Tooth loss in young mice is associated with cognitive decline and femur-bone mineral density.

Osteoporosis is a prevalent disease that is associated with increased hip fractures which cause significant decline in quality of life. Tooth loss affects systemic condition such as cognitive function through various mechanism, but the link between tooth loss and femoral bone mineral density is still uncertain. This study aims to investigate whether tooth loss in young mice affects memory function and femoral bone mineral density. Eight-week-old male C57BL/6 J mice were allocated randomly into the control group with sham operation and the tooth-loss group extracted all maxillary molar. Step-through passive avoidance test as cognitive function test, micro-CT analysis and western blotting analysis were performed after 1- and 2-month observation period. Step-through passive avoidance test revealed that the tooth-loss group in 2-month observation period impaired cognitive function. Additionally, micro-CT analysis revealed a significant decrease in both the length of the mandible and bone mineral density in the femur of the tooth-loss group compared to the control group. Claudin-5 level in the hippocampus, which is one of the tight junction markers in blood-brain-barrier, was significantly decreased in the tooth-loss group. The findings of our present study suggested that tooth loss impair cognitive function accompanied by reduced tight-junction marker, mandibular growth and bone mineral density of femur.

Experimental tooth loss affects spatial learning function and blood-brain barrier of mice.

OBJECTIVE: This study aims to investigate how experimental tooth loss affected learning, memory function, and brain pathophysiology in mice. MATERIALS AND METHODS: The mice (C57BL/6 J, 2-month-old, male) were divided into tooth loss and control groups. The behavioral test battery was performed at 6 and 12 months after tooth extraction. The protein levels of the tight junctions in the brains of the mice were analyzed. Hippocampal astrocyte was measured using immunohistochemical staining. RESULTS: The results of behavioral tests and biochemical analysis performed during the 6 months observation period did not show significant differences between the groups. However, the escape latency in the tooth loss group was significantly longer than that in the control group at the 12 months after tooth extraction. The level of claudin-5 decreased in the tooth loss group. Additionally, hippocampal astrogliosis was found in the tooth loss group. CONCLUSIONS: Experimental tooth loss reduced the level of claudin-5 and caused astrogliosis in the brains of mice, which was accompanied by deterioration of learning functions. This study may provide a new insight about the association between tooth loss and cognitive dysfunction.

Association between buccal mucosa ridging and oral feature/symptom and its effects on occlusal function among dentate young adults in a cross-sectional study of Japan.

Objective: The purpose of this study was to assess the distinction in oral features/symptoms and occlusal function between young dentate individuals with and without buccal mucosa ridging (BMR). Methods: This cross-sectional study included 200 young adults. The outcome variable was BMR state. The predictor variables were oral features/symptoms (torus palatinus, torus mandibularis, temporomandibular joint noise, bruxism, tongue thrusting habit, number of teeth present, and occlusal vertical dimension) and oral function (occlusal force, occlusal contact area, occlusal pressure, tongue pressure). These variables were compared among participants with and without BMR using univariate and multiple logistic regression analysis. Results: There were 119 participants with BMR and 81 without BMR. Multiple logistic regression analysis revealed that BMR was closely associated with bruxism, occlusal vertical dimension, and occlusal pressure. Discussion: Oral/occlusal changes of increased bruxism, lower occlusal vertical dimension, and lower occlusal pressure constitute the major causes of BMR.

Effect of attenuation of fibroblast growth factor receptor 2b signaling on odontoblast differentiation and dentin formation.

Attenuation of fibroblast growth factor receptor (FGFR) 2b signaling suppresses the differentiation of oral epithelial stem cells to ameloblasts, their survival and viability remaining unaffected; however, its effect on dentin formation is unknown. This study aimed to clarify the effect of attenuation of FGFR2b signaling on odontoblast differentiation and dentin formation. Initially, we used a murine rtTA transactivator/tetracycline promoter system for inducible and reversible attenuation of FGFR2b signaling in adult mice. Experimental animals overexpressed soluble FGFR2b (sFGFR2b), and wild-type controls were selected from the same litter (WT group). Histological analysis of CMV mice confirmed the obliteration of the enamel and ameloblast layer, and micro CT analysis revealed a significant increase in dentin thickness in CMV mice rather than in WT mice (P < 0.05). On analyzing the expression of dentin-related differentiation factors, DSPP, nestin, and OCN were upregulated in CMV mice compared to WT mice after 2 weeks of attenuation of FGFR2b signaling. Thereafter, on overexpressing sFGFR2b in dental pulp stem cells, RUNX2 and ALP were upregulated; however, DSPP, nestin, and OCN were downregulated in CMV mice compared to WT mice. The present results show that attenuation of FGFR2b signaling in the oral epithelium specifically induced odontoblast differentiation and promotes early-stage dentin calcification in dental pulp tissue.

Osteoclastogenesis from bone marrow cells during estrogen-induced medullary bone formation in Japanese quails.

Osteoclasts are differentiated from hematopoietic mononuclear cells by regulation of the receptor activator of nuclear factor kappa-B (RANK)/receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) system. Medullary bone (MB) that forms in the bone marrow of female birds is remodeled under the control of circulating estrogen (E2) during the laying period. Although the osteoclasts of MB are differentiated from mononuclear cells, the mechanism of osteoclastogenesis is not known. We investigated whether MB osteoclastogenesis is regulated by the RANK/RANKL/OPG system using MB from male quails induced with E2. Bone marrow cells (BMCs) differentiate into osteoclasts that have the ability of bone resorption via stimulation of RANKL/M-CSF, but this ability is suppressed by OPG and differentiation is inhibited by calcinurin inhibitors. We found that BMCs at 3 days after E2 administration had high bone osteoclastogenesis ability and colony forming unit-granulocyte/macrophage (CFU-GM)/colony forming unit-macrophage (CFU-M) formation abilities. We conclude that MB osteoclasts are differentiated from BMCs by the RANK/RANKL/OPG system, and that precursor cells of osteoclasts are increased during MB formation.

Novel fabrication of porous titanium by a resin-impregnated titanium substitution technique for bone reconstruction.

The purpose of this study was to develop a novel porous titanium material with superior mechanical strength and osteoconduction for bone reconstruction. Porous titanium samples were fabricated by titanium-slurry impregnate to prepare urethane forms with several porosities (high-porosity; 92%, middle-porosity; 85% and low-porosity; 65%). Porous HA (mean porosity; 75.3%) was used as a control. To evaluate the characteristics of these materials, we performed porosity measurements, scanning electron microscopy (SEM), three-point bending testing, and cell proliferation assays. To evaluate the osteoconduction ability, porous titanium was placed into the femurs of rabbits and histological and histomorphometric evaluations were performed after 3 weeks. In SEM images, porous three-dimensional structures were observed in all samples. The bending strength significantly increased as porosity increased (Ti-65 > Ti-85 > porous HA > Ti-92, P < 0.05; respectively). Ti-65, Ti-85, and porous HA showed good cell proliferation. Newly formed bone was observed in the central portion of Ti-65, Ti-85, and porous HA. Ti-92 was mainly detected in the bone marrow tissue. The bone formation areas of Ti-65, Ti-85, and porous HA were significantly higher than that of Ti-92 (P < 0.05). It was suggested that novel developed porous titanium composed of Ti-65 and Ti-85 showed superior mechanical strength and osteoconduction.

Preoperative evaluation of bone quality for dental implantation using an ultrasound axial transmission device in an ex vivo model.

This study investigated the clinical utility of an ultrasound axial transmission device in preoperative evaluation of bone quality for dental implantation, by clarifying the relationship between cortical bone speed of sound (cSOS), insertion torque values (ITV), and implant stability quotient (ISQ) in porcine femur bone. Eleven fresh porcine femurs, without soft tissue, were prepared. The cSOS of these bones were measured using the axial transmission device. Bone mineral density (BMD) and porosity (Po) were measured in cortical bone samples obtained from the region of ultrasound measurements by X-ray microcomputed tomography. Thirty-three implants were inserted into these samples (three implants per bone sample), and ITV and ISQ were measured for all implants. Then, cortical bone thickness (CbTh) of the area for implantation was measured for all implants using a micrometer. The mean cSOS was 3962 m/s; mean BMD and Po were 0.822 g/cm2 and 0.185%, respectively. cSOS and BMD values were positively correlated, and cSOS values and Po values were negatively correlated. Mean ITV, ISQ, and CbTh were 37.95 Ncm, 71.172, and 2.869 mm, respectively. There was a positive correlation between cSOS values and ISQ values. The cSOS of each bone did not correlate with ITV for all of the bone samples. However, when the CbTh ranges from 3.0 to 3.5 mm, ITV are correlated with cSOS. These findings suggest that cSOS, which reflects the cortical bone quality, may be clinical utility as a preoperative diagnosis of the implant.