Comparison of the effects of rapid maxillary expansion versus Twin Block appliance on mandibular growth in skeletal Class II patients

Efficacy of a modified twin block appliance compared with the traditional twin block appliance in children with hyperdivergent mandibular retrognathia: protocol for a single-centre, single-blind, randomised controlled trial

INTRODUCTION

Compensatory mouth breathing, caused by nasopharyngeal obstructive diseases, is the main cause of hyperdivergent mandibular retrognathia in children. Such deformities require effective growth guidance before pubertal growth peaks. The traditional mandibular advancement device, twin block (TB), can guide the forward development of the mandible. However, the side effect of increasing the vertical dimension of the lower facial third, worsens the facial profile of children with divergent growth trends. To solve this problem, a modified TB (LLTB) appliance was designed to control the vertical dimension by intruding incisors and inhibiting the elongation of posterior teeth during the advancement of the mandible, which could avoid the side effects of traditional appliances and effectively guide the growth of the mandible in a normal direction.

METHODS AND ANALYSIS

The study was designed as a single-centre, single-blind, randomised, parallel controlled trial. We aim to enrol 60 children aged 9-14 years with hyperdivergent skeletal class II malocclusion, using a 1:1 allocation ratio. The participants were will be randomly assigned to receive either the TB or LLTB treatment. The primary outcome will be a change in the angle of the mandibular plane relative to the anterior cranial base. The secondary outcomes will include changes in the sagittal maxillomandibular relation, occlusal plane, facial height, morphology of the mandible and upper airway width. Safety endpoints will also be evaluated.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the ethics committee of Shanghai Stomatological Hospital. Both participants and their guardians will be fully informed of the study and sign an informed consent form before participating in the trial. The results will be publicly available in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

ChiCTR2000035882.

Effect of the magnitude of condylar head displacement on the TMJ function in skeletal class II patients undergoing different degrees of mandibular advancement: A retrospective comparative study

PURPOSE

This study aimed to compare the condylar head displacement (CHD) after bilateral sagittal split ramus osteotomy (BSSO) between different degrees of mandibular advancement in skeletal class II patients and to evaluate whether the temporomandibular joint (TMJ) function would be affected.

PATIENTS AND METHODS

Fifty-nine patients (118 condyles) were included in this retrospective study and were divided into three groups based on the distance of mandibular advancement. The CHD in three directions, x (sagittal direction), y (coronal direction), and z (axial direction), was measured before operation (T0), immediately after operation (T1), and at least 6 months after operation (T2), and the TMJ function of patients was followed up and scored using the Helkimo index system. All the abovementioned data were statistically analyzed, and p < 0.05 was considered the statistical difference standard.

RESULT

During the BSSO surgery, the condyle was predominantly displaced in a lateral, posterior, and superior direction whenever in T1 and T2, even though the degree of CHD was different. Regarding the amount of CHD, the large advancement group was higher than the other two groups in T1 and T2 (p＜0.01). The Helkimo index scores of the three groups were evaluated, and there was no significant statistical difference between the Ai and Di index of the three groups.

CONCLUSION

In our center, CHD occurred in lateral, posterior, and superior directions following mandibular advancement in skeletal class II patients, with a positive correlation between the CHD and the mandibular advancement; however, the TMJ function of the three groups did not show significant differences.

Changes in the Mandible Following Rapid Maxillary Expansion in Children with Class II Malocclusion: A Systematic Review

Objective: The aim of this systematic review was to determine whether rapid maxillary expansion (RME) allows favorable changes in the mandible during the treatment of class II malocclusion before the growth spurt. Methods: A search of Pubmed/Medline, the Science Direct, and the Google Scholar database was performed. The keywords used were: orthodontics, rapid maxillary expansion, class II, and growing patients. Relevant articles were assessed for quality according to Cochrane guidelines, and then changes in SNA, SNB, ANB, NL-NSL (or SN-SNP.SNA), and ML-NSL (or SN-Go-Gn) relationships were analyzed. Results: The selection process brought forth five articles, including 162 patients (91 females, 71 males) for detailed analysis. The quality of the evidence (GRADE) for comparisons and outcomes was assessed as moderate for SNB and ANB and as low or very low for other variables. Conclusions: The results of this systematic review showed that there is a small body of moderate-quality evidence for statistically and clinically favorable changes in SNB and ANB angles and a small body of low-quality evidence for changes in vertical parameters after RME.