Comparative evaluation of transpalatal arch and vertical holding appliance at different heights

Abstract

Objectives: An effective method for controlling vertical dysplasia remains a concern for orthodontists. This study aims to compare the stresses on the maxillary first molars while changing the height of the loop/acrylic pad of the transpalatal arch (TPA) and vertical holding appliance (VHA) during swallowing using finite element analysis.

Methods: Head and neck computed tomography (CT) of a patient with levelled and aligned maxillary teeth was taken for a three-dimensional reconstruction. Six models comprising the maxilla, molars, and surrounding periodontal ligament (PDL) with different heights of loop/acrylic pads of the appliances were constructed. A force of 112 g/cm² was applied to the loop/acrylic pads of both appliances to simulate the average tongue pressure. The distribution of von Mises stresses occurring at the PDL due to the tongue pressure was mapped at the cervical area, furcation, distobuccal, mesiobuccal, and palatal root apices. Separately, subjects requiring TPA and VHA at different heights during orthodontic treatment were asked to rate their comfortability with the appliance on the visual analogue scale (VAS).

Results: The VHA demonstrated higher values of stresses at all heights from the palatal floor compared to the corresponding heights of the TPA. The 8 mm model of VHA was found to be functionally effective. This height was also perceived to be acceptable for most patients on the VAS.

Conclusions: The acrylic pad of VHA when kept at a distance of 8 mm from the palatal floor enhances the functional efficiency of the appliance with an acceptable comfortability for the patient.

Keywords: Finite element; Maxillary molars; Stress; Transpalatal arch; Vertical holding appliance.