ORIGINAL�ARTICLE ABSTRACT Objective: To determine the frequency of dental midline deviation in different age groups of school children of Lahore, Pakistan. Study Design: Observational cross-sectional study. th th Place and Duration of Study: The study was performed in 7 different schools of Lahore, from 11 March to 30 May 2019. Materials and Methods: A total sample of 300 children (190 girls, 110 boys) was taken whose ages were between 8 to 16 years. Midline deviations were observed with scale in millimeters, by taking the philtrum as a reference landmark. The statistical analysis was implemented with SPSS version 20. Qualitative data like gender, midline deviation and type of dentition was presented in the form of frequency and percentage. Data was stratified for gender and dentition. Post-stratification chi -square test was applied with p-value ≤ 0.05 considered as significant. Results: Frequency of midline deviation was found to be 69.7% of which mandibular midline deviation was more frequent (45.7%) followed by maxillary midline deviation (12.7%), with the severity of 2mm being most common (42.3%). Deviation of both midlines was observed in 11.3% of students. The difference of frequency of midline shift in gender (p=0.924) and dentition (p=0.109) was insignificant. Conclusion: The study concluded that the most frequently observed dental deviation was mandibular midline deviation towards right side relative to facial midline. No significant differences were displayed regarding gender and dentition. Key Words: Cupid's Bow, Dental Asymmetry, Incisive Papilla, Philtrum, Smile Esthetics. midline deviations and can even appreciate 1 mm 5 deviation of dental midline. The magnitude to which the maxillary and mandibular dental midlines deviate from the facial midline is often recorded, with an aim that these midlines should be coincident after orthodontic treatment. It is an essential aspect of functional occlusion and serves as a clinical 6,7,8 template to achieve maximum intercuspation. An individual's facial midline (constructed from glabella, base of the nose, nasal apex, upper lip Cupid's Bow and central point of the chin) is used as a 4,9,10 reference line to evaluate dental midline. The incisive papilla between the maxillary central incisors is normally found below the center of the 10 philtrum. One of the studies reported that the patients tend to relate their maxillary midline to the 8,11 upper lip. The philtrum is generally considered to be a valid facial landmark for assessment of 6,11 midline. However, this may be misleading due to the presence of a variable degree of asymmetry in facial structures, therefore, the incisive papilla could be an alternate intraoral landmark as it follows the Introduction Frontal symmetry and balanced smile are the 1,2 appraisal standards of facial appearance. Any discrepancy in facial and dental harmony of 3 corresponding parts can cause asymmetry. Midline deviations are most obvious of all the dental and occlusal asymmetries, as dental midline is a focal point in smile esthetics. The effect of harmonized facial and dental midlines on clinical outcome of 4 orthodontic treatment is undebatable. Orthodontists are considerably less tolerant of Frequency of Dental Midline Deviation in School Children of Lahore, Pakistan: A Cross- Sectional Study 1 2 3 4 Faiza Rana , Faiza Malik , Esha Rana , Rabia Tabassum Correspondence: Dr. Faiza Rana Demonstrator Department of Orthodontics Sharif Medical and Dental College, Lahore E-mail: dr.faizarana03@gmail.com 1,2 3 Department of Orthodontics/ Operative Dentistry Sharif Medical and Dental College, Lahore 4 Department of Orthodontics University Medical and Dental College, Faisalabad Received: May 29, 2021; Revised: June 02, 2022 Accepted: June 04, 2022 Dental Midline Deviation in School ChildrenJIIMC 2022 Vol. 17, No.2 81 9 direction of the deviation. E m p h a s i s o n d e nto - a l ve o l a r e st h et i c s h a s heightened among orthodontists and patients. Although an ideal occlusion is still an important goal of treatment, the ideal esthetic outcome is crucial for 7,8 patient's and orthodontist's gratification. The treatment for existing discrepancies in midline may involve tooth movement, dental extractions, orthopedic treatment, or even orthognathic 7 surgery. In Pakistan there has not been much previous research done to determine the frequency of maxillary and mandibular dental midline asymmetry. So, this cross-sectional survey was conducted to determine the frequency of dental midline deviation in different age groups of school children of Lahore, Pakistan. This provided some valuable local data base to create awareness among school children regarding their orthodontic treatment need. Materials and Methods This was an observational cross-sectional survey, th performed in 7 different schools of Lahore, from 11 th March to 30 May 2019. The study was done on a sample of 300 school children belonging to grade 3- 10, selected via non-probability consecutive sampling technique to determine the frequency of dental midline deviation. Sharif Medical Research Center approved the study, followed by ethical approval with the letter number SMDC/SMRC/194- 21. Prior permission was taken from the school principals. The inclusion criteria were children of both genders, aged 8 years and above, irrespective of the type of dentition and malocclusion. Children with unerupted or impacted incisors, missing or extracted teeth, history of orthodontic treatment, restoration of anterior teeth, craniofacial anomalies like cleft lip and/or palate, were excluded. Data was collected by clinical intraoral observation and examination of children after taking written informed consent from their parents. All data was collected by the primary researcher. To avoid visual fatigue, number of students examined per day was kept to a maximum of 30, which corresponded to the number of students in one class. Maxillary and mandibular dental midline deviations were measured with a clear plastic scale to the nearest millimeter by taking the philtrum (cupid's bow) as a reference landmark (figure 1). Data was non-parametric and statistical analysis was performed with IBM SPSS version 25. Qualitative data like gender, midline deviation and type of dentition were presented in the form of frequency and percentage. The magnitude and side of midline deviation was also noted. Data was stratified for gender and dentition. Post-stratification chi -square test was applied with p-value ≤ 0.05 considered as significant. Results Overall, the sample consisted of 300 students (190 females, 110 males) out of which, 157 (52.3%) were in the mixed dentition group and 143 (47.7%) were in the permanent dentition group. The mean age of the sample was 11.5 ± 2.5 years, ranging from 8-16 years. Frequency of midline deviation was found to be 69.7% (Table I) of which mandibular midline deviation was more frequent (45.7%) followed by maxillary midline deviation (12.7%). Deviation of both midlines was observed in 11.3% of students. Table II represents the severity of dental midline deviation. In most of the patients, dental midlines were shifted from the facial midline by 2mm (42.3%), that was more likely towards right side of the face. Table III shows the difference of midline deviation among gender (p = 0.924) and dentition (p = 0.109), which was statistically insignificant. Fig. 1: Measuring Maxillary Dental Midline Deviation from Philtrum of Upper Lip Table I: Frequency of Midline Deviation Dental Midline Deviation in School ChildrenJIIMC 2022 Vol. 17, No.2 82 Discussion This cross-sectional study was conducted to provide valuable local database of maxillary and mandibular dental midline deviation and to give awareness of orthodontic treatment among school children. We used philtrum as a reference for the evaluation of dental midline deviation as this is a valid facial landmark and patients generally relate their midline 11 to the upper lip. Dental midline is a vital element in smile design. Midline should be perpendicular to incisal plane and 12,13 incisive papilla. The parallelism between the maxillary dental midline and facial midline is more fundamental than the coordination between these midlines. A minor midline deviation is acceptable if connector between the maxillary central incisors is 4 vertical. D e n t o fa c i a l a t t ra c t i v e n e s s i s r e d u c e d b y discrepancies between dental and facial midlines. The maximum amount of deviation acceptable to orthodontists before it has negative impact on smile esthetics, has been documented to be 1mm to 5,7,8,14,15 2mm. Ker et al and Springer et al observed that almost 3 mm of deviation is acceptable by 16,17 layperson. Beyer and Lindauer reported that 2mm midline shift was detectable by almost 18 everyone. According to Kokich and Shapiro, a 4mm maxillary midline deviation was not noticed by laypersons, whereas a 2mm deviation in incisor a n g u l a t i o n w a s r e g a r d e d a s r e m a r k a b l y 4,5 unattractive. Therefore, dental and facial esthetics 7,16 are of fundamental concern in orthodontics. In the present study, lack of midline coincidence was found to be 69.7%. Sheats et al conducted a study at Virginia Commonwealth University and found 46% lack of midline coincidence in orthodontic 7,19 population. They also concluded that the most frequently seen trait of asymmetry was mandibular midline deviation from the facial midline and maxillomandibular midline deviation. Thilander et al 20 registered midline deviation in 13.2% subjects. They found that it increased with age and was more frequent in lower arch. Borzabadi et al observed non- coinciding dental midlines in 23.7% of urban Iranian 21 sample. This study also concluded that mandibular midline deviation was the most seen asymmetry (45.7%). Jain et al. noticed midline deviation in 77% of 22 orthodontic patients. Of overall dental midline deviation, 21% patients had maxillary midline deviation and 43% had mandibular midline deviation 22 which is almost twice of maxillary midline deviation. Bhateja and Fida observed that most frequent asymmetry seen was non-coinciding dental midlines 23 in 78.2% of patients. Mandibular midline deviation was observed in 67.5% of patients whereas, maxillary 23 midline deviation was found in 14.3% of patients. However, the side of deviation was not recorded. The severity of midline deviation in majority of patients was found to be 2 mm in this study, which is similar to the findings of Bhateja et al who reported 23 the severity of about ¼ of lower incisor width. Moreover, this study found that midline deviation was mostly towards right side of the face which is in contrast to Khan et al and Eskelsen et al who revealed that dental midline is mostly shifted towards left side 24,25 of the face. The current study, having a cross-sectional design, had some limitations. The method of evaluating midline deviation was relatively inadequate at times, mostly in the evaluation of centric occlusion and centric relation (Co-Cr) shifts. The Co-Cr shift was not investigated in this study, therefore, a possibility of mandibular midline deviation due to underlying Table II: Severity of Midline Deviation Table III: Stratification of Midline Deviation with respect to Gender and Dentition p-value > 0.05 shows insignificant statistical difference. Dental Midline Deviation in School ChildrenJIIMC 2022 Vol. 17, No.2 83 functional shifts was there. Exact assessment of Co- Cr is essential to evaluate the probable origin of such deviations. Conclusion This study concluded that mandibular midline deviation was the most frequently observed midline deviation followed by maxillary midline deviation. The common severity of deviation was 2mm most likely towards right side of the face. No statistically significant differences were displayed regarding gender and dentition. REFERENCES 1. Sriphadungporn, C., Chamnannidiadha, N. Perception of smile esthetics by laypeople of different ages. Prog Orthod. 2017; 18:1- 8. 2. Williams R, Rinchuse D, Zullo T. Perceptions of midline deviations among different facial types. Am J Orthod Dentofacial Orthop 2014; 145:249-55. 3. Bhardwaj A, Miglani A and Gupta M. Decoding the facial asymmetry. J Dent Specialities 2020;8(1):13–17. 4. Sabri R. The Eight Components of Balanced Smile. J Clin Orthod March 2005; 3:155-167. 5. Melo M, Ata-Ali J, Ata-Ali F, Bulsei M, Grella P, Cobo T, et al. Evaluation of the maxillary midline, curve of the upper lip, smile line and tooth shape: a prospective study of 140 Caucasian patients. BMC Oral Health 2020; 20: 42. 6. Narmada S, Kumar KP, Raja S. Management of mid-line discrepancies: A review. J Ind Acad Dent Spec Res 2015; 2:45-8. 7. Priya S, Sumathi A. Prevalence of maxillary midline shift in female patients. Drug Invent. /Today. 2019:11(1):77-80. 8. Rossini G, Parrini S, Castroflorio T, Fortini A, Deregibus A, Debernardi CL. Children's perceptions of smile esthetics and their influence on social judgment. Angle Orthod 2016; 86 (6): 1050–1055. 9. Al-Murtadha R, El-Housseiny S, El-Beialy AR. Maxillary Midline and Other Deviations. Austin J Dent. 2016; 3(1): 1030. 10. Ferreira JB, Silva LE, Caetano MTO, Motta AFJ, Cury- Saramago AA, Mucha JN. Perception of midline deviations in smile esthetics by laypersons. Dental Press J Orthod. 2016;21(6):51-7. 11. Khan MF, Sharaz S, Shariff M, Alam MK, Binhomran FM, Almathami SA. Discord Between the Facial and Maxillary Midline and Intermaxillary Midline Among the Population o f A s i r, S a u d i A r a b i a . P e s q u i s a B r a s i l e i r a e m Odontopediatria e Clínica Integrada 2019; 19: e4700. 12. Parrini S, Rossini G. Laypeople's perceptions of frontal smile esthetics:A systematic review. Am J Orthod Dentofacial Orthop 2016; 150:740-50. 13. Mavani S, Ramesh TR, Patel N and Patel V. Evaluation of coincidence of facial midline to dental midline and maxillary midline to mandibular midline in undergraduate students. Int. J. Adv. Res. 2017; 5(2):2364-2369. 14. Sadrhaghighi AH, Zarghami A, Sadrhaghighi S, Mohammadi A, Eskandarinezhad M. Esthetic preferences of laypersons of different cultures and races regarding smile attractiveness. Indian J Dent Res 2017; 28:156-61. 15. Öz AA, Akdeniz BS, Canlı E, Çelik S. Differences among the perceptions of dental professionals and laypersons. Turk J Orthod 2017; 30: 50-5. 16. Ker AJ, Chan R, Fields HW, Beck M, Rosenstiel S. Esthetics, and smile characteristics from the layperson's perspective: a computer-based study. J Am Dent Assoc 2008; 139:1318- 27. 17. Springer NC, Chang C, Fields HW, Beck FM, Firestone AR, Rosenstiel S, et al. Smile esthetics from the layperson's perspective. Am J Orthod Dentofacial Orthop 2011; 139:91- 101. 18. Almanea R, Modimigh A, Almogren F, Alhazzani E. Perception of smile attractiveness among orthodontists, restorative dentists, and laypersons in Saudi Arabia. J Conserv Dent 2019; 22:69-75. 19. Sheats RD, McGorray SP, Musmar Q, Wheeler TT, King GJ. Prevalence of orthodontic asymmetries. Semin Orthod 1998; 40:138-45. 20. Thilander B, Pena L. Prevalence of malocclusion and orthodontic treatment need in children and adolescents in Bogota, Colombia. An epidemiological study related to different stages of dental development. Eur J Orthod 2001; 23:153-167. 21. Borzabadi-Farahani A, Eslamipour F. Malocclusion, and occlusal traits in an Arban Iranian population. An epidemiological study of 11- to 14-year-old children. Eur J Orthod 2009; 31:477–84. 22. Jain S, Jain V. Prevalence of Midline Shift in Orthodontic Patients. Int J Current Innov Res. Dec 2015;1(10):287-290. 23. Bhateja N, Fida M, Shaikh A. Frequency of Dentofacial Asymmetries: A Cross-sectional Study on Orthodontic Patients. J Ayub Med Coll Abbottabad 2014;26(2):129-133. 24. Khan M, Kazmi S. Coincidence of Dental Midline with Facial Midline in a Sample of Pakistani Population. J Coll Physicians Surg Pak. Mar 2019;29(3):210-213. 25. Eskelsen E, Fernandes CB, Pelogia F. Concurrence between the maxillary midline and bisector to the interpupillary line. J Esthet Restor Dent 2009; 21:37-41. Dental Midline Deviation in School ChildrenJIIMC 2022 Vol. 17, No.2 84 CONFLICT OF INTEREST Authors declared no conflicts of Interest. GRANT SUPPORT AND FINANCIAL DISCLOSURE Authors have declared no specific grant for this research from any funding agency in public, commercial or nonprofit sector. DATA SHARING STATMENT The data that support the findings of this study are available from the corresponding author upon request. This is an Open Access article distributed under the terms of the Creative Commons Attribution- Non- Commercial 2.0 Generic License. Dental Midline Deviation in School ChildrenJIIMC 2022 Vol. 17, No.2 85