Properties of the ANB angle and the Wits appraisal in the skeletal estimation of Angle's Class III patients

The aims of the present study were: (1) to investigate the statistical differences in jaw relationship assessments with the ANB angle and the Wits appraisal in Angle Class III children, and (2) to suggest guidelines for the use of these two parameters in this group of children. Seventy-five Angle Class I children with anterior crowding (male, 37; female, 38) and 96 Angle Class III children with anterior crossbite (male, 38; female, 58) were examined. All had undergone treatment that started at 8 or 9 years of age. Pre-treatment lateral cephalograms were used cross-sectionally for the analysis. The mean age was 8 years 7 months +/- 9 months in the Class I subjects, and 9 years 0 month +/- 7 months in the Class III subjects. To compare the assessments using ANB angle and the Wits appraisal in the Angle's Class III subjects, nine measured values from each individual subject were converted into Z scores in relation to the means and standard deviations of the two parameters in the Angle Class I subjects. The jaw discrepancy is assessed more severely using the ANB angle than by the Wits appraisal in these Angle Class III subjects. The paired t-test showed that the Z score of the ANB angle was significantly smaller than that of the Wits appraisal (P < 0.001). In Angle Class III subjects with a counter-clockwise mandibular rotation and a flattened occlusal plane, the ANB angle is a more critical cephalometric parameter than the Wits appraisal.     

ANB角与Wits值的关系

目的 揭示ANB角与Wits值的关系，探讨已知ANB能否准确预测Wits值，方法：研究选用100例（男女各50例）11－13岁Class I或Class II错He患者矫治前的头颅定位侧位片，患者均有较好骨生长型，I组：13例患者ANB小于等于1．5度，Wits值均为负：II组：61例5．8度大于ANB大于1．5度，Wits值或正或负；III组：26例ANB大于等于5．8度，Wits值均为正，借助计算机对各组进行统计分析。结果：分析发现无男女性别差异（P＞05），II组与III组ANB与Wits两值间有显著相关意义（P＜0．05），回归分析表明I组与II组有统计学意义（P＜0．05），我们在II组可以预测Wits值，准确率为21％，结论 ：尽管许多测量分析数据有统计学意义，但无显著的临床意义。     

Craniofacial features of patients with Class III abnormalities: growth-related changes and effects of short-term and long-term chincup therapy.

The craniofacial features of patients with Class III abnormalities, including growth-related changes and effects of short-term and long-term chincup therapy, were studied. Twenty female subjects were treated with chincups and an orthopedic force of 500 g for 31 months (short-term treatment group). Another 36 female patients were treated with chincups and a force of 250 to 300 g for 86 months (long-term treatment group). All subjects treated with chincups had lateral cephalograms taken before treatment (T0), after treatment (T1), and at retention (T2). Cross-sectional lateral films of 562 skeletal Class III girls were selected from the records of 1265 Class III patients at a public hospital and private clinics as controls. The controls were selected to approximately match the ANB angle, Wits appraisal, and chronological age of the treated groups. Short-term treatment resulted in a slight improvement in ANB angle and Wits appraisal, while long-term treatment resulted in a significant improvement in ANB angle and Wits appraisal. Such treatment also resulted in a significant inhibition of the growth of the ramus (2.2 mm) and body length (3.6 mm) of the mandible, a backward rotation of the mandible, and a reduction (8.2 degrees ) of the gonial angle. However, there was no alteration of any parameter of the maxilla and the cranial base, except the length of S-N and N-S-Ar in the long-term treatment group. Subjects who completed the long-term treatment protocol retained the changes by wearing the appliance during sleep, with a force of 200 g applied to the center of the chin.     

四种上下颌骨矢状位置关系评估方法的比较

目的:比较ANB角、Wits值、AFBF值和APDI四种方法评估上下颌骨矢状位置关系的稳定性及相关性。方法:随机选择50例错牙合畸形病例正畸治疗前的X线头颅侧位定位片,同时测量其ANB角、Wits值、AFBF值和APDI,测量结果进行相关性及变异度分析。结果:APDI的变异系数最小,Wits值变异系数最大;四值之间均存在相关性,以ANB角与AFBF值相关性最强。结论:每种评估方法影响因素不同,宜采用综合分析。     

Seven parameters describing anteroposterior jaw relationships: Postpubertal prediction accuracy and interchangeability

Seven parameters describing anteroposterior jaw relationships (the A-B plane angle, the angle of convexity, the ANB angle, the SN-AB angle, the Wits appraisal, the AF-BF distance, the APDI) were measured on pairs of prepubertal and postpubertal cephalograms of 44 normal occlusion subjects (20 males and 24 females). The mean ages at prepubertal and postpubertal stages were 10 years 5 months and 14 years 5 months in males and 8 years 10 months and 12 years 10 months in females, respectively. The purpose of this study was to compare prediction accuracy of future relationships by regression analysis and to evaluate interchangeability among the 7 parameters by correlation analysis. In the prepubertal assessment, the ANB angle and the angle of convexity showed better prediction accuracy for postpubertal jaw relationships. Higher interchangeability among the parameters was statistically substantiated between the SN-AB angle and the AF-BF distance, as well as among the ANB angle, the angle of convexity, and the A-B plane angle. The Wits appraisal and the APDI were less interchangeable with other parameters. The ANB angle, the Wits appraisal, and the APDI would complement each other for the geometrically distorting factors because of the low interchangeability due to their different geometric basis. The conjunctive use of the ANB angle, the Wits appraisal, and the APDI is recommended as a clinically appropriate method for assessment of jaw relationships in individuals.     

Study between anb angle and wits appraisal in cone beam computed tomography (cbct)

Objectives: To analyse the ANB and Wits values and to study correlations between those two measurements and other measurements in diagnosing the anteroposterior maxilo-mandibular relationship with CBCT. Study Design: Ninety patients who had previously a CBCT (i-CAT®) as a diagnostic register were selected. A 3D cephalometry was designed using one software package, InVivo5®. This cephalometry included 3 planes of reference, 3 angle measurements and 1 linear measurement. The means and standard deviations of the mean of each measurement were assessed. After that, a Pearson´s correlation coefficient has been performed to analyse the significance of each relationship. Results: When classifying the sample according to the anteroposterior relationship, the values obtained of ANB (Class I: 53%; Class II: 37%; Class III: 10%) and Wits (Class I: 35%; Class II: 56%; Class III: 9%) did not coincide, except for the Class III group. However, of the patients classified differently (Class I and Class II patients) by ANB and Wits, a high percentage of individuals (n=22; 49%), had a mesofacial pattern with a mandibular plane angle within normal values. A correlation has been found between ANB and Wits (r=0,262), occlusal plane angle and ANB (r=0,426), and mandibular plane angle and Wits (r=0,242). No correlation was found between either Wits or ANB in relation with the age of the individuals. Conclusions: ANB and Wits must be included in 3D cephalometric analyses as both are necessary to undertake a more accurate diagnosis of the maxillo-mandibular relationship of the patients. Key words:Cone beam computed tomography, ANB, Wits, cephalometrics.     

颅底重叠法Wits值的评价

目的 探讨颅底重叠法测量Ｅｉｔｓ值与常规Ｗｔｉｓ值测量法对评价治疗前后颌骨矢状关系改变的可靠性。方法 样本为４８例经过正畸治疗的错卧倒患者的头颅侧位片，用计算机数字化仪测量法分别测量常规Ｗｉｔｓ值、颅底重叠法Ｗｉｔｓ值及ＡＮＢ角在治疗前后的变化，用ＳＡＳ软件包对３者间的相关笥进行统计分析。结果 重叠法Ｗｉｔｓ值与ＡＮＢ角之间的相关笥明显高于常规Ｗｉｔｓ值，相关系数高达０．８４９，差异具有高度显著性     

Relation of the Wits appraisal to the ANB angle: a statistical appraisal

The hypothesis that the relationship between the ANB angle and the Wits appraisal can be expressed by measuring the individual variations in their reference systems and by constructing a model of regression between them and a few parameters describing the reference systems was tested with material consisting of 30 lateral cephalometric radiographs of untreated orthodontic patients with different types of skeletal and/or dentoalveolar malocclusions. The results indicated that approximately 93% of the variation of the Wits appraisal could be explained by the variation of the ANB, NSL/OL, and SNA angles. The study also showed that the results given by different measurements with different reference systems, such as the ANB angle and the Wits appraisal, cannot be directly compared. To obtain comparable interpretations, one should correct the results of both measurements in relation to the variations in their reference systems.     

Clinical application of a method to correct angle ANB for geometric effects

Angle ANB does not provide an adequate assessment of the skeletal discrepancy between the jaws in the sagittal plane. Attempts have been made to avoid the fallacies with the introduction of quadrilateral and Wits analyses. Based on the Wits appraisal of zero, Hussels and Nanda (1984) were able to evaluate and eliminate four geometric factors that affect angle ANB. These four factors are (1) anteroposterior position of point N in relation to points A and B, (2) inclination of the occlusal plane, (3) dental height (a linear measurement between point A and B), and (4) distance between points N and B. The authors derived a mathematic formula to evaluate the influence of all four parameters in terms of angle ANB. This formula reflects the skeletal relationship of a patient when points A and B are on a perpendicular plane in relation to the occlusal plane (Wits = 0 mm). The authors define this to be a Class I skeletal relationship. A comparison of the measured ANB angle with the calculated angle ANB gives a better perspective of the skeletal discrepancy. If the measured angle ANB is larger than the calculated angle, the discrepancy is Class II. On the other hand, if the measured angle ANB is smaller than the calculated angle, the skeletal relation is Class III. This method of assessing the skeletal sagittal position of the jaws in relation to each other was applied to 508 patients. The authors showed that the geometric influence of the four factors indeed conceals the true skeletal relations when angle ANB is used without any correction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of functional versus bisected occlusal planes on the Wits appraisal

Lateral cephalometric radiographs of 35 males between the ages of 11 years and 24 years, all of whom had Class II, Division 1 malocclusions, were traced and Wits appraisals were completed with the use of two occlusal planes: the functional occlusal plane and the bisected occlusal plane. These two values were then statistically related to two dental parameters (overjet and incisor angulation [1 to 1]) and one skeletal parameter (angle ANB) by means of the Pearson product-moment correlation with a predetermined level of statistical significance at p less than 0.05. The findings demonstrated that Wits values for both occlusal planes were significantly correlated to both skeletal and dental parameters. Each Wits value also shared variance with the Wits value for the other occlusal plane. Both Wits measures seem to vary to the same degree when compared to the other measures, as demonstrated by the r values. From the results of this experiment, three conclusions can be drawn: (1) either occlusal plane can be used in the calculation of the Wits appraisal to aid in the diagnosis of the severity or degree of anteroposterior jaw disharmony, (2) the bisected occlusal plane Wits appraisal value showed a higher relationship to dental measures than the functional occlusal plane Wits appraisal value, and (3) the functional occlusal plane Wits value shared slightly more variance with skeletal measures.     

The use of linear and angular measurements of maxillo-mandibular anteroposterior discrepancies

A new reference plane where the anteroposterior discrepancy between maxilla and mandible could be measured, namely the bisector of the palatal plane to mandibular plane angle, has recently been proposed. The aims of the present investigation were to extend the assessment of the clinical significance of this measurement to a large group of randomly selected patients of both sexes, and to verify the correlation of this measurement to well-established angular and linear assessments of anteroposterior discrepancy. On the pretreatment lateral cephalograms of 306 orthodontic patients (165 males, 141 females) aged between 6 and 50 years, the following measurements were obtained: ANB angle; corrected ANB* angle (computed as: ANB* = original ANB angle + 0.5 × (81.5°-SNA angle) + 0.25 × (32°-SN-GoMe angle), which compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits: linear distance between the projections of A and B points on the bisector of the palatal plane to mandibular plane angle. The MM-Wits distance was significantly correlated to two angles (ANB and ANB*), as well as with the Wits appraisal. All the correlations performed did not show sex- or age-characteristic patterns. The correlation to the corrected ANB* was the best among the three, with a correlation coefficient of 0.915, MM-Wits (mm) = 1.497 × ANB* (degrees) ?6.784. From the correlation, reference values for the new measurement have also been estimated, and found to be between ?0.65 and ?6.85 mm for skeletal Class I individuals. Nevertheless, it is recommended that the diagnosis of orthodontic anomalies should be performed taking into consideration more than a single anteroposterior appraisal.     

安氏Ⅱ类1分类错(牙合)上下颌基骨前后关系诊断指标的可靠性评价

目的评价反映安氏Ⅱ类1分类错（牙合）上下颌基骨前后关系13项指标的可靠性。方法安氏Ⅱ类1分类错（牙合）患者120例,男60例,女60例,年龄20-28岁。拍摄自然头位（NHP）下的头颅定位侧位片。一金属链悬于头颅前方,其在胶片上的影像作为确定真性水平面（THP）的依据。X线头影测量项目包括ANB角、AB平面角、Wits值、AF—BF、AXB平面角、AB／SN4、AB／PP、AXD平面角、AD／SN、SGrdAB角、APDI角、FABA角、B角及A、B两点在THP上垂足间的距离（AB／HP）。计算各测量项目的相关系数：测量结果按最小相关系数指标分类法行聚类分析。所有测量结果用SPSS11．0统计软件进行分析。结果相关分析表明各项指标除Wits值和SGrdAB角外多数呈高度相关性：聚类分析采用最小相关系数指标分类,结果按0．60水准分为5类。结论在安氏Ⅱ类1分类错（牙合）患者中,除Wits和SG11／AB外其他11项指标均可作为上下颌基骨前后关系的评价指标。AB／SN。能比较真实地反映上下颌骨的矢状关系：ANB角、AB平面角、β角、AF—BF、AXB平面角、FABA角、AB／PP、APDI角等指标具有相似的临床意义。     

Longitudinal cephalometric changes in the maxilla, mandible and maxillary-mandibular relationship between 10 and 14 years of age

In the present study, longitudinal growth changes in the maxilla, mandible, and maxillary-mandibular relationship occurring between the ages of 10 and 14 years were evaluated in 19 female and 15 male subjects. All subjects had a clinically-acceptable occlusion, a normal growth pattern, and none had undergone orthodontic treatment. Serial cephalometric radiographs were taken at the ages of 10, 11, 12, and 14 years. The effects of age and sex on the sagittal growth of the jaws were studied by means of variance analysis. The results show that A-Ptm, B-Ptm, Pg-Ptm, A'-Ptm, B'-Ptm, and S-N-Pg measurements were affected by age, and the measurements A-Ptm, A'-Ptm, Wits and ANB by sex. Duncan's multiple range test was applied to those measurements where F values were found to be statistically significant. As a result, it was observed that the greatest growth changes occurred between 12 and 14 years old.     

安氏Ⅱ类1分类错上下颌基骨前后关系诊断指标的可靠性评价

目的 评价反映安氏Ⅱ类1分类错上下颌基骨前后关系13项指标的可靠性。方法 安氏Ⅱ类1分类错患者120例，男60例，女60例，年龄20-28岁。拍摄自然头位（NHP）下的头颅定位侧位片。一金属链悬于头颅前方，其在胶片上的影像作为确定真性水平面（THP）的依据。X线头影测量项目包括ANB角、AB平面角、Wits值、AF-BF、AXB平面角、AB/SN4、AB/PP、AXD平面角、AD/SN、SGn/AB角、APDI角、FABA角、β角及A、B两点在THP上垂足间的距离（AB/HP）。计算各测量项目的相关系数；测量结果按最小相关系数指标分类法行聚类分析。所有测量结果用SPSS11.0统计软件进行分析。结果 相关分析表明各项指标除Wits值和SGn/AB角外多数呈高度相关性；聚类分析采用最小相关系数指标分类，结果按0.60水准分为5类。结论 在安氏Ⅱ类1分类错患者中，除Wits和SGn/AB外其他11项指标均可作为上下颌基骨前后关系的评价指标。AB/SN4能比较真实地反映上下颌骨的矢状关系；ANB角、AB平面角、β角、AF-BF、AXB平面角、FABA角、AB/PP、APDI角等指标具有相似的临床意义。     

Overjet as a predictor of sagittal skeletal relationships

Skeletal relationships in the sagittal plane do not always correspond with dental relationships. The aim of this study was to determine in which type of malocclusion the correlation between overjet and skeletal sagittal parameters assessed by lateral cephalogram analysis is the highest. The extent to which overjet can predict skeletal relationships in the sagittal plane was also assessed. Eighty-three subjects fulfilled the inclusion criteria (40 males and 43 females, mean age 16.3 +/- 4.3 years). Overjet was measured on study casts and sagittal skeletal relationships were analysed on lateral cephalograms. ANB angle, Wits appraisal, and convexity at point A were determined. Mean values and standard deviations of measured parameters were calculated for Class I, Class II division 1, and Class III malocclusion subjects. Correlation between overjet measured on study casts and sagittal skeletal parameters measured on lateral cephalogram was calculated. Overjet as a predictor of skeletal relationships was assessed by means of linear regression analysis. A statistically significant positive correlation (P < 0.01) was found between the values of overjet and ANB (r = 0.690), overjet and Wits appraisal (r = 0.750), and overjet and convexity at point A (r = 0.608) when assessing the whole sample. When linear regression between overjet and cephalometric parameters was assessed separately in Class I, Class II division 1, and Class III malocclusion subjects, the percentage of variability was statistically significant in just four pairs. The findings show that overjet is a good predictor of sagittal relationship only in subjects with a Class II division 1 malocclusion.     

Age-related changes in sagittal relationship between the maxilla and mandible

The aim of the study was to assess age-related changes in sagittal jaw relationship during pre-pubertal and pubertal development on the basis of angular [ANB, anteroposterior dysplasia indicator (APDI) and A-B plane angle] and linear (Wits, AF-BF, App-Bpp, and App-Pgpp) measurements. Lateral cephalograms of orthodontically untreated subjects were evaluated at 7, 9, 11, 13 and 15 years of age. Cephalometric standards and age-related changes were determined on the basis of Class I subjects with a good occlusion (n = 18, 10 males and 8 females). With respect to changes related to growth, the main findings were, in both genders, a statistically significant age-related decrease in ANB angle, App-Bpp and App-Pgpp, a significant increase in APDI, but no age-related change in Wits. A reduction of sagittal jaw distance during pre-pubertal and pubertal development was observed arising from a relative dominance of sagittal mandibular growth. For an evaluation of differences concerning jaw relationship in Class II subjects, a group with Class II division 1 malocclusions (n = 17) and a group with Class II division 2 malocclusions (n = 12 were compared with two control groups, i.e. the good occlusion group and a Class I group (n = 37). Conclusions about the sagittal discrepancy in Class II division 1 and Class II division 2 subjects depended on the geometric reference used in the various parameters, and further research is called for with respect to the diagnostic performance of the various measurements. Differences between Class II subjects and controls present at 15 years of age were already established at 7 years of age, but were less pronounced.     

The use of linear and angular measurements of maxillo-mandibular anteroposterior discrepancies.

OBJECTIVES: To extend the assessment of the clinical significance of the measurement of the anteroposterior discrepancy between maxilla and mandible on the bisector of the palatal plane to mandibular plane angle to a large group of randomly selected patients of both sexes, and to verify the correlation of this measurement to well established angular and linear assessments of anteroposterior discrepancy. DESIGN: Retrospective analysis of pre-treatment lateral cephalometric radiographs. SETTING AND SAMPLE POPULATION: The Laboratory of Functional Anatomy of the Stomatognathic Apparatus at Milan University, Italy. Three hundred and six orthodontic patients (165 males, 141 females) aged between 6 and 50 years. EXPERIMENTAL VARIABLE: ANB angle; corrected ANB* angle which compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits: linear distance between the projections of A and B points on the bisector of the palatal plane to mandibular plane angle. RESULTS: The MM-Wits distance was significantly correlated to two angles (ANB and ANB*), as well as to the Wits appraisal. All the correlations performed did not show sex- or age-characteristic patterns. The correlation to the corrected ANB* was the best among the three, with a correlation coefficient of 0.915, MM-Wits (mm) = 1.497 x ANB* (degrees) -6.784. From the correlation, reference values for the new measurement have also been estimated, and found to be between -0.65 and -6.85 mm for skeletal Class I individuals. CONCLUSION: It is recommended that the diagnosis of orthodontic anomalies should be performed taking into consideration more than a single anteroposterior appraisal.     

Beta角评价前牙反患者颌骨矢状关系的准确性分析

目的探讨Beta角判断替牙期与恒牙期前牙反[牙合]患者颅面矢状关系的可靠程度。方法应用X线头颅定位侧位片,比较替牙期与恒牙期前牙反[牙合]患者的Beta角、ANB角、Wits值和APDI指数的差异,并进行相关性和变异程度分析。结果替牙期与恒牙期前牙反[牙合]患者Beta角间差异有统计学意义（P〈0．05）;Beta角与ANB角、Wits值和APDI指数显著相关（P〈0．05）,但变异较ANB角和Wits值小,与APDI指数接近。结论Beta角可准确评价前牙反[牙合]患者的颌骨矢状关系。     

Cephalometric and in vivo measurements of maxillomandibular anteroposterior discrepancies: a preliminary regression study

One of the aims of the present investigation was to assess three-dimensionally the anteroposterior discrepancy of dental bases using a noninvasive direct procedure. A second aim was to verify the relationship of three-dimensional soft-tissue measurement to the well-established two-dimensional cephalometric assessments of anteroposterior discrepancy. Dental and facial landmarks were directly digitized on 20 orthodontic and maxillofacial surgery patients aged 8 to 26 years using an electromagnetic three-dimensional computerized digitizer. The anteroposterior maxillomandibular discrepancy was measured by calculating the linear distances between the projections of subnasal and sublabial landmarks on the occlusal plane, subnasal and sublabial landmarks on Camper's plane, and insertion of maxillary and mandibular median labial frenula on the occlusal plane. From lateral cephalograms of the same patients, the following measurements were obtained: subspinale point-nasion-supramentale point (ANB) angle; corrected ANB angle that compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits, linear distance between the projections of points A and B on the bisector of the palatal plane to mandibular plane angle; and soft-tissue Wits, linear distance between the projections of soft-tissue points A and B on the bisecting occlusal plane. The best two-dimensional vs three-dimensional linear regression (r = 0.91) was found between Wits appraisal and the linear distances between the projections of maxillary and mandibular median labial frenula on the occlusal plane (Wits = -1.05 x 3D measurement - 3.75). The three-dimensional evaluation of the sagittal discrepancy of the jaws directly performed in vivo may allow a more complete analysis of a patient's soft-tissue drape together with the underlying hard-tissue structure.     

153例错畸形患者W角的测量分析研究

目的:本研究使用一种新的头影测量方法-W角评价上下颌骨矢状向关系,据此分析安氏3种错类型W值。方法:对153例11～20岁患者头颅侧位片进行头影测量分析,按照ANB角、Wits值和β角分为3组,取平均值和标准差,分析男女差异。结果:分析安氏3种错类型患者W角的正常值;3组W值间差异有统计学意义(P<0.05);各组W值在性别上没有显著差异。结论:W角能反映上下颌骨矢状方向不调,具有较好可重复性。