Photoelastic analysis of stress generated by Connecticut Intrusion Arch (CIA).

Alessandro Schwertner,Renato Rodrigues De Almeida,Marcio Rodrigues De Almeida,Alcides Gonini Jr

doi:10.1590/2177-6709.22.1.057-064.oar

Abstract

ABSTRACTObjective: The present in vitro study evaluated, by means of the photoelastic technique, the effects generated by the Connecticut Intrusion Arch (CIA), with a 90o bend on the distal surface of molar tubes and using the 4 x 2 appliance on the anterior and posterior regions of the upper dental arch. Methods: Five models were manufactured, in which two different clinical situations were correlated: 1) use of intrusion arch not cinched back and transpalatal bar for anchorage (Group 1); 2) use of intrusion arch cinched back and transpalatal bar for anchorage (Group 2). Stress generated in the apical and middle regions of tooth roots of maxillary anterior teeth and maxillary first molars was evaluated.Results: Taking a reference value of 1.0 MPa = 100%, qualitative descriptive analysis was performed, which showed uniformity between stress values in the apical region of anterior teeth of both groups (G1 and G2). In the posterior region, for models with the arch cinched back (G2), stress remained within 100%. As for G1 models (with the arch not cinched back), variations in the mesial surface of first molars were observed, with an increase of 20% in the generated stress. The apical region did not undergo any changes, while in the distal region of molars there was a decrease of 20% in stress.Conclusion: Laboratory results revealed differences in stress between Groups 1 and 2 in the molar region, thereby indicating that there was a tendency towards mesial root tipping of first molars when the distal end of the CIA was not cinched back.

Highlights

The 4 x 2 appliance is considered a versatile appliance, with easy adaptability and high tolerance for orthodontic treatment in the mixed dentition
Based on the mean standard deviation obtained in both groups for the eight points (0.24 MPa), adopting an alpha error of 5% and adjusting for non-parametric tests by means of the Asymptotic Relative Efficiency (ARE) — technique advocated by Randles and Wolfe28 — a sample size of n = 5 in each group presented an 80% power to detect a minimum difference of 0.6 MPa among the mean values of groups
Studies, such as the present research, investigating intrusion and photoelasticity to elucidate the distribution of forces, different mechanics, and root anatomy, are of great importance for orthodontists when evaluating and determining the risk of root resorption for patients

Summary

Introduction

The 4 x 2 appliance is considered a versatile appliance, with easy adaptability and high tolerance for orthodontic treatment in the mixed dentition. In addition to being used for alignment and leveling of maxillary and mandibular incisors, it is used for retraction of incisors in cases of Class II, Division 1 malocclusion, uprighting of incisors in cases of Class II, Division 2 malocclusion, and for minimizing diastemas while gaining space for permanent canines It assists on correcting the overbite associated with distalization of first molars during application of intrusive mechanics.[1,2] Overbite correction is one of the greatest challenges faced by orthodontic treatment.[3] Depending on diagnosis and treatment goals, overbite can be treated with intrusion of mandibular and/or maxillary incisors, extrusion of the posterior segment, or a combination of both.[4,5]. This is because the caudal angle is located on the mesial surface of the molar tube (resulting in an extrusive effect with a clockwise moment), establishing a statically determined system.[10,11]

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Results

Conclusion