## 1 Introduction  
The realm of esthetics has undergone a constant transformation and recently garnered monumental weight in orthodontics [1]. The pursuit of a visually pleasing smile and a balanced facial profile has become a primary objective of OT, surpassing the traditional focus on achieving functional occlusion and conforming to skeletal and dental norms [1, 2]. Although all orthodontists strive to create beautiful smiles, there is currently no standardized method for objectively analyzing frontal smiles. This lack of consistency in data collection and analysis has hindered research in this field [3]. The smile line, which determines the amount of upper incisor display, can be measured in millimeters of gingival display or as a percentage of incisor coverage. According to existing research, a pleasing smile displays between 75% and 100% of the maxillary incisors and 0-2 mm of the gingiva [4, 5, 6]. Nevertheless, there are individuals with more than 2 mm of gingival tissue, which is not considered a pathological condition but may lead to an unfavorable esthetic outcome known as a \"gummy smile.\" Excessive gingival exposure or a gummy smile can result from a short upper lip, a slightly movable lip, vertical maxillary excess (VME), anterior overexruption, wear and compensatory eruption, altered active eruption, and APE [7]. APE refers to a dental condition where excessive gum tissue covers the enamel of the teeth, creating a short clinical crown appearance and giving the impression that the teeth are hidden [8]. [PERSON] and [PERSON] define APE as the condition where the gingival margin lies above the crown's cervical convexity and away from the CEJ in adults [9]. APE is also known as \"retarded passive eruption\" or \"delayed passive eruption\" in the dental literature [10; 11]. This condition results in square-shaped clinical crowns that are not esthetically pleasing. Although a few studies have linked the mechanisms behind APE to the shape of the coronal periodontitis, there is still no concrete evidence regarding the condition's root causes [11; 12]. Despite its plethora of benefits, OT is associated with certain risks and complications, such as enamel demineralization [13], enamel fractures [14], teeth discoloration [15], periodontal diseases [16], gingival recession [17], root resorption [18], triangular gaps between the gums [19], nickel allergies [20], and the possibility of treatment failure [21]. An excessive display of the gums, unevenness in the gingival border, and a missing papilla are three unpleasant scenarios that may occur during OT, as per [PERSON]'s observations [22]. It is also mentioned in [PERSON]'s narrative review that some adolescent patients may show gingival margin discrepancies due to APE after OT [22]. The primary symptom of such issues is a smile that exposes unnaturally short clinical crowns and thickened gingival tissue that seems abnormally wide labiolingually [23]. In contrast, [PERSON] et al. reported no difference in APE between orthodontically treated and untreated patients [7]. Therefore, a systematic literature review is needed to reveal detailed evidence. Traditionally, the diagnosis and treatment planning of APE have relied upon radiographic analysis and trans-gingival probing [24; 25]. However, advancements in computed imaging have elevated the resolution of imaging to an astounding degree, enabling the analysis of soft and hard periodontal tissues. Despite CBCT being a marvelous instrument to assess soft and hard periodontal tissue dimensions, it has yet to be widely employed to resolve periodontal esthetic issues [26; 27]. Nevertheless, to the author's knowledge, no research has been published employing CBCT to investigate whether OT is an etiological factor for APE. Therefore, the primary aim of this research is to evaluate any association between OT and the development of APE.