American Journal of Orthodontics and Dentofacial OrthopedicsVolume 133, Number 1

Readers’ forum 7

operator has knowledge of the prosthesis, implant, or suturebeing placed in a patient.

Moreover, a design with several operators would haveresulted in greater variability because of differences in han-dling and application of materials such as bracket bondingand wire engagement, as well as differences in determiningtreatment stages.

The discussion about adequate sample size and largestandard deviation is typical of the first-year statistics seminarin a graduate orthodontic curriculum and should not beanalyzed in a scientific periodical of the caliber of theAJO-DO. For the record, large standard deviations might be aproblem when no statistical significance is shown.1 Since, inour project significant associations were noted, no furtherinvestigation was undertaken.

The introduction of clinical research on a large scale inorthodontics seems to generate new challenges for graduateorthodontic education. This was realized in medical disci-plines also; a recent study evaluated the medical residents’understanding of biostatistics and research results, with only37% of the responders interpreting correctly adjusted oddsratios from a multivariate regression and even fewer (10%),the results of a Kaplan-Meier analysis.2

Apparently, the only way to deal with demanding re-search requirements is to emphasize the importance of statis-tics as a cornerstone of modern orthodontic education.

Theodore EliadesAthens, Greece

Am J Orthod Dentofacial Orthop 2008;133:6-70889-5406/$34.00Copyright © 2008 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2007.11.006

REFERENCES

1. Piantadosi S. Clinical trials: a methodological perspective. 2nd ed.Hoboken, NJ: Wiley & Sons; 2005.

2. Windish DM, Huot SJ, Green ML. Medicine residents’ under-standing of the biostatistics and results in the medical literature.JAMA 2007;298:1010-22.

Author’s responseI want to thank Dr Razavi for his comments and critique

of the study design in my recent article (Miles PG. Self-ligating vs conventional twin brackets during en-masse spaceclosure with sliding mechanics. Am J Orthod DentofacialOrthop 2007;132:223-5). Dr Razavi stated that because “thearchwire cannot slide toward the faster side, . . . space closureis achieved symmetrically, making the slower side . . . therate-limiting factor in space closure.” He is concerned thatusing a posted wire eliminates the ability to discern fastermovement on 1 side of the arch from the other.

This methodology—using a posted wire and en-masseretraction—was selected according to the Damon system; asDr Razavi correctly points out, the anterior portion of thearchwire cannot slide to either side past the soldered posts/

hooks. Although the soldered posts prevent the anterior

portion of the wire from sliding, this does not affect the rateof posterior space closure. We have 3 possible scenarios toachieve space closure: (1) teeth distal to the extraction sitemove mesially faster if there is less friction, (2) the midline/archform skews to the side with lower friction, or (3) bothoccur. In all cases, the space closes faster on the side with lessfriction—if friction is a major determinant in the rate of toothmovement. Because we found no difference in the rate ofspace closure (and although not reported, I noted no arch ormidline skewing), it suggests to me that the physiology wasthe major determinant in the rate of tooth movement, andfriction was not. However, if we had ligated with modules orchain, perhaps we would have found a difference. If we wereto retract the canines as Dr Razavi suggests, I suspect that wewould similarly find no difference, unless again we created a“critical mass” of friction by tying modules or chain over thecanine as it is retracted. However, this would be the subject ofanother investigation.

I thank Dr Razavi for his thoughtful critique, and Iappreciate the opportunity to clarify these issues.

Peter MilesCaloundra, Queensland, Australia

Am J Orthod Dentofacial Orthop 2008;133:70889-5406/$34.00Copyright © 2008 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2007.11.007

Authors’ responseWe appreciate very much the kind remarks by Moham-

mad R. Razavi regarding our article on self-ligating brackets,and we commend him on his application and synthesis of ourideas about the future of self-ligating brackets, and hisintegration of an active and passive system, as it would beapplied to the SmartClip bracket system.

Daniel J. RinchusePeter G. Miles

Pittsburgh, Pa, and Caloundra, Queensland, AustraliaAm J Orthod Dentofacial Orthop 2008;133:70889-5406/$34.00Copyright © 2008 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2007.11.008

ObesityThe article in the May issue, “Obesity in adolescence:

implications in orthodontic treatment” (Neeley W, GonzalesDA. Am J Orthod Dentofacial Orthop 2007;131:581-8), wasa good review of a topic that was, until now, unexplored inorthodontics. However, the authors did not mention the effectof obesity on the quality and the properties of bone, factorsthat affect many orthodontic treatment considerations, includ-ing amount of orthodontic forces, the time taken to initiatetooth movement, bite-opening requirements such as extrusionof posterior teeth or intrusion of incisors, and relapse tenden-cies due to the soft tissues of the craniofacial complex and theretention protocol. Any modifications required in the mech-

anotherapy for these patients should be known.

American Journal of Orthodontics and Dentofacial OrthopedicsJanuary 2008

8 Readers’ forum

Also, information about the effects on orthodontic treat-ment of any medications or hormonal therapy the patient istaking that could contribute to obesity or treating it is lacking.

Answers to these questions are needed for incorporationinto academic and clinical schedules for providing the best

Sandeep GoyalMurad Nagar, Ghaziabad, India

Am J Orthod Dentofacial Orthop 2008;133:7-80889-5406/$34.00Copyright © 2008 by the American Association of Orthodontists.

treatment to these patients. doi:10.1016/j.ajodo.2007.11.014