As Japan becomes a super aging society, the number of denture users is increasing and dentures are becoming increasingly important from the perspective of quality of life. Ceramic denture teeth are widely used because of their excellent aesthetics and hardness. However, depending on the components used and the firing method for each product, bubbles or cracks may occur within the ceramic material. This can be a cause of fracture after dentures are fitted in the mouth, and so quality management is important. Current methods for evaluating the interior of ceramic denture teeth are sampling and destruction tests, but the amount of information obtained is limited. In this study we attempted to evaluate the internal structure of ready-made ceramic denture teeth using optical coherence tomography (OCT), the characteristics of which include non-destructiveness, high resolution, and simultaneity. Thirteen different ready-made ceramic denture teeth, manufactured by four companies, were analyzed non-destructively using a dental OCT system (IVS-2000, Santec) developed with cooperation between industry and government at the National Center of Geriatrics and Gerontology. The inner structure and defects such as cracking and air bubbles were evaluated based on the obtained OCT images. The composition of the silicate ceramic used differs among these denture products, but the boundary placement between the high translucency enamel portion and the low translucency dentin (core) portion was found to be correct in this OCT analysis, similar to natural teeth. Voids due to fine bubbles in the ceramic denture teeth were also identified on the OCT images. Evaluation of the interiors of ceramic denture teeth currently requires sample destruction, but with the use of the dental OCT system such evaluation can be done non-destructively. The system can also be used for some parts of JIS evaluations, including thermal shock tests and counting air bubbles. The results of this study confirm that this dental OCT system can be used to objectively evaluate and detect defects and weaknesses in the internal structure of ceramic denture teeth in real time.

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　Objectives：Removing tongue coat is important to prevent aspiration pneumonia. The aim of this study was to clarify the effect of cleaning the tongue surface with a tongue brush and oral care gel on removing the tongue coat. 　Methods：From elderly patients in a rehabilitation Hospital who need help from the nursing staff for their oral health. 21 patients (mean age 88±9 year-old) were selected. The patients were divided into 2 groups randomly. Patients in the control group were given tongue cleaning with a tongue brush. The others in the gel group were given the antibacterial material “Hinokitiol” containing-oral the care gel “Refrecare H” (EN Otsuka Pharmaceutical Co.) on the tongue surface for 30 seconds followed by tongue cleaning with a tongue brush. The intervention period was 2 weeks and the number of total anaerobic bacteria, the number of Candida species, moisture degree and Shimizuʼs tongue coating index (TCI) on tongue surface were measured before and after the intervention. The Dunnett test was applied to compare TCI, moisture degree, the number of total anaerobic bacteria and the number of Candida species. The significant level was set at 0.05. This protocol was approved by the Ethics Committee of Tokyo Dental College. 　Results：Before the intervention, there was no significant difference in all 4 factors between 2 groups. For the control group, there was no significant difference in all 4 factors between before and after the intervention. For the gel group, there was no significant difference in the number of total anaerobic bacteria, but, there were significant differences in the number of Candida species, moisture degree and TCI. 　Conclusion：Cleaning the tongue surface with the Hinokitiol contained-oral care gel “Refrecare H” for 2 weeks decreases tongue coat.

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The purpose of this study was to develop a new dental chair that allows adjustments of the backrestaccording to the abnormal curvature of the spine. Firstly, we performed morphometry of 50 outpatients aged≧65 years and 30 as controls aged 20〜29 years. For measurement, a back morphometric system we developed for the measurement of clothed patientsʼ spinal curvature in the sitting position was used. Sagittal spinal curve figures including the head, and goniometry of the spine and neck was performed.Lines were drawn from the apex of the most protruded point of the spine to the deepest point of the neck and the waist, and the angle between the two lines was obtained as angle θ. In addition, tangents were drawn to the head and shoulder using the deepestpointof the neck, and the angle between the two lines was defined as angle α. Next, the positions of the head and neck were measured as horizontal distances. Both Angle θ and Angle α were smaller in the elderly than in the young controls, and significantly differed between the two groups (t-test, p＜0.01). The mean value of the head position showed a markedly anterior neck position in the elderly. These results suggested that the backrest should be divided into two or more to fit their curvature. Based on the obtained data, we developed a backrestand a headrest. The backrest consisted of a main-backrestand a subbackrest, and the latter was placed inside the former. The subbackrest can go up and down and recline independently of the main-backrest, and is aligned with the main-backrest in the initial position. This backrest can be adjusted to the curvature of the spine in patients with abnormal curvature of the spine by being raised, lowered, or reclined. Finally, we developed a headrestthatmoves together with the backrest.

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[in Japanese]

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The palatal augmentation prosthesis (PAP) is designed to facilitate improvement in both speech and swallowing function in patients with tongue resection or tongue movement disorders. A number of studies focusing on its effectiveness in patients with impaired tongue function have been reported. However, there has been no report that demonstrated the effectiveness of the PAP in patients with hard tissue defects from segmental mandibulectomy. We applied a PAP to a 56-year-old male patient with impaired tongue movement and insufficient lip closure who had undergone segmental mandibulectomy due to osteoradionecrosis. The PAP with a special form to augment the mandible defect and assist the lip closure produced positive outcomes in swallowing and speech function. The speech function was evaluated with syllable intelligibility and conversational intelligibility tests. The intelligibility of syllables and conversation increased with a PAP. The tongue-palate contact patterns were also examined using a static palatogram.By using a PAP, abnormal contact patterns decreased and approximately normal tongue-palate contact patterns were obtained. Also, tongue thrust swallow changed to the normal swallowing pattern by using a PAP. The swallowing function was evaluated with a videofluoroscopic swallow study and tongue pressure measurement. With a PAP, the incidence of aspiration was eliminated, and obvious decreases in oral residue, number of swallows, oral transit time and pharyngeal transit time were confirmed. Also, the tongue pressure was increased with a PAP. The results suggested that the PAP improved the tongue tip anchor function and lateral tongue pressure by giving a form to augment the mandible defect and assist the lip closure. The effectiveness of the PAP in improving both speech and swallowing function in patients with hard tissue defects was demonstrated.

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[in Japanese]

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[in Japanese]

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