The authors used standardised procedures to assess the relevance and validity of the included studies, and described the validity assessment and data extraction in some detail. However, while the research question was clearly defined, the authors included data that did not relate to this research question. Most of the studies included in the review focused on secondary care, although the stated focus was primary care. The authors acknowledged that the findings may not be generalisable to general dental practice, but inserting figures from secondary care may confuse the issue.
The authors searched a number of bibliographic databases without applying any language restrictions. However, the strategy used to search for unpublished material may have been limited: apart from one study brought to the reviewers' attention by an expert in the field, the authors do not appear to have searched for unpublished studies. As the only study with a primary care focus was unpublished, the review may have benefited from a broader search for unpublished literature.
The authors did not identify studies on the effectiveness of toluidine blue dye in primary care and, consequently, concluded that toluidine blue dye is not effective in primary care. However, a lack of research on the topic does not demonstrate that the dye is ineffective, so this conclusion should be interpreted with caution. A conclusion that there was insufficient evidence to assess the effectiveness of toluidine blue dye as an adjunct to visual examination in primary dental care may have been more valid. Finally, the cost data were based on the reviewers' own assumptions and calculations, rather than trials or other studies.