Preventive and Interceptive Orthodontic Treatment Needs in Early and Late Mixed Dentition: An IPION-Based Assessment in Children

Background/Objectives: Mixed dentition is critical for identifying developing malocclusions that may benefit from preventive or interceptive orthodontic management. This study aimed to assess IPION-defined preventive/interceptive orthodontic treatment need using the Index of Preventive and Interceptive Orthodontic Needs (IPION), compare early and late mixed dentition, and evaluate associated clinical findings. Methods: This single-center cross-sectional study included 200 children attending their first examination at the university Pediatric Dentistry and/or Orthodontics clinics: 100 aged 6 and 100 aged 9 years. IPION-defined treatment need was assessed using the age-specific IPION-6 and IPION-9 subsystems. Dental, developmental, and occlusal findings were recorded using standardized criteria. Treatment-need categories and clinical findings common to both subsystems were compared between groups, while total IPION scores were summarized separately by age. Relationships of caries and premature primary tooth loss with IPION scores were evaluated. Results: Definite treatment need predominated (58.0% vs. 51.0%), and treatment-need distributions differed between age groups (p = 0.047). Dental caries, molar relationship, overjet, and overbite showed significant differences. In 6-year-olds, carious and prematurely lost tooth counts were positively correlated with IPION scores, with the strongest relationship for premature tooth loss (ρ = 0.609; p < 0.001). Relationships were weaker in 9-year-olds. Conclusions: IPION-defined preventive/interceptive orthodontic treatment need was common within this university-based clinical sample across mixed dentition stages. Differences in treatment-need distribution and clinical findings indicated distinct preventive and interceptive orthodontic profiles across mixed dentition stages. Age-specific IPION assessment may support identification of children who may benefit from further orthodontic evaluation by integrating dental, developmental, and occlusal findings.