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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 1200ºC for 4 h. After sintering at 1200ºC, 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 37ºC. After osteoblastlike (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.

Purpose: The lack of occlusal support is an epidemiological risk factor linked to Alzheimer's disease. This study sought to assess the relationship between amyloid β (Aβ) deposition and the lack of occlusal support in amyloid precursor protein (APP) knock-in mice. Methods: Sixteen experimental animals were divided into two groups. The upper molars were extracted in the extraction group (group E), and a sham operation was performed in the control group (group C). The Morris water maze test was performed 4 months after the tooth extraction. Aβ immunohistochemical staining and Nissl staining of the hippocampus were performed. Hippocampal plasma corticosterone and Aβ protein levels were measured. Results: In the maze task, the escape latency was significantly longer in group E than in group C. In the probe trials, the time elapsed in the target quadrant was significantly shorter in group E than in group C. The number of hippocampal neurons decreased in group E. There was no significant difference in the plasma corticosterone levels between the two groups, indicating that there was no effect of chronic stress on the behavioral results. Hippocampal Aβ40 and Aβ42 protein levels and Aβ deposition areas by immunohistochemical staining were not significantly different between the two groups. Conclusions: Aβ deposition was not increased in the hippocampus of molarless APP knock-in mice. As such, it appears that cognitive impairment due to a lack of occlusal support was not related to Aβ deposition.

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