

ORIGINAL ARTICLE 

Year : 2016  Volume
: 50
 Issue : 1  Page : 2630 

An evaluation of YEN and W angle in the assessment of anteroposterior jaw relationship
Anushka Mittal^{1}, Sumit Bohra^{1}, PS Murali^{2}, K Saidath^{3}, US Krishnanayak^{4}
^{1} PG Student, Department of Orthodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India ^{2} Lecturer, Department of Orthodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India ^{3} Professor, Department of Orthodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India ^{4} Head of Department, Department of Orthodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India
Date of Submission  19Aug2015 
Date of Acceptance  13Jan2016 
Date of Web Publication  4Feb2016 
Correspondence Address: U S Krishnanayak Department of Orthodontics, A B Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore, Karnataka India
Source of Support: None, Conflict of Interest: None  Check 
DOI: 10.4103/03015742.175715
Objective: The objective of this study was to investigate two cephalometric variables: YEN angle and W angle in the assessment of sagittal jaw discrepancy. Materials and Methods: A sample of 75 subjects were categorized as Class I (Group I), II (Group II), and III (Group III) based on ANB angle, Beta angle, and Wits appraisal. The YEN angle and W angle were measured for each patient in all the three groups on a lateral cephalogram. ANOVA analysis, post hoc assessment, and correlation coefficient analysis were done. Results: Mean value of YEN angle for Class I, II, and III groups was 119.79 (±3.575), 112.08 (±6.606), and 128.67 (±4.63) degrees, respectively. Mean value of W angle for Class I, II, and III groups was 54.5 (±4.09), 47.5 (±6.679), and 55.33 (±6.041) degrees, respectively. The coefficient of variance was found to be least for YEN angle followed by the W angle. The ANOVA analysis revealed highly significant differences among the means of all the three Groups (Group I, Group II, and Group III) for YEN angle and between Group I and II for W angle. Post hoc assessment revealed that YEN angle significantly differentiated among the three groups whereas W angle failed to differentiate between Group I and Group III. Pearson's correlation test revealed that YEN angle and W angle were highly correlated. Conclusion: YEN angle with the least coefficient of variance was the most homogenously distributed parameter to assess the anteroposterior dysplasia. In addition, it could significantly differentiate among the three groups and was highly correlated to ANB, Wits, and W angle. Keywords: Lateral cephalograms, sagittal jaw discrepancy, W angle, YEN angle
How to cite this article: Mittal A, Bohra S, Murali P S, Saidath K, Krishnanayak U S. An evaluation of YEN and W angle in the assessment of anteroposterior jaw relationship. J Indian Orthod Soc 2016;50:2630 
How to cite this URL: Mittal A, Bohra S, Murali P S, Saidath K, Krishnanayak U S. An evaluation of YEN and W angle in the assessment of anteroposterior jaw relationship. J Indian Orthod Soc [serial online] 2016 [cited 2019 Jan 19];50:2630. Available from: http://www.jios.in/text.asp?2016/50/1/26/175715 
Introduction   
Cephalometry marked a beginning of a new era in the orthodontic diagnosis and treatment planning. ^{[1]} Many measurements were incorporated by various researchers to get an accurate method to assess skeletal base discrepancy. ^{[2]} Till date, various measurements have been developed such as AB plane angle, ANB angle, AXB angle, AXD angle, PABA angle, FABA angle, APDI angle, AB/TH angle, Beta angle, and linear measurements such as Wits appraisal, AB/PP distance, AB/SN distance, AD/SN distance, AB/FH distance, and AB/TH distance. ^{[3]} All these methods have their own merits and demerits.
Although the ANB angle is very popular and useful, there is often a difference between the interpretation of this angle and the actual discrepancy between the apical bases. Studies have shown that the position of nasion is not fixed during growth, and any displacement of nasion directly affects the ANB angle. ^{[4]}
A second widely used measurement, the Wits appraisal, was introduced by Jacobson to overcome problems related to the ANB angle. However, the Wits appraisal has its own shortcomings. First, accurate identification of the occlusal plane is not always easy or accurately reproducible, especially in mixed dentition patients or patients with open bite or missing teeth. ^{[5]} Second, any change in the angulation of the functional occlusal plane, caused by either normal development of the dentition or orthodontic intervention, can profoundly influence the Wits appraisal. ^{[6]}
Baik and Ververidou introduced the Beta angle to assess sagittal discrepancies. This angle depends on point A and point B, which are sometimes difficult to locate. In some situations, the condyle is not clearly visible. ^{[7]}
Thus, to overcome these difficulties, two new measurements named YEN angle and W angle were projected. ^{[7],[8]} So far, hardly any study has been done to assess the validity of YEN angle and W angle. Therefore, this study is aimed to compare YEN angle and W angle as anteroposterior dysplasia indicators.
Materials and Methods   
Standardized pretreatment lateral cephalogram of subjects visiting the department was obtained using the Planmeca PM 2002 cc proline (80 kV max/total filtration 2.5 mm Al) in a month and categorized based on their skeletal pattern group as Class I, Class II, and Class III. Since, a total of 25 Class III subjects were obtained in a month, the total sample size was selected to be 75, including 25 in each group. Inclusion criteria for the subjects were as follows:
Group I included subjects with:
 ANB angle between 1° and 3°
 Wits appraisal: male  1 mm, female  0 mm
 Beta angle between 27° and 35° [Figure 1]
 Profile with Class I appearance.
Group II included subjects with:
 ANB angle more than 4°
 Wits appraisal more than normal
 Beta angle <27°
 Profile with Class II appearance.
Group III included subjects with:
 ANB angle <2°
 Wits appraisal less than normal
 Beta angle >35°
 Profile with Class III appearance.
Lateral cephalograms were traced on to 0.003 inch acetate paper using 0.5 mm lead pencil under same illumination. All the tracings were performed by a single operator in a standardized manner to avoid errors due to inter operator variations. The YEN angle and W angle were measured for each patient in all three groups [Figure 2].
Three skeletal landmarks were marked:
 Midpoint of the sella turcica (point S).
 Midpoint of the premaxilla (point M).
 Center of the largest circle tangential to the internal inferior, anterior, and posterior surfaces of the mandibular symphysis (point G).
The angle that is formed by connecting point S, point M, and point G, measured at point M is the YEN angle [Figure 1]. Following this, a line was drawn from point M perpendicular to the SG line. The angle formed between the perpendicular line drawn from M to SG line and the MG line is the W angle [Figure 1].
Statistical analysis
The data were collected, tabulated, and statistically analyzed using ANOVA to determine whether there was a statistical significance among the mean values of YEN angle and W angle. Following this, the coefficients of variability and the correlation coefficients between the various parameters were calculated using Pearson's correlation test.
Results   
Mean value of YEN angle for Class I, II, and III groups was 119.79 (±3.575), 112.08 (±6.606), and 128.67 (±4.63) degrees, respectively. Mean value of W angle for Class I, II, and III groups was 54.5 (±4.09), 47.5 (±6.679), and 55.33 (±6.041) degrees, respectively. The coefficient of variance was least for YEN angle (0.071) followed by W angle (0.127) [Table 1].
The post hoc assessment found the Group I, Group II, and Group III to be significantly different for YEN angle, whereas it was found that W angle did not differentiate between Group I and Group III [Table 2].
Pearson's correlation analysis shows significant positive correlations between YEN angle and W angle (r = 0.735) and significantly negative correlations with ANB (−0.710) and Wits appraisal (−0.309) for Group I. In Group II, there was a significantly positive correlation between YEN angle and W angle (0.914) and significantly negative correlations with ANB (−0.418) and Wits appraisal (−0.609). In Group III, YEN angle showed a highly significant negative correlation with ANB (−0.873) and Wits appraisal (−0.593). In Group II, W angle showed a highly significant negative correlation with Wits appraisal (−0.472) whereas in Group III, it showed a significantly negative correlation with ANB angle (−0.546) [Table 3].
Discussion   
Till date, several angular and linear variables have been proposed to analyze the sagittal jaw relationship and jaw position cephalometrically. The literature exhibits a number of methods to assess the maxillamandibular jaw discrepancy, but none of them have proved to be universally acceptable. To overcome these difficulties, two new measurements, YEN angle and W angle, were projected. Therefore, the present study was designed to compare the YEN angle and W angle in the assessment of anteroposterior dysplasia. ^{[3]}
Lateral cephalometric radiographs were obtained from 75 subjects who had never undergone orthodontic treatment. Samples were divided into Class I, II, and III skeletal pattern groups (I, II, and III, respectively) with the help of cephalograms; based on ANB angle, the Wits appraisal, and the Beta angle.
From this present study, it was found that the value of YEN angle was significantly (P < 0.001) different in all the three skeletal pattern groups. The mean value for YEN angle in the skeletal Class I subject was 120.5 ± 2.9, for skeletal Class II was 114 ± 3.6, and for skeletal Class III was 129 ± 4.6 as stated by Neela et al. ^{[8]} The mean value recorded in the present study for skeletal Class I (119.79 ± 3.5), Class II (112.08 ± 6.6), and Class III (128.6 ± 4.6) was at par with the above study. YEN angle depends on stable points such as Smidpoint of sella turcica, Mmidpoint of premaxilla, and Gcenter of largest circle that is tangent to the internal inferior, anterior, and posterior surfaces of the mandibular symphysis and so it is not influenced by growth changes and can easily be used in mixed dentition. However, since it measures an angle between line SM and MG, rotation of jaw because of growth or orthodontic treatment can mask true basal dysplasia, similar to ANB angle. ^{[9]}
The mean value for W angle in skeletal Class I subject was 53 ± 2, for skeletal Class II was 48.9 ± 2.1, and for skeletal Class III was 58.7 ± 3.2 as stated by Bhad et al. ^{[7]} The mean value recorded in the present study for skeletal Class I (54.5 ± 4.09), Class II (47.5 ± 6.6), Class III (55.3 ± 6.04) was not in accordance with the above study.
According to post hoc analysis, the YEN angle differentiates significantly among the three groups, whereas the W angle fails to differentiate significantly (0.869) between skeletal Class I and Class III indicating that it is not a good determinant to differentiate between skeletal Class I and Class III malocclusion.
The results of this study show the difference in the coefficients of variability. The greatest coefficient of variability (CV) was observed for Wits appraisal (−4.125) and this may be partially due to difficulty in accurately determining the occlusal plane. ^{[9],[10],[11]} In addition, it can be easily influenced by the vertical dimensions of the jaws and the inclination of the occlusal plane. ^{[7]} Oktay reported more variation in the Wits appraisal than in the ANB angle. ^{[12]} YEN angle exhibited the lowest CV (CV = 0.071) in comparison to all other measurements indicating it to be more reliable compared to other parameters. This is also supported by Doshi et al. who found the high reliability and homogenecity of the YEN angle to assess anteroposterior sagittal discrepancy. ^{[3]} W angle had the second lowest CV (0.127) indicating that it was the second most homogeneously distributed parameter [Table 3].
The results of this study showed statistically significant correlation (P < 0.001) among the five sagittal parameters. However, the strength of association (correlation coefficient, r) varied between different pairs. A statistically significant negative correlation between ANB angle and YEN angle in all the three groups Group I (r = −0.710); Group II (r = −0.418); Group III (r = −0.873) was observed suggesting a strong correlation between YEN angle and ANB angle. A statistically significant negative correlation between Wits appraisal and YEN angle was observed in Group II (r = −0.609) and Group III (r = −0.593) suggesting a strong correlation between YEN angle and Wits appraisal. No significant correlation was observed between YEN angle and Beta angle in all the three groups and this could be attributed to the difficulty in the approximation of the center of condyle as stated by Baik and Ververidou. ^{[6]} A statistically significant positive correlation between YEN angle and W angle was observed in all the three groups suggesting a very strong correlation between the two angles. No significant correlation was found among W angle, ANB angle, and Wits appraisal for Group I whereas it was significantly negatively correlated with Wits appraisal (−0.472) in Group II and with ANB angle (−0.546) in Group III.
The results of this study indicate that YEN angle is more reliable and predictable in the assessment of anteroposterior dysplasia as it is highly correlated to ANB angle and Wits appraisal, which are the most commonly used parameters to assess the anteroposterior dysplasia.
Although till date, a number of skeletal dysplasia indicators have been introduced, none of the parameters are established to be a gold standard. Although a single study cannot validate the results, our study is a step in the direction to establish an angle which can be reliable enough to be used in daytoday clinical practice for diagnosis and treatment planning.
Conclusion   
The following conclusions can be drawn from the study:
 YEN angle with the least coefficient of variance was the most homogenously distributed parameter to assess the anteroposterior dysplasia
 YEN angle was the most reliable indicator in the assessment of anteroposterior dysplasia
 YEN angle could significantly differentiate among the three groups and was highly correlated to ANB, Wits appraisal, and W angle
 W angle is not a good determinant to differentiate between skeletal Class I and Class III malocclusion.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]
