Study of tooth drifts after orthodontic extractions in cases of interruption / 口腔疾病防治

Objective @# To compare the tooth drift differences between different types of patients after orthodontic extraction for 1.5 months (45 days) without return to the clinic on time for some reasons.@*Methods@#This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. A total of 84 patients had bilateral premolars extracted but were not bonded the bracket for some reasons. The upper and lower jaw dental models were cast, scanned, and reconstructed in 3D. Patients were divided into 12 groups based on extraction positions (first premolar or second premolar), jaw types (maxilla or mandible) and vertical facial types (average angle, high angle, or low angle). Multivariate analysis of variance was used to analyze the changes in the following five indicators in different types of patients who were interrupted for 1.5 months after extraction: anterior tooth crowding, width between canines, width between first molars, tooth extraction space, and overbite of anterior teeth. @*Results @#The tooth extraction position, jaw type and vertical facial type had an effect on the reduction in tooth extraction space and anterior tooth crowding before and after the sudden emergent state (1.5 months after tooth extraction) (P<0.001), and the tooth extraction position and vertical facial type had an effect on the increase in anterior tooth overbite (P<0.001). The drift of bilateral adjacent teeth was greater in patients with first premolars extracted than in those with second premolars extracted (P<0.001), and the drift of bilateral adjacent teeth in the maxilla was larger than that of the mandible (P<0.001). The drift of bilateral adjacent teeth in patients with high angles was more obvious than that of patients with average angles and low angles (P<0.001). @* Conclusion@# For orthodontic patients who have maxillary tooth extraction, first premolar extraction, and even high angles in the vertical facial type, the bilateral adjacent teeth are easier to drift, orthodontic treatment should be carried out soon after extraction, and attention should be given to anchorage control.

Evaluation of buccolingual molar inclinations among different vertical facial types / 대한치과교정학회지

OBJECTIVE: The aim of this study was to compare the buccolingual inclination of maxillary and mandibular molars in adults with different vertical facial types. METHODS: Cone-beam computed tomography images of 135 adult patients (age, 20–45 years) with skeletal Class I maxillomandibular relationships were assigned to normodivergent (n = 46), hypodivergent (n = 49), and hyperdivergent groups (n = 40) according to linear and angular sella-nasion/gonion-menton measurements. The normodivergent group consisted of 24 females and 22 males, hypodivergent group of 26 females and 23 males, and hyperdivergent group of 24 females and 16 males. Buccolingual inclination of the maxillary and mandibular first and second molars was measured relative to the occlusal plane. One-way analysis of variance was used for intergroup comparison. Gender differences were evaluated using independent t-tests. RESULTS: Buccolingual molar inclinations did not differ significantly between females and males (p > 0.05). There were no statistically significant differences among the buccolingual inclinations of the first and second maxillary and mandibular molars of the groups (p > 0.05). CONCLUSIONS: Buccolingual inclinations of maxillary and mandibular molars are similar in normodivergent, hyperdivergent, and hypodivergent adults with Class I sagittal relationships.

The relation between the upper first molar root tips and the maxillary sinus floor in patients with different vertical facial patterns / 口腔疾病防治

Objective@#To study the relation between the upper first molar root tips and the maxillary sinus floor in patients with different vertical facial patterns using cone-beam computed tomography (CBCT) and to explore the reference data for safe clinical orthodontic treatments.@*Methods@#Three-dimensional images were reconstructed from CBCT data. The CBCT data from 120 adolescents and adults were divided into three groups (low-angle group, average-angle group, high-angle group) based on vertical facial type. For each subject, the distance from the maxillary sinus floor to the upper first molar root tips was measured, and the types of contacts were classified. ANOVA and LSD t tests were used for statistical comparisons and performed using SPSS 19.0.@*Results@#Of the 120 samples, only 27% of the upper first molar root tips lost their contacts with the maxillary sinus floor, and the other 73% of the root tips contacted the sinus to different extents. Significant differences in the distances from the maxillary sinus floor to the upper first molar root tips were found for different vertical facial types (P < 0.05). The high-angle group had the lowest sinus floor, relative to the root tips, of the three adult groups (P < 0.05). In the adult group with a low angle, the measured value for the palatal root tips was the lowest and was significantly different from those in the other groups (P < 0.05).@*Conclusion@#Seventy-three percent of the upper first molar root tips contacted the maxillary sinus floor. The maxillary sinus floor tended to be lower relative to the first molar root tips in patients with a high-angle facial pattern than in others. The roots protruded into the sinus to a greater extent.

The relationship between arch width and vertical facial skeletal types of the adults with individual normal occlusion / 实用口腔医学杂志

Objective:To analyze the correlation between arch width and different vertical facial skeletal types of the adults with individual normal occlusion.Methods:52 adults with individual normal occlusions(females 31,males 21) were included.According to the values of mandibular plane angle MP-FH,SN-MP measured on CBCT image the subjects were divided into 3 groups(13 cases with highangle,19 with average-angle and 20 with low-angle groups).12 parameters were measured for each sample,including maxillary and mandible arch width and alveolar arch width between canines,between first premolars and between first molars,the difference between the maxillary arch width and mandibular arch width were calculated.The data were statistically analyzed by one-way ANOVA and Pearson~ rank correlation test.Results:In the group of high-angle,average-angle and low-angle the alveolar arch width(mm) between maxillary canines was 38.03 ± 1.90,39.65 ± 1.80 and 39.78 ± 2.20 respectively(P ＜ 0.05).The arch width between maxillary first premolars of high-angle group(37.01 ± 1.60) was smaller than that of low-angle group(38.65 ± 1.30).The arch width difference in canine area between maxillary and mandibular alveolar in high-angle,average-angle and low-angle groups was 7.39 ± 1.82,9.04 ± 1.43 and 9.26 ± 1.67 respectively(P ＜0.05);in maxillary first premolars area in high-angle(6.8 ± 1.59) was smaller than that in averageangle(7.79 ± 1.09),maxillary and mandibular arch width showed no statistical difference.Pearson correlation test showed that among 3 groups,upper and lower alveolar arch width difference in canine and first premolars area was negatively correlated with the mandibular plane angle.while upper and lower arch width difference showed no statistical correlation with the mandibular plane angle.Conclusion:The maxillary middle arch width of the subjects with individual normal occlusion was correlated with vertical facial type.

A CBCT study of alveolar bone structure around incisors of the patients with verical facial type of skeletal Class Ⅱ / 实用口腔医学杂志

Objective:To investigate the structure of alveolar bone around incisors in patients with verical facial type of skeletal ClassⅡ by CBCT.Methods:60 skeletal Class Ⅱ patients were divided into low angle,average angle and high angle cases(n =20)by FMA.CBCT scanning was made and the thickness of the labial and lingual alveolar bone around the incisors in each subject was meas-ured.The measurements were analyzed using ANOVA.Results:The total width of alveolar bone at the root apical level of maxillary and mandibular incisors,the lingual thickness of alveolar bone at the root midpoint of maxillary incisors and labial thickness of alveolar bone at the root midpoint of mandibular incisors in the high angle cases were thinner than that in the average and low angle cases(P <0.05),but there was no significant difference in labial thickness of alveolar bone at the crest among 3 groups.Conclusion:The alveo-lar bone thickness around incisors of high angle patients is thinner,more attention should be paid for the alveolar bone absorpation and tooth root exposure in these patients.

Differences in the mandibular premolar positions in Angle Class I subjects with different vertical facial types: A cone-beam computed tomography study / 대한치과교정학회지

OBJECTIVE: To compare the positions of the mandibular premolars in Angle Class I subjects according to vertical facial type. The results will provide a theoretical basis for predicting effective tooth movement in orthodontic treatment. METHODS: Cephalometric parameters were determined using cone-beam computed tomography in 120 Angle Class I subjects. Subjects were categorized as short, normal, and long face types according to the Frankfort mandibular angle. Parameters indicating the position of the mandibular right premolars and the mandible were also measured. RESULTS: The angle between the mandibular first premolar axis and buccal cortex, the distance between the root apex and buccal cortex, angle of vestibularization, arc of vestibularization, and root apex maximum movable distance were significantly greater in the short face type than in the long and norm face types. The angle between the mandibular second premolar axis and buccal cortex, the distance from root apex to buccal cortex, and the arc of vestibularization were significantly greater in the short face type than in the normal face type. CONCLUSIONS: There are significant differences in the mandibular premolar positions in Class I subjects according to vertical facial type.

Upper airway form and hyoid position of the adults with different vertical facial types / 实用口腔医学杂志

Objective:To study the difference of upper airway form and hyoid position of the adults with different vertical facial types.Methods:Cephalograms of 120 adults with different vertical facial types were retrospectively investigated by computerized cephalometric analysis.Upper airway depths and hyoid position were measured,and differences were compared between male and female,also compared among different vertical facial type groups.Results:The sagittal depth of upper airway in male was larger than that in female,but there was no statistical difference except V-LPW.Among different vertical facial types,the sagittal depths of upper airway in high angle group was smaller than that in average angle group and low angle group.There was statistical difference in hyoid position between genders,AH-SN,AH-FH and AH-C3 in male were larger than in female(P

Upper airway forms of the adults with classⅡsagittal facial type / 实用口腔医学杂志

Objective:To analyze the characteristics and differences of upper airway forms in the adults with class Ⅱ sagittal facial type of different vertical facial types and investigate the correlation between craniofacial structures and upper airway forms.Methods:Cephalograms of 135 adults with classⅡsagittal facial type of different vertical facial types were collected.60 cases were males and 75 cases were females.All the cephalograms were measured in sagittal upper airway depths.The differences were compared between genders,and also among different vertical facial type groups.Results:Among different vertical facial type groups,only the sagittal depths of nasopharynx(PNS-Ba、PNS-R)of the males and PNS-Ba of the females in high angle groups were smaller than that in average and low angle groups(P0.05),but the values of V-LPW of the males were larger than that of the famales in all vertical facial type groups(P

Comparison of cranial base morphology between high-angle and low-angle malocclusion patients / 实用口腔医学杂志

Objective:To compare the differences of cranial base morphology between high-angle and low-angle malocclusion patients with geometric morphometrics.Methods:Pretreatment lateral cephalograps of 80 skeletal Class I patients(40 hypodivergent,40 hyperdivergent)were selected.All cephalographs were scanned,and 13 homologous landmarks of cranial base were identified and digitized.Average geometries of cranial bas e were created by means of Procrustes analysis.Thin-plate spline analysis was applied to cranial base configurations to determine local morphology differences between the two vertical facial types.Results:1.high-angle patients had the cranial base characteristics as follow:(1)Horizontal and vertical expansion occured in the sphenoida region,(2)The anterial and posterior cranial bases circled S point opposite direction revolving,which caused cranial base angle to reduce significantly.2.The low-angle the cranial base characteristics was just opposite with high-angle′s.Conclusion:The shape of cranial base was different between high-angle and low-angle malocclusion patients.

Relation of condylar morphology with different vertical facial types in the development of patients with skeletal Ⅲ malocclusions / 实用口腔医学杂志

Objective: To study the relation of condylar morphology with different vertical facial types in the development of patients with skeletal Ⅲ malocclusions. Methods:180 cases with skeletal Ⅲ malocclusion were divided into children(5-11 years old), adolescence(12-17 years old) and adult(18-30 years old) groups with 60 cases in each group. Orthopantomograms of the patients with different vertical facial types were retrospectively investigated by computerized cephalometric analysis. Condylar morphology were compared among different age groups of the same vertical facial type. Results:In patients with high angle, ramus height(RH) was getting bigger with ageing(P0.05). In patients with low angle h and RH in adult group were bigger than those in adolescence or in children(P