Learning objectives

  • Explain intention-to-treat
  • A randomized controlled trial (RCT) comparing a new non-steroid antiinflammatory drug (NSAID) against a placebo reported that the NSAID did not cause more gastrointestinal side effects than the placebo. Upon reading the paper, you notice that as many as 30% of the study participants in the NSAID group switched over to the using the placebo.

    Do you trust this conclusion? What would be a proper way of analyzing the outcomes?


    Randomized controlled trials (RCTs) often suffer from two major complications: noncompliance and missing outcomes. One potential solution to this problem is a statistical concept called intention-to-treat (ITT) concept. ITT analysis avoids overoptimistic estimates of the efficacy of an intervention resulting from the removal of non-compliers by accepting that noncompliance and protocol deviations are likely to occur in actual clinical practice.

    Learning objectives

  • Explain rationale and weaknesses of subgroup analyses
  • You read in the below meta-analysis that bruxism may contribute to implant failure. However, you want to learn more if the complications are biologic (related with implant) or mechanical (related with prosthesis or other mechanical failures).

    A critical appraisal of a systematic review: Zhou Y, Gao J, Luo L, Wang Y. Does bruxism contribute to dental implant failure? A systematic review and meta-analysis. Clinical Implant Dentistry and Related Research 2015 doi: 10.1111/cid.12300 Article first published online: 2 March 2015.

    You have to refer the subgroup analysis for outcomes.

    Learning objectives

  • Explain ARR – absolute risk reduction, RRR - relative risk reduction, NNT numbers needed to treat
  • Your patient with severe periodontitis has a history of smoking 1 pack/day. Besides dental treatment, you recommend smoking cessation, but is unsure what the most effective intervention is. You make search the website of the Cochrane collaboration and find systematic review on nicotine replacement therapy with conclusions. You read that nicotine replacement therapy increased cessation rates with a number needed to treat (NNT) of 15, yielded an absolute risk reduction (ARR) of 2%. Smoking cessation was consistently associated with a reduction in tooth loss risk. However, many of the words in the conclusion of the SRs are difficult to understand. Being the treatment provider you need to understand these terms so you can discuss with your patient the effectiveness of different options to help her stop smoking.

    Although systematic reviews provide the highest level of evidence, do you know how to critically appraise a SR? There is necessity to learn the meaning of ARR, RRR,NNT