Determining condylar bone density in adolescents: An inconclusive cone-beam computed tomographic study

Abstract

In an article in the September issue of the journal, Kim et al attempted to determine the condylar bone density in different age groups and various skeletal patterns. (Kim KJ, Park JH, Bay RC, Lee MY, Chang NY, Chae JM. Mandibular condyle bone density in adolescents with varying skeletal patterns evaluated using cone-beam computed tomography: A potential predictive tool. Am J Orthod Dentofacial Orthop 2018;154:382-9). We appreciate the efforts of the authors and thought it was a great attempt to explore some unknown findings about condylar bone density, but certain points need to be addressed. As mentioned in the text, “The bone density of the mandibular condyle is affected by the functional pressure generated by the occlusion and the mandibular movements that are, in turn, influenced by the properties of the masticatory muscles and age.” Also, “Skeletal pattern is thought to be closely related to occlusal force.” Thus, the authors mentioned that age, sex, and occlusion type (Class I, II, III) affects the condylar bone density. But they do not mention confounding factors, which could alter the results of the study. For example, they did not mention the number of hyperdivergent, hypodivergent, or normovergent cases when the subjects were divided into Classes I, II, and III; the number of cases of hypodivergent subjects in Classes I and II might vary. Facial height ratio (which might be the actual factor responsible for variation of condylar bone density) acts as a confounding factor and can give us biased results. Also, the numbers of boys and girls in the Class I, II, and III groups were not the same, so sex as a confounding factor affects the result. Similarly, when the authors divided the subjects into hypodivergent, normovergent, and hyperdivergent groups, the number of Class I, II, and III cases and the sex of the subjects can act as confounding factors.1Jain S. Debbarma S. Jain D. Bias in dental research/dentistry.Ann Int Med Dent Res. 2016; 2: 2395-2814Google Scholar Nor did the authors mention the different adolescent age groups in the hyperdivergent and Class II groups versus other groups. It is quite possible that the results, which showed higher condylar bone density in Class II and hyperdivergent groups, might be due to a greater number of late adolescent subjects in these groups. Another important point to be noted in the study is that the standard deviation is more than the difference between bone density in different groups.2Jain S. Sharma N. Jain D. Basic fundamentals of designing a quality research.J Adv Med Dent Sci Res. 2015; 3: 88-95Google Scholar The authors did not mention the 95% CIs. P value and CIs are common statistical measures that provide complementary information about probability and conclusions regarding the clinical significance of the study.3Gupta A. Interpreting research findings with confidence interval.J Orthod. 2015; 1: 8Google Scholar Therefore, if we calculate the CIs, the values of the bone density would overlap within different groups and make the results less clinically significant. The value of difference in bone density of the different groups are very close to each other. For example, as mentioned in Table IV, total bone density difference in Class 1 and Class II is just 13 HU; when the samples are improperly distributed in terms of sex or age, that raises questions about clinical significance. Similarly, in Table III, normovergent and hyperdivergent groups have a difference of 21 HU in total bone density. The authors described the results to be statistically significant, but clinical significance of the results is doubtful. Thus, the results can not be held as conclusive as stated in the conclusion of the article. These might be factors causing different bone densities, but again, the results can not be held as conclusive. Mandibular condyle bone density in adolescents with varying skeletal patterns evaluated using cone-beam computed tomography: A potential predictive toolAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 154Issue 3PreviewThe aim of this study was to evaluate the bone density of mandibular condyles in adolescents with varying skeletal patterns using cone-beam computed tomography. The null hypothesis was that there is no difference in the bone density of mandibular condyles in adolescents across various facial height ratios, ANB angle classifications, sexes, and age categories. Full-Text PDF Authors' responseAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 155Issue 3PreviewThank you very much for your interest in our article. We truly appreciate your insightful questions and valuable suggestions. We agree that all of the factors listed can influence condylar bone density, and that they may interact with one another in doing so. Optimally, a full factorial analysis would be conducted on these data. Unfortunately, this type of analysis requires a very large data set. When we attempted to combine predictors, the matrices contained a number of very small groups, and even some empty cells. Full-Text PDF