Comparing Two Classification Methods of Third Molar Development

Abstract

BACKGROUND: Radiographic evaluation of third molar development is often used in estimating chronological age. A widely used system of such an evaluation, developed by Demirjian, uses eight growth stages (Demirjian et al. 1973). These stages are defined by changes of shape and can be subjective (Sisman et al. 2007). A new staging system uses numeric values (millimeters) to separate the stages (Hammer 2015). OBJECTIVE: The purpose of this study is to determine if Hammer’s staging of third molar development is more reliable than Demirjian’s staging. MATERIALS AND METHODS: Existing panoramic radiographs from University of Minnesota Orthodontic Department were scored twice by three calibrated readers using Hammer and Demirjian Staging Classifications. Kappa statistics were calculated to assess intra- and inter-rater agreement. RESULTS: The results showed that Hammer’s method had higher intra- and inter-rater reliability, but is not significantly different from Demirjian’s method. CONCLUSION: Hammer’s classification of third molar eruption pattern may be used to stage third molar formation. Future studies may aim to correlate Hammer’s classification with population-specific chronological age data.