[The technique characteristic and clinical application of HX straight-wire appliance].

HX straight-wire appliance (HX-SWA) is designed and adjusted by doctors of Orthodontic Department, West China College of Stomatology, Sichuan University. It is a set of appliance that is constructed according to normal occlusion features of the Chinese people, including the prescription of tip, torque, in/out, counter-tip, counter-rotation and overcorrection in brackets and buccal tubes. Some ingredients of the appliance are different from that of the most popular Roth straight-wire appliance in the world wide. Over a period of the last 10 years, doctors in our hospital kept on summarizing treatment experience with HX-SWA, which will help more doctors promote practice and results in orthodontic clinic.

[Changes of the acetylcholine receptor on rat's superficial masseter muscles after functional mandibular advancement].

OBJECTIVE: The purpose of this study was to evaluate the maximum binding (Bmax) and affinity Kd value changes of acetylcholine receptor (n-AchR) on rat's superficial masseter muscles after functional mandibular advancement. METHODS: Forty 5-week-old male SD rats were randomly divided into experimental and control groups. The mimic functional appliances were only used in experimental groups, and the rats of two groups were killed after 1, 3, 7, 14 days. Radio-ligand binding assay (RBA) was applied to determine the Bmax and Kd value of n-AchR on the superficial masseter muscles. RESULTS: The Bmax of n-AchR in experimental groups was higher than that in the control groups at all time points, and the differences had statistical significance. The Kd value of n-AchR was higher in experimental group than that in control groups in 1, 3, 7 days, while Kd value in experimental group of n-AchR was lower than that in control groups in 14 days. The differences had statistical significance in 7 and 14 days, but the differences had no statistical significance in 1 and 3 days. CONCLUSION: The functional orthopedics can increase the Bmax and affinity of n-AchR on rapid growing rat's superficial masseter muscles.

[Substance P regulates function of osteoclasts via neurokinin-1 receptor].

OBJECTIVE: To investigate the effects of substance P on cultured rat osteoclasts. METHODS: Neurokinin-1 (NK1) receptor expression in osteoclasts was examined by immunohitochemical method, and changes of bone resorption activity caused by substance P and NK1 receptor antagonists were detected by pit formation assay. RESULTS: Immunoreactivity for NK1 receptor was distributed in the cytoplasm of osteoclasts. The average of pit formation areas significantly increased with addition of substance P (10(-7)-10(-4) mol/L) (P < 0.05), but the number of pitformations did not change (P > 0.05). NK1 receptor antagonists inhibited the enhancement of the bone resorption by substance P addition. CONCLUSION: The findings suggested that substance P may stimulate osteoclasts and result in bone resorption by the mediation of NK1 receptor.

[Effects of programmed cell death on human dental follicle cells and changes of programmed cell death under different hydrostatic pressures].

OBJECTIVE: Tooth eruption requires the presence of the dental follicle (DF) around the unerupted tooth. This study is to investigate programmed cell death on human dental follicle cells and changes of programmed cell death under different hydrostatic pressures: 0, 50 and 100 kPa. METHODS: Human dental follicles from third mandibular molars were surgically removed from adolescents who need for orthodontics treatment after informed content, then trypsinized and cultured. Human dental follicle cells were divided into three groups according to different hydrostatic pressures: 0, 50 and 100 kPa and their programmed cell death were labeled by using TdT-medi-ated-dUTP nick and labeling (TUNEL). RESULTS: Dental follicle cells cultured were elongate shape and exhibited fibroblastic characteristics. Compared with 0 kPa, programmed cell death cells on human dental follicle cells were increased 0.23% and 31.65% under 50 kPa and 100 kPa hydrostatic pressures respectively. 100 kPa group increased significantly (P < 0.01). CONCLUSION: It suggested that programmed cell death occured in human dental follicle cells cultured in vitro and was influenced by different hydrostatic pressures. Hydrostatic pressure may improve tooth erup-tion through dental follicle.

[The clinic skill in fixed appliance based on characteristics of Chinese normal occlusion].

OBJECTIVE: To study the bracket placement and arch wire bending based on ethnic differences and individual differences of normal occlusion. METHODS: The prominence, tip, torque, upper first molar offset of crown and arch form between Chinese and Caucasian normal occlusion were compared. RESULTS: The results showed the ethnic differences of prominence, tip, torque, upper first molar offset of crown and arch form between Chinese and Caucasian normal occlusion. The placement of bracket was influenced by the crown morphology. CONCLUSION: The adjustments of the bracket placement and arch wire bending with Edgewise and pre-adjusted appliance are necessary to adapt to ethnic difference and individual difference.

[Cephalometric evaluation of the effects of pendulum appliance on various vertical growth patterns].

OBJECTIVE: The aim of this study was to investigate the effects of the pendulum appliance in treating dental Class II patients with various vertical growth patterns. METHODS: The samples (n = 30) were divided into three groups equally based on their FMA. Pretreatment and post-treatment cephalometric radiographs were taken to measure the changes. RESULTS: The amount of upper molar distalization in the low-angle group was the fewest, and that in the high-angle group was the most. Upper molars had been intruded insignificantly. The amount of anchorage loss at the first premolars and overjet increased at incisors was different in the three groups. The biggest change happened in the low-angle group, and the smallest in the high-angle group. CONCLUSION: The results of this study showed that pendulum appliance could move the upper molars distally in a short period of time. The upper molars in different groups were intruded insignificantly. Pendulum appliance could be used to move the upper molars distally in high-angle cases.

[The effects of growth hormone on rabbit's mandibular condylar chondrocytes proliferation and secretion in vitro].

OBJECTIVE: To study the effect of growth hormone (GH) on the proliferation and type II collagen secretion of chondrocytes of mandibular condyle in rabbit in vitro. METHODS: Flow cytometry (FCM) and immunohistochemical technique were employed to observe the possible changes. RESULTS: (1) The exogenic GH can enhance the proliferation and synthesis of DNA of the chondrocytes of mandibular condyle in rabbit in vitro. The suitable concentration of GH is 10 microg/ml. The synthesis of DNA reaches the highest level after 12 hours, while the proliferation index (PI) hits the highest after 24 hours. (2) GH (10 microg/ml) can stimulate the secretion of type II collagen of the chondrocytes. CONCLUSION: The exogenic GH can enhance the proliferation, the synthesis of DNA and the secretion of type II collagen of the chondrocytes of mandibular condyle in rabbit in vitro.

[Changes of sarco(endo)plasmic reticulum Ca2+-Mg2+-ATPase activity of cultured myoblast induced by cyclic stretch].

OBJECTIVE: To evaluate the effect of stretch on sarco(endo)plasmic reticulum Ca2+-Mg2+ ATPases activity and mRNA level and study the remodeling reaction of muscle in a variety of mechanical environments. METHODS: Myoblast from maxillofacial skeletal muscle of one-week-old male Sprague-Dawley rat was cultured and stretched cyclicly using a four-point bend device. Inorganic Phosphorus test was used to compare the activity of Ca2+-Mg2+ ATPases of myoblast before and after stretch. RT-PCR was also used to observe the Ca2+-Mg2+ ATPases mRNA level. RESULTS: The activity of Ca2+-Mg2+ ATPases of myoblast down regulated significantly in 4 hours. During the period of 8 hours to 24 hours, up-regulation followed then returned to control level at the 48 hour point. RT-PCR showed that Ca2+-Mg2+ ATPases mRNA level were elevated by stretch, particularly at 2 hour and 48 hour point. CONCLUSION: The results suggested a transcriptional control of Ca2+-Mg2+ ATPases activity was involved in the muscle remodeling process induced by stretch.

[Three-dimensional finite element analysis of maxillary canine during the tooth translation movement].

OBJECTIVE: To find the characteristic of the stress distribution in the periodontal tissue during maxillary canine distal translation. METHODS: The model was implemented numerically by means of the 3-dimensional finite element method (FEM) and was used to simulate orthodontic tooth translation movements. The finite element model was loaded with defined force systems. And the stresses at 0, 7, 14, and 21 days of loaded distal force and moment in maxillary canine were calculated. RESULTS: During the whole distal translation of canine, 1. the stress in alveolar bone was higher than that in peridontal ligament; 2. the stresses in the cervical region were higher than those in the apical region of the alveolar bone and periodontal tissues; 3. the stresses in the cervical, medium and apical regions of periodontal tissue were on the decline, and the stress in cervical region declined faster than that in apical region. On the 21st day the stresses in the cervical, medium and apical regions were similar. CONCLUSION: The 3-D FEM analysis revealed that alveolar bone loss could be most likely to happen during the initial stage of the tooth movement, and the data from this study mihgt be helpful to orthodontists in selecting an appropriate device of force systems to control the initial loading during orthodontic treatment.

[Expression of testosterone in the rapid growing rat condylar cartilage and the expression changes after the function mandibular advancement].

OBJECTIVE: To investigate the expressions of Testosterone in the condylar cartilage of rapid growing rats. METHODS: The mimic functional appliances were used in experiment groups and rats were killed after 3 days, 1 week, 2 weeks, 3 weeks and 4 weeks. Immunohistochemical technique was used to detect the expression of T. RESULTS: T was expressed throughout the condylar cartilage. The Highest expressions were in mature layers of both experiment and control groups. Along with the maturation, the expressions of T in the condylar cartilage were changed respectively, and the immunostain levels in the mature layer of experiment groups 2 and 3 weeks were higher than those of control groups (P < 0.05). CONCLUSION: 1. T is a member of cartilage growth and development control system. 2. The orthopedic mechanism of functional appliance may be conducted by T.