Healing of implants installed in over- or under-prepared sites--an experimental study in dogs

OBJECTIVE To study bone healing at implants installed with different insertion torques. MATERIAL AND METHODS In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two implant sites were prepared at each side of the mandible. In the right side of the mandible, the distal sites were prepared conventionally, while the mesial sites were over-prepared by 0.2 mm. As a consequence, a final insertion torque of ~30 Ncm at the distal and a minimal insertion torque close to 0 Ncm at the mesial sites were obtained. In the left sides of the mandible, however, the recipient sites were underprepared by 0.3 mm resulting in an insertion torque of ≥ 70 Ncm at both implants. Cover screws were applied, and flaps sutured to fully submerge the experimental sites. After 4 months, the animals were sacrificed and ground sections obtained for histological evaluation. RESULTS The mineralized bone-to-implant contact was in the range of 55.2-62.1%, displaying the highest value at implants with ~30 Ncm insertion torque and the lowest value at the implant sites with close to 0 Ncm insertion torque. No statistically significant differences were revealed. Bone density was in the range of 43.4-54.9%, yielding the highest value at implants with ≥ 70 Ncm insertion torque and the lowest at the implant sites with close to 0 Ncm insertion torque. The difference between the sites of ~30 Ncm and the corresponding ≥ 70 Ncm insertion torque reached statistical significance. CONCLUSIONS Similar amounts of osseointegration were obtained irrespective of the insertion torque applied. Moreover, implants installed in sites with close to 0 Ncm insertion torque may properly osseointegrate as well

Increasing the Vertical Dimension of Occlusion: A Multicenter Retrospective Clinical Comparative Study on 100 Patients with Fixed Tooth-Supported, Mixed, and Implant-Supported Full-Arch Rehabilitations

This multicenter retrospective clinical study was aimed at comparing the effects of an increase in vertical dimension of occlusion (VDO) in patients with fixed rehabilitations. Expert clinicians retrospectively evaluated 100 patients treated with an increase of the VDO and fixed dental prostheses (FDPs) supported by teeth, implants, or both. The patients were divided into three study groups according to the type of support of restorations in posterior areas, as follows: partially edentulous patients with posterior teeth-supported rehabilitations and no implants in posterior segments (group A), partially edentulous patients with posterior mixed rehabilitations and at least one osseointegrated implant in posterior segments (group B), and completely edentulous patients with posterior implant-supported rehabilitations (group C). The new VDO was tested with mock-ups, temporary restorations, or removable appliances. The patients were followed up for at least 1 year after the delivery of final restorations. Clinical variables were collected retrospectively, such as presence of referred self-reported bruxism and temporomandibular joint or muscle symptoms before treatment, extension of the dental arches, increase in VDO, restorative materials, and functional complications. Descriptive statistics were analyzed; the three experimental groups were compared with one-way analysis of variance (ANOVA) followed by Tukey post hoc test for the quantitative variables and with logistic regression using the likelihood ratio test for the qualitative variables. Statistically significant differences were reported among the experimental groups for functional complications. Functional and prosthetic complications after the VDO increase were not frequent. Functional complications were mainly noticed in group C but usually were no longer evident after 2 weeks. No significant differences were found between groups in terms of prosthetic complications and self-reported bruxism