (30%) it was not possible to place implants of at least 10.0 mm, so shorter implants were placed instead. In mandibles, one implant from the augmented group failed vs two 4.0 mm implants in two patients from the short implant group. In maxillae, three short implants failed in two patients vs seven long implants in four patients (two long implants and one short implant dropped into the maxillary sinus). Two prostheses on short implants (one mandibular and one maxillary) were placed at a later stage because of implant failures, vs six prostheses (one mandibular and five maxillary) at augmented sites (one mandibular prosthesis not delivered, three maxillary prostheses delivered with delays, one not delivered, and one failed) at augmented sites. In particular, three patients in the augmented group (one mandible and two maxillae) were not wearing a prosthesis. There were no statistically significant differences in implant failures (P (chi-square test) = 0.693; difference in proportion = 0.03; CI 95% -0.11 to 0.17) or prostheses failures (P (chi-square test) = 0.126; difference in proportion = 0.10; CI 95% -0.03 to 0.24). At mandibular sites, nine augmented patients were affected by complications vs two patients treated with short implants (P (chi-square test) = 0.01; difference in proportion = 0.37; CI 95% 0.11 to 0.63), the difference being statistically significant. No significant differences were found for maxillae: nine sinus-lifted patients vs four short implant patients were affected by complications (P (chi-square test) = 0.091; difference in proportion = 0.25; CI 95% -0.03 to 0.53). At 1-year post-loading, average peri-implant bone loss was 0.51 mm at 4 mm long mandibular implants, 0.77 mm at 10 mm or longer mandibular implants, 0.63 mm at short maxillary implants and 0.72 mm at long maxillary implants. The difference was statistically significant in mandibles (mean difference -0.26 mm, 95% CI -0.39 to -0.13, P (ANCOVA) < 0.001), but not in maxillae (mean difference -0.09 mm, 95% CI -0.24 to 0.05, P (ANCOVA) = 0.196). CONCLUSIONS: One year after loading 4.0 mm long implants achieved similar results, if not better, than longer implants in augmented jaws, but were affected by fewer complications. Short implants might be a preferable choice over bone augmentation, especially in mandibles, since the treatment is less invasive, faster, cheaper, and associated with less morbidity. However, 5 to 10 years post-loading data are necessary before making reliable recommendations.

Soft Tissue and Marginal Bone Adaptation on Platform-Switched Implants with a Morse Cone Connection: A Histomorphometric Study in Dogs.

The purpose of this study was to investigate peri-implant tissue adaptation on platform-switched implants with a Morse cone-type connection, after 3 and 12 weeks of healing in dogs. Ten weeks after mandibular premolar extractions, eight beagle dogs received three implants each. At each biopsy interval, four animals were sacrificed and biopsies were processed for histologic analysis. The height of the peri-implant mucosa was 2.32 mm and 2.88 mm, respectively, whereas the bone level in relation to the implant platform was -0.39 mm and -0.67 mm, respectively, after 3 and 12 weeks of healing. Within the limits of the present study, platform-switched implants exhibited reduced values of biologic width and marginal bone loss when compared with previous data.

Early Periimplant Tissue Healing on 1-Piece Implants With a Concave Transmucosal Design: A Histomorphometric Study in Dogs.

INTRODUCTION: The purpose of our study was to investigate the early healing phase of marginal bone and soft tissues around unloaded 1-piece implants with a concave transmucosal design, in a dog model. METHODS: Twenty-four 1-piece implants with a concave transmucosal neck were inserted 1 mm subcrestally in the mandibular ridge of 8 beagle dogs. Four animals were sacrificed after 3 and 12 weeks of healing. Histomorphometric analysis was performed to measure the height of the periimplant tissues. RESULTS AND DISCUSSION: The overall height of the periimplant mucosa was, respectively, 2.67 and 2.52 mm, after 3 and 12 weeks. In the connective tissue, a soft tissue O-ring seal was observed in the healing area provided by the transmucosal concavity, after 12 weeks. The location of the first bone-to-implant contact facing the implant shoulder was 0.00 and +0.18 mm, respectively, after 3 and 12 weeks of healing. Some bone apposition occurred on the implant shoulder during the healing. CONCLUSION: Within the limits of the present study, a concave transmucosal design in 1-piece implants was associated with a short vertical value of biological width and promoted a mechanical interlocking of the implant body at the connective tissue and marginal bone levels.