Analyzing Dental Arch Shape in Untreated Orthodontic Patients with Anterior Arch Crowding

Abstract

Background: Crowding of the dentition results in distortion of the arch form and orthodontic treatment unravels the crowding based on the shape of the wire of arch form utilized. Alteration of an existing arch form with the wrong arch wire and biomechanics may result in unstable results. Selection of the appropriate arch wire shape based on the patient’s original arch form results in a finished orthodontic treatment which is aesthetically pleasing, preserves the shape and function, with long term stability of the finished case.

Objective: To analyze the dental arch shape in untreated orthodontic patients with anterior arch crowding.

Methods: Dental casts of 100 untreated orthodontic patients with anterior arch crowding of both the maxilla and mandible were selected and classified using Angles method. Crowding was described as mild, moderate, severe and very severe using the index described by Little. The Occlusal plane was outlined for both jaws using brass wire adapted with sticky wax along the buccal cusps of the posterior teeth on one side of the arch through the incisal edges of the anterior teeth to the buccal cusps of the posterior teeth on the other side of the arch. Data analysis was done using IBM SPSS version 22.0 software. All data was expressed as frequencies, percentages and means. The results were presented using frequency tables.

Results: Upper arch shapes were identified as square in 58(58%), tapered in 18(18%) and ovoid in 24 (24%). Lower arch shapes were square in 60(60%), tapered in 36 (36%) and ovoid in 4(4%). Anterior arch crowding was seen in both arches as mild in 68(68%), moderate in 17(17%), severe in 9(9%) and very severe in 6(6%). The highest prevalence of anterior crowding was seen in the mild variant and in the square shape in both the upper and lower arch forms in 43 (63.2%), respectively. The tapered arch form was not demonstrated in the very severely crowded upper arch, while the ovoid arch form in the lower arch was not evident in the severe and very severe variant of crowding. This was however not statistically significant.

Conclusion: The square arch form is most prevalent in cases of upper and lower crowding.

Keywords:  Dental arch, untreated orthodontics