A critical appraisal of the systematic review process: Systematic reviews of zirconia single crowns

Statement of problem Systematic reviews analyze the data of published research in an effort to assemble the scientific evidence to help clinicians apply evidence-based information in decision making. The quality of systematic reviews varies greatly. Purpose The purpose of this study was to critically appraise the current systematic review process by evaluating systematic reviews that pertain to zirconia-based single crowns. Materials and methods The following PICO (patients, intervention, comparison, outcome) question was formulated: “In adults, how does the long-term prognosis of zirconia-based single crowns compare with conventional single crowns on natural teeth?” An electronic search was performed in PubMed and the Cochran Library for articles published in English between 1950 and October 2012. Additional manual searches were completed. To be included in the analysis, the study must have been a systematic review, published in an English-speaking peer-reviewed journal, and evaluated zirconia crowns on teeth. Two examiners qualitatively evaluated the publications with an Assessment of Multiple Systematic Reviews checklist and the Oxford Systematic Review Appraisal form. Results Three systematic reviews were identified that met the search criteria. Two studies met 5 of the 11 Assessment of Multiple Systematic Reviews criteria, whereas the third met only 1 criterion. The same 2 studies met 3 of the 5 Oxford Systematic Review Appraisal criteria and the third met only 2 criteria. Conclusion Because of the variation in methodologies, systematic reviews should be interpreted cautiously. The Assessment of Multiple Systematic Reviews Checklist and the Oxford Systematic Review Appraisal Sheet are practical tools for appraising and determining the quality of systematic reviews.