Motohiro Munakata

Lateral Bone Window Closing Technique with Poly-L-Lactic Acid (PLLA) Membrane in the Augmentation of the Maxillary Sinus without Grafting Material: Evaluation of Bone Healing in a Rabbit Model.

BACKGROUND When augmenting the maxillary sinus without grafting material, the method used to cover the bony window is a subject of debate. PURPOSE The purpose of this study was to evaluate the poly-L-lactic acid (PLLA) membrane as closing material of the lateral window in a maxillary sinus augmentation without bone grafting. MATERIALS AND METHODS Augmentation of the maxillary sinus without grafting material and installation of titanium screws that fix the Schneiderian membrane were performed in 18 Japanese male white rabbits. The bony window was covered with a collagen membrane or PLLA membrane or no membrane. The animals were sacrificed at 4 or 8 weeks. New bone volume was calculated radiologically using microcomputed tomography (micro-CT). The samples were analyzed histologically after toluidine blue staining. RESULTS No significant differences were observed in the new bone volume, as measured by micro-CT. However, histomorphometric analysis demonstrated the superiority of the PLLA membrane in new bone formation compared with the collagen membrane. CONCLUSION The PLLA membrane is a suitable material to be applied for tissue regeneration in this animal model.

Influence of Bisphosphonates on Implant Failure Rates and Characteristics of Postmenopausal Woman Mandibular Jawbone

Rehabilitation of oral function using dental implants is clinically effective and highly predictable. Both bone quantity and quality at the implant site affect the success of the procedure. However, the effect of bisphosphonate (BP) use on mandibular bone quality has not been well documented. The purpose of this retrospective cohort study was to evaluate the bone mineral density (BMD) and cortical thickness of the mandible, as well as the influence of BP use on early implant failure. Twenty-five female patients (≥60 years of age) were selected from among 93 candidates with partially edentulous posterior mandibles. Eleven patients had received BP therapy using alendronate (BP group), and 14 patients had received alternate therapy (non-BP group). Cortical and trabecular BMD was measured using quantitative computed tomography. Cortical thickness was measured using computed tomography. The BMDs and cortical thicknesses of the two groups were compared. The results were as follows: (1) Cortical BMD was significantly higher in the BP group, (2) trabecular BMD was not affected by BP use, and (3) Cortical thickness was affected by the duration of BP use. These results indicate that BP use affects the quality and quantity of the cortical bone in the partially edentulous posterior mandible of patients with osteoporosis, which should be considered prior to treatment with dental implants in patients taking BPs.

Histological and Histomorphometrical Determination of the Biogradation of β-Tricalcium Phosphate Granules in Maxillary Sinus Floor Augmentation: A Prospective Observational Study

Introduction: We have recently used highly pure &bgr;-TCP (beta-tricalcium phosphate) as the bone grafting material to avoid highly invasive autogenous bone grafting. We evaluated the osseoconduction potential of highly pure &bgr;-TCP in sinus augmentation surgery treatment. Materials and Methods: The study group comprised 13 patients who underwent maxillary sinus floor augmentation with &bgr;-TCP alone. Seven patients underwent sinus augmentation and implant placement simultaneously. Six patients were treated with a staged approach. Six months after surgery, specimens were obtained from 7 patients (for lateral biopsy) and 6 patients (for vertical biopsy). Results: Histological and histomorphometrical analysis showed a mean bone proportion of 30.8% (vertical) and 12.0% (lateral) for new bone formation and good integration of the &bgr;-TCP. New bone formation was lower in the lateral biopsy specimens than in the vertical. Conclusion: Highly pure &bgr;-TCP is a safe bone-grafting material with superior osteoconductive properties. Histologic and radiographic examinations indicate that &bgr;-TCP is slowly resorbed, which results in unresorbed graft material remaining even 6 months after the procedure, and that new bone replacement occurs slowly for approximately 1 year.

Rehabilitation of a Bilateral Maxillectomy Patient with a Free Fibula Osteocutaneous Flap and with an Implant-Retained Obturator: A Clinical Report

A 47-year-old man underwent surgical resection and reconstruction with a fibula osteocutaneous flap. After the surgery, a surgical obturator was placed and adjusted. After flap healing, a conventional obturator was fabricated with polymethyl methacrylate resin and retained by the anatomical undercuts around the reconstructed fibula bone flap and the posterior part of the defect. As the defect shape changed with time, a second conventional obturator was fabricated and fitted. No further recurrence of myoepithelioma was observed for 2 years, and the patient was satisfied with the obturator during mastication and speech; however, despite having no major complaints, the patient found it difficult to chew on the right side, and the obturator was displaced slightly downward when the mouth was opened wide and shifted when chewing hard and sticky food. Thus, an implant-retained obturator was suggested to provide better retention and stability. Four dental implants were therefore placed into the fibula bone, although one did not osseointegrate because either primary stability was insufficient or overload was affected in the nonloaded implant environment and was replaced. After fitting custom abutments with a magnet, an implant-retained obturator was placed, and the patient was satisfied with the outcome. During 3 years of follow-up, no issues were noted with the implant bodies, abutments, obturator, or reconstructed site. The conventional obturator was displaced slightly downward when the patient opened his mouth wide, and it shifted when chewing hard and sticky food because there was limited fibula bone at the reconstruction site and more available posteriorly. For better retention and stability, the implant-retained obturator was fabricated with a custom abutment and magnetic retention. The patient was satisfied with the results, as improved implant retention increased the stability of the prosthesis. This clinical report describes the rehabilitation of a bilateral maxillectomy patient with a free fibula osteocutaneous flap and an implant-retained obturator. The patients oral functions were improved when the prosthesis was stabilized by means of dental implants and custom abutments.

The Maxillary Sinus Floor Elevation Using a Poly-L-Lactic Acid Device to Create Space Without Bone Graft: Case Series Study of Five Patients

Maxillary sinus floor elevation using autologous or alloplastic bone grafting is often performed for implant treatment of maxillary molars; however, issues related to the donor site and complications such as infection have been reported. We performed maxillary sinus floor elevation using poly-L-lactic acid (PLLA) as a space-making material in patients with an insufficient bone mass (<3 mm) for simultaneous implantation between the alveolar crest and floor of the maxillary sinus and evaluated the newly formed bone. Conventional antrostomy of the maxillary sinus from the lateral wall was performed, and PLLA was placed on the floor of the maxillary sinus after elevating the sinus membrane. Six months after surgery, the bone mass and density were measured using quantitative computed tomography, and histological evaluation was performed. No complications were recorded. Radiological findings showed a bone-like radiopaque appearance, and histological examination revealed new bone formation in all patients. In cases with insufficient bone mass prior to simultaneous implant placement, this method of maxillary sinus augmentation allows for sufficient bone augmentation without bone grafting.

Occurrence Regions and Sites of Peri-implant Inflammation With Bone Resorption in Partially-edentulous Patients

Aim: The aim of this study was to clarify the occurrence regions and sites of peri-implant bone resorption and inflammation in partially-edentulous patients. Methods: Five hundred one partially-edentulous patients with 738 implants in function for more than 5 years were included in this study for the evaluation of the bone resorption by using dental radiograph and probing. Considering physiological bone remodeling, the mean mesio-distal bone resorption around the implant was measured on dental radiograph. Results: In 65 patients (13.0% of the total patients) with 76 implants (10.3% of the total implants), peri-implant bone resorption was identified. The mean functional loading time of these implants was 8.4 years. Occurrence regions were frequently found in the molar regions in maxilla (15.4%) and the molar region in mandible (10.0%) In these leisions detected radiologically, the bleeding on probing was seen in 95.2% of the buccal sites in mandibular molar regions, 70.0% of the palatal sites in maxillary molar regions and 56.7% of the buccal sites in maxillary molar regions with statistically significant differences. Conclusion: From the limitation of the information in this study, it was concluded that the sites that tend to be vulnerable to peri-implant inflammation were the buccal site in mandible, and the buccal and palatal sites in maxilla.