Factors associated with increased duration of orthodontic treatment: A retrospective cohort study

Orthodontic anomalies can exert a multifaceted impact on individuals, influencing various aspects of their oral and general well-being, thus there is an increasing demand for orthodontic treatment. One of the primary concerns expressed by new orthodontic patients pertains to the expected duration of therapy, thus, this study’s aim was to examine various patient-related and treatment-related factors that contribute to prolonged orthodontic treatment. Materials: This study constitutes a retrospective analysis of clinical records of consecutively treated patients, obtained from a single, private orthodontic clinic. Univariate and multivariable linear regressions were conducted to investigate potential patient-related and treatment-related factors associated with increased orthodontic treatment duration. Results: A total of 357 patients, with a median age of 14 years (IQR: 13, 17), females (n=220, 61.6%), were included. Their orthodontic treatment lasted a mean of 28.5 (SD:10) months. Multivariable linear regression revealed that significant patient-related factors for increased duration are “Angle Class” Class II-Class I (B:4.78; 95%CI: 2.74 to 6.81; P<0.001) and “Impacted” (B:9.68; 95%CI: 5.41 to 13.94; P<0.001), while treatment-related risk factors are “Dental arch” (B:-9.89; 95%CI: -13.14 to -6.64; P<0.001), “Molar appliance” (B:3.05; 95%CI: 0.35 to 5.76; P=0.027) and “Extraction” (B:3.73; 95%CI: 1.52 to 5.94; P=0.001). Further investigation in Class II cases indicated that Class II subdivision exhibits significantly lower treatment duration when compared to Class II non-subdivision (P=0.033). Conclusions: Multivariable linear regression revealed that Angle Class II in comparison to Class I and the presence of at least one impacted tooth are significant patient-related factors of prolonged treatment duration, while orthodontic treatment in both dental arches, the choice of bands over tubes and the inclusion of at least one extraction in the treatment plan are significant treatment-related factors of increased duration. Class II non-subdivision is associated with extended duration compared to Class II subdivision.