Effects of force magnitude on torque control in the correction of bimaxillary protrusion with mass retraction

Pulp blood flow changes in maxillary and mandibular anterior teeth after orthodontic retraction: a prospective study

Background

Previous studies of pulpal blood flow (PBF) changes in anterior teeth have been limited in the early phase of orthodontic treatment; less is known about the blood supply of anterior teeth in bimaxillary protrusion patients after orthodontic retraction.

Methods

Fifty bimaxillary protrusion patients (25 orthodontic patients ready for debonding and 25 non-orthodontic patients) were selected as study participants. The PBF of maxillary and mandibular anterior teeth were measured using laser Doppler flowmetry. For orthodontic patients, the PBF was measured at 1 day (T1), 1 month (T2), and 3 months (T3) after fixed appliance removal. Non-orthodontic patient PBF was measured as a control. Cone-beam computed tomography (CBCT) examinations before and after orthodontic treatment were performed for orthodontic patients to measure the root resorption. The anterior teeth in orthodontic group were further divided into subgroups according to root resorption and patient age.

Results

At T1 and T3, PBF changes did not differ significantly between the orthodontic and non-orthodontic groups. Maxillary lateral incisor, maxillary central incisor, and mandibular lateral incisor PBFs at T2 were significantly higher in the orthodontic group (P = 0.048, P = 0.04, and P = 0.021). No significant difference in PBF was found between the root resorption and non-resorption subgroups at any time point. Adolescent patients showed a higher PBF in the maxillary lateral incisor at T2 (12.23 ± 3.48) relative to that at T1 (9.10 ± 3.76) and T3 (9.81 ± 2.80) with statistically significant difference (P = 0.020).

Conclusion

For bimaxillary protrusion patients with four premolars extraction, PBF in the maxillary anterior teeth increased transiently after orthodontic appliance removal and then returned to non-orthodontic levels 3 months later. This effect was more pronounced in adolescents. The PBF of anterior teeth after orthodontic retraction may not be influenced by root resorption.

Methods of Anterior Torque Control during Retraction: A Systematic Review

Background: There are various methods of controlling the inclination of the incisors during retraction, but there is no evidence as to the advantages of some methods over others. The purpose of this systematic review and meta-analysis was to determine the effectiveness of the methods used to control torque during anterior teeth retraction. Methods: In accordance with the PRISMA guidelines, the main research question was defined in the PICO format [P: patients with complete permanent dentition; I: the maxillary incisor torque after (I) and before I retraction with straight-wire appliance and different modes of torque control; O: statistically significant differences in torque values of the upper incisors after orthodontic treatment]. The MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases were searched for keywords combining: retraction orthodontics, torque control orthodontics, torque orthodontics, inclination orthodontics, torque control retraction. The articles were subjected to risk of bias and quality analyses with the ROBINS-I protocol and the modified Newcastle–Ottawa QAS, respectively. Meta-analyses were performed with both fixed- and random-effects models. Results: 13 articles were selected in which total number of 580 subjects took part. In all studies, incisors were retroclined during retraction by 2.46° (mean difference), which was statistically significant. Considering the articles separately, the differences in torque between the study group and the control group were statistically significant in six articles. The Q statistic was 36.25 with p = 0.0003 and I2 = 66.9%, which indicated a high level of study heterogeneity. Conclusion: Both properly performed corticotomy and en-masse retraction using orthodontic microimplants seem to be the most effective and scientifically validated methods of torque control. Further high-quality research is needed to perform better quality analyses and draw more reliable conclusions.

Torque expression by active and passive self-ligating brackets in patients with four premolar extractions: A retrospective study

OBJECTIVE

Appropriate torque expression contributes to ideal treatment outcomes both clinically and aesthetically. Whether active and passive self-ligating brackets (SLBs) have different torque-control capability in vivo has never been reported. The purpose of present study was to explore whether there was difference in torque expression in active and passive SLBs.

SETTING AND SAMPLE POPULATION

In this retrospective study, 225 patients with four first premolar extractions were enrolled. For each patient, the digital lateral cephalometric radiographs were taken before and after treatment.

MATERIALS AND METHODS

The study consisted of 2 groups: 111 subjects were treated with passive SLBs (Damon Q, Ormco) and 114 subjects with active SLBs (Empower 2, American Orthodontics). Measurements to determine skeletal changes and incisor inclination were obtained from cephalometric tracings using Dolphin software (version 11.8, USA). Comparisons in both groups and intergroups were compared using t tests and chi-square test.

RESULTS

Significant differences in the variation of U1-SN(°), U1-NA(°), L1-NB(°) and L1-FH(°) were found between two groups. More labially inclined maxillary incisors were found in active SLB group, while more labially inclined mandibular incisors were observed in passive SLB group.

CONCLUSIONS

With the present prescription set in the two brackets, active SLBs achieved more proclined maxillary incisors and retroclined mandibular incisors. Clinicians should take torque expression of brackets into consideration during orthodontic treatment.