拔除第二双尖牙矫正病例(牙合)颌面的垂直向变化

目的　评价安氏 I类错畸形患者,特别是下颌平面角较大的患者拔除第二双尖牙矫正后颌面的垂直向变化,尤其是下颌平面的旋转变化。方法　24 例覆正常或较浅且下颌平面角大于均值的安氏 I类错患者(骨性与牙性均为 I类)拔除第二双尖牙,应用直丝弓技术完成矫治,25 例符合同样标准的患者由不拔牙矫正完成。对所有病例治疗前后的头颅侧位片进行描图和手工测量,比较拔牙组与非拔牙组颌面垂直向的变化。结果　对拔牙和非拔牙两组患者的头影测量结果进行的统计学比较发现,除下磨牙的伸长量拔牙组大于非拔牙组外,两组患者间颌面垂直向的变化并无统计学意义的差别。结论　第二双尖牙的拔除并不一定意味着下颌平面角的减小,对于高角前牙开倾向病例选择拔除第二双尖牙后,在矫正过程中仍需注意对后牙的垂直向控制。     

正畸拔除第一前磨牙后第三磨牙倾斜度的变化

目的 探讨正畸拔除第一前磨牙对第三磨牙倾斜度的影响。方法 选择37例拔牙和32例非拔牙患者,分别在治疗前和治疗后的曲面断层片上测量第三磨牙长轴与平面的交角以及第二、第三磨牙长轴的交角。用U检验来比较两组患者第三磨牙倾斜度在治疗前后的变化。结果 拔牙组和非拔牙组间治疗前后下颌第三磨牙长轴与平面和第二磨牙长轴交角的差异均具有统计学意义（P<0.05）;拔牙组和非拔牙组治疗前后上颌第三磨牙长轴与平面和第二磨牙交角的差异没有统计学意义（P>0.05）。在拔牙组,治疗后下颌第三磨牙比上颌第三磨牙更直立。结论 拔除前磨牙的正畸治疗能够改善第三磨牙的倾斜角度。     

Growth and treatment changes distal to the mandibular first molar: a lateral cephalometric study

This study examined space changes occurring distal to the mandibular first molar in growing patients treated using two different approaches. Two groups of 50 patients were selected for the study. The patients in group I were treated with the extraction of mandibular second premolars, whereas those in group II were treated without mandibular premolar extractions, by holding E-spaces with utility arches. Lateral cephalograms taken before and after treatment were used to measure space changes within the mandible. Follow-up written treatment records and radiographs were also examined to ascertain whether the mandibular third molars were ultimately extracted or retained. A greater mean space increase between Xi point and the mandibular first molar was found in boys and girls treated with second premolar extractions. The mean space increase between Xi point and the mandibular first molar, as well as the average increase in total mandibular length, was greater in boys than in girls for both treatment modalities. This reflects a greater amount of growth in boys during the treatment period. The greater mean space increase in the groups treated with second premolar extractions could be attributed to the fact that the first molar generally moved further mesially during treatment in the extraction subjects, whereas in the E-space subjects, the first molars were perhaps held back. It was noted that the mandibular third molars were ultimately more likely to have been extracted in the E-space groups than in the second premolar extraction groups within this sample.     

Influence of extraction and nonextraction orthodontic treatment in Japanese-Brazilians with class I and class II division 1 malocclusions.

BACKGROUND: The primary objective of this retrospective, longitudinal, cephalometric investigation was to study the influence of extraction and nonextraction orthodontic treatment on the facial height of Japanese-Brazilian children with Class I and Class II Division 1 malocclusions. METHODS: The sample included 59 mesocephalic patients distributed into 4 groups: group 1: Class I patients treated with 4 first premolar extractions; group 2: Class I patients treated nonextraction; group 3: Class II Division 1 patients treated with 4 first premolar extractions; group 4: Class II Division 1 patients treated nonextraction. The overall initial mean age of the groups was 12.14 years, and all groups were treated with standard edgewise appliances for a mean period of 2.49 years. The pretreatment and posttreatment stage comparison and the intergroup comparison of the treatment changes were conducted between extraction and nonextraction groups in the Class I and Class II malocclusion samples with t tests. RESULTS: The amounts of changes in the absolute magnitude of posterior and anterior facial heights and in the ratios of lower posterior facial height/lower anterior facial height and lower anterior facial height/total anterior facial height were similar between extraction and nonextraction treatment in both Class I and Class II malocclusions.     

A comparison of the effects of first premolar extractions on third molar angulation.

The effect of third molars on the stability of orthodontic treatment has been studied extensively. Yet the effect of orthodontic treatment, particularly premolar extractions, on third molars has not been substantially studied. The purpose of this investigation was to compare the changes in third molar angulation in patients treated with and without extractions. Records of 45 Class I, nonextraction and 33 Class I, first premolar extraction patients were examined. The pretreatment and posttreatment pantographs were digitized, and the angles between the third molar long axes and the occlusal plane were measured. Changes in third molar angulation from pretreatment to posttreatment for the two groups were compared for statistical differences using a Student's t-test. Statistical analysis revealed there were no significant differences in the change in third molar angulation in either group. On average, the maxillary and mandibular third molars showed an improvement in angulation relative to the occlusal plane. The results suggest that factors other than first premolar extractions may influence third molar angulation.     

Changes in soft tissue profile after orthodontic treatment with and without extractions.

The effects of orthodontic treatment on the facial profile, with or without the extraction of teeth, have greatly concerned orthodontists. A study was made of 80 patients with Angle Class I malocclusion. Forty patients (24 girls, 16 boys) did not undergo extraction of teeth, and 40 patients (23 girls, 17 boys) underwent extraction of maxillary and mandibular first premolars. Data were obtained from the corresponding lateral radiographs of the head taken before and after orthodontic treatment. The purpose of this study was to compare the response of the soft tissue of the facial profile in Class I malocclusions treated with and without the extraction of the 4 first premolars. The main soft tissue differences between the groups at the end of treatment were more retruded upper and lower lips in the extraction patients.     

Arch width changes in extraction and nonextraction treatment in class I patients

The aim of this retrospective study was to examine the dental arch width changes of extraction and nonextraction treatment in Class I patients. The study was performed on pretreatment and posttreatment dental casts of 60 patients (30 extraction and 30 nonextraction). The mean ages were 14.3 +/- 2.02 years for the extraction group and 14.1 +/- 2.9 years for the nonextraction group. The maxillary and mandibular crowding was -6.7 +/- 3.1 and -6.3 +/- 2.8 mm for the extraction group and -4.5 +/- 3.6 and -2.1 +/- 3.5 mm for the nonextraction group, respectively. The intercanine and intermolar arch width measurements were measured using a digital caliper. Paired samples t-test was used to evaluate the treatment changes within each group. To compare the changes between groups, independent samples t-test was performed. At the start of treatment, the maxillary and the mandibular intercanine and intermolar widths of both groups did not differ statistically. At the end of treatment, maxillary and mandibular intercanine widths of both groups increased significantly. The mandibular intermolar width decreased significantly for the extraction group and the maxillary intermolar width increased significantly for the nonextraction group. The decrease in maxillary intermolar width for the extraction group and the increase in mandibular intermolar width for the nonextraction group were not significantly different. No differences were observed between the groups in maxillary and mandibular intercanine widths. Maxillary and mandibular intermolar width indicated a significantly larger value in the nonextraction group than that in the extraction group.     

正畸拔除第一前磨牙对第三磨牙萌出角度的影响

目的：研究正畸拔除第一前磨牙对第三磨牙的影响。方法：37例第一前磨牙拔除和33例非拔牙患者作为研究对象,拍摄术前术后的全景片,测量第三磨牙长轴与平面及第三磨牙长轴与第二磨牙长轴的夹角,对治疗前后夹角的变化以U检验进行比较。结果：结果显示,拔除第一前磨牙后,下颌第三磨牙的的萌出角度得到了改善,而对上颌第三磨牙萌出改善并不明显。结论：拔除下颌第一前磨牙后,第三磨牙萌出角度会更加直立,从而可能减少其阻生的可能性。     

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目的评价骨性Ⅲ类错矜畸形患者正颌术前正畸治疗中拔除与不拔除上颌第一前磨牙对牙弓横向宽度的影响,为是否在术前正畸中拔除上颌前磨牙提供一个参考指标。方法选择2007年1月至2012年7月在大连市口腔医院接受正畸一正颌联合治疗的骨性Ⅲ类错铪畸形患者28例,其中12例术前正畸采取拔牙矫治（拔牙组）,16例采取不拔牙矫治（非拔牙组）。对两组病例正畸治疗前后的模型进行牙弓宽度对比研究。结果经过术前正畸治疗,拔牙组较非拔牙组的上颌后段牙弓宽度减小明显,差异有统计学意义（P〈0．05）;拔牙组与非拔牙组的下颌牙弓中段及后段宽度均有增加,但两组差异无统计学意义（P〉0．05）。结论在骨性Ⅲ类错猞畸形的正畸一正颌外科联合治疗中,拔除上颌第一前磨牙有利于术前正畸有效去除后牙代偿,协调上下牙弓间横向关系,为正颌手术创建良好条件。     

上颌拔牙矫治对骨性Ⅲ类错牙合畸形正颌术前牙弓宽度影响研究

目的 评价骨性Ⅲ类错牙合畸形患者正颌术前正畸治疗中拔除与不拔除上颌第一前磨牙对牙弓横向宽度的影响,为是否在术前正畸中拔除上颌前磨牙提供一个参考指标。方法 选择2007年1月至2012年7月在大连市口腔医院接受正畸-正颌联合治疗的骨性Ⅲ类错牙合畸形患者28例,其中12例术前正畸采取拔牙矫治（拔牙组）,16例采取不拔牙矫治（非拔牙组）。对两组病例正畸治疗前后的模型进行牙弓宽度对比研究。结果 经过术前正畸治疗,拔牙组较非拔牙组的上颌后段牙弓宽度减小明显,差异有统计学意义（P < 0.05）;拔牙组与非拔牙组的下颌牙弓中段及后段宽度均有增加,但两组差异无统计学意义（P > 0.05）。结论 在骨性Ⅲ类错牙合畸形的正畸-正颌外科联合治疗中,拔除上颌第一前磨牙有利于术前正畸有效去除后牙代偿,协调上下牙弓间横向关系,为正颌手术创建良好条件。     

Tip-Edge Plus直丝弓技术矫治Ⅱ类错(牙合)的临床应用初探

目的 通过观察Tip-Edge Plus直丝弓技术矫治的Ⅱ类错(牙合)患者颅面、牙(牙合)的特征性改变,探讨该技术的矫治要点.方法 应用Tip-Edge Plus直丝弓技术矫治12例(女性7例,男性5例,平均14.3岁)Ⅱ类错袷双颌或上颌前突患者.所有患者均拔除4颗第一前磨牙,按照Tip-Edge Plus 直丝弓技术矫治程序进行矫治,矫治前后行X线头影测量分析.结果 与矫治前相比,矫治后患者软组织侧貌改善明显,鼻唇角增大17.22°(P<0.01);上、下唇突距分别减少4.57 mm、3.72 mm(P<0.01);上、下切牙显著内收,突度分别减小4.73 mm、1.89mm(P<0.05).依靠口内支抗,矫治前后上颌支抗磨牙的移动仅为0.89 mm(P>0.05).结论 Tip-Edge Plus直丝弓技术利用口内支抗、细丝轻力,快速倾斜移动牙齿后简捷、准确转距并正轴的方法 ,可有效矫治Ⅱ类错(牙合)双颌或上颌前突患者.     

Cephalometric comparison of maxillary second molar extraction and nonextraction treatments in patients with Class II malocclusions

This retrospective cephalometric study compared the nature of the skeletodental correction of maxillary second-molar extraction and nonextraction treatments in correcting Class II malocclusions. The sample comprised 50 Class II, deep-bite, low-angle adolescents; half were treated with maxillary second-molar extraction and half were treated without extraction. Pretreatment and posttreatment lateral cephalograms were analyzed. Analysis relied primarily on the method of Lysle Johnston that evaluates sagittal changes in the teeth and supporting bones relative to the functional occlusal plane. All 18 cephalometric variables examined were statistically equivalent between the 2 groups at the start of treatment. In contrast, several skeletodental treatment changes differed significantly. The maxillary second-molar extraction group exhibited distal movement of the maxillary first molar (1.2 mm vs 0.0 mm), and there was greater flaring of the mandibular incisors in the nonextraction group (9.1 degrees vs 3.5 degrees ). The upper incisor root was torqued lingually in both groups, but there was more anterior crown movement in the nonextraction group (2.0 mm vs 0.0 mm). Also, the extraction group finished active treatment 7 months sooner on average. Sagittal molar correction in the maxillary second-molar group was a result of distalizing in the maxillary arch, whereas anchorage was expended in the mandibular arch to correct the malocclusion in the nonextraction group. In properly selected Class II malocclusions, maxillary second-molar extraction is a viable alternative treatment choice.     

Effects of extraction and nonextraction treatment on class I and class II subjects

This study aims to examine the profile as well as the dentoalveolar and skeletal effects of extraction or nonextraction treatment in a wide range of patients including Class I and Class II, division 1 cases. Results achieved with extraction and nonextraction modalities have also been compared. The study was performed on pretreatment and posttreatment lateral cephalograms of 87 orthodontic patients. There were no significant differences between the pretreatment values of extraction and nonextraction Class I groups, whereas SN-GoGn (degrees), maxillary incisor to A-Po (degrees), mandibular incisor to A-Po (mm), Co-Gn (mm), overjet (mm), and overbite (mm) measurements of extraction Class II group were significantly higher before the treatment. After treatment, these differences were eliminated in the Class II group; however, incisors were significantly protruded in both nonextraction groups. No other differences in profile or lip position were found between the extraction and nonextraction groups. The results of this study indicate that in successfully treated cases, whether by extraction or nonextraction, the same soft and hard tissue profile posttreatment end points were reached except for the incisor positioning, which is rather easier to anticipate than profile and soft tissue changes. The simple statement that extraction means a more retrusive or dished-in profile seems to be unacceptable. It seems that a more thorough assessment and investigation including pretreatment extent of crowding and factors related to anchorage, soft tissue thickness, and strain should be carried out.     

Geometric analysis of alveolar bone around the incisors after anterior retraction following premolar extraction

Objective:To evaluate changes in shape and alterations in thickness and vertical marginal bone levels of the alveolar bone around the maxillary and mandibular incisors before and after orthodontic treatment with premolar extraction using geometric morphometric analysis.Materials and Methods:Thirty-six patients with Class I bialveolar protrusion who underwent orthodontic treatment with premolar extraction were included. Cone-beam computed tomographic scans were obtained from the patients before and after treatment. Five fixed landmarks and 70 semilandmarks were used to represent the morphology of the alveolar bone around the maxillary and mandibular incisors. The coordinates of the landmarks of the alveolar bones were generated by Procrustes fit. The labial and lingual alveolar bone thicknesses around the maxillary and mandibular incisors and vertical marginal bone level were assessed quantitatively.Results:There was a significant difference in shape change of the alveolar bone before and after treatment. The deformation grid of the thin plate spline showed that the thickness and vertical marginal bone decreased on the lingual side after treatment. Shape changes were greater for the lingual alveolar bone on the mandibular incisor than for the maxillary incisors.Conclusions:Orthodontic treatment with premolar extraction might cause loss of alveolar bone around the maxillary and mandibular incisors. Careful consideration is needed to avoid iatrogenic degeneration of periodontal support around the incisors, particularly in the lingual area.     

The effects of first premolar extractions on third molar angulations

The purpose of this study was to determine the relationship between the inclinations of second and third molars during a two- to 2.5-year period in patients treated orthodontically both with and without premolar extractions. Records of 37 first premolar extraction patients and 33 nonextraction patients were examined. The pretreatment and posttreatment panoramic radiographs were analyzed. The angles were measured between the long axis of the third molar and the occlusal plane and between the long axis of the third molar and the long axis of the second molar. Changes in third molar angulations from pretreatment to posttreatment for two groups were compared by Mann-Whitney U-test. Statistical analysis revealed that mandibular third molars showed an improvement in angulation relative to the occlusal plane in the first premolar extraction group.     

Soft tissue changes after upper premolar extraction in Class II camouflage therapy

The long-term effect on the facial profile has led many orthodontists to attempt Class II division I camouflage treatment without extraction. Practitioners may cite "dishing in the face" as a reason not to extract. Previous investigations have evaluated the soft tissue response after maxillary incisor retraction, but few have evaluated the effect of maximum retraction in skeletal mandibular deficient Class II patients with essentially no crowding. Twenty-seven Class II division I Caucasian patients with a mean of 8.62 mm of overjet, little to no arch length deficiency, and maximum anchorage requirements were treated with extraction of only maxillary first premolars. Pre- and posttreatment lateral cephalograms were taken. Using several skeletal and soft tissue cephalometric measures, the treatment changes were assessed. The mean maxillary incisor retraction was 5.27 mm, the mean maxillary lip retraction was 2.03 mm, and the mean mandibular lip retraction was 1.23 mm. All the patients finished with good overall facial harmony and balance. The maxillary first premolar extraction for orthodontic camouflage may be a viable treatment option, especially if the patient has full upper lips and only a relative mandibular deficiency.     

The effects of extraction and nonextraction treatment on the mandibular position

Decisions on extraction of teeth as an aid in orthodontic treatment depend on dental and skeletal discrepancies concerning sagittal and vertical relationships. The purpose of this study was to assess the effects of extraction and nonextraction procedures on the posterior rotation of the mandible and the position of gnathion. Forty-eight nonextraction patients and seventy-three extraction patients treated in the orthodontic department were selected. The patients were from 11 to 15 years old, with a mean age of 12 years 2 months. The lateral cephalometric radiographs taken before and after treatment were traced and measured. Eleven variables reflecting the mandibular rotation were selected on the basis of factor analysis. Before treatment, total arch circumferential discrepancy and the 11 selected measurements showed significant differences between the extraction and nonextraction groups. In the extraction group, the lower anterior facial height was larger, ramus height was smaller, and the difference between vertical position of both maxillary and mandibular first molars and posterior facial height was greater than in the nonextraction group. Consequently, the mandible showed posterior rotation and was in retruded position in the extraction group. In the nonextraction group, the type of force application had no significant effect on the changes in skeletal and dental measurements. In the extraction group, however, the type of force application had a significant effect (p less than 0.05) on the changes in total anterior facial height, the horizontal distance of the maxillary first molar to a perpendicular line to the S-N plane passing through point S, the vertical distance of the maxillary molar to the S-N plane, the vertical distance of the maxillary and mandibular first molars to the S-N plane, the difference between the vertical position of the first molars and posterior facial height, and the difference between the vertical position of the first molar and vertical height of the ramus. In the group in which high-pull face-bow headgear was used, the extraction/nonextraction procedures had a significant effect (p less than 0.05) on the changes in angle ANB, total anterior facial height, anterior lower facial height, and the difference between anterior and posterior facial height.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of orthodontic treatment on mandibular rotation and displacement in Angle Class II division 1 malocclusions

The aim of this retrospective cephalometric study was to investigate the effects of orthodontic treatment on rotation and displacement of the mandible in Angle Class II, division 1 malocclusions. Thirty patients in the treated group (15 boys and 15 girls; mean age at pretreatment, 12.27 +/- 1.36 years) were compared with 28 subjects who had untreated Class II, division 1 malocclusions (15 boys and 13 girls; mean age at T1, 12.01 +/- 0.07 years). The patients in the first group were treated nonsurgically, without extraction, and without the use of functional appliances. Cephalometric data were obtained from three lateral cephalograms per case representing pretreatment (T1), posttreatment (T2), and at least 2-years postretention (T3). Thirty-seven variables were measured representing craniofacial morphology, tooth measurements, and mandibular displacement. Some variables were obtained from cranial base, maxillary, or mandibular superimposition. Statistical significance was established at P < .05, P < .01, and P < .001. The findings indicated that orthodontic treatment of Class II, division 1 malocclusions induced a more vertical mandibular growth direction associated with an increased vertical displacement of pogonion. Occlusal or vertical movement of maxillary and mandibular molars was not correlated to mandibular rotation or horizontal displacement of pogonion. When compared with controls, the treated group did not exhibit a significant difference in mandibular rotation or occlusal movement of maxillary molars; however, it did show a greater occlusal movement of mandibular molars during treatment.     

Long-term profile changes associated with successfully treated extraction and nonextraction Class II Division 1 malocclusions

This study was undertaken to compare the post-treatment and long-term soft tissue profiles of successfully managed and stable Class II, division 1 malocclusions treated with either 4 first premolar extractions or nonextraction therapy. It was hypothesized that, if sound extraction decisions were made according to accepted treatment objectives and successful treatment outcomes were achieved, there should be no differences between groups in soft tissue profiles post-treatment and long-term post-retention. The sample consisted of 63 Caucasian adolescents (23 extraction, 40 nonextraction). Correction of the malocclusion was achieved using a combination of cervical headgear concurrent with mandibular growth and maxillary incisor retraction. Pretreatment, post-treatment, and long-term post-retention lateral cephalometric radiographs were evaluated. The soft tissue facial profiles of the extraction and nonextraction samples were the same following active treatment and long-term post-retention. Progressive flattening of the facial profile was observed in both samples. This flattening was attributed to the maturational changes associated with continued mandibular growth and nasal development and was not influenced by whether or not teeth were removed. Long-term lip positions were more retrusive than the ideals suggested by Ricketts and Steiner, but close to the values reported for normal, untreated adults of similar ages. The pretreatment position and thickness of the lower lip as well as the initial maxillomandibular skeletal relationship may be predictors of post-treatment or long-term lower lip position.     

An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects

The purpose of this study was to examine dimensional changes in the maxillary arch following the extractions of maxillary first or second premolars. Pre- and posttreatment records of 71 patients treated by one experienced orthodontist were randomly selected from completed premolar extraction cases. Forty-five patients involved the extraction of maxillary first premolars; of these, 15 also had extractions of mandibular first premolars and 30 had extractions of mandibular second premolars. Twenty-six patients involved the extraction of maxillary second premolars, and all of these also had extractions of mandibular second premolars. Pretreatment factors that seemed to suggest a basis for the extraction choice in this sample included incisal overjet, molar relationship, and maxillary incisor protrusion. Mean reductions with treatment in the anteroposterior arch dimension were similar within all premolar extraction groups. There was evidence of greater mean maxillary intermolar-width reduction following the extractions of maxillary second premolars than following extractions of maxillary first premolars. Greater mean maxillary incisor retraction was found in the maxillary first premolar extraction group than in the maxillary second premolar group. A wide range of individual variation in incisor and molar changes did, however, accompany treatment involving both maxillary premolar extraction sequences.