TMD in OSAS PatientsTMD in OSAS Patients 

Risk of bias assessment

The overall quality of the included studies as per RoB-2 was good. Attrition bias was noted in five studies, and three studies reported high risk in outcome measures as TMDs were assessed solely based on subjective evaluation, as seen in Figures 2 and 3.

DISCUSSION

The findings presented in this review hold significance in terms of analysing and assessing the correlation between MAD therapy and the occurrence of TMD in cases of OSAS. The inclusion of studies with a wide publication period and age range ensures a comprehensive representation of the population under study. These collective characteristics allow for a more robust evaluation of the occurrence and impact of TMDs in this specific patient population. The varying effects of MAD treatment on TMD-related outcomes highlight the complexity of the relationship between MAD treatment for OSAS and TMD symptoms.

The significant reduction in TMD symptoms observed in some studies indicates the potential benefits of MAD treatment in alleviating TMD-related issues. However, the lack of significant changes in other studies emphasises the need for careful consideration of factors such as MAD appliance type, TMD assessment techniques, and follow-up duration. These findings contribute to the existing scientific knowledge in the field and have implications for clinical decision-making and further research on the association between MAD treatment for OSAS and TMD occurrence.

Bondemark et al.29 mentioned that subjects in their study had fewer episodes of headaches as a result of OSA, which could be because of a decrease in oxygen saturation. Joint sounds tended to increase in the 2 years of follow-up, but this was not significant. Doff et al.30 were the only study to have assessed patients at regular time periods of Baseline, 2 weeks, 15 weeks, and 27 weeks. Fransson et al.31 showed a dropout rate of 16%, suggesting good patient compliance. An interesting observation noted by Giannasi et al.32 was the reduction of tinnitus incidence with MAD usage. Fatigue was noted in 12 (35%) patients at baseline but reduced to two at follow-up. The study of Knappe et al.33 showed a significant amount of loss to follow-up in both short-term and long-term follow-up. The same observation was noted in the study of Martinez et al.,34 wherein only 15 out of 40 patients used MAD until the end of their follow-up. The study was also unique in that it was the only study to include patients who were diagnosed with TMD and found that the MAD intervention did not alter the prevalence even after 5 years. Only six patients remained in the study of Napankangas et al.35 out of 15 patients at the end of the study. A single examiner who was trained and experienced examined all subjects in the study of Nikolopoulou et al.36 The final size of Perez et al.37 was reduced to 85 from 167 samples. Yet, the study held credibility as a drop-out analysis was performed. Certain concerns about confounding factors were present in the study of Ranieri et al.,38 as it was hospital-based. Six and two cases presented with systemic hypertension and infarction out of 14 samples, respectively. The patients of Tegelberg et al.39 were categorised into 50% and 75% mandibular protrusion. However, no difference was noted between them in terms of TMD signs. 26% of dropouts were reported, and headaches remained for almost 1 year of treatment, which began to reduce in the follow-up phase. In the study of Walker et al.,40 TMJ pain was persistent in five samples with 75% protrusion. They were later switched to 50% protrusion. Headaches were consistently present throughout the treatment.

During the initial months of MAD therapy, there is evidence of a lower pain pressure threshold in the masticatory muscles and a higher incidence of pain, which tends to decrease over time.13-15, 30, 36 Studies have reported a reduction in both the incidence and prevalence of TMDs as well as a decrease in the number of dropouts during follow-up.38 It should be noted that CPAP, similar to MAD, may also induce orofacial pain in certain individuals, although no systematic investigation has been conducted on this topic.30 Further research is required to explore this association. TMD pain and dysfunction can manifest acutely, transiently, or chronically and may exist before or be exacerbated by treatment.42 Therefore, a gradual adjustment and advancement of the appliance, stopping at the minimum necessary advancement for managing OSAS, is recommended to facilitate adaptation of the masticatory structures.43 Increasing mandibular advancement does not consistently lead to significant improvement in success rates.13-15 Additionally, it has been observed that TMD symptoms typically arise in the early twenties and persist intermittently into middle age, with fluctuating patterns and eventual resolution over time.44 These findings offer a potential explanation for the disappearance of TMDs in some patients and the development of TMDs in others, considering the age range of the reviewed studies in our investigation.29-41 Furthermore, TMDs are known to occur more frequently in women than men,44-46 whereas OSAS is more prevalent in men than women.47, 48 Among the studies included in the review, three exclusively analysed male patients, while the others comprised a mixed population with a higher proportion of males compared to females.36, 39, 40

CPAP is considered the gold standard treatment for Obstructive sleep apnea syndrome (OSAS). CPAP therapy involves using a machine that delivers a continuous flow of air through a mask, keeping the airway open during sleep and preventing apnea episodes.1, 3, 4, 49 CPAP is highly effective for many individuals with OSAS and is often the first-line treatment prescribed by sleep specialists. However, despite its effectiveness, CPAP therapy may not be suitable or well tolerated by all OSAS patients. Some individuals may find it challenging to adjust to wearing the CPAP mask during sleep, experience discomfort, or feel claustrophobic. Compliance with CPAP can be an issue for some patients, leading to suboptimal treatment outcomes. In such cases, the MAD can serve as a useful alternative or adjunctive therapy for OSAS patients. While it may not be considered the gold standard, the MAD has several advantages and can be a valuable treatment option in such situations.

However, the therapy for OSAS with MADs is typically considered to be long-term or lifelong, as the condition often persists throughout a person's life. This calls for regular follow-up with a dentist and periodic monitoring of MADs. The effectiveness of MAD therapy can vary among individuals. Periodic follow-up visits with the dentist allow for an evaluation of the device's efficacy in managing OSAS symptoms. Adjustments to the device may be necessary based on the patient's response and any changes in sleep apnea severity. MADs are custom-made for each patient to ensure a proper fit and optimal effectiveness. Over time, changes in the dental or oral structures may occur, affecting the MAD's fit and function. Regular check-ups allow the dentist to adjust or modify the device as needed to maintain its effectiveness. MADs can sometimes cause side effects such as jaw discomfort, tooth movement, or changes in bite alignment. Regular follow-up visits enable the dentist to identify and address any emerging side effects promptly. Adjustments or modifications can be made to minimise discomfort and ensure the device remains tolerable and effective for the patient.

Another factor to be considered is the use of MAD in Class III malocclusion. MAD is not commonly given in Class III malocclusion cases. The MAD works by holding the lower jaw (mandible) in a more forward position during sleep to open the airway and reduce airway obstruction. While it may temporarily advance the mandible, its effects are limited to dental adjustments and do not have a significant impact on skeletal discrepancies. Class III malocclusion involves a mismatch in the size and positioning of the upper and lower jaws, which requires more comprehensive orthodontic or surgical interventions for correction.

Despite the valuable insights provided by the included studies in this review, there are several limitations that should be acknowledged. Firstly, the studies encompassed various publication years, indicating potential heterogeneity in terms of advancements in MAD treatment and diagnostic methodologies over time. Secondly, the diverse sample sizes across the studies introduce variability in the statistical power and precision of the estimates. Additionally, the mean age of participants varied, which may influence the generalizability of the findings across different age groups. The gender ratio, although reported differently among the studies, suggests a potential imbalance in the representation of males and females, limiting the generalizability of the findings to the broader population. Moreover, the studies employed different study designs, TMD assessment techniques, OSAS assessment techniques, MAD appliance types, and follow-up periods, which may contribute to inconsistencies and challenges in comparing the results across studies. The limitations in the TMD assessment techniques, such as the use of questionnaires or unspecified methods, may introduce measurement bias and affect the accuracy of the reported TMD outcomes. Lastly, the follow-up periods varied, ranging from months to years, which may impact the detection of the long-term effects of MAD treatment on TMD symptoms. Considering these limitations, cautious interpretation of the collective findings is necessary, and further well-designed studies with standardised methodologies are warranted to strengthen the evidence base in this area.

CONCLUSION

The overall findings indicate that MAD treatment for OSAS has varying effects on TMD-related outcomes. Some studies demonstrated a significant reduction in the severity and frequency of TMD symptoms following MAD treatment, particularly with the use of monobloc, hard, and heat-cured appliances. However, other studies did not observe significant changes in TMD symptoms or TMJ-related parameters. The type of MAD appliance, TMD assessment techniques, and follow-up duration emerged as potential factors influencing the treatment outcomes. Temporary increases in TMJ-related pain or symptoms at the beginning of the follow-up period were reported in some studies but later subsided. While the overall findings suggest a potential positive impact of MAD treatment on TMD symptoms, the variability across studies underscores the need for further research with standardised methodologies. Future studies should aim to address the limitations identified and provide a more robust understanding of the relationship between MAD treatment for OSA and the occurrence of TMDs.

AUTHOR CONTRIBUTIONS

Giuseppe Minervini: Conceptualization, methodology, software, validation, formal analysis, investigation; data curation, writing—original draft preparation, writing—review and editing, supervision. Mohammad Khursheed Alam: Conceptualization, software, validation, formal analysis. Usha Hegde: writing—original draft preparation, visualisation Mangesh Shenoy Panakaje: investigation; data curation. Gabriele Cervino: writing—review and editing, supervision. All authors have read and agreed to the published version of the manuscript.