Orthodontic Treatment and External Apical Root Resorption: A Study on the Worldwide Prevalence - A Scoping Review.

External apical root resorption (EARR) is an important concern in orthodontic practice. Despite extensive research, the reported prevalence, occurrence, and grade distribution of EARR remain heterogeneous, ranging from 0% to 100%. This review aimed (i) to analyse the available scientific evidence worldwide to ascertain conclusions regarding EARR prevalence and (ii) to identify and evaluate the most appropriate radiographic technique and complete/comprehensive assessment method for EARR. This review followed the JBI and PRISMA guidelines and included studies of any orthodontic treatment. The studies were analysed based on diagnostic imaging methods, quantification, categorisation, and other variables. Of the 1209 records identified, 81 studies were included. The evidence originated from six continents, predominantly Europe (33 studies), Asia (23 studies), and the Americas (13 studies from North America and 16 from South America). Across the studies, marked variability was observed in both the reported prevalence and the severity of EARR. Studies utilising two-dimensional techniques mainly reported no or only mild resorption in most incisors. Similarly, studies employing three-dimensional techniques found that mild or no resorption was predominant. However, severe EARR was rare in all studies, consistently affecting fewer than 5% of cases. Notably, discrepancies in severity and mean EARR values among studies were largely attributable to variations in techniques and classification systems. This inconsistency emphasises the urgent need for standardised diagnostics and a unified classification. Resolving these issues will provide clearer insights into EARR.