This study suggests that burnout is a common problem in Korean dentists and that occupational calling and willing to reselect a dentistry as a job are important factors for managing burnout.

The alveolar ridge was preserved clinically and histologically in both groups. rhBMP-2/HA resulted in greater new bone formation than bovine bone 3 months after the surgery.

Support provided by the Industrial Strategic Technology Development Program (10062635, New hybrid milling machine with a resolution of less than 10 mm development, using open CAD/CAM S/W integrated platforms for 1-day prosthetic treatment of 3D smart medical care system) funded by the Ministry of Trade, Industry, and Energy (MOTIE, Korea); and the industrial infrastructure program of laser industry support, which is funded by the Ministry of Trade, Industry, and Energy (MOTIE, Korea, N0000598).

This study evaluated the anatomical profile of the mesial root canals of the Burmese mandibular first molar with Vertucci's type IV canal configuration (VT4) using microcomputed tomography analysis. Seventy-five mesial roots of extracted mandibular first molars were scanned and evaluated. Fourteen middle mesial canals (MMCs) were observed in the specimens; each specimen had an average of 1.63 lateral canals and 3.77 apical foramina. The lateral canals arising from the mesiobuccal canal, mesiolingual canal, MMC, and isthmus terminated at an average distance of 0.92, 0.73, 2.11, and 1.89 mm, respectively, from the apex. The mean distance between the centers of the mesiobuccal and mesiolingual canals at 1.5 mm coronal to the furcation was 2.60 mm. A higher incidence of isthmus was observed in the apical 2-6-mm region compared with the apical 0-2-mm region (P < 0.05). The incidence of lateral canals in the isthmus was similar to that of the mesiobuccal and mesiolingual canals (P > 0.05). This study shows that the mesial root of the Burmese mandibular first molar with VT4 has complex anatomical profiles comprising MMCs and isthmus and their lateral canals.

In mouse tooth development, the roots of the first lower molar develop after crown formation to form 2 cylindrical roots by post-natal day 5. This study compared the morphogenesis and cellular events of the mesial-root-forming (MRF) and bifurcation-forming (BF) regions, located in the mesial and center of the first lower molar, to better define the developmental mechanisms involved in multi-rooted tooth formation. We found that the mesenchyme in the MRF showed relatively higher proliferation than the bifurcation region. This suggested that spatially regulated mesenchymal proliferation is required for creating cylindrical root structure. The mechanism may involve the mesenchyme forming a physical barrier to epithelial invagination of Hertwig's epithelial root sheath. To test these ideas, we cultured roots in the presence of pharmacological inhibitors of microtubule and actin polymerization, nocodazole and cytochalasin-D. Cytochalasin D also inhibits proliferation in epithelium and mesenchyme. Both drugs resulted in altered morphological changes in the tooth root structures. In particular, the nocodazole- and cytochalasin-D-treated specimens showed a loss of root diameter and formation of a single-root, respectively. Immunolocalization and three-dimensional reconstruction results confirmed these mesenchymal cellular events, with higher proliferation in MRF in multi-rooted tooth formation.