Journal of Orthodontics & Endodontics

Keywords

Sagittal discrepancy; Antero-posterior jaw relationship; Cephalometric parameters

Introduction

In orthodontics, sagittal discrepancies are more frequently confronted in day to day practice. The first jaw based relationship assessment on the first permanent molars was provided by Angle. A new era of orthodontics began after the introduction of Broadbent’s cephalometer [1]. After Wylie’s descrfibed effort to define anteroposterior jaw relationship, several other cephalometric parameters have been proposed [2]. Downs’s A-B plane angle used positive and negative signs to signify retrusion and protrusion of mandible [3]. Riedel introduced ANB angle, and it became the most regularly used measurement [4]. However,these methods are subjected to error as any displacement of nasion point, will directly affect them [3,4]. Later, to eliminate cranial reference points and to reduce the rotational effects of jaw growth; Jacobson used the occlusal plane as a reference, named it as the Wits appraisal. But he described skeletal discrepancies using dental parameter [5]. Thus, these two most commonly used measurements have flaws.

Readings were not affected by the facial degree measure angle of divergence, as he also eliminated point N Chang employed a linear measurement for the perpendiculars distance from points A and B onto the FH plane [7,8]. Yang and Suhr also used the FH plane by drawing a perpendicular from point A [6,7,9]. Studies have reported that the Frankfurt plane is not a true horizontal. Still, it remains to be the most commonly used plane for facial typing. Nanda and Merrill, used the palatal plane as a reference based and suggested angles and linear measurements. After a decade, the Beta angle was proposed by Baik and Ververidou [8- 11]. Here, the problem lies with point A, as it is considered to be changed by alveolar bone remodelling; and the point condylion and its reproducibility. Proposed the sagittal dysplasia measure indicator, known as YEN angle [12].

Proposed W angle as a modification of YEN angle with a benefit of remaining relatively stable on jaws rotation or its vertical growth. The parameter named Pi angle also defies ease of application but does not seem to offer significant advantages [13].

The literature revealed several angular measurements and linear measurements to define the sagittal skeletal discrepancy such as AXD, JYD, MM bisector, FABA, Beta angles, AF-BF and App-Bpp, but none has been authenticated universally [14]. Therefore, it's essential for the orthodontist to understand, merits and demerits of each parameter. In the absence of clear indications of these parameters, the conjunctive use of different parameters is recommended. The purpose of our study was to evaluate different methods for assessing skeletal class I, class II and class III relationships in the sagittal plane with twenty-two parameters, comprising of thirteen angular and nine linear measurements and to determine the level of agreement between them [15-17]. The study was focused on their reliability and variability with the interchangeability or the redundancy in assessing the AP jaw relationship for young adults of North India population.

Materials and Methods

The material of this retrospective study is based on existed diagnostic records of patients visited between 2011-2013 to the Department of Orthodontics and Dentofacial Orthopedics, M. M. College of Dental Sciences and Research, Mullana, Haryana, India. The retrieved records from the archives of the Department of Orthodontics were good quality and evaluated anonymously, therefore, no requirement existed for ethical approval [18]. The pre-treatment Lateral Cephalogram of a minimum of 100 patients, both male and female were taken [19]. The pre- treatment radiograph selected as patients of 11-25 years age group; patients with permanent dentition only; no impacted or missing teeth except for third molars; no craniofacial deformity or asymmetry; no excess soft tissue (to avoid the interference with the identification of cephalometric points); and no previous orthodontic treatment record [20].

All the lateral cephalometric radiographs were taken using the same digital cephalometer. Manual tracings were performed on clear acetate placed over the digitally printed cephalometric film. All the tracings and measurements were performed by the same investigator. The sample of 100 pre-treatment lateral cephalograms was divided into three groups as skeletal class I, class II and class III based on ANB and Wits appraisal; with a minimum of 15 lateral cephalograms in each group [21]. Male and female were considered separately. Subsequently, angles and linear measurements were measured. The coefficient of variability was calculated between all the measurements of sagittal maxilla-mandibular jaw relationships, and thus, their accuracy and interchangeability were assessed [22].

Statistical analysis

The data was collected and tabulated using spreadsheet software. SPSS 21 software was used for statistical analysis. Ten radiographs were randomly selected to determine radiographic measurements errors. Paired ‘t’ test was used for comparing the repeated measurements with the first one [23]. Appropriate statistical methods were employed to calculate minimum/ maximum values, range, mean ± SD. Independent ‘t’ test was applied, to find the differences between males and females. Pearson’s coefficient was used to determine the level of correlation among all parameters.

Results

The mean age was 16.5 years (class I, n=38), 16.2 years (class II, n=43) and 21.2 years (class III, n=19) of 100 patients. Of all, 51 patients were male. Both showed no statistically significant differences (p>0.05). Range, mean, Standard Deviation (SD), and Coefficient of Variability (CV) were tabulated (Table 1).

Table 1: Range, mean, Standard Deviation (SD), and Coefficient of Variability (CV).

The assessment of sagittal jaw relationship by thirteen angular and nine linear parameters; and measurement of agreement with ANB angle and Wits appraisal (on BOP) were tabulated among all three groups (Table 2). All the angular measurements are statistically significant with ANB angle. YEN angle (n=41) showed the highest frequency in Class III malocclusion cases, and; S-Gn/AB angle (n=65) showed the highest frequency in Class II malocclusion cases [24].

Table 2: Measurement of agreement with ANB angle and Wits appraisal (on BOP) were tabulated among all three groups.

The coefficients of variability (Table 1) and correlation matrixes (Table 3) of all parameters were calculated in all three groups. According to these coefficients, YEN (CV=4.94, 4.74 and 3.01) and FABA (CV=4.58, 4.88 and 7.50) angles were the most homogenous distributed; least homogenous was the Wits appraisal, in all three groups. ANB angle had statistically significant positive correlation with JYD angle (r=0.502, 0.499 and 0.766; p<0.01) and AXD angle (r=0.556, 0.572 and 0.631; p<0.01) in all three groups, (Table 4); whereas Wits appraisal on BOP had correlation with Wits appraisal on FOP (r=0.812, 0.969, 0.984; p<0.01) and MM bisector (r=0.348, 0.729, 0.718) and App-Bpp distance (r=0.339, 0.588, 0.745). The positive correlation was quite strong between A’B’ distance and AXD angle (r=0.794, 0.804, 0.677; p<0.01); negative correlation was strong between AFB angle and FABA angle [r=(-0.734), (-0.805) and (-0.617); p<0.01] and; FABA and AF-BF distance [r=(-0.788), (-0.847) and (-0.716); p<0.01] among all three groups (Table 5).

Table 3: Correlation matrixes in class I group.

Table 4: Correlation matrixes in class II group

Table 5: Correlation matrixes in class III group.

Discussion

Orthodontic diagnosis and treatment planning provided great significance to the maxilla-mandibular relationship evaluation [25]. The most popular parameters, ANB angle and Wits appraisal, are affected by numerous factors and can often be inaccurate. Still, they are in use for an absolute determination for assessing sagittal skeletal disharmony. Methods for geometric correction in both parameters had been proposed to eliminate these distorting effects [26]. In cephalometrics, both angular and linear variables should be used simultaneously, as individually they are erroneous. Linear measurement has a distinct advantage over angular measurement because fewer variables can affect their accuracy [27,28].

A’-B’ distance is a linear measurement, introduced by Taylor, to establish few degree changes in ANB angle accomplished through the linear measurements [18]. Approximately 1 mm per degree of change was noted in this study, whereas the actual values ranging from 0.7 mm per degree to 0.8 mm per degree. Taylor also stated that nasion is moving away from Sella approximately 1 mm per year [29]. Therefore, an alternative to ANB angle, AXD angle was devised [19]. In this study, the AXD angle’s mean value accuracy (12.0°) was relatively close to the pre-treatment mean (12.7°) reported in the original study for Class II malocclusion. He also used A’-D' distance as a linear measurement to eliminate the inter-individual variation due to the effect of anterior cranial base length and anterior facial height, arising in assessing AXD angle [30]. AXD angle also showed a statistically significant positive correlation with ANB angle in all the three groups; and strong correlation especially with JYD angle and A’-B’ distance, which was in agreement [31].

Brought JYD angle, which showed a statistically assessing AXD's significant strong positive correlation with ANB angle, AXD angle and A'-D' distance. This might be due to the use of SN plane as a reference plane in all the above three parameters. The rotation of the jaws can influence these parameters, whereas actual anterior face height can affect AXD and JYD angles. The JYD angle usually increases with steepening of the mandibular plane angle [32]. Though, PABA (palatal plane to AB plane) or APDI (Anteroposterior Dysplasia Indicator) angle was introduced by Kim and Vietas as a combination of the facial angle, A-B plane angle and palatal plane angle; but this geometric summation is less liable for interchangeability [22,33]. The mean value for Class II malocclusion group was 74.45° for APDI angles; in agreement with the earlier study. APDI was the most homogenously distributed parameter and showed a strong correlation with ANB angle and Wits appraisal in all groups, which was further supported by Oktay and Yang Suhr [23,34].

Ift was recommended the conjunctive use of APDI with ANB angle and Wits appraisal. Also, due to their different geometric basis, these three parameters would complement each other, especially in geometrically distorting figures as they have low interchangeability [35,36].

Yang Suhr introduced a parameter on FH plane fthaft named FABA; which showed highest negative statistically significant correlation with AFB angle and AF-BF distance means, the smaller the FABA, larger the AF-BF distance and AFB angle values and vice-versa; similar to the results of Doshi et al. [24,37]. Therefore, showed a good interchangeability with FABA angle and AF-BF distance, this result was in par with results of Gul and Fida’s study [25,38]. Since, FH plane is known for its uncertainty of accurately locating porion in cephalometrics; natural head position had been used as reference plane due to its high reproducibility. We had also studied dependability on three different sagittal reference planes, and the results indicated that Wits appraisal on MM Bisector was less correlated with ANB angle; unlike correlation studies done [28]. MM bisector’s normal occlusion measurement mean values were numerically dissimilar with Jacobson’s original values [39]. The most homogenously distributed parameter, Maxillo-mandibular differential is a subtractive result of effective midfacial length and effective mandibular length. This analysis is very suitable in myofunctional therapy. In contrast, S-Gn/AB angle did not show any overlap between values in different classes [40].

AF-BF distance also did not take into account point A and B vertical relationship, which seems to affect anteroposterior jaw dysplasia as well as the facial profile. Its mean values were higher when compared with Chang’s AF-BF values, unlike the study, done by Judy et al. where the AF-BF values were lower [31,41]. also proved that AF-BF distance showed.

The highest correlation coefficient with App-Bpp distance; but, a statistically significant correlation with SN-AB angle, unlike earlier study. App-Bpp linear distance was averaged as 4.8 mm ± 6.9 mm 6.6 ± 4.5 mm in Indian males and females, respectively. Though the palatal plane is stable, but its inclination remains highly variable with age, thus it’s difficult to gain mean values around the norms. But, App-Bpp distance was positively correlated with Wits appraisal and ANB angle, similar to the previous study [42].

Similar to study on Indian population, the mean measurements value for Beta angle were 30.49° ± 8.7°; having a high standard deviation, thus conveyed more severe malocclusion among Indian population [33]. Positive correlation results of Beta angle with AB plane angle, FABA and APDI angles, were also dictated [43].

Comparisons throughout orthodontic treatments and during the planning of orthognathic surgery. It helps in deciding between orthodontic camouflage and surgery; but not in determining which jaw is prognathic or retrognathic. In this study, YEN angle was found to be homogenously distributed, similar to the study [44]. It showed a statistically significant positive angle has been correlation only with the W angle. In W angle’s geometry, a perpendicular from point M on S-G line rotates along with jaw rotation, thus recommended parameter in a clockwise or counterclockwise rotation. Many studies had already proved the reliability and validity of these angles in different populations. Still, the mean values of these angles were found to be higher when compared with the study [45]. Another linear measurement parameter, dentoskeletal overjet depends on dentoalveolar compensation and overjet. However, for skeletal discrepancy overjet didn’t found to be a good predictor in the sagittal plane, but it acted as a significant predictor in Class II division 1 malocclusion subjects. also compared these angles were with Pi analysis and predicted their corrections.

The quadrilateral analysis being individualised, and not dependent on established norms, would be an excellent tool in cases with underlying skeletal discrepancies. In orthodontics, conventional cephalometrics is incapable of delineating shape and size as it relies on linear and angular measurements [46]. Therefore, there is a requirement for a better comparative method w.r.t biological variability. Therefore, Procrustes analysis can be used for direct comparison of patient’s tracing to the size and position corrected template. Due to the large variability in the human population, a single cephalometric analysis may not provide an accurate diagnosis. Moreover, cephalometrics is not an exact diagnostic tool and analysis, which are based on angular and linear parameters, have evident limitations. Hence, it is imperative that a clinician be aware of a range of cephalometric analysis to be used appropriately as the need arises. Again, the best solution would be to apply at least three analysis in each case [47]. Thorough knowledge of the various analysis at hand will help the astute clinician in choosing the most appropriate ones for each case. Predictability and variability of each parameter must be considered when assessing individuals' skeletal discrepancy. For standardising norms, further investigation must be conducted in different populations for assessing different parameters of the sagittal discrepancy. Further reliability, validity and correlation studies are required to evaluate latest developed parameters like E analysis, SAR angle and HBN angle for assessing sagittal maxilla- mandibular jaw relationships in different populations.

Conclusion

Despite numerous cephalometric sagittal dysplasia indicators, ANB angle remains the most widely used due to its simplicity and global acceptability. However, total reliability on ANB angle cannot be recommended. The Wits appraisal of jaw disharmony is also popular. Being a linear parameter dependent on the occlusal plane, again has obvious limitations. Many studies have been published in comparisons, but none exit on comparing thirteen angular and nine linear parameters altogether. The present study concluded that: Among the angular parameters, the YEN angle was found to be homogenously distributed as well as highly reliable. High interchangeability among FABA angle and AF-BF distance due to their strongest correlation. The conjunctive use APDI with ANB angle and the Wits appraisal is recommended for assessing AP jaw relationship.

Conflict of Interest

None.

Funding Sources

None.

References

1. Broadbent BH (1931) A new x-ray technique and its application to orthodontia. Angle Orthod 1: 45-66.

   [Crossref][Google Scholar]

2. Wylie WL (1947) The assessment of anteroposterior dysplasia. Angle Orthod 17: 97-109.

   [Crossref][Google Scholar]

3. Downs WB (1949) Variations in facial relationship: Their significance in treatment and Prognosis1. Angle Orthod 19: 145-155.

   [Crossref][Google Scholar]

4. Riedel RA (1952) The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod 22: 142-145.

   [Crossref][Google Scholar]

5. Jacobson A (1975) The “Wits” appraisal of jaw disharmony. Am J Orthod 67: 125-138.

   [Crossref][Google Scholar][Pubmed]

6. Rushton R, Cohen AM, Linney AD (1991) The relationship and reproducibility of angle ANB and the Wits appraisal. Br J Orthod 18: 225-231.

   [Crossref][Google Scholar][Pubmed]

7. Freeman RS (1981) Adjusting ANB angles to reflect the effect of maxillary position. Angle Orthod 51: 162-171.

   [Crossref][Google Scholar][Pubmed]

8. Chang HP (1987) Assessment of anteroposterior jaw relationship. Am J Orthod Dentofac Orthop 92: 117-122.

   [Crossref][Google Scholar]

9. Yang SD, Suhr CH (1995) FH to AB plane angle (FABA) for assessment of anteroposterior jaw relationships. Angle Orthod 65: 223-231.

   [Crossref][Google Scholar][Pubmed]

10. Nanda RS, Merill RM (1994) Cephalometric assessment of sagittal relationship between maxilla and mandible. Am J Orthod Dentofac Orthop 105: 328-344.

    [Crossref][Google Scholar][Pubmed]

11. Baik CY, Ververidou M (2004) A new approach of assessing sagittal discrepancies: The Beta angle. Am J Orthod Dentofac Orthop 126: 100-105.

    [Crossref][Google Scholar][Pubmed]

12. Neela PK, Mascarenhas R, Husain A (2009) A new sagittal dysplasia indicator: The YEN angle. World J Orthod 10: 147-151.

    [Google Scholar][Pubmed]

13. Bhad WA, Nayak S, Doshi UH (2013) A new approach of assessing sagittal dysplasia: The W angle. Euro J Orthod 35: 66-70.

    [Crossref][Google Scholar][Pubmed]

14. Kumar S, Valiathan A, Gautam P, Chakravarthy K, Jayaswal P (2012) An evaluation of the Pi analysis in the assessment of anteroposterior jaw relationship. J Orthod 39: 262-269.

    [Crossref][Google Scholar][Pubmed]

15. Haynes S, Chau MN (1995) The reproducibility and repeatability of the Wits analysis. Am J Orthod Dentofac Orthop 107: 640-647.

    [Crossref][Google Scholar][Pubmed]

16. Hussels W, Nanda RS (1987) Clinical application of a method to correct angle ANB for geometric effects. Am J Orthod Dentofac Orthop 92: 506-510.

    [Crossref][Google Scholar]

17. Williams S, Leighton BC, Nielsen JH (1985) Linear evaluation of the development of sagittal jaw relationship. Am J Orthod 88: 235-241.

    [Crossref][Google Scholar][Pubmed]

18. Taylor CM (1969) Changes in the relationship of nasion, point A, and point B and the effect upon ANB. Am J Orthod 56: 143-163.

    [Crossref][Google Scholar][Pubmed]

19. Beatty EJ (1975) A modified technique for evaluating apical base relationships. Am J Orthod 68: 303-315.

    [Crossref][Google Scholar][Pubmed]

20. Jarvinen S (1981) A comparison of two angular and two linear measurements used to establish sagittal apical base relationship. Euro J Orthod 3: 131-134.

    [Crossref][Google Scholar][Pubmed]

21. Jarvinen S (1982) The JYD angle: A modified method of establishing sagittal apical base relationship. Euro J Orthod 4: 243-250.

    [Crossref][Google Scholar][Pubmed]

22. Kim YH, Vietas JJ (1978) Anteroposterior dysplasia indicator: An adjunct to cephalometric differential diagnosis. Am J Orthod 73: 619-633.

    [Crossref][Google Scholar][Pubmed]

23. Oktay H (1991) A comparison of ANB, Wits, AF-BF, and APdI measurements. Am J Orthod Dentofac Orthop 99: 122-128.

    [Crossref][Google Scholar][Pubmed]

24. Doshi JR, Trivedi K, Shyagali T (2012) Predictability of yen angle and appraisal of various cephalometric parameters in the assessment of sagittal relationship between maxilla and mandible in angle’s class II malocclusion. Peoples J Sci Res 5: 1-8.

    [Google Scholar]

25. Fida M (2008) A comparison of cephalometric analyses for assessing sagittal jaw relationship. J Coll Physicians Surg Pak 18: 679.

    [Google Scholar][Pubmed]

26. Singh AK, Ganeshkar SV, Mehrotra P, Bhagchandani J (2013) Comparison of different parameters for recording sagittal maxillo mandibular relation using natural head posture: A cephalometric study. J Orthod Sci 2: 16.

    [Crossref][Google Scholar][Pubmed]

27. Antony PJ, Puthalath MS, Chacko T, George A, Kurian B, et al. (2014) A new method for assessment of sagittal dysplasia-E analysis. J Indian Orthod Soc 48: 454-460.

    [Google Scholar]

28. Foley TF, Stirling DL, Hall-Scott J (1997) The reliability of three sagittal reference planes in the assessment of Class II treatment. Am J Orthod Dentofac Orthop 112: 320-329.

    [Crossref][Google Scholar][Pubmed]

29. McNamara Jr JA (1984) A method of cephalometric evaluation. Am J Orthod 86: 449-469.

    [Crossref][Google Scholar][Pubmed]

30. Sarhan OA (1990) A new cephalometric parameter to aid in dental base relationship analysis. Angle Orthod 60: 59-64.

    [Crossref][Google Scholar][Pubmed]

31. Judy DL, Farman AG, Silveira AM, Yancey JM, Regennitter FJ, et al. (1995) Longitudinal predictability of AF-BF value in Angle Class I patients. Angle Orthod 65: 359-366.

    [Crossref][Google Scholar][Pubmed]

32. Ishikawa H, Nakamura S, Iwasaki H, Kitazawa S (2000) Seven parameters describing anteroposterior jaw relationships: postpubertal prediction accuracy and interchangeability. Am J Orthod Dentofac Orthop 117: 714-720.

    [Crossref][Google Scholar][Pubmed]

33. Dhinahar S, Dilipkumar D, Suresh P, Tandon A, Pereira A (2017) Accuracy of beta angle in assessment of sagittal skeletal discrepancy in Chennai population-A cephalometric study. J Pierre Fauchard Acad 31: 43-46.

    [Google Scholar]

34. Alam MK, Qamruddin I, Basri R, Begum S, Sikder MA, et al. (2016) Assessment of sagittal discrepancies in Bangladeshi adults: Latest and old approaches. Int Med J 23: 411-413.

    [Google Scholar]

35. Qamaruddin I, Alam MK, Shahid F, Tanveer S, Umer M, et al. (2018) Comparison of popular sagittal cephalometric analyses for validity and reliability. Saudi Dent J 30: 43-46.

    [Crossref][Google Scholar][Pubmed]

36. Potode NB, Bajaj TD, Verulkar AA, Wankhade SB, Lohakpure RA, et al. (2018) Norms for anterior-posterior assessment of jaw relationship in Maharashtra population. Int J Orthod Rehabil 9: 141.

    [Google Scholar]

37. Agarwal R, Sharma L, Soni VK, Yadav V, Soni S, et al. (2013) Comparison of different angular measurements to assess sagittal Jaw discrepancy in Jaipur population-A cephalometric study. IOSR J Dent Med Sci 10: 33-36.

    [Google Scholar]

38. Prasad M, Reddy KPK, Talapaneni AK, Chaitanya N, Reddy MVB, et al. (2013) Establishment of norms of the beta angle to assess the sagittal discrepancy for Nellore district population. J Nat Sci Biol Med 4: 409.

    [Crossref][Google Scholar][Pubmed]

39. Alam MK, Qamruddin I, Muraoka R, Nakano K, Okafuji N (2014) Validity of W Angle and YEN Angle in a sample from Pakistani and Bangladeshi populations. J Hard Tissue Biol 23: 351-356.

    [Crossref][Google Scholar]

40. Aparna P, Kumar D, Prasad M, Shamnur N, Kumar A, et al. (2015) Comparative assessment of sagittal skeletal discrepancy: A cephalometric study. J Clin Diagn Res 9: ZC38.

    [Crossref][Google Scholar][Pubmed]

41. Iwasaki H, Ishikawa H, Chowdhury L, Nakamura S, Iida J (2002) Properties of the ANB angle and the Wits appraisal in the skeletal estimation of Angle's Class III patients. Eur J Orthod 24: 477-483.

    [Crossref][Google Scholar][Pubmed]

42. Zupancic S, Pohar M, Farcnik F, Ovsenik M (2008) Overjet as a predictor of sagittal skeletal relationships. Eur J Orthod 30: 269-273.

    [Crossref][Google Scholar][Pubmed]

43. Bohra S, Udeshi PS, Sinha SP, Saidath K, Shetty KP, et al. (2018) Predictability of pi angle and comparison with ANB angle, W angle, Yen angle, and beta angle in South Indian population. J Indian Orthod Soc 52: 22-28.

    [Google Scholar]

44. Di Paolo RJ, Philip C, Maganzini AL, Hirce JD (1983) The quadrilateral analysis: An individualized skeletal assessment. Am J Orthod 83: 19-32.

    [Crossref][Google Scholar][Pubmed]

45. Wellens H (2009) Improving the concordance between various anteroposterior cephalometric measurements using Procrustes analysis. Eur J Orthod 31: 503-515.

    [Crossref][Google Scholar]

46. Agarwal S, Bhagchandani J, Mehrotra P, Kapoor S, Jaiswal RK (2014) The SAR angle: A contemorary Sagital jaw dysplasia marker. Orthod J Nepal 4: 16-20.

    [Crossref][Google Scholar]

47. Kirchner J, Williams S (1993) A comparison of five different methods for describing sagittal jaw relationship. Br J Orthod 20: 13-17.

    [Crossref][Google Scholar][Pubmed]