Evaluation of the stiffness characteristics of rapid palatal expander screws

The efficiency of a customized distalizer with Variety SP® screws anchored on palatal miniscrews for upper molar distalization

OBJECTIVE

To assess the effectiveness of a customized distalizer with Variety SP® screws anchored on palatal miniscrews for upper molar distalization.

METHODS

Seventeen patients aged between 12.5 and 24 years underwent distalization with a customized distalizer. Lateral cephalogram and cast analysis were performed before and after distalization. Linear and angular parameters of the upper first molar, first premolar, and central incisor were assessed.

RESULTS

Distalization with the force passing near the center of resistance (CRes) of the upper first molars resulted in distal movement, with minimal distal tipping (2.8 ± 0.45°, p< 0.05). However, distalization passing occlusal to the CRes led to greater distal tipping (13.6 ± 1.63°, p< 0.05). Statistically significant spontaneous distal tipping and distal movement of the upper first premolars occurred, with a mean of 6.2 ± 1.24° (p< 0.05) and 0.68 ± 0.34 mm (p< 0.05), respectively. The positional change of the upper central incisors presented a mean of -0.23 ± 0.1 mm (p> 0.05) and 2.65 ± 1.1° (p< 0.05). Upper first molar intrusion was statistically significant, with a mean of 0.88 ± 0.2 mm (p< 0.05). Upper right and left first molars rotation towards palatal midline presented mean of 4.1 ± 0.19° (p< 0.05) and 3.4  ± 0.1° (p< 0.05), respectively. Additionally, the distance between upper right and left first molars increased significantly, with a mean of 2.54 ± 0.01 mm (p< 0.05).

CONCLUSION

The study successfully demonstrated the efficiency of molar distalization without anchorage loss using a customized distalizer anchored on palatal miniscrews.

Biomechanics of conventional and miniscrew-assisted rapid palatal expansion

Posterior Crossbite is a common condition resulting because of transverse maxillary deficiency. The growth of the craniofacial complex finishes first in the transverse dimension, followed by sagittal and vertical dimensions. Conventional rapid palatal expansion (RPE) appliances are commonly used to correct transverse maxillary deficiency. Although RPE is efficient in correcting posterior crossbite, it results in dental side effects such as buccal tipping of maxillary molars, root resorption, bone dehiscence, and relapse. Mini-implant-assisted RPE has been introduced to increase the skeletal effects of expansion especially in patients with increased maturation and greater interdigitation of midpalatal suture. This article will review the biomechanics of RPE and mini-implant-assisted RPE. Additionally, the different designs of MARPE and the long-term clinical effects of expansion appliances will also be discussed in detail.

Comparison of Mechanical Behavior of Clear Aligner and Rapid Palatal Expander on Transverse Plane: An In Vitro Study

(1) Background: This study aims to investigate, within a controlled laboratory environment, the magnitude of the transversal load and the force decay over time produced by clear aligners in comparison to a Rapid Palatal Expander (RPE). (2) Methods: Resin models of a dental maxillary arch, additively manufactured from an intraoral scan, were inserted in a testing machine with uniaxial load cells to measure the force trend over time expressed by RPE and clear aligners. The mechanical load was recorded during a certain timeframe for both appliances. (3) Results: The force expressed by the RPE ranged from 30 to 50 N for each activation, decreasing with a nonlinear pattern over time. The force expressed by the clear aligner ranged from 3 to 5 N, decreasing with a linear pattern over time. In contrast, the force generated by the clear aligner fell within the range of 3 to 5 N, showing a linear reduction in force magnitude over the observed period of time. (4) Conclusions: The RPE exerted a force magnitude approximately ten times greater than that generated by clear aligners. Nevertheless, it is essential to acknowledge that the oral environment can significantly influence these results. These limitations underscore the need for caution when applying these findings to clinical settings.

Expansion in the absence of crossbite – rationale and protocol

Transverse maxillomandibular discrepancies are a major component of several malocclusions. Clinically, posterior crossbite is a common and valid indicator of maxillary transverse problems and orthopedic and orthodontic forces are routinely used to correct maxillary transverse deficiency. However, crossbite and transverse discrepancies are not a homologous group but must be viewed as a continuum with varying degree of abnormality. The etiology, diagnostic protocol, rationale, and procedures employed for correcting maxillary transverse discrepancy in the absence of crossbite are discussed in the article.

Mandibular response after rapid maxillary expansion in class II growing patients: a pilot randomized controlled trial

Background

The aim of this pilot randomized controlled trial (RCT) was to evaluate the sagittal mandibular response induced by rapid maxillary expansion (RME) therapy in mixed dentition patients with class II malocclusion, comparing the effects of bonded RME and banded RME with a matched untreated class II control group.

Methods

This RCT was designed in parallel with an allocation ratio of 1:1:1. The sample consisted of 30 children with a mean age of 8.1 ± 0.6 years who were randomly assigned to three groups: group 1 treated with bonded RME, group 2 treated with banded RME, and group 3 the untreated control group. All patients met the following inclusion criteria: early mixed dentition, class II molar relationship, transverse discrepancy ≥ 4 mm, overjet ≥ 5 mm, and prepubertal skeletal maturity stage (CS1–CS2). The expansion screw was activated one quarter of a turn per day (0.25 mm) until overcorrection was reached. For each subject, lateral cephalograms and plaster casts were obtained before treatment (T1) and after 1 year (T2). A randomization list was created for the group assignment, with an allocation ratio of 1:1:1. The observer who performed all the measurements was blinded to group assignment. The study was single-blinded in regard to statistical analysis.

Results

RME was effective in the correction of maxillary deficiency. Class II patients treated with both types of RME showed no significant improvement of the anteroposterior relationship of the maxilla and the mandible at both skeletal and occlusal levels. The acrylic splint RME had significant effects on reducing the skeletal vertical dimension and the gonial angle.

Conclusions

The orthopedic expansion did not affect the sagittal relationship of class II patients treated in the early mixed dentition when compared with the untreated control group. Additional studies with a larger sample are warranted to elucidate individual variations in dento-skeletal mandibular response to the maxillary expansion protocol in class-II-growing patients.

Trial registration

ClinicalTrials.govNCT03159962.