拔牙与非拔牙矫治后牙弓宽度及颊廊变化的对比研究

目的比较拔牙矫治与非拔牙矫治对牙弓宽度及颊廊的影响,并探讨颊廊与牙弓宽度改变的关联性。方法收集符合要求的拔牙矫治与非拔牙矫治患者各50例,用石膏模型测量牙弓宽度,用正面自然微笑相测量颊廊宽度,比较拔牙矫治前后牙弓宽度及颊廊宽度的改变量、非拔牙矫治前后牙弓宽度及颊廊宽度的改变量,研究拔牙对牙弓宽度及颊廊宽度的影响,并通过分析牙弓宽度的改变量与颊廊宽度的改变量之间的关联性来探究拔牙与否对牙弓宽度及颊廊宽度的影响是否存在相关性。结果 1拔牙组矫治后的上尖牙牙弓宽度增加,非拔牙组无明显增加;2拔牙组与非拔牙组矫治后前磨牙宽度均有所增加,但拔牙组增加量大于非拔牙组;3拔牙组与非拔牙组矫治后上颌第一磨牙间的宽度均有所增加,但非拔牙组增加量大于拔牙组;4拔牙组与非拔牙组矫治前后的颊廊宽度均无统计学差异;5拔牙组与非拔牙组矫治前最后可视磨牙的宽度、矫治后尖牙牙弓宽度与颊廊宽度有相关性。结论 1矫治前后牙弓宽度的改变与拔牙与否有关;2矫治前后颊廊的改变与拔牙与否无关;3牙弓宽度的改变与颊廊的改变在大多数情况下无直接的相关性。     

Dental arch widths and mandibular-maxillary base widths in Class II malocclusions between early mixed and permanent dentitions

The aim of the study was to analyze the transverse morphology and development of the dental arches and skeletal mandibular-maxillary bases in untreated Class II malocclusions. Using the records of the Belfast Growth Study, a Class II division 1 group (II/1) and a Class II division 2 group (II/2) were compared with a Class I group and a control group with good occlusion. On posteroanterior cephalograms, maxillary skeletal base width and bigonial and biantegonial widths were determined at two-year intervals between seven and 15 years. Maxillary and mandibular intermolar widths were measured on the associated study casts. As a result, maxillary skeletal base widths were smallest in the Class II/1 subjects. No statistically significant differences were found among the groups for the skeletal mandibular widths. With respect to the development of the dental arches, maxillary intermolar widths were smaller in the Class II/1 group than in the Class I and the good-occlusion groups. These group differences were present for the total period of observation, ie, seven to 15 years, and statistically significant at most ages. When the relative difference between the maxillary and the mandibular intermolar widths was examined, the Class II/1 cases were found to have the largest average difference (about -2.5 mm for boys and -1.5 mm for girls), indicating a relatively narrow maxillary arch. Less pronounced molar differences were found in the Class II/2 group. In the Class II/1 subjects the deviations in molar differences observed at 15 years of age were established already at 7 years of age and maintained during 7 and 15 years of age.     

Extraction vs nonextraction: arch widths and smile esthetics

Dental casts of 30 patients treated with extraction and 30 patients without extraction of four first premolars were randomly selected to determine changes in arch width as a result of treatment. Arch widths were measured from the cusp tips of the canines, premolars, and molars. Posttreatment arch widths were also measured in the midline at a constant arch depth from the most labial surfaces of the incisors. Standardized frontal photographs of the face taken during smiling of 12 extraction- and 12 nonextraction-treated subjects were evaluated. Fifty laypersons judged the esthetics of the smiles. Intercanine width increased less than one mm in both groups, and there was no difference between the two groups. The interpremolar and intermolar distance in both arches decreased significantly from 0.53 to 0.95 mm in the extraction sample, whereas the interpremolar and intermolar widths increased significantly from 0.81 to 2.10 mm in the nonextraction sample. When arch widths of both groups were measured from the most labial surfaces of the teeth at a constant depth, the average arch width of both arches was significantly wider in the extraction sample (1.8 mm wider in the mandible and 1.7 mm wider in the maxilla). The mean esthetic score and the number of teeth displayed during a smile did not differ between the groups. The results indicate that arch width is not decreased at a constant arch depth because of extraction treatment, and smile esthetics are the same in both groups of patients.     

Dental and alveolar arch widths in normal occlusion and Class III malocclusion

The aim of this study was to compare the transverse dimensions of the dental arches and alveolar widths of Class III malocclusion group with a group of untreated normal occlusion subjects. This study was performed using measurements on dental casts of 150 normal occlusion (mean age, 21.6 +/- 2.6 years) and 100 Class III malocclusion (mean age, 15.4 +/- 2.2 years) subjects. Independent samples t-test was applied for comparing the groups. The findings of this study indicated that the mandibular intercanine and intermolar alveolar widths were significantly larger in the Class Ill group when compared with the normal occlusion sample (P < .001). Maxillary interpremolar, intermolar widths and all maxillary alveolar width measurements were significantly narrower in the Class III group (P < .001). In addition, the lower canine and premolar alveolar width measurements were also statistically significantly larger in the normal occlusion group when compared with the Class III malocclusion group (P < .001). Subjects with Class III malocclusion tend to have the maxillary teeth inclined to the lingual and mandibular teeth inclined to the buccal direction because of the restriction of maxillary growth and development according to dental arch width measurements. Therefore, rapid maxillary expansion should be considered before or during the treatment of a Class III patient with or without face-mask therapy.     

Bolton tooth size ratio and its relation with arch widths,arch length and arch perimeter: A cone beam computed tomography (CBCT) study

Objective. The prime aim of the study was to measure and compare the 3D CBCT Bolton tooth size ratio in relation to the upper and lower arch widths, arch length and arch perimeter. Materials and methods. The data source was CBCT high volumetric data from the archives. Tooth size, arch widths, arch length and arch perimeter were measured in maxilla and mandibular arches. The independent t-test and ANOVA were used for statistical analyses. Results. The female Bolton anterior ratio (BAR) (78.373) and Bolton overall ratio (BOR) (93.231) show a greater tooth size ratio in comparison to male BAR (77.162) and BOR (93.124), respectively. However, no significant difference was found in the sexual comparison of all the measurements. Tooth size ratio in arch width groups also showed no significant difference. Significant discrepancies in the arch length (p < 0.05) groups and overall ratio and in the arch perimeter groups (p < 0.05 and p < 0.01) and anterior ratio were revealed. Conclusions. Tooth size ratios during orthodontic treatment for different arch length and arch perimeter groups need to be evaluated carefully.     

牙列拥挤与前突病例拔牙矫正后牙弓宽度变化对比研究

目的：通过研究尖牙、第一磨牙及第二磨牙间宽度的变化,对比牙列拥挤和牙列前突病例以及年龄因素对拔牙矫治前后牙弓宽度变化的影响。方法：随机选择60例拔除四个第一前磨牙MBT矫治技术治疗患者,分为拥挤组和前突组及16岁以上组和16岁以下组进行对比研究,取治疗前后记存模型进行测量,并经统计学分析。结果：拔除四个前磨牙病例矫治后,磨牙区牙弓宽度均减小,尖牙区牙弓宽度均增加;拥挤组及16岁以下组尖牙间牙弓宽度增加更明显,磨牙区牙弓宽度减小在各组间无明显差异。结论：拔牙矫正后拥挤组及16岁以下组的尖牙间牙弓宽度增加更明显,所以治疗后的保持需要时间更长。     

青年女性浅层嚼肌B超形态与牙弓形态关系的研究

目的了解肌肉形态、功能与牙弓形态之间的相互作用关系,探讨错牙合畸形的形成机理。方法本研究采用超声成像技术测量31例正常牙合青年女性浅层嚼肌横截面的周长、面积、横径、平均厚度、最大厚度及纵截面的长度,并将测量结果与牙弓测量指标进行统计相关分析。结果超声测量浅层嚼肌横截面的周长、面积、横径、平均厚度、最大厚度对下颌牙弓磨牙区宽度影响明显,且成负相关;横截面的周长、面积、横径与下颌牙弓前段长度关系显著,呈正相关,厚度与下颌牙弓前中段长度呈正相关,周长与下颌牙弓后段长度呈正相关;横截面的面积、周长与上颌牙弓长度成正相关;纵截面长度与上下颌尖牙角、下颌双尖牙角成负相关关系。结论浅层嚼肌形态与牙弓形态相关关系显著,浅层嚼肌形态越粗壮,功能越强,则越有利于面下1/3矢状向发展,而限制其宽度发育。     

青年女性浅层嚼肌B超形态与牙弓形态关系的研究

目的　了解肌肉形态、功能与牙弓形态之间相互作用关系 ,探讨错畸形形成机理。方法　本研究采用超声成像技术测量 31例正常青年女性浅层嚼肌横截面的周长、面积、横径、平均厚度、最大厚度及纵截面的长度 ,并将测量结果与牙弓测量指标进行统计相关分析。结果　超声测量浅层嚼肌横截面的周长、面积、横径、平均厚度、最大厚度对下颌牙弓磨牙区宽度影响明显 ,且成负相关 ;横截面的周长、面积、横径与下颌牙弓前段长度关系显著 ,呈正相关 ,厚度与下颌牙弓前中段长度呈正相关 ,周长与下颌牙弓后段长度呈正相关 ;横截面的面积、周长与上颌牙弓长度成止相关 ;纵截面长度与上下颌尖牙角、下颌双尖牙角的负相关关系。结论　浅层嚼肌形态与下颌牙弓形态相关关系显著 ,浅层嚼肌形态越粗壮 ,功能越强 ,下颌牙弓形态越窄长 ;浅层嚼肌形态对面中份深度有一定影响 ;此外 ,浅层嚼肌长度越长 ,上下颌尖牙角、下颌双尖牙角越小 ,牙弓形态越尖。     

Dental and alveolar arch widths in normal occlusion, class II division 1 and class II division 2

The aim of this study was to compare the transverse dimensions of the dental arches and alveolar arches in the canine, premolar, and molar regions of Class II division 1 and Class II division 2 malocclusion groups with normal occlusion subjects. This study was performed using measurements on dental casts of 150 normal occlusion (mean age: 21.6 +/- 2.6 years), 106 Class II division 1 (mean age: 17.2 +/- 2.4 years), and 108 Class II division 2 (mean age: 18.5 +/- 2.9 years) malocclusion subjects. Independent-samples t-test was applied for comparisons of the groups. These findings indicate that the maxillary interpremolar width, maxillary canine, premolar and molar alveolar widths, and mandibular premolar and molar alveolar widths were significantly narrower in subjects with Class II division 1 malocclusion than in the normal occlusion sample. The maxillary interpremolar width, canine and premolar alveolar widths, and all mandibular alveolar widths were significantly narrower in the Class II division 2 group than in the normal occlusion sample. The mandibular intercanine and interpremolar widths were narrower and the maxillary intermolar width measurement was larger in the Class II division 2 subjects when compared with the Class II division 1 subjects. Maxillary molar teeth in subjects with Class II division 1 malocclusions tend to incline to the buccal to compensate the insufficient alveolar base. For that reason, rapid maxillary expansion rather than slow expansion may be considered before or during the treatment of Class II division 1 patients.     

Dental arch widths and mandibular-maxillary base width in Class III malocclusions with low, average and high MP-SN angles

OBJECTIVE: To analyze the development of the dental arches and skeletal mandibular-maxillary bases in untreated Class III malocclusions with low averages and high mandibular plane angles in subjects aged 10 to 14. MATERIALS AND METHODS: The records of 50 untreated Japanese girls with Class III malocclusions at age 10 were selected from the files of patients pending orthodontic surgery. The patients included those with low (< or =27 degrees), average (27 degrees through 37 degrees) and high (>37 degrees) mandibular plane angles. The maxillary skeletal base width, biantegonial width, and maxillary and mandibular intermolar width were determined on posteroanterior cephalograms obtained at annual intervals when subjects were between 10 and 14 years of age. The difference between the maxillary and mandibular intermolar width was also calculated and reported. RESULTS: All skeletal and dental transverse widths in the high-angle group were significantly smaller than those in the low-angle group (P < .05) from ages 10 to 14. On the other hand, the maxillary to mandibular molar difference was the same for the three groups (P > .05) at each age. The deviations in molar differences did increase from age 10 to age 14 in all three groups. CONCLUSION: Mandibular plane angles might play a stronger role in the transverse skeletal growth of the maxilla and the mandible than the transverse dental growth of the maxilla and the mandible.     

Comparison of the headgear activator and Herbst appliance--effects and post-treatment changes

The aim of this study was to evaluate the effects of the headgear activator (HGA) and Herbst appliance during active treatment and retention and at follow-up in children with a skeletal Class II malocclusion. The two groups comprised 16 consecutive male patients (mean age 11.6 +/- 1.42 years) treated with a HGA and 16 male patients (mean age 12.6 +/- 1.13 years) treated with a Herbst appliance and Andresen activator (HAA) sampled from a larger pool using similar selection criteria. Growth data were obtained for the two groups. Lateral cephalograms taken at the start, after 6 months of treatment, after 12 months of active treatment or 6 months of retention, and at the 24-month follow-up were analysed. The total changes over the whole observation period (T0-T3) did not differ significantly between the groups; there was, however, a statistically significant increase in jaw prognathism (P < 0.05) and improvement of the molar relationship (P < 0.05) in the HAA group as compared with the HGA group. During the initial treatment phase (T0-T1), the overall treatment effects were statistically more pronounced in the HAA group than in the HGA group. Despite significant differences in treatment effects and changes between the two devices, there were no significant overall changes at follow-up except for the prognathism, i.e. maxillary prognathism decreased with treatment with the HGA while mandibulars prognathism continued to increase with HAA treatment.     

A comparison of arch widths in adults with normal occlusion and adults with class II, Division 1 malocclusion

This study compares arch widths and other cast and cephalometric measurements of 36 normal-occlusion subjects (19 males, 17 females) with 39 Class II, Division 1 subjects (20 males, 19 females). None of the subjects had received orthodontic treatment. Analysis of variance demonstrated that subjects with normal occlusion had larger maxillary molar widths, maxillary canine widths, and maxillary alveolar widths than subjects with malocclusion; only male subjects with normal occlusion had larger mandibular molar widths and mandibular alveolar widths than the malocclusion subjects; the normal occlusion and malocclusion groups had similar mandibular canine widths; and when the lower molar and alveolar widths were subtracted from corresponding upper widths, the remainders of the Class II group were negative instead of positive, contrary to the normal group. This revealed a posterior crossbite tendency in the Class II group.     

Comparison of dental arch measurements in the primary dentition between contemporary and historic samples.

The purpose of this study was to investigate secular changes that may have occurred in dental arch dimensions by comparing a sample of contemporary North American white children (born between 1992 and 1995) in the primary dentition to those children found in an earlier study of North American white children (born between 1946 and 1948). The sample of contemporary children has been followed prospectively since birth and was assessed at 4(1/2) to 5 years of age. Data for the historic sample were obtained from 5-year-old children who were enrolled in the Iowa Growth Study. The 2 samples were similar in terms of geographic location, racial and ethnic backgrounds, and socioeconomic status. To further enhance the comparison and to match the 2 groups, the 2 samples were restricted to white children with a normal overjet (<4 mm) and normal anteroposterior molar relationship, no anterior open bite, and no crossbite. In addition, individuals were excluded if any permanent teeth were erupted. Measurements of maxillary and mandibular arch lengths and intercanine and intermolar arch widths were made, with measurements of overjet and overbite. The results indicated that maxillary and mandibular arch lengths in both sexes were significantly shorter in the contemporary sample; all arch widths were significantly smaller in contemporary boys, but not in girls. These findings suggest that average arch dimensions may be smaller in contemporary children than in past generations. Further research is needed to determine whether smaller arch dimensions are associated with more crowding in the primary, mixed, and permanent dentitions.