We want to thank Robert Vitral, Marcio Campos, and Marcelo Fraga for their interest and feedback regarding our research. They analyzed our 2 null hypotheses and stated that 1 was already rejected before the study began.
The null hypothesis in question was “that no significant difference would exist between the Class II and Class I sides for skeletal and dental measurements of Class II subdivision malocclusions.” From previous studies, it has been shown that there are significant differences in dental measurements, but for skeletal measurements it has been unclear. It could be related to the dentition, the skeleton, or a combination of both. The word “could” is the key to this statement. Skeletal discrepancies could play a role, but based on previous studies they have not been shown to be significant unless there was an underlying craniofacial syndrome (which we excluded from our sample).
Vitral and his colleagues also mentioned that “the skeletal component in the dentoalveolar asymmetries has already been widely studied and discussed.” The previous studies referenced in our introduction used different methodologies to examine Class II subdivision malocclusions with 2-dimensional radiography and measurements. These studies showed tendencies toward skeletal differences but no statistically significant differences. The studies did not quantify how much of the overall asymmetry was caused by dental vs skeletal asymmetries. The skeletal component has been looked at before, but the previous authors suggested that the skeletal aspects should be investigated more in depth.
Vitral and his colleagues were correct in stating that “the great merit of our study was to evaluate skeletal structures with cone-beam computed tomography.” We were expecting to see dental differences in our measurements but still decided to include the dental aspect in our null hypothesis for 2 reasons: first, to test whether our new methodology with cone-beam computed tomography and 3-dimensional measurements would confirm the dental differences shown in the previous studies (ie, validation), and second, to be able to quantify how much of the total discrepancy is derived from dental asymmetry vs skeletal asymmetry. We do not disagree that we could have formulated a null hypothesis on skeletal asymmetries alone, but since we were using a different methodology, and also to make the study more complete, we decided to incorporate the dental asymmetries as well.
The only other study that shows significant skeletal asymmetries in Class II subdivision malocclusions is by Sanders et al in 2010. They also used cone-beam computed tomography to analyze this malocclusion and showed some skeletal asymmetries in the mandible. Our research supports some of their findings and contributes new findings for skeletal asymmetries. Our study was completed before their article was published, so it was exciting to find that both of our methodologies found some statistically significant skeletal asymmetries that were not detected or significant in the prior studies that used 2-dimensional images.