Variability in Measurement Techniques and Terminology for Maximum Mouth Opening in Oral Submucous Fibrosis: A Critical Review of Methodological Inconsistencies

Abstract Introduction: Oral submucous fibrosis (OSF) causes progressive restricted mouth opening and functional impairment. Maximum mouth opening (MMO) is a critical outcome measure, but a lack of standardised measurement techniques and terminology hinders comparison across clinical trials. This study evaluates the methodological rigour and homogeneity of MMO measurement in a representative OSF literature. Materials and Methods: The present study analysed 72 OSF treatment trials, extracting data on measurement instruments, terminology, and procedural reporting. Inconsistency was defined as inadequate uniformity in terminology, instruments, procedural details, clinical adjustments, or reporting clarity of MMO measurements. Related data were extracted and analysed using descriptive statistics and the Kruskal–Wallis test. P ≤ 0.05 was taken as significant. Results: Significant heterogeneity was observed in measurement instruments, with Vernier callipers being the most commonly used (43%). Terminology varied, with inter-incisal distance being the most frequent (73%). Methodological reporting was poor: 86% of studies failed to cite references for their technique, 82% did not address missing teeth, and the mean description length was brief (26.9 ± 17.3 words). Discussion: The lack of standardisation in MMO measurement techniques and terminology poses challenges for comparing outcomes across studies. Detailed reporting of measurement protocols, including instrument calibration and patient positioning, is essential for improving reproducibility and reliability in OSF research. Findings are limited by exclusive reliance on published data without protocol registration. Conclusion: Standardisation of MMO measurement techniques and terminology is crucial for advancing OSF research and improving patient outcomes. Future studies should adopt comprehensive guidelines to ensure methodological rigour and reproducibility.