Mandibular second premolar distoangulation: a longitudinal follow-up from the mixed to the permanent dentition

The aim of this study was to assess the frequency of mandibular second premolar (MnP2) distoangulation among orthodontic patients and the angular changes after a longitudinal follow-up.

The sample was collected from the orthodontic records of 865 patients. The distoangulation group was composed of 42 patients (mean age 9.29 ± 1.24 years, 16 male, 26 female) with distoangulation of MnP2. The control group was composed of 32 patients (mean age 9.38 ± 1.10 years, 15 male, and 17 female) without distoangulation of MnP2. Panoramic radiographs taken in the mixed (T1) and the early permanent dentition (T2) were analyzed in both groups. Longitudinal angular changes (distal angle θ and premolar-molar angle γ), degree of root formation, second premolar depth, and prevalence of associated dental anomalies were analyzed. Intergroup comparison was performed with Mann-Whitney, t-tests, and chi-square tests (P < 0.05).

The prevalence of MnP2 distoangulation in the mixed dentition was 4.85%. The distoangulation group showed a smaller initial distal angle (59.34o ± 8.41) when compared to control group (79.88o ± 7.60). The spontaneous eruption of the MnP2 with distoangulation was observed in 76.57% of the sample. MnP2 distoangulation was significantly associated with agenesis of its antimere, small maxillary lateral incisors, and deciduous molar infraocclusion.

Severe cases of MnP2 distoangulation were absent in this study.

The frequency of MnP2 distoangulation among orthodontic patients was 4.85%. Mild to moderate distoangulated Mnp2 spontaneously uprighted from the mixed to the permanent dentition. Small lateral incisors, second premolar agenesis, and infraocclusion of deciduous molar were frequently found in cases with MnP2 distoangulation.