|Year : 2015 | Volume
| Issue : 3 | Page : 165-169
Establishment of cephalometric norms for four sagittal skeletal discrepancy indicators in Andhra population
Venkata S Polina1, Adusumilli S Prakash1, Sudhakar Paturi2, Bhaskar Mummidi2, Praveen K Varma2, B Shyam Kumar1
1 Department of Orthodontics, Sibar Institute of Dental Sciences, Takkellapadu, Guntur, Andhra Pradesh, India
2 Department of Orthodontics, Vishnu Dental College, Vishnupur, Andhra Pradesh, India
|Date of Web Publication||15-Sep-2015|
Venkata S Polina
Senior Lecturer in Department of Orthodontics, Malla Reddy Institute of Dental Sciences, Quthbullapur Municipality, R.R. Dist., Hyderabad - 500 055
Source of Support: Nil., Conflict of Interest: None declared.
Background: In orthodontic diagnosis assessment of sagittal skeletal discrepancy has greater importance and it aids in treatment planning.
Aim: To establish cephalometric norms for sagittal dysplasia using four parameters WITS, ANB, Beta and YEN in Andhra population.
Materials and Methods: Sample consisted of 90 pretreatment conventional lateral cephalograms and WITS, ANB, Beta, YEN were measured. Statistical analysis included mean, standard deviation, reciever operative characteristic (ROC) analysis.
Results: ROC analysis shows range for WITS: −3 mm to +2.5 mm; ANB: 0° to 4.5°; Beta: 27° to 37° and YEN: 120° to 127°.
Conclusion: Subjects with straight profile and class I occlusion showed higher range of values for all the four parameters. These values can be considered while assessing sagittal skeletal discrepancies which help in better orthodontic diagnosis and treatment plan of subjects residing in Andhra.
Keywords: Beta angle, ROC analysis, sagittal dysplasia indicators, YEN angle
|How to cite this article:|
Polina VS, Prakash AS, Paturi S, Mummidi B, Varma PK, Kumar B S. Establishment of cephalometric norms for four sagittal skeletal discrepancy indicators in Andhra population. J NTR Univ Health Sci 2015;4:165-9
|How to cite this URL:|
Polina VS, Prakash AS, Paturi S, Mummidi B, Varma PK, Kumar B S. Establishment of cephalometric norms for four sagittal skeletal discrepancy indicators in Andhra population. J NTR Univ Health Sci [serial online] 2015 [cited 2020 Mar 28];4:165-9. Available from: http://www.jdrntruhs.org/text.asp?2015/4/3/165/165404
| Introduction|| |
The anteroposterior relation of mandible to maxilla is an important diagnostic criterion. It can be determined from clinical observation to some degree, but accurate evaluation was not possible. Introduction of cephalometrics offered a possibility to evaluate sagittal apical base relationship more accurately.
Cephalometrically Riedel's ANB angle is widely used in evaluating anteroposterior apical base relationship., But reliability of ANB as a true indicator of sagittal jaw relationship has been questioned., ANB angle can vary because of variances in the length or rotation of the cranial base and/or rotation of the jaws during growth.,,
Hence, to eliminate the influence of the anatomic variations in the spatial position of nasion on the sagittal relationship of the jaws, numerous angular and linear measurements have been described. These include AXB , AXD , APDI , Wits appraisal, i.e., AO — BO , AF-BF  for the assessment of sagittal dysplasia but all these have various shortcomings.
In 2004, Baik and Ververidou  established Beta angle making use of three skeletal landmarks point A, point B, and center of condyle. An advantage of Beta angle is that it does not depend on the cranial landmarks and remains stable even when jaws are rotated. But points A and B are affected by remodeling changes during growth and are influenced by treatment. In 2009, Neela et al., established YEN angle based on the landmarks S, M  and G  as described in [Table 1].
The aim of present study was to establish cephalometric norms for Wits, ANB, and new angles such as Beta, YEN in Andhra populations.
| Materials and Methods|| |
The study sample consisted of 90 subjects of Andhra population with in a range of 17-25years of age. Sample grouped based on the clinical profile and dental occlusion into three groups class I, class II, class III and each consisted of 30 subjects. Inclusion criteria for selection of subjects were bilateral facial symmetry, presence of all permanent teeth excluding third molars in all the three groups. Exclusion criteria were subjects with craniofacial anomalies or with history of orthodontics.
Lateral cephalograms were taken in natural head position obtained when relaxed individuals looked into their own eyes in a mirror and inclined their heads up and down in increasingly smaller movements until they felt comfortably placed. X-ray machine used was X-Mind panoceph, Satelec, manufactured in Finland.
Each cephalogram was manually traced and following land marks were identified [Table 1]. Four parameters WITS, ANB, Beta, YEN were measured [Figure 1], [Figure 2], [Figure 3], [Figure 4].
|Figure 1: Perpendiculars from point A and point B to OP are represented as AO and BO respectively, linear distance between them measured as Wits appraisal|
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|Figure 2: From point Nasion, two planes drawn to point A and point B. Angle ANB measured between those two planes at Nasion|
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|Figure 3: A line connecting condylion C with B point (CB line) and another line connecting A and B points (AB line) are drawn. A perpendicular drawn from point A to the C-B line. Beta angle formed by perpendicular to AB line is measured|
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|Figure 4: A plane is drawn from S to point M and another plane drawn from point M to point G. YEN angle is the inner angle formed at point M by above-mentioned two planes measured|
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| Results|| |
Statistical analysis included mean, standard deviation, reciever operative characteristic (ROC) analysis. [Table 2] shows the mean WITS, ANB, Beta, and YEN values for all the three classes. ROC analysis shows that WITS value of less than or equal to 2.5 has 83.3% sensitivity and 83.3% specificity for discriminating class II from class I. WITS value greater than or equal to −3 has 100% sensitivity and 100% specificity for discriminating class III from class I. Range for WITS in class I group is −3 mm to +2.5 mm.
|Table 2: Mean and Standard Deviation of Wits, Anb, Beta and Yen in Three Groups|
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ANB value of less than or equal to 4.5° has 80% sensitivity and 83.3% specificity for discriminating class II from class I. ANB value of greater than or equal to 0.075° has 100% sensitivity and 96.7% specificity for discriminating class III from class I. Range for ANB in class I group is 0° to 4.5°.
Beta value of more than or equal to 27.5° has 83.3% sensitivity and 83.3% specificity for discriminating class II from class I. Beta value of less than or equal to 37° has 96.7% sensitivity and 100% specificity for discriminating class III from class I. Range for Beta in class I group is 27.5° to 37°.
YEN value of less than or equal to 120.5° has 86.7% sensitivity and 76.7% specificity for discriminating class II from class I [Figure 5]. YEN value of greater than or equal to 127.5° has 90% sensitivity and 96.7% specificity for discriminating class III from class I [Figure 6]. Range for YEN in class I group 120° to 127°.
|Figure 5: ROC analysis of YEN for discriminating class II from class I. Area under the curve is 0.893 with P < 0.001; Highly significant|
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|Figure 6: ROC analysis of YEN for discriminating class II from class I. Area under curve is 0.968 with P < 0.001; Highly significant|
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| Discussion|| |
There are numerous angular and linear measurements to assess the maxilla-mandibular sagittal discrepancy, which is of prime importance in diagnosis and treatment planning. Among all these measurements, ANB and WITS are commonly used even though they have shortcomings.
The mean WITS, ANB, Beta, and YEN value in each class differs significantly from the other classes. The mean WITS value in class I is 0.767 with an SD of 1.552. The mean for WITS in the present study is close to the WITS values measured by Järvinen  −0.6 mm ± 2.9, Jacobson  1.07 ± 1.77, Robertson and Pearson  0.30± 1.9, Richardson  −0.32 ± 2.81. ROC curves showed a cut off value for WITS −3 mm between class II and class I, +2.5 mm between class III and class I. In Andhra population WITS value for class I group can range from −3 mm to +2.5 mm.
The mean for angle ANB in class I group is 3° with an SD of 1.63° and it is quite close to ANB mean values of Riedel  3.4°, Bhatia and Akpabio  3.5° ± 2.3° and Richardson  2.32°± 1.92°, Järvinen  2.9°± 2.4°. But Walker and Kowalski  mean ANB values of 4.5° were high compared with present study mean values. ROC curves showed a cut off value for ANB 4.5° between class II and class I, 0.07° between class III and class I. In Andhra population ANB value for class I group can range from 0° to 4.5°.
The mean for angle Beta in class I is 30.23° with an SD of 3.30°. ROC curves showed a cut off value for Beta 27.5° between class II and class I, between class III and class I 37°. In Andhra population Beta value for class I group can range from 27° to 37°. It is almost close to Baik and Ververidou  mean Beta angle values 31.1° ± 2.0° with a range from 27° to 35°.
The mean YEN angle values in class I is 122.63° with an SD of 2.95° slightly higher than mean YEN values of Neela et al study  120.5° ± 2.9°. ROC curves showed a cut off value 120.5° between class II and class I, 127.5° between class I and class III. In Andhra population YEN value for class I group can range from 120° to 127°, where as in Neela et al study YEN value for class I group has a range from 117° to 123°.
The ANB angle is influenced by variations in the horizontal or vertical position of nasion and Taylor's study indicated that nasion was moving away from sella approximately 1 mm per year. Because of these inherent problems ANB could often be a poor reflection of actual apical base relationship.
Although the WITS appraisal avoids nasion point and reduces the rotational effects of jaw growth, it uses the occlusal plane, a dental parameter to describe a skeletal maxillo-mandibular relation. Cant of the occlusal plane affected by tooth eruption and dental development. Any change in angulation of occlusal plane profoundly influences the positions of A, B and thereby Wits appraisal reading.,
In contrast to ANB angle, Beta angle does not depend on cranial landmarks and remains stable even when jaws are rotated, as C-B line is rotated in the same direction of jaw rotation carrying the perpendiculars from point A with it. Tracing the condyle and locating its center is difficult.
Research has overwhelming evidence that points A and B are affected by remodeling changes during growth and are influenced by treatment., Hence there is need for a technique that will eliminate or reduce the inaccuracies in the presently used landmarks.
Difficulties in location of the point A and point B which are common to WITS, ANB, Beta could affect either methods equally. Hard tissue land marks used for YEN angle (Sella, constructed Points M, G) represent the true nature of underlying skeletal pattern and are less affected by remodeling changes during orthodontic treatment.
YEN may be preferable to Beta in analysis of sagittal maxillo-mandibular relationship as there is ease in locating the landmarks. It is possible that YEN can be affected by jaw rotation as it depends on cranial landmark. This aspect is not studied in the present research and needs to be evaluated in further studies.
| Conclusion|| |
In the view of the findings of the present study the following conclusions are drawn.
- In Andhra population, subjects with straight profile and class I occlusion show higher range of values for all the four parameters; WITS: −3 mm to +2.5 mm; ANB: 0° to 4.5°; Beta: 27° to 37° and YEN: 120° to 127°.
- The present study results can be considered in orthodontic diagnosis and treatment planning of subjects residing in Andhra.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2]