附件对隐形矫治器内收上前牙影响的三维有限元分析

目的    通过拔除上颌第一前磨牙后前牙内收的隐形矫治三维有限元模型,分析切牙上设置附件对牙齿移动方式的影响。方法    基于1例成年患者颌骨的锥形束CT影像数据,按照切牙上有无附件,构建4组拔除第一前磨牙的上颌隐形矫治模型,分别为切牙无附件组、侧切牙单附件组、中切牙单附件组和双附件组;导入Ansys Workbench三维有限元软件,设置4个上切牙控根压入内收的隐形矫治过程,分析牙列初始位移和附件的应力分布。结果    切牙无附件组及中切牙单附件组均发生4个切牙的舌向倾斜移动,后牙产生不同程度的近中倾斜移动,尖牙近中倾斜伴有伸长;侧切牙单附件组及双附件组切牙呈整体内收压入移动趋势,切牙附件的龈方可观测到压应力集中。结论    隐形矫治内收上前牙时,在侧切牙放置附件有助于切牙整体内收的表达,而中切牙附件对牙移动方式的影响较小。     

无托槽隐形矫治器整体内收上颌前牙的三维有限元分析

目的:研究无托槽隐形矫治器整体内收上颌前牙过程中上颌前牙所受的应力情况及初始移动规律.方法:采用CBCT扫描已拔除双侧上颌第一前磨牙患者,建立上牙列、牙周膜及牙槽骨的初始复合体模型.激光扫描患者牙冠外形并与初始模型三维重叠建立终模型.应用ANSYS Workbench软件分析安装无托槽隐形矫治器时上颌前牙的应力分布及初始位移趋势.结果:建立了具有高仿真度的上颌复合体三维有限元模型;上颌双侧中切牙及侧切牙初始位移趋势一致,表现为远中舌向倾斜移动,且均有伸长趋势,其牙周膜应力分布与其位移趋势相一致;上颌双侧尖牙表现为远中倾斜移动趋势.结论:无托槽隐形矫治器在整体内收上颌前牙时,上颌前牙均表现为倾斜移动,且有伸长趋势.     

Changes in alveolar bone thickness due to retraction of anterior teeth.

In cases of bimaxillary protrusion, extraction of 4 premolars and orthodontic treatment with retraction of the anterior teeth is a widely used approach. However, there is controversy over whether the changes that occur in the anterior alveolar bone always follow the direction and quantity of tooth movement. Nineteen patients with dentoalveolar bimaxillary protrusion treated by extracting the 4 first premolars were evaluated with lateral cephalograms and computed tomography (CT). Cephalograms and CT scans were made before treatment and 3 months after retraction of the incisors. The measurements of the cephalograms showed that maxillary and mandibular incisors were retracted primarily by controlled tipping of the teeth. For all maxillary and mandibular incisors, we assessed the labial and the lingual alveolar plates at crest level (S1), midroot level (S2), and apical level (S3) for bone-thickness changes during retraction of the maxillary and mandibular anterior segments. In the mandibular arch, the labial bone maintained its original thickness, except the S1 measurements, which showed a significant decrease in bone thickness (P <.001). In the maxillary arch, the labial bone thickness remained unchanged. There were statistically significant decreases in lingual bone width in both arches after retracting the incisors. Some of the patients demonstrated bone dehiscence that was not visible macroscopically or cephalometrically. When tooth movement is limited, forcing the tooth against the cortical bone may cause adverse sequelae. This type of approach must be carefully monitored to avoid negative iatrogenic effects.     

微种植体支抗辅助内收上切牙后牙槽骨改建的锥形束CT研究

目的:探索运用微种植体支抗结合高位牵引钩大量内收上颌切牙后牙槽骨的改建情况。方法:以22例青少年上颌前突拔牙矫治患者,上颌切牙内收前、内收完成后的锥形束CT（cone-beam CT,CBCT）为研究样本,应用Mimics 15.0行CBCT影像三维重建,明确上颌切牙移动方式,利用Invivo5.0三维定点测量唇、腭侧牙槽骨厚度和高度变化。采用SPSS19.0 软件包对测量数据进行配对t 检验。结果:上颌切牙切缘与根尖均发生水平舌侧移动,但切缘的移动距离大于根尖;切缘点发生向下移动,根尖点出现明显的向上移动。上切牙腭侧牙槽骨厚度及唇腭侧总厚度在根颈1/3和根中1/3均显著减小（P<0.05）,而根尖1/3显著增加（P<0.05）,腭侧牙槽骨高度显著降低（P<0.05）。结论:青少年上颌前突患者微种植体支抗结合高位牵引钩可以实现受控制的倾斜移动。大量内收上颌切牙后,其腭侧牙槽骨吸收远大于唇侧增生,牙槽骨并没有完全跟随牙的移动而改建,提示正畸矫治时不宜过度内收前牙。     

Comparison of anterior and posterior mini-implant-assisted maxillary incisor intrusion: Root resorption and treatment efficiency

Objective:To compare, through cone-beam computed tomography (CBCT), the root resorption and treatment efficiency of two different mini-implant-assisted modalities in intruding the maxillary incisors.Materials and Methods:Thirty-two adults who had deep bite and elongated maxillary incisors were randomly allocated to two groups: anterior mini-implant group (AMG) and posterior mini-implant group (PMG). In the AMG, approximately 40 g of force was applied per side with elastic chains from mini-implants placed between the lateral incisors and canines and in the PMG, with beta-titanium wires from mini-implants placed between the second premolars and first molars. This study was conducted on CBCT scans taken before intrusion and after 4 months of intrusion. Data were analyzed by means of a paired t-test, independent t-test, and Pearson’s correlation test.Results:One patient was excluded from the AMG due to mini-implant loosening. While the incisors showed a significant reduction in length and volume, this amount was greater in the AMG, especially in the central incisors (P < .05). Together with the mean intrusion rates of 0.62 and 0.39 mm/mo in the AMG and PMG respectively, the center of resistance of the incisors showed distal movement with labial tipping; these changes were greater in the PMG (P < .001). Volumetric root resorption was correlated with the amount of intrusion (P < .05).Conclusions:Intrusion anchoring from posterior mini-implants is preferred in cases of upright incisors, as the use of such mechanics directs the roots into the spongiosa where they undergo less root resorption and more labial tipping.     

Combined use of miniscrews and continuous arch for intrusive root movement of incisors in Class II division 2 with gummy smile

Adequate intrusion and torque control of the retroclined maxillary incisors are critical for the treatment of Class II division 2 (div2) malocclusion. In addition, anterior retraction via lingual root movement can be challenging. This case report demonstrates a combined use of miniscrews and continuous arch with additional torque for intrusion, retraction, and torque control of maxillary incisors in the Class II div2 with gummy smile. A 20-year-old woman presented with multiple issues, including impacted canine, lip protrusion, prolonged retained mandibular primary molar, and two missing maxillary premolars. In order to improve her facial profile and eliminate the need for prosthetic work, the mandibular primary molar and contralateral premolar were extracted. Two miniscrews were placed at the maxillary buccal alveolar bone to apply the posterosuperior force for retraction of anterior teeth, with additional labial crown torque on the arch wire. The results were the intrusion (4 mm) and lingual root movement (17°) of the maxillary incisors without anchorage loss of maxillary molars, flattening of the Curve of Spee, and Class I molar relation that were maintained after 50 months of retention period. The combined use of miniscrews and continuous arch could be a reliable and effective treatment modality for torque control and intrusion of retroclined maxillary incisors in the Class II div2 patient.     

双钥匙曲整体内收上前牙的三维有限元研究

目的：探讨双钥匙曲整体内收上前牙的过程中不同的加力方式对上颌前牙生物力学效应的影响。方法：采用 CBCT采集患者上颌骨以及上牙列数据信息,利用 Mimics 软件进行三维重建,建立双钥匙曲整体内收上前牙的三维有限元模型;在ANSYS 软件中分别分析①末端回弯、②结扎丝加力以及③结扎丝加力联合双钥匙曲顶部连扎3种工况下上颌前牙的初始位移。结果：从工况1到工况3,矢状方向上：中切牙冠根位移差值由4．19E －03 mm 变为－8．85E －03 mm,表现为舌侧倾斜移动到整体移动后转变为唇侧倾斜移动。而侧切牙冠根位移差由7．99E －03 mm 减小到5．84E －04 mm,尖牙由9．47E －03 mm 变为8．54E －03 mm,显示侧切牙和尖牙由倾斜移动向整体移动转变;垂直方向上：切牙由伸长移动趋势变为压低,而尖牙的压低量也逐渐变大。结论：不同的加力方式上颌前牙的移动趋势不同,结扎丝加力和顶部连扎使前牙趋向于整体移动。     

滑动法关闭下颌拔牙间隙的力学行为有限元分析

目的模拟临床加载力系统,研究滑动法内收下前牙过程中,不同方向载荷作用下,牙及弓丝力学行为的变化。方法建立含有托槽、弓丝、前后牙牵引钩的下牙列及下颌骨有限元模型。连接前后牵引钩上的点来确定矫治力的方向。并通过改变牵引钩高度来改变矫治力的作用点和方向。分析计算每一组加载力对牙的三维瞬间移动趋势、牙周膜的单元应力、弓丝的节点最大位移。结果前后牵引钩高度的变化与各牙角位移及牙周膜应力间均有相关性(P<0.01),各牙在不同后牙牵引钩高度,均随着前牙牵引钩高度变化而产生不同的移动。①随着前牙牵引钩高度的增加,中切牙、侧切牙的移动趋势逐渐由近中舌侧倾斜变为近中唇侧倾斜;而尖牙则向远中舌侧倾斜;第二前磨牙由近中颊侧倾斜变为近中舌侧倾斜;第一磨牙则由近中舌侧倾斜变为远中舌侧倾斜,且近中根比远中根舌向倾斜角度要大。②全牙弓牙周膜的最大应力始终出现在侧切牙的唇侧根尖1/3处;而尖牙、第一磨牙的牙周膜最大应力分别集中在牙槽嵴顶、根分叉处。结论在临床治疗中,可通过改变牵引钩的高度来实现前后牙的不同移动趋势,在弓丝上弯制不同的序列以更好地控制支抗牙。     

微植体支抗滑动法内收上颌前牙的三维有限元研究

目的探讨不同微螺钉种植体植入高度以及不同牵引钩高度对微植体支抗滑动法内收上颌前牙的生物力学效应的影响。方法采用高精度螺旋CT扫描结合MIMICS快速三维重建的方法建立微植体－直丝弓上颌前牙内收力系的三维有限元模型,并在准确构建托槽、牙齿、弓丝、微种植体的力学关系基础上计算当微种植体植入高度为4、8 mm时以及牵引钩高度为1、4、7、10 mm时上颌前牙的初始移动情况。结果随着牵引钩高度的增加,上颌前牙内收时逐渐从冠舌向倾斜移动变为冠唇向移动;微种植体高位植入更有利于上颌前牙内收时的压入移动。结论通过微种植体植入高度和牵引钩高度的变化可以有效控制上颌前牙内收的牙齿移动方式。     

Efficiency of root torquing auxiliaries

In an experimental typodont study simulating the third stage of Tip-Edge treatment, the effect of five torquing auxiliaries on upper four incisors was assessed using the method of laser reflection. The auxiliaries analysed were: (1) Two-Spurs 0.016", (2) Four-Spurs 0.016", (3) Reciprocal Lateral Torque 0.016", (4) Torque Bar 0.022x0.018", 20 degrees, and (5) Torque Bar 0.022x0.018, 30 degrees. When comparing the wires, the efficiency (amount and speed of root tipping) varied considerably: (1) The Two-Spurs wire was the most efficient auxiliary of the five tested and showed good torque effect on the central incisors. (2) The Four-Spurs wire acting on all four incisors was less efficient than the Two-Spurs wire. (3) The Reciprocal Lateral Torque wire exhibited good palatal root torque on the central incisors and labial root torque on the lateral incisors. (4) The Torque Bars (20 degrees and 30 degrees ) were the least efficient wires of the auxiliaries tested and showed only small torque effects on the central and lateral incisor teeth. In clinical work using the Tip-Edge technique, the Two-Spurs torquing auxiliary should be the wire of choice for an efficient palatal root torque of the upper central incisors.     

A comparison of treatment results of adult deep-bite cases treated with lingual and labial fixed appliances

ObjectivesTo compare the cephalometric treatment results of adult deep-bite cases after labial and lingual fixed orthodontic treatment.Materials and MethodsA total of 102 patients underwent lingual orthodontic treatment and complete records were evaluated. The following inclusion criteria were used: patients who had Angle Class I or mild Class II malocclusion; comprehensive orthodontic treatment that did not include intrusion mechanics or any extractions; patients with an initial overbite of more than 3.7 mm. Thirteen patients met the inclusion criteria. These cases were matched with the same number of patients according to age with a labial orthodontic treatment group. Pre- and post-treatment cephalometric radiographs were evaluated. Independent t test or Fisher exact tests were performed to assess the differences between the groups.ResultsProclination of the upper incisors was higher in the labial group. Incisor mandibular plane angle (IMPA) showed an increase of 1.2° in the lingual group and 9.7° in the labial group. Lower incisor edge was approximately in a stable sagittal position in the lingual group but significant lower incisor proclination was seen in the labial group. The lower incisors were intruded (-1 mm) in the lingual group but lower incisors were minimally extruded (0.3 mm) in the labial group. No significant difference was found in the movements of upper and lower molars for both groups.ConclusionsThe nature of lower incisor movement involved less protrusion in lingual orthodontics than the labial treatment. Lingual orthodontic treatment is a better option in adult cases where intrusion of lower incisors without labial tipping is desired.     

Alveolar bone response to light-force tipping and bodily movement in maxillary incisor advancement: A prospective randomized clinical trial

Objective:To compare alveolar bone thickness and height changes between untreated incisors (control), incisors advanced with light-force tipping, and incisors advanced with bodily movement mechanics.Materials and Methods:Forty-three subjects (aged 9.49 ± 1.56 years) with anterior crossbite were allocated into an untreated group (control), tipping group, or bodily movement group. Lateral cephalograms were taken before advancement (T₀) and after obtaining normal overjet (T₁). Changes in labial and palatal alveolar bone thickness and height surrounding maxillary incisors were evaluated with limited field-of-view cone-beam computed tomography before advancement (CT₀) and 4 months after normal overjet was obtained (CT₁). Wilcoxon matched-pairs signed-rank and Kruskal-Wallis one-way ANOVA tests were used to compare changes within and between groups, as appropriate. The significance level was set at .05.Results:Labial alveolar bone thickness at the midroot and apical levels were significantly decreased in the bodily movement group (P < .05). However, between groups, there was no statistically significant difference in labial bone thickness changes at any level. Palatal and total alveolar bone thickness at the midroot and apical levels were significantly decreased in the tipping group compared with the control and bodily movement groups (P < .05). Neither labial nor palatal bone height changes were significantly different among groups.Conclusions:Maxillary incisor advancement with light-force tipping and bodily movement in growing patients resulted in labial alveolar bone thickness and labial and palatal alveolar bone height changes that were similar to the untreated group.     

骨皮质切开术辅助上切牙内收后对牙根及牙槽骨影响的锥形束CT研究

目的 探讨骨皮质切开术辅助上切牙内收后对上颌切牙牙根吸收、牙槽骨厚度和牙槽骨高度的影响.方法 招募20例拔除两个上颌第一前磨牙的骨性Ⅱ类1分类错牙合畸形患者,分为骨皮质切开术组(n=10)和对照组(n=10).矫治前后拍摄锥形束CT,测量两组矫治前后上颌切牙牙根长度、牙槽骨厚度和牙槽骨丧失高度.结果 骨皮质切开术组矫治...     

Extreme dentoalveolar compensation in the treatment of Class III malocclusion

The orthodontic treatment of an adult patient with a skeletal Class III malocclusion, increased anterior facial height, negative overjet, and bilateral posterior crossbite is presented. Treatment options included mandibular first premolar or third molar extractions with dentoalveolar compensation or combined surgical-orthodontic treatment. Mandibular third molar extraction with dentoalveolar compensation was the treatment choice. Biofunctional brackets, with accentuated lingual crown torque on the maxillary incisors and accentuated buccal crown torque on the mandibular incisors, were used. The anterior crossbite was corrected with intermaxillary elastics from the palatal aspect of the maxillary incisors to the labial aspect of the mandibular incisors. Class III elastics moved the maxillary teeth mesially and assisted in retruding the mandibular teeth. Patient compliance with the elastics was excellent, and satisfactory dentofacial esthetics were achieved. This treatment protocol has rigorous indications, and it is not a routine plan. The mechanotherapy and the pros and cons of this approach are discussed.     

Changes of anterior maxillary alveolar bone thickness following incisor proclination and extrusion

Objective:To investigate changes in maxillary alveolar bone thickness after maxillary incisor proclination and extrusion during anterior crossbite correction in a group of growing patients with Class III malocclusion.Materials and Methods:Maxillary incisors of 15 growing patients with anterior crossbite were proclined and extruded with 0.016″ beta-titanium advancing loops and Class III elastics. Lateral cephalograms were recorded before advancement (T₀) and 4 months after a normal overjet and overbite were achieved (T₁). Changes in alveolar bone thickness surrounding the maxillary incisors at the crestal (S1), midroot (S2), and apical (S3) levels were measured using cone-beam computed tomography (CBCT). Paired t-tests were used to determine the significance of the changes. A Spearman rank correlation analysis was performed to explore the relationship between thickness changes and the rate and amount of incisor movements.Results:Although statistically significant decreases were observed in palatal and total bone thickness at the S2 and S3 level (P < .05), the amounts of these changes were clinically insignificant, ranging from 0.34 to 0.59 mm. Changes in labial bone thickness at all levels were not significant. Changes in palatal bone thickness at S3 were negatively correlated with changes in incisor inclination. (r  =  −0.71; P < .05).Conclusion:In a group of growing patients with Class III malocclusion undergoing anterior crossbite correction, controlled tipping mechanics accompanied by extrusive force may produce successful tooth movement with minimal iatrogenic detriment to the alveolar bone.     

Incisor position and alveolar bone thickness:: A comparative analysis of two untreated samples using lateral cephalograms

ObjectivesTo evaluate incisor position and its relationship to alveolar bone in untreated optimal occlusions and in untreated Class II malocclusions.Materials and MethodsFifty-seven lateral cephalograms of individuals with naturally occurring optimal occlusions (mean age = 23 years) were used to assess positions of central incisors and their relationships to alveolar bone. Data were compared to a sample of 57 individuals with untreated Class II malocclusions with concurrent anterior-posterior (AP) skeletal discrepancies (mean age = 16.9 years).ResultsSignificant intergroup differences were found for AP jaw relationship, maxillary alveolar bone thickness, mandibular incisor inclination, maxillary incisor root distance to labial surface of alveolar bone, and mandibular incisor root apex distance to labial surface of alveolar bone. Small differences between females and males existed for several variables. In both samples, maxillary incisor roots were located closer to the labial surface of alveolar process than to the palatal surface by roughly a 2:1 ratio. Mandibular incisor root apices were generally equidistant from the labial and lingual surfaces of the alveolus in the optimal sample but closer to the lingual surface in the Class II sample.ConclusionsMaxillary incisors tend to occupy the anterior one-third of the alveolus in untreated individuals, regardless of AP interarch dental relationships or AP jaw relationships. Mandibular incisor root apices tend to be centered within the alveolus in untreated optimal occlusions but are more positively inclined, and their root apices are more posterior in untreated Class II malocclusions.     

Absolute anchorage with universal t-loop mechanics for severe deepbite and maxillary anterior protrusion and its 10-year stability

An adult patient with severe maxillary protrusion and deepbite who was congenitally missing two mandibular incisors was treated successfully by maximum retraction of the maxillary anterior teeth after extraction of the maxillary first premolars using a moment differential between the anterior and posterior segments created by a universal T-loop. Anterior teeth were moved with controlled tipping, and little anchorage loss of the posterior segments was experienced using the universal T-loop spring. Reduction of overbite was performed by absolute intrusion of both maxillary and mandibular anterior teeth. With retraction of the maxillary anterior teeth and recontouring of the mandibular canines, proper overjet and overbite were achieved. This report shows the 10-year stability of the case treated with the universal T-loop for the first time.     

Forces and moments delivered by the PET-G aligner to a maxillary central incisor for palatal tipping and intrusion

Objective:To evaluate the effect of material thickness and width of the gingival edge on the forces and moments delivered by aligners prepared from Duran foil (PET-G) to a maxillary incisor during tipping and intrusion.Materials and Methods:Aligners prepared from PET-G of three material thicknesses (0.5, 0.625, and 0.75 mm) and three widths of gingival edges (0–1, 3–4, and 6–7 mm) were investigated during incisor palatal tipping and intrusion of 0.5 mm each. Forces and moments were measured with a six-component measuring device. The influence of aligner thickness and aligner extend on the force and moment development were tested for statistical significance (P < .05).Results:The F_x and F_z forces produced during palatal tipping and intrusion by the 0.75-mm aligner material was significantly higher than those produced by the 0.5-mm-thick material (P = .005 and P = .047, respectively). There was no statistical difference between aligner thickness of 0.5 and 0.625 mm and between 0.625 and 0.75 mm. The same behavior was observed for the palatal moment (M_y). The F_x and F_z forces produced during palatal tipping and intrusion by the aligner with an extension of 0–1 mm edge was significantly lower than that of the aligner with a larger extension (3–4 mm edge: P = .003; 6–7 mm: P = .001). However, there was no statistical difference between aligners with a 3–4-mm and a 6-mm edge. The same behavior was observed for the palatal moment (M_y).Conclusions:The forces and moments exerted by the PET-G aligner on teeth vary, depending on the material thickness, width of the aligner edge, and direction of tooth movement.     

Comparison of anterior retraction and anchorage control between en masse retraction and two-step retraction: A randomized prospective clinical trial

Objectives:The purpose of this two-arm parallel trial was to compare en masse (ER) and two-step retraction (TSR) during space closure.Materials and Methods:Forty-eight adult patients with bimaxillary protrusion who were planned for treatment with extraction of four first premolars were enrolled. All patients were randomly allocated in a 1:1 ratio to either the ER (n = 24) group or the TSR (n = 24) group. The main outcome was the amount of posterior anchorage loss in the molars and the retraction of the incisors between ER and TSR; the difference in incisor and molar inclination was a secondary outcome. Lateral cephalometric radiographs and oblique cephalometric radiographs at 45° were taken before retraction (T1) and after space closure (T2). Cephalograms were digitized and superimposed on the anatomic best fit of the maxilla and mandible by one operator who was blinded to the treatment group.Results:Neither incisor nor molar crown movements showed any significant differences between the ER and TSR. There were no significant differences in the tipping of incisors and molars between the two groups.Conclusions:No significant differences existed in the amount of retraction of incisors and anchorage loss of molars between ER and TSR. Changes in incisor and molar tipping were similar, with the crowns showing more movement than the apex.     

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目的采用三维有限元法模拟不同方向牵引力内收上前牙,分析前牙位移趋势及应力分布,为临床治疗提供指导。方法研究于2012年在福建医科大学进行。建立唇侧直丝弓矫治器、6个上前牙及其牙周膜和前颌骨的三维有限元模型。模拟在0.48 mm×0.64 mm英寸主弓丝上,以种植钉为支抗、1.47 N矫治力整体内收上前牙,设定前牙区牵引钩为0-6 mm、后牙区种植钉高度分别为8和14 mm。加载后求解,计算出各前牙的位移及牙周膜第一主应力。结果滑动法整体内收上前牙时,牵引钩长度主要影响前牙的矢状向位移方式：牵引钩长度增加至6 mm的过程中,侧切牙在唇舌向上由舌向倾斜运动变为舌向整体平移和舌向控根运动外,中切牙和尖牙的三维位移只有数量的增大,趋势基本保持不变。支抗种植钉高度主要影响前牙垂直向位移：种植钉位置越高,侧切牙的压低位移增大,尖牙的伸长位移减小,即前牙整体压低的趋势更明显。结论种植支抗整体内收前牙时,单纯调整牵引钩长度和支抗种植钉高度难以实现前牙段的整体内收,有必要对前牙段增加适当的垂直向压低力量。