Treatment of a patient with a Class II malocclusion, impacted canine, and severe malalignment

A case report of the orthodontic treatment of a male adolescent with a unilateral dental Class II malocclusion, an impacted canine, severe maxillary malalignment, and a canted maxillary anterior occlusal plane. Treatment consisted of full fixed appliances, extraction of the maxillary right first premolar, and surgical exposure of the impacted canine. Treatment vastly improved the patient's facial and dental esthetics. A Class I skeletal and dental relationship was established, along with a functional anterior guidance. The dental arches were coordinated and the dental midlines coincident with the midsagittal plane. This case report was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.     

减数下颌切牙在正畸-种植修复联合治疗中的设计和应用

目的评价正畸-种植修复联合治疗患者减数下颌单个切牙矫治的临床疗效,探讨其适合的病例选择标准及临床操作要点。方法从148例正畸-种植修复联合治疗病例中选出涉及减数下颌单个切牙矫治的21例患者,男9例,女12例,平均年龄32．1岁。所有患者均存在缺失数目不等的上颌前牙。21例患者均存在针对具体矫治目标而需要考虑的前牙牙量不调。其中7例接受了上下颌矫治,14例仅接受了下颌固定矫治器治疗。正畸治疗和种植修复完成后,对21例患者的前牙咬合关系和牙齿排列进行临床疗效评价。结果21例下切牙拔牙间隙完全关闭,相邻牙齿牙冠无倾斜,X线全口曲面断层片显示拔牙间隙关闭处两侧牙齿牙根平行。所有患者治疗后下前牙排列整齐,前牙覆[牙合]覆盖关系正常,后牙段维持了治疗前的排列和与[牙合]关系。下切牙间隙关闭处未出现和邻近牙位明显差异的“黑三角间隙”。正畸治疗后上前牙种植牙处覆盖平均2mm。种植医师对正畸治疗后的前牙[牙合]关系满意。结论对存在Bolton指数不调,上前牙牙量较小,下前牙中度拥挤或伴有下牙轻度前突的Ⅰ类或轻度Ⅲ类正畸-种植修复联合治疗患者,设计减数单个下切牙治疗,可以获得正畸和种植均满意的牙齿排列和前牙[牙合]关系。     

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。     

Biomechanical considerations for total distalization of the mandibular dentition in the treatment of Class III malocclusion

Class III malocclusions with mild to moderate skeletal discrepancies can be camouflaged by orthodontic tooth movement. Conventional methods using Class III elastics can correct Class III into Class I molar relationships. These mechanics show side-effects such as labioversion and intrusion of the maxillary incisors, extrusion of the maxillary molars, linguoversion and extrusion of the mandibular incisors, and intrusion of the mandibular molars along with flattening of the occlusal plane. Conventional mechanics can improve occlusal relationships and some profile esthetics but may produce detrimental smile esthetics by reducing the amount of maxillary incisor exposure. Recently, with the advent of temporary skeletal anchorage devices (TSADs), clinicians are able to achieve total distalization of the mandibular dentition and therefore improve the occlusal relationship without worsening smile esthetics. With the use of TSADs, the en masse movement of an entire dentition can be easily accomplished using a statically determinate force system, which makes treatment plans easier and treatment results more predictable. Finite element studies have identified the location of the center of resistance of the entire dentition and simulated displacement of the dentition depending on the force angulations (FAs) and have thus provided the theoretical basis for 3-dimensional tooth movement patterns. This article provides the biomechanical considerations and clinical applications of total distalization of the mandibular dentition depending on various FAs to the mandibular occlusal plane for camouflage treatment of various types of skeletal Class III 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.     

Ⅲ类错(牙合)下颌偏斜正畸疗效的初步分析

目的 探讨Ⅲ类错(牙合)牙性、功能性和轻度骨性下颌偏斜的正畸矫治效果,为临床治疗提供参考.方法 选择Ⅲ类错(牙合)牙性、功能性和轻度骨性下颌偏斜患者共35例,男性14例,女性21例,年龄7～22岁(平均16.5岁).牙性偏斜主要通过扩大上颌牙弓,促使下颌自动复位;功能性下颌偏斜应用双颌式功能矫正器或不对称性前方牵引和Ⅲ类颌间牵引进行治疗;轻度骨性下颌偏斜行拔牙正畸掩饰性治疗.结果 通过正畸临床矫治,22例Ⅲ类错(牙合)牙性和功能性下颌偏斜患者的颜面外形和咬合均达到满意的疗效.13例Ⅲ类错(牙合)骨性下颌偏斜患者,拔牙掩饰性正畸矫治仅可改善颜面美观.结论 Ⅲ类错(牙合)牙性和功能性下颌偏斜是正畸治疗的适应证;而对于Ⅲ类错(牙合)轻度骨性下颌偏斜的患者,单纯正畸治疗仅可减轻牙(牙合)畸形的程度.     

A morphometric study with setup models for bracket design.

This study was designed to obtain basic data on bracket design for the Asian patient. Setup models of 125 Japanese orthodontic patients seeking treatment were measured relative to the occlusal plane by the Andrews' method. A single experienced dental technician fabricated all setup models to provide one-tooth-to-two-teeth occlusal relationship, maximum intercuspation, ABC contacts, flat occlusal planes, canine guidance, and anterior guidance. Means and standard deviations of the crown angulations, inclinations, facial prominence, vertical contour, horizontal contour, and maxillary molar offsets were measured to reach the following conclusions: (1) No difference was observed in crown angulation between groups with one-tooth-to-two-teeth relationships. (2) Crown inclinations of the mandibular central and lateral incisors and canine were greater in the Class II setup group. (3) Maxillary molar offset averaged approximately 7 degrees in the Class II setup group. (4) The data from the Class I setup group showed minor differences from other researchers' data.     

A cephalometric study of the Class II correction effects of the Eureka Spring

The effect of the Eureka Spring (ES) appliance was investigated on 37 consecutively treated, noncompliant patients with bilateral Class II malocclusions. Lateral cephalographs were taken at the start of orthodontic treatment (T1), at insertion of the ES (T2), and at removal of the ES (T3). The average treatment interval between T2 and T3 was four months. The Class II correction occurred almost entirely by dentoalveolar movement and was almost equally distributed between the maxillary and mandibular dentitions. The rate of molar correction was 0.7 mm/mo. There was no change in anterior face height, mandibular plane angle, palatal plane angle, or gonial angle with treatment. There was a 2 degrees change in the occlusal plane resulting from intrusion of the maxillary molar and the mandibular incisor. Based on the results in this sample, the ES appliance was very effective in correcting Class II malocclusions in noncompliant patients without increasing the vertical dimension.     

拔除第一前磨牙对第三磨牙倾角的影响

目的研究正畸治疗中拔除第一前磨牙进行矫治和非拔牙矫治对第二磨牙和第三磨牙倾角的影响。方法选择56例上下颌第三磨牙均存在的青少年正畸患者,按拔牙与否分为拔牙组（30例,拔除4颗第一前磨牙）和非拔牙组（26例）,通过术前术后曲面断层片来测量患者上下颌第三磨牙长轴和平面的交角,第二磨牙与平面的交角以及第二、第三磨牙长轴的交角,并进行统计学分析。结果拔牙与非拔牙组矫治前后第三磨牙倾角均有不同程度的改善。与非拔牙组相比,拔牙组上下颌第三磨牙长轴与平面交角的变化量更大,2组间年平均变化量的差异有统计学意义（P<0.05）;2组矫治前后上下颌第二、第三磨牙长轴交角的变化无统计学差异,但其年平均变化量在2组间则有统计学差异（P<0.05）。2组间上颌第二磨牙与平面交角的年平均变化量无统计学差异（P>0.05）,而下颌第二磨牙与平面交角的年平均变化量则有统计学差异（P<0.05）。结论拔除第一前磨牙进行正畸治疗有利于第三磨牙倾角的改善,对第三磨牙萌出有积极意义。     

女性骨性Ⅱ类高角患者牙合平面与上下颌骨矢状向位置关系的相关性研究

目的 探讨女性骨性Ⅱ类高角患者牙合平面与上下颌骨矢状向位置关系之间的相互关系。方法 选取48例成人女性骨性Ⅱ类高角患者正畸治疗前头颅侧位片,各测量27项指标。应用Pearson相关分析上下颌骨矢状向位置关系与牙合平面指标、牙合平面指标与牙齿指标的相关性。结果 ANB角与后牙牙合平面倾斜度（OPP-FH）相关性显著。OPP-FH与上颌第二磨牙垂直高度及倾斜度相关性显著。结论 女性骨性Ⅱ类高角患者上下颌骨矢状向位置关系与后牙牙合平面倾斜度关系密切。     

Dentoalveolar compensation related to variations in sagittal jaw relationships

The purpose of this study was to investigate dentoalveolar compensation for variations in sagittal jaw relationships in 44 adult females with normal incisor relationships and either skeletal Class I or skeletal Class III jaw relationships. Cephalometric analysis was performed to evaluate sagittal jaw relationship, maxillary and mandibular incisor inclination, and the cant of the occlusal plane. Molar relationships were evaluated from study models. Correlation analysis was performed between skeletal and dental measurements. The most appropriate cephalometric parameters describing dental compensation quantitatively were SN-AB as a skeletal measurement and SN-U1, SN-L1, and SN-OP as dental measurements. Among the compensatory dentoalveolar changes, lower incisor inclination was strongly related to the sagittal jaw relationship and played an important role in obtaining a normal incisor relationship. Compensatory changes in the occlusal plane angulation were slight when compared with changes in the incisor regions. A Class I molar relationship was rare when SN-AB exceeded 84 degrees, even when incisor relationships were normal.     

平面与下颌矢状向位置关系的 X线头影测量研究

目的明确下颌处于不同矢状向位置时的牙形态,以及下颌矢状向位置与平面倾斜度的关系,为下颌矢状向位置异常患者的非手术正畸治疗提供策略依据。方法选取114例女性正畸患者治疗前的114张头影侧位片,根据ANB角的大小分为3组,每组各测量25项指标。对3组之间及两两组之间的差异进行方差分析和多重比较分析,对骨性指标与牙性指标的相关性进行直线相关分析。结果后牙平面（OP-P）倾斜度和上颌第二磨牙的垂直高度与下颌矢状向位置相关（P<0.05）。下颌后缩时,上颌第二磨牙垂直向萌出相对不足,OP-P倾斜度增加;下颌前伸时,上颌第二磨牙垂直向萌出相对过度,OP-P更平坦。当下颌处于不同位置时,牙轴近远中倾斜度有不同的代偿。下颌后缩患者上颌牙列牙轴远中倾斜,下颌牙列牙轴近中倾斜;下颌前突患者上颌牙列牙轴近中倾斜,下颌牙列牙轴远中倾斜。结论不同骨性环境下形态各有不同,正畸治疗下颌位置异常的患者时应重视后牙垂直高度的控制和对OP-P倾斜度的改变。     

Determination of the physiologic equilibrium point of the mandible by electronic means

The location of the physiologic equilibrium point of the mandible was determined by electronic means while the subjects clenched their teeth in centric relation with a force of 24 pounds. A total of 20 occlusal relationships were observed. In 14 Angle's Class I occlusal relationships, the equilibrium point, when projected at right angles to the midsagittal plane, was observed lined up within the mesial third of the mandibular first molar. In four Angle's Class II occlusal relationships, it was lined up within the distal half of the mandibular second premolar; and in two Class III Angle's occlusal relationships, it was lined up within the middle third of the mandibular first molar. When referenced to the maxillary arch, 16 occlusal relationships lined up within the mesial third of the first molar and four within the distal half of the second premolar. In the coronal plane, the equilibrium point was estimated as being in or close to the midsagittal plane. The biomechanical significance of the equilibrium point was discussed. The location of the equilibrium point was expressed mathematically using a model of the mandible as a beam on resilient supports. Further studies considering the clinical significance of the equilibrium point in relation to centric occlusion registrations and orthodontic treatment are suggested.     

Three-dimensional analysis of molar compensation in patients with facial asymmetry and mandibular prognathism

Objective:To evaluate the characteristic transverse dental compensations in patients with facial asymmetry and mandibular prognathism and to compare features of dental compensations between two types of mandibular asymmetry using 3-dimensional (3D) cone-beam computed tomography (CBCT).Materials and Methods:Seventy-eight adult patients with skeletal Class I (control group; n  =  33; 19 men and 14 women) or skeletal Class III with facial asymmetry (experimental group; n  =  45; 23 men and 22 women) were included. The experimental group was subdivided into two groups according to the type of mandibular asymmetry: translation type (T-type; n  =  20) and roll type (R-type; n  =  19). CBCT images were acquired before orthodontic treatment and 3D analyses were performed.Results:The transverse dental distance was significantly different between the two groups only at the palatal root apex of the maxillary first molar (P < .05). In the experimental group, the first molar axes were compensated significantly on both arches except the maxillary nondeviated side. The vertical molar heights were different between the two groups only on the maxillary arch (P < .001). The R-type showed greater mandibular ramal length difference and menton deviation than the T-type (P < .001). In the R-type, transverse compensation of the maxillary first molars was more obvious than with the T-type, which resulted in canting in the maxillary occlusal plane.Conclusions:Mandibular asymmetry with prognathism showed a characteristic transverse dental compensation pattern. The mandibular asymmetry type influenced the amount and direction of molar compensation on the maxillary arch.     

减小后牙▉平面倾斜度对安氏Ⅱ类高角畸形髁突位置影响的研究

目的: 研究在安氏Ⅱ类高角畸形正畸治疗中,减小后牙平面倾斜度对髁突位置的影响。方法: 15例安氏Ⅱ类高角畸形患者,年龄15~30岁。治疗前ANB>5°,下颌平面角FH-MP>32°,磨牙关系为双侧远中关系。常规排齐整平及适当扩弓后,利用多曲唇弓导下颌向前,并使后牙平面平坦化。利用锥形束CT（cone-beam CT,CBCT）测量治疗前、后颞下颌关节前、上、后间隙及后牙平面的改变情况。采用SPSS19软件包对变化量进行t检验;并利用相关性分析,进一步探讨髁突位置改变量与后牙平面倾斜度减小量之间的相关性。结果: 所有患者磨牙尖牙关系均调整到中性,侧貌改善明显,髁突后间隙平均增加(0.88±0.17)mm,变化有统计学意义(P<0.001);髁突上间隙平均增加(0.45±0.20)mm,变化也具有统计学意义(P<0.05)。后牙平面变平坦,POP-SN及POP-FH平均减小3.59°±2.31°及2.31°±3.62°,变化具有统计学意义(P<0.001)。髁突前间隙变化量无统计学意义,髁突位置改变量与后牙平面倾角的变化量之间无显著相关性。结论: 在安氏Ⅱ类高角畸形患者的正畸治疗中,通过正畸减小后牙平面倾斜度,可使髁突的位置发生适当的前下改变,有利于关节症状的改善。     

Treatment of dentoskeletal bimaxillary protrusion: additional extraction of maxillary second molars

This case report describes the orthodontic treatment of an 18-year-old female patient with Class II malocclusion with dentoskeletal bimaxillary protrusion. An acceptable treatment result was obtained with a four first premolar extraction and an additional maxillary two second molar extraction plan. Standard edgewise appliances were placed after the premolars were extracted. A positive soft tissue response to treatment was achieved, and the patient’s profile was improved, with a reduction of lip protrusion and mentalis strain. Dentally, the interincisal angle improved significantly as both the maxillary and mandibular incisors were uprighted after space closure. The occlusion remained stable during 2 years of follow-up.     

Interdisciplinary treatment of an adult patient with old extraction sites

This case report describes the interdisciplinary treatment of a 31-year-old female patient showing a protrusive profile, maxillary constriction, mandibular crowding, a Class III canine relationship complicated with multiple missing teeth, old atrophic extraction sites, and periodontal defects. The lower dental arch irregularity was eliminated by air-rotor stripping (ARS). The upper extraction site was opened for prosthetic rehabilitation, whereas closure of the lower extraction space was preferred. The narrow alveolar crest of the atrophic bone was augmented with the use of autogenous bone, beta-tricalcium phosphate (Cerasorb), and autogenous platelet-rich plasma. A functional and esthetic occlusion in an improved facial profile was established at the end of orthodontic treatment combined with ARS technique, surgery, and prosthodontics.     

Asymmetric severe skeletal Class II division 1 patient with temporomandibular joint disorder treated with zygomatic anchorage devices and Ni-Ti alloy wires

Objective:To describe the orthodontic treatment of a nongrowing 30-year-old woman with asymmetric severe skeletal Class II malocclusions (asymmetric Angle Class II), large overjet (16 mm), large overbite (8 mm), two congenitally missing mandibular incisors (presenting a deciduous anterior tooth), and signs and symptoms of temporomandibular joint disorder (TMD).Materials and Methods:We used novel improved super-elastic Ni-Ti alloy wires (ISWs) combined with Ni-Ti alloy coil springs, power hooks, and a zygomatic implant as reinforced anchorage to provide a constant and continuous mild force to the dentition.Results:We successfully distalized maxillary molars, premolars, and retracted anterior teeth and corrected the asymmetric Angle Class II molar relationship using this system of zygomatic anchorage in conjunction with ISWs, Ni-Ti alloy open-coil springs, and crimpable power hook. The maxillary molars were distalized, and postero-occlusal relationships were improved to achieve Class I canine and molar relationships on both sides. Intrusion of the upper molars made the mandibular plane close. Ideal overbite and overjet relationships were established. Facial esthetics were improved with decreased upper and lower lip protrusion, and no symptoms of TMD were observed after treatment.Conclusion:The orthodontic treatment described here is a promising anchorage technique alternative to traditional techniques to improve severe skeletal Class II with TMD.     

Dentoskeletal treatment changes in Class II subdivision malocclusions in submentovertex and posteroanterior radiographs.

The objective of this study was to evaluate the dentoskeletal changes consequent to orthodontic treatment in subjects with Class II subdivision malocclusions, treated with asymmetric extractions, compared with a normal-occlusion control group. The sample consisted of 3 groups, with 30 subjects in each: normal-occlusion subjects (group 1), untreated Class II subdivision subjects (group 2), and Class II subdivision patients treated with asymmetric extractions (group 3). All subjects had a full complement of permanent teeth at the beginning of treatment. The average ages of the subjects were 22.42, 15.76, and 18.57 years, respectively, in groups 1, 2, and 3. Measurements of relative differences in the spatial position of dental and skeletal bilateral landmarks were obtained from the submentovertex and posteroanterior cephalometric (PA) radiographs. The t test for independent samples was used to compare group 1 with groups 2 and 3 at different times. Results from the submentovertex radiograph showed that asymmetric extractions in Class II subdivision malocclusions will maintain the differences in the anteroposterior positions of right and left, maxillary and mandibular first molars, as would be expected with the treatment protocols used. There were no significant skeletal changes that could be attributed to the treatment approaches investigated or transverse collateral effects with the asymmetric mechanics used. It was also demonstrated that treatment of Class II subdivision malocclusions with asymmetric extractions produced corrections of maxillary and mandibular dental midline deviations with the midsagittal plane, without canting the occlusal plane or any other investigated horizontal plane, as seen in the PA radiograph. Treatment of Class II subdivision malocclusions with asymmetric extractions constitutes a beneficial approach to this problem.     

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.