Reporting of Sample Size Parameters in Randomized Controlled Trials Published in Prosthodontic Journals

An important consideration in the proper planning of randomized controlled trials (RCTs) is the determination of sample size. A study may fail to answer its research question if the sample size is inadequate, while a large enough sample size may be impractical to implement. The purpose of this study is to describe the reporting of sample size methodology and parameters used in RCTs published in prosthodontic journals.

A MEDLINE search for publications categorized as RCTs was conducted for articles in The Journal of Prosthodontics and The Journal of Prosthetic Dentistry published from 2008 to 2017. The Abstract and Methodology sections of RCTs identified were reviewed, and the following data recorded: reporting of method used to calculate sample size and reporting of parameters used for sample size calculation - type I error (α), type II error (β) or power, minimal clinically relevant difference (MCRD), and variability.

The search strategy retrieved 96 articles; 42 met inclusion criteria for RCTs and were reviewed. Fifty percent (21) of RCTs reported how sample size was determined, but only 17% (7) of RCTs reported all 4 parameters. Type I error (α) was reported in 90% (38) of RCTs, 38% (16) reported power, while only 26% (11) and 12% (5) reported MCRD and variability, respectively.

Methodology and parameters used for sample size determination are inadequately reported in RCTs published in prosthodontic journals.