Dentoalveolar compensation related to variations in sagittal jaw relationships

The purpose of this study was to investigate dentoalveolar compensation for variations in sagittal jaw relationships in 44 adult females with normal incisor relationships and either skeletal Class I or skeletal Class III jaw relationships. Cephalometric analysis was performed to evaluate sagittal jaw relationship, maxillary and mandibular incisor inclination, and the cant of the occlusal plane. Molar relationships were evaluated from study models. Correlation analysis was performed between skeletal and dental measurements. The most appropriate cephalometric parameters describing dental compensation quantitatively were SN-AB as a skeletal measurement and SN-U1, SN-L1, and SN-OP as dental measurements. Among the compensatory dentoalveolar changes, lower incisor inclination was strongly related to the sagittal jaw relationship and played an important role in obtaining a normal incisor relationship. Compensatory changes in the occlusal plane angulation were slight when compared with changes in the incisor regions. A Class I molar relationship was rare when SN-AB exceeded 84 degrees, even when incisor relationships were normal.     

头影测量中冠长轴与牙长轴倾斜在正常 的表现

目的 本研究通过测量并分析正常头影测量中的切牙冠长轴与牙长轴的倾斜角度,以期为错畸形的方案选择及疗效评判提供参考。方法 按照Andrews正常六项标准纳入120名受试者,于自然头位下拍摄头颅侧位片,并测量其上下颌切牙冠长轴与真性垂线（TV）、平面（OP）及牙长轴的交角。结果 上颌切牙冠长轴与TV交角为11.72°±4.71°,与OP交角为73.29°±5.69°,与上颌切牙长轴交角为20.04°±3.71°;下颌切牙冠长轴与TV、OP和牙长轴的交角分别为16.03°±5.40°、81.76°±4.81°和14.82°±4.01°。多数上颌切牙冠长轴与牙长轴夹角分布于15°~25°之间,多数下颌切牙冠长轴与牙长轴夹角分布于10°~20°之间。结论 在使用头颅侧位片制订治疗方案和评估疗效时,除了关注上下颌切牙的牙长轴倾斜程度,还应考虑上下颌切牙的冠长轴倾斜情况。     

A comparison of 3 methods of face-bow transfer recording: implications for orthognathic surgery.

PURPOSE: The purpose of this study was to compare the occlusal plane inclination of models mounted using 3 different systems for face-bow transfer with the actual occlusal plane inclination as measured on a cephalometric radiograph. PATIENTS AND METHODS: Twenty-two subjects were enrolled in this study. Three alginate impressions of the maxillary dentition were taken, and 3 stone dental models were produced for each subject. Face-bow recordings were obtained on each subject using the SAM Anatomical Face-bow (Great Lakes Orthodontics Products, Ltd, Tonawanda, NY), the Erickson Surgical Face-bow (Great Lakes Orthodontics Products, Ltd) and a new technique developed by one of the authors (J.G.). For each subject, the dental models were mounted on a SAM articulator using each of the 3 face-bow recordings. Finally, a lateral cephalometric radiograph was obtained for each subject. The occlusal plane inclination was measured on the models and on the cephalometric radiographs. Differences among groups were tested using a 1-way analysis of variance. Bonferroni test was used for post hoc comparison between different pairs of groups. RESULTS: The average occlusal plane inclination using the SAM Anatomical Face-bow was 7.8 degrees +/- 4.2 degrees greater than the actual-a difference that was statistically significant. The mean occlusal plane inclination of the models obtained using the Erickson Surgical Face-bow was 4.4 degrees +/- 2.2 degrees greater than the actual-a difference that was also statistically significant. The mean occlusal plane inclination of the models obtained by the new technique was only 0.9 degrees +/- 1.2 degrees greater than the actual; this difference was not statistically significant. CONCLUSIONS: The new mounting technique is more accurate than the conventional SAM Face-bow or the Erickson Face-bow for reproducing the actual occlusal plane inclination.     

Dentoalveolar compensation in negative overjet cases

The purpose of this study was to investigate dentoalveolar compensation in negative overjet cases. Eighty-eight adult females with either skeletal Class I or skeletal Class III jaw relationships were examined. Of the total, 44 cases showed anterior crossbite and the remaining 44 cases had normal incisor relationships. Four cephalometric parameters were measured: the sagittal jaw relationship, maxillary and mandibular incisor inclination, and the occlusal plane angulation. In the negative overjet cases, correlation analysis was performed between the skeletal and dental measurements. Stepwise discriminate analysis was carried out to separate the negative and normal overjet cases. Compensatory changes for sagittal jaw discrepancies in the negative overjet cases were statistically confirmed for both incisor inclination and occlusal plane angulation. However, the compensatory effects were weaker than in the normal overjet cases. The discriminate analysis successfully separated the normal and negative overjet cases, suggesting that negative overjet results from insufficient dentoalveolar compensation for variations in the sagittal jaw relationships.     

Anterior open bite--cephalometric evaluation of the dental pattern

The purpose of this study was to compare the dental pattern of patients with anterior open bite malocclusion to that of individuals with normal overbite by utilization of lateral cephalograms, panoramic radiographs and study casts. The findings showed that there was no significant difference in the inclination of the occlusal plane (SN.PlO) and position of the maxillary and mandibular incisors (1-NA, 1-NB) between both groups of individuals; but the angles of inclination of the maxillary and mandibular incisors (1.1, 1.NA and 1.NB) differed statistically between patients with anterior open bite of the individuals that presented normal overbite, which suggests that the anterior open bite may be of dental origin.     

模型重叠评价上颌切牙牙轴变化的可靠性研究

目的 探讨运用模型重叠的方法 评价上颌切牙牙轴变化的可靠性。方法 选取28例完成正畸治疗的患者,入选标准包括上颌对称拔除第一或者第二前磨牙,无偏斜的上颌中线等。治疗前、后拍头颅侧位片和制取寄存模型。头影测量分析头颅侧位片的中切牙牙轴变化,模型用Roland LPX-1200三维点激光扫描仪数字化,基于腭部区域重叠,使用测量软件(Rapidform 2006)分析治疗前后中切牙牙轴变化。用SPSS10.0统计软件对两种测量方法的结果行统计分析。结果 本研究样本的头影测量显示切牙牙轴平均内收14.47°,模型测量中切牙有14.70°的牙冠舌向移动。两种测量方法没有显著性差异。结论 用模型重叠的方法分析切牙的牙轴变化可以取得与头影测量一致的结果。?     

A comparison of two- and three-dimensional incisor angles

Two- and three-dimensional incisor angulations are compared in 40 patients using lateral radiographs and direct dental cast measurement using the Reflex Metrograph coupled to a computer. The two-dimensional upper and lower incisor angulations to the occlusal plane were also compared by the two methods. It was found that: The two-dimensional radiographic and three-dimensional dental cast inter-incisor angulation showed a significant difference at a probability level 0.01 greater than p greater than 0.001. The two-dimensional radiographic and two-dimensional dental cast upper left and right incisor angulations to the functional occlusal plane showed a significant difference at a probability level of 0.01 greater than p greater than 0.001. The significant differences can be attributed to the measurement of the incisor crown angulation in the dental cast measurement and the incisor tip and apex assessment in the radiographic technique. The system of dental cast measurement arguably provides a more realistic and reliable assessment of incisal angles than conventional radiographic measurement techniques.     

The position of the occlusal plane in dentulous subjects with various skeletal jaw-relationships

This study was conducted to examine the level and inclination of the occlusal plane in dentulous subjects with various skeletal jaw-relationships with the purpose of finding more reliable guides for locating the occlusal plane in edentulous patients. The investigation was carried out on 140 lateral cephalometric radiographs of young people with natural teeth in the intercuspal position. The sample was divided into three groups according to the skeletal relation of the jaws. The occlusal plane in this study and the two reference planes (maxillary and mandibular plane) were established according to the cephalometric criteria of Schwarz. On each radiograph both the angulation and the perpendicular distance of the occlusal plane to the reference planes were recorded and the values of the obtained data were subject to statistical analysis. The selected mean values of the angles and linear distances between the occlusal plane and reference planes calculated on the probability level of 95% could be used as cephalometric indicators for the locating or correcting the position of the occlusal plane in the prosthetic treatment of edentulous patients.     

Relationships between the upper central incisor crown forms and degree of labial inclination,overbite, and overjet in Japanese young adults

PURPOSEThe present study aimed to investigate the relationships between the crown form of the upper central incisor and their labial inclination, overbite, and overjet.MATERIALS AND METHODSMaxillary and mandibular casts of 169 healthy dentitions were subjected to 3D dental scanning, and analyzed using CAD software. The crown forms were divided into tapered, square, and ovoid based on the mesiodistal dimensions at 20% of the crown height to that at 40%. The degree of labial inclination of the upper central incisor was defined as the angle between the occlusal plane and the line connecting the incisal edge and tooth cervix. The incisal edges of the right upper and lower central incisor that in contact with lines parallel to the occlusal plane were used to determine the overbite and overjet. One-way ANOVA was performed to compare the labial inclination, overbite, and overjet among the crown forms.RESULTSThe crown forms were classified into three types; crown forms with a 20%/40% dimension ratio of 1.00±0.01 were defined as square, >1.01 as tapered, and <0.99 as ovoid. The labial inclination degree was the greatest in tapered and the least in square. Both overbite and overjet in tapered and ovoid were higher than those in square.CONCLUSIONUpper central incisor crown forms were related to their labial inclination, overbite, and overjet. It was suggested that the labial inclination, overbite, and overjet should be taken into consideration for the prosthetic treatment or restoring the front teeth crowns.     

Reproducibility of cephalometric measurements made by three radiology clinics

The purpose of this study was to assess reproducibility of cephalometric measurements in cephalograms obtained by three dentomaxillofacial radiology clinics. Forty lateral cephalometric radiographs were selected and sent at different times to three different clinics for cephalometric analyses. Each clinic digitized the radiographs with the same resolution, and landmarks were located with the mouse pointer directly on the digitized radiographic image on the screen. Three cephalograms were obtained from each radiograph, totaling 120 analyses. Data were analyzed with analysis of variance. Of the 32 factors studied, reproducibility of results was satisfactory for only four factors: position of maxilla relative to anterior cranial base, inclination of occlusal plane relative to anterior cranial base, position of lower incisor relative to nasion-pogonion line, and soft-tissue profile of face (P < .05). Differences in cephalometric measurements were present and such differences were significant for most factors analyzed. The different cephalometric measurements obtained by the three dental radiology clinics were not reproducible.     

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.     

Effects of single- or double-jaw surgery on vertical dimension in skeletal Class III patients

The vertical facial proportions resulting from bimaxillary surgery (maxillary advancement and mandibular setback) and mandibular setback alone were evaluated. The measurements were evaluated on the preoperative and postoperative cephalometric radiographs of 20 skeletal Class III patients. The results showed that sagittal correction of the jaws caused no change in the vertical relationship of the jaws. The only significant change was an increase in occlusal plane inclination in bimaxillary surgical patients.     

Bilateral congenital absence of maxillary lateral incisors: a craniofacial and dental cast analysis

The dental casts and cephalometric records of forty-three patients exhibiting bilateral congenital absence of maxillary lateral incisors were evaluated to determine the nature and extent of any concurrent craniofacial and dental anomalies. The effects of bilateral orthodontic space closure were evaluated on a subsample of twenty-two cases. The data revealed normal dental arch length, arch width, overjet, and overbite, while significant tooth size discrepancies were found in several anterior and posterior teeth. Craniofacial deviations from normal included smaller maxillary length, smaller mandibular length, smaller anterior cranial base, and nasal bone. Vertical facial dimensions, both anterior and posterior, were significantly less, as was the mandibular plane angle. Soft-tissue examination revealed a 10 degrees greater nasiolabial angle, which was increased a further 5 degrees as a result of a mean incisor retraction of 1.5 mm during space closure. The craniofacial anomalies noted in the present sample were similar to those seen in persons with clefts and may reflect a common etiology related to a developmental disturbance during fusion of the facial processes in utero. In the treatment of patients with bilateral congenital absence of maxillary incisors, mechanotherapy designed to open the mandibular plane, increase the vertical dimension, and move the maxillary posterior teeth forward is recommended in order to prevent worsening the Class III tendency and to minimize maxillary incisor and upper lip retraction. Most cases will require significant mesiodistal reduction in tooth size in order to achieve an optimal occlusion.     

成人骨性Ⅲ类错(牙合)下颌骨联合形态与下切牙位置的关系

目的了解成人严重骨性Ⅲ类错（牙合）患者下颌骨联合形态结构与下切牙位置的相关关系。方法选择需接受正颌手术的严重骨性Ⅲ类错（牙合）患者70人（ANB〈-3°）,男性37名,女性33名,年龄范围18—28岁。根据下颌平面角的大小将患者分为均角（43例）及高角（27例）二组。利用X线头影测量进行下颌骨联合形态结构与下切牙位置的相关分析。结果高角组较均角组下颌骨联合形态更高、更窄,高角组下切牙倾斜程度与下颌骨联合长轴的倾斜度有密切关系（r=0．78117）,而均角组下切牙倾斜程度与下颌骨联合牙槽骨长轴倾斜度有密切关系（r=0．81774）,同时下颌骨联合基骨唇侧骨板的舌倾角度在高角组较均角组有减小的趋势。结论治疗骨性Ⅲ类错（牙合）患者时需考虑下颌骨联合的形态,尤其高角病例由于下颌骨联合的形态较高较窄,提示我们去代偿或代偿性移动下切牙的范围可能要小。     

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.     

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.     

Evaluation of posttreatment changes in Class II Division 1 patients after nonextraction orthodontic treatment: cephalometric and model analysis.

BACKGROUND: The aim of this retrospective study was to evaluate changes in patients with Class II Division 1 malocclusions treated with cervical headgear and full fixed orthodontic appliances and without extractions. METHODS: Lateral cephalograms and dental casts of 18 patients were obtained at the beginning and the end of treatment and at the postretention period. Pretreatment records were taken at 11.9 +/- 2.6 years, and the mean treatment time was 2.8 +/- 1.2 years. All patients were asked to use maxillary and mandibular Hawley retainers for 1 year. The average postretention interval was 5.3 years. RESULTS: The assessment of cephalometric findings showed that maxillary growth was restricted; maxillary incisor inclination, overjet, and overbite were decreased; the mandibular incisors were proclined; and a slight mandibular posterior rotation occurred at the end of treatment. At the postretention period, the maxilla remained stable, the mandible moved anteriorly, and the overjet increased slightly (1.25 mm, P < .01). The dental cast changes indicated that both maxillary and mandibular irregularity index values decreased significantly during treatment but increased after 5 years. Mandibular intercanine width decreased 0.47 mm ( P < .01) during the postretention period. CONCLUSIONS: The redirection of maxillary growth remained stable in patients with Class II malocclusions treated with cervical headgear and fixed orthodontic appliances and without extractions, but treatment-induced mandibular rotations tended to return to their original patterns. Various dental changes occurred during the postretention period.     

Influence of saggital inclination of the teeth and the orientation of the occlusal plane on mesial drift in the dental arch

As a rule, the occlusal plane in man is not flat but curved in the three dimensions. This curved organization is related to a specific phenomena: the continuity of the dental arch without diastema. The Page's proposal of the tangent law explains the sagittal organization of the mandibular teeth by geometrical analyses. A cephalometric analysis of 485 subjects, in natural dentition, is the basis for the present statistical study of the mandibular teeth sagittal inclination, related to the direction of the tangent. Mandibular incisors follow the tangent law, but the long axis of the posterior mandibular teeth exhibits a postero-anterior and progressive differential angle with the direction of the tangent: 15 degrees, 20 degrees, 25 degrees, 28 degrees. The differential angle with the direction of vertical strength during closure movement generates an horizontal strength component, with a tendency to create a forward tooth movement. This horizontal component of force is tightening the proximal contacts, maintaining the continuity of the dental arch: it also originates the mesial "drift" and mandibular incisor crowding.     

Analysis of tooth movement in extraction cases using three-dimensional reverse engineering technology

Despite inherent errors, cephalometric superimpositions are currently the most widely used means for assessing sagittal and vertical tooth movements. The purpose of this study was to compare three-dimensional (3D) digital model superimposition with cephalometric superimposition. The material was collected from initial and final maxillary casts and lateral cephalometric radiographs of 30 patients (6 males, 24 females, mean age 17.7 years) who underwent orthodontic treatment with extraction of permanent teeth. Each pair of cephalograms was traced and superimposed according to Ricketts' four-step method. 3D scanning of the maxillary dental casts was performed using INUS dental scanning solution(R), which consists of a 3D scanner, an autoscan system, and 3D reverse modelling software. The 3D superimposition was carried out using the surface-to-surface matching (best-fit method) function of the autoscan system. The antero-posterior movement of the maxillary first molar and central incisor was evaluated cephalometrically and on 3D digital models. To determine whether any difference existed between the two measuring techniques, paired t-tests and correlation analysis were undertaken. The results revealed no statistical differences between the mean incisor and molar movements as assessed cephalometrically or by 3D model superimposition. These findings suggest that the 3D digital orthodontic model superimposition technique used in this study is clinically as reliable as cephalometric superimposition for assessing orthodontic tooth movements.