Randomisation essential for preventing invalid, potentially misleading results in restorative dentistry

It has been argued that the randomised controlled trial design is unsuitable for restorative dentistry and that cohort studies or the analysis of large observational datasets without randomisation is more suitable. This opinion article examines why randomisation in clinical trials is needed and why big observational data is not enough for clinical inference.

It may sound plausible, and indeed it may be tempting, to view RCTs in restorative dentistry as something that is too expensive, too slow and rather unhelpful when its results are inconclusive, that is, when they yield no statistically significant results, particularly in the absence of a sufficiently large sample size. In contrast, observational data collected in the 'real world' of dental practice networks seems more appealing, particularly when the results of different restorative treatment types can so easily be compared in simple graphs and tables.However, the expedience of observational studies carries over to other fields as well, and is most certainly not limited to restorative dentistry, and in these other fields, randomised trials are used anyway, despite the added expense. Why is that? The answer is that it is recognised that the results of comparisons of groups formed without randomisation will, in general, have nothing in common with what would reflect the 'real world' in terms of therapeutic truth.

Mickenautsch, S., Berger, V. The role of the randomised controlled trial in restorative dentistry and the correct purpose of observational data. Br Dent J 226, 95–97 (2019). https://doi.org/10.1038/sj.bdj.2019.43