<p>The Index For Preventive and Interceptive Orthodontic Treatment Needs (IPION) was developed to assess early orthodontic treatment needs (EOT) in mixed dentition. This scoping review aimed to map the extent, characteristics and nature of the existing evidence on the development of IPION and its application in identifying the prevalence of EOT and malocclusion in mixed dentition. This scoping review also investigated the reported IPION modifications, limitations and gaps in literature. Following PRISMA-ScR guidelines, a scoping review of the literature was conducted in July 2025 across 4 databases (EBSCO, Proquest, Pubmed, Scopus, Web of Science) and additional sources (journal reference list). Eligible sources include population-based and institutional observational studies which applied the IPION among children between the ages of 6 to 12 years. Data were extracted and literature was reviewed by 5 independent reviewers using a predefined extraction template and the findings were synthesized narratively. Twelve of 47 identified records (1999 to 2025) from North America, Asia, and Africa were included. EOT prevalence ranged from 20 to 96% across institutional and population-based studies. IPION modifications across different studies included modifications on the assessments of caries, overbite, overjet, missing permanent incisors, IPION component categories and addition of IPION score for 12-year-olds. Limited studies evaluated the validity of these modifications. There is a growing application of the IPION in evaluating the prevalence of EOT and malocclusion in mixed dentition. Future research is warranted to address its limitations and enhance its utility as a comprehensive epidemiological instrument.</p>