1Department of Orthodontics, M. S. Ramaiah University of Applied Sciences, Bangalore, India; 2Department of Orthodontics, Military Dental Centre, Ministry of Defence, Muscat, Oman; 3Department of Orthodontics, Oman Dental College, Muscat, Oman *Corresponding Author’s e-mail: pacchi77@yahoo.com املعايري الطبيعية لقياس الرأس لدى السكان العمانيني العرب البالغني بار�شنثا �شيافامورتي جوفيناكويف، اإبراهيم البو�شعيدي، في�شوابورنا �شنجوتوفان abstract: Objectives: This study aimed to establish cephalometric norms for an Omani population of Arab descent and to compare these with established cephalometric values for Caucasians. Methods: This cross-sectional study was conducted at the Military Dental Centre and Oman Dental College in Muscat, Oman, between May 2014 and October 2016. A total of 150 Omani patients between 20–29 years old seeking orthodontic treatment were included. All participants had a symmetrical face, class I molar and canine relationships, proper intercuspation, a normal overjet/overbite (<3 mm) and mild spacing/crowding of the teeth (≤3 mm). Lateral cephalography was performed in centric occlusion with the lips relaxed and the head in a natural position. Cephalometric measurements were then compared with Eastman Standard norms. Results: The Omani subjects were found to have a slightly retrusive maxilla, an increased angle between the maxillary and mandibular planes and shorter facial heights in comparison to the Eastman Standard norms. Furthermore, incisor relations were edge-to-edge in nature and the interincisal angle was reduced, suggesting that the Omani subjects had more proclined incisors. In addition, the lips were more protrusive and the nasolabial angle was more obtuse. Conclusion: In the Omani sample, increased proclination of the incisors was observed in comparison to Eastman Standard norms. As such, slightly more proclined incisors should be considered acceptable and natural among Omani patients of Arab descent. The cephalometric findings of this study may be helpful in the diagnosis and treatment planning of orthodontic problems among Omanis of Arab descent. Keywords: Cephalometry, standards; Population Characteristics; Ethnic Groups; Arabs; Orthodontics; Oman. الراأ�ض قيا�شات قيم مع ومقارنتها العرب العمانيني ال�شكان لدى الراأ�ض لقيا�ض معايري و�شع اإىل الدرا�شة هذه هدفت الهدف: امللخ�ص: املعتمدة لدى القوقازيني. الطريقة: اأجريت هذه الدرا�شة املقطعية العر�شية يف مركز طب الأ�شنان الع�شكري وكلية عمان لطب الأ�شنان يف م�شقط، عمان، بني عامي 2014 و 2016. مت اختيار جمموعة من 150 مري�شا عمانيا بني �شن 29–20 عاما كانوا يبحثون عن عالج لتقومي الأ�شنان. كان لدى جميع امل�شاركني وجه متماثل، اإطباق الرحى والأنياب من الدرجة الأوىل، ت�شابك حدبات متكافئ، قيا�ض طبيعي لرتاكب الع�شة العمودي والأفقي )اأقل من 3 ملم(، وكان التباعد/الر�ش�ض ال�شني معتدل بني الأ�شنان )3≤ ملم(. مت اإجراء اأ�شعة الراأ�ض اجلانبية يف و�شع اإنطباق مركزي لالأ�شنان مع ارتخاء ال�شفاه والراأ�ض يف و�شعها الطبيعي. مت بعد ذلك مقارنة قيا�شات الراأ�ض مع معايري اإي�شتمان القيا�شية. النتائج: وجد اأن املجموعة العمانية لديها تراجع ب�شيط يف الفك العلوي، زيادة الزاوية بني م�شتوى الفك العلوي وال�شفلي وق�رض يف ارتفاعات الوجه مقارنة مبعايري اإي�شتمان القيا�شية. كما كان طابع العالقة بني القواطع من احلافة اىل احلافة، وزاوية الإنق�شام بينهم منخف�شة العالقات بني القواطع ذات طبيعة من احلافة اإىل احلافة، وانخفا�ض يف زاوية النق�شام بني القواطع، مما يوحي باأن املجموعة العمانية لديهم قواطع اأكرث اإنحراف اإىل الأمام. بالإ�شافة اإىل ذلك، كانت ال�شفتني اأكرث بروزا وكانت الزاوية الأنفية ال�شفوية اأكرث انفراجا. اعتبار ينبغي النحو، هذا على القيا�شية. ال�رضقية املعايري مع باملقارنة القواطع تداخل تزايد لوحظ العمانية، املجموعة يف اخلال�صة: القواطع املنحرفة لالأمام ب�شكل طفيف مقبولة وطبيعية بني املر�شى العمانيني العرب. قد تكون نتائج قيا�شات الراأ�ض يف هذه الدرا�شة مفيدة يف ت�شخي�ض وعالج م�شاكل تقومي الأ�شنان بني العمانيني العرب. الكلمات املفتاحية: قيا�شات الراأ�ض؛ معايري؛ خ�شائ�ض ال�شكان؛ فئات اأثنية؛ عرب؛ تقومي الأ�شنان؛ عمان. Cephalometric Norms in an Omani Adult Population of Arab Descent *Prashantha S. Govinakovi,1 Ibrahim Al-Busaidi,2 Viswapurna Senguttuvan3 clinical & basic rEsEarch Sultan Qaboos University Med J, May 2018, Vol. 18, Iss. 2, pp. e182–189, Epub. 9 Sep 18 Submitted 12 Dec 17 Revision Req. 21 Jan 18; Revision Recd. 22 Feb 18 Accepted 15 Mar 18 doi: 10.18295/squmj.2018.18.02.010 because cephalometric norms vary widely between different ethnic groups.1–3 While minor differences between an individual’s cephalometric values and those of the respective norms is routine, major differences may indicate a structural deviation. Knowledge of the The diagnosis of potential orthodontic anomalies necessitates the comparison of an individual patient’s cephalometric values with those of established norms.1 However, the patient’s ethnic background needs to be taken into consideration Advances in Knowledge - To the best of the authors’ knowledge, this study is the first to establish cephalometric norms for an Omani population of Arab descent. Application to Patient Care - Establishing cephalometric norms for Omanis of Arab descent could help dentists to detect any orthodontic deviations for diagnostic or treatment purposes. Prashantha S. Govinakovi, Ibrahim Al-Busaidi and Viswapurna Senguttuvan Clinical and Basic Research | e183 nature of the mandible and bimaxillary dento-alveolar protrusion, with males having a steeper MN angle.2 Among Saudi Arabian students with acceptable profiles and occlusion, a craniofacial analysis indicated the students had a slightly protrusive maxilla, with a tendency towards class II facial patterns, high MN angles and procumbent maxillary and mandibular incisors in comparison to Caucasian subjects.8 In Oman, the native population has a unique culture and lineage, with a history of considerable ethnic diversity.9 Although previous studies have attempted to set normative standards in the Arabian Gulf region, none have so far focused on Omanis of Arab descent.2–4,7,8 Therefore, the present study aimed to establish cephalometric standards for an Omani population of Arab descent and compare these with Eastman Standard norms.10–27 Methods This cross-sectional study was conducted at the Military Dental Centre and Oman Dental College in Muscat, Oman, from May 2014 to October 2016. A sample of 150 Omani patients aged 20–29 years old seeking orthodontic treatment at these two institutions were selected. All subjects were of Arab descent from both parents’ side, without any history of interracial marriages occurring for at least two generations. Each subject underwent a clinical examination by two orthodontists to ensure they had a symmetrical face (in which a line drawn from the forehead to the chin would yield measurements conforming to the mathematical concept of the golden ratio), class I molar and canine relations with proper intercuspation and an acceptable overjet and overbite (<3 mm), mild spacing/crowding (≤3 mm), no transverse discrepancies and no detectable lateral and sagittal way in which an individual’s cephalometric values differ from accepted norms will allow clinicians to conclude whether the anomaly is dento-alveolar or skeletal in origin and undertake corrective measures if necessary.4 In a comparison of cephalometric norms between Egyptian adolescents and those of a sample in Iowa, USA, Bishara et al. concluded that Egyptian boys tended to have bimaxillary dental protrusion and greater posterior facial heights (PFHs), whereas Egyptian girls had mandibular dental protrusion and more convex skeletal profiles.5 In a Jordanian population, Hamdan et al. concluded that, in comparison to a British sample, Jordanians had reduced lower facial heights and more proclined upper incisors (UIs) and lower incisors (LIs); this finding was substantiated by a reduced interincisal angle.3 Al-Awwad et al. compared the cephalometric norms of a sample of adult Kuwaitis with those of previously published Caucasian norms, reporting that the Kuwaiti subjects had more proclined incisors and significantly more obtuse nasolabial angles; more- over, females had more protrusive lower lips with more proclined LIs compared to males.6 Another study found that adolescent Kuwaitis had a steeper mandibular plane (MN) and a more convex profile, with reduced chin protrusion and more protrusive dentition compared to published norms.4 Shalhoub et al. established cephalometric radio- graphical norms for Saudi Arabian adults by comparing normal facial proportions with a North American sample; the Saudi subjects showed reasonably normal dental relationships, with no severe anteroposterior, vertical or transverse skeletal discrepancies.7 In west- ern Saudi Arabia, previous findings have suggested that western Saudis have an increased A point/ nasion/B point (ANB) angle due to the retrognathic Figure 1: Example of a cephalogram with (A) identified anatomical landmarks and (B) automated cephalometric measurements generated using imaging software. ANS = anterior nasal spine; UI = upper incisor; LI = lower incisor. Cephalometric Norms in an Omani Adult Population of Arab Descent e184 | SQU Medical Journal, May 2018, Volume 18, Issue 2 shifts. Medically compromised subjects and those with congenital abnormalities, facial trauma, missing/ extracted teeth or a history of orthodontic treatment, orthognathic surgery or plastic surgery were excluded from the study, as such individuals were deemed not to represent the typical facial characteristics of an Arab Omani population. The sample size was calculated using nMaster software, Version 1.0 (Department of Biostatistics, Christian Medical College, Vellore, India) based on the following formulae: Where Sp is the target population, Z is the confidence interval (1.96), a is the α error (assumed to be 1%), B is the β error (assumed to be 10% at a power of 90%), D is the effect size (i.e. the mean difference between males and females) and SD is the standard deviation. The mean and SD of randomly selected variables, including the ANB, sella/nasion (SN) line to the maxillary plane (MP) and the lower dental facial height (LDFH), defined as the distance between the LI tip to the MN, was estimated based on 15 male and 35 female subjects. The minimum sample size was therefore calculated to be 35 subjects of each gender. However, in order to improve the statistical power of the results, the sample size was increased to a total of 150 subjects. All of the subjects underwent routine two- dimensional (2D) lateral cephalography in centric 2Sp2 [Z1 − + Z1 − B] 2 N = D2 a 2 SD of males + SD of females Sp − pooled SD = 2 Table 1: Definition of various cephalometric parameters used in the current study Parameter Definition Skeletal SNA Position of the maxilla in relation to the skull base (i.e. the angle between the SN and NA planes) SNB Position of the mandible in relation to the skull base (i.e. the angle between the SN and NB planes) ANB Sagittal relationship between the maxilla and mandible (i.e. the angle between the NA and NB planes) SN-MP Vertical relationship between the maxilla and cranium (i.e. the angle between the SN and ANS and PNS planes) PPL-MN Angle between the PPL and MN LAFH Distance between the Me and MP (i.e. distance between the Me and ANS) UAFH Distance between the N and MP (i.e. distance between the N and ANS) LAFH/TAFH Ratio of LAFH to the TAFH (i.e. ratio of the N-ANS to the ANS-Me) LPFH Distance between the Go and MP (i.e. distance between the Go and PNS) UPFH Distance between the S and MP (i.e. distance between the S and PNS) PFH Distance between the S and Go Wits appraisal Extent to which the jaws are related to each other* Dental Overjet Horizontal overlap of the incisors from the labial aspect of the LI to the incisal edge of the UI Overbite Vertical overlap of the incisors from the incisal edge of the UI to the incisal edge of the LI UI-MP Angle between the UI axis and MP LI-MP Angle between the LI axis and MP UI-LI Angle between the UI and LI axes LI protrusion Distance between the incisal edge of the LI and the line joining point A to Po LI-FP Distance between the incisal edge of the LI and the line joining N to Po B-NPo Distance between point B and the line joining N to Po LDFH Distance between the tip of the LI and the MP Soft tissue UL-EP Distance between the UL and Ricketts’ E line† LL-EP Distance between the LL and Ricketts’ E line† NLA Angle between the Co and Sn of the UL Chin thickness Distance between the hard and soft tissue Po SNA = sella (S)/nasion (N) point A; SNB = SN point B; ANB = A point/N/B point; MP = maxillary plane; ANS = anterior nasal spine; PNS = posterior nasal spine; PPL = palatal plane; MN = mandibular plane; LAFH = lower anterior facial height (AFH); Me = menton; UAFH = upper AFH; TAFH = total AFH; LPFH = lower posterior facial height (PFH); Go = gonion; UPFH = upper PFH; LI = lower incisor; UI = upper incisor; Po = pogonion; FP = facial plane; LDFH = lower dental facial height; UL = upper lips; EP = E plane; LL = lower lips; NLA = nasolabial angle; Col = columella; Sn = philtrum. *Measured by drawing perpendicular lines from points A and B on the maxilla and mandible, respectively, to the occlusal plane through the region of overlapping cusps of the first premolar and first molars. †Measured by drawing a line from the tip of the nose to the soft tissue Po. Prashantha S. Govinakovi, Ibrahim Al-Busaidi and Viswapurna Senguttuvan Clinical and Basic Research | e185 occlusion with the lips relaxed and a natural head position, in which the Frankfort plane was parallel to the floor. The cephalograms were taken from a distance of 150 cm away using an Orthophos XG 5 SD X-ray unit (Dentsply Sirona, York, Pennsylvania, USA). Although three-dimensional (3D) cephalometric analyses have recently gained popularity, recent research has indicated that 3D analysis does not ensure more accurate results than conventional 2D analysis.28 Subsequently, digital versions of the lateral cephalograms were examined using Dolphin imaging software, Version 11.8 (Dolphin Imaging & Management Solutions, Chatsworth, California, USA). A single examiner identified anatomical landmarks on the cephalogram directly on the monitor using markings on a ruler to calibrate the magnification. A dot was placed and moved around on the image until the examiner was satisfied that the position of the landmark had been accurately recorded. After all of the landmarks were clearly identified, various linear and angular measurements were automatically generated by the program [Figure 1]. In order to assess if any errors were made while localising the landmarks, 10 random radiographs were retraced after three weeks to determine examiner error and confirm the reproducibility of measurements at a 95% confidence interval. There were very few measurement errors for all of the variables tested, except for PFH, measured from the sella to the gonion, which resulted in an intra-class correlation coefficient of 0.504 for the male subjects. Table 1 lists the definitions used in the measurement of each cephalometric parameter. Microsoft Excel, Version 2007, (Microsoft Corp., Redmond, Washington, USA), and the Statistical Package for the Social Sciences (SPSS), Version 10.0 (IBM Corp., Armonk, New York, USA), were used for data entry and analysis. The data were tested for normalcy as per previously described methods.29 The results were presented as means ± SD for continuous variables and numbers and percentages for discrete variables. Due to the large sample size and normal distribution of the results, parametric tests were applied. Each of the parameters for male and female subjects were compared using an independent samples t-test. A one-sample t-test was used for comparison between published Eastman Standard values and those of the current study.10–27 The level of statistical significance was set at P <0.050. Ethical approval to conduct this study was obtained from the Research & Ethical Review & Approval Committee of the Ministry of Health in Oman (#MH/DGP/R&S/30/2013). All of the subjects included in the study were informed of the nature and purpose of the study and the radiographic procedures involved. Verbal consent was provided for the use of the radiographs for research purposes, under the condition that the subjects’ anonymity was maintained. Results A total of 150 Omani subjects of Arab descent were included in the study, of which 91 (60.7%) were female and 59 (39.3%) were male. The mean age was 25.3 ± 0.5 years old. In terms of gender, males had significantly higher palatal-MP angles compared to females (28.22 ± 5.69 Table 2: Cephalometric norms according to gender in an adult Omani population (N = 150) Parameter Mean ± SD P value Males (n = 59) Females (n = 91) Skeletal SNA in degrees 80.94 ± 4.7 81.44 ± 4.23 0.498 SNB in degrees 80.00 ± 4.77 78.98 ± 3.92 0.157 ANB in degrees 1.04 ± 2.84 2.46 ± 2.31 0.001 SN-MP in degrees 7.57 ± 4.04 9.22 ± 3.65 0.010 PPL-MN in degrees 28.22 ± 5.69 25.95 ± 5.15 0.012 LAFH in mm 60.87 ± 10.31 58.38 ± 6.45 0.070 UAFH in mm 49.59 ± 6.39 49.93 ± 3.56 0.674 LAFH/TAFH ratio in % 34.90 ± 27.75 38.24 ± 25.32 0.449 LPFH in mm 34.08 ± 7.09 34.21 ± 5.85 0.902 UPFH in mm 41.20 ± 5.90 39.05 ± 4.26 0.011 PFH in mm 73.95 ± 9.92 71.99 ± 6.18 0.138 Wits appraisal in mm -1.47 ± 3.73 -0.03 ± 2.79 0.008 Dental Overjet in mm 2.21 ± 1.91 2.79 ± 2.16 0.095 Overbite in mm 1.12 ± 1.77 1.68 ± 1.8 0.063 UI-MP in degrees 116.61 ± 7.22 115.51 ± 8.77 0.423 LI-MN in degrees 93.91 ± 8.17 96.54 ± 7.53 0.046 UI-LI in degrees 121.25 ± 10.06 121.78 ± 11.59 0.773 LI protrusion in mm 3.11 ± 2.89 2.54 ± 2.44 0.202 LI-FP in mm 2.83 ± 3.07 3.27 ± 2.84 0.368 B-NPo in mm -1.59 ± 1.82 -1.47 ± 1.19 0.632 LDFH in mm 38.23 ± 5.02 36.54 ± 3.33 0.014 Soft tissue UL-EP in mm 2.76 ± 3.71 2.43 ± 2.86 0.533 LL-EP in mm -1.00 ± 2.27 -0.7 ± 1.84 0.380 NLA in degrees 106.00 ± 8.82 105.31 ± 10.34 0.672 Chin thickness in mm 12.17 ± 2.60 11.81 ± 2.48 0.390 SD = standard deviation; SNA = sella (S)/nasion (N) point A; SNB = SN point B; ANB = A point/N/B point; MP = maxillary plane; PPL = pala- tal plane; MN = mandibular plane; LAFH = lower anterior facial height (AFH); UAFH = upper AFH; TAFH = total AFH; LPFH = lower post- erior facial height (PFH); UPFH = upper PFH; UI = upper incisor; LI = lower incisor; FP = facial plane; B-NPo = point B/N/pogonion; LDFH = lower dental facial height; UL = upper lips; EP = E plane; LL = lower lips; NLA = nasolabial angle. Cephalometric Norms in an Omani Adult Population of Arab Descent e186 | SQU Medical Journal, May 2018, Volume 18, Issue 2 degrees versus 25.95 ± 5.15 degrees; P = 0.012). However, females had higher ANB (2.46 ± 2.31 degrees versus 1.04 ± 2.84 degrees; P = 0.001) as well as SN-MP (9.22 ± 3.65 degrees versus 7.57 ± 4.04 degrees; P = 0.010) angles. As per the Wits appraisal value, jaw disharmony among males was significantly more severe compared to females (-1.47 ± 3.73 mm versus -0.03 ± 2.79 mm; P = 0.008). Females had significantly higher LI-MN angles (96.54 ± 7.53 degrees versus 93.91 ± 8.17 degrees; P = 0.046) and lower LDFHs (36.54 ± 3.33 mm versus 38.23 ± 5.02 mm; P = 0.014) when compared to males [Table 2]. In comparison with Eastman Standard norms, statistically significant differences were noticed for all of the mean cephalometric values of the Omani subjects, apart from SN point B (SNB) and ANB values. The Omani subjects had a significantly smaller SN point A (SNA) value (81.24 ± 4.40 degrees versus 82.01 ± 3.89 degrees; P = 0.036), suggesting a retro-positioned maxilla.12 In addition, the Omani subjects had slightly more divergent basal planes, as indicated by their significantly higher palatal-MP (26.84 ± 5.46 degrees versus 25 ± 6 degrees; P <0.001) and SN-MP (8.57 ± 3.87 degrees versus 7 ± 3 degrees; P <0.001) angles.12,13 In addition, the Omani subjects had significantly smaller anterior and PFHs (P <0.001 each).11,13–16 According to the Wits appraisal value, the SD value of jaw disharmony of the Omani population was just over 1 mm less than that of the Eastman Standard norms (-0.59 ± 3.25 mm versus 0.59 ± 1.84 mm; P <0.001).19 Both the overjet and overbite of the Omani subjects was significantly decreased in comparison to Eastman Standard norms (P <0.001 each), with the Omani subjects having more proclined incisors.20,21 With regards to soft tissue parameters, the upper and lower lips were significantly more protrusive in the Omani subjects and the nasolabial angle was significantly more obtuse (P <0.001 each) [Table 3].10–27 Discussion During orthodontic evaluation, a cephalometric analysis can reveal important anatomical information regarding the internal structures of the facial complex, particularly in terms of skeletal and dento-alveolar anomalies.30 While various cephalometric norms have been published in an attempt to define normal skeletal characteristics, most attempts have utilised populations of North American or European Caucasians.10,11,31,32 However, it is apparent that the cephalometric norms for one ethnic group do not necessarily apply to others.5,32–41 The present study was undertaken to establish cephalometric norms for a young population of Omanis of Arab descent. Statistically significant differences were observed in comparison to Eastman Standard norms for almost all of the cephalometric variables.10–27 With regards to skeletal parameters, the Omani subjects had a significantly smaller SNA angle in comparison to the Eastman Standard norms, suggesting a retro-positioned maxilla.12 In contrast, previous studies conducted to establish cephalometric norms in other Arab populations have shown variations in SNA and SNB angles [Table 4].2–5,8,38–40,42 Overall, Arab Omanis were found to have a more retruded maxilla when compared to the Eastman Standard norms or Egyptian, Saudi, Kuwaiti and Emirati samples; however, they were less retruded than Jordanian, Moroccan and Yemeni samples.3–5,8,38–40,42 Nevertheless, results Table 3: Comparison of cephalometric norms in an adult Omani population (N = 150) with Eastman Standard norms10–27 Parameter Mean ± SD P value Arab Omanis (N = 150) Eastman Standard norms Skeletal SNA in degrees 81.24 ± 4.40 82.01 ± 3.8912 0.036 SNB in degrees 79.38 ± 4.28 79.77 ± 3.6912 0.272 ANB in degrees 1.90 ± 2.61 2.04 ± 1.8112 0.517 SN-MP in degrees 8.57 ± 3.87 7 ± 313 <0.001 PPL-MN in degrees 26.84 ± 5.46 25 ± 614 <0.001 LAFH in mm 59.35 ± 8.24 64.95 ± 3.5511 <0.001 UAFH in mm 49.79 ± 4.85 52.35 ± 2.815,16 <0.001 LAFH/TAFH ratio in % 36.92 ± 26.25 5517 <0.001 LPFH in mm 43.00 ± 34.50 43.0 ± 418 <0.001 UPFH in mm 39.89 ± 5.06 52.25 ± 1.9513 <0.001 PFH in mm 72.75 ± 7.89 79.0 ± 4.513 <0.001 Wits appraisal in mm -0.59 ± 3.25 0.59 ± 1.8419 <0.001 Dental Overjet in mm 2.56 ± 2.07 3.2 ± 0.520,21 <0.001 Overbite in mm 1.45 ± 1.80 3.2 ± 0.720,21 <0.001 UI-MP in degrees 115.93 ± 8.18 112 ± 613 <0.001 LI-MN in degrees 95.50 ± 7.86 91.4 ± 3.7810 <0.001 UI-LI in degrees 121.57 ± 10.98 135.4 ± 5.7610 <0.001 LI protrusion in mm 2.76 ± 2.62 1 ± 222 <0.001 LI-FP in mm 3.10 ± 2.93 1.6 ± 223 <0.001 B-NPo in mm -1.52 ± 1.46 -2 ± 227 <0.001 LDFH in mm 37.20 ± 4.14 40 ± 215,16 <0.001 Soft tissue UL-EP in mm 2.55 ± 3.21 -5.4 ± 222 <0.001 LL-EP in mm -0.82 ± 2.01 -2.0 ± 222 <0.001 NLA in degrees 105.57 ± 9.74 102.0 ± 424 <0.001 Chin thickness in mm 11.95 ± 2.52 12.65 ± 1.925,26 <0.001 SD = standard deviation; SNA = sella (S)/nasion (N) point A; SNB = SN point B; ANB = A point/N/B point; MP = maxillary plane; PPL = palatal plane; MN = mandibular plane; LAFH = lower anterior facial height (AFH); UAFH = upper AFH; TAFH = total AFH; LPFH = lower posterior facial height (PFH); UPFH = upper PFH; UI = upper incisor; LI = lower incisor; FP = facial plane; B-NPo = point B/N/pogonion; LDFH = lower dental facial height; UL = upper lips; EP = E plane; LL = lower lips; NLA = nasolabial angle. Prashantha S. Govinakovi, Ibrahim Al-Busaidi and Viswapurna Senguttuvan Clinical and Basic Research | e187 from the present study showed no significant difference with Eastman Standard norms regarding the sagittal relationship between the maxilla and the mandible (i.e. the ANB angle).12 Previous studies in Saudi Arabia and Jordan have reported similar findings, while other studies in Kuwait, Saudi Arabia, Morocco and Yemen have reported conflicting findings.2,3,37–40 Arab Omanis were found to have relatively reduced ANB angles compared to reports for other Arab populations.2–5,8,38–40,42 On the other hand, the angle between the palatal and MN planes was significantly higher among the current sample of Omani adults in comparison to Eastman Standard norms.14 Furthermore, the SN-MP angle was significantly higher among the Omani subjects by 1.57 degrees.13 It can therefore be concluded that Omanis have slightly more divergent basal planes, as well as a more caudally tipped palatal plane. This is in accordance with a previous study conducted in Saudi Arabia, but in contrast to Hamdan et al.’s findings among Jordanian adolescents.2,3 In the current study, the lower and upper anterior facial heights of the Omani subjects were significantly shorter than those in Eastman Standard norms, by 5.6 mm and 2.6 mm, respectively; moreover, the ratio of lower anterior facial height to upper anterior facial height was significantly lower (-18.1%).11,15–17 Thus, it seems that Omanis have considerably smaller anterior facial heights, which is in accordance with Hamdan et al.’s findings.3 In addition, the upper PFH and overall PFH of the Omani subjects were significantly shorter, by 12.4 mm and 6.3 mm, respectively, compared to Eastman Standard norms.13 However, lower PFH was similar to that of Eastman Standard norms.18 This is in contrast to the findings of Bishara et al. and Behbehani et al. among Egyptian and Kuwaiti adolescents, respectively.5,37 The Wits appraisal value for the studied Omani population was also significantly different to that of Eastman Standard norms.19 In terms of dental parameters, both the overjet and overbite values for the studied Omani population were significantly lower than those of Eastman Standard norms.20,21 Moreover, the angles between the UI and MP and the LI and MN were increased by 3.9 and 4.1 degrees, respectively, while the interincisal angle was decreased by 13.8 degrees, suggesting that the Omani subjects had more proclined incisors compared to Eastman Standard norms.10,13 In addition, Omanis had the greatest degree of incisor proclination compared to other Arab populations, apart from Emiratis.2–5,8,38–40,42 Protrusion of the LI and the distance between the LI and facial plane was also increased by 1.8 mm and 1.5 mm, respectively.22,23 This finding is in accordance with other studies of Arab populations which indicated greater proclined incisor relations.2–5,8,38–40,42 Finally, the LDFH of the Omani subjects was shorter than those of Eastman Standard norms by 2.8 mm.15,16 Within soft tissue parameters, both the upper and lower lips were more protrusive in the current Omani sample in comparison to Eastman Standard norms, by 7.9 and 1.2 mm, respectively.22 Behbehani et al. reported similar findings in a Kuwaiti population.37 In the current study, the nasolabial angle was also significantly more obtuse by 3.6 degrees in comparison to Eastman Standard norms.22 Regarding gender differences within the studied Omani population, females had a significantly greater sagittal relationship between the maxilla and mand- ible, as evidenced by their ANB values. This feature was further supported by the females having a more positive Wits appraisal value. These findings suggest that Omani females display a more retrusive mandible, which is in contrast to reported findings from other Arab populations.3,5,42 In addition, females in the current Table 4: Comparison of selected cephalometric norms in an adult Omani population (N = 150) with other Arab populations2–5,8,38–40,42 Author and year of study Population Mean ± SD SNA in degrees SNB in degrees ANB in degrees Wits appraisal in mm UI-LI in degrees Current study (2018) 150 Omani adults 81.24 ± 4.40 79.38 ± 4.28 1.90 ± 2.61 -0.59 ± 3.25 121.57 ± 10.98 Hassan (2006)2 70 Saudi adults 80.8 ± 4.06 77.5 ± 4.48 3.7 ± 1.522 - - Hamdan et al. (2001)3 65 Jordanian adolescents 80.7 ± 3.67 77.7 ± 3.19 3.0 ± 1.96 - 127.5 ± 7.93 Bishara et al. (1990)5 90 Egyptian adolescents 82.7 ± 3.6 79.5 ± 3.5 3.2 ± 1.7 -0.1 ± 2.8 124.1 ± 8.4 Al-Jasser (2000)8 87 Saudi students 83.6 ± 4.3 81.0 ± 3.7 2.5 ± 2.0 - 124.8 ± 6.9 Al-Jame et al. (2006)4 162 Kuwaiti adolescents 83.04 ± 3.6 79.44 ± 3.4 3.6 ± 2.16 -0.48 ± 2.36 - Aldrees (2011)38 485 Saudi adults 82.49 ± 4.17 79.55 ± 3.84 2.93 ± 2.31 0.13 ± 2.47 - Ousehal et al. (2012)39 71 Moroccan adults 80.59 ± 3.8 77.68 ± 3.55 3.11 ± 1.68 - - Daer et al. (2016)40 194 Yemeni students 80.86 ± 2.54 77.89 ± 2.52 2.97 ± 1.35 - 126.65 ± 7.19 Al Zain et al. (2012)42 61 Emirati adults 81.7 78.6 3.1 - 118.6 SD = standard deviation; SNA = sella (S)/nasion (N) point A; SNB = SN point B; ANB = A point/N/B point; UI = upper incisor; LI = lower incisor. Cephalometric Norms in an Omani Adult Population of Arab Descent e188 | SQU Medical Journal, May 2018, Volume 18, Issue 2 study had significantly more proclined LIs compared to males, as expressed by the LI-MN angle; this is in accordance with findings of Bishara et al.5 This study is subject to certain limitations. As noted earlier, Oman is a heterogenous country and is native to individuals of various ethnicities and races, with Arabs representing only a portion of the total population.9 Therefore, in order to determine accurate and specific cephalometric norms for the Omani population, a larger sample comprising all of the different tribes existing in the country should be evaluated. Conclusion In comparison to Eastman Standard norms, the Arab Omani subjects were found to have a slightly more retrusive maxilla and an increased MP-MN angle. Their vertical facial heights were also significantly shorter than those of Eastman Standard norms. The Wits appraisal value for the Omani subjects was also comparatively reduced, nearing zero. In terms of dental parameters, the incisor relations of the Omani subjects were edge-to-edge in nature and the interincisal angle was reduced, suggesting more proclined incisors. With regards to soft tissue parameters, the lips of the Omani subjects were significantly more protrusive and the nasolabial angle more obtuse compared to the Eastman Standard norms. These findings suggest that certain cephalometric parameters, such as slightly more proclined incisors, should be considered acceptable and normal within the Arab Omani popul- ation, despite differing from Eastman Standard norms. c o n f l i c t o f i n t e r e s t The authors declare no conflicts of interest. f u n d i n g No funding was received for this study. References 1. Kapila S. Selected cephalometric angular norms in Kikuyu children. Angle Orthod 1989; 59:139–44. doi: 10.1043/0003- 3219(1989)059<0139:SCANIK>2.0.CO;2. 2. 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