Elham S. Abu Alhaija; Rami A. Al Shayeb; Susan Al-Khateeb; Hasan O. Daher, Saba O. Daherd
What did the authors aim to do in this study?
The main aim of this study was to investigate and compare the amount and rate of space closure and tooth tipping during the orthodontic space closure in a recent vs healed first premolar extraction site.
How did the authors evaluate?
This randomized controlled clinical trial was performed on 28 subjects. All the patients were treated by upper and lower first premolar extractions using fixed appliances although only the lower arch was included in this study. All the patients were treated with a preadjusted edgewise fixed appliance after the extraction of one right or left lower premolar. All lower teeth were included in the appliance, including second molars. Alignment started with a 0.014-inch nickel-titanium (NiTi) archwire, then with a sequence of 0.018-inch, 0.016 x 0.022-inch and 0.019 x 0.025-inch NiTi archwires, before 0.019 x 0.025-inch Stainless Steel Arch WIre (SSAW) was reached and kept for 1 month before space closure.
After reaching 0.019 x 0.025-inch SSAW and according to subject's random allocation, patients were subdivided into two groups. In the Group 1, it included the right or left lower arch (28 patients). Lower first premolar was extracted before orthodontic treatment (1 week before bond-up) and space closure was carried out into the healed extraction site when 0.019 x 0.025-inch SSAW was reached. Whereas in Group 2, it included the other side of Group 1 patients (28 patients). Lower first premolar was extracted when 0.019 x 0.025-inch SSAW was reached, immediately before space closure. Shifting of the midline was prevented by holding the incisors together on the delayed extraction side using long lacebacks. The same SSAW was used in the lower arch during space closure. Elastomeric power chain from second molar to second molar was used to close lower extraction spaces. Patients were instructed to contact the clinic within 24 hours if any bracket was debonded.
The patients were followed up monthly, at which time the elastomeric power chain was replaced with a new one. On each monthly visit, alginate impressions were taken of the lower arch with no archwire in place. Dental casts were then produced in the laboratory on the same day, using orthodontic stone. Follow-up models of each subject were labeled. A digital caliper was used to measure the width of extraction space on each follow-up model. Two readings (one coronal and one gingival) were obtained from each side. Coronally, space width was measured between two points at the maximum convexity of the lower canine and second premolar. Gingivally, space width was measured between two points on the gingival margin of the canine and second premolar.
The amount of space closure was calculated by sub- tracting values at each time point. The rate of space closure was calculated as space closure achieved in mm/month (3 months). The following time points were defined to measure the amount of space closure.
T1: When reaching 0.019 x 0.025-inch SSAW and just before space closure.
T2: First follow-up (1 month from T1).
T3: Second follow-up (2 months from T1).
T4: Third follow-up (3 months from T1).
A 3-month end point after initial space closure began was chosen for this study because it was previously demonstrated that the extraction socket will be replaced by provisional matrix and immature bone at 8 weeks post extraction.
Differences between the two groups were examined using independent t-test.
What did the authors find?
The extraction of premolars immediately before space closure using a 19 x 25 stainless steel archwire increased the rate of space closure with minimal tipping.
What did the authors conclude?
The study revealed that the amount and rate of space closure in the lower arch at a recent extraction site was greater than that of a healed extraction socket, with similar amounts of tipping that was observed in both the groups.
What do we think about it?
The most important concern that any patient has about orthodontic therapy is the duration of the treatment. In today's fast moving world, everyone wants quick results and many techniques hence developed to cater the same to the needs of the patients. But one of the most simple yet efficient method to enhance the rate of space closure was to carry out the extraction right before the retraction was begun. This study shows us the comparison of extractions that were carried out before and after the levelling and aligning, with evident results stating that better space closure was observed when extraction was done after.
This is because the injury that was inflicted at the site induces the Regional Acceleratory Phenomenon [RAP]. This phenomenon is a tissue reaction to a noxious stimulus that increases the healing capacities of the affected tissues. Hence, at a cellular level, this enhances the activation of the basic multicellular units (BMUs), thereby increasing the remodeling of the bone, which causes an increase in the rate of tooth movement. Along with this, as there is absence of newly formed bone, there is reduced physical resistance for space closure. All these factors combined together aid in reducing the treatment duration.
As all the comparisons in the study were done in the same patient on either side, it eliminated most of the confounding factors that can effect the results. Although they used the friction mechanics for space closure, the results cannot be generalised for all kinds of orthodontic therapies. But it cannot be denied that this method enhances the rate of space closure in patients.
Abu Alhaija ES, Al Shayeb RA, Al-Khateeb S, Daher HO, Daher SO. A comparative assessment of the amount and rate of orthodontic space closure toward a healed vs recent lower premolar extraction site. Angle Orthod. 2022 Jul 1;92(4):463-470.
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