Stability of maxillary anterior teeth during retention and 1 year after removal of retention-an RCT on adolescents retained with two different bonded retainers and a vacuum-formed retainer

BACKGROUND

Maxillary bonded and removable retainers maintain teeth in correct positions following orthodontic treatment. There is insufficient evidence regarding the capacity of the retention methods to stabilize the maxillary teeth both during and after retention.

OBJECTIVE

To evaluate retention capacity and 1-year post-retention changes in the irregularity of maxillary anterior teeth and single anterior tooth contact point discrepancy (CPD) of two bonded and one removable retention method.

TRIAL DESIGN

Three-arm parallel group single-centre randomized controlled trial.

METHODS

Ninety adolescent patients treated with fixed orthodontic appliances were enrolled. After gaining informed consent, the patients were randomized in blocks of 30 by an independent person into one of three groups: A) bonded retainer 13-23; B) bonded retainer 12-22; and C) removable vacuum-formed retainer. The primary outcomes were changes in Little's irregularity index (LII) and single CPD measured on digitalized casts before retention (T1), after 2 years of retention (T2), and 1-year post-retention (T3).

BLINDING

The digital casts were blinded for the outcome assessor.

RESULTS

Data on all 90 patients were analysed according to intention-to-treat principles. Changes in LII during retention were 0.3 mm in group A, 0.6 mm in group B, and 1.0 mm in group C. No significant differences between the groups were seen (P > 0.05). Changes during post-retention were 1.1 mm in group A, 0.5 mm in group B, and 0.4 mm in group C. Group A showed more significant changes than groups B and C (P = 0.003). During the whole post-treatment period, no significant differences were shown between the groups (P > 0.05). CPD did not differ significantly between the groups at any point.

HARMS

Three patients showed changes of LII over 3 mm or CPD over 2 mm during the post-retention period, and two accepted to be realigned.

LIMITATIONS

The trial was a single-centre study evaluating 1-year post-retention changes.

CONCLUSIONS

The changes were clinically insignificant during and after the retention period. Thus, all three methods showed equal retention capacity.

TRIAL REGISTRATION

www.clinicaltrials.com (NCT04616755).

Cost analysis of two types of fixed maxillary retainers and a removable vacuum-formed maxillary retainer: a randomized controlled trial

Background

There has been an increased interest in conducting healthcare economic evaluations. Also, orthodontic treatments have gathered focus from an economic point of view, however orthodontic research seldom examines both clinical and economic outcomes.

Objective

To evaluate and compare the costs of three retention methods: a bonded retainer to the maxillary four incisors, a bonded retainer to the maxillary four incisors and canines, and a removable vacuum-formed retainer (VFR) in the maxilla. The null hypothesis was that there was no difference in costs for the three types of retention methods.

Trial design

Three-arm, parallel group, single-centre, randomized controlled trial.

Materials and methods

Ninety adolescent patients, 54 girls and 36 boys, treated with fixed or removable retainers in the maxilla, were recruited to the study. The patients were randomized in blocks of 30, by an independent person, to one of three groups: bonded multistranded PentaOne (Masel Orthodontics) retainer 13-23, bonded multistranded PentaOne (Masel Orthodontics) retainer 12-22, and removable VFR. A cost analysis was made regarding chair time costs based on the costs per hour for the specialist in orthodontics, and material costs plus any eventual costs for repairs of the appliance. Changes in Little’s irregularity index and in single contact point discrepancies (CPDs) were measured on digitalized three-dimensional study casts. Data were evaluated on an intention-to-treat basis. The analysis was performed at 2 years of retention.

Results

No statistically significant difference in costs between the maxillary fixed retainers and the VFRs was found, however, the material and emergency costs were significantly higher for the VFR compared with the bonded retainers. All three retention methods showed equally effective retention capacity, and no statistically significant differences in irregularity or CPDs of the maxillary anterior teeth in the three groups was detected.

Limitations

It was a single-centre trial, and hence less generalizable. Costs depended on local factors, and consequently, cannot be directly transferred to other settings.

Conclusions

All three retention methods can be recommended when considering costs and retention capacity.

Trial registration

NCT04616755.

Orthodontic retention: what's on the horizon?

Orthodontic retention remains one of the great challenges in orthodontics. In this article, we discuss what is on the horizon to help address this challenge, including biological approaches to reduce relapse, treating patients without using retainers, technological developments, personalised medicine and the impact of COVID-19 on approaches to orthodontic retention.

Stability of maxillary anterior teeth after 2 years of retention in adolescents: a randomized controlled trial comparing two bonded and a vacuum-formed retainer

BACKGROUND

Retention of the maxillary anterior teeth is commonly recommended to maintain the teeth in their corrected positions. Both fixed and removable retention methods are used, but the certainty of evidence is low.

OBJECTIVE

To evaluate post-treatment changes in irregularity of the maxillary six anterior teeth and single tooth contact point discrepancy (CPD) of three different retention methods.

TRIAL DESIGN

Three-arm parallel group single-centre randomized controlled trial.

MATERIALS AND METHODS

Ninety patients, 54 girls and 36 boys, were recruited to the study. The inclusion criteria were adolescent patients treated with fixed appliances at least in the maxilla. After gaining informed consent from the patient and their custodians, the patients were randomized to one of three groups: bonded retainer 13-23, bonded retainer 12-22, and removable vacuum-formed retainer (VFR) covering the maxillary teeth including the second molars. The randomization, prepared by an independent person, used blocks of 30. The primary outcomes were changes in single CPD and Little's irregularity index (LII) measured on digitalized three-dimensional study casts before and after 2-year retention. The study casts were anonymized before assessment and the changes were blinded for the assessor. Data were evaluated on an intention-to-treat basis. Thus, all randomized patients were incorporated into the final analysis.

RESULTS

The LII and CPDs increased slightly in all three groups without any statistically significant differences between the groups. The VFR group showed a small intercanine width increase and some more changes of canine rotations than in the other groups.

HARMS

No harm was observed in any subjects and none of the patients needed retreatment.

LIMITATIONS

The trial was a single-centre study and short-term changes were evaluated.

CONCLUSIONS

All three retention methods showed equally effective retention capacity and all the changes found in the three groups were small and considered clinically insignificant. Thus, the null hypothesis was confirmed. All three methods can be recommended.

TRIAL REGISTRATION

NCT04616755.

Comparison of post-treatment changes with and without retention in adolescents treated for maxillary impacted canines-a randomized controlled trial

Objective

To evaluate whether retention is needed after orthodontic treatment of impacted maxillary canines.

Trial design

Two-arm parallel group single-centre randomized controlled trial.

Materials and methods

Sixty-three patients, 39 girls and 24 boys, were recruited to the study. The inclusion criteria were patients with at least one impacted or unerupted maxillary canine, and moderate irregularity of the maxillary six anterior teeth according to Little’s index (LI). After gaining informed consent from the patient and their custodians, the patients were randomized to one of two groups, i.e. to a non-retention group or a retention group. The randomization process was prepared and carried out by an independent person not involved in the trial and the randomization used blocks of 20 (10 + 10). Primary outcomes were changes in single contact point discrepancy, and LI measured on digitalized three-dimensional study casts 1-year post-treatment. The study casts were anonymized before assessment and the changes were blinded for the assessor. Data were evaluated on an intention-to-treat basis. Thus, all randomized patients were incorporated into the final analysis. In the non-retention group a 10-week interim period was used to detect patients who eventually have a relapse immediately after treatment. If so, the patient got the arch-wire reinserted. Most patients in the retention group received a vacuum-formed retainer and pretreatment spacing cases got a bonded retainer.

Results

Mean irregularity change was 0.4 mm in the retention and 1.3 mm in the non-retention group (P < 0.001). Maximum change was 2.5 mm in the retention and 3.2 mm in the non-retention group (P < 0.001). Most changes in the non-retention group occurred during the 10-week interim period. In the non-retention group, one patient developed contact point discrepancy of >2 mm during the interim period and was realigned.

Harms

One patient met the stopping guideline criteria. This patient had the arch wire reinserted for 2 months. After realignment, the patient received a retention appliance.

Limitations

The trial was a single-centre study and short-term changes were evaluated.

Conclusions

Changes between the retention and the non-retention group were statistically but not clinically significant. Since satisfactory clinical results 1-year post-treatment were found in the non-retention group, retention does not appear to be needed. The 10-week interim period was useful in detecting patients who might have a relapse immediately after treatment.

Trial registration

The trial was not registered.

Pattern and amount of change after orthodontic correction of upper front teeth 7 years postretention

OBJECTIVE

To investigate the amount and pattern of changes of maxillary front teeth 7 years postretention, which previously were retained with a bonded retainer.

MATERIALS AND METHODS

The study group consisted of 27 patients. Study models before treatment (T1), at debonding (T2), 1 year after removal of the upper bonded retainer (T3), and 7 years postretention (T4) were present. The irregularity index (sum of contact point displacements) and the rotations of front teeth toward the raphe line were calculated.

RESULTS

The irregularity index of the maxillary front teeth changes very little or not at all during the first year postretention. Further change long term resulted in an irregularity index of mean 2.0 (range 0.0-5.8). The contact relationship between the laterals and centrals seems to be the most critical. Forty rotated teeth in 21 patients were corrected more than 20 degrees . Mean relapse during the first year postretention was 6.7 degrees (range 0.0 degrees -14.7 degrees ). Mean changes during 7 years was 8.2 degrees (range 0.0 degrees -19.3 degrees ).

CONCLUSIONS

Relapse of upper front teeth retained with a bonded retainer is minor in both the short and long term. If permanent retention is required after 3 years of retention, it is enough to retain the incisors.

Relapse tendency after orthodontic correction of upper front teeth retained with a bonded retainer

OBJECTIVE

To investigate the amount and pattern of relapse of maxillary front teeth previously retained with a bonded retainer.

MATERIALS AND METHODS

The study group consisted of 135 study casts from 45 patients. Recordings from study models before treatment (T1), at debonding (T2), and 1 year after removal of the retainer (T3) were present. All patients had been treated with fixed edgewise appliances. The irregularity index (sum of contact point displacement [CPD]) and rotations of front teeth toward the raphe line were calculated at T1, T2, and T3.

RESULTS

The mean irregularity index at T1 was 10.1 (range 3.0-29.9, SD 5.4). At T2 it was 0.7 (range 0.0-2.1, SD 0.7), and at T3 it was 1.4 (range 0.0-5.1, SD 1.2). Fifty-five teeth in 42 patients were corrected more than 20 degrees between T1 and T2 (mean correction 31.4 degrees range 20.0-61.7), and mean relapse in this group was 7.3 degrees (range 0.0-20.5). Regarding alignment of the maxillary front teeth, the contact relationship between the laterals and centrals seems to be the most critical. A significant positive correlation was found between the amount of correction of incisor rotation and the magnitude of relapse but not between the amount of correction of CPD and the magnitude of relapse. Eighty-four percent of the overcorrected CPDs returned to a desired position.

CONCLUSIONS

Minor or no relapse was noted at the 1-year follow-up.

Relapse tendency after orthodontic correction of upper front teeth retained with a bonded retainer

OBJECTIVE

To investigate the amount and pattern of relapse of maxillary front teeth previously retained with a bonded retainer.

MATERIALS AND METHODS

The study group consisted of 135 study casts from 45 patients. Recordings from study models before treatment (T1), at debonding (T2), and 1 year after removal of the retainer (T3) were present. All patients had been treated with fixed edgewise appliances. The irregularity index (sum of contact point displacement [CPD]) and rotations of front teeth toward the raphe line were calculated at T1, T2, and T3.

RESULTS

The mean irregularity index at T1 was 10.1 (range 3.0-29.9, SD 5.4). At T2 it was 0.7 (range 0.0-2.1, SD 0.7), and at T3 it was 1.4 (range 0.0-5.1, SD 1.2). Fifty-five teeth in 42 patients were corrected more than 20 degrees between T1 and T2 (mean correction 31.4 degrees range 20.0-61.7), and mean relapse in this group was 7.3 degrees (range 0.0-20.5). Regarding alignment of the maxillary front teeth, the contact relationship between the laterals and centrals seems to be the most critical. A significant positive correlation was found between the amount of correction of incisor rotation and the magnitude of relapse but not between the amount of correction of CPD and the magnitude of relapse. Eighty-four percent of the overcorrected CPDs returned to a desired position.

CONCLUSIONS

Minor or no relapse was noted at the 1-year follow-up.

Receptor tyrosine kinase inhibition suppresses growth of pediatric renal tumor cells in vitro

PURPOSE

Children who undergo standard therapy for renal tumors are at an increased risk for treatment sequelae such as congestive heart failure, abnormal trunk development, and secondary malignancies. Therefore, research on the use of novel chemotherapeutic agents with fewer side effects is justified. Recent experimental evidence suggests that growth factor receptors such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR) play an important role in growth and development of pediatric renal tumors especially that of Wilms' tumor. In this study we investigated the effects of genistein, AG1478, and AG1295, from the class of growth factor receptor tyrosine kinase (GFR-TK) inhibitors, on proliferation and colonigenic growth of 2 pediatric renal tumor cell lines.

METHODS

The authors studied the effect of genistein (broad-spectrum GFR-TK inhibitor), AG1478 (EGFR-specific GFR-TK inhibitor), and AG1295 (PDGFR-specific GFR-TK inhibitor) on proliferation and colonigenic growth of rhabdoid tumor of the kidney and Wilms' tumor cell lines: G-401 and SK-NEP-1, respectively. The effect of genistein at concentrations of 0 to 200 micromol/L, and AG1478 and AG1295 at 0 to 10,000 nmol/L were tested on proliferation by using a growth inhibition assay. Viable cell counts at each concentration were obtained by hemocytometer and trypan blue exclusion, and percent growth inhibition was calculated based on control cultures at the same time-point. As a measure of colonigenic survival, the percent inhibition of colony formation in drug-treated dishes was calculated based on the number of colonies (>50 cells) in control dishes.

RESULTS

Genistein at concentrations of 25 and 50 micromol/L inhibited the colonigenic growth of G-401 by 37% and 79% (P = .01 and 5E-06, 2-tailed t test, respectively) and that of SK-NEP-1 by 44% and 74% (P = .0001 and 9.9E-07). The mean percent growth inhibition at the above doses was 57% +/- 7.9% and 96% +/- 0.2% for G-401, and 47% +/- 11.2% and 60% +/- 2.7% for SK-NEP-1. AG1478 at concentrations of 1,000 and 5,000 nmol/L inhibited the colonigenic growth of G401 by 75% and 78% (P = .0005 and 7.38E-06, respectively) and that of SK-NEP-1 by 19% and 40% (P = .02 and .0001). The percent growth inhibition at the mentioned concentrations for G-401 were 53% +/- 9.3% and 63% +/- 6.3%, and for SK-NEP-1 were 55% +/- 14.5% and 65% +/- 20.1%, respectively. AG1295 did not appear to be as effective as AG1478.

CONCLUSIONS

This is the first experimental study on the use of GFR-TK inhibitors as a potential treatment for pediatric renal tumors. GFR-TK inhibitors such as genistein occur naturally in soybean foods and have been shown to reach therapeutic levels in blood after consuming a soybean-based diet. Considering the significance of growth factor receptor activity in Wilms' tumor development, inhibition of GFR-TKs should be investigated as effective and potentially nontoxic adjunctive treatment for this childhood tumor. Furthermore, GFR-TK inhibitors may offer an effective alternative to the treatment of commonly fatal rhabdoid tumor of the kidney in children.