In the orthodontic literature, randomized clinical trials are used to establish standards for the comparison of different clinical approaches. The balancing effect
produced in a randomized study makes it possible to attribute the differences in results achieved clearly to treatment and not to variations in the biological characteristics
of the patients involved. Recently, most randomized studies in orthodontics have been devoted to testing the hypothesis that some orthodontic appliances exert
orthopedic effects that modify dento-facial growth. The authors propose definitions of “orthopedic effects” and of “dento-alveolar changes” and discuss the difficulties
encountered in measuring them. They also review clinical studies published over the past 10 years on the correction of Class II malocclusions, on the problems
of expansion and also report on Class III disorders. In addition, they assess the problems associated with these clinical studies such as the ethical requirement of
assuring that control groups receive treatment as appropriate for their maladies as that delivered to patients under study, the high cost of carrying them out, the
relatively long delay before results can be evaluated, the difficulties of measuring all the different parameters involved, and the need to assemble large enough samples.
To sum up, one can conclude that, because of all these impediments, randomized clinical studies have not as yet delivered the hoped for benefit of collecting
enough “evidence-based” information for the orthodontic profession to deliver better treatment to its patients.
(Rev Esp Ortod. 2008;38(2):095-108)