Decalcification and tooth clustering

READERS’ FORUM

Letters to the editor* Developing our role as ‘‘clinical biologists’’ Three articles recently published in the AJO-DO by Davidovitch and Krishnan,1 Bartzela et al,2 and Turpin3 are refreshing encouragements to increase our clinical and research knowledge base to provide better orthodontic results. One can only marvel at the quantum leaps in orthodontic results achieved from communication and research with oral surgery, periodontics, and prosthodontics. We need to expand communication and research with colleagues who share our common interests, including genetics, orthopedics, pediatrics, internal medicine, endocrinology, and so on. The concepts of biology, pathophysiology, and pharmacology are all deeply related and intertwined. A full knowledge of biology is needed to understand how mechanotherapy works and whether pathophysiology exists. Knowledge of pathophysiology is needed to understand whether orthodontic benefits are hindered or how pharmacology can help achieve a more normal biologic state. Knowledge of pharmacology is needed to understand how orthodontic treatment can be positively or negatively affected. We should cherish the role of ‘‘clinical biologists’’ that has been bestowed on us. Our specialty needs to enthusiastically develop this role from university research departments to private clinical practices. We need to fully expect and monitor each patient’s biologic response from orthodontic mechanics. Current and future research will describe cellular proteins that are responsible for bone growth, tooth movement, and root resorption.1 Once these proteins are found, pharmacology will add to our knowledge base and treatment options. DNA recombinant techniques are now routinely used to manufacture drugs—beneficial human proteins—from bacteria.4 Just around the corner, genetic and pharmacology studies are promising. Gene silencing techniques (2006 Nobel Prize, Physiology/Medicine) might use RNA interference drugs to alter the production of destructive proteins.5,6 Gene modification of DNA might be able to treat genetic disorders (2007 Nobel Prize, Physiology/Medicine).7 Each orthodontist’s unique skills can be synergistic to our specialty’s progression. Increasing innovation, knowledge, and communication will deliver dramatic benefits to our specialty and patients that we could have only dreamed of in decades past. Having a true obligation to uplift our specialty will make our future bright, but we must eagerly prepare ourselves for the uphill climb. Let’s see how many shoulders we can stand on and how far we can reach! Are you ready? James J. Zahrowski Tustin, Calif Am J Orthod Dentofacial Orthop 2009;135:558 0889-5406/$36.00 Copyright Ó 2009 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2009.03.020 * The viewpoints expressed are solely those of the author(s) and do not reflect those of the editor(s), publisher(s), or Association.

558

REFERENCES 1. Davidovitch Z, Krishnan V. Role of basic biological sciences in clinical orthodontics: a case series. Am J Orthod Dentofacial Orthop 2009;135:222-31. 2. Bartzela T, Turp JC, Motschall E, Maltha JC. Medication effects on the rate of orthodontic tooth movement: a systematic literature review. Am J Orthod Dentofacial Orthop 2009;135:16-26. 3. Turpin DL. Medications weigh-in on tooth movement. Am J Orthod Dentofacial Orthop 2009;135:139-40. 4. Watson JD, Myers RM, Caudy AA, Witkowski JA. Recombinant DNA, genes and genomics a short course. 3rd ed. New York: W.H. Freeman; 2005. 5. Fire A, Nirenberg M, Krishnarao A. RNA interference technology: from basic science to drug development. Cambridge, UK: Cambridge University Press; 2005. 6. Stevenson M. Therapeutic potential of RNA interference. N Engl J Med 2004;351:1772-7. 7. Manis J. Knock out, knock in, knock down —genetically manipulated mice and the Nobel Prize. N Engl J Med 2007;357:2426-9.

Decalcification and tooth clustering I read with interest the recent in-vivo study of demineralization (Ghiz MA, Ngan P, Kao E, Martin C, Gunel E. Effects of sealant and self-etching primer on enamel decalcification. Part II: an in-vivo study. Am J Orthod Dentofacial Orthop 2009;135:206-13). I was disappointed that the authors’ statistical analysis did not appear to take into account the clustering of teeth in the mouth.1 A tooth surface is not an independent unit for statistical purposes, because it is subject to similar conditions as the surrounding teeth. In split-mouth studies, such as this one, the analysis should be undertaken by quadrant or arch (ie, was there demineralization on any tooth in the quadrant or arch in which the experimental material was used compared with the control material?). In parallel group studies then, the statistical unit is the patient. This means that the effective sample size is reduced, and therefore more patients must be recruited, but an appropriate analysis will greatly assist in determining the effectiveness or otherwise of these materials. Philip Benson Sheffield, United Kingdom Am J Orthod Dentofacial Orthop 2009;135:558 0889-5406/$36.00 Copyright Ó 2009 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2009.03.013

REFERENCE 1. Blance A. Not necessarily strength in numbers, more a case of size does matter! J Orthod 2008;35:67.

Author’s response We agree with the observation of Dr Philip Benson. Because a split-mouth technique was used in this study, with