Tomomichi Ozawa

Factors influencing secondary alveolar bone grafting in cleft lip and palate patients: prospective analysis using CT image analyzer.

Objective: To examine the effect of migration of the germ of the lateral incisor into the bone for eruption factors on bone bridge resorption. Methods: Twenty-five subjects who underwent secondary alveolar bone graft were enrolled. The volume of the alveolar bone grafts immediately after the operation (V1), bone bridge formation 6 months postoperatively (V2), and tooth (teeth) migration into the bone bridge (Vt) were measured using a computed tomography (CT) image analyzer. Based upon these measurements, the following points were examined: (1) the correlation between the tooth-occupied ratio (Rt = Vt/V2 × 100) and the ratio of bone bridge resorption (Rv = (V1 − V2)/ V1 × 100); and (2) comparison of the tooth-occupied ratio (Rt) and the ratio of bone bridge resorption (Rv) between the groups with and without the germ of the lateral incisor. Results: A significant negative correlation was found between Rv and Rt (p < .001). Comparison of Rv and Rt between the groups with and without a germ of the lateral incisor revealed that both indices were significantly higher in the former group than the latter one (p < .05). Conclusion: In cleft lip and palate patients with a germ of the lateral incisor, it is beneficial to carry out secondary bone grafting to the alveolar cleft at the age of 5 to 7 years, preceding eruption of the canine, in order to form a good bone bridge that will facilitate eruption of the lateral incisor and subsequent normal dentition and occlusion.

Hydroxyapatite coating for titanium fibre mesh scaffold enhances osteoblast activity and bone tissue formation

This study investigated the bone regeneration properties of titanium fibre mesh as a tissue engineering material. A thin hydroxyapatite (HA) coating on the titanium fibre web was created using the developed molecular precursor method without losing the complex interior structure. HA-coated titanium fibre mesh showed apatite crystal formation in vitro in a human osteoblast culture. Titanium fibre mesh discs with or without a thin HA coating were implanted into rat cranial bone defects, and the animals were killed at 2 and 4 weeks. The in vivo experience revealed that the amount of newly formed bone was significantly higher in the HA-coated titanium fibre mesh than in the non-coated titanium fibre mesh 2 weeks after implantation. These results suggest that thin HA coating enhances osteoblast activity and bone regeneration in the titanium fibre mesh scaffold. Thin HA-coating improved the ability of titanium fibre mesh to act as a bone regeneration scaffold.

Vertical distraction of a free vascularized osteocutaneous scapular flap in the reconstructed mandible for implant therapy

This paper describes a case of vertical distraction osteogenesis of a free vascularized osteocutaneous scapular flap in the reconstructed mandible before implant therapy. The patient was a 67-year-old woman with squamous cell carcinoma of the right lower gingiva. She underwent segmental mandibulectomy for tumor ablation and reconstruction with an osteocutaneous scapular flap. The distraction protocol, clinical course and implant therapy are presented. Through this procedure, the bone height of the scapular graft increased by 10mm. Implants with adequate length could be placed in the distracted area. Two years after masticatory loading, the condition of these implants was stable. Vertical distraction osteogenesis of the scapular flap was considered effective when performed before implant therapy, to facilitate postoperative functional and esthetic restoration after tumor resection.

Development of a biointegrated mandibular reconstruction device consisting of bone compatible titanium fiber mesh scaffold.

Coating biomaterials with a thin hydroxyapatite (HA) was proven effective in enhancing bone compatibility. Segmental bone defects are considered as the most difficult defect to repair in bone regeneration therapy. We developed submicron-thin HA-coated titanium fiber mesh scaffolds to reconstruct immediately loaded segmental mandibular defects and evaluated their bone compatibility in vitro and in vivo. Human osteoblasts attachment, proliferation, and osteocalcin expression in non- and HA-coated scaffolds were evaluated. A 10-mm long segmental bone defect in a rabbit mandibular bone was reconstructed with non- or HA-coated scaffolds, which were removed at 9 and 21 weeks, to evaluate the mechanical strength of the bone-scaffold connection and the bone formation around the scaffold. Expression of osteocalcin was greater in HA-coated scaffolds. In vivo bone formation in HA-coated scaffolds was greater than that in non-coated scaffolds at 21 weeks. Newly formed bone in HA-coated scaffolds mostly restored bone continuity. Scanning electron microscopy identified strong integration of the bone and HA-coated scaffolds. The mechanical strength of the bone-scaffold connection was 3-fold greater in HA-coated scaffolds than that in non-coated scaffolds. These results suggest that a thin HA-coated titanium fiber mesh scaffold is a bone-compatible mandibular reconstruction device in immediately loaded segmental defects.

Osteosynthesis and simultaneous irregular trifocal distraction osteogenesis for segmental mandibular defect after tumor ablative surgery: a case report

OBJECTIVE This paper describes a case of secondary mandibular bone reconstruction performed to place dental implants. Osteosynthesis and simultaneous irregular trifocal distraction osteogenesis were documented. PATIENT The patient was a 51-year-old man with recurrent ameloblastoma of the mandible. Segmental mandibulectomy for tumor ablation and immediate mandibular reconstruction were performed. Because the volume of reconstructed bone was insufficient to place dental implants, trifocal distraction osteogenesis (vertical and horizontal distraction osteogenesis) was performed. Because the mandible had lost its continuity, osteosynthesis was performed simultaneously. RESULTS Through this procedure, the bone was well augmented. Absorption of the distracted bone was not seen. Adequate-length implants were placed. CONCLUSION Irregular trifocal distraction osteogenesis synchronized with osteosynthesis shortened the treatment period and produced stable bone augmentation for placement of dental implants. Therefore, this procedure could be indicated for complicated segmental mandibular bone defects.

Mandibular reconstruction using 2-step bone transport in an irradiated cancer patient with type 2 diabetes mellitus

This report describes mandibular reconstruction using a 2-step bone transport technique in a cancer patient with type 2 diabetes mellitus (DM) who received radiotherapy before ablative surgery. The bone, measuring 90 mm in length with the mandibular curvature and good alveolar form, was regenerated using a plate-guided method. Three implants were placed 21 months after completion of the first distraction and 14 months after the second distraction. These implants integrated successfully and have remained stable more than 2 years after loading. The results suggest that mandibular reconstruction using bone transport is possible after segmental osteotomy in irradiated cancer patients with DM, although a long treatment period is required.

Implant Stability Development of Photofunctionalized Implants Placed in Regular and Complex Cases: A Case-Control Study.

PURPOSE The objective of this study was to compare the rate of implant stability development of as-received and photofunctionalized dental implants in regular and complex cases. MATERIALS AND METHODS Forty-nine implants (24 as-received and 25 photofunctionalized) placed in regular or complex cases (simultaneous guided bone regeneration, sinus elevation, or fresh extraction sockets) were studied. Photofunctionalization was performed by ultraviolet (UV) treatment of implants for 15 minutes using a photo device immediately prior to placement, and the generation of superhydrophilicity was confirmed. Implant stability was evaluated by measuring the implant stability quotient (ISQ) at placement (ISQ1) and at stage-two surgery (ISQ2). The rate of implant stability development was evaluated by calculating the osseointegration speed index (OSI), defined as the ISQ increase per month ([ISQ2-ISQ1]/healing time in months). The percentage of innate bone support at placement was evaluated clinically and radiographically. RESULTS The average OSI was considerably greater for photofunctionalized implants (3.7 ± 2.9) than for as-received implants (0.0 ± 1.0). The OSI in complex cases was 4.2 ± 3.2 for photofunctionalized implants and 0.2 ± 0.9 for as-received implants. The OSI in cases with simultaneous sinus elevation was 5.5 ± 3.5 for photofunctionalized implants and 0.2 ± 1.1 for as-received implants. Photofunctionalized implants showed significantly higher ISQ2 values than as-received implants. Photofunctionalized implant ISQ2 values were greater than 60, regardless of primary stability and innate bone support at placement. In multivariate analysis including the effects of photofunctionalization, age and sex of patients, and diameter and length of implants, photofunctionalization showed the strongest influence on the OSI for both regular and complex cases, while other factors influenced the OSI only in certain conditions. CONCLUSION Photofunctionalization accelerated the rate and enhanced the final level of implant stability development compared with as-received implants, particularly for implants placed into poor-quality bone and other complex cases. Photofunctionalization was a stronger determinant of implant stability than all the other tested implant- and host-related factors.

Effects of Ultraviolet Photofunctionalization on Bone Augmentation and Integration Capabilities of Titanium Mesh and Implants.

PURPOSE Ultraviolet (UV)-mediated photofunctionalization has earned considerable attention for the enhancement of the biologic capabilities of titanium. The effects of photofunctionalization on bone augmentation and gap closure were examined using titanium implants and mesh in a rat femur model. MATERIALS AND METHODS An acid-etched titanium implant (4-mm length, 1-mm diameter) was placed in the gluteal tuberosity that resembles a knife-edge-like edentulous ridge. The lower half of the implant was located in a 2-mm-diameter defect created in the bone without cortical bone support; the upper half was exposed and covered with a titanium mesh to provide augmentation space. After 12 and 24 days of healing, specimens were subjected to microcomputed tomography (micro-CT)- and histology-based bone morphometry in three zones of analysis: augmentation, cortical bone-implant gap, and bone marrow. A biomechanical push-in test was performed to examine the strength of bone-implant integration. Photofunctionalization was performed by treating titanium implants and mesh with UV light for 12 minutes. RESULTS Photofunctionalized titanium mesh and implants were hydrophilic, whereas untreated controls were hydrophobic. Bone volume was significantly greater in photofunctionalized implants and mesh than in untreated implants in all zones on days 12 and 24. Bone-to-implant contact of photofunctionalized implants was greater than that of untreated implants, not just in the bone marrow but also in the gap and augmented zones. The strength of osseointegration was three times greater for photofunctionalized implants than for untreated implants. CONCLUSION Use of photofunctionalized titanium mesh and implants effectively enhanced vertical bone augmentation, cortical bone-implant gap closure, and osseointegration without innate bone support.

Effect of Photofunctionalization on Early Implant Failure

PURPOSE This study retrospectively evaluated the effects of bone density, staging strategy, implant stability, healing process, implant length, surface type, and photofunctionalization on early implant failure. MATERIALS AND METHODS Consecutive study samples at Yokohama City University Hospital were analyzed for their early implant failure potentially influenced by patient-, surgical protocol-, and implant-related factors. Through the screening process using univariate analysis for those factors, candidate influential factors such as bone density, staging strategy, the level of initial implant stability, postoperative wound breakdown, the length of implants, the surface type of implants, and use or nonuse of photofunctionalization were selected as independent variables in forward multivariate logistic regression analysis. The odds ratio (OR) for candidate factors was calculated. RESULTS A total of 563 implants placed in 219 patients from 2005 to 2017 were analyzed for their early implant failure. Stepwise logistic regression analysis finally identified postoperative wound breakdown (OR = 0.21) and the use of photofunctionalization (OR = 0.30) that significantly reduced the risk of early implant failure (P < .01 and P < .05, respectively). The implant failure rate was 10.0% with postoperative wound breakdown and 1.0% without it, whereas it was 4.3% without photofunctionalization and 1.3% with it. CONCLUSION Among various patient-, surgical protocol-, and implant-related factors, the absence of postoperative wound breakdown and use of photofunctionalization significantly reduced the risk of early implant failure. It was notable that photofunctionalization, a unique, chairside measure to improve implant surfaces, was effective exclusively among implant-related factors.