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Dr. Giuseppe Perinetti comments on Dr. Nozomi Maeda, et al.'s article (pps. 194-203) in CRANIO's July, 2011 issue.
Article Type:
Letter to the editor
Bias (Statistics) (Reports)
Occlusion (Dentistry) (Research)
Leg length inequality (Research)
Perinetti, Giuseppe
Contardo, Luca
Pub Date:
Name: CRANIO: The Journal of Craniomandibular Practice Publisher: Chroma, Inc. Audience: Academic Format: Magazine/Journal Subject: Science and technology Copyright: COPYRIGHT 2011 Chroma, Inc. ISSN: 0886-9634
Date: Oct, 2011 Source Volume: 29 Source Issue: 4
Event Code: 310 Science & research

Accession Number:
Full Text:
Dear Editor:

I am writing to comment on the paper entitled: "Effects of experimental leg length discrepancies on body posture and dental occlusion" by Maeda, et al. that just appeared in CRANIO (July, 2011). (1) This is a controlled study showing that immediate effects of experimental leg length inequality exist on both body posture and dental occlusion. At first glance, the study appears interesting and well conducted, but after a more accurate reading, one wonders if the interpretation of the results can be truly considered unbiased, or if important aspects related to the correlations between the masticatory system and body posture have been missed.

The investigations on such correlations are both relatively recent and still controversial. However, a few years ago systematic reviews (2-4) were published with the aim of pointing out limitations of current research and suggesting future improvements/directions. In 2009, our group published one of these systematic reviews (3) that uncovered the fact that about half of the current publications were negative, and failed to find any significant correlation. While negative studies carry the same dignity as positive ones (and should be quoted in any paper as well), this piece of evidence leaves all questions about the true existence of such correlations open. Moreover, our analysis (3) initially uncovered major methodological limitations of published studies, such as the lack of a method error analysis of the parameters used to measure aspects of the body posture or dental occlusion. Indeed, the degree of correlations seen in most of the positive studies, although statistically significant, are little and there is no proof that they are beyond the systematic/random errors encountered. In this view, endeavors to overcome current methodological limitations are necessary to avoid ambiguous or contrasting results.

Finally, the existence of correlations at a biological level, and their potential clinical relevance (3,5) need to be considered, along with how they relate to two distinct aspects that must not be confused. Therefore, while a correlation may be detected experimentally, this does not mean that it will have a clinical relevance. Only if the correlations reach a clinically significant grade would the diagnosis and the consequent treatment plan have to take such aspects into account. However, this concept is missed in most of the published literature (including the above-mentioned study), (1) with a few exceptions. (3)

Therefore, in consideration that none of the abovementioned reviews or negative studies have been discussed or cited, the conclusions in the paper by Maeda, et al. might suffer from bias. Moreover, whether these correlations are clinically relevant or limited to a biological level is still far from being clearly demonstrated.

Giuseppe Perinetti, D.D.S., Ph.D.

Luca Contardo, D.D.S., M.S.

Trieste, Italy

Dr. Nozomi Maeda, et al.'s response to Drs. Giuseppe Perinetti and Luca Contardo.

Dear Editor:

Our distinguished colleagues are quick to accuse bias in our interpretation of the data without elaborating on what they see as biased. Data was presented and the statistics done in a standard, unbiased way. We would have appreciated some elaboration on the correlations we have missed. We are still trying to understand what they are concerned about beside the fact that their names were not included in our references. This field is still experimental, and, as was mentioned in our paper, many areas showed no correlation. Our paper was clear in presenting both positive and negative correlations.

Moreover, it is very obvious that our colleague was quite upset that we did not quote his group's study in our research. We would like to point out that their publications came around the same time our paper was in publication. Our references included both sides of the argument, and we feel that it is up to the readers to decide what may or may not be of clinical relevance. It will take a few more research projects to prove a solid correlation pattern and many more to establish clinical applications. Our research simply presents a pattern, as measured by accurate computerized equipment. It is intended to present data, and to open a discussion regarding its clinical relevance. We look forward to future research in the area.

Kiwamu Sakaguchi, D.D.S., Ph.D.

Nozomi Maeda, D.D.S., Ph.D.

Atsuro Yokoyama, D.D.S., Ph.D.

Sapporo, Japan

Noshir R. Mehta, D.M.D., M.D.S., M.S.

Emad F. Abdallah, D.M.D., M.S.

Albert G. Forgione, B.D.S., M.S.

Boston, Massachusetts
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