We want to thank you for your interest in our recent article dealing with the effectiveness of a sealant in the prevention of white spot lesions in patients undergoing orthodontic treatment (O’Reilly MT, De Jesús-Viñas J, Hatch JP. Effectiveness of a sealant compared with no sealant in preventing enamel demineralization in patients with fixed orthodontic appliances: a prospective clinical trial. Am J Orthod Dentofacial Orthop 2013;143:837-44); this research was conducted by using the National Practice-Based Research Network model. Regarding your concerns, especially with what you termed a lack of standardization, we would point out that our intention was to do the testing under actual private-practice conditions, away from a highly controlled environment. This is at the heart of the practice-centered research philosophy, since it builds on the reality that each orthodontist delivers treatment in a highly personal way. This approach derives its strength in that it allows each practitioner to follow his or her particular preferences because that is what happens every day in our offices. There is always a trade-off between internal validity and external validity in any study, and the concerns you state, although legitimate, only reflect to some extent the internal validity part of the equation. Practice-based research seeks to maximize external validity by looking for maximum generalization of the results in a clinical population while maintaining its internal validity within the bounds of standard clinical practice. The National Practice-Based Research Network concept is so compelling that it was the subject of a recent editorial suggesting that clinical orthodontists should move toward joining such practice-based teams and collaborate in completing randomized controlled trials, like the one we presented.