First, I want to thank Hisham Badawi and Paul Major for taking time to respond to my editorial (Turpin DL. In-vivo studies offer best measure of self-ligation. Am J Orthod DentofacialOrthop 2009;136:141-2). Their statements show a level of professionalism that is not always easy to maintain when one is teaching, conducting original research, and maintaining a practice. Although I do some teaching, I am not running a research laboratory or a private practice—and I still find it difficult to satisfy the reasonable demands of our many readers for a new editorial each month, written with clarity and understanding. I will try again to make myself understood regarding the issue of in-vitro and in-vivo studies.

Drs Badawi and Major are correct in stating that their 3-dimensional orthodontic force measurements should not be compared with the in-vitro shear bond strength study of adhesives; the AJO-DO quit accepting new in-vitro bonding studies about a year ago, when we realized that the relationship of the findings to patient treatment was fleeting, at best. Since then, we have tended to look more carefully at all in-vitro studies. Perhaps a better analogy would be the study of static friction done by pulling a straight wire through a series of brackets in a typodont to determine which brackets provide the most resistance to tooth movement. These types of in-vitro studies teach us little about actually aligning teeth in the mouth and tend to have little value for clinicians.

I share Drs Badawi and Major’s interest in obtaining a deeper understanding of the biologic principles of tooth movement resulting from complex force systems, with the goal of transferring what is learned through in-vitro studies to the clinical environment. It is challenging to weigh the benefits of a 3-dimensional environment that is devoid of muscles, bone, and, most of all, a periodontal ligament. Perhaps their approach will shortcut the trial-and-error method of testing treatment modalities and biased “expert” opinions. They are certainly correct in noting that “it is the inappropriate interpretation of these research findings into clinical practice” that must be guarded against.