Impact of dentofacial development on early mandibular incisor crowding

•Mandibular incisor crowding from the mixed to the permanent dentition was evaluated.•Incisor crowding decreased from the mixed to the permanent dentition.•Crowding threshold of 2 mm in the mixed dentition was not a significant predictor of self-correction.•Incisor crowding improvement was mainly explained by greater initial crowding and leeway space.•Incisor protrusion and maxillary width increase also contributed to crowding improvement.

IntroductionIn this retrospective longitudinal study, we evaluated the influence of dentofacial development on mandibular incisor crowding from the early mixed dentition (T1) to the early permanent dentition (T2).MethodsThe sample was selected from 1212 longitudinally followed untreated subjects. Cephalometric radiographs and dental casts of 42 subjects (mean age, 8.66 years) with mandibular incisor crowding were evaluated at T1 and T2. Dentoskeletal variables were compared, and their influence on crowding changes was estimated. The sample was divided regarding incisor crowding severity (≤2 mm and >2 mm) and behavior (improvement and worsening), and the variables with a significant influence on the crowding changes were compared between the groups (P <0.05).ResultsIncisor crowding decreased from T1 to T2. The crowding changes were influenced by the amount of initial crowding, leeway space, incisor protrusion, and maxillary width increase. Crowding of 2 mm or less was not a good predictor for self-correction, with similar chances for improvement or worsening.ConclusionsIncisor crowding reduction can be expected from the early mixed to the early permanent dentition. The potential for crowding reduction was associated with greater initial incisor crowding, leeway space, incisor protrusion, and maxillary width increase. A crowding threshold of 2 mm was not a valid borderline condition to define the self-correction prognosis.