Alignment of Maxillary and Mandibular Midlines in Dentate Individuals: A Cross-sectional Analysis

Abstract

Introduction: The dental midline is a vital element in smile design. The maxillary and mandibular central incisors midline should ideally be positioned coinciding with each other, Incorrect placement of midlines would lead to instability in dental composition. The dental literature fails to disclose the data as to how nature positions the midline of anterior teeth. Aim: To evaluate the relation between the midlines of maxillary and mandibular dental arches in the dentate population using standardised digital photographs. Materials and Methods: This in-vitro cross-sectional study was carried out in the Department of Prosthodontics, Maharishi Markandeshwar College of Dental Sciences and Research, Mullana, Ambala, Haryana, India between June 2021 to December 2022. A total of 155 dentate subjects (102 females and 53 males) of this demographic area, all within the age group 18-45 years of age were selected for present study. Full-face standardised photographs of the subject’s frontal profile of occluding teeth in a retracted mouth were captured with a Digital Camera (Nikon D3200 DSLR). The collected samples of intraoral images were analysed in image analysing software (Digimiser version 6.0). Lines were constructed in the software to record the maxillary midline and mandibular midline to assess the coincidence or deviation between them. Direct measurements were also obtained within these constructed lines to record the distance of deviation. Direction (right/left) and distance of deviation were recorded. The collected data were subjected to appropriate statistical testing. The statistical analysis was done using the Chi-square test, t-test, etc., and performed in the statistical software International Bussiness Machine (IBM) Statisical Packages of Social Sciences (SPSS) statistics version 25 (Armonk, USA). Results: The mandibular midline did not coincide with the maxillary midline in 134 (86%) of the tested population and within both genders and showed a significant (p-value-0.00) deviation of 1.88 mm after application of the t-test. Although 78 (50%) deviations were towards the left-side and 56 (36%) toward the right-side of the maxillary midline within both genders, the results were statistically insignificant with the Chi-square test. Conclusion: Mandibular and maxillary dental midline fails to coincide in more than four-fifths of the subjects.