The effects of childhood masticatory function loss and soft foods on the mandibular condyle have been the subject of much research. However, the corresponding bone turnover is not fully understood. The purpose of the present study was to clarify the effects of a lack of teeth and a soft food diet during the growth period on bone turnover in the mandibular condyle. We divided 3-week-old Wistar rats into the following three groups: 1) Extraction group: The maxillary molars were extracted at the age of 4 weeks, and animals were fed powdered standard feed. 2) Powder group: Animals were fed powdered standard feed without tooth extraction. 3) Control group: Animals were fed solid standard feed without tooth extraction. Non-decalcified thin-slice specimens of sagittal sections of the mandibular condyle were obtained at the age of 20 weeks for histological analysis. We used micro-CT analysis and bone histomorphometry to measure bone volume (BV), bone mineral content (BMC), bone mineral density (BMD), bone microstructure, bone resorption, and osteogenesis in the mandibular condyle, and we compared the results among groups. In the extraction and the powder groups, we found deformation and disruption of the arrangement of chondrocytes, coagulation of chondrocytes, and duplication of the tidemark in the cartilage. We also found an increase in multinuclear osteoclasts in the cancellous bone. We found a reduction in BV, BMC, and BMD in the extraction and powder groups compared to the control group, as well as a reduction of bone volume, a lowering of osteogenesis parameters, and an increase in bone resorption parameters in the secondary cancellous bone. These results suggest that a lack of teeth and a soft food diet during the growth period cause a decline in bone microstructure, a decrease in osteogenesis, and an increase in bone resorption.
Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutation of the gene encoding tissue non-specific alkaline phosphatase (TNSALP). Odonto-HPP is well known as the mildest of HPP. The manifestations involve only the teeth, such as premature primary teeth exfoliation caused by reduction of alveolar bone, enlarged dental pulp chamber, and dental defects. We report a case of a 9-years-old boy who developed HPP. He was observed from the primary dentition to the mixed dentition period. At initial presentation at our hospital, he had multiple premature exfoliation of primary teeth and reduction of the alveolar bone. HPP was suspected due to the low level of ALP activity in serum, his oral manifestation, and dental history. He was referred to a physician for the final diagnosis. Therefore his compound heterozygote mutations, c.1559 delT (T/delT) and c.407G > A (G/A), were found in TNSALP and he diagnosed with odonto-HPP. Even though these mutations were reported as being involved in odonto-HPP, his mineral densities tended to be lower than that of his age. It is therefore necessary to investigate the bone mineralization level in odonto-HPP without other bone symptoms. Moreover, ongoing enzyme-replacement therapy in odonto-HPP might improve dental abnormality and bone disorders.
Hypophosphatasia(HPP)is caused by mutations in the gene encoding tissue-nonspecific alkaline phosphatase(ALPL). HPP patients develop deficient calcification of bones and teeth including defects in cementum, dentin, and enamel and the characteristic premature loss of primary teeth. Here, we investigated the enamel defects of knockout(Alpl-/-)mice compared with that of control wild type(Alpl+/+)mice.
There is plenty of literature on masticatory function and its impact on maxillofacial development. However, the influence of masticatory hypofunction on bone turnover in the alveolar bone has hardly been studied. This study aimed to clarify the influence of tooth loss and soft diet on the alveolar bone turnover during the growth period. Three-week-old Wistar rats were randomly divided into the following three groups: Hard diet group (rats raised on solid standard diet), Powder diet group (rats raised on powdered standard feed diet), and Extraction group (rats raised on powdered standard diet with maxillary molars extraction). BV, BMC, and BMD in the cancellous bone of M1 were measured using micro-CT analysis. To analyze the histological bone turnover, we prepared non-decalcified thin sections of alveolar cancellous bone when rats were 20 weeks old. On three-dimensional constructed images, the experimental groups (the Powder diet and Extraction groups) showed expansion of the medullary cavity of the interradicular septum of the first molar compared to controls (the Hard diet group). BV, BMC, and BMD were significantly lower in the experimental groups, with the difference from controls being greater in the Extraction group. On histomorphometric analysis, the bone mass parameters, bone formation parameters, and bone mineralization parameters were significantly lower in the experimental groups compared to controls. The bone resorption parameters were significantly higher in the experimental groups. From this study, we found that soft diet and tooth loss might worsen the bone microstructure, reduce osteogenesis, and promote bone resorption in alveolar bone.
Nanotechnology is a branch of science focusing on the manipulation of materials measured on the nanoscale (size = 1–100 nm). Recent advances in the field of nanodentistry have resulted in the development of alternative treatment plans for common dental problems, bringing about a paradigm shift in dentistry. Nanorobots, also known as “nanites” or “nanomachines,” are theoretical microscopic devices that may be used for the diagnosis and treatment of oral health problems. This paper aims to discuss the latest innovations in the field of nanodentistry.
Background: Alkaline phosphatase has 4 isozymes, tissue non-specific alkaline phosphatase (TNAP), placental alkaline phosphatase (PLAP), intestinal alkaline phosphatase and germ-cell alkaline phosphatase. Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutations of the gene encoding TNAP. Although TNAP is expressed in various tissues, the primary HPP symptoms appear in bones and teeth. The clinical severity of HPP varies widely from the most severe (perinatal, infantile and childhood) to the mildest forms (adult, and odonto-hypophosphatasia). We reported that gene therapy using a single injection of lentiviral vector expressing bone-targeted TNAP (TNAP-D10) is effective in preventing all the skeletal of HPP in TNAP knockout (Alpl–/–) mice as the model of infantile HPP. Objective: In this study we focus on evaluating the efficacy of treatment with gene therapy on the bone and teeth using TNAP-D10 and also we investigate the feasibility of gene therapy using bone-targeted PLAP (PLAP-D10). Methods and Findings: We used Alpl–/–mice that develop skeletal disease at postnatal days 6-8 mimicking the infantile form of human HPP. We injected 100 μl of lentiviral vectors harboring TNALP-D10 (5.0 × 107 TU) or PLAP-D10 (5.0 × 107 TU) to 1-day-old Alpl–/– mice via the jugular vein. We performed histological analysis and micro-CT evaluation on bone and mandible of Alpl–/– mice. The alveolar bone, enamel and dentin defects were corrected on treated Alpl–/– mice by this treatment. Additionally the long bone growth rates (LGR) of long bones were encouraged on treated Alpl–/– mice compared with untreated mice. Conclusions: These results indicate that the bone-targeted TNAP treatment mediated by lentivirus can correct not only the bone disorder but also the dental symptoms in Alpl–/–. This study also shows that PLAP-D10 can potentially be used to correct HPP disease.
