Introduction to cumulative meta-analysis in dentistry: lessons learned from undertaking a cumulative meta-analysis in periodontology.

Improving health and well-being from the consideration of isolated studies is problematic. Systematic reviews have been developed to address this problem and may include a quantitative data synthesis in the form of a meta-analysis, or a cumulative meta-analysis. The value of systematic reviews depends greatly on the availability and quality of the results of primary research. The objective of the current project was to demonstrate the technique of cumulative meta-analysis in dentistry using data from a previously published systematic review. The process highlights an issue that some trials could not be synthesized due to the lack of reporting of measures of variation. This represents a potential source of bias. Investigators are encouraged to consider their trials as part of an information continuum and to report sufficient detail to permit the trials' incorporation into subsequent syntheses.