Orthodontic retention and adjustment of the occlusion after orthognathic surgery / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the orthodontic retention and adjustment of the occlusion after orthognathic surgery.</p><p><b>METHODS</b>18 patients were divided into three groups. Group I: Cases with skeletal Class I bimaxillary protrusion treated by subapical osteotomy; Group II: Cases with skeletal Class II mandibular retrusion treated by sagittal split mandibular advancement surgery; Group III: Cases with skeletal Class III treated by Le Fort I osteotomy on maxilla and sagittal split osteotomy on mandible. There were 6 patients in each group. Three kinds of orthodontic elastic tractions were used based on different categories of malocclusion and different types of operation.</p><p><b>RESULTS</b>18 patients attained functional occlusion after the orthodontic occlusion adjustment. There was no relapse and malocclusion by surgery.</p><p><b>CONCLUSION</b>Intermaxillary elastics based on different categories of occlusion and different kinds of surgery can improve the occlusion after orthognathic surgery and attatin the functional occlusion.</p>

Treatment of skeletal Class III adult patients with facemask protraction / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the clinical effects of facemask protraction on skeletal Class III adult patients.</p><p><b>METHODS</b>Totally 15 skeletal Class III patients (male 7, female 8, aged 18 - 24 years) were included in the study. Removable and fixed appliances were used in the upper or lower arches. Facemask protraction was used at night for about 7 months and Class III elastics were worn during the day. The total treatment time was 24 mouths on average. Cephalometric analysis was carried out before and after treatment.</p><p><b>RESULTS</b>The profile was greatly improved and Class I molar relationship was achieved. SNA angle was increased from (79.6 ± 3.7)° to (81.1 ± 3.8)°. SNB angle was decreased from (83.5 ± 3.3)° to (82.6 ± 3.6)°. ANB angle was increased from (-4.1 ± 2.0)° to (-1.5 ± 1.8)°.</p><p><b>CONCLUSIONS</b>Protraction was effective in the treatment of skeletal Class III adult patients.</p>

Effects of the first premolar extraction on the third molar angulation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the effects about inclinations of the second and the third molars in patients treated with or without premolar extractions.</p><p><b>METHODS</b>Fifty-six adolescents were chosen and divided into the first premolar extraction and non-extraction groups, 30 and 26 patients respectively. The pre-treatment and post-treatment panoramic radiographs were made. Angles between long axis of the third molar and the occlusal plane (the second molar alike), and long axis of the second and the third molar were measured and evaluated.</p><p><b>RESULTS</b>The maxillary and mandibular third molar angulations were all improved after treatment in two groups. Compared with non-extraction group, the average changes of angle between long axis of the third molar and the occlusal plane increased significantly in maxilla and mandible (P < 0.05). Average changes of angles between long axis of the second and the third molar decreased and had statistically significant difference (P < 0.05). The change of angle between long axis of mandibular second molar and the occlusal plane had statistically significant difference (P < 0.05), but there was no statistically significant difference in maxillary second molar (P > 0.05).</p><p><b>CONCLUSION</b>The first premolar extraction in orthodontic treatment could improve the third molar angulations and it would promote the eruption of the third molar.</p>

Orthodontic treatment of Class III patients with mandibular asymmetry / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the treatment outcome of Class III patients with dental, functional and mild skeletal mandibular asymmetry.</p><p><b>METHODS</b>Thirty-five patients (14 males and 21 females) with dental, functional and mild skeletal mandibular asymmetry were selected. The age range of the patients was 7 - 22 years with a mean age of 16.5 years. Dental mandibular asymmetry was treated with expansion of maxillary arch to help the mandible returning to normal position. Functional mandibular asymmetry was treated with activator or asymmetrical protraction and Class III elastics. Mild skeletal mandibular asymmetry was treated with camouflage treatment.</p><p><b>RESULTS</b>Good occlusal relationships were achieved and facial esthetics was greatly improved after orthodontic treatment in patients with dental and functional mandibular asymmetry. However, patients with skeletal mandibular asymmetry should be treated with both extraction and genioplasty.</p><p><b>CONCLUSIONS</b>Orthodontic treatment was suitable for patients with dental and functional mandibular asymmetry, while combined orthodontics and surgery could get good results in patients with skeletal mandibular asymmetry.</p>

Study on the height of marginal ridge to cusp in posterior teeth and its effect on brackets placement / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To measure the vertical height of mesio-distal marginal ridge to cusp in posterior teeth, which may be helpful to brackets positioning.</p><p><b>METHODS</b>The study groups comprised of 60 patients (30 men, 30 women, mostly aged 12-14 years) who underwent orthodontic treatment without tooth extraction and matched the Andrews normal occlusion standard after treatment. Study model of each patient was made. Three-dimensional laser measurer was used to evaluate the vertical height of mesio-distal marginal ridge to mesial cusp in posterior teeth. The data were stored in a personal computer and submitted to statistical analysis of paired t test.</p><p><b>RESULTS</b>No statistical significant difference was found in the same teeth between men and women. Not only in maxilla but also in mandible, there was no significant difference between the left and the right (P>0.05). The average vertical height of maxillary first premolars was (1.70+/-0.50) mm, the maxillary second premolars was (1.24+/-0.45) mm, and for maxillary first molars, the result was (0.83+/-0.40) mm. The difference between each result was statistically significant (P9< 0.01). The average vertical height of mandibular first premolars was (2.25+/-0.45) mm, the mandibular second premolars was (1.55+/-0.45) mm, and for mandibular first molars, the result was (1.18+/-0.40) mm. The difference between each result was statistically significant (P<0.0 1).</p><p><b>CONCLUSION</b>The vertical height of brackets position in posterior teeth should be considered to guarantee that mesio-distal marginal ridges of deferent posterior teeth located in the same plane, so that satisfying goal could be achieved, If the vertical height in the first molar was X mm, the vertical height in the second premolar should be (X+0.5) mm, and (X+1.0) mm might be suit for the first premolar.</p>

Tooth movement in tissue-engineered bone / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore the effect and practical value of repairing the alveolar defects with tissue engineering technique and investigate the influence of the generated new bone on the orthodontic tooth movement.</p><p><b>METHODS</b>The marrow stromal cells of rats were separated, cultured in vitro and induced to osteoblast-like cells. The osteoblast-like cells were implanted onto the ceramic bovine bone. Then the complex was implanted into the alveolar defect in one side of the rat's mandible. The other side of the mandible served as control. Eight weeks later, the orthodontic appliances were placed between the first molar and incisors of SD rats to move the first molar forward. The tooth movement and root resorption of the molar were observed.</p><p><b>RESULTS</b>We found that the tooth movement in the experimental area was faster than that in the normal alveolar bone (P < 0.05). The root resorption and the alveolar bone height loss were less than that in the control area (P < 0.05).</p><p><b>CONCLUSIONS</b>The tissue-engineered bone did not have negative influences on tooth movement. The repair of alveolar bone defect by tissue engineering approach may be used in craniofacial surgery and orthodontics.</p>

Cloning genes sensitive to mechanical stretch in osteoblasts through subtractive hybridization technique / 华西口腔医学杂志

<p><b>OBJECTIVE</b>In this experiment, genes sensitive to mechanical stretch in osteoblast like cells were cloned through subtractive hybridization technique.</p><p><b>METHODS</b>Two dimensional mechanical stretch with deformation of 12% and frequency of 6 cycles was loaded on human osteoblastic like cell line Saos-2. Complementary deoxyribonucleic acid (cDNA) library of cells was constructed 12 h after loading, acting as tester. cDNA library of cells without loading was constructed, acting as driver. A subtractive cDNA library osteoblastic like cell stimulated with mechanical stretch was constructed through subtractive hybridization technique.</p><p><b>RESULTS</b>Of clones randomly selected from this library, fifteen genes were identified to be the differentially expressed genes. Comparing with the sequences published in GeneBank via Internet, two sequences located in chromosome 9 and 18 respectively were identified to be novel, which were named as stretch sensitive gene 1 and stretch sensitive gene 2.</p><p><b>CONCLUSION</b>It is an efficient approach to clone and study genes relative to mechanical stretch through subtractive hybridization technique.</p>

Clinical research on unilateral extraction for moderate crowding / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To clinically investigate the results of unilateral extraction in the treatment of special moderate crowding cases.</p><p><b>METHODS</b>22 patients with harmonic profile and moderate crowding were selected and treated by unilateral extraction with Edgewise technique. The patients crowding was 6 - 9 mm and focused on one side of the arch. 22 patients with moderate crowding were treated by bilateral extraction as control.</p><p><b>RESULTS</b>22 patients have been treated successfully within 18 months. Crowding was completely resolved. Midline coincidence was basically maintained.Good intercuspation was achieved. There is no significant difference in dental arch symmetry between unilateral extraction and bilateral extraction (P > 0.05).</p><p><b>CONCLUSION</b>Unilateral extraction can be successful in the treatment of special moderate crowding cases.</p>

Orthodontic treatment of malocclusion with mandibular congenital missing teeth guided by Bolton index / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the outcome of the treatment of malocclusion with mandibular congenital missing teeth guided by Bolton index.</p><p><b>METHODS</b>26 class I and II cases (males 10, females 16) were chosen in this study. Guided by Bolton index, enamel stripping, denture and two types of tooth extraction were used in the treatment.</p><p><b>RESULTS</b>Normal Bolton index was achieved and the results of treatment were satisfactory.</p><p><b>CONCLUSIONS</b>Malocclusion with mandibular congenital missing teeth can be treated successfully guided by Bolton index.</p>

Effect of elastic stress on expression of corebinding factor a 1 mRNA in human periodontal ligament cells in vitro / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the osteoblast-like characteristics of human periodontal ligament cells affected by elastic stress in vitro, and the role of corebinding factor a 1 (cbfa1) in alveolar bone formation during orthodontic tooth movement.</p><p><b>METHODS</b>Rat dig-labeled cbfa1 cDNA probe was prepared from SD rat osteoblasts cultured in vitro. Human periodontal ligament cells were cultured on the elastic bottom plate and stimulated by elastic stress using mechanical loading system for cultured cells in vitro. The expression of cbfa1 mRNA was detected by in situ hybridization method.</p><p><b>RESULTS</b>Cbfa1 mRNA express in human periodontal ligament cells stimulated by elastic stress and did not express in normal human periodontal ligament cells.</p><p><b>CONCLUSION</b>It is suggested that elastic stress plays a role in the differentiation process from human periodontal ligament cells to osteoblast-like cells. Cbfa1 is a transcription factor in alveolar bone remodeling during orthodontic tooth movement.</p>

Development of an analysis system for X-ray cephalometry by Windows platform / 中国医疗器械杂志

Here in this paper introduced is an analysis system for X-ray cephalometry developed through Windows platform,which includes three parts: data input, cephalometry analysis & calculation, and display & printing of diagnostic results. It has been applied in orthodontic department of Stomatological Hospital of the Fourth Military Medical University, and it is quite convenient for doctors' cephalometry diagnosis.