# Long-term changes in overjet in individuals with and without orthodontic treatment: A 30-year cohort study

## TL;DR

A 30-year study found that orthodontic treatment reduces overjet but does not lower dental injury risk or tooth decay scores.

## Contribution

This study provides long-term evidence on the effectiveness of orthodontic treatment in reducing overjet and its impact on dental health outcomes.

## Key findings

- Orthodontic treatment significantly reduced overjet over 30 years.
- Larger initial overjet was associated with higher odds of traumatic dental injury.
- No significant difference in DMFT scores was found between treated and untreated groups.

## Abstract

Large overjet increases the risk of traumatic dental injury (TDI). This study, part of the Münster Long-Term Study (MLS), aimed to investigate long-term changes in overjet with or without orthodontic treatment and to evaluate whether correcting large overjet can reduce Decayed, Missing, and Filled Teeth Index (DMFT) scores of maxillary incisors.

Eligible for inclusion in this longitudinal cohort study (MLS) were 667 primary school children who underwent two systematic orthodontic examinations between 1981 and 2001 (T0). Data collection at follow-up in 2022–2023 (T1) included a clinical examination and intraoral scans to evaluate overjet, DMFT, TDI and orthodontic treatment history. Participants were divided into treated and untreated groups. Statistical analysis included Mann–Whitney U tests and paired t‑tests, with significance set at α = 0.05.

A total of 73 participants could be enrolled in the follow-up: 50 treated (female/male: 27/23; mean age 38.3 ± 5.1 years) and 23 untreated (female/male: 10/13; mean age 39.1 ± 6.0 years). The mean observation period was 30.0 ± 5.3 years. At T0, the mean overjet was significantly larger in the treated group than in the untreated group (4.0 ± 1.78 mm vs 2.6 mm ± 0.79, p = 0.002). The treated group showed a significant reduction in overjet from T0 to T1 (p < 0.001), while changes in the untreated group were not significant (p = 0.601). At T1, differences in overjet between groups were no longer significant (p = 0.105) and there was no significant difference in DMFT scores of the maxillary incisors (p = 0.276). TDI of the anterior teeth occurred in 30.0% (n = 15) of the treated group and in 8.7% (n = 2) of the untreated group at T1. Logistic regression analysis showed that each millimeter increase in overjet at T0 was associated with 47% higher odds of TDI (odds ratio 1.47, 95% CI 1.05–2.13).

Orthodontic treatment can effectively improve overjet in the long-term. However, it did not reduce DMFT scores of the maxillary incisors in this MLS sample.