Discrepancies between actual and expected orthodontic treatment duration with pre-adjusted edgewise fixed appliances: A case-control study of factors associated with treatment delays

Objectives: To explore the prevalence of discrepancies between estimated and actual orthodontic treatment duration and identify predictors of treatment delays. Material and methods: A total of 96 patients (62.5% female; age = 15.6 ± 6.8 years) who completed an orthodontic treatment with pre-adjusted edgewise fixed appliances between 2015 and 2023 were retrospectively included. Differences between actual and estimated treatment duration >3 months were classified as discrepancies and categorized as "overestimation" or "underestimation." Such discrepancies were compared on demographics, COVID period, and orthodontic parameters using Student's t-tests and chi-square tests, as appropriate. Predictors of underestimated treatment duration were assessed with logistic regression analysis. Results: Actual treatment duration significantly differed from the estimated duration (26.5 ± 9.6 vs. 21.6 ± 3.6 months; P <0.001), with 65.6% cases exhibiting treatment discrepancy (P = 0.003) and 61.5% of them being underestimated (P = 0.032). Cases with underestimated durations more commonly displayed posterior crossbite (30.9% vs. 5.4%; P = 0.004), larger SNA angle (83.7 ± 3.7 vs. 78.8 ± 3.8; P = 0.005), bracket debonding (53.4% vs. 31.4%; P = 0.039; odds ratio [OR] = 2.51, 95% confidence interval [CI] = 1.04-6.04), and were most likely conducted during COVID period (33.9% vs. 10.8%; P = 0.011; OR = 4.23, 95% CI = 1.31-13.62) compared to overestimated ones. Posterior crossbite (P = 0.006) and COVID period (P = 0.007) were significant predictors of treatment underestimation. Conclusions: Approximately two-thirds of orthodontic treatments showed discrepancies between estimated and actual duration, with 61.5% being underestimated especially in presence of posterior crossbite and during COVID period.