Skeletal and dental effects of Herbst appliance anchored with temporary anchorage devices: A systematic review with meta-analysis

Sustained Protraction Increases Lengthening of the Mandibular Condylar Process Whilst Changes Its Growth Direction in a Rat Model

OBJECTIVE

In Class II elastics treatment, the mandible is subject to sustained protraction. The study aimed to investigate the morphological and histological changes resulting from sustained mandibular protraction, through establishment of a novel model in rat.

MATERIALS AND METHODS

Forty-eight 4-week-old male Sprague-Dawley rats were randomly divided into three groups, including the 50 and 100 cN protraction groups, and the control. In the two protraction groups, NiTi coil springs were fixed between the metal bands on the maxillary incisors and mandibular molars to pull the mandible forward. CBCT scans were taken immediately before (T0), 2 weeks (T1) and 4 weeks (T2) after the traction. Histological and immunohistochemical analyses were performed at T1 and T2.

RESULTS

Increase of the condylar process length and angular process length were significantly larger in the two protraction groups than that in the control; however, the condylar process angle (∠CPA) was significantly reduced by the protraction at T2, leading to decreased condylar height. The protraction decreased the condylar cartilage thickness at T1, which recovered to the control level at T2, with no significant changes detected in the expression of SRY-related high mobility group-box gene 9 (SOX9) and type II collagen (COL II), two chondrogenic markers.

CONCLUSION

The established rat model is manoeuvrable and reliable, which exerts sustained and measurable mandibular protraction. The sustained protraction increases the lengthening of the mandibular condylar process, but alters its growth direction by causing it to turn downwards.

The Efficacy of the RME II System Compared with a Herbst Appliance in the Treatment of Class II Skeletal Malocclusion in Growing Patients: A Retrospective Study

(1) Background: The objective of this study was to evaluate the efficacy of the Rapid Maxillary Expander (RME) II System compared to a Herbst appliance and a control group in the treatment of class II skeletal malocclusions in growing patients. (2) Methods: A total of 30 class II patients treated using the RME II System (group R) were compared with 30 patients treated with a Herbst appliance (group H) and 30 untreated class II children (group C). Cephalograms were compared at the start (T0) and after 24 months (T1). Nine cephalometric parameters were analyzed: SN-MP, SN-PO, ANB, AR-GO-ME, AR-GO-N, N-GO-ME, SN-PP, LFH, CO-GN, 1+SN, IMPA, OVERJET, and OVERBITE. Since the variables failed the normality test, a Wilcoxon test was performed for a pairwise comparison of the cephalometric measurements taken at T0 (pre-treatment) and at T1 (post-treatment). ANOVA with Tukey post hoc correction was used to evaluate the differences among the groups. (3) Results: ANOVA showed a statistically significant difference for all analyzed variables except for AR-GO-ME, AR-GO-N, and N-GO-ME. Post hoc Tukey's HSD test showed the following difference: the SN-PO angle in group H was 3.59° greater than in group R; the LFH in group H was 4.13 mm greater than in group R. The mandibular length (CO-GN) in group H was 3.94 mm greater than in group R; IMPA in group H was 6.4° greater than in group R; and the ANB angle in group H was 1.47° greater than in group R. (4) Conclusions: The RME II System is an effective therapeutic device for class II skeletal malocclusion treatment in growing patients.

Class II subdivision treatment and stability with asymmetric Herbst appliance: A case report

Non-surgical treatment of Class II subdivision may involve complex mechanics or asymmetric tooth extraction in its resolution. This report demonstrates the result and the short-term stability of Class II subdivision treated with asymmetrically installed Herbst appliance followed by conventional fixed orthodontic appliance. The approach allowed the correction of the unilateral Class II molar relationship and increased overjet, as well as the deviation of dental midlines, with improvement in lip posture and facial profile. The results remained stable two years after treatment, confirming the treatment success.

Is significant mandibular advancement possible after the peak of puberty? Dento-osseous palatal expansion and the STM4 technique (Skeletal Therapy Manni Telescopic Herbst 4 miniscrews): A case report

INTRODUCTION

Treatment of skeletal class II growing patients often requires the use of functional appliances, aimed at promoting mandibular advancement. Among these, Herbst appliance is recommended for its effectiveness, efficiency, and reduced need for compliance. Despite its skeletal favourable effects, well-known dental compensations can occur, especially when the appliance is not used close to the pubertal peak: upper incisors retroclination, lower incisors proclination, upper molars distalization and lower molars mesialization could reduce the overjet needed for a proper mandibular advancement. To counteract these unfavourable effects skeletal anchorage could be crucial.

AIM

The aim of this case report is to describe and evaluate the effects of using a skeletally anchored Herbst appliance in an 18-year-old (CVM5) male patient with skeletal Class II malocclusion and a convex profile.

TREATMENT PROTOCOL

The treatment started with a tooth-bone-borne palatal expansion, then the upper arch was bonded with pre-adjusted ceramic brackets. After 2months, a Manni Telescopic Herbst (MTH) supported by 4 miniscrews (two in the maxilla and two in the mandible) was applied. To avoid anchorage loss, TADs were connected with elastic chains to the arches. Nine months later, the Herbst was removed, the lower teeth were bonded and the patient wore class 2 elastics to stabilise the occlusion.

RESULTS AND CONCLUSIONS

After 24months the treatment goal was achieved with a considerable improvement of the profile and a clinically significant mandibular advancement (Pogonion moved forward 7mm). A one-year follow-up lateral X-rays showed a good stability of the result.

Evaluation of the Co-Go-Me angle as a predictor in Class II patients treated with Herbst appliance and skeletal anchorage: a retrospective cohort study

Introduction

A condylion-gonion-menton (Co-Go-Me) angle threshold of 125.5° has been introduced as a predictive parameter of cephalometric mandibular response in the orthopedic treatment of growing Class II patients with functional appliances, despite some contradictions in the literature. Considering the lack of studies evaluating the role of skeletal anchorage, this study aims to reassess the threshold of 125.5° in the Co-Go-Me angle as a useful predictor in growing skeletal Class II patients treated with acrylic splint Herbst appliance and two mini-screws in the lower arch (STM2).

Methods

Thirty-five consecutively treated patients (20 males, 15 females; mean age, 11.37 years) with mandibular retrusion were classified into two groups according to their Co-Go-Me baseline values (Group 1, <125.5°; Group 2, >125.5°). The STM2 protocol involved the use of the MTH Herbst appliance with an acrylic splint in the lower arch and two interradicular mini-screws as anchorage reinforcement. Cephalometric analysis was performed by the same operator for each patient at baseline (T0) and at the end of the Herbst phase (T1). The effects of time and group on the variables were assessed by a repeated-measures analysis of variance. The primary research outcome was the difference between the groups in terms of mandibular responsiveness to treatment referred to as the relative difference (T1-T0) in Co_Gn.

Results

The mean duration of the treatment was 9.5 months. No statistically significant differences between groups were detected at baseline, except from the expected SN/GoMe° (p < 0.001) and Co-Go mm (p = 0.028). No statistically significant changes between groups, which were caused by the treatment, were found considering the mandibular sagittal and vertical skeletal parameters. Similarly, no statistically significant differences were found in the dental changes between the high-angle and low-angle patients, apart from the upper molar sagittal position (p = 0.013).

Discussion and conclusions

The 125.5° threshold in the Co-Go-Me value was not a reliable predictive parameter for the mandibular response in growing patients treated with the MTH Herbst appliance and lower skeletal anchorage. Due to its effective control in the sagittal and vertical planes, the STM2 technique might be an appropriate protocol to use in treating skeletal Class II patients, regardless of the growth pattern.

Mandibular Endochondral Growth Is Specifically Augmented by Nutritional Supplementation with Myo-Inositol Even in Rabbits

Mandibular retrognathism occurs by insufficient mandibular growth and causes several issues, such as respiratory difficulty and diminished masticatory function. At present, functional orthodontic appliances are used for stimulating mandibular growth in pediatric cases. However, the effectiveness of functional appliances is not always stable in daily practices. A more effective, reliable, and safer therapeutic method for mandibular growth promotion would be helpful for growing mandibular retrognathism patients. As we previously discovered that nutritional supplementation of myo-inositol in growing mice specifically increases mandibular endochondral growth, we performed preclinical animal experiments in rabbits in this study. Briefly, six-week-old male Japanese white rabbits were fed with or without myo-inositol supplementation in laboratory chow until 25 weeks old, and 3D image analysis using micro CT data and histological examinations was done. Myo-inositol had no systemic effect, such as femur length, though myo-inositol specifically augmented the mandibular growth. Myo-inositol increased the thickness of mandibular condylar cartilage. We discovered that the nutritional supplementation of myo-inositol during the growth period specifically augmented mandibular growth without any systemic influence, even in rabbits. Our results suggest the possibility of clinical use of myo-inositol for augmentation of the mandibular growth in growing mandibular retrognathism patients in the future.

The Use of TADs in the Mandibular Arch to Prevent Proclination of the Lower Incisors during the Use of the Mini Scope Herbst Appliance

Class II malocclusions are the most frequent within the Italian population. Normally, these malocclusions are caused by a reduction in a mandibular component whose functional stimulus is still very much cause for debate. The negative effect of all types of Class II functional appliances is in the proclination of the lower incisors, which, in subjects whose incisors are already labially inclined, must be checked at all times to avoid serious consequences to these elements. In this case study, a girl aged 14 years and 5 months presented with Class II malocclusion, 2nd division with a convex profile and a visibly retruded chin. The lower incisors presented a marked proclination (-1/Go-Gn ini = 107.7°) in a brachyfacial patient. To avoid further inclination of the lower incisors a Herbst appliance was mounted in two separate sittings. The first part of the appliance including the tubes was mounted to the upper jaw allowing the vestibularisation of the upper incisors in order to increase the overjet. Once this was obtained the lower part of the appliance was mounted together with the telescopic arms associated with two temporary anchorage devices (TADs) in positions 36-37 and 46-47, and an anterior section 33-43 with distal loop to which two double metallic ligatures were anchored at the TADs to contrast the negative effect of the appliance. At the end of the first functional phase, the treatment was refined using MBK fixed therapy to finish the case. The orthodontic therapy led to a visible improvement of the profile and the achievement of a first-class dental-skeletal result on both sides. From the cephalometric evaluation carried out immediately after the Herbst appliance treatment at time T1 and at the end of the orthodontic therapy T2 it was possible to verify a slight increase in the inclination of the lower incisors (-1/Go-Gn fin = 108°). In conclusion, it can be said that the use of the skeletal anchorage avoided, in this case, the proclination effect in the lower incisors due to the use of a Herbst appliance.