Objective: To investigate the effects of the cyclic uniaxial compressive stress on RKIP and its mRNA in the rat condylar chondrocytes. Methods:The third-passage chondrocytes were harvested from the mandibular condyles of 2-day-old rats, and a cellular compressive stress device (self-made four-point bending system. Patent No: 01129166.4 & 01256849.x) was used to apply stress on cells at 4 000 ?strain ( 0.5 Hz frequency) for 0, 15, 30, 60, 120 and 240 min. The effects of the cyclic uniaxial compressive stress on RKIP and its mRNA in the rat mandibular condylar chondrocytes were examined by REAL-TIME PCR and Western blot. Results:The results showed that the expression of RKIP and its mRNA changed obviously with 4 000 ?strain compressive stress loading, there are reverse tendency in the expression between RKIP and its mRNA. RKIP mRNA significantly increased at 30min (P

Objective:To study the biological characteristics of condylar chondrocytes isolated from mechanical stress stimulated TMJ condylar cartilage of rats.Methods:The rat models of mechanical stress stimulated condylar cartilage were made by class III orthope-dic force for 14 days.The cartilage from control and experimental rats were observed in gross view.The cell harvest rate and viability were examined,proteomic analysis was performed.Results:After stress stimulation the thickness,the elasticity of condylar cartilage and number of chondrocytes were significantly reduced.The weight of mandibular cartilage was decreased(P<0.01).The harvest rate and the viability rate of the cells were decreased(P<0.01).The chondrocytes in the experimental group appeared to be elongated. Proteomic analysis showed that stress-related proteins,signal transduction proteins were up-regulated;cytoskeleton proteins,cell prolif-erative proteins were down-regulated.Conclusion:Mechanical stress stimulation of condylar cartilage may result in biological activity and protein changes of the condylar cartilage chondrocytes.

Humans ; Molar ; Tooth Eruption ; Tooth, Deciduous

Objective To investigate the root length of posterior teeth after palatal expansion by magnetic expansion ap-pliance. Methods A total of 32 patients who accepted palatal expansion with magnetic expansion appliance were enrolled in the study. Pretreatment and post-treatment cone-beam computed tomography (CBCT) images were obtained. A paired t test was used to evaluate the length change, and a group t test was used to compare the tooth lengths of developing and developed teeth. Results Anchorage teeth showed greater root resorption than non-anchorage teeth, whereas the developed posterior teeth showed reduced resorption. Moreover, the mesial buccal roots of the first molar and first premolar were reduced. No resorption was found in the developing teeth group. Conclusion The magnetic palatal expansion can reduce the root length, particularly of developed root. The developing root of anchorage teeth show greater tolerance to resorption than the developed root. Early palatal expansion treatment with magnetic expansion appliance can reduce the risk of root resorption.