Defining progression in erosive tooth wear: an interpretive challenge

Objectives To critically evaluate current approaches to longitudinal erosive tooth wear (ETW) monitoring and examine whether quantitative intraoral scanner (IOS)-based measurements and conventional clinical indices can be meaningfully compared in defining progression. Materials and methods A systematic review identified longitudinal studies evaluating ETW using IOS-based quantitative approaches alongside conventional clinical assessment methods. MEDLINE, Embase, Scopus, and Web of Science were searched from database inception to January 2026, with grey literature sources also searched. The electronic database searches were updated in August 2026 using the original search strategies. Reference-list screening and forward citation tracking were undertaken alongside both the initial search and the updated search. Results Five longitudinal studies met the eligibility criteria. IOS-based approaches consistently detected measurable surface change over time, including during relatively short follow-up intervals in which conventional clinical indices frequently demonstrated no categorical progression. Substantial heterogeneity existed in progression thresholds, outcome measures, superimposition methodologies, and reporting strategies. Agreement between IOS-derived measurements and conventional index scores was variable and generally weak to moderate. IOS quantifies continuous dimensional change, whereas clinical indices categorise severity using ordinal scales. No validated framework was identified linking quantified dimensional surface loss to clinically meaningful ETW progression. Conclusions Quantitative IOS measurements and conventional clinical indices assess different dimensions of tooth wear and cannot currently be interpreted as directly interchangeable measures of progression. Validated frameworks linking quantitative surface loss to biological and clinical relevance are required. Clinical relevance IOS enables high-resolution longitudinal quantification of tooth surface change, but the clinical significance of detected change remains uncertain. Establishing clinically meaningful progression thresholds is essential for integrating quantitative digital monitoring into routine care.