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Orthodontics Original Article OVERJET AS A PREDICTOR OF SAGITTAL SKELETAL RELATIONSHIPS GHULAM RASOOL 2 NAYAB HASSAN 3 SUMMIYA BASHIR 4 ANEELA NAUSHEEN 5 UMAR HUSSAIN 1 ABSTRACT Skeletal relationships in the sagittal plane do not always correspond with dental relationships. The aim of the study was to evaluate the degree of correlation between a dental parameter (overjet) and a skeletal (ANB) angle. Eighty nine patients fulfilled the inclusion criteria for the study ( 22 males and 69 females, aged 1235). Overjet was measured on casts with a standard ruler. Lateral cephalograph was taken to measure the ANB angle. The correlation analysis of overjet with ANB angle in the three malocclusion classes showed, that there was a weak correlation of overjet with ANB angle in all three groups of malocclusion with “r” value of 0.257 whereas P value was statistical insignificance (P-value > 0.05). This study concluded that overjet is not a good predictor for sagittal skeletal relationship and therefore could not be used for better assessment of sagittal jaw relation which is critical in orthodontic diagnosis and treatment planning. Key Words: Overjet, ANB angle, sagittal skeletal malocclusion. INTRODUCTION Correct orthodontic diagnosis requires history of the patient, thorough examination and certain diagnostic tools e.g model, radiographic analysis and photographs.1-3 The aim of Clinical examination is to establish the type and severity of malocclusion and to determine the skeletal or dental origin of the problem. It also helps to determine what diagnostic records might be needed.3,4 OJ is an important linear parameter that can be measured clinically and is used to assess the sagittal relationship of upper and lower dental arches. OJ could be due to skeletal, dental, or a combination of both.5 It is generally accepted that increased OJ is due to a growth deficit of the lower jaw or increase of upper jaw rather than poor positioning of the dental elements but no significant data regarding this has been published as yet.6 Ghulam Rasool, Professor and Principal Khyber College of Dentistry, Peshawar 2-5 Nayab Hassan, Summiya Bashir, Aneela Nausheen, Umar Hussain, Residents Orthodontics FCPS II Email: [email protected] Cell: 0321-9117048 Received for Publication: June 29, 2016 Revised: August 6, 2016 Accepted: August 8, 2016 1 At completion of growth, when deciding on surgical or orthodontic intervention, beside the facial profile, OJ is also an important guideline. Generally when the OJ is greater than 10 mm, surgery is a more successful treatment option.5 Cephalometric analysis is an important part of diagnosis in orthodontics, allowing changes associated with growth and orthodontic treatment to be observed. To diagnose and classify a malocclusion, the measured values of cephalometric parameters are compared with standard values. A large number of cephalometric standards have been developed for adult populations and for children in the period of growth and development.7 For accurate measurement of sagittal skeletal relationship, the ANB angle and the Wits appraisal have been considered as the most common cephalometric.5,8 ANB measurement is commonly used to determine sagittal skeletal relationship in routine. It indicates the magnitude of the skeletal jaw discrepancy and is, in a normal well proportionate face, from 10 to 40.9 However ANB angle has certain limitations; with change in the anteroposterior and vertical position of nasion, increased or decreased vertical height of the face10, tipping of SN plane ANB can give incorrect value Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016) 395 Overjet as a predictor of sagittal skeletal relationships .There is variation in ANB angle between patient’s centric occlusion and centric relation.11 Various authors have shown that these angular measurements are geometrically sensitive and can give false measurement8, soother linear measurement like witts and OJ should be investigated for sagittal evaluation. The rationale of this study was to determine whether the sagittal skeletal evaluation through a non-invasive parameter of OJ rather than through cephalometry and to find out whether the previous study performed is applicable in our population or not. If ANB could coincide with the OJ; then this method could be considered as a substitution in cases where radiographic facility is not available, patient not fit for radiation or unaffordable. METHODOLOGY This cross-sectional study was carried out in the orthodontic department of Khyber College of Dentistry. Eighty nine patients were recruited, out of which 36 were males and 53 were females. Approval from the Ethics Committee was sought and written consent were taken from all the participants. The age range was 12 to 35 years. The inclusion criteria included subjects with permanent dentition. Patients having any asymmetry of jaws, absent or supernumerary teeth, previous extraction of any tooth or patients with past history of orthodontic treatment were excluded from the study. The molar relationship was assessed according to the mesiobuccal cusp of the upper first permanent molar. • Class I: When the mesiobuccal cusp of permanent upper first molar occluds in the mesio-buccal of the permanent lower first molar. • Class II: When the mesiobuccal cusp of permanent upper first molar occluds mesial to the mesio-buccal groove of the permanent lower first molar. • Class III: When the mesiobuccal cusp of permanent upper firstmolar occludes distal to the mesio-buccal groove of the permanent lower first molar. OJ was measured on the study casts with a standard ruler as the horizontal overlap of the most prominent incisor, with cast in occlusion distance from the labial surface of lower central incisor to the incisal edge of the most prominent upper central incisor was recorded. The lateral cephalograms were taken under standard conditions. The film – focus distance from the median planeof the patient’s head was 150 cm, and the median plane – film distance 10 cm. The cephalograms were taken with the subjects standing and the head positioned in the cephalostat and orientated to the Frankfort horizontal plane with the teeth in maximum intercuspation. All measurements were made by the same investigator. On cephalograph, the ANB angle was measured by drawing two lines from nasion to point A called as NA line and other line from nasion to point B called as NB line. Angle formed between these two lines was taken as ANB angle. The data were analyzed using SPSS version 19.0. Mean and standard deviation for numerical variable likes OJand ANBwere calculated. Pearson correlation test was used to relationships between OJ and ANB. P < 0.05 was consideredto be significant. RESULTS A total of 83 subjects, 36 (40.4%) males and 53 (59.6%) females) were included in the study. Male to female ratio was 1: 0.64. The most common age group was second decade. (Table 1). There is very low correlation between ANB and OJ (r =0.257) and co-efficient of determination (r2= 0.066). Only 6.6% skeletal cases of malocclusion OJ can be for ANB. There is no statistically significant correlation between ANB and OJ. (Table 2) TABLE 1: AGE DISTRIBUTION Age group (in years) Frequency Percentage 11-20 68 76.22 21-30 19 21.44 35 2 2.34 Total 89 100.0 TABLE 2: CORRELATIONAL ANALYSIS BETWEEN ANB AND OJ r* r2 Std. Error of the Estimate 0.257 0.066 3.63775 *Pearson correlation test TABLE3 : CORRELATION BETWEEN ANB AND OJ USING LINEAR REGRESSION EQUATION Model Sum of Squares df Mean Square F Sig. 81.493 1 81.493 6.158 0.015a Residual 1151.288 87 13.233 Total 1232.781 88 Regression a. Predictors: (Constant), ANB b. Dependent Variable: OJ Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016) 396 Overjet as a predictor of sagittal skeletal relationships TABLE 4: COMPARISON BETWEEN ANB AND OJ Pair Mean N Std. Deviation Std. Error Mean Overjet 4.0899 89 3.74284 .39674 ANB 4.5618 89 4.29840 .45563 a. Significant level = P<0.005 TABLE 5: PAIRED t TEST STATISTICS OF COMPARISON BETWEEN ANB AND OJ Paired Differences Mean Std. Deviation Std. Error Mean -.47191 4.92060 .52158 95% Confidence Interval of the Difference Lower Upper T Df Sig. (2 tailed) -1.50845 .56462 -.905 88 .368 Table 3 shows the regression model of ANB and OJ which is statistically significant; OJ is predictor of ANB but correlation is very weak. Table 4 and 5 shows that the difference between OJ and ANB is not statistically significant (p=.640) which denotes similarity in ANB and OJ. DISCUSSION Among the factors which must be evaluated to formulate a correct diagnosis and a suitable treatment plan, the antero-posterior relationship between the maxilla and mandible is a particularly important parameter.12,13 Correction of sagittal discrepency is very important in achieving balanced profile after orthodontic treatment. Various methods (ANB, Witts, OJ, etc) used to measure the antero-posterior relationship of maxilla to mandible.14-17 As proposed by the ABO (American Board of Orthodontist), OJ, in association with other parameters such as overbite, IMPA, presence of open bite or crossbite, or entity of crowding, is a useful indicator in evaluation of the diagnostic complexity.18 The aim of this study was to evaluate by what degree a dental parameter i.e OJ which is measured clinically is able to predict the entity of the skeletal parameter ANB. Therefore, within individual classes of malocclusion, according to Angle’s classification, the average values of these parameters were calculated and their correlations tested the extent to which OJ can determine skeletal relationships in the sagittal plane. OJ is an important measurement in cast analysis. It has been one of the parameters used to investigate the sagittal relationship of the upper and lower dental arch. The cause of an increased or negative OJ could be skeletal, dental, or a combination of both. At completion of growth, when deciding on orthodontic or surgical intervention, in addition to the facial profile, OJ is an important guideline. Generally when the OJ is greater than 10mm, surgery is a more indicated treatment.2,5 The current study, showed that there was weak correlation between OJ and ANB with r=0.257. This was probably due to the fact that OJ is influenced by the inclination of the upper and lower incisors, while ANB is less affected. However, ANB also varies according to the anteroposterior position of the nasion, the inclination of the SN plane, and the inclination of the jaws.19 Another factor able to modify the width of ANB, even if the relationship between the jaws remains constant, is the inclination of the Occlusal plane.20 In a previously conducted study by Iwasaki et al21 similar results as in current study were observed. They found that OJ is not always a reliable measure of the jaw relationship in the sagittal plane, especially in subjects with Class III malocclusions Another study carried out by Zupancic et al5 showed the same results. This study findings demonstrated that for Class I and Class III malocclusions OJ is not a good predictor of skeletal relationships in the sagittal plane. However, according to their study, in Class II division 1 malocclusion subjects, OJ is a statistically significant predictor.5 Similar results were found in a study by Jabbar et al3 they observed weak correlation between OJ and ANB angle in all three malocclusion groups but found that it is statistically significant only in class III malocclusion.3 CONCLUSION The findings of this study demonstrate that OJ is not a good predictor of malocclusion (Class I, Class II & Class III) for skeletal relationships in the sagittal plane. REFERENCES 1 Lombardo L, Sgarbanti C, Guarneri A, Siciliani G. Evaluating the correlation between OJ and skeletal parameters using. Int J Dent. 2012; 921942: 1-7. 2 Proffit WRJ, Ackerman L. Contemporary Orthodontics. Mosby, St. Louis, Mo, USA, 3rd edi 2000.pp. 145-93. Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016) 397 Overjet as a predictor of sagittal skeletal relationships 3 Jabbar A, Mahmood A. Correlation of OJ, ANB and wits appraisal for assessment of sagittal skeletal relationship. Pak Oral & Dent J 2012: 4(1): 17-23. 12 Tanaka JLO, Ono E, Filho EM, de Moraes LC, de Melo JC, de Moraes MEL. Influence of the facial pattern on ANB, AF-BF, and Wits appraisal. World J Orthod 2006: 7 369-75. 4 Sarver DM, Proffit WR. Special considerations in diagnosis and treatment planning. In: Graber TM, Vanarsdall RL, Vig KWL (edi). Orthodontics: current principles and techniques. 4th ed. St Louis: Mosby 2005: 03-70. 13 Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod 1975; 67: 125-38. 14 Jacobson A. Application of “Wits” appraisal. Am J Orthod 1976; 70: 179-89. 5 Zupancic S, Pohar M, Farcnik F, Ovsenik M. OJ as a predictor of sagittal skeletal relationships. Eur J Orthod 2008; 30: 269-73. 6 Proffit WRJ, Ackerman L. Contemporary Orthodontics, chapter 1, Mosby, St. Louis, Mo, USA, 2nd edition, 1993. 7 Martina D, Franc F,Vidmar G. Cephalometric standards for Slovenians in themixed dentition period. Eur J Orthod 2006; 28: 51-57. 8 AL-hammadi K, Labib A, Heider AM, Sultan A. Dentoskeletal OJ: A New Method for Assessment of Sagittal Jaw Relation. Aust J Basic App Sci 2011; 5(9): 1830-36. 18 Cangialosi TJ, Riolo ML, Owens SE. The ABO discrepancy index: a measure of case complexity. Am Jorthod Dentofac Orthop 2004; 25(3): 270-78. 9 Vaden JL, Dale JG, Klontz HA. The Tweed-Merrifield edgewise appliance: philosophy, diagnosis and treatment. In: Graber TM, Vanarsdall RL, Vig KWL (edi). Orthodontics: current principles and techniques. 4th ed. St Louis: Mosby 2005: 675-715. 19 Bishara SE, Fahl JA, Peterson LC. Longitudinal changes in the ANB angle and Wits appraisal: clinical implications,” Am J orthod Dentofac Orthop 1983; 84(2): 133-39. 10 Erum GE, Fida M. A comparison of Cephalometric analyses for assessing sagittal jaw relationship. J Coll Physicians Surg Pak 2008; 18:679-83. 11 Afzal A, Qamruddin I. Relation between centric slide and Angle's classification. J Coll Physicians Surg Pak 2005; 15: 481-84. 15 Oktay H. A comparison of ANB, WITS, AF-BF, and APDI measurements. Am J Orthod Dentofacial Orthop 1991; 99: 122-28. 16 Hussels W, Nanda RS. Analysis of factors affecting angle ANB. Am J Orthod 1984; 85: 411-23. 17 Rotberg S, Fried N, Kane J, Shapiro E. Predicting the "Wits" appraisal from the ANB angle. Am J Orthod 1980; 77: 636-42. 20 Del Santo M, “Influence of occlusal plane inclination on ANB and Wits assessments of anteroposterior jaw relationships. Am J orthod Dentofac Orthop 2006; 129(5): 641-48. 21 Iwasaki H, Ishikawa H, Chowdhury L. Properties of the ANB angle and the Wits appraisal in the skeletal estimation of Angle’s Class III patients. Eur J Orthod 2002; 24: 477-83. CONTRIBUTIONS BY AUTHORS 1 Ghulam Rasool: 2 Nayab Hassan: 3 Summiya Bashir: Supervision and proof reading Paper writing Topic selection 4 Aneela Nausheen: 5 Umar Hussain: Data collection Data analysis Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016) 398