Ectopic eruption of the maxillary first permanent molar: etiologic factors

For clinical handling, it is important to determine whether any etiologic factors, alone or in combination, are of more importance than others in causing ectopic eruption of a maxillary first permanent molar. Etiologic factors involved in ectopic eruption of maxillary first permanent molars were investigated in 129 children with a mean age of 8.6 years. Ninety-two children (fifty-eight boys and thirty-four girls) had ectopic eruption and thirty-seven children served as controls and were matched by age and sex. Two types of ectopic eruption could be distinguished: a reversible type in which the permanent molar frees itself and an irreversible type in which the permanent molar remains in a locked position. Measurements were made on lateral head films, orthopantomograms, and dental casts. For 104 subjects all variables could be measured. Data was analyzed by discriminant analysis. Children with irreversible ectopic eruption had significantly larger permanent molars and a more pronounced mesial angle of eruption. A tendency toward a shorter maxilla was also found. No significant difference was found between sides with reversible ectopic eruption and sides with normal eruption. From the discriminant analysis between groups and all variables investigated, 90.7 percent of the cases could be correctly classified into groups. This study indicates that sufficient space may be gained for the premolars if the mesial tipping of the first molar is corrected, despite the tendency toward a shorter maxilla and larger than normal permanent molars.     

上颌第一恒磨牙异位萌出的片段弓治疗

目的:探讨片段弓治疗上颌第一恒磨牙异位萌出的临床应用效果.方法:纳入15例年龄7～9岁的患者,上颌第一恒磨牙异位萌出,单侧近中阻生,应用片段弓矫治技术,镍钛推簧推第一恒磨牙向远中.结果:15例患者治疗结束后,异位的上颌第一恒磨牙正常萌出.结论:片段弓矫治技术远中移动异位萌出的上颌第一恒磨牙疗效显著.     

变异式保持器治疗第一恒磨牙异位萌出的临床应用

目的探讨变异式保持器治疗第一恒磨牙异位萌出的临床应用效果。方法选择临床25例上颌第一恒磨牙异位萌出的患儿,年龄7~9岁,其中10例双侧,15例单侧,通过传统的Nance弓焊接远端牵引钩,在异位萌出的第一恒磨牙牙合面,联合应用链状橡皮圈推第一恒磨牙向远中以达到其正常的生理位置。结果 25例接受治疗的患儿均完成了治疗,且疗效明显,异位的第一恒磨牙均萌出到了正常位置。结论变异式保持器用于治疗第一恒磨牙异位萌出疗效显著,操作简便,适合在临床推广。     

Association between ectopic eruption of maxillary canines and first molars

The purpose of this study was to elucidate a possible association between ectopic first molar eruption causing root resorption on the distal root of the primary maxillary second molar, and ectopic canine eruption causing root resorption on the permanent maxillary incisors.The subjects consisted of 30 patients, 22 females and eight males in the age range 8.3-15.0 years in whom root resorption of the permanent maxillary lateral and/or central incisor caused by the erupting permanent canine was diagnosed, and clinical and/or radiographic information concerning maxillary first molar eruption existed.It was found that of the 30 patients, seven (23.3 per cent) also had pathological root resorption of the second primary molar caused by ectopic molar eruption.It is suggested that patients with ectopic maxillary first molar eruption leading to pathological root resorption of the maxillary second primary molar are followed closely during the period of premolar and canine eruption, as the ectopic first molar could be an early warning of an increased risk of ectopic canine eruption leading to root resorption of the maxillary permanent incisors.     

Dentofacial changes after orthodontic intervention with eruption guidance appliance in the early mixed dentition

OBJECTIVE: To evaluate skeletal and dentoalveolar changes induced by the eruption guidance appliance in the early mixed dentition. MATERIALS AND METHODS: Pre- and posttreatment cephalometric radiographs of 115 consecutively treated children, 62 boys and 53 girls, were compared with those obtained from a control group of 104 children, 52 boys and 52 girls. Pretreatment radiographs were taken at the deciduous-mixed dentition interphase (T1) and after full eruption of all permanent incisors and first molars (T2). The mean age of the children in both groups was 5.1 years at T1 and 8.4 years at T2. RESULTS: A significant difference between the groups at T2 was found in the mandibular length, midfacial length, and maxillomandibular differential. The increase in mandibular length was 11.1 mm in the treatment group and 7.2 mm in the control group. No differences were found in measurements of maxillary position or size. There was a significant shift toward a Class I relationship in the treatment group. Labial tipping and linear protrusion of the mandibular incisors was evident in the treatment group at T2. There was no effect on the inclination or position of the maxillary incisors. CONCLUSIONS: Occlusal correction was achieved mainly through changes in the dentoalveolar region of the mandible. In addition, the appliance enhanced condylar growth resulting in a clinically significant increase in mandibular length. No effect was observed on maxillary position, maxillary size, inclination or protrusion of the maxillary incisors, or facial height.     

上颌第一磨牙倾斜度自然代偿的最主要影响因素研究

目的 探寻未经治疗状态下错(牙合)患者上颌第一磨牙倾斜度(UM/PP)自然代偿的最主要因素.方法 共纳入1403例患者,涉及36个变量,以UM/PP为因变量进行多元回归分析,建立相应的变量影响权重解释模型.结果 治疗前上颌第一磨牙近远中倾斜度的回归模型纳入16个有意义的变量,包括年龄、是否双颌前突、安氏分类、垂直骨型、...     

改良舌弓治疗下颌第一磨牙异位萌出的临床应用

目的探讨改良舌弓治疗下颌第一恒磨牙异位萌出的临床效果。 方法选择于2018年1月至2021年6月于东莞健力口腔医院正畸科就诊的15例下颌第一恒磨牙异位萌出的患儿，年龄7 ~ 8岁，其中5例双侧、10例单侧，以第二乳磨牙作为直接支抗，通过传统的下颌舌弓焊接远端牵引钩，在异位萌出的恒磨牙面粘接舌侧扣联合链状橡皮圈牵引异位萌出恒磨牙向远中，以达到其正常的生理位置。使用SPSS 20.0统计软件分别对治疗前后作为直接支抗牙的第二乳磨牙与异位的第一恒磨牙的倾斜角度与冠近远中高度进行统计学分析，采用配对t检验进行对比，以P<0.05为差异有统计学意义。 结果第二乳磨牙治疗前的倾斜角度为64°±3°，治疗后为63° ± 4°，差异无统计学意义（t = 1.399，P = 0.178）。同样，第二乳磨牙治疗前的近远中冠高比（85% ± 4%）与治疗后（84% ± 4%）相比，差异无统计学意义（t = 0.608，P = 0.550）。异位的下颌第一恒磨牙治疗前的倾斜角度为52° ± 6°，治疗后为69° ± 4°，差异有统计学意义（t = -10.423，P<0.001）。异位的下颌第一恒磨牙治疗后的近远中冠高比（90% ± 3%）高于治疗前（80% ± 5%），差异有统计学意义（t = -8.231，P<0.001）。 结论改良舌弓临床操作简便，提供的支抗良好、充分，能有效治疗下颌第一恒磨牙异位萌出。     

Ectopic eruption of the maxillary permanent first molar: the effect of increased mesial angulation on arch length

Fifty-four cases of ectopically erupted maxillary permanent first molars were studied with a method using the measurements obtained from photographs of the study casts. The amount of relative loss of anteroposterior arch length of the right and left sides was shown to correlate with the increased mesial angulation of the maxillary permanent first molar. The bilateral ectopic group has a significantly larger mesial angulation of the permanent first molar on a maxilla with shorter anteroposterior arch length. The relative loss of arch length with ectopic eruption of the permanent first molar limits the use of unilateral appliances for treatment. The use of an appliance with bilateral arch support seems preferable.     

328颗上颌恒切牙异常萌出原因的临床分析

目的分析导致上颌恒切牙异常萌出的原因,为提高诊疗水平提供理论依据。方法收集上颌恒切牙异常萌出的患者239例,共计328颗上领恒切牙,记录并分析导致上颌恒切牙异常萌出的原因,对数据进行统计学分析。结果328颗异常萌出的上颌恒切牙中,阻生或弯曲牙者64颗;上颌恒切牙已萌出,但位置异常者264颗,其中唇侧异常萌出45颗,腭侧异常萌出187颗,远中异常萌出32颗。对异常萌出的原因进行分析,上颌乳前牙根尖感染患者92例（38．5％）,上颌乳前牙外伤患者30例（12．6％）,上颌乳前牙滞留患者（非感染和外伤所致）26例（10．9％）,多生牙患者18例（7．5％）,上唇系带肥厚患者11例（4．6％）,口腔不良习惯、骨量不足等其它原因患者19例（7．9％）,另有43例（18．0％）患者合并局部或全身多种相关疾病。结论乳前牙根尖周炎是导致上颌恒切牙异常萌出的主要病因,儿童口腔医生应积极治疗乳牙疾病,去除或减轻导致上颌恒切牙异常萌出的因素,诱导儿童牙列和咬合功能的正常发育。     

弹弓式磨牙远移器治疗上颌第一恒磨牙异位萌出

目的评价使用弹弓式磨牙远移器治疗第一恒磨牙异位萌出的临床效果。方法选择替牙期不可逆性第一恒磨牙异位萌出患者8例,男3例,女5例,年龄6.8~9.5岁,平均8.6岁。所有病例均存在不同程度的第二乳磨牙远中根吸收。采用弹弓式磨牙远移器标准型或简化型矫治器治疗,推第一恒磨牙向远中移动,使第一恒磨牙与第二乳磨牙远中面脱离接触并最终萌出到正常位置。结果所有病例第一恒磨牙牙冠均向远中移动并竖直,与第二乳磨牙脱离接触。治疗时间1.5~4.0个月,平均2.2个月。结论弹弓式磨牙远移器是治疗第一恒磨牙异位萌出的有效方法。     

Eruption of third permanent molars after the extraction of second permanent molars. Part 1: Assessment of third molar position and size.

The eruptive path of third molars after extraction of second molars was examined in 63 patients. Panoramic radiographs from the start and the end of active treatment and 3 or more years after treatment were assessed. Study models were used to compare the size of the second and third molars and to assess the final position of the third molars. All third molars erupted; none became impacted. During eruption, maxillary third molar crowns uprighted and maintained their angulation as they came into occlusion. Mandibular third molar crowns continued to upright significantly mesiodistally after active treatment, with space closure the result of horizontal translation rather than mesial tipping. Further uprighting occurred once occlusion was established, although few became as upright as the second molars they replaced. However, mandibular third molar roots were frequently curved distally, thus the third molar crown position was invariably better than the overall tooth angulation would suggest, by 16.5 degrees on average. Model analysis (Richardsons' scoring system) showed 96% of mandibular and 99% of maxillary third molars erupted into a good or acceptable position. Limitations of this scoring system are discussed. The mesiodistal size of third molars was suitable to replace second molars; on average, mandibular third molars were 0.55 mm larger and maxillary third molars were 0.7 mm smaller than second molars.     

第一恒磨牙异位萌出倾斜角度与第二乳磨牙牙根吸收程度相关性研究

目的    通过曲面体层片测量分析第一恒磨牙异位萌出倾斜角度与第二乳磨牙牙根吸收程度的相关性。方法    选取2015—2020年于中山市人民医院儿童口腔科就诊的第一恒磨牙异位萌出患儿473例,共计患牙690颗,将其相邻第二乳磨牙牙根吸收程度分为Ⅰ ~ Ⅳ级。测量第一恒磨牙近中倾斜角度,并分析其与第二乳磨牙牙根吸收程度的相关性。结果    上颌第二乳磨牙牙根吸收Ⅱ ~ Ⅳ级的相邻第一恒磨牙倾斜角度依次为（102.2 ± 8.5）、（98.8 ± 8.8）、（92.7 ± 8.5）°,两者之间存在显著的负相关性（r = -0.4,P < 0.05）。下颌第二乳磨牙牙根吸收Ⅰ ~ Ⅳ级的相邻第一恒磨牙倾斜角度依次为（58.5 ± 6.4）、（61.4 ± 8.4）、（61.9 ± 9.4）、（61.7 ± 9.0）°,两者之间无显著相关性（r = 0.1,P > 0.05）。结论    上颌第一恒磨牙异位萌出时,其近中倾斜角度越小,越可能导致并加重第二乳磨牙牙根的异常吸收。     

不同面部生长型正常少年的后牙近远中向倾斜度研究

目的研究恒牙列初期正常少年人群的面部生长型与后牙近远中向倾斜度的关系。方法选择163例正常少年为研究对象,根据面部生长型分为垂直、平均、水平生长型3组,均拍摄X线头颅定位侧位片并进行X线头影测量分析,研究其上下颌后牙近远中向倾斜度及上下颌后牙牙体长轴交角的差异。结果垂直生长型24例,平均生长型96例,水平生长型43例。垂直生长型与水平生长型、水平生长型与平均生长型之间的上下颌第一磨牙和第一、二前磨牙牙体长轴近远中向倾斜度均存在统计学差异（P<0.05）,但垂直生长型与平均生长型之间的差异无统计学意义（P>0.05）。3组的上下颌后牙牙体长轴交角的差异无统计学意义（P>0.05）。结论恒牙列初期正常人群中不同面部生长型有各自相协调的后牙近远中向倾斜度。     

Interceptive management of eruption disturbances: case report

The aim of the present report is to describe a case of a patient with eruption disturbances of an ankylosed lower primary second molar, delayed development of a maxillary permanent canine associated with an odontoma and a class III dental malocclusion. In such a case the objectives of treatment are: to prevent impaction of the lower second premolar and tipping of the lower first molar; to establish correct anterior overbite and overjet and to control the development of the permanent upper canine.     

Ankylosis of primary molar along with congenitally missing first permanent molar

Ankylosis of primary mandibular molars has been routinely found to be associated with various developmental disturbances in permanent dentition such as aplasia of the succedaneous tooth, ectopic eruption of the premolar, infraoclusion of the ankylosed tooth leading to tipping of the first permanent molar etc. This article describes a rare case where there was ankylosis of a mandibular second primary molar along with congenitally missing first permanent molar which resulted in the transposition of second premolar. Treatment options and prognosis of the case are discussed.     

Labiolingual and mesiodistal positioning of maxillary permanent incisors during the eruption process

This study aimed to establish radiographical parameters concerning the tipping, the labiolingual positioning and the angulation of the maxillary permanent incisors in the mixed dentition. Three groups of 20 cephalograms and 20 orthopantomographic radiographs taken from children aging from 7 to 12 years old, with normal occlusion were compared. The Group I presented only the eruption of the central permanent incisors, the Group II presented both the central and lateral permanent incisors and the Group III presented central, lateral incisors and permanent canine teeth. The tipping and the labiolingual positioning were measured, respectively, using U1/PP and U1<-->AVERT. Mesiodistally, the angles between the teeth axis and the line that touched the lower border of the orbit in the orthopantomographic radiographs were measured. The mean values of tipping, labiolingual positioning and angulation of the central and lateral incisors obtained from Groups I, II and III were respectively 112 degrees, 1.2 mm, 90.4 degrees and 91.7 degrees; 112 degrees, 2.6 mm, 89.5 degrees and 96.8 degrees and 114 degrees, 2.7 mm, 87.4 degrees and 92.6 degrees. The tipping levels were similar for all groups, the mean values of the labiolingual positioning were significantly different at 5% when Group I was compared to both Groups II and III. And the mean values of the angulation were significantly different 5% for the central incisors between Groups I and III, and at 1% for the lateral incisors between Groups I and II, and, II and III.     

Evaluation of maxillary molar distalization with the distal jet: a comparison with other contemporary methods

Maxillary molar distalization is an increasingly popular option for the resolution of Class II malocclusions. This communication describes the effects of one particular molar distalizing appliance, the distal jet, in a sample of 20 consecutively treated and growing subjects (11 females, nine males; mean starting age of 13) and compares these effects with those of similar devices. Pre- and postdistalization cephalometric radiographs and dental models were analyzed to determine the dental and skeletal effects. The distal jet appliances were constructed using a biomechanical couple to direct the distalizing force to the level of the maxillary first molar's center of resistance. The distal jet was the only appliance used during the distalization phase of treatment. Examination of the cephalometric tracings demonstrated that the crowns of the maxillary first molars were distalized an average of 3.2 mm into a Class I molar relationship. In the process, the first molars were tipped distally an average of 3.1 degrees, however, the amount of tipping in each case was influenced by the state of eruption of the second molar. In subjects whose second molars had erupted only to the level of the apical third of the first molar roots, distal tipping was almost twice that seen when the second molar had completed their eruption. Anchorage loss measured at the first premolars averaged 1.3 mm, but the crowns tipped 3.1 degrees distally because of the design of the appliance. The maxillary incisors were proclined an average of 0.6 degrees with minimal effect on the mandibular plane angle and lower facial height. This study suggests that the distal jet appliance effectively moves the maxillary molars distally into a Class I molar relationship with minimal distal tipping, however, some loss of anchorage is to be expected during this process. The distal jet appliance compares favorably with other intraoral distalization devices and with mechanics featuring mandibular protraction for the resolution of patients with Class II, despite the fact that these types of mechanics address different jaws.     

Enamel defects and ectopic eruption in a child with Usher syndrome and a cochlear implant

BACKGROUND: Usher syndrome is a genetic disorder consisting of progressive loss of vision and hearing. CASE REPORT: The paper describes an 8-year-old girl with Usher syndrome type I who presented with generalized defects of the permanent dentition and ectopic eruption of the right maxillary first permanent molar. A cochlear implant had been fitted for her hearing loss, and the report reviews the implications of this device for dental treatment. The impacted first permanent molar was encouraged to erupt into the correct position by shaving the distal surface of the second primary molar. CONCLUSION: This is the first report to describe in detail an association between Usher syndrome and enamel defects.     

Dentoalveolar and skeletal changes associated with the pendulum appliance.

The purpose of the study was to examine the dentoalveolar and skeletal effects of the pendulum appliance in Class II patients at varying stages of dental development and with varying facial patterns (high, neutral, and low mandibular plane angles). Specifically, the amount and nature of the "distalization" of the maxillary first molars and the reciprocal effects on the anchoring maxillary first premolars and incisors were studied, as were skeletal changes in the sagittal and vertical dimensions of the face. Pretreatment and posttreatment cephalometric radiographs obtained from 13 practitioners were used to document the treatment of 101 patients (45 boys and 56 girls). The average maxillary first molar distalization was 5.7 mm, with a distal tipping of 10.6 degrees. The anchoring anterior teeth moved mesially, as indicated by the 1.8-mm anterior movement of the upper first premolars, with a mesial tipping of 1.5 degrees. The maxillary first molars intruded 0.7 mm, and the first premolars extruded 1.0 mm. Lower anterior facial height increased 2.2 mm; there was no significant difference in lower anterior facial height increase between patients of high, neutral, or low mandibular plane angles. In patients with erupted maxillary second molars, there was a slightly greater increase in lower anterior face height and in the mandibular plane angle and a slightly greater decrease in overbite in comparison to patients with unerupted second molars. Similar findings were observed in patients with second premolar anchorage versus those with second deciduous molar anchorage. The results of this study suggest that the pendulum appliance is effective in moving maxillary molars posteriorly during orthodontic treatment. For maximum maxillary first molar distalization with minimal increase in lower anterior facial height, this appliance is used most effectively in patients with deciduous maxillary second molars for anchorage and unerupted permanent maxillary second molars, although significant bite opening was not a concern in any patient in this study.