Objectives: To describe the use of historical controls in orthodontic literature by contrasting comparative and follow-up studies and to analyze trends of use before and after the AAOF legacy project launch.
Methods: Both electronic and manual searches were conducted. Three independent reviewers assessed the studies for inclusion and the criteria were: human subjects of any age, sex, and ethnicity; at least one of the nine AAOF legacy collections were used either as main sample population or as comparison/control; and assessed orthodontic outcomes. Two customized data abstraction forms were used to obtain data from comparative and follow-up studies. Data were analyzed using STATA version 14.2.
Results: A total of 201 (129=follow-up studies, 72= comparative studies) studies were included. Comparative studies: The most commonly utilized growth study collection was the Michigan Growth sample. The number of published studies more than doubled after the AAOF legacy collection initiation in 2009. The increase continued through 2010-14, during which there was a trend to use multiple collections. Follow-up studies: The Burlington Growth collection was the most commonly utilized. The overall use of the legacy collection showed a small increase in the number of published studies post-2009.
Conclusion: The overall number of published studies in the comparative and follow-up categories increased post-2009, reflecting the efforts of the AAOF team and collection curators in making the records available worldwide. This study provides a snapshot of the legacy collections’ utilization. Further research should consider studying each collection to identify utilization predictors.