Yoshiaki Arai

Immediate implant loading following computer-guided surgery

PURPOSE The aim of this study was to develop and apply a new method for easy intraoperative adjustment of a provisional fixed full-arch restoration, in order to allow immediate implant loading following computer-guided surgery, regardless of any implant positioning errors compared to the virtual planning. METHODS In accordance with the NobelGuide™ protocol, a provisional restoration for immediate loading of six maxillary implants was prepared prior to surgery. Because small shifts between the planned and the actual implant positions were to be expected, the provisional restoration was not fabricated directly on temporary cylinders as a conventional one-piece superstructure, but was divided into two portions: six custom made abutments and a long span fixed restoration which were left unconnected. After implantation, the custom abutments were attached to the six implants to be immediately loaded, and the superstructure was cemented simultaneously to all abutments using dual cure resin cement. After the excess cement was cleaned and polished, the superstructure was then reseated. Passive fit was achieved between implants and the superstructure. CONCLUSION The superstructure described in this article can be easily seated and adjusted to accommodate any possible shifts in implant positioning occurring during computer-guided surgery. Through this method uneventful immediate implant loading can be achieved in a reasonable operative time.

Correlations between alveolar bone microstructure and bone turnover markers in pre- and post-menopausal women.

OBJECTIVE Alveolar cancellous bone biopsy samples were extracted during dental implant preparation for investigating microstructural changes due to menopause and relationships between these changes and bone turnover markers. STUDY DESIGN Subjects were 18 women receiving mandibular implants: premenopausal (n = 5), early postmenopausal (≤5 years; n = 3), and late postmenopausal (>5 years; n = 10). Bone turnover markers were measured and the samples analyzed using microscopic computerized tomography and 3-dimensional bone morphometry. RESULTS The alveolar bone volume was significantly less in late postmenopausal women than in premenopausal ones. The trabeculae in early postmenopausal women were more separated and rod-like than in premenopausal ones (P < .05). Each alveolar bone parameter was significantly (P < .05) related to at least 1 bone turnover marker. CONCLUSIONS Alveolar cancellous bone structure begins changing even in early postmenopausal women, and this structure varies in close relationship to bone turnover markers.

Quantitative evaluation of masseter muscle stiffness in patients with temporomandibular disorders using shear wave elastography

PURPOSE The aim of this study was to quantify masseter muscle stiffness in patients with masticatory myofascial pain. METHODS Stiffness was measured using shear wave elastography, which expresses stiffness as shear wave velocity (Vs). A phantom study was conducted to confirm the reliability of the measuring device. The study participants were 26 females with bilateral masseter muscle pain who were classified into either Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) group Ia (myofascial pain; n=13) or RDC/TMD group Ib (myofascial pain with limited opening; n=13). Healthy controls consisted of 24 female volunteers with normal teeth and jaws, who were not classified into groups I/II/III by RDC/TMD. RESULTS Muscle stiffness was 1.96m/s (12.5kPa) in 13 patients in group Ia, 2.00m/s (13.0kPa) in 13 patients in group Ib and 1.27m/s (5.25kPa) in 24 control subjects. Vs was significantly greater in groups Ia and Ib than in the control group (p<0.05). Characteristic pain intensity (CPI) became clear as an independent factor impacting Vs (partial regression coefficient=0.714; multiple regression analysis , p<0.05). Masseter muscle stiffness was positively correlated with CPI (p< 0.05) and negatively correlated with maximum assisted mouth opening (p<0.05) and painless mouth opening (p<0.05). CONCLUSION Shear wave elastography is useful to quantify masticatory muscle stiffness. Masseter muscle stiffness of females measured using shear wave elastography was about two-fold greater in group Ia and Ib than in the healthy control group.

Pneumococcal DNA-binding proteins released through autolysis induce the production of proinflammatory cytokines via toll-like receptor 4

Streptococcus pneumoniae is a leading cause of bacterial pneumonia. Our previous study suggested that S. pneumoniae autolysis-dependently releases intracellular pneumolysin, which subsequently leads to lung injury. In this study, we hypothesized that pneumococcal autolysis induces the leakage of additional intracellular molecules that could increase the pathogenicity of S. pneumoniae. Liquid chromatography tandem-mass spectrometry analysis identified that chaperone protein DnaK, elongation factor Tu (EF-Tu), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were released with pneumococcal DNA by autolysis. We demonstrated that recombinant (r) DnaK, rEF-Tu, and rGAPDH induced significantly higher levels of interleukin-6 and tumor necrosis factor production in peritoneal macrophages and THP-1-derived macrophage-like cells via toll-like receptor 4. Furthermore, the DNA-binding activity of these proteins was confirmed by surface plasmon resonance assay. We demonstrated that pneumococcal DnaK, EF-Tu, and GAPDH induced the production of proinflammatory cytokines in macrophages, and might cause host tissue damage and affect the development of pneumococcal diseases.

III–1 Vertical Distraction Osteogenesis of a Reconstructed Mandible with a Free Non-Vascularized Iliac Bone Garft Combined with LIPUS Treatment: A Case Report

Introduction: We report a patient who underwent vertical distraction osteogenesis of a reconstructed mandible. Treatment involved a free non-vascularized iliac bone graft combined with LIPUS treatment, followed by dental implant treatment. Case: The patient was a 37-year-old female who underwent mandibular resection for treatment of a benign ameloblastoma. The postoperative course was uneventful, and dental implant treatment was planned in the reconstructed mandible. However, bone height in the reconstructed mandible was insufficient for ideal prosthetic rehabilitation. Therefore, we performed vertical distraction osteogenesis of the reconstructed mandible, resulting in a total distraction length of 14 mm. LIPUS was performed to accelerate bone healing in the distracted area for 3 months during the consolidation period. After that, there was a bone defect between the native bone and the mesial side of the transport segment. The patient underwent grafting of bone harvested from the distal ridge of the transport segment and the mandibular ramus, to obtain sufficient volume of the alveolar ridge. Bone was held in position with titanium mesh. CT images demonstrated that density of the iliac bone in the reconstructed mandible was sufficient for implant treatment. Eventually, the patient received dental implant prosthetic rehabilitation in the reconstructed mandible. Discussion and Conclusion: Bone density of an iliac bone graft is often less than that of native bone. In this case, we performed vertical distraction osteogenesis combined with LIPUS to generate sufficient bone height and density. The patient successfully received adequate esthetics and function of the implant-supported prosthesis.

Vertical distraction osteogenesis of a reconstructed mandible with a free vascularized fibula flap: a report of two cases

BackgroundThe free vascularized fibula flap presents many advantages such as sufficient length of the bony segment, good vascularization, better quality of the bone, and a long vascular pedicle, but it is also associated with some disadvantages with regard to prosthetic rehabilitation because of its limited height. Improvement in bone height is necessary for ideal dental implant treatment of reconstructed mandibles.Case presentationFor two squamous cell carcinoma patients, mandibular bone reconstruction was performed secondarily with the peroneal flap after tumor resection. Since the bone height was insufficient at the time of implant treatment, occlusion reconstruction by dental implant was performed after vertical distraction osteogenesis.ConclusionsVertical distraction osteogenesis is a suitable treatment option for alveolar ridge deficiency resulting from fibula transplantation for mandibular reconstruction following tumor surgery.

Risk factors associated with post-loading implant loss of removable and fixed implant-supported prostheses in edentulous jaws

PURPOSE This study analyzed risk factors for post-loading implant loss in cases of implant-supported prostheses applied to edentulous jaws of Japanese patients. METHODS In total, 245 dental implant fixtures placed in 54 edentulous jaws of 46 patients performed at Niigata University Hospital were retrospectively analyzed. Kaplan-Meier curves were used to estimate the cumulative survival rate (SR) of implants, and multiple Cox regression analysis was used to identify predictive factors of implant loss. The following risk factors for implant failure were examined: age, sex, survival time, implant length, implant location, smoking habit, bone density, bone augmentation, opposing dentition, loading period, and type of final restoration. The Cochran-Mantel-Haenszel test was used to examine difference in survival curves of the extracted predictors. RESULTS Sixteen implants failed during the observation period (SR=92.8 %). Multiple Cox regression analysis revealed that male sex [hazard ratio (HR)=16.1; p=0.007] and use of maxillary removable restorations (HR=12.7; p<0.000) were risk factors for implant failure. Other factors had no significant effect on implant failure. The SR of implants for males (SR=86.9%) was significantly lower than that for females (SR=99.1%). The SR of implants for maxillary removable restorations (SR=76.4%) was significantly lower than for maxillary fixed restorations (SR=99.1%) and mandibular fixed restorations (SR=97.8%). CONCLUSIONS Maxillary implants with removable restorations and male sex were risk factors for implant failure among Japanese edentulous patients.

Antimicrobial activity of ethylene-vinyl acetate containing bioactive filler against oral bacteria

We developed an ethylene vinyl acetate (EVA) containing surface pre-reacted glass-ionomer (S-PRG) filler, as a new mouthguard material for preventing intraoral bacterial infection. We examined its physical properties, antimicrobial activity against a major cariogenic bacterium Streptococcus mutans and a periodontopathogen Porphyromonas gingivalis, and its cytotoxicity toward human gingival epithelial cells. S-PRG filler was added to EVA copolymer at 5, 10, 20, or 40 wt% and was processed into disc-shaped test specimens. Only minor differences between the Shore hardness and rebound resilience properties of EVA materials with and without the S-PRG filler were observed. The specimens with S-PRG filler showed bacteriostatic activity toward S. mutans and P. gingivalis and inhibited S. mutans biofilm formation. No cytotoxicity against the gingival epithelial cells was observed. Our findings show that EVA containing S-PRG filler has antimicrobial activity toward pathogenic oral bacteria and may be an effective material for maintaining the oral health of athletes.

Changes in Abutment Teeth Mobility after Insertion of Partial Dentures within Short Period.

The purpose of this study was to clarify the change of abutment teeth mobility by insertion of partial dentures for a short period.Twenty patients who received partial dentures at the Dental Clinic of Niigata University School of Dentistry, between August and November 1994, were selected.To evaluate changes in tooth mobility, the Periotest (PT) value of 49 abutment teeth within 3 months after initial insertion were measured and the following factors were analyzed.1. change in PT value of all abutment teeth2. change in PT value of upper abutment teeth3. change in PT value of lower abutment teeth4. the relationship between the type of edentulous space, the type of clasp and the amount of PT value changeThe results were as follows:1. PT value of all abutment teeth decreased after insertion of the dentures.2. PT value of upper abutment teeth showed no significant change within 3 months after initial insertion of the dentures.3. PT value of lower abutment teeth decreased from 2 weeks after insertion, and these decreases were clearly detected in free-end dentures.4. PT value of lower abutment teeth of free-end dentures decreased irrespective of the type of the clasp.