We appreciate the interest in our article (Flórez-Moreno GA, Isaza-Guzmán DM, Tobón-Arroyave SI. Time-related changes in salivary levels of the osteotropic factors sRANKL and OPG through orthodontic tooth movement. Am J Orthod Dentofacial Orthop 2013;143:92-100), and we want to clarify the concerns about the methodology for readers. Based on a previous review article, the letter stated that current ELISA techniques are not very sensitive. However, the review cited included only studies using ELISA techniques with lower sensitivity than those we used. For example, the assay used by Zhao et al had a sensitivity of 1.6 pg per milliliter for the minimum detectable dose for RANKL, and the test conducted by Jørgensen et al had a detection limit of 62.5 pg per milliliter for OPG. In contrast, we outlined in the “Material and Methods” section that the concentrations of RANKL and OPG were measured by new, highly sensitive ELISA techniques developed by Immunodiagnostic Systems for soluble RANKL (detection limit of 0.4 pg/mL or 0.02 pmol/L) and for OPG (detection limit of 2.8 pg/mL or 0.14 pmol/L). These assays measure the total levels of sRANKL and OPG in the samples, including not only the unbound forms, but also the sRANKL-OPG complex.
For the use of saliva instead of gingival crevicular fluid as a sampling method, currently a number of articles support the use of this oral fluid for determining analytes in the periodontal microenvironment, therefore providing a sensitive and inexpensive detection technique that could be useful in monitoring molecular responses in patients having orthodontic treatment.
Finally, also based on the same review, the authors of the letter argue that no reference ranges were established. Due to the descriptive nature and explorative character of our study, and taking into account that the validity of salivary sRANKL and OPG reference values can be established only by testing a large number of subjects, this point was not considered. Hence, the results should be interpreted in the context of each patient’s treatment phase and compared with simultaneous measurements in the patient’s gingival crevicular fluid in further studies.