Vertical Bone Augmentation with an Autogenous Block or Particles in Combination with Guided Bone Regeneration: A Clinical and Histological Preliminary Study in Humans.

BACKGROUND: Vertical ridge augmentation with the use of solid bone blocks or particulate bone autograft, exposed or covered by a nonresorbable expanded polytetrafluoroethylene (ePTFE) membrane, are well known in the literature and have been shown to be effective in treating bone atrophy. PURPOSE: The aim of our study was to assess the two techniques in respect to biological properties of transplanted bone in graft revascularization and bone remodeling in conjunction with dental implants. MATERIALS AND METHODS: Ten patients were treated within the study, with a total of 12 sites with posterior mandibular edentulous ridges with insufficient bone to allow implant placement. Bone regeneration was performed using autogenous intraoral block graft or autogenous particulate graft with an ePTFE barrier membrane. At 6-10 months, reentry surgery was performed; bone biopsies, including microscrews, were harvested; and implants were placed. RESULTS: Eleven sites out of 12 healed uneventfully. A mean height gain of 5.03 mm was achieved. Mean bone-to-implant contact and bone fill were assessed by means of histomorphometric analysis. The block specimens revealed a bone-to-implant contact of 42.34%, and the particulate grafts had a bone-to-implant contact of 26.62% (p < .012). Bone fill values reported were 68.32% and 48.28% (p < .019) for block specimens versus particulate grafts. CONCLUSIONS: The results clearly showed that both techniques were clinically successful for subsequent implant placement and prosthetic rehabilitation. The histological outcomes, including revascularization and bone remodeling, of the two techniques differed significantly. The block grafts outperformed the particulate grafts in terms of bone-to-implant contact and bone fill values; however, the morbidity associated with the donor site of the block must be considered.

Poly-D-L-Lactic Acid Membranes for Bone Regeneration.

PURPOSE: To histologically and histomorphometrically evaluate the biocompatibility and the biological properties of perforated and nonperforated poly-D-L-lactic acid (PDLLA) resorbable membranes, using a model of calvarial monocortical bone defects in domestic pigs. METHODS: A total of 6 10 × 10 × 10  mm circular calvarial bone defects were prepared in each of the 3 adult female large white domestic pigs and assigned to the following experimental groups: negative control, nonperforated membrane only, perforated membrane only, bone only, bone + nonperforated membrane, and bone + perforated membrane. The PDLLA membranes were fixed by PDLLA pins by means of an ultrasonic device. After 40 days, bone blocks containing the defects were harvested and histologically processed. RESULTS: A close contact between the PDLLA devices and the surrounding bone was found, and no trace of inflammatory tissue or signs of infection were detected. Bone regeneration occurred from the preexisting bone with a centripetal pattern. Incomplete bone filling was found in empty defects, whereas all sites filled with bone showed a complete bone formation, irrespectively of the presence and the type of membrane used. CONCLUSION: PDLLA membranes and pins showed to be highly biocompatible toward bone tissue and to do not interfere with the bone healing process of monocortical calvaria defects in domestic pigs. No adjunctive effect of PDLLA membranes, irrespectively of their perforated/nonperforated structure, could be evidenced in terms of bone regeneration under the present experimental conditions. Further studies are needed to investigate the regenerative potential of such devices in other clinically relevant models.

Early bone formation adjacent to oxidized and machined implant surfaces: a histologic study.

Various designs of dental implants representing different geometries and surface technologies are commercially available for patient treatment. However, data with regard to the biologic events that occur immediately after implant placement, regardless of the surface characteristic, are scarce. It has become a common procedure to perform immediate/early prosthetic loading rather than delayed loading. The goal of this study was to observe the early biologic events of peri-implant healing to understand the role of surface modifications in relation to the early phases of bone integration. The secondary goal was to observe the possible differences in the healing pattern at two oral implant surfaces differing in morphology and roughness (Ra, with Ra values ranging from 0.5 µm (machined surface; MS) to 1.5 µm (oxidized surface; OS). A total of 36 implants were placed in six foxhound dogs, equally divided between machined and oxidized surfaces. Three implants were positioned per hemimandible following a randomization scheme. Each animal was euthanized at a specific time point for histologic observation and histomorphometry: immediately after implant insertion and after 24 hours, 7 days, 15 days, 30 days, and 90 days. The study demonstrated an extremely low bone-implant contact (BIC) for both OS and MS implant surfaces during the first 15 days after implant placement (ranging from 12.9% to 26.9% independent of the implant surface). Increased BIC values were observed only in the 30- and 90-day specimens. The presence and the degradation of residual bone particles acted as centers for new bone formation, with osteoblasts lining osteoid tissue and subsequently woven bone independent of the implant surface characteristics. The bone-forming activity appeared strongly reduced after 30 days of healing and seemed to be complete only in the 90-day specimens, where abundant lamellar bone was evident. There is a continuing effort to develop improved titanium surfaces to achieve more rapid osseointegration and improve BIC, with the ultimate goal of applying occlusal load as early as possible. Since immediate or early implant loading is applied during and not after the first 15 days, the findings in the present study of an extremely low BIC and limited mineralized bone formation for both implant surfaces during the first 15 days after implant placement suggest that the surface roughness may not be a key factor for successful osseointegration of immediately or early loaded implants. Within the limits of this study, it can be stated that osseointegration follows a similar healing pattern with machined and oxidized implant surfaces.