We read with interest the article of Dr Kim et al reporting on a new technique for molar uprighting (Kim MH, Kim M, Chun YS. Molar uprighting by a nickel-titanium spring based on a setup model. Am J Orthod Dentofacial Orthop 2014;146:119-123). Some points need further consideration or correction.
The authors presented the case records for 2 patients. The patient in case 1 had a missing mandibular right first molar. We wondered whether it is right to extract an intact third molar, consequently upright the second molar, and prescribe an implant for the missing first molar, when orthodontically we are able to protract the second and third molars to solve the edentulous space problem. The latter approach will eliminate 2 surgeries: a minor surgery for installing the miniscrew and a more invasive one for the implant fixture. Furthermore, the prognosis of a natural tooth is much better and longer than any implant. As shown in Figures 1, 5, and 6 cited in their article, in case 1, there was a narrow space between the second molar and the first premolar. Thus, the malocclusion could be easily improved by using only fixed orthodontic devices without an implant fixture.
In case 2, uprighting a mesially inclined left second molar when the third molar is absent can be achieved by using a removable orthodontic appliance with a finger spring inserting a distal force to the target tooth. This technique is less expensive and more comfortable to the patient.
A round 0.014-in nickel-titanium wire is superelastic and does not have enough rigidity for uprighting a molar to the desired position. The uprighting force was inserted buccally at a distance from the center of resistance (rotation) of the molar, and regarding the high resiliency of the mentioned wire, the molar will rotate around the center of rotation mesially out and distally in. This aberration can be even seen in Figure 5 in their article. On the other hand, this light superelastic wire can be so easily distorted by functional forces. As the authors mentioned in their study, when a flexible wire is deformed by a food bolus, the spring serves as an unwanted V bend, and the operator should be cautious about this issue for early replacement of the deformed spring.
Today, temporary skeletal anchorage devices are at the center of innovations and considerations. The number of studies introducing novel techniques with miniscrews and miniplates are growing too fast in the literature. However, these anchorage devices should be used only when no simpler approaches are available. In fact, they should be used to simplify the orthodontic procedure.