Mineral trioxide aggregate (MTA), a commonly used endodontic repair material, is useful for both basic and clinical research, and the effect of MTA on osteoblast differentiation has been well-defined. However, the effects of MTA on osteoclastic bone resorption are not fully understood. Hence, the aim of this study is to examine the effect of MTA solution in the regulation of osteoclast bone-resorbing activity using osteoclasts formed in co-cultures of primary osteoblasts and bone marrow cells. MTA solution dose-dependently reduced the total area of pits formed by osteoclasts. The reduction of resorption induced by 20% MTA treatment was due to inhibition of osteoclastic bone-resorbing activity and had no effect on osteoclast number. A 20% MTA solution disrupted actin ring formation, a marker of osteoclastic bone resorption, by reducing phosphorylation and kinase activity of c-Src, and mRNA expressions of cathepsin K and mmp-9. A high concentration of MTA solution (50%) induced apoptosis of osteoclasts by increasing the expression of Bim, a member of the BH3-only (Bcl-2 homology) family of pro-apoptotic proteins. Taken together, our results suggest that MTA is a useful retrofilling material for several clinical situations because it both stimulates osteoblast differentiation and inhibits bone resorption.

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.

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.