Three-dimensional inclination of the dental axes in healthy permanent dentitions--A cross-sectional study in a normal population

The 3-dimensional (3-D) inclination of the facial axis of the clinical crown (FACC) and the size of the clinical crowns were measured in 100 white northern Italians. The subjects consisted of 22 girls and 21 boys, ages 13-15 years (adolescents), and 31 women and 26 men, ages 16-26 years (adults), all with a complete permanent dentition and Class I dental relationships. The 3-D coordinates of dental landmarks were obtained with a computerized electromagnetic digitizer. Clinical crowns heights and FACC inclinations in the anatomical frontal and sagittal planes relative to 2 reference planes, maxillary and mandibular (between the incisive papilla and the intersection of the palatal/lingual sulci of the first permanent molars with the gingival margin), were calculated. Ages and sexes were compared by ANOVA. On average, the frontal plane FACCs of most teeth converged toward the midline plane of symmetry. In contrast, the incisors diverged from the midline plane or were nearly vertical. Within each quadrant, the inclinations of the postincisor teeth progressively increased. In the sagittal plane, most teeth had a nearly vertical FACC. FACC inclinations showed sex- and age-related differences (P < .05). In the frontal plane, the canines, premolars, and molars were more inclined in adolescents than in adults. In the sagittal plane, a large within-group variability was observed. Clinical crown height was significantly larger in males than in females in all maxillary and mandibular canines, premolars, second molars, maxillary central incisors, and first molars. With age, some degree of dental eruption was found in maxillary and mandibular canines, maxillary second premolars, and molars. The age-related decrease in FACC inclination may be the effect of a progressive buccal and mesial drift.     

Mesiodistal root angulation of permanent teeth in children with mixed dentition and normal occlusion

Objective

There is little information regarding the mesiodistal angulation of permanent teeth in mixed dentition. The aim of this study was to evaluate mesiodistal root angulation of permanent incisors, canines and first molars of 100 Brazilian children, using a new horizontal reference plane based on the midpoint of the intercuspation of primary canines and permanent first molars in panoramic radiographs during the mixed-dentition phase.

Material and methods

Children were equally divided between the genders with a mean age of 8.9 years (SD=0.76), normal occlusion and no eruptive disturbances.

Results

The angulation of the permanent maxillary first molars was close to the vertical, whereas the mandibular molars presented approximately 25 degrees of distal root angulation. The maxillary canines were the most distally angulated teeth, whereas the permanent mandibular canines were vertically positioned. The evaluation of the anterior maxillary area showed vertical position of permanent lateral, and central incisors with a slight distal angulation, whereas the permanent mandibular incisors tended to a mesial radicular convergence.

Conclusions

The proposed reference line could be useful in mixed dentition root angulation evaluation; there was a slight asymmetry in the mesiodistal angulation among homologous teeth, and also a small variation between the male and the female groups, but no difference between 8-and 10-year-old children.     

Relationship between maxillary canine intra-alveolar position and maxillary incisor angulation: a cone beam computed tomography study

The aims of the present study were to evaluate the angulation and inclination of permanent maxillary incisors and to correlate the results to the intra-alveolar permanent maxillary canine position during mixed dentition, using cone beam computed tomography (CBCT). The subjects were 30 children aged 7 to 10 years in the inter-transitory period of mixed dentition (permanent incisors and first molars erupted; primary canines, first and second molars erupted; and permanent canines intraosseous). The CBCT scans were obtained and, using the Dolphin Imaging(?) software - version 11.0, 3D images were reconstructed and the measurements were performed. The angulation of the right and left lateral and central maxillary incisors was measured in relation to the sagittal plane and their inclination was measured in relation to the coronal plane. The intra-alveolar height of the right and left maxillary canines was measured from the cusp tip to the axial plane. Pearson's correlation at 5% significance level showed positive correlation between the canine height and the lateral incisor angulation. It was concluded that the intra-alveolar position of the maxillary canines has a direct influence on the angulation of maxillary incisors, especially the lateral incisors.     

Transition of molar relationships in different skeletal growth patterns.

This study investigated maxillary and mandibular growth differences and their effect on the changes in molar relationships from early transitional dentition to adult permanent dentition. Various landmarks were identified and measurements made on the longitudinal cephalometric radiographs of 40 people. The subjects were classified into 3 groups based on the amount of sagittal skeletal growth difference between the jaws. In group A, the mandible grew more than did the maxilla; in Group B, growth was about the same; and in group C, the maxilla grew more than did the mandible. The results revealed that skeletal growth differences between the jaws significantly influenced the changes in molar relationship during the transitional dentition, not only by translating basal bones but also by altering the amount of physiologic mesial shift in the dentition. However, the skeletal growth difference during the permanent dentition did not influence the changes in molar relationship. The sagittal growth difference between the jaws was largely absorbed by a dentoalveolar compensation. Tooth movement showed different characteristic features depending on the amount of the skeletal growth difference: (1) If the mandible grew more than did the maxilla, the growth difference was mostly absorbed by mesial displacement of the maxillary first molars and counterclockwise rotation of the occlusal plane. Anterior occlusion was adjusted by mesial displacement and labial inclination of the maxillary incisors and lingual inclination of the mandibular incisors. (2) If the maxilla grew more than did the mandible, the growth difference was mainly absorbed by mesial displacement of the mandibular molars. Then the maxillary molars showed minimal mesial displacement. The occlusal plane also showed minimal rotational change. Anterior occlusion was adjusted by lingual tipping of the maxillary incisors and mesial displacement and labial tipping of the mandibular incisors.     

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.     

Meeting Reports

Abstract

This article describes treatment of a patient presenting with a class II malocclusion, maxillary and mandibular crowding, posterior crossbite and an increased deep bite, where the specific treatment goals were achieved in the early mixed dentition by only working on the primary teeth. A Haas-type rapid maxillary expansion (RME) appliance was modified to be anchored on the primary second molars and canines and activated once a day, with each activation equal to 0.20 mm. The appliance was blocked after 30 days and left as a retainer. After 6 months, the RME appliance was removed and bands were cemented to the primary second molars in order to apply traction with headgear. After complete eruption of the mandibular central and lateral incisors, sequential slicing of the lower primary teeth was performed to transfer the leeway space from the distal to the mesial part of the arch. When the patient had entered the permanent dentition, a dental class I relationship was achieved, the crossbite corrected and the crowding improved. The overjet and overbite were also improved. No permanent teeth were involved during this phase of treatment. The outcome of this case report shows that it is possible to work only on primary teeth in the mixed dentition and this can be an effective way to correct a class II malocclusion with deep bite, posterior crossbite and maxillary and mandibular crowding.     

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.     

Relationship between occlusal wear of the teeth and periodontal health

abstract – The study was undertaken in order to examine the relationship between occlusal wear and periodontal health in thc maxillary and mandibular anterior, premolar and molar regions of the human dentition. The occurrence and degree of attrition was recorded for the 4,316 fully erupted teeth of 154 males aged 19–22 years. The mandibular central incisors and the canines of both jaws were found most often to show attrition. In general, occlusal wear was found to be associated with improved cleanliness, and thus, in most areas of the dentition, also with improved periodontal conditions. At the openings of the major salivary glands, however, more calculus was found on attrited than intact teeth, and consequently, no improvement of the periodontal status was found in mandibular anterior teeth and maxillary molars. As the degree of attrition was not influenced by the frequency of toothbrushing, it seems evident that the masticatory function which results in occlusal wear of the teeth, has an effect per se on periodontal health.     

Surface distribution of enamel opacities following orthodontic treatment

A cross-sectional study was carried out to determine the prevalence and severity of enamel opacities occurring on different surfaces of the dentition as well as the distribution of these lesions on individual teeth following orthodontic treatment. The sample consisted of 527 patients examined prior to and 269 other patients examined after completion of multibanded orthodontic treatment. The results showed that following orthodontic treatment there was a significant increase in the prevalence of enamel opacities on the vestibular and lingual surfaces of the dentition. The increase was significantly greater on the cervical and middle thirds of the crown. Among individual teeth, there was a statistically significant increase in the prevalence and severity of enamel opacities on the maxillary and mandibular first molars, the maxillary lateral incisors, and the mandibular lateral incisors and canines. The increase was greatest on the cervical and middle thirds of the vestibular surface of these teeth.     

A Study of Anterior Guidance

Purpose This study focuses on the curvature and inclination of the lingual surfaces of the maxillary anterior teeth from the transition point on the cingulum to the incisal edge. Materials and Methods On 32 sets of mounted casts, 768 measurements were made of the curvature of the lingual surfaces utilizing radius gauges. The inclination of the lingual surface relative to the occlusal plane was recorded. The relationship of the incisal edge of the mandibular teeth to the transition point on the cingulum of the maxillary teeth was determined. Centric occlusion contact was noted on each tooth. Results Significant differences were found between the measured areas of any one tooth and between the types of teeth. The average radius ranged from 20.5 mm on the mesial ridge of the canine to 5.3 mm in the fossa of the central. The average inclination of the lingual surfaces was 46%. In centric occlusion, 97% of the canines and 59% of the centrals and laterals were in contact with the opposing teeth. These contacts occurred 2.8 mm incisal to the transition point. The centrals contacted two opposing teeth (45%), and canines contacted one opposing tooth (53%). Conclusions The function and curvature of the incisor teeth vary considerably from those of the canines. Overcontouring the lingual surfaces of the maxillary incisors to gain contact is not normal and may be detrimental.     

The morphological studies of root resorption of maxillary primary canines and their relation with the position of successive permanent teeth using Micro-CT

The purpose of this study is to clarify the root resorption of maxillary primary canines in relation to the development of successive permanent teeth. It was observed the maxilla of dry skulls of Indian children, using Micro-CT, and measured shortest distance between the root surface of maxillary primary canine and the bony crypt of maxillary canine. The bony crypt including successive canine was positioned almost directly above the root of primary canine and located superior to another bony crypts in the primary dentition stage. When the first molars reached the alveolar crest in addition to the primary dentition stage, the bony crypt of canine grew, showing the distal inclination of the superior margin and mesial inclination of the inferior margin. After the stage which is central incisors reached the alveolar crest, root resorption of primary canines was observed on the lingual side nearby the root apex and the bony crypt of canine was adjacent to the nasal cavity. It was quantitatively shown that the distance between the roots of primary maxillary canine and canine bony crypts reduced from central incisors reached the alveolar crest to lateral incisors reached that.     

Normal torque of the buccal surface of mandibular teeth and its relationship with bracket positioning: a study in normal occlusion

This study evaluated the degree of buccolingual inclination of mandibular tooth crowns relative to torque. For such purpose, mandibular and maxillary stone casts from 31 Caucasian Brazilian adults with normal occlusion, pleasant facial aspect and no history of previous orthodontic treatment were examined. A custom device was developed for measuring the degree of inclination (torque) of bracket slots of orthodontic appliances relative to the occlusion plane, at three bonding height: standard (center of clinical crown), occlusal (0.5 mm occlusally from standard) and cervical (0.5 mm cervically from standard). Except for the mandibular incisors, which presented a small difference in torque from one another (lingual root torque for central incisors and buccal root torque for lateral incisors), the remaining average values are close to those found in the literature. Due to the convexity of the buccal surface, the 1-mm vertical shift of the brackets from occlusal to cervical affected the values corresponding to the normal torque, in approximately 2 degrees in central and lateral incisors, 3 degrees in canines and 8 degrees in premolars and molars.     

Design and implementation of a hybrid genetic algorithm and artificial neural network system for predicting the sizes of unerupted canines and premolars

The aim of this study was to develop a novel hybrid genetic algorithm and artificial neural network (GA-ANN) system for predicting the sizes of unerupted canines and premolars during the mixed dentition period. This study was performed on 106 untreated subjects (52 girls, 54 boys, aged 13-15 years). Data were obtained from dental cast measurements. A hybrid GA-ANN algorithm was developed to find the best reference teeth and the most accurate mapping function. Based on a regression analysis, the strongest correlation was observed between the sum of the mesiodistal widths of the mandibular canines and premolars and the mesiodistal widths of the mandibular first molars and incisors (r = 0.697). In the maxilla, the highest correlation was observed between the sum of the mesiodistal widths of the canines and premolars and the mesiodistal widths of the mandibular first molars and maxillary central incisors (0.742). The hybrid GA-ANN algorithm selected the mandibular first molars and incisors and the maxillary central incisors as the reference teeth for predicting the sum of the mesiodistal widths of the canines and premolars. The prediction error rates and maximum rates of over/underestimation using the hybrid GA-ANN algorithm were smaller than those using linear regression analyses.     

Distribution of developmental defects of tooth enamel by tooth-type in 11–12-year-old children in South Wales

The distribution of enamel developmental defects in 759 11-12-yr-old children from South Wales is described. Overall, 8% of maxillary teeth were affected compared to 3.6% of mandibular teeth. Most teeth were affected equally on right and left sides of the mouth except for maxillary lateral incisors, which had significantly more defects on the right (P less than 0.05) and maxillary first molars, which had significantly more defects on the left (P less than 0.025). Maxillary central incisors (18.7%) were affected by enamel defects most often followed by maxillary first molars (8.1%) and maxillary lateral incisors (7.2%). The ranking order of the teeth varied when the prevalence of the different types of defects was assessed. White demarcated opacities were seen most often in maxillary central incisors (10.8%), yellow demarcated opacities in maxillary first molars (1.8%), diffuse opacities in maxillary central incisors (6.6%) and hypoplasias in mandibular first premolars (1.5%). Defects of all types occurred most frequently on the buccal surfaces of the teeth. In premolar and molar teeth more defects occurred on the occlusal surface than on the lingual.     

Ectopic eruption of the maxillary central permanent incisors and mandibular first permanent molars: report of an unusual case.

Ectopic eruption is a disturbance in which the tooth does not follow its usual course. Among its more important etiologic factors are macrodontism, shortened arch length, posterior positioning of the maxilla, atypical eruption angle, and genetic factors. This article reports a rare case of ectopic eruption of 4 permanent teeth, maxillary central incisors and mandibular first molars, in a child aged 7 years and 11 months, in which the treatment consisted of extracting the maxillary primary central incisors and making an orthodontic intervention on the mandibular arch. A bilateral fixed appliance containing 2 hooks with loops, 1 buccal and the other lingual, was placed on the mandibular primary first molars. The hooks were activated in a niche made of light-curing resin on the occlusal surface of the mandibular permanent molars, to bring about the distal drift of these teeth. After 6 months, complete eruption of the mandibular permanent molars occurred, and a slight displacement of the maxillary permanent central incisors toward the median line was noted. The importance of early, adequate treatment is discussed.     

无托槽隐形矫治拔牙病例的后牙不同轴倾度对牙齿三维力学影响

目的 研究无托槽隐形矫治技术拔除双侧上颌第一前磨牙病例整体内收前牙，后牙不同轴倾度时，各个牙齿的瞬时受力情况。方法 设置4组后牙不同轴倾度的上颌牙列，T1组后牙为正常牙合轴倾度，T2组后牙在T1组基础上后倾5°,T3组后牙在T1组基础上前倾5°,T4组后牙在T1组基础上前倾10°。拔除双侧第一前磨牙，整体内收前牙0.25 mm,在矫治器六轴力传感器测试平台上测量4组牙列中各个牙齿在三维方向的瞬时力。每组牙列设计12副隐形矫治器。结果 与T1组相比，T2组切牙伸长力减小，尖牙远中向力增加，后牙近中向力减小，磨牙颊向和伸长力增大，差异均有统计学意义(P<0.05)。与T1组相比，T3和T4组切牙舌向力和伸长力增大，尖牙远中向力增大，后牙近中向力也增大，磨牙颊向和伸长力增大，差异均有统计学意义(P<0.05)。结论 后牙后倾时利于前牙转矩的表达，有助于保护后牙支抗，但增加了磨牙的颊向力和伸长力。后牙前倾时，前牙更容易出现转矩丢失，覆牙合加深的现象。后牙越前倾，覆牙合越容易加深，后牙支抗容易丢失。     

Clinical crown length and reduction in overjet, overbite, and dental height with orthodontic treatment

To evaluate the clinical crown length relative to fixed-appliance orthodontic treatment of excessive overjet and deep overbite and to correlate such changes to the vertical dental height, the following measurements were undertaken for 12 females and 8 males, between the ages of 16 and 20 years, on three separate occasions--2 days before banding, 2 days after debanding, and 12 months after debanding: (1) overjet, overbite and dental height measured from right lateral cephalometric x-ray films; (2) clinical crown length, measured from study models, of 400 teeth divided into four groups--maxillary incisors and canines (120 teeth), maxillary second premolars and first molars (80 teeth), mandibular incisors and canines (120 teeth) and mandibular second premolars and first molars (80 teeth); and (3) gingival condition by means of the gingival index of L?e and Silness. Fixed edgewise orthodontic appliances were used and the four first premolars were extracted. From the results of the investigation, the following conclusions were evident: after a 12-month follow-up observation period, the achieved reduction in overjet, overbite, and dental height showed relapses of 9%, 11%, and 29%, successively; only 7% of the 400 teeth examined showed reductions in clinical crown length. This change was probably the result of gingival hyperplasia. The gingival condition greatly improved by approximately 64% after 12 months of debanding, accompanied by 25% to 50% relapse in the amount of change in clinical crown length (noted 2 days after debanding); and the intrusive tooth movement during orthodontic correction of deep overbite was the result of vertical movement of the tooth, with its investing tissues and soft-tissue attachment, into the jaws.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tooth dimensions in hypodontia patients,their unaffected relatives and a control group measured by a new image analysis system

Tooth dimensions were compared between index patients with severe hypodontia (six or more congenitally missing teeth), their relatives with a full complement of teeth, and a control group. The groups consisted of 12 index cases (seven females and five males), 21 relatives without hypodontia (13 females and eight males), and a control group of 10 males and 10 females with complete dentitions, and no family history of hypodontia. All formed teeth were imaged buccally and occlusally from study models, with a digital camera linked to a computer. The images were acquired and measured using Adobe Photoshop and Image Pro Plus, respectively. Mesiodistal, buccolingual, or occlusogingival area and perimeter measurements were determined from each image. In the index hypodontia group tooth dimensions were significantly smaller (P < 0.001, Bonferroni corrected level) for maxillary and mandibular canines, and first premolars for all dimensions from the buccal view, and for maxillary and mandibular canines and first premolars, maxillary central incisors, maxillary first molars, mandibular lateral incisors, and mandibular second premolars for all dimensions from the occlusal view. In the relatives without hypodontia compared with the control group, mesiodistal dimensions from the buccal view were significantly smaller (P < 0.001) for the central incisors and maxillary first and second premolars, and for the maxillary and mandibular first premolars for all dimensions from the occlusal view. There was a trend for the tooth dimensions of all teeth in the index group to be smaller compared with the control group. The tooth dimensions of the relatives without hypodontia also tended to be smaller than the control group, but were larger than those of the index cases.     

Dens evaginatus of anterior teeth (talon cusp): report of five cases.

The talon cusp, or dens evaginatus of anterior teeth, is a relatively rare dental developmental anomaly characterized by the presence of an accessory cusplike structure projecting from the cingulum area or cementoenamel junction. This occurs in either maxillary or mandibular anterior teeth in both the primary and permanent dentition. This article reports five cases of talon cusp, two of them bilateral, affecting permanent maxillary central and lateral incisors and canines that caused clinical problems related to caries or occlusal interferences.     

Buccolingual inclination of first molars in untreated adults: A CBCT study

Objective:To evaluate the buccolingual inclinations of maxillary and mandibular first molars in untreated adults.Materials and Methods:Fifty-nine subjects (14 males and 45 females; mean age, 41.2 years) with no missing teeth, no crossbite, and minimal crowding were included. For each subject, a CBCT was taken. The long axis of each first molar was determined, and the inclination of each molar was measured using the long axis and the floor.Results:One hundred seventeen out of 118 mandibular first molars measured had a lingual inclination, with a mean of 12.59° ± 5.47°. For the maxillary first molars, 107 out of 118 had a buccal inclination, with a mean of 4.85° ± 4.22°.Conclusions:There is a curvature to the inclinations of first molars in untreated adults, where the maxillary molars have a slight buccal inclination and mandibular molars have a slight lingual inclination.