Lip Changes Following Non-Extraction Orthodontic Treatment Kaveh Baharvand Ahmadi 1 , Peter H Buschang 2 and Sawsan Tabbaa 3 * 1 Orthodontics Private Practice, Texas, USA 2 Director of Orthodontic Research, Texas A&M University College of Dentistry, USA 3 Director of Orthodontic Research, School of Orthodontics, Jacksonville University, USA Introduction Esthetic ideals are continuously evolving in today’s age of global media and merging cultures. It has been estimated that 3 out of 4 patients come to orthodontists to improve facial attractiveness [1]. Lips are among the most important features that determine attractiveness [2]. For example, lip thickness has been shown to be critical in the perception of beauty, [3,4] with thicker lips being positively related to higher esthetic perceptions [5]. The public notices the lip changes more than nose or chin changes [6]. It is essential for orthodontists to differentiate between lip changes due to treatment and those due to growth. For untreated subjects between 6-18 years of age, upper lip length increases approximately 4mm, thickness increases 1-2mm and protrusion decreases only slightly (0.5mm); lower lip length (9-10mm) and thickness (2-3mm) both increase [7]. Adolescents’ lips become relatively more retrusive over time, substantially longer, and somewhat thicker [8,9]. In contrast, adults show different patterns of change. Untreated adult soft tissues change at much slower rates. Their lips continue to retrude and tend to flatten, especially at the older ages [10-12]. Relationships between the lips and the underlying dental structures were demonstrated as early as 1834. 7 Soft tissue changes following the orthodontic treatment are usually considered secondary to tooth and skeletal alterations [13]. Some authors have reported simple linear relationships between hard tissue and soft tissue profile changes [14,15]. Ratios, which relate lip changes to the amount of incisor retraction, have been reported to range from 1:1.75 to 1:2.2 for the upper lip, and from 1:1.2 to 1:1.4 for the lower lip [16,17]. Importantly, ratios assume that lip movements can be predicted by a single hard tissue measure, which limits their ability to predict [18,19]. Moreover, ratios imply that the relationship between hard and soft tissue changes is linear, which is not necessarily the case [8,20,21]. Ratios also provide no information about their predictive accuracy. Ratios have been reported to bias soft tissue changes, due to the fact they do not account for the effects of the other independent variables on the measured dependent variable [21]. Crimson Publishers Wings to the Research Research Article *Corresponding author: Sawsan Tabbaa, Associate Professor, Orthodontics Research Director, School of Orthodontics, Brooks Rehabilitation College of Health Sciences, Jacksonville University, 2800 University Blvd N. Jacksonville. Fl. 32211, USA Submission: August 01, 2019 Published: August 08, 2019 Volume 4 - Issue 3 How to cite this article: Kaveh Baharvand Ahmadi, Peter H Buschang, Sawsan Tabbaa. Lip Changes Following Non- Extraction Orthodontic Treatment. 4(3). MRD.000587.2019. DOI: 10.31031/MRD.2019.04.000587 Copyright@ Sawsan Tabbaa, This article is distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use and redistribution provided that the original author and source are credited. ISSN: 2637-7764 381 Modern Research in Dentistry Abstract Introduction: The purpose of this study was to predict the lip changes in Class I adolescents and adults following non-extraction orthodontics treatment. Methods: This longitudinal retrospective study evaluated the pre- and post-treatment lateral cepha- lograms of 40 adults and 72 adolescents with Angle Class I molar relationships and crowding in both arches. The horizontal and vertical changes of 15 landmarks, along with lip thickness and taper, were evaluated. The sample was randomly divided into two group; 76% of the subjects were used to develop the multivariate regression formulas; the remaining 24% served as a validation sample. Result: Adolescent lips moved inferiorly and anteriorly during treatment; adult lips showed lesser infe- rior movement, little or no anterior movement and decreases in thickness. Males demonstrated signifi- cantly greater inferior and, mostly, greater anterior changes of lip position. The multivariate regressions explained 48-59% and 41-69% of the vertical and horizontal variation of the lip changes, respectively. When the prediction equations were applied to the validation sample, with correlations ranged from 0.60-0.84, indicating external validity. Conclusion: The lip changes of Class I adolescents and adults treated with non-extraction orthodontic treatment can be predicted with fair to moderate accuracy. Adults’ lips became compressed and thinner, while the upper lip thickness of adolescents did not change or become slightly thicker.