Outwardly the rhetorical organisation of sections of research reports in different disciplines can appear similar. Close examination, however, may reveal subtle differences. Numerous studies have drawn on the genre-based approach developed by Swales (1990, 2004) to investigate the schematic structure of sections of articles in a range of disciplines. Dentistry does not appear to have attracted this kind of research interest. The present study examined discussion sections of articles in Dentistry with reference to a schematic framework of discussion sections in Applied Linguistics. Steps in "commenting on results" moves were closely examined to understand how arguments about the meaning and significance of results in the Dentistry discussions were constructed. Findings showed the discussion sections could largely be accounted for in terms of moves and steps in the framework (thus indicating a broadly similar rhetorical organisation) and they revealed two patterns of argumentation in commenting moves, one not reported in previous genre-based research. Findings from the study are discussed in relation to disciplinary variation. The study provides a genre-based description of discussion sections of articles in Dentistry and suggests that analysis of steps, sub steps and sequences within moves can be a useful focus for genre-based investigation of disciplinary norms. (Contains 2 figures and 2 tables.)