Mandibular propulsion appliance for adults with Class II malocclusion: a systematic review and meta-analysis

Comparison of part-time and full-time mandibular advancement: enlightenment based on type H vessel coupling osteogenesis

OBJECTIVES

This study was aimed at resolving the controversy over the wearing time of mandibular advancement (MA) appliances by comparing the differences between part-time and full-time MA (PTMA and FTMA) from the perspective of promoting H-type vessel coupling osteogenesis in the condylar heads.

MATERIALS AND METHODS

Thirty 30-week-old male C57BL/6J mice were randomly divided into 3 groups: the control (Ctrl), PTMA, and FTMA groups. The mandibular condyles were analyzed by morphology, micro-computed tomography, histological staining, and immunofluorescence staining to investigate the changes of the condylar heads in the PTMA and FTMA groups after 31 days.

RESULTS

Both PTMA and FTMA models promoted condylar growth and achieved stable mandibular advancement at day 31. However, compared with PTMA, FTMA has the following characteristics. First, new bone formation in the condylar head was detected in the retrocentral region in addition to the posterior region. Second, the condylar proliferative layer was thicker, and the number of pyknotic cells in the hypertrophic and erosive layers was higher. Moreover, endochondral osteogenesis of the condylar head was more active. Finally, the retrocentral and posterior regions of the condylar head had more vascular loops or arcuate H-type vessel coupling Osterix⁺ osteoprogenitors.

CONCLUSIONS

While both PTMA and FTMA induced new bone formation in the condylar heads of middle-aged mice, FTMA promoted more osteogenesis by volume and region. Furthermore, FTMA presented more H-type vessel coupling Osterix⁺ osteoprogenitors in both the retrocentral and posterior regions of the condylar head.

CLINICAL RELEVANCE

FTMA is better at promoting condylar osteogenesis, especially in non-growing patients. We suggest that enhancing H-type angiogenesis could be an effective strategy to achieve favorable MA outcomes, especially for patients unable to meet the FT-wearing requirement or being non-growing.

Deferoxamine mesylate enhances mandibular advancement-induced condylar osteogenesis by promoting H-type angiogenesis

BACKGROUND

The effect of functional orthopaedic treatment for mandibular deficiency relies on mandibular advancement (MA)-induced condylar new bone formation. However, this is not easy to achieve, especially in non-growing patients. Therefore, how to obtain reliable MA-induced condylar osteogenesis is a subject much worthy of study.

OBJECTIVE

To investigate whether deferoxamine mesylate (DFM) enhances MA-induced condylar osteogenesis in middle-aged mice.

METHODS

Forty 30-week-old male C57BL/6J mice were randomly divided into 4 groups: the control (Ctrl), DFM, MA + Ctrl and MA + DFM groups. After a 4-week experimental period, femurs, tibias and condyles were collected for morphological, micro-computed tomography and histological evaluation.

RESULTS

For long bones, DFM reversed osteoporosis in middle-aged mice by promoting H-type angiogenesis. For mandibular condyles, MA promoted condylar osteogenesis in middle-aged mice, thereby allowing the mandible to achieve a stable protruding position. In addition, DFM enhanced the volume and quality of MA-induced condylar new bone formation. Furthermore, histological analysis revealed that DFM enhanced MA-induced condylar subchondral ossification. Mechanistically, it was confirmed that DFM increased the number of H-type vessels and their coupled Osterix⁺ osteoprogenitors by upregulating the hypoxia-inducible factor (HIF)-1α signalling pathway, thereby enhancing MA-induced condylar osteogenesis.

CONCLUSION

Applying DFM to enhance MA-induced condylar osteogenesis through H-type angiogenesis is expected to be an effective strategy to achieve favourable functional orthopaedic treatment effectiveness in non-growing patients.

The effect of orthodontic treatment on facial attractiveness: a systematic review and meta-analysis

BACKGROUND

Facial and smile attractiveness are significant motivating factor for patients to seek orthodontic treatment. Although there is a general belief that orthodontic treatment improves facial appearance, this has yet not been systematically evaluated.

OBJECTIVE

The objective of this study was to assess the current evidence on the effect of orthodontic treatment on facial attractiveness.

SEARCH METHODS

Systematic and unrestricted search of nine databases were performed up to January 2022.

SELECTION CRITERIA

Studies evaluating facial attractiveness before and after orthodontic treatment.

DATA COLLECTION AND ANALYSIS

Extracted data included study design and setting, sample size and demographics, malocclusion type, treatment modality, and method for outcome assessment. Risk of bias was assessed with the ROBINS-I tool for non-randomized studies and with RoB-2 for randomized controlled trials (RCTs). Random-effects meta-analyses of mean differences and their 95% confidence intervals (CIs) were performed.

RESULTS

Twenty studies were included in data synthesis; three randomized controlled clinical trials and 17 non-randomized clinical studies of retrospective or prospective design. One of the RCTs was found to have low risk of bias, one presented some concerns and the third showed a high risk of bias. All non-randomized studies showed either unclear or high risk of bias. Data syntheses showed that orthodontic treatment improved facial attractiveness ratings by 9% when compared with untreated controls (MD: 9.05/95% CI: 4.71; 13.39). A combination of orthodontics and orthognathic surgery also showed a positive effect of 5.5% (MD: 5.51/95% CI: 1.55; 9.47) when compared with orthodontic treatment alone. There was no difference in effect between extraction and non-extraction treatments (MD: -0.89/ 95% CI: -8.72; 6.94) or between different types of Class II correctors (MD: 2.21/95% CI: -16.51; 20.93).

LIMITATIONS

With the exception of two RCTs, included studies were of unclear or low quality.

CONCLUSIONS

Orthodontic treatment has a clinically weak effect on facial attractiveness when compared to no treatment. The same is true when a combined orthodontic/surgical treatment is compared to orthodontics alone.

REGISTRATION

PROSPERO #: CRD42020169904.

Mandibular advancement analysis among orthodontists, lay people and patients in class II malocclusion subjects. A three-dimensional imaging study

OBJECTIVE

To evaluate the acceptance of orthodontists, laypeople and the patient when progressive mandibular advancements are performed in class II subjects with mandibular retrognathism.

SETTING AND SAMPLE

3D images were obtained by an optical surface scanning of fifteen individuals (12 males and three females, mean age of 23 years and 8 months) with mandibular retrognathism in three mandibular positions: maximum intercuspation (MIC) and progressive mandibular advancement of 2 and 4 mm.

METHODS

The images (n = 45) were evaluated through a scale by two groups of panellist, 20 orthodontists, 20 laypeople and by the patients themselves (n = 15). The participants evaluated and rated each video and give scores between 0 and 10, according to their perception of facial harmony. MANOVA for repeated measures was used for intra- and intergroup differences and to evaluate the patients' self-perception.

RESULTS

Laypeople reported better face acceptance than orthodontists in MIC and progressive mandibular advancement of 2 and 4 mm (P < .0001). 80% of the patients evaluated their own face as pleasant in MIC. Around half of them did not note significant difference following mandibular advancement of 2 mm as compared with MIC and even two-third attributed lower scores when the mandible was advanced 4 mm.

CONCLUSION

A high variability was observed among all groups of raters. Patient´s opinion should be taken into account when mandibular advancement of 4 mm or more is planned. This study suggests that a thorough discussion of facial changes resulting from mandibular advancement should be carried out among professionals, parents and patients.