Long-term changes in overjet in individuals with and without orthodontic treatment

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.