Date of Completion


Embargo Period



Flavio Uribe; Patricia Diaz

Field of Study

Dental Science


Master of Dental Science

Open Access

Open Access


Introduction: Despite major advances in orthodontic tooth movement, orthodontic retention still remains a major problem. It has been estimated that only 10% of the population who have received orthodontics are still in acceptable occlusion as judged by orthodontists 20 years after retention. (Little, Riedel et al. 1988) In addition, very little is known about patient’s perception in relation to orthodontic relapse. Therefore, the goal of this study was to evaluate the efficacy of 3 different types of retainers (Hawley removable, Essix removable and Fixed) of the mandibular and maxillary anterior sextant and to assess patient perception of crowding. Materials and Methods: A retrospective clinical evaluation of 80 patients treated at the University of Connecticut Health Center. These 80 patients were selected 1-2 years into retention based on complete records and consent to participate. Emodels (digital models) taken of the upper and lower arches were assessed pre- and post-orthodontically, and during retention for alignment of the anterior sextant using Little’s Irregularity Index. The amount of Irregularity was compared for 3 retention groups (Hawley, Essix and Fixed). Relapse was also subjectively measured in the form of a questionnaire which was administered to each patient, documenting one's perception of their crowding and the amount of time the retainer was worn. Results: We found a significant increase in the Irregularity Index of the mandibular incisors during retention in patients wearing Hawley retainers compared to the patients that had Fixed retainers. In addition, patients wearing mandibular Hawley retainers perceived their crowding significantly more than patients with Fixed retainers. Only half the patients with overall crowding in the maxillary and mandibular arch, noticed the crowding. Conclusions: Hawley retainers allow for more mandibular incisor movement than Fixed retainers. In addition, the finding that only half the patients with overall crowding actually notice the crowding, may suggest that the Hawley retainer patients may perceive more crowding due to factors unrelated to actual crowding.

Major Advisor

Sunil Wadhwa