Mineral trioxide aggregate solution inhibits osteoclast differentiation through the maintenance of osteoprotegerin expression in osteoblasts.

Mineral trioxide aggregate (MTA) is a therapeutic, endodontic repair material that is reported to exhibit calcified tissue-conductive activity. The aim of this study was to investigate whether MTA may prevent osteoclast differentiation in vitro. MTA solution, but not other commonly used retrofilling materials, such as Dycal, Super-EBA, or intermediate restorative material (IRM) solution, dose-dependently inhibited osteoclastogenesis in cocultures of mouse bone marrow cells (BMCs) with primary osteoblast cells (POBs) induced by 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2) D(3) ]. Exogenous CaCl(2) medium supplementation did not inhibit osteoclastogenesis in cocultures. Furthermore, MTA solution did not affect receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis, suggesting that POBs are targets of MTA. MTA solution suppressed the 1α,25(OH)(2) D(3) -induced reduction of osteoprotegerin (OPG) mRNA and protein production without changing RANKL expression in POBs. Consistent with this result, MTA solution did not inhibit osteoclastogenesis in cocultures of BMCs and POBs from OPG-deficient mice. Therefore, the maintenance of OPG expression in POBs appears to be critical for the inhibitory effect of MTA solution on osteoclast differentiation.

Developmental anomalies of permanent lateral incisors in young patients.

OBJECTIVE: To elucidate the prevalence of developmental anomalies of permanent lateral incisors among young patients in Japan. STUDY DEIGN: A total of 1375 patients were observed between 1990 and 2008 at the Department of Pediatric Dentistry in the Kyushu Dental College Hospital and four private pediatric dental clinics in Kitakyushu City. Panoramic and periapical radiographs were examined for all those patients aged 5 to 19 years. RESULTS: The prevalence of agenesis of the lateral incisors was 7.3% (100 patients), with more girls than boys being affected. The prevalence rates of absent upper and lower lateral incisors were 2.7 and 4.8% (34 and 63 patients), respectively. Nine (0.7%) of the total patients had microdontia. Eruption disturbance was present in five patients (0.4%). Two of five patients presented with a disturbed eruption owing to an odontoma or a supernumerary tooth. CONCLUSION: In our study, the prevalence of agenesis of the lateral incisors was higher in Japanese children than in other populations, and eruption disturbance occurred less frequently than agenesis and microdontia. Nevertheless, the early differential diagnosis of an eruption disturbance is important in order to begin appropriate treatment at the optimal time.