Morio Ochi

Analysis of bacterial flora associated with peri-implantitis using obligate anaerobic culture technique and 16S rDNA gene sequence.

PURPOSE To analyze and characterize the predominant bacterial flora associated with peri-implantitis by using culture techniques under obligate anaerobic conditions and 16S rDNA gene sequences. MATERIALS AND METHODS Subgingival bacterial specimens were taken from 30 patients: control (n = 15), consisting of patients with only healthy implants; and test (n = 15), consisting of patients with peri-implantitis. In both groups, subgingival bacterial specimens were taken from the deepest sites. An anaerobic glove box system was used to cultivate bacterial strains. The bacterial strains were identified by 16S rDNA genebased polymerase chain reaction and comparison of the gene sequences. RESULTS Peri-implantitis sites had approximately 10-fold higher mean colony forming units (per milliliter) than healthy implant sites. A total of 69 different bacterial species were identified in the peri-implantitis sites and 53 in the healthy implant sites. The predominant bacterial species in the peri-implantitis sites were Eubacterium nodatum, E. brachy, E. saphenum, Filifactor alocis, Slackia exigua, Parascardovia denticolens, Prevotella intermedia, Fusobacterium nucleatum, Porphyromonas gingivalis, Centipeda periodontii, and Parvimonas micra. The predominant bacteria in healthy implant sites apart from Streptococcus were Pseudoramibacter alactolyticus, Veillonella species, Actinomyces israelii, Actinomyces species, Propionibacterium acnes, and Parvimonas micra. CONCLUSION These results suggest that the environment in the depths of the sulcus showing peri-implantitis is well suited for growth of obligate anaerobic bacteria. The present study demonstrated that the sulcus around oral implants with peri-implantitis harbors high levels of asaccharolytic anaerobic gram-positive rods (AAGPRs) such as E. nodatum, E. brachy, E. saphenum, Filifactor alocis, Slackia exigua, and gram-negative anaerobic rods, suggesting that conventional periodontopathic bacteria are not the only periodontal pathogens active in peri-implantitis, and that AAGPRs may also play an important role.

Effect of the quantity and quality of cortical bone on the failure force of a miniscrew implant

This study examined the influence of the quantity and quality of cortical bone on the failure force of miniscrew implants. Twenty-six titanium alloy miniscrew implants (AbsoAnchor) 1.4mm in diameter and 5 or 7 mm long were placed in cross-sectioned maxillae (n = 6) and mandibles (n = 20) of human cadavers. Computed tomography imaging was used to estimate the cortical bone thickness and bone mineral density [total bone mineral density (TBMD, values obtained from cortical bone plus trabecular bone); cortical bone mineral density (CBMD, values obtained from only cortical bone)]. Maximum force at failure was measured in a shear test. Nanoindentation tests were performed to measure the hardness and elastic modulus of cortical bone around the miniscrew implants. The mean failure force of miniscrew implants placed in mandibles was significantly greater than that for implants in maxillae, and the bone hardness of mandibles was significantly greater than that of maxillae. The length of miniscrew implants did not influence the mean failure force in monocortical placement in the mandible. Cortical bone thickness, TBMD, CBMD, and bone hardness were significantly related to the mean failure force. CBMD was related to the mechanical properties of cortical bone. In conclusion, the quantity and quality of cortical bone greatly influenced the failure force of miniscrew implants.

Effect of low intensity pulsed ultrasound stimulation on sinus augmentation in rabbits

Objectives The objective of the present study was to evaluate the efficacy of low intensity pulsed ultrasound stimulation (LIPUS) and to determine the optimal frequency for enhancing bone regeneration in sinus augmentation using a rabbit model. Material and methods Thirty male rabbits underwent sinus augmentation. Two rectangular nasal bone windows were outlined bilaterally. LIPUS was applied at two different frequencies (1 MHz and 3 MHz) on experimental sites daily for 2, 4 and 8 weeks. Each histological area of the experimental and control sites was divided into upper and lower parts from the parietal region to a depth of 5 mm. Each area of new bone was measured. Results At 2, 4 and 8 weeks, the experimental sites in the 1 MHz group exhibited significantly more new bone growth than the control sites in both the upper and lower parts. When the upper and lower parts of each area were measured in combination there was a statistical difference between the test and control sites in the 1 MHz group at 2, 4 and 8 weeks; however, there were no statistical differences between the test and control sites in the 3 MHz group. Conclusions The results suggest that clinical application of LIPUS for sinus augmentation may promote new bone formation, and that the effect of LIPUS for sinus augmentation at a frequency of 1 MHz was greater than at 3 MHz until 8 weeks after sinus augmentation.

Simultaneous Implantation of Dental Implants and Autogenous Human Dentin

In our previous clinical study, autogenous demineralized dentin matrices (DDM) prepared from the functional vital teeth (#38, #41) of thirty-five-year-old female were grafted on the bone defect, using newly developed mill, and then received to the host without troubles. In this study, we implanted the human tooth dentin adjusted previously and the dental implants into the regions of missing tooth simultaneously. Fifty-seven-year-old female presented with missing teeth (#35-#37, #45-#47). First, a non-functional vital tooth (#18) were extracted and cryopreserved immediately. 11 months after extraction, the tooth was crushed by newly developed auto-crash mill using ZrO2 vessel and ZrO2 blade for 1 minute. The crushed granules were demineralized completely in 2% HNO3 solution, rinsed in cold distilled water and lyophilized (granule size: 0.5-2.0mm). The bacteria-free of the DDM were confirmed by the bacteriological examination before use. Drilling of the prospective implant beds were then performed according to the manufacture’s protocol and a screw-type rough surface implants (Nobel Biocare® Mk III) were placed. The adjusted DDM granules were implanted into the bone defect (#45). There are no postoperative complications at 3 years after implantation. This case indicates that the preserved autogenous DDM can be used as collagenous biomaterials with osteoinductive potency.

Human Dentin Transplantation for Bone Engineering

The aims of this study are to confirm the capacity of hard tissue induction by human demineralized dentin matrics (DDM) and calcified dentin matrics (CDM) in subcutaneous tissues of nude mice, and to report a human pioneering trial following the autotransplantation of DDM for bone augmentation in a case of the atrophied upper jaw. Human DDM and CDM particles were prepared from adult, extracted vital teeth, and were implanted into the subcutaneous tissues of 4-week-old nude mice. DDM induced bone and cartilage independently at 4 weeks after implantation, while CDM did not induce a hard tissue formation. Autogenous DDM prepared from the non-functional second molar of a 58-year-old female were grafted on the atrophied jaw and received to the host. Human dentin can be recycled as autogenous biomaterials for local bone engineering.