We read with great interest the article entitled “Quantitative and qualitative assessment of anchorage loss during en-masse retraction with indirectly loaded miniscrews in patients with bimaxillary protrusion” (Monga N, Kharbanda OP, Samrit V. Am J Orthod Dentofacial Orthop 2016;150:274-82). This article concluded that in clinical situations when directly loaded miniscrews are not preferable, indirect miniscrew anchorage could be a viable alternative to direct anchorage. However, we still have a few questions regarding this study.
This retrospective clinical study only included 18 patients with bimaxillary protrusion who were treated with miniscrew-supported anchorage. However, as depicted by the authors, previous related studies also incorporated a conventional anchorage group to assess the anchorage loss of different anchorage strategies. Can the authors explain more clearly why the control group or conventional anchorage group was not considered? Also, the included patients of this retrospective study were chosen from a database of 89 patients. Were these patients consecutively started or finished, or were only those “with excellent results” included? Otherwise, there could be some selection bias.
The tooth movement in the vertical plane was measured from the mesial cusp tips of molars or incisal edges to the palatal and mandibular planes by passing through the root apex. Although it is technically correct to refer to these lines, however the distance changes of these lines actually reflect total tooth movement, both sagittally and vertically, because, first, these lines are not perpendicular to the horizontal plane (eg, Frankfort plane), and, second, the tipping movement of both molars and incisors would also confound the reported vertical changes. Therefore, did the authors ever consider the horizontal plane as the reference plane for vertical movement changes?
As Table III showed, in terms of anteroposterior position changes, the crown of the maxillary first molar (1.27 ± 0.82 mm) moved more mesially than that of the apex root (1.10 ± 0.94 mm), whereas more apex root mesial movement (1.43 ± 1.06 mm) was found compared with crown movement of the mandibular first molar (1.07 ± 0.87 mm), indicating that different tipping was induced by indirect miniscrew anchorage. However, similar distal tipping was found in terms of angular change for maxillary (−2.43° ± 3.12°) and mandibular first molars (−0.03° ± 4.28°). Can the authors explain more clearly the different results presented by 2 parameters?
The miniscrews were placed after the leveling and aligning phase of treatment as depicted in the study, which was common practice in orthodontic clinics. However, we still have 1 more interesting question: do you think placing the miniscrews before leveling and aligning will be better for anchorage control, since anchorage loss is also observed during the leveling and aligning phases?