# Evaluation of the Distortion of Essix Retainer Formed From Biostar Machine Using Intraoral Digital Scans: An In Vitro Study

## TL;DR

This study evaluates how much Essix retainers distort over time using digital scans, finding more distortion in the back teeth area.

## Contribution

The study introduces a novel in vitro method to assess Essix retainer distortion using intraoral digital scans over six months.

## Key findings

- Distortion in Essix retainers increased over time, especially in the posterior region.
- Posterior distortion ranged from 0.133 mm at one month to 0.304 mm at six months.
- Anterior distortion remained relatively low, increasing from 0.057 mm to 0.068 mm over six months.

## Abstract

Introduction

Retention is essential to prevent unwanted tooth movement due to growth changes, to allow the gingival and periodontal tissues affected by orthodontic treatment to realign, and to stabilize teeth that have been moved to potentially unstable positions, thus reducing the risk of relapse. This study aimed to evaluate the distortion of Essix retainers over time to enhance their retention and stability.

Methods

Patients who visited the Department of Orthodontics and Dentofacial Orthopedics at Ranjeet Deshmukh Dental College & Research Centre, Nagpur, India, after completing their orthodontic treatment were included in the study, according to the established inclusion and exclusion criteria. A total of 26 patients participated. Each patient received an Essix retainer fabricated from a Duran+ Biostar round sheet (1 mm thickness) using a Biostar machine based on their post-debonded maxillary cast. The patients were instructed on the correct insertion and removal of the Essix retainer. The inner surface of the retainers was scanned at one month, three months, and six months using an intraoral digital scanner. These scans were analyzed and compared for distortion at different time intervals using Medit software.

Results

The Essix retainers exhibited varying degrees of distortion at different time intervals. Notably, distortion was more significant in the posterior region compared to the anterior region. Additionally, distortion increased over time, with the least amount observed at one month and progressively worsening by the sixth month. Specifically, the average distortion in the posterior region ranged from 0.133 mm after the first month to 0.304 mm after six months. In contrast, the average distortion in the anterior region was lower, ranging from 0.057 mm at one month to 0.068 mm at six months.

Conclusions

Distortion was more pronounced on the posterior surface of the Essix retainer compared to the anterior region.