Bone formation steadily declines with age resulting in significant loss of bone mass, and reactive oxygen species (ROS) are thought to be a major contributor to the aging process. H₂O₂ treatment significantly reduced bone nodule formation rate in pre-osteoblastic cell, MC3T3E1. In this study, to identify which genes have an altered transcription level associated with bone loss by ageing, MC3T3-E1 cells were treated with H₂O₂, and monitored gene expression change using the Affymetrix GeneChip^TM system (Mouse; 34,000 genes). H₂O₂ altered many gene expressions including reduction of osteomodulin (OMD) mRNA level. The reduction of OMD gene expression by H₂O₂ was successfully confirmed by reversed transcription polymerase chain reaction (RT-PCR) and real-time PCR. Since OMD was found in bone tissues and play an important role in biomineralization, the reduction of OMD gene expression by H₂O₂ may be involved in the decline of bone formation in the ageing process.

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Wingless-type protein (Wnt) is a family of 19 secreted glycoproteins that function as signaling transducers for cell-cell interaction, cell growth and differentiation. Wnt-1, a highly transforming member, has been implicated in tumorigenesis. The aim of this study was to elucidate the role of this cell signaling molecule in the development and progression of primary ameloblastoma and their recurrent tumors. Wnt-1 expression patterns were examined immunohistochemically in 22 primary and 14 recurrent ameloblastomas. These collectively consisted of the following subtypes: conventional (CA) (n=22), desmoplastic (DA) (n=2) and unicystic (UA) (n=12) ameloblastoma. Results demonstrated that CA (n=20/22; 90.9%), DA (n=2/2; 100%) and UA (11/12; 91.7%) showed high Wnt-1 expression percentages. Strong staining intensity for Wnt-1 was observed more frequently in primary CA (n =10/13; 76.9%) than in their recurrent counterparts (n=2/9; 22.2%) (p<0.05). Conversely, in UA, recurrent tumors (n=3/5; 60.0%) tend to stain strongly for Wnt-1 more frequently than their primary lesions (n=3/7; 42.9%) (p>0.05). Keratinizing cells in areas of squamous metaplasia also expressed Wnt-1 more intensely compared to their surrounding polyhedral stellate reticulum-like cells. Tumor islands containing granular cells were also Wnt-1 positive. Present findings confirmed that the Wnt signaling pathway is activated in ameloblastoma. Strong Wnt-1 expression in primary conventional and recurrent unicystic ameloblastoma suggests that Wnt-1 plays a more critical role in these subtypes. Positive expression of Wnt-1 in keratinizing ameloblastomatous tumor epithelium and granular cells complies with the anti-apoptotic properties of Wnt-1. Negative reactivity for Wnt-1 in 3 cases of ameloblastoma suggests that the development and progression of ameloblastoma may occur independent of this cell signaling molecule.

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The in-vitro response of the biphasic calcium phosphate (BCP) ceramics hydroxyapatite (HAP) and β-tricalcium phosphate (TCP) prepared by tape-casting was investigated. BCP ceramic slurries were prepared to HAP/β-TCP weight ratios of 75/25 (H75-T25), 50/50 (H50-T50), and 25/75 (H25-T75). Additionally, 100% HAP (H100) and 100% β-TCP (T100) were prepared as control. BCP ceramic sheets fabricated by tape-casting were sintered at 1200°C for 4 h. After sintering at 1200°C, thin-film X-ray diffraction confirmed that β-TCP in the BCP ceramics was partially transformed to α-TCP; HAP showed no change. Field-emission scanning electron microscope observation showed that the surfaces of H25-T75 and T100 were completely covered with precipitate after 90 d' immersion in phosphate-buffered saline solution with pH 7.4 at 37°C. After osteoblast-like (MC3T3-E1) cell cultivation for 7 d, H25-T75 showed a significantly higher cell number than H100, H75-T25, and H50-T50 (Fisher's PLSD test, p<0.05). These results indicate that the determination of an optimal balance of biological stability and biodegradation rate is important to fabricating BCP ceramics because it directly affects the in-vitro response. Within the limitation of this study, it is concluded that BCP ceramics with a HAP/TCP ratio of 25/75 prepared by a tape-casting technique has high cellular activity.

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The reaggregation system is a special technique developed to clarify the essential characteristics of the mesenchyme. In this study, the reaggregation system was performed using mouse lower first molar at E13.5 and the reaggregated tooth germs were transplanted into the kidney capsule for 6 weeks to investigate tooth root formation. The reaggregated tooth was surrounded by bone. The reaggregated tooth germ produced a single thick root like a taurodontium (cuneiform tooth), although mouse lower first molar has two roots in vivo. Histologically, the reaggregated mesenchyme could form not only tooth elements including enamel, dentin, dental pulp and cementum, but also periodontal tissue including periodontal ligament-like structure and alveolar bone-like structure. The periodontal ligament-like structure has a regular width between the cementum and alveolar bone-like structure. Moreover, Sharpy's fiber-like structure was inserted into the cementum and alveolar bone-like structure. In conclusion, the reaggregated mesenchyme has the ability to form both tooth and periodontal tissue without information from the epithelium. In addition, this reaggregation system may be a useful method for regenerative dentistry, since tooth and periodontal tissue can be produced en bloc.

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The aim of this study was to reveal the efficacy of autogenous bone mixed with β-TCP. The mixtured graft materials at the maxillary sinus floor were observed. Sinus floor augmentation with autogenous bone and β-TCP was performed at six sites in three patients. The grafted site was observed with computed tomography (CT) at one, six and twelve months. The height and Hounsfield units (HU) of graft tissues were calculated using SIMplant. Dental implant surgery was then performed. The increasing height of graft tissue at one month was approximately 13 mm and showed 20 % reduction at twelve months. Approximately 10 mm bone height was gained before implant surgery. The mean HU at six months showed the bone level HU. The HU at one month was reduced at six months and slightly increased mainly at the center of graft tissue at twelve months. At implant surgery, initial stability was adequate. The mixture of autogenous bone and β-TCP played a sufficient role for sinus floor augmentation, and it could be possible to reduce bone harvesting by using β-TCP.

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To evaluate the efficacy of tooth extraction wound protection made of atelocollagen sponge (TRE-641), we observed healing in tooth extraction sites filled with TRE-641 and those filled with a control material, oxide cellulose. Subjects were 11 beagle dogs, with a total of 22 extraction sites. Both maxillary lateral incisors were carefully removed, and extraction wounds were filled with TRE-641 on one side and with oxidized cellulose sponge as control on the other side. Wound healing was observed, and the animals were sacrificed at 7, 14, and 28 days after surgery. We compared extent of bone formation, hematoma, inflammation, and graft material remaining between the two groups. At 7 days, newly formed bone extending from the floor and wall of the socket bone were seen in the TRE-641. Hematoma and inflammation were observed in the oxide cellulose. At 14 days, a small amount of TRE-641 remained. In the oxide cellulose group, a small amount of hematoma remained. At 28 days, the extraction socket was filled with newly formed bone in both groups. TRE-641 produced acceptable early phase bone healing at the tooth extraction site with no remnant graft material with sufficient bone formation of the tooth extraction wound.

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This study was intended to determine the tissue distribution of lidocaine in mandibular mucosa and alveolar bone marrow after local infiltration. Tissue distribution of local anesthetics shortly after regional injection has been unclear. We used macro autoradiography to visually examine the tissue distribution of lidocaine shortly after local anesthetic infiltration. Male Japan White rabbits received an injection of ¹⁴C-labeled 2% lidocaine with or without 1:80,000 epinephrine. The areas of infiltration and proportion of distribution 1, 5 and 10 minutes after administration were measured. After the administration of 2% lidocaine with 1:80,000 epinephrine, infiltration area increased over time. Ratios of distribution in alveolar bone marrow at the level equivalent to the root apex increased in 1 to 5 minutes after administration, and then decreased. In contrast, after the administration of plain lidocaine, infiltration was hardly detected. These results suggest that infiltration of lidocaine with epinephrine diffused to a wider area over time after administration and then gradually absorbed into the capillaries.

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Cone beam computed tomography (CBCT) with a flat panel detector can provide more precise and fine images compared to that with an image intensifier which have been used previously. Measurement of the length clearly varies among different measurement regions on the images of CBCT with an image intensifier. However, little is known whether measurement of the length on the images of CBCT with a flat panel detector varies as well or uniform. The objective of this study was, therefore, to analyze the homogeneity of the measurement of the length on the images of the CBCT with a flat panel detector. The results demonstrated that both short- and long-term reproducibility of measurement of the length on the CBCT images of the x-ray mesh gauge was less than 1.5%. The non-uniformity of measurement of the length on the CBCT images was less than 2% between any of two regions. The non-uniformity of measurement of the length on the CBCT images with φ60mm×h60mm exposed area was almost constant at any regions independent of the tube current. That on the CBCT images with φ40mm×h40mm exposed area varied randomly. The non-uniformity of measurement of the length varied randomly on the CBCT images with small exposed area; however, this was considerably small and negligible. The results suggest that measurement of the length on the images of CBCT with a flat panel detector may be substantially uniform at any regions in comparison with that on the images of CBCT with an image intensifier.

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Tooth enameloid of medaka as a representative of human tooth enamel was analyzed by high-resolution transmission electron microscope (HR-TEM), electron probe microanalyzer (EPMA) and micro-X-ray diffraction to deepen the knowledge on the crystal formation of tooth enamel. HR-TEM observation showed that enameloid crystals, with incomplete slender hexagonal shape, sometimes became fused with each other when the density of crystals increased. EPMA analysis showed clear image maps of calcium, phosphate and iron. The element analysis indicated high concentration of calcium and phosphate. Micro-X-ray diffraction showed that enameloid crystals are composed of relatively well-crystallized hydroxyapatite. Each (211), (112), (210) and (002) reflection peaks was clearly detected. It is suggested that the medaka is useful for research of developing tooth because it is polyphyodont and has a short lifespan.

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Erratum: Effect of Varying HAP/TCP Ratios in Tape-cast Biphasic Calcium Phosphate Ceramics on Response in vitro
Yasuhiro Tanimoto, Yo Shibata, Asuka Murakami, Takashi Miyazaki and Norihiro Nishiyama
Journal of Hard Tissue Biology 18[2], 71-76 (2009) ; In the version of this published online, the title of the Article, Effect of varying HAP/TCP Ratios in Tape-cast Biphasic Calcium Phosphate Ceramics on Responcce in vitro Response was a misprint as In the version of this published online. The error has been corrected as fellows: Effect of varying HAP/TCP Ratios in Tape-cast Biphasic Calcium Phosphate Ceramics on Response in vitro.

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