Expression of wingless-type MMTV integration site family member 3 in rat dental follicle tissues and cells undergoing osteogenic differentiation / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the expression of wingless-type MMTV integration site family, member 3 (Wnt3) in rat dental follicles and its protein level in dental follicle cells (DFC) undergoing osteogenic induction and to discuss the effects of Wnt3 on the differentiation of DFC.</p><p><b>METHODS</b>Rats at postnatal days 1, 3, 5, 7, 9, 11 and 13 were executed, then the mandibles were immediately removed and immunohistochemistry was performed to detect the expression of Wnt3 in dental follicles of postnatal rats. The expression and distribution of Wnt3 in DFC were determined by immunofluorescence. Alizarin red-S staining was performed to assess the mineralization of DFC. Western blotting was used to evaluate Wnt3 and β-catenin protein levels after stimulated by osteogenic medium for 1, 2 and 3 weeks, respectively.</p><p><b>RESULTS</b>Immunohistochemistry revealed that the expression of Wnt3 in rat dental follicles began at day 5 and sustained to day 13. On day 1 and 3, the expression of Wnt3 in dental follicles was negative.Wnt3 was expressed in the cytoplasm of DFC. Alizarin red-S staining indicated that the osteogenic medium stimulated the differentiation of DFC into osteoblastic lineage.Western blotting demonstrated that the Wnt3 protein levels were significantly up-regulated after stimulated with osteogenic medium for 1 weeks compared with the control (2.60 ± 0.04 vs.1.00 ± 0.00, P < 0.05). Then the levels of Wnt3 protein were declined, and at the 3rd week, no significant difference was observed between osteo-induced group and the control (1.00 ± 0.05 vs.1.00 ± 0.00, P > 0.05). The levels of β-catenin were increased in osteo-induced groups compared with the control (1.95 ± 0.05 vs.1.00 ± 0.00, P < 0.05; 9.77 ± 0.65 vs.1.00 ± 0.00, P < 0.05;1.75 ± 0.21 vs.1.00 ± 0.00, P < 0.05). Furthermore, the expression of β-catenin reached to a peak on the 2nd week (9.77 ± 0.65), and then declined.</p><p><b>CONCLUSIONS</b>Wnt3 was expressed in the rat dental follicles both in vivo and in vitro and up-regulated during early phase of osteoblast differentiation in DFC.Wnt3 may be involved in early phase of osteoblast differentiation.</p>

Biomechanical analysis on periodontal ligament in dynamic jaw / 医用生物力学

Objective To investigate the influences of loading time and loading angle on the stress, displacement of human periodontal ligament in dynamic jaw. Methods The three-dimensional assembly model of the mandible front teeth, periodontal ligament and alveolar bone was reconstructed by using the reverse engineering technology. The thickness of periodontal membranes was 0.2 mm. The stress, displacement at different positions of the periodontal ligaments during different jaw cycles were analyzed under dynamic load in the direction from bucca to tongue side with 0°, 15°, 30°, 45°, 60°, 75°, 90° angle to the long axis of the tooth. Results During one jaw cycle, the ratio of the maximum to minimum value of the maximum residual stress due to different loading angles was 5.5, and the ratio of the maximum to minimum value of the maximum displacement was 8.1. The ratio of the maximum to minimum value of the maximum displacement which was caused by five jaw cycles was increased in the range from 1.02 to 1.35 with the increase of loading angles. The ratio of the maximum to minimum value of the maximum residual stress which was caused by different loading angles was increased in the range from 1.86 to 3.00 with the increase of jaw cycles. The location of the maximum stress was at the tongue side of the cervical margin at different loading angles, and the location of the maximum residual stress was distributed at different positions of the cervical margin. Most stress was accumulated at the root of the periodontal ligament under the 0° dynamic load. Conclusions The situation of the accumulated residual stresses and the uncertainties in the distribution of the maximum residual stresses should be observed in the clinical choice of mandible incisors fixed by bridge abutments; large angle force applied to the tooth was harmful to the periodontal ligament and rapid succession of chewing hard food should be avoided as much as possible during the clinical treatment.