被动自锁托槽在固定正畸治疗中的应用

目的 通过比较被动自锁托槽与传统结扎托槽在非拔牙固定矫治的差异,来评估被动自锁托槽在固定正畸治疗中应用价值。方法 从已有病例中选取患者40例, 其中Damon Q自锁托槽组20例,传统托槽组20例。比较两组患者治疗过程中及治疗前后牙周相关指数的变化、治疗前后扩弓效果,以及两组患者每组平均矫治疗程、平均就诊次数、每次复诊医生椅旁操作平均用时间。结果 在粘接后6个月（T6）、粘接后12个月（T12）期,Damon Q自锁托槽组患者菌斑指数（PLI）、牙龈指数（GI）较传统托槽组患者明显低,差异具有统计学意义（P<0.05）。Damon Q自锁托槽组相比于传统托槽组有明显的扩弓效果,而对上颌第一磨牙的扩弓效果Damon Q自锁托槽组倾向于对牙齿的整体移动。Damon Q自锁托槽组平均矫治疗程、就诊次数、每次复诊医生椅旁操作平均所用时间明显小于传统托槽组。结论 被动自锁托槽在牙周健康、扩弓效果、减少患者平均矫治疗程及就诊次数、减少医生椅旁操作时间方面,较传统托槽都具有明显的优势。     

Evaluation of posttreatment stability after orthodontic treatment in the mixed and permanent dentitions

Objective:To investigate posttreatment changes in the maxillary and mandibular arches in patients who underwent orthodontic treatment during the mixed and permanent dentitions.Materials and Methods:The sample was collected retrospectively from three private practices and consisted of 42 patients who were at least 10 years out of orthodontic treatment. The longitudinal records of study casts and cephalometric radiographs were analyzed to quantify posttreatment changes.Results:Minimal changes in maxillary and mandibular irregularity occurred after an average of 16.98 years from completion of treatment. More than 10 years posttreatment, approximately 81% of the maxillary anterior teeth and 88% of the mandibular anterior teeth showed clinically acceptable incisor alignment (<3.5 mm). Mandibular fixed retainers greatly aided in maintaining the stability of the mandibular incisor alignment. However, posttreatment changes in maxillary incisor irregularity did not appear to be influenced by the presence of a mandibular fixed retainer. When compared with longitudinal changes observed in untreated subjects, the increase in incisor irregularity resembled a pattern similar to the regression line of untreated subjects and seems to be entirely age related. Arch width and arch depth was consistently decreased after treatment, but the magnitude of change was minimal at about 1 mm. No associations were found between any of the cephalometric measurements and changes in incisor irregularities.Conclusions:Orthodontic treatment stability can be achieved and mandibular fixed retention appears to be a valuable contributor, especially in patients with further growth expected.     

国产3B自锁托槽、3B直丝弓托槽和Damon Q自锁托槽椅旁操作时间的对比研究

目的比较国产3B自锁托槽、Damon Q自锁托槽以及国产3B直丝弓托槽的椅旁操作时间,为国产3B自锁托槽的临床应用提供参考依据。方法选择正畸患者80例,其中20人使用国产3B自锁托槽(3B自锁组),20人使用Damon Q自锁托槽(Damon Q自锁组),20人使用国产3B直丝弓托槽+结扎丝结扎(结扎丝组),20人使用国产3B直丝弓托槽+橡皮圈结扎(橡皮圈组)。待患者上下颌牙列基本排齐后,使用0.018*0.025英寸镍钛方丝入槽,记录全口结扎和拆除时间。采用单因素方差分析,比较4组患者的结扎和拆除时间。结果 3B自锁组的结扎、拆除和总时间均明显短于结扎丝组和橡皮圈组(P<0.01)。3B自锁组和Damon Q自锁组在结扎、拆除和总时间方面的差异均无统计学意义(P>0.05)。结论无论是采用结扎丝结扎还是橡皮圈结扎,国产3B自锁托槽的椅旁操作时间明显短于直丝弓托槽,且与进口的Damon Q自锁托槽相比无明显统计学差异。     

Self-Ligating Brackets in Orthodontics: A Systematic Review

Objective:To evaluate the clinical differences in relation to the use of self-ligating brackets in orthodontics.Materials and Methods:Electronic databases were searched; no restrictions relating to publication status or language of publication were applied. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) investigating the influence of bracket type on alignment efficiency, subjective pain experience, bond failure rate, arch dimensional changes, rate of orthodontic space closure, periodontal outcomes, and root resorption were selected. Both authors were involved in study selection, validity assessment, and data extraction. Disagreements were resolved by discussion.Results:Six RCTs and 11 CCTs were identified. Meta-analysis of the influence of bracket type on subjective pain experience failed to demonstrate a significant advantage for either type of appliance. Statistical analysis of other outcomes was unfeasible because of inadequate methodological design and heterogenous designs.Conclusions:At this stage there is insufficient high-quality evidence to support the use of self-ligating fixed orthodontic appliances over conventional appliance systems or vice versa.     

Mini-implants for en masse intrusion of maxillary anterior teeth in a severe Class II division 2 malocclusion

Abstract

This case report describes the treatment of a 16-year-old post pubertal male patient with a severe Class II division 2 malocclusion and 100% deep bite. In the first phase of treatment, a ‘Jones-Jig’ molar distalization appliance was used to distalize the maxillary molars by more than 6 mm, to achieve a Class I molar relation. In the second phase of treatment, mini-implants were inserted between the roots of the maxillary lateral incisor and canine to intrude all the maxillary anterior teeth en masse in a single step. Four millimetres of intrusion was achieved. The implants remained stable throughout treatment. In the mandibular arch the incisors were proclined to alleviate the severe crowding. Good overjet and overbite was achieved and has been maintained one year after completion of active orthodontic treatment.     

Canine retraction rate with self-ligating brackets vs conventional edgewise brackets

Objective:To compare the rates of retraction down an archwire of maxillary canine teeth when bracketed with a self-ligating bracket was used on one side and a conventional bracket on the other.Materials and Methods:In 43 patients requiring maxillary premolar extraction, a self-ligating bracket (Damon3, SmartClip) was used on the maxillary canine on one side and a conventional bracket (Victory Series) on the other. The teeth were retracted down a 0.018-inch stainless steel archwire, using a medium Sentalloy retraction spring (150 g). The rates of retraction were analyzed using a paired t-test.Results:The mean movement per 28 days for the conventional bracket was 1.17 mm. For the Damon bracket it was 0.9 mm and for the SmartClip bracket it was 1.10 mm. The differences between the conventional and self-ligating brackets were statistically significant: paired t-test, SmartClip, P < .0043; Damon3, P < .0001).Conclusion:The retraction rate is faster with the conventional bracket, probably because of the narrower bracket width of the self-ligating brackets.     

自锁矫治与传统矫治对牙根吸收的影响

目的:探讨自锁托槽轻力矫治是否可以减轻对牙根的吸收。方法:选取临床治疗的安氏Ⅰ、Ⅱ类拥挤并拔除4颗第一前磨牙病例30例,分为2组。其中,15例使用Damon 3MX自锁托槽矫治(自锁组),15例使用传统结扎式直丝托槽矫治(结扎组)。2组资料矫治前在性别、年龄、拥挤度及错类型等指标上具有可比性。通过矫治前、后的模型及全口曲面体层片,测量计算2组矫治后上、下切牙牙根吸收量,应用SPSS19.0软件包对数据进行t检验分析。结果:①上颌中切牙牙根吸收自锁组为(2.05±1.51)mm,结扎组为(2.08±1.21)mm,差异无显著性(P=0.973>0.05)。②上颌侧切牙牙根吸收自锁组为(1.77±1.01)mm,结扎组为(1.91±1.59)mm,差异无显著性(P=0.848>0.05)。③下颌中切牙牙根吸收自锁组为(2.06±1.62)mm,结扎组为(1.98±1.50)mm,差异无显著性(P=0.926>0.05)。④下颌侧切牙牙根吸收自锁组为(1.94±1.45)mm,结扎组为(1.84±1.17)mm,差异无显著性(P=0.888>0.05)。结论:在拔牙正畸中,自锁矫治并未表现出比传统结扎矫治更少的牙根吸收。     

Pattern of stress distribution in different bracket–adhesive–tooth systems due to debonding load application

PurposeOrthodontic bracket debonding during treatment period is an unbecoming occurrence for both orthodontists and patients. Various clinical and numerical studies have been done to specify different parameters which affect the bond strength of bracket–adhesive–tooth system. Pattern of stress distribution seems to be an appropriate factor to estimate bond strength of different systems. Since it is not possible to experimentally define stress distribution in bracket–adhesive–tooth systems, three dimensional finite element method is used. The purpose of this study is to obtain and compare stress distribution of five bracket–adhesive–tooth systems with various enamel surface morphologies as an indicator parameter of these systems’ bond strength.Materials and methodsIn order to specify and compare stress in five different teeth, including maxillary central incisor, mandibular central incisor, maxillary canine, and maxillary and mandibular premolar, 3D STL files of teeth and brackets were reconstructed in MIMICS10 and were imported to HYPERMESH for each tooth, separately. Space between enamel and bracket was filled with orthodontic adhesive, mechanical property of each layer was assigned and appropriate boundary conditions were applied.ResultsIt was observed that stress distribution in bracket, adhesive and tooth due to shear load application had irregular pattern. For all of systems stress concentration was observed either on the borders or incisal and gingival regions of enamel–adhesive bonding region and adhesive layer.ConclusionDespite the overall similarity in stress distribution pattern of different bracket–adhesive–tooth systems, some differences on pattern of stress distribution and magnitude of stress were also observed. This may bring about more susceptibility of curved enamel surface teeth to lower bond strength, damage and fracture than flat enamel surface teeth.     

A pilot clinical study of Class III surgical patients facilitated by improved accelerated osteogenic orthodontic treatments

Objective:To evaluate if the improved accelerated osteogenic orthodontics (IAOO) procedure could speed Class III surgical patients'' preoperative orthodontic treatment duration and, if yes, to what extent. This study was also designed to determine whether or not an IAOO procedure affects the tooth-moving pattern during extraction space closure.Materials and Methods:The samples in this study consisted of 24 Class III surgical patients. Twelve skeletal Class III surgery patients served as an experimental group (group 1) and the others as a control group (group 2). Before treatment, the maxillary first premolars were removed. For group 1, after the maxillary dental arch was aligned and leveled (T2), IAOO procedures were performed in the maxillary alveolar bone. Except for this IAOO procedure in group 1, all 24 patients experienced similar combined orthodontic and orthognathic treatment. Study casts of the maxillary dentitions were made before orthodontic treatment (T1) and after extraction space closure (T3). All of the casts were laser scanned, and the amount of movement of the maxillary central incisor, canine, and first molar, as well as arch widths, were digitally measured and analyzed by using the three-dimensional model superimposition method.Results:The time durations T3–T2 were significantly reduced in group 1 by 8.65 ± 2.67 months and for T3–T1 were reduced by 6.39 ± 2.00 months (P < .001). Meanwhile, the tooth movement rates were all higher in group 1 (P < .05). There were no significant differences in the amount of teeth movement in the sagittal, vertical, and transverse dimensions between the two groups (P > .05).Conclusion:The IAOO can reduce the surgical orthodontic treatment time for the skeletal Class III surgical patient by more than half a year on average. The IAOO procedures do not save anchorage.     

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.     

Permanent maxillary central incisor and first molar rotations in the mixed dentition in repaired complete unilateral cleft lip and palate and their relationship with absence of teeth in their vicinity

Objectives:To describe qualitatively and quantitatively the directions and magnitudes of rotations of permanent maxillary central incisors and first molars in the mixed dentition in repaired complete unilateral cleft lip and palate (UCLP) and study their associations with absence of teeth in their vicinity.Materials and Methods:Dental casts and orthodontic records taken prior to orthodontic preparation for alveolar bone grafting of 74 children with repaired UCLP (53 male, 21 female; aged 8.9 ± 1.0 years) were studied. Directions and magnitudes of permanent maxillary central incisor and first molar rotations were recorded. Tooth absence was confirmed from longitudinal radiographic records. Incisor and molar rotations were analyzed in relation to the absence of teeth in their vicinity.Results:Distolabial rotation of the permanent maxillary central incisor was noted in 77.14% on the cleft side, while distopalatal rotation was noted in 82.19% on the noncleft side. Incisor rotation was greater when a permanent tooth was present distal to the cleft side central incisor, in the greater segment. The permanent maxillary first molar showed mesiopalatal rotation, which was greater on the cleft side and when there was absence of one or more teeth in the buccal segment.Conclusions:Presence and absence of teeth were associated with the severity of incisor and molar rotations in UCLP. Crowding of anterior teeth in the greater segment was associated with a greater magnitude of rotation of the cleft side permanent central incisor. Absence of one or more buccal segment teeth was associated with greater magnitude of rotation of the molar.     

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.     

A Comparison of the Periodontal Health of Patients during Treatment with the Invisalign® System and with Fixed Orthodontic Appliances

Abstract Objective: Evaluation of the periodontal health in patients during treatment with either fixed orthodontic appliances or the Invisalign^® system. Study Design: The study was designed as a concomitant trial. The evaluation of the patients started in February 2002 and was completed in August 2003. Patients and Methods: Thirty consecutive patients each with fixed orthodontic appliances and with aligners were examined at three consecutive control visits for their periodontal condition. All individuals were part of the clientele of the Department of Orthodontics and Dentofacial Orthopedics of the Charité Berlin. The parameters evaluated were the modified Gingival Index, modified Plaque Index, modified Papillary Bleeding Index, and sulcus probing depth. The first three indices were recorded alternatively buccally and lingually in all permanent teeth from central incisor to first molar: buccally in the maxillary right and the mandibular left quadrants, lingually in the maxillary left and mandibular right quadrants. The sulcus depth was measured in four areas: mesially and distally, lingually and buccally in the 1st molar and the 1st premolar of each quadrant. Each control visit was concluded with a detailed, individualized oral hygiene instruction. Results: The modified Plaque Index was significantly lower in the Invisalign^® group overall. On the other hand, the periodontal condition of the two samples was nearly identical. Conclusion: Periodontal health is not jeopardized, even though the Invisalign^® system aligners cover all the teeth and the keratinized gingiva in part. This could be attributed to the fact that aligners are removable and thus allow unimpeded oral hygiene.     

上颌埋伏并与侧切牙易位的尖牙的正畸矫治

目的：探讨上颌埋伏并与侧切牙易位的尖牙的正畸矫治。方法：采用带钩的改良Nance弓联合直丝矫治技术治疗了2例替牙期上颌埋伏并和侧切牙易位尖牙病例,首先用改良Nance弓的末端钩在高位水平地牵引尖牙冠向颊侧及后方移动,同时用直丝弓技术使侧切牙排齐、根近中移动、牙体整体腭侧移动,使尖牙冠和侧切牙根在冠状向分开。然后采用“随形弓”,在维持两者在冠状向和垂直向的距离情况下,不断改变“随形弓”置于尖牙托槽上弓丝水平臂的第二序列弯曲,使两个交叉的易位牙体不断换位。结果：2例患者尖牙及侧切牙恢复正常的排列顺序,牙髓、牙周健康,治疗时间27个月。结论：矫治上颌埋伏并与侧切牙易位的尖牙关键是创造足够的空间,使两个易位牙的牙体换位时无干扰。改良Nance弓联合直丝矫治技术是一种有效的方法。     

自锁托槽非拔牙矫治下牙列拥挤的临床研究

目的 比较自锁托槽和传统结扎式托槽非拔牙矫治牙列拥挤患者的下牙列变化,探讨自锁托槽解除牙列拥挤的机制.方法 选择26例下牙列拥挤患者,分为自锁组和传统组,每组13例,分别使用自锁托槽(Damon3)和传统托槽(传统结扎式托槽)进行非拔牙矫治.对矫治前后变化进行配对t检验,逐步回归分析拥挤解除机制以及影响下切牙唇倾度改变量的相关因素.结果 矫治前后两组患者下颌尖牙间、前磨牙间牙弓宽度改变量及下切牙唇倾度改变量比较,差异均无统计学意义(P>0.1);矫治后自锁组下颌第一磨牙间牙弓宽度增加1.42 mm、下切牙凸距增加2.66 mm,传统组下颌第一磨牙间牙弓宽度增加0.65 mm、下切牙凸距增加1.57 mm,两组比较,差异有统计学意义(P<0.1).回归分析显示,自锁组对下切牙唇倾度变化量解释的总测定系数高达96.6%,被选入模型的变量为矫治前下颌拥挤度、下颌平面角、第一磨牙间牙弓宽度,以及矫治前后尖牙及第一前磨牙间牙弓宽度改变量.结论 非拔牙矫治下牙列拥挤时,自锁组和传统组患者均出现下切牙唇倾及下牙弓宽度增加,自锁组第一磨牙间牙弓宽度增加量及下切牙前移量较传统组多;自锁组下切牙唇倾度的改变不仅受拥挤度和矫治前牙弓宽度影响,而且受患者自身骨面型及牙弓宽度变化的影响.     

Damon3自锁托槽与普通金属托槽对牙齿垂直移动影响的实验研究

目的:探讨自锁托槽和普通直丝弓托槽使牙齿受压低力作用时牙周组织改建的差异.方法:以比格犬右侧侧切牙为研究对象,分别用Damon3自锁托槽与MBT金属托槽压低牙齿,观察加力7 d,14 d,28 d后两组犬牙周组织和牙槽骨改建情况.结果:对于被压低的牙齿,自锁托槽组骨吸收活跃,破骨细胞较多.结论:实验结果提示自锁托槽系统能够形成更加活跃的骨改建.     

The timing of significant arch dimensional changes with fixed orthodontic appliances: Data from a multicenter randomised controlled trial

Objectives

To identify the timing of significant arch dimensional increases during orthodontic alignment involving round and rectangular nickel-titanium (NiTi) wires and rectangular stainless steel (SS). A secondary aim was to compare the timing of changes occurring with conventional and self-ligating fixed appliance systems.

Methods

In this non-primary publication, additional data from a multicenter randomised trial initially involving 96 patients, aged 16 years and above, were analysed. The main pre-specified outcome measures were the magnitude and timing of maxillary intercanine, interpremolar, and intermolar dimensions. Each participant underwent alignment with a standard Damon (Ormco, Orange, CA) wire sequence for a minimum of 34 weeks. Blinding of clinicians and patients was not possible; however, outcome assessors and data analysts were kept blind to the appliance type during data analysis.

Results

Complete data were obtained from 71 subjects. Significant arch dimensional changes were observed relatively early in treatment. In particular, changes in maxillary inter-first and second premolar dimensions occurred after alignment with an 0.014 in. NiTi wire (P < 0.05). No statistical differences in transverse dimensions were found between rectangular NiTi and working SS wires for each transverse dimension (P > 0.05). Bracket type had no significant effect on the timing of the transverse dimensional changes.

Conclusions

Arch dimensional changes were found to occur relatively early in treatment, irrespective of the appliance type. Nickel-titanium wires may have a more profound effect on transverse dimensions than previously believed.

Clinical significance

On the basis of this research orthodontic expansion may occur relatively early in treatment. Nickel-titanium wires may have a more profound effect on transverse dimensions than previously believed.     

A prospective clinical trial of the effects produced by the Connecticut intrusion arch on the maxillary dental arch

ObjectiveTo assess and compare the effects produced in the maxillary dental arch by means of Connecticut intrusion arch (CIA) with or without a cinch back on the distal end of the tube of the first molars.Materials and MethodsThis study included 44 patients with a mean age of 13.1 ± 1.8 years treated for deep bite with a CIA randomly divided into two groups: group 1 (G1), 22 patients with initial mean age of 12.72 ± 1.74 years treated with the CIA in the upper arch without a cinch back on the distal surface of the tube of the first molars, and group 2 (G2), 22 patients with an initial mean age of 13.67 ± 2.03 years treated with the CIA with a cinch back. Lateral cephalograms were available before treatment (T1) and after intrusion of maxillary incisors (T2). The mean treatment period was 5.5 ± 1.45 months. Intragroup and intergroup changes in the maxillary incisor and molar positions were analyzed by paired and independent t-tests associated with the Holm-Bonferroni correction method for multiple comparisons (P < .05).ResultsThere were significant differences between groups in terms of maxillary incisor displacement. The maxillary incisors flared labially (2.17°) and proclined (1.68 mm) in group 1, whereas a palatal inclination (−1.99°) and retroclination (−1.13 mm) was observed in group 2. No significant differences were found for the molar positions between the groups.ConclusionsThe presence or absence of a distal bend in CIA affects incisor tipping and proclination during intrusion mechanics.     

Evaluation of maxillary buccal alveolar bone before and after orthodontic alignment without extractions: A cone beam computed tomographic study

Objectives:To assess the changes in the maxillary buccal alveolar bone during alignment without extractions. Secondarily, to evaluate the changes in arch dimensions and buccolingual inclinations of teeth and to identify risk factors for bone loss.Materials and Methods:Twenty-two adolescents with crowded permanent dentitions were treated without extractions with Damon 3MX brackets. Cone beam computed tomographic scans were taken before treatment (T0) and after alignment (T1). Bone thickness (BT) and height from the cementoenamel junction to the alveolar crest (BH) were evaluated at the maxillary central incisors, second premolars, and buccal roots of first molars. Changes in all variables from T0 to T1 were assessed. Correlations between bone changes and initial bone thickness, initial arch widths, initial crowding, amount of expansion, amount of tipping, and amount of molar rotation were calculated.Results:BT decreased and BH increased significantly for the incisors and mesiobuccal root of the first molars. Arch dimensions generally increased together with tipping. Bone loss was correlated with crowding and amount of expansion in the premolar region. Initially thinner BT was correlated with greater apical migration of bone for the incisors.Conclusions:Nonextraction alignment with self-ligating brackets led to arch expansion associated with tipping of teeth. Expansion related to alignment resulted in horizontal and vertical bone loss at the incisors and mesiobuccal root of the first molars. Thinner BTs and more severe crowding before treatment increased the risk for buccal bone loss.     

上下颌唇挡对替牙晚期儿童牙(牙合)的影响

目的研究上下颌唇挡同时应用对替牙晚期儿童牙(牙合)的影响.方法选择替牙晚期上下牙列轻度或中度拥挤患儿12例,上下颌均采用唇挡治疗8个月,进行治疗前后X线头影测量分析和模型测量分析,并对治疗前后的测量值变化进行配对t检验.结果唇挡治疗后,SNA、SNB分别增加1.02°和0.97°(P＜0.05),上下切牙前移均是牙冠向近中倾斜,而根尖相对固定的控制性倾斜,旋转中心接近根尖.上下磨牙远中倾斜效果不同,上磨牙远中倾斜直立,旋转中心接近牙冠;下磨牙远中倾斜移动,旋转中心接近阻抗中心;上颌磨牙间牙弓宽度、牙弓周径分别增加4.12mm和5.09mm(P＜0.01),下颌磨牙间牙弓宽度、牙弓周径分别增加4.07mm和6.86mm(P＜0.01).结论在儿童生长发育高峰期,唇挡可有效地引起上下颌牙弓横向和纵向变化,减轻或解除上下牙弓拥挤.