Permissible limit for mandibular expansion

In recent years, mandibular expansion has been increasingly performed in conjunction with orthodontic treatment. Lateral tipping of the molars associated with mandibular expansion should, however, be considered, because excessive expansion may result in excessive buccal tooth inclination, which may disturb the occlusal relationship. This study was conducted to quantitatively clarify molar movement during mandibular expansion using the Schwarz appliance to determine the permissible limit of mandibular expansion as a clinical index for inclination movement. Inclinations in the masticatory surface of the first molar and intermolar width were measured before expansion (T1), after expansion (T2), and before edgewise treatment (T3). Lower plaster models from 29 subjects treated with expansion plates were used and compared with models from 11 control subjects with normal occlusion.The average treatment change (T1-T2) in intermolar width was 5.42 mm (standard deviation 1.98), and the average angle of buccal tooth inclination was 10.16 degrees (standard deviation 3.83). No significant correlation was found between age prior to treatment and the treatment period when they were compared with the intermolar width increments and inclination angles. There was a significant positive correlation between retention duration and the amount of expansion. The regression coefficient of the angle of buccal tooth inclination during expansion to the increment of the intermolar width was approximately 0.2. This means that 1 mm of expansion is accompanied by 5 degrees of molar lateral tipping. This coefficient is clinically useful for estimating the permissible limit for mandibular expansion.     

两种颌托在颊侧多曲簧作用下对牙齿作用力的对比实验

目的 比较自凝树脂材料和热压膜材料制作的颌托,在颊侧多曲簧矫治力的作用下对上下颌中切牙的力值,以期选用合适材料代替自凝树脂制作颌托,为解决在临床应用颊侧多曲簧矫治器矫治安氏Ⅲ类错(牙合)畸形过程中,部分患者前牙出现的唇舌向倾斜问题提供参考.方法 口外模拟闭口位状态,将颊侧多曲弹簧依次矢状向打开2 mm、4 mm、6 m...     

Management of a hyperdivergent class III malocclusion, maxillary midline diastema, and infected mandibular incisors in a young adult

This is a case report of a 20-year-old woman with a hyperdivergent Class III malocclusion, infected mandibular incisors, maxillary midline diastema, and a mild tongue thrust. Extraction of the infected incisors and orthodontic treatment involving partial mesial movement of the remaining mandibular teeth produced a well-intercuspated Class III occlusion. After successful orthodontic treatment, a 4-unit bridge with pontics for the mandibular central incisors completed the rehabilitation and met the functional, esthetic, and occlusal treatment goals. Occlusal stability of the treatment result has been excellent in the 3-year follow-up.     

Orthodontic treatment of a traumatically intruded tooth with ankylosis by traction after surgical luxation.

This report presents the treatment of a patient with anterior crossbite and displacement of ankylosed maxillary and mandibular right lateral incisors. The maxillary lateral incisor, which was traumatically intruded, was successfully treated with 2 surgical luxations followed by orthodontic traction. The mandibular lateral incisor, which was avulsed and replanted, experienced replacement root resorption during orthodontic treatment and was ultimately extracted. Two years after active orthodontic treatment, the occlusal results were considered satisfactory.     

Anterior tooth morphology and its effect on torque

This study was undertaken to determine the variation in crown-root angle (CRA) of the upper incisors and canines as well as the variation in their labial contour. In addition, the influence of the variability of the labial contour and of different bracket heights on torque was evaluated. Proximal radiographs were taken of 160 extracted maxillary teeth (81 incisors and 79 canines). They were digitized and analysed with Jasc Paint Shop Pro 7TM and Mathcad 2001 Professional. The incisal edge, the centre of the cemento-enamel junction (CEJ), and the root apex were digitized to define the crown and root long axis. For all teeth the CRA was measured. At several heights of the labial surface a tangent was determined, enabling measurement of the inclination of the labial surface.The CRA had great variability, ranging from 167 to 195 degrees for the canines (mean value 183 degrees) and from 171 to 195 degrees for the incisors (average 184 degrees). The mean inclinations of the labial surfaces for the incisors varied greatly. Between 4 and 4.5 mm from the incisal edge the standard deviations (SD) were the smallest and between 2 and 4.5 mm from the incisal edge the labial surface angle differed by approximately 10 degrees. For the canines the mean inclinations of the buccal surface also varied. This angle differed by around 10 degrees between 2 and 4.5 mm from the incisal edge, but the SD were much larger than for the incisors.It can be concluded that placement of a bracket on a tooth at varying heights, still within a clinically acceptable range, results in important differences in the amount of root torque.     

Root Canal Morphology Evaluation of Central and Lateral Mandibular Incisors Using Cone-beam Computed Tomography in an Israeli Population

Introduction

Central and lateral mandibular incisors usually have 1 root canal. The purpose of this study was to investigate the prevalence of additional root canals in central and lateral mandibular incisors and to investigate the prevalence of oval and long oval canals in the cervical, middle, and apical thirds of cases with 1 root canal.

Apical root displacement is a critical risk factor for apical root resorption after orthodontic treatment

Objectives:To identify risk factors for apical root resorption (ARR) of maxillary and mandibular incisors using mathematical quantification of apical root displacement (ARD) and multiple linear mixed-effects modeling.Materials and Methods:Periapical radiographs of maxillary and mandibular incisors and lateral cephalograms of 135 adults were taken before and after orthodontic treatment. ARR was measured on the periapical radiographs, and movement of central incisors was evaluated on the superimposed pre- and posttreatment lateral cephalograms. ARD was mathematically calculated from pretreatment tooth length, inclination change, and movement of the incisal edge. Linear mixed-effects model analysis was performed to identify risk factors for ARR, and standardized coefficients (SCs) were calculated to investigate the relative contribution of the risk factors to ARR.Results:Vertical ARD showed the highest SCs for both maxillary and mandibular incisors. Horizontal ARD showed the second highest SC for mandibular incisors but was not significantly correlated with the ARR of maxillary incisors. When horizontal and vertical ARDs were included in the mixed-effects model, the use of self-ligating brackets was significantly correlated with increased ARR of mandibular incisors.Conclusions:ARD is a critical factor for ARR after orthodontic treatment. Careful monitoring of ARR is recommended for patients requiring significant ARD of incisors.     

正常(牙合)青年(牙合)平面与咀嚼运动轨迹的相关性分析

目的 分析个别正常(牙合)青年(牙合)平面与咀嚼运动轨迹特征的相关性,以期为临床定位(牙合)平面提供参考.方法 收集43名个别正常(牙合)青年志愿者,拍摄头颅侧位X线片,测量耠平面倾斜度(OP-CP);记录下颌中切牙切点的左右侧咀嚼运动轨迹,测量矢状面垂直向最大位移(V)、矢状面水平向前后最大位移之和(P+A)、冠状面水平向左右侧方位移之和(L+R)以及(牙合)平面与咀嚼运动轨迹的夹角,对(牙合)平面倾斜度(OP-CP)与V、(P+A)、(L+R)以及(牙合)平面与咀嚼运动轨迹的夹角进行Pearson线性相关分析.结果 OP-CP为(2.1±3.8)°.V为(20.22±4.28)mm,(P+A)为(11.42±2.45)mm,(L+R)为(8.62±1.52)mm.OP-CP与(L+R)呈负相关,相关系数r为-0.39(P<0.05).矢状面(牙合)平面与牙尖交错位及其附近的咀嚼运动开闭口轨迹近似垂直;OP-CP与咀嚼运动轨迹(牙合)期阶段2.0 mm、(牙合)外期上段的(牙合)平面-闭口轨迹角呈正相关(P<0.05);咀嚼轴角平均为(66.50±7.98)°,与OP-CP不相关(P>0.05).结论 矢状面(牙合)平面倾斜度与咀嚼运动轨迹有一定相关性.(牙合)平面对咀嚼运动(牙合)期闭合轨迹的影响较明显.     

Correlation between mandibular central incisor proclination and gingival recession during fixed appliance therapy

The purpose of this study was to determine whether proclination of mandibular central incisors during fixed appliance therapy results in gingival recession. Complete records of 67 patients (39 female and 28 male patients; mean age, 16.4 years; age range, 10-45 years) were used in this retrospective case-control study. Using pretreatment and posttreatment lateral cephalograms, the change in mandibular central incisor inclination was measured to divide the patients into an experimental group (proclination) and a control group (no proclination). Changes in clinical crown length were determined from pretreatment and posttreatment study models, and changes in gingival recession were determined from intraoral slides. Eight of the 67 patients exhibited a measurable increase in gingival recession of at least 0.5 mm, and 27 patients had an increase in clinical crown length of at least 0.5 mm. Statistical analyses showed no correlation between mandibular central incisor proclination and gingival recession or clinical crown length. A t-test analysis showed no statistically significant difference in gingival recession or change in clinical crown length between patients whose mandibular central incisors were proclined and those whose incisors were not proclined. Multiple regression analysis demonstrated that age, sex, race, treatment duration, extraction, treatment type, Angle classification, and proclination were not related to gingival recession or change in clinical crown length of mandibular central incisors. We conclude that the degree of proclination of mandibular central incisors during fixed appliance therapy was not correlated to gingival recession in this sample.     

Orthodontic space opening in patients with congenitally missing lateral incisors

OBJECTIVE: To determine the best time to begin orthodontic treatment for patients scheduled for implants to replace congenitally missing upper lateral incisors. The aim of timing is to maximize the amount of bone available for implant insertion and to improve incisors inclination. MATERIALS AND METHODS: Seventy-three plaster casts of 14 patients with 26 missing lateral incisors were cross sectioned in the center of the planned insertion of the implant, and the implant profile was projected into the area at three different times: T1--beginning of orthodontic treatment, T2-- end of orthodontic treatment, and T3--implant insertion. Deficiency of alveolar ridge volume needed for implantation was determined by Leica Quin analySIS software. RESULTS: An increase of ridge-volume deficiency from 0.26 mm(2) at T1 to 3.77 mm(2) at T3 was found. During orthodontic treatment the incisors protruded about 9.4 degrees (differing from the O1-NA standard of 7.5 degrees ). To ensure optimal esthetic and functional implantation results, time management concerning orthodontic treatment has to be done carefully. CONCLUSIONS: To avoid a high degree of alveolar bone atrophy and the risk of relapse and retreatment, orthodontic treatment involving tooth movement should not be initiated before the age of 13 years. Furthermore, it is important to maintain anchorage of the upper incisors because high incisor proclination causes extra-axial stress on the implant. An interdisciplinary approach is essential to provide the best treatment outcome.     

三种矫治器治疗安氏Ⅱ类2分类对切牙牙根吸收的影响

目的 比较不同矫治器治疗安氏Ⅱ类2分类错牙合畸形患者切牙牙根的吸收状况。方法 选择使用不同矫治器的安氏Ⅱ类2分类成年患者30例,其中传统MBT托槽、自锁托槽以及无托槽隐形矫治器的患者各10例,共计240颗切牙。收集患者治疗前后的锥形束CT(CBCT)影像学资料,并导入Dolphin Imaging软件,Mimics软件以及3-Matics软件测量分析治疗前后切牙牙根吸收情况。结果 传统MBT托槽组和自锁托槽组的上下颌中切牙以及侧切牙的牙齿长度(L)与无托槽隐形矫治器组上下颌中切牙及上颌侧切牙的牙齿长度治疗后较治疗前显著减小,差异具有统计学意义。使用无托槽隐形矫治器的患者下颌侧切牙治疗前后的牙齿长度无显著变化。而三组之间的对比,上下颌中切牙牙齿长度变化无显著统计学差异。无托槽隐形矫治器组上下颌侧切牙的牙齿长度减少量相对更低,差异具有统计学意义(P＜0.05)。此外,无托槽隐形矫治器组平均牙齿长度变化为(-0.37±0.11)mm,显著小于传统MBT托槽组(-1.32±0.47)mm及自锁托槽组(-1.05±0.38)mm。在牙根吸收区域的比较上,各组均表现为腭侧吸收多于唇侧吸收,近中吸收多于远中吸收。结论 无托槽隐形矫治器治疗安氏Ⅱ类2分类错牙合畸形可有效降低切牙牙根吸收严重程度。     

正常(牙合)青少年替牙期至恒牙初期切牙和磨牙转矩度的纵向观察

目的：研究正常胎青少年从替牙期到恒牙初期切牙和第一恒磨牙转矩度的生长变化，为正畸诊断、治疗方案设计提供依据。方法：对北京大学口腔医学院·口腔医院颅面生长发育中心收集的20名正常胎青少年样本（男性6名，女性14名）替牙期和恒牙初期的牙颌模型进行分析：替牙期：第一恒磨牙及4颗恒切牙萌出至胎平面，研究对象平均（9.5±0.9）岁；恒牙初期：除第三磨牙外其他恒牙均萌出至眙平面，研究对象平均（13．7±1．3）岁。使用BiagginiRayset系统测量切牙和第一恒磨牙的转矩度，分析替牙过程中牙冠倾斜度的变化。结果：替牙期与恒牙初期相比，男、女切牙和磨牙的转矩度差异均无统计学意义（P〉0．05）。替牙期至恒牙初期，上颌中切牙转矩度由14。减小为10.9°（P〈0．001）；下颌中切牙转矩度由1．8°增加为5.2°（P〈0.01）；上颌侧切牙转距度的变化无统计学意义（P〉0．05）；下颌侧切牙转矩度由1．2°增加为3．0°（P〈0．05）。上颌第一恒磨牙转矩度由-6．6°减小为-10．3°（P〈0．001）。下颌第一恒磨牙转矩度由一38．6°增加为-33.2°（P〈0，001）。结论：从替牙期到恒牙初期，上颌第一恒磨牙逐渐舌向直立，下颌第一恒磨牙逐渐颊向直立。     

Change in dentition over 20 years from third decade of life

PurposePrevious studies have documented long-term, age-related change in the teeth, dental arches and occlusion. However, very few studies have investigated longitudinal age-related change in the dentition using 3-dimensional (3-D) measurement. The purpose of this study was to clarify age-related change in the dentition using a laser scanner.Materials and methodsWe used dental casts obtained from the same subjects in their twenties and forties. Subjects were selected based on near-normal occlusion. We investigated age-related variation in the dentition using 3-D measurement.ResultsAge-related change in the dentition was characterized by a decrease in maxillary and mandibular width, an increase in maxillary length, and a decrease in mandibular length. Measurement of angulation revealed that the maxillary canines and molars were mesially inclined. We observed labial inclination of the maxillary incisors, and lingual inclination of the mandibular incisors, as well as the maxillary and mandibular canines and molars. Overjet, overbite, and the irregularity index all showed an increase, while occlusal vertical dimension showed a decrease. Multiple regression analysis indicated that lingual inclination of the lower central incisors was related to an increase in the irregularity index, and that lingual inclination of the upper canines and decrease in occlusal vertical dimension of the anterior teeth were related to increased overbite.ConclusionThe present findings showed that age-related changes in angulation and inclination of each tooth should be taken into account when providing occlusal rehabilitation or post-orthodontic retention.     

上颌阻生尖牙牵引治疗后邻近切牙牙根吸收情况的研究

目的 分析上颌阻生尖牙正畸牵引治疗后邻近切牙的牙根吸收情况及可能的相关因素。方法 选取上颌尖牙阻生且符合标准的43例患者,年龄10～23岁,共60颗上颌埋伏阻生尖牙。上颌阻生尖牙正畸牵引治疗前后分别拍摄锥形束CT,分析阻生尖牙邻近切牙的牙根吸收程度,并对可能存在的相关因素进行分析。结果 上颌阻生尖牙正畸牵引治疗后,上颌中切牙发生轻、中、重度牙根吸收的概率分别为71.7%、15.0%、13.3%,上颌侧切牙发生轻、中、重度牙根吸收的概率分别为48.3%、36.7%、15.0%,上颌中切牙与侧切牙牙根吸收严重程度存在差异(P<0.05)。位于腭侧及颌骨内、低位且靠近面中线的阻生尖牙,在正畸牵引治疗后,侧切牙牙根吸收程度较重(P<0.05)。低位阻生尖牙牵引治疗后,中切牙牙根吸收较重(P<0.05)。牵引时间较长时,中切牙牙根吸收程度较重(P<0.05)。治疗前已发生牙根吸收的切牙,在阻生尖牙牵引治疗后发生的牙根吸收程度较重(P<0.05)。结论 上颌侧切牙在阻生尖牙正畸牵引治疗后,发生的牙根吸收程度较重。上颌阻生尖牙正畸牵引治疗后,邻近切牙牙根吸收情况与阻生尖...     

牙科锥形束CT评价上颌前牙唇面形态对转矩的影响

目的研究上颌前牙的唇面形态及牙冠牙根成角关系对转矩的影响,为临床治疗中调整牙齿的转矩提供参考。方法选择206颗离体上颌前牙为研究对象,其中中切牙77颗、侧切牙68颗、尖牙61颗。利用牙科锥形束CT将全部牙齿进行扫描,在CT工具软件下进行影像的三维重建并提取全部牙的正中矢状切面图像,利用Auto CAD软件测量图像,分别测量牙冠唇面4个不同高度的切线与牙冠长轴所成的角度,以及牙冠长轴与牙根长轴所成的角度（冠根角）。结果当托槽高度为3.5～5.0 mm时,其高度每变化0.5 mm,上颌中切牙转矩变化约为1.5°,上颌侧切牙和尖牙的转矩变化约为2°。上颌中切牙、侧切牙、尖牙冠根角的均数分别为0.88°、3.87°、-3.30°。结论牙体形态的生物学变化从多方面影响矫治后牙齿的转矩角。     

福建地区安氏Ⅱ类1分类骨性错(牙合)患者切牙及磨牙高度和倾斜度研究

目的 研究福建地区未治疗的安氏Ⅱ类1分类错(牙合)患者上下颌第一磨牙、切牙的发育趋势及与测量平面的相关性分析,为临床诊断、治疗提供参考.方法 选取2013-2015年就诊我院的安氏Ⅱ类1分类骨性错(牙合)病例210例,按不同性别、发育阶段分为4组,测量上下颌第一恒磨牙、切牙牙槽高度和倾斜度及其他相关项目,分析比较各组间差异及相关性.结果 1.无论男女性成熟期组较生长发育高峰期组相比,下颌骨升支及体部长度、上第一磨牙倾斜度及高度、下第一磨牙高度、下切牙高度的差异具有统计学意义(P＜0.05).2.无论男女性,下颌平面角与上下颌第一磨牙倾斜度存在负相关性,与(牙合)平面角存在正相关性.此外,高峰期组中,下颌平面角与上下切牙倾斜度存在负相关性.而成熟期组中,与上下切牙高度存在正相关性.3.无论男女性组,高峰期组中,(牙合)平面角与上第一磨牙倾斜度及高度、下第一磨牙倾斜度、上切牙倾斜度存在负相关性.成熟期组中,(牙合)平面角与上切牙倾斜度存在负相关性,与上颌切牙高度存在正相关性.结论 1.上下磨牙、切牙倾斜度与牙槽高度存在随颌面发育成熟的变化趋势.2.下颌平面角与上下颌前后牙位置存在代偿规律.3.不同发育分期人群,(牙合)平面角与前后牙位置相关性特征不尽相同,临床诊治中应注意相关差异.     

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.     

Facial symmetry after distraction osteogenesis and orthodontic therapy.

The purpose of this study was to document changes in the facial symmetry of patients with severe hypoplastic mandibles treated with distraction osteogenesis and orthodontic therapy. Ten patients (5 males and 5 females), ages 7 to 22 years, underwent unilateral mandibular distraction osteogenesis with extraoral distracting devices. Orthodontic therapy was initiated after the completion of mandibular lengthening. The mean follow-up period was 25.5 months. Posteroanterior cephalograms were traced before distraction, 6 months after distraction, and at a later follow-up appointment. Displacement of the chin point (in millimeters) and the midpoint of the mandibular incisors, the piriform angle, the intergonial angle, the occlusal cant to the horizontal line (in degrees), the ratio of linear measurements (in millimeters) Co-Gn, Co-Go, and Go-Gn of the affected to the nonaffected side, CoA'-Mid to CoA-Mid, and GoA'-Mid to GoA-Mid were compared. At the latest follow-up appointment, patients defined as having a successful result had a mean occlusal cant of 1.25 degrees, an intergonial angle of 2.13 degrees, and a piriform angle of 2.63 degrees. The mean displacement of the chin point to the midline was 1.5 mm and that of the mandibular central incisors to the midvertical line was 1.38 mm. The results indicated improvement in all patients.     

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目的对上颌前牙区颌骨的骨量及唇侧骨皮质厚度进行测量分析,为正畸治疗植入微种植支抗钉的安全区提供参考依据。方法对2010年9月至2011年6月来大连市口腔医院就诊的25例成人患者行锥形束CT扫描及三维重建,测量距上颌牙槽嵴顶3、6、9、12mm4个水平上颌中切牙、侧切牙、尖牙根间区近远中向、唇腭向的距离以及唇侧骨皮质厚度。结果 (1)在距上颌牙槽嵴顶3、6、9mm水平中切牙根间近远中向距离均最宽,唇侧骨皮质均最薄;(2)在距牙槽嵴顶9mm水平中切牙与侧切牙根间近远中向距离最窄;(3)在4个测量水平侧切牙与尖牙根间唇侧骨皮质均最厚;(4)唇腭向在距牙槽嵴顶9mm及以上水平,中切牙根间骨厚度最薄,中切牙与侧切牙根间骨厚度最厚。25例中仅3例前牙区各牙根长度超过12mm,在距牙槽嵴顶12mm水平能测出根间近远中向距离,均较宽。结论通过对扫描后颌骨影像的分析,明确了前牙区颌骨的骨量及唇侧骨皮质厚度,为植入微种植支抗钉的安全区提供参考依据。