# Predictability of Deep Bite Correction and Curve of Spee Flattening in Clear Aligner Therapy: An Open-Label and One Arm Retrospective Study

## TL;DR

This study shows that clear aligners are less predictable for deep bite correction and lower Curve of Spee flattening compared to upper Curve of Spee flattening.

## Contribution

The study provides new insights into the predictability of clear aligner therapy for specific orthodontic corrections.

## Key findings

- Overbite correction achieved only 55% of the expected outcome with a significant difference (p = 0.0001).
- Lower Curve of Spee flattening achieved 62% of the expected change, while upper Curve of Spee reached 86%.
- ICC values showed good predictability for upper Curve of Spee but moderate for overbite and lower Curve of Spee.

## Abstract

Objectives: This study aims to evaluate the predictability of Clear Aligner Therapy (CAT) in deep bite correction and Spee Curve flattening by comparing final intraoral scans with planned outcomes in ClinCheck. Methods: STL files from pre-treatment, post-treatment (first aligner cycle), and planned final positions of 18 patients (12 females; 6 males; mean age 30.9 ± 12.3 years) were analyzed. The software Medit Link (version 3.4.4) was used to measure overbite as the vertical distance between the incisal edges of the maxillary and mandibular central incisors and the Curve of Spee in both arches by drawing a reference line between the most distal molar and the central incisor on each side, recording the perpendicular distance from the distal cusp. Measurements were repeated on post-treatment and ClinCheck STL files. Data analysis was performed using a Student’s t-test (p = 0.05) to compare the expected and actual measure variations and intraclass correlation coefficient (ICC) to assess aligner predictability. Results: A significant discrepancy was observed in overbite correction (55% achieved), with a significant difference between expected and actual outcomes (p = 0.0001). Moderate differences were noted for the lower Spee Curve (62% achieved), while the upper Spee Curve showed 86% of the expected change. ICC values were moderate for overbite and lower Spee Curve, and good for the upper Spee Curve. Conclusions: ClinCheck overestimates deep bite correction. Upper Curve of Spee flattening is highly predictable, while the lower curve flattening has lower predictability.