The periodontal ligament (PDL), a connective tissue located between the cementum of teeth and the alveolar bone of mandibula, plays a crucial role in the maintenance and regeneration of periodontal tissues. The PDL contains fibroblastic cells of a heterogeneous cell population, from which we have established several cell lines previously. To analyze characteristics unique for PDL at a molecular level, we performed cDNA microarray analysis of the PDL cells versus MC3T3-E1 osteoblastic cells. The analysis followed by validation by reverse transcription-polymerase chain reaction and immunochemical staining revealed that endoglin, which had been shown to associate with transforming growth factor (TGF)-beta and bone morphogenetic proteins (BMPs) as signaling modulators, was abundantly expressed in PDL cells but absent in osteoblastic cells. The knockdown of endoglin greatly suppressed the BMP-2-induced osteoblastic differentiation of PDL cells and subsequent mineralization. Interestingly, the endoglin knockdown did not alter the level of Smad-1/5/8 phosphorylation induced by BMP-2, while it suppressed the BMP-2-induced expression of Id1, a representative BMP-responsive gene. Therefore, it is conceivable that endoglin regulates the expression of BMP-2-responsive genes in PDL cells at some site downstream of Smad-1/5/8 phosphorylation. Alternatively, we found that Smad-2 as well as Smad-1/5/8 was phosphorylated by BMP-2 in the PDL cells, and that the BMP-2-induced Smad-2 phosphorylation was suppressed by the endoglin knockdown. These results, taken together, raise a possibility that PDL cells respond to BMP-2 via a unique signaling pathway dependent on endoglin, which is involved in the osteoblastic differentiation and mineralization of the cells.
Regional odontodysplasia is a rare, severe, and nonhereditary developmental disorder in tooth formation and involves epithelial and mesenchymal-derived dental tissue. On radiographs, affected teeth have an abnormal morphology, a hypoplastic crown, and only a faint outline of hard tissue, a condition termed “ghost teeth.” We report clinical and radiographic findings from two children with regional odontodysplasia. Using computed tomography (CT), we calculated attenuation coefficients (i.e., Hounsfield units) for affected teeth and assessed the condition of dental follicles. To measure density, regions of interest were delimited and CT values were calculated. In our two patients, the CT values for enamel were lower in affected teeth than in sound teeth, while CT values for dentin were similar for affected and sound teeth. The average CT value for dental follicles in affected teeth was about 65 to 120, which suggests that dense fibrous connective tissues or hard tissue-like structures might be present in dental follicles. Analysis of CT values may be quite useful in the diagnosis and treatment of regional odontodysplasia.
Regional odontodysplasia is an unusual non-hereditary developmental anomaly of tooth structures in both primary and permanent dentitions. The appropriate treatment differs for each individual's clinical findings. The purpose of this study was to describe the clinical findings and the long-term progress as to the treatment and the management of a male patient who was diagnosed with regional odontodysplasia on the left side of the mandible. The mandibular left primary molars had shown a remarkable "ghost-like" appearance on x-ray, but they had already been extracted by an oral surgeon because of osteomyelitis due to pulpal infection, when the patient was referred to our pediatric dental clinic at 5 years of age. According to x-ray findings, the five permanent teeth (32,33, 34, 35, 36) on the mandibular left side were delayed in formation. During the 15 years from age 5 to age 20, the patient was treated and managed in our clinic and the prosthodontic clinic of our hospital. Because the patient lost his mandibular left primary teeth early but presented delayed eruption of succedaneous permanent teeth, the patient used a temporary removable space maintainer for a long time. Although the affected first molar was extracted, the second premolar erupted and the other three unerupted teeth were not removed. The edentulous region was rehabilitated with a removable partial acrylic prosthesis when the patient was 19 years and 4 months. It was found that a multidisciplinary approach was essential for the long-term follow-up of typical regional odontodysplasia.
The aim of the present study was to examine the prevalence rate and treatment outcome of maxillary canine transposition in Japanese children according to the conventional standard and our new additional consideration of the classification. From 140 cases with ectopic canines diagnosed in the Pediatric Dental Clinic of Niigata University Medical and Dental Hospital, we selected 10 transposition cases as the present subjects. Out of 10 cases, 4 were males and 6 females. Six were classified into type A: the mesio-distal positional interchange of the canine and the first premolar, 2 cases into type B: the mesio-distal transposition of the canine and the lateral incisor, and the other 2 cases into type C: the present new classification that showed the vertical transposition of the canine and the first premolar within the developmental bone. The prevalence rate of types A and B resembled the previous papers regarding the ratio of sex and bilateral occurrence. Although 3 cases in type A, one case in type B and one case in type C could finally be aligned in the normal tooth order, every one of the types A and B cases were aligned in the reverse order. For every one case in types A and C, the transposed canines were extracted. It is recommended that pediatric dentists take an orthopantomogram during early mixed dentition as a routine practice in order to detect anomalies of tooth eruption, such as tooth transposition, as early as possible. and that transposition between the canine and the first premolar appears most often (70%) in maxillary dentition, followed by the one between the canine and lateral incisor (20%) 1). In Japanese children, however, the prevalence rate or the treatment course of canine transposition has not been documented. Many previous articles on tooth transposition 1,2,5-10) have described the horizontal (mesio-distal) tooth relationship, but have not mentioned the vertical interchange of two adjacent teeth buds during preeruptive dental development. In order to examine the development or the eruptive movement of the permanent tooth germ, the pediatric dentist usually takes x-ray photographs during mixed dentition. On these x-ray photographs, we can sometimes discover the positional anomaly that can be called vertical tooth transposition.
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