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J Periodontol. 1998 May;69(5):521-7.

Equivalence and superiority testing in regeneration clinical trials.

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Department of Periodontics, Virginia Commonwealth University, Richmond, USA.


The purpose of this report is to investigate sample size requirements for both equivalence and superiority studies investigating products used in regeneration. The goal of a superiority clinical trial is to determine if a new therapy is superior to an established therapy or placebo. In contrast to superiority trials, equivalence trials are used to determine if a new product has similar therapeutic properties to an established product. The sample sizes for the two different types of clinical trials were based on the following assumptions: an alpha of 0.05, a power of 0.80, a 2 group parallel arm study, and equal variances and sample sizes for both groups. Separate sample size calculations were done for both intrabony defects and Class II furcation defects. Sample sizes for the equivalence and superiority trials using the same criteria were the same. However, criteria for estimating sample sizes for equivalence clinical trials require much smaller differences between groups, resulting in much larger sample sizes. A criterion of a 20% difference between groups of the total therapeutic effect resulted in sample sizes which ranged from 64 to 127 in equivalence clinical trials. These samples sizes are much larger than have been generally used in clinical trials investigating periodontal regeneration.

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