The meta-analysis aimed to evaluate the efficacy of mandibular advancement device (MAD) for the treatment of obstructive sleep apnea (OSA) and explore the effect of different positions on MAD for OSA.
The Embase, PubMed, Medline, and Cochrane Library databases were searched for relevant studies evaluating the effect of MAD on the treatment of OSA from database inception to November 2022. The Bayesian random-effects mode was used to calculate the pooled outcome. Subgroup analysis and sensitivity analysis were applied to investigate the heterogeneity.
A total of 6 studies enrolling 643 patients were eligible for further analysis. MAD treatment led to improvements in total apnea-hypopnea index (AHI) for both positional OSA(POSA) and Non-POSA groups, but there was no significant difference in the effect of MAD on Non-POSA and POSA (MD = -1.46,95%CI [-4.89,1.97], P = 0.40). In the supine position, AHI improvement after MAD treatment in POSA group was more than that in Non-POSA group by 15 events/hour in average (MD = 14.82, 95%CI [11.43,18.22], P＜0.00001), while in the non-supine position, the change of AHI in Non-POSA group was significantly better than that in POSA group by approximately 8 events/hour (MD = -7.55,95%CI[-10.73,-4.38],p < 0.00001).
MAD is more suitable for POSA compared to Non-POSA in patients with habitual sleep in the supine or supine predominant position. While for patients with habitual sleep in the non-supine position, MAD is an effective treatment option for Non-POSA.

Studies show that patients with obstructive sleep apnea (OSA) are more likely than the general population to have psychological disorders such as depression. However, it is less clear how OSA treatment affects this association. This meta-analysis aimed to assess whether or not continuous positive airway pressure (CPAP) and mandibular advancement devices (MADs) reduce depression symptoms in patients with OSA.
We searched Pubmed, Embase, Web of Science, and Cochrane Library from creating the databases until November 2022. Our analysis included RCTs that examined CPAP and MAD treatment effectiveness for depression in patients with OSA.
We identified 17 CPAP studies comprising 1,931 patients for inclusion in the meta-analysis. The results of the meta-analysis using a fixed effects model found that CPAP improved depressed mood in patients with OSA relative to controls (SMD = 0.27;95% CI:0.18,0.36), with small heterogeneity among trials (I2 = 8.1% < 50%, P = 0.359). We performed subgroup analyses on three factors: the length of trial follow-up, patient adherence data, and depression assessment scales. The meta-analysis also identified six MAD studies involving 315 patients. According to this analysis, there was no heterogeneity between studies (I2 = 0%, P = 0.748). MADs did not significantly improve depression symptoms compared to controls, indicating a combined effect of SMD = 0.07 (95% CI: - 0.15,0.29), P > 0.05.
The present findings confirm that CPAP may improve depressive symptoms in patients with OSA. However, the review results suggest that MADs have no significant effect on depressive symptoms in patients with OSA, a finding that is different from the results of previous meta-analyses.

OBJECTIVE: To generate a novel subtype of obstructive sleep apnea (OSA) based on anatomical features and verify the differences in the response of different subtypes to orthodontic treatment, thus providing a theoretical reference for clinical decision-making.
METHODS: A K-means cluster analysis was performed for this retrospective serial study, which includes 722 OSA patients, aged 44.0 (36.0, 54.0) years, 80.2% male, with apnea-hypopnea index (AHI) of 23.2 (13.4, 39.6) events·h-1 , and body mass index (BMI) of 25.47 ± 3.00 kg·m-2 . All samples were divided into three subtypes based on AHI, BMI, and five variables of craniofacial measurements. Sixty-seven cases with mandibular advancement devices (MAD) therapeutic results were further applied to validate the efficacy and side effects of this treatment in different subtypes.
RESULTS: Two hundred and thirty patients (31.9%) were characterized as cluster 1: AHI of 17.65 (11.80, 30.42) events·h-1 , BMI of 23.65 ± 2.62 kg·m-2 , with skeletal Class II high-angle shape. Cluster 2 included 278 patients (38.5%): AHI of 17.00 (11.00, 26.48) events·h-1 , BMI of 25.36 ± 2.53 kg·m-2 , soft palate length (SPL) of 39.25 mm (36.12, 42.20), with basically normal skeleton and normal airway size. Cluster 3, consisting of 214 patients (29.6%), exhibited a combination of anatomical deformity and obesity, with the highest AHI and BMI of 45.35 (30.42, 62.53) events·h-1 and 27.57 ± 2.59 kg·m-2 respectively, but less deformity degree than cluster 1. Cluster 2 had the highest response rate and relatively mild side effects with MAD.
CONCLUSIONS: Orthodontic treatment based on anatomical morphology could exert a better effect on mild-moderate OSA patients with mild skeletal deformity.

BACKGROUND: To explore the feasibility, the efficacy, and the mechanism of mandibular advancement devices (MAD) in the treatment of persistent sleep apnea after surgery.
METHODS: Nineteen patients who failed uvulopalatopharyngoplasty (UPPP) or UPPP plus genioglossus advancement and hyoid myotomy (GAHM) were given a non-adjustable MAD for treatment. All patients had polysomnography (PSG) at least 6 months post-UPPP with and without the MAD. Seventeen patients had computed tomography (CT) examinations.
RESULTS: After the application of MAD, the apnea hypopnea index (AHI) decreased significantly from 41.2 ± 13.1/h to 10.1 ± 5.6/h in the responder group. The response rate was 57.9 % (11/19). During sleep apnea/hypopnea acquired from sedated sleep, the cross-sectional area and anterior-posterior and lateral diameters of the velopharynx enlarged significantly from 4.2 ± 6.0 mm2 to 17.5 ± 15.3 mm2, 1.9 ± 2.3 mm to 6.5 ± 4.1 mm, and 1.1 ± 1.3 mm to 2.6 ± 2.1 mm, respectively (P < 0.01) in the responder group with MAD. The velopharyngeal collapsibility also decreased significantly from 83.3 ± 21.8 % to 46.5 ± 27.1 %. The glossopharyngeal collapsibility decreased from 39.8 ± 39.1 % to -22.9 ± 73.2 % (P < 0.05).
CONCLUSIONS: MAD can be an effective alternative treatment for patients with moderate and severe OSAHS after surgery. The principal mechanisms underlying the effect of MAD are expansion of the lateral diameter of the velopharynx, the enlargement of the velopharyngeal area, the reduction of velopharyngeal and glossopharyngeal collapsibility, and the stabilization of the upper airway.