It is well known that bone tissues are affected by mechanical stimuli, and that osteocytes could be the key to understanding the mechanisms of bone metabolism under mechanical stress. Low-power laser irradiation stimulates wound healing in tissues, and we hypothesized that low-power laser irradiation, which is like mechanical stimulation, can stimulate bone metabolism. The purpose of this study was to test whether lowpower laser irradiation influences bone tissue. We used a carbon dioxide (CO2) laser, which is frequently used in dental clinical situations, to examine the effects of low-power laser irradiation on osteocyte functions using primary osteocyte-like cells. Osteocyte-like cells were isolated from rat calvariae with enzyme digestion, and the cells received CO2 laser irradiation at doses of 0, 0.5, 1, and 2 W for 10 sec. Osteocyte-like cells isolated from calvariae exhibited dendritic processes and expressed sclerostin and dentin matrix protein 1 (Dmp-1), which are characteristic of osteocytes. CO2 laser irradiation dose-dependently decreased sclerostin mRNA expression and increased Dmp-1 mRNA expression. Furthermore, these effects were caused directly by laser irradiation without thermal damage. These results suggest that low-power CO2 laser irradiation influences bone metabolism via osteocytes, and we demonstrated the possibility of low-power CO2 laser irradiation for bone regeneration therapy.

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The purpose of this clinical study was to evaluate the effectiveness of β-tricalcium phosphate (β-TCP) as a bone graft substitute in maxillary sinus floor elevation. Sixty one of the one hundred five patients were treated with β-TCP for maxillary sinus floor elevation from May 2007 to February 2013. Various factors were evaluated over five months following the treatment to determine the effectiveness of β-TCP for both lateral and crestal approach. No complication was observed for the crestal approach. Perforation of maxillary sinus membrane was observed for 4% of lateral approach treatment. However, recovery was alleviated by the use of resorbable membrane and collagen membrane. Maxillary sinusitis and the leakage of β-TCP were not observed. The results demonstrated the effectiveness of β-TCP in bone grafting not only through osteoconductivity, but also biocompatibility, bioresorbability, and the ease of use with respect to long term implant prognosis.

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Fluoridated hydroxyapatite (Ca10(PO4)6(OH)2-2xF2x; FHAp) is expected to be much more effective than hydroxyapatite (HAp) in medical and dental applications due to its good acid-resistance. In this paper, we report the results of fabrication of FHAp films and in vitro evaluation of its biocompatibility. FHAp films were deposited on Ti substrates by PLD using an ArF excimer laser. XRD results showed that the length of the a-axis of FHAp film decreased compared to the standard length of HAp. In the FT-IR analysis, it was confirmed that part of OH－ was replaced by F－. From the FT-IR analysis, the FHAp film yielded a fluorine signal. In the in-vitro cell test, it was proven that FHAp film showed excellent cell proliferation of the degree equal to HAp film. These results indicate that we succeeded in the fabrication of FHAp film that is very useful as the implant coating material in the next generation.

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In order to measure the piezoelectric properties of the hydroxyapatite(HAp) films, we have fabricated Cu/ HAp/Ti or Cu/HAp/Pt structure. At first, a 1.5μm thick HAp was deposited on a Ti or Pt substrate using the KrF pulsed laser deposition(PLD) method. After the HAp deposition, the HAp film was crystallized by postannealing in nitrogen gas atmosphere and cooled slowly in an electric furnace. Then, a Cu top electrode sheet was attached on the HAp film. Finally, one end of the Cu/HAp/Ti or Cu/HAp/Pt structure was clamped to compose a vibrating cantilever beam. Piezoelectric coefficients were estimated by output voltage responses of HAp films measured by a operational amplifier circuit when the Cu/HAp/Ti or Cu/HAp/Pt beam was excited by a mini-shaker at the first natural frequency of the beam. The results showed the piezoelectricity of the artificially synthesized HAp films.

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Recently, tissue or organ regeneration has been studied from pluripotent stem cells. For this purpose, development of scaffolds that can be long-term cell differentiation culture technique is necessary. Generally, porcine collagen has been studied as a scaffold of these cells. However, there are safety concerns that porcine endogenous retrovirus is included porcine origin. Accordingly, marine collagen is desired from the viewpoint of safety scaffold. We examined type I collagen, extracted from the scales of tilapia inhabiting tropical and subtropical areas, can be used as a scaffold for ES-D3 cells. As a result, it had no effect on ES-D3 cell differentiation as compared with porcine collagen. And, the collagen sponge extracted from the scales of tilapia may be as effective as the collagen gel when used as a scaffold for tissue regeneration.

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The thin HA layer by a sputtering technique had been expected that has excellent adhesion to the titanium substrate. However there was no evidence in previous studies about the adhesion to the substrate. In this study, we investigated the change in the film thickness and the presence or absence of detachment of the HA film by the friction with the resin when were implanted with a high torque into a resin model on the basis of a practical method. The μ-one HA implant S type was used as the experimental material. It was measured the thickness changes and examined detachment of HA film by friction after which performs drilling into MMA resin block to form holes in different diameters and screwing the implant by using a torque meter. Was used the fluorescent X-ray analysis (EDX), HA film thickness measurements were quantitatively analyzed by a fundamental parameter method. Thickness of HA film was 1.8±0.15μm before implantation in the resin block, and was 1.7±0.17μm, 1.9±0.22μm and 1.9±0.15μm after implantation in torque of 48Ncm, 135Ncm and 140Ncm, respectively. The sputtered HA film showed no change in thickness before and after implantation into resin block. And, no detachment of the HA film was observed in microscopic observation. As a result, the sputtered HA film was not caused any detachment and degradation after implantation into the resin block at a high torque of 140Ncm. Therefore, it was considered that the risk of detachment of HA film is mostly avoidable in clinical.

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The aim of the present study was to evaluate radiographically the peri-implant？ bone resorption around a thin hydroxyapatite coated one-piece implant during 8 years. A clinical test was performed between October 2004 and June 2006 at the Department of Oral Implantology, Dental Hospital, Tokyo Medical and Dental University. Then, nine patients with fifteen implants among them were recalled between November 2012 and May 2013. The bone resorption around the all implants were examined clinically and radiographically with periapical radiographs. Periapical radiographs were calibrated and measured by an image analysis software. The declination of medial and distal bone around each implant was measured by a scale. The all implants showed no sign of complication during eight years after implantation. The mean crestal bone declination was 0.66±0.36mm. The declination value was smaller than that of titanium surface two piece implant reported previously.

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Introduction: Inadequate alveolar bone volume is a common limitation for implantation in the anterior maxilla since bone resorption occurs soon after tooth extraction. Such problems have been overcome by bone grafting or GBR, however, these are invasive procedures and require a long treatment period. Purpose: The aim of this study is to evaluate the efficacy of HA-coated one piece implants on the graftless procedure of immediate and early implant placement in the anterior maxilla. Materials and methods: Thirty patients, 22 males and 8 females, 27 to 67 years of age, were included in this study. Thirty-four hydroxyapatite-coated one-piece implants (AQB implant®, ADVANCE, Co. Japan) were placed immediately or early within 8 weeks of tooth extraction. All implants were placed and positioned slightly towards the palatal aspect, leaving bone defects facially because the implants did not contact the facial aspects. In cases where bone chips were collected from the implant bed during drilling, they were placed on the facial aspect of the implant. No donor site was prepared. No membrane and filling materials were used. The following items were investigated. 1) Sex and age distribution, 2) Location of implants inserted, 3) Diameter and length of implants used, 4) Period from tooth extraction to implant placement, 5) Duration of the healing period from implant placement up to addition of occlusal force. The survey was carried from January 2005 through February 2013. Results: All 34 implants were functionally loaded and showed no sign of morbidity and periimplant disease. Conclusion: This retrospective study indicates that HA-coated one-piece implants are effective on the graftless procedure of immediate and early implant placement in the anterior maxilla. HA-coated one-piece implants may have the possibility of not only reducing donor site discomfort and morbidity, but also of shortening the treatment period.

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The purpose of this study is to evaluate the biological safety of a thin hydroxyapatite (HA) sputta-coated implant by four tests, including cytotoxicity, sensitization, acute toxicity and genotoxicity. The implants used for this study are one piece type implant of HA with 1.5μm thickness coated on titanium with square thread by a sputtering coating technique. These four tests were performed in accordance with the International Organization for Standarization (ISO). All results in the cytotoxicity, sensitization, a cutetoxicity, and genotoxi city were negative to the implants and the biological safety of the thin HA sputta-coated implant was certificated.

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The purpose of this study was to investigate clinically the bone tissue reaction and exfoliation of HA around a HA coated implant removed by excessive torque. The flame spraying HA-coated implants were inserted into D2 human bone by 60 Ncm torque and after one month of the insertion a significant bone resorption around the implant and an exfoliation of the HA particles from the HA coated surface were revealed by histological SEM and EDX(Energy dispersive X-ray fluorescence spectrometer) observations. It was suggested that an excessive insertion torque 60Ncm causes a significant bone resorption and an exfoliation of HA particle from the HA coated surface and results failure clinically.

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