Extraoral appliances: a twenty-first century update

Biomechanical performance of ATOZ expander: Finite-element analysis

INTRODUCTION

Microimplant-assisted rapid palatal expansion appliances have been used for the treatment of orthodontic patients with maxillary deficiency. A new design named ATOZ (applicable from A to Z) was recently introduced to expand the scope of treatment in early permanent dentition. The objective of this study was to analyze the biomechanical performance of the ATOZ expander with various microimplants configurations using finite-element method.

METHODS

Nine ATOZ models were designed based on the number of microimplants configurations on the palate. For skeletal maturation, stage B midpalatal suture (MPS) maturation classification was chosen. A displacement along the sagittal axis, parallel to the MPS, of 0.15 mm was applied on each side of the device to simulate a 1 jackscrew turn of 0.3 mm.

RESULTS

Configurations 1, 2, 6, and 7 achieved a quasi-parallel skeletal movement with a uniform distribution of displacement in the maxilla. The highest posterior nasal spine to anterior nasal spine ratio of 95.95% was found with configuration 6, indicating an optimum quasi-parallel expansion. For configuration 2, microimplants 1 and 2 exhibited stresses of 619.18 MPa and 656.49 MPa, respectively, whereas microimplants 7 and 8 showed stresses of 609.64 MPa and 658.30 MPa, respectively. Maximum stress in zygomatic bone was 0.69 MPa. Higher stresses were more distributed in the zygomaticofrontal suture than in zygomaticotemporal and zygomaticomaxillary sutures.

CONCLUSIONS

In terms of posterior nasal spine to anterior nasal spine ratio, skeletal-to-dental ratio, and MPS deformation, ATOZ with configurations 1, 2, and 6 outperform other configurations, and thus, they can be recommended for correction of maxillary deficiency in patients with skeletal maturation of stage B or earlier.

Comparison of treatment effects between two types of facemasks in early Class III patients

OBJECTIVE

To compare the short-term treatment effects between two types of facemasks in skeletal Class III patients.

MATERIALS AND METHODS

This retrospective study included 40 skeletal Class III subjects (mean age: 7.7 years) who had been treated with protraction facemasks with forehead straps (PFFS) or Petit type facemasks (PTF). Lateral cephalograms were analyzed at pretreatment (T1) and posttreatment (T2) with an average interval of 9 months.

RESULTS

At T1, PFFS and PTF groups showed similar sagittal, vertical dentoskeletal patterns. From T1 to T2, both groups presented significant forward movement of the maxilla, posterior movement and clockwise rotation of the mandible (all p < .001), labioversion of the maxillary incisors, and linguoversion of the mandibular incisors. They showed increased overjet (p < .001). Although there were no significant differences in the number of changes in most dentoskeletal variables between the two groups, the PFFS group showed more anterior rotation of the palatal plane and backward rotation of the mandible compared to the PTF group, resulting in a significant decrease (-0.42 mm) in overbite (p < .05).

CONCLUSIONS

Both PFFS and PTF showed no significant differences in most skeletal and dental changes, except for overbite. These findings might be helpful for clinicians in selecting the types of facemasks for growing Class III malocclusion patients.

Treatment of Maxillary Retrusion-Face Mask with or without RPE?

Background/Aim: Maxillary transverse deficiency often combines with retruded maxillary skeletal position causing a skeletal class III malocclusion. In these cases combination of rapid palatal expander and a facial mask to protract the maxilla is a very effective treatment protocol. When the maxilla is not deficient is it necessary to use palatal expansion before protracting? Should we use this combination because it has been proved to be effective? The aim of this paper is to show that maxillary protraction is also effective when applied without expanding the maxilla although there are some statistically significant changes.

Material and Methods: Two groups of 20 patients each, were created for this study. The first group were treated with rapid palatal expansion and face mask. In the second group, patients were treated only with face mask.

Results: Measurements made at T0 (prior to treatment) and those at T1 (after treatment) were statistically analyzed. At the end of the treatment patients of the 1st group showed significant difference for the values of SNA, SNB, ANB angles (p=0.000). Significant changes were observed also for the second group (SNA, SNB, ANB). The only differences between the two groups were observed regarding SNA angle (p=0.040) and maxillary incisor inclination (p=0.028).

Conclusions: At the end of treatment, all patients showed skeletal class III correction and improved facial appearance. Significant changes of SNA angle were observed for each group. There were also significant changes in the position of the mandible. These changes contributed in skeletal class III correction but there was no significant difference between them.

Clinical Tip for Adjusting Reverse Pull Facemask/Headgear Assembly

Point of force application is critical in predicting the result of reverse pull headgear assembly. Different people have suggested different point of force application. A clinical tip is provided for adjusting the hook of intraoral stabilizing appliance, so that it rests on zero moment line which helps in translatory movement of maxilla. Simple and effective clinical method of adjusting the reverse pull headgear is illustrated here along with its biomechanical justification.

Expansion/Facemask Treatment of an Adult Class III Malocclusion

The orthodontic treatment of class III malocclusion with a maxillary deficiency is often treated with maxillary protraction with or without expansion. Skeletal and dental changes have been documented which have combined for the protraction of the maxilla and the correction of the class III malocclusion. Concerning the ideal time to treat a developing class III malocclusion, studies have reported that, although early treatment may be the most effective, face mask therapy can provide a viable option for older children as well. But what about young adults? Can the skeletal and dental changes seen in expansion/facemask therapy in children and adolescents be demonstrated in this age group as well, possibly eliminating the need for orthodontic dental camouflage treatment or orthognathic surgery? A case report is presented of an adult class III malocclusion with a Class III skeletal pattern and maxillary retrusion. Treatment was with nonextraction, comprehensive edgewise mechanics with slow maxillary expansion with a bonded expander and protraction facemask.