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。     

Fully digital fabrication of an occlusal device using an intraoral scanner and 3D printing: A dental technique

This dental technique describes a fully digital method for fabricating occlusal devices using a complete-arch intraoral scan and 3D printing. The maxillary and mandibular arches of a healthy, fully dentate volunteer were digitized using an intraoral scanner. A second scan and modified recording of the centric relation enabled a virtual arrangement of the maxillary and mandibular arches, both in centric relation and in the desired vertical dimension of occlusion. An occlusal device was subsequently designed virtually and fabricated from a light-polymerizing acrylic resin using a 3D printer. The occlusal device was tested for fit, occlusion, and patient-friendly handling. As only minor occlusal corrections were required, the fully digital procedure described is suitable for the fabrication of occlusal devices.     

Relationship between the pharyngeal airway space and craniofacial morphology, taking into account head posture

This study assessed the relationship between craniofacial characteristics and the size of the pharyngeal airway space (PAS), taking into account head posture. Sixty dental students 25-30 years of age (30 men and 30 women) were examined by lateral cephalometry. The data were corrected with the use of appropriate regression equations for the PAS. The PAS significantly correlated with hyoid position, maxillary and mandibular size, maxillary and mandibular prognathism, and mandibular inclination. A large, anteriorly positioned mandible was associated with a large PAS-TP (the most proximal distance between the posterior pharyngeal wall and the tongue base). Uvula length and PNS-Ba (the distance between the most posterior point of the hard palate and the most inferior point of the anterior foramen magnum) correlated with PAS-UP (the most proximal distance between the posterior pharyngeal wall and uvula). Our results suggest that the anteroposterior dimension of the PAS is substantially affected by the size of the enclosure surrounding the PAS, including the maxilla, mandible and soft palate.     

β函数拟合正常(牙合)牙弓形态的研究

目的　本研究应用β函数,通过比较正常的三种牙弓形态,评价其对不同牙弓形态的拟合程度。方法　选择22副个别正常模型(男4人,女18人),平均年龄为13.6岁。分为三组:方圆形8副、卵圆形10副、尖圆形4副。将模型平行于平面扫描到计算机。由中切牙接触点、双侧尖牙牙尖点和双侧第二恒磨牙远中颊尖点五个点确定个体弓形。计算模型上其他各点与曲线的拟合度-相关系数(r)以及各点到拟合曲线的垂直距离之和、平均距离。比较β函数对三组弓形的拟合程度。结果　1β函数模拟22副模型的拟合度-相关系数(r)均大于0.96。三组曲线拟合度-相关系数(r)没有差别。2 方圆组上、下颌牙弓各点到拟合曲线的垂直距离之和、平均距离均比尖圆组大,P<0.05。3 三组弓形的 e值具有显著性差异,P<0.01。4 上颌磨牙宽度、深度分别比下颌大 4.9mm、4.4mm, P<0.001。而上、下颌牙弓 e值没有显著差异。结论　β函数可以较好地拟合正常弓形,对尖圆形牙弓比方圆形牙弓拟合更准确。β函数参数e值大小可以区分方圆、卵圆和尖圆三种牙弓形态。正常个体上、下颌牙弓形态相似。     

Finite element analysis of stresses in the maxillary and mandibular dental arches and TMJ articular discs during clenching into maximum intercuspation, anterior and unilateral posterior occlusion

The objective of this study was to investigate distribution of stresses in the human TMJ discs, generated during clenching into various occlusal positions. The work presents a biomechanical finite element model of interaction of mandibular and maxillary dental arches and the TMJ discs of a particular person, based on real geometrical data obtained from spiral computed tomography two-dimensional images. 3D contour coordinates - point clouds were collected from these images and solid model was created. The system under investigation consisted of eight basic parts: two rigid structures representing the mandibular and maxillary dental arches, two mandibular condyles, two mandibular fossae of temporal bone, and solid models of two articular discs. The model of maxillary dental arch was fixed in space. The model of the mandibular dental arch was able to move in space synchronically with the mandibular condyles under action of applied forces, which were considered as prescribed and known at insertion points of masticatory muscles. The motion of the mandible was constrained by interdental contact interactions and contact interaction with articular discs, which were situated in between mandibular condyles and mandibular fossae of temporal bone. The model was implemented by using LS-DYNA finite element software. The obtained results presented a 3D view of stresses exhibited in the articular discs, as well as the real contact points of dental interactions at given masticatory geometry of a particular subject and the values of interaction forces. The expected practical value of the developed model is the facilitation of biomechanical evaluations of the influence of tolerances of teeth shapes and occlusal areas together with the supporting areas on the final stress distribution in the dental arches and articular discs.     

Tooth-position, arch-size, and arch-shape in the primary dentition

Tooth positions and dental arch forms are related to the growth of the cranio-facial complex. To determine the positions of primary teeth and size and shape of the primary dental arches, sixty dental casts of young children (thirty boys and thirty girls) with normal occlusions were examined. In all casts the coordinates of cusp tips of primary canines and molars, and mesial and distal line angles of primary canines and incisors were digitized. The computer-generated curves were made for the maxillary and mandibular arches using a polynomial model. The results show that there were three major cusp-to-fossa and one cusp-to-marginal ridge relations in primary molar intercuspation. On average, girl's dental arches were smaller than boy's dental arches. The mean curves of mandibular arches in anterior segments were gentler than those of maxillary arches.     

Correlation between maxillary central incisor crown morphology and mandibular dental arch form in normal occlusion subjects

The aim of this study was to evaluate the correlation between the morphology of the mandibular dental arch and the maxillary central incisor crown. Cast models from 51 Caucasian individuals, older than 15 years, with optimal occlusion, no previous orthodontic treatment, featuring 4 of the 6 keys to normal occlusion by Andrews (the first being mandatory) were observed. The models were digitalized using a 3D scanner, and images of the maxillary central incisor and mandibular dental arch were obtained. These were printed and placed in an album below pre-set models of arches and dental crowns, and distributed to 12 dental surgeons, who were asked to choose which shape was most in accordance with the models and crown presented. The Kappa test was performed to evaluate the concordance among evaluators while the chi-square test was used to verify the association between the dental arch and central incisor morphology, at a 5% significance level. The Kappa test showed moderate agreement among evaluators for both variables of this study, and the chi-square test showed no significant association between tooth shape and mandibular dental arch morphology. It may be concluded that the use of arch morphology as a diagnostic method to determine the shape of the maxillary central incisor is not appropriate. Further research is necessary to assess tooth shape using a stricter scientific basis.     

Xerox copy of the dental cast for analysis of the stability of mandibular osteotomy

Stability of the mandible was analysed with a Xerox copy of the dental cast in 35 cases of mandibular prognathism corrected by ramus osteotomies. The occlusal relationship in the Xerox copy was illustrated by superimposing two contact points on the upper and lower dental arches and the change in the position of the lower dental arch in relation to the upper dental arch was obtained by superimposing the latter on preoperative, predicted postoperative, and six months postoperative occlusions. The stability of the mandible was analysed by measuring the movement of five landmarks (two posterior, two molar and one incisor points) set around the lower dental arch to represent the movement of the mandible. The relapse was estimated by the movements of the landmarks from the predicted postoperative occlusion to the six months postoperative occlusion. The mean estimated anterior relapses at the posterior and molar points with the larger predicted movement and the incisor point were between 0.9 mm. and 2.0 mm. at six months postoperatively, whereas on the side with the smaller predicted movement, the points moved posteriorly by 0.6 mm. and 0.5 mm. Despite the fact that the amount of the predicted lateral movement was much smaller than that of the predicted posterior movement at operation, the posterior points were estimated to relapse laterally by 2.0 mm. and 1.7 mm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Skeletal profile changes related to two patterns of activator effects

A longitudinal cephalometric study was carried out on twelve boys and thirteen girls who initially exhibited Class II, Division 1 malocclusion and who were treated exclusively with activators. Twenty-four boys and fifteen girls, corresponding with the experimental subjects with respect to initial age and observation period, were selected as controls. The aim of the investigation was to examine cephalometric profile changes associated with two patterns of effects of activator treatment detected previously. The findings demonstrate that the two types of reaction bring about similar corrections of both apical base discrepancy and dental Class II relationship but clearly differ in their effects on the skeletal profile. Whereas the first type of reaction results in an improvement in mandibular retrognathism, a marked rotation of the occlusal plane, and good vertical control of the upper and lower dental arches, the second type is distinguished by a significant reduction of maxillary prognathism, downward and backward rotation of the mandible, and forward tipping of the lower incisors. Additional evidence presented further suggests that the two patterns of effects are due to differences in the construction bites of the appliances. According to this hypothesis, a great interocclusal height of an activator would lead to the first and a low construction bite to the second type of reaction.     

Proposal for a classification of Class II Division 1: contribution of Delaire's analysis

Class II division 1 dental malocclusions are present in various forms depending on the site, direction and degree of discrepancy between the arches. The ability to recognize the origin of the malocclusion is essential to decide how, and when it is necessary to treat. In this study, the Delaire's analysis was performed for 111 individuals with a Class II division I malocclusion; a classification of these cases is proposed, according to the presence or the absence of a skeletal discrepancy. In 87% of the cases, a Class II division 1 dental malocclusion was associated with a Class II skeletal discrepancy (50% maxillary prognathism, 23.5% normal maxillary relationship and 13.5% maxillary retrognathism). The lines of the cranial base, the shape and size of the mandible varied considerably. In only 6% of cases, the dental malocclusion was associated with a skeletal Class I relationship, and in 7% of cases with a Class III relationship: it was often related to retruded mandibular teeth. It was shown that Class II division 1 dental malocclusions may result from differing causes: therefore, the identification of their etiology seems essential to provide the best possible treatment, at the right period in time.     

Early developmental traits in Class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.     

Early developmental traits in class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.     

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.     

Is the postretention relapse of maxillary and mandibular incisor alignment related?

Previous studies suggest a poor association between initial and postretention pattern of incisor irregularity. One explanation may be that the incisor movements are limited by the boundaries provided by the incisors in the opposite arch. If so, postretention malalignment of the maxillary and mandibular incisors may be related. To test this hypothesis, long-term postretention study models of 96 patients with acceptable occlusion at the time of appliance removal were examined. The occlusal surfaces of the postretention study models were photocopied, and tooth anatomical contact points were digitized. An algorithm was used to fit the dental arch to the digitized points. The amount of incisor rotation and anatomical contact point displacement of maxillary and mandibular anterior teeth, relative to their respective dental arches, were computer generated. Overbite, the number of occlusal contact points in the anterior segment, and concavity of the lingual surfaces of the maxillary incisors were recorded manually. Statistical analyses demonstrated a significant association (P <.05) between the overall irregularity of the maxillary and mandibular incisors. The association did not differ among subgroups that were stratified according to overbite or number of occlusal contacts. No associations were found for the overall amount of incisor rotation in the 2 arches (P >.05). The amount and direction of displacement of antagonistic pairs of maxillary and mandibular central incisors were also associated (P <.05), but not the amount and direction of rotation (P >.05). The lingual configuration of the maxillary incisors did not affect the pattern of mandibular incisor malalignment.     

Components of adult Class II open-bite malocclusion

In an effort to identify the frequency and distribution of the dental and skeletal components of adult Class II malocclusion with and without open-bite, 124 adults, half of whom had an anterior open-bite, were evaluated. Significant differences (P less than 0.05) between the open-bite and non-open-bite groups were found for the following measurements: the posterior maxilla exhibited vertical excess in the open-bite group; the maxillary occlusal plane was less steep in the open-bite group; the mandibular occlusal plane was more steep in the open-bite group; the gonial angle was higher in the open-bite group; the mandibular plane angle was higher in the open-bite group; the mandibular ramus was positioned in a more downward and backward (clockwise) location in the open-bite group; the total and lower anterior facial height were increased in the open-bite group; and the mandible was less protrusive in the open-bite group. No significant intergroup differences were noted in the cranial base, the anteroposterior position of the maxilla or of the upper and lower incisors, the palatal plane, posterior facial height, mandibular ramus height, or mandibular body length. The results of this analysis indicate that the average Class II open-bite malocclusion is characterized by aberrations in both the maxilla and the mandible. Therapy, therefore, may frequently require surgical intervention in both jaws to successfully correct this deformity.     

255例牙冠折裂的临床分析

目的分析长期咀嚼过程中牙冠折裂的发生情况,并初步探讨冠折发生的相关因素。方法以2005年12月-2007年12月在兰州市第一人民医院口腔科就诊的255颗冠折牙为研究对象,对折裂牙的患者性别、年龄、牙位、折裂位置及形态等进行分析。结果255颗冠折牙中,1）上颌第一磨牙76颗（29.8%）,下颌第一磨牙45颗（17.6%）,上颌第二磨牙41颗（16.1%）,下颌第二磨牙37颗（14.5%）,上颌第二前磨牙32颗（12.5%）,上颌第一前磨牙15颗（5.9%）,下颌第二前磨牙9颗（3.5%）;2）折裂位置与窝沟重叠者158颗（62.0%）,发生于牙尖斜面者97颗（38.0%）。3）正常者85颗（33.3%）,面形态异常者55颗（21.6%）,型异常者115颗（45.1%）。结论牙位及形态等与牙冠折裂的发生具有一定的关系。力是牙冠折裂的基本因素,但不是唯一因素。     

The effects of Fr?nkel II treatment on arch width and arch perimeter

Changes in dental arch width and total arch perimeter in 24 Class II, Division 1 patients treated with the Fr?nkel II appliance were compared with changes in an untreated control group. Measurements were made on pretreatment and posttreatment plaster casts at three points on each of four maxillary and four mandibular teeth. Increases in width were computed at the occlusal point and compared for the two samples. A significant increase in occlusal arch width for all measures was suggestive of both a minor tipping movement of the maxillary teeth and a bodily movement of the mandibular teeth. Width development in the maxilla was greater than in the mandible. Occlusal arch width increased more in the molar and premolar regions in the maxilla and in the premolar region in the mandible. Wide arches were found to have as much increase as narrow arches. The total arch perimeter decreased significantly less in the treatment sample than in the control sample. The documented gains in arch width and arch perimeter would not be sufficient to relieve severe crowding, but could be useful in avoiding removal of teeth in borderline extraction cases.     

骨性Ⅲ类错（牙合）牙弓、基骨弓宽度及协调性分析

目的 探讨骨性Ⅲ类错（牙合）患者牙弓、基骨弓宽度及二者协调性,为临床诊断和治疗提供理论依据.方法 选择骨性Ⅲ类错（牙合）患者33例为实验组,47例个别正常（牙合）为对照组,利用锥形束CT扫描颌面部,将扫描后图像导入Mimics10.01图像处理软件分别测量牙弓宽度、基骨弓宽度,并计算上下颌对应宽度之差,对测量结果进行独立样本t检验.结果 骨性Ⅲ类错（牙合）组上颌牙弓宽度与个别正常（牙合）组比较无显著性差异,但下颌牙弓宽度大于正常（牙合）,其中下颌第一磨牙处平均宽度正常（牙合）为（56.26±3.09）mm,骨型Ⅲ类患者为（57.78±3.22）mm,差异有统计学意义（P＜0.05）;骨性Ⅲ类错（（牙合）上颌基骨弓宽度测量值均小于对照组,其中在上颌第二前磨牙处正常（骀）为（59.11±5.97）mm,骨型Ⅲ类患者为（56.23±5.28）mm,有统计学差异（P＜0.05）,下颌基骨弓宽度均大于对照组,其中在前磨牙及第一磨牙处分别为（47.44±2.96）mm、（59.81±3.87）mm和（76.20±4.20）mm,与正常（牙合）相比差异显著（P＜0.05）.骨性Ⅲ类错（牙合）上下颌基骨弓宽度差值均小于正常（牙合）（P＜0.01）,而牙弓宽度差值仅在尖牙处差异显著（P＜0.05）,其余牙位测量项目无统计学差异.结论 ①骨性Ⅲ类错（牙合）组上颌基骨宽度发育不足,下颌基骨宽度发育过度.②骨性Ⅲ类错（牙合）的宽度不协调表现在基骨水平,牙弓对基骨弓宽度不调有代偿.     

小型下颌后退位（牙合）板在前牙反（牙合）矫治中的应用

目的：在前牙反（牙合）矫治中应用一种小型下颌后退位（牙合）板后退下颌,评价其矫治AngleⅢ类功能性-轻、中度骨性前牙反（牙合）病例的临床应用效果.方法：应用小型下颌后退位（牙合）板治疗反（牙合）328例.在打开咬合的同时后退下颌,同时粘固上下颌托槽进行排齐整平.结果：患者侧貌在戴用后退位（牙合）板后明显改善,下颌的有效后退使反（牙合）的矫治变得简单化,治疗时间较传统矫治明显缩短.远期随访疗效肯定.结论：小型下颌后退位（牙合）板适用于下颌可适度后退的前牙反（牙合）病例,可快速矫治前牙反（牙合）.是较固定反式TBA联合前牵引更为理想的装置,结构更小巧,制作更简便,更适用于临床应用.     

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.