Response to letter to the Editor: Look at the elephant! Commentary on 'Prevalence of temporomandibular disorders in adult obstructive sleep apnoea patients: A cross-sectional controlled study'.

Obstructive sleep apnoea and temporomandibular disorders are complex pathologies. Considering dento-skeletal occlusion as their main predisposing factor could be detrimental for optimal patient care.

Prevalence of temporomandibular disorders in adult obstructive sleep apnoea patients: A cross-sectional controlled study.

BACKGROUND: Obstructive sleep apnoea (OSA) is characterised by partial or complete obstruction of the upper airways during sleep and it has been associated with temporomandibular disorders (TMDs) on the basis of several pathophysiological hypotheses. OBJECTIVES: To assess the prevalence of TMDs in a population of patients affected by OSA compared to a control group of subjects not affected by OSA. METHODS: A cross-sectional controlled study was conducted on a group subjects studied by polygraphy (PG) at the snoring section of the ENT department, Sant'Orsola-Malpighi Hospital - University of Bologna. Patients who received a diagnosis of OSA were included in the study group and subjects with a negative PG diagnosis for Sleep Disordered Breathing and PG respiratory pattern that did not suggest the occurrence of sleep disorders were enrolled in the control group. Both the subjects included in the study group and the control group underwent an examination following the Diagnostic Criteria for Temporomandibular Disorders Axis I and II. RESULTS: Forty-three OSA patients (29 M, 16 F, mean age 52.26 ± 11.40) and 43 healthy controls (25 M, 18 F, mean age 49.95 ± 7.59) were included in the study. No significant differences were found between groups in demographic data. TMD prevalence and Axis II results did not differ between groups. CONCLUSIONS: This paper does not highlight a higher prevalence of TMDs in adults with OSA compared to healthy controls. Further high-quality studies are needed to confirm the results and to give possible pathophysiological explanations, providing reliable evidence.

Maximum voluntary retrusion or habitual bite position for mandibular advancement assessment in the treatment of obstructive sleep apnoea patients.

BACKGROUND: There is no consensus on whether the range of mandibular advancement for the construction of mandibular advancement devices in obstructive sleep apnoea (OSA) patients should be measured from a starting position of maximum voluntary retrusion or habitual bite position. OBJECTIVE: The purposes of this study were to investigate the differences in mandibular advancement registrations starting from maximum voluntary retrusion or from habitual bite position and to evaluate the reliability of these assessments. METHODS: A retrospective cohort analysis of 126 patients with OSA was performed. All patients had their mandibular range of motion evaluated twice (starting from maximum voluntary retrusion and from habitual bite position) through the George Gauge before undergoing drug-induced sleep endoscopy. The Dahlberg formula and paired t test were used to calculate random and systematic errors of dental positions assessment. Test-retest reliability was quantified using the intra-class correlation coefficient (ICC). RESULTS: The mean mandibular range starting from maximum voluntary retrusion and from habitual bite position were 12.49 ± 2.19 mm and 7.68 ± 2.29 mm, respectively, with a mean distance between the two starting positions of 4.81 ± 1.75 mm. No systematic error was found (P > .05), and random errors ranged from 0.30 to 0.95 mm. ICC values were excellent for maximum voluntary protrusion (ICC = 0.986) and maximum voluntary retrusion (ICC = 0.956), whereas habitual bite position showed a good value (ICC = 0.818). CONCLUSION: The difference between maximum voluntary retrusion and habitual bite position is potentially relevant. Maximum retrusion is advisable as starting point of the mandibular advancement registration since it provides a more reliable measure.

Relationship between cephalometric parameters and the apnoea-hypopnoea index in OSA patients: a retrospective cohort study.

OBJECTIVE: The purpose of this study was to assess the relationship between cephalometric parameters and apnoea-hypopnoea index (AHI) controlling for the effect of gender, age, and body mass index (BMI) on a large sample of patients with obstructive sleep apnoea (OSA). METHODS: This retrospective cohort study was conducted on the lateral cephalograms of 253 Caucasian adult OSA patients. Cephalometric analyses were performed using 14 parameters for skeletal and soft tissue morphology, including antero-posterior and vertical jaw relationships, hyoid bone position, soft palate length and thickness, airway space, and tongue length and height. A hierarchical regression was run to examine the amount of variability in AHI that cephalometric variables explained after controlling for patients' general characteristics (gender, age, and BMI). RESULTS: After controlling for gender, age, and BMI, the increase in AHI variance accounted for by cephalometric parameters was equal to 0.103. Among the cephalometric variables, only MP-H and PNS-P were statistically significant (P < 0.05). LIMITATIONS: Given the retrospective nature of the study, it is difficult to assess whether other confounding variables not considered in the present study could have influenced the relationship between cephalometric parameters and AHI. CONCLUSIONS: This study revealed the existence of a relationship between OSA severity and some cephalometric parameters. Indeed soft palate length and vertical position of the hyoid bone were significant predictors of AHI in adult Caucasian OSA patients.

Dentoskeletal effects of oral appliance wear in obstructive sleep apnoea and snoring patients.

OBJECTIVES: To evaluate the dentoskeletal changes associated with long-term and continuous mandibular advancement device (MAD) use in sleep-related breathing disorder patients. METHODS: Cephalometric measurements and three-dimensional model analysis were performed at baseline and after 3.5 ± 1.1 years in 20 snoring and obstructive sleep apnoea patients treated with the Silensor® appliance. Intra-group differences were compared using paired t-test or Wilcoxon signed-rank test. A regression analysis was performed for variables that showed a statistically significant difference between time points to evaluate the influence of treatment time and patient's initial characteristics on their variations. The statistical significance was set at P < 0.05. RESULTS: At cephalometric assessment, the maxilla revealed a significant decrease in horizontal position (SNA: -0.4 ± 0.72 degree, P = 0.021) and a significant retroclination of the upper incisor (-1.59 ± 1.07 degree, P < 0.001), while the mandible displayed a significant downward rotation (0.88 ± 1.28 degree, P = 0.006) and a proclination of the lower incisor (2.27 ± 1.38 degree, P < 0.001). Model analysis showed a decrease in upper total space discrepancy (-0.66 ± 0.72 mm, P < 0.002), overjet (OJ; -0.34 ± 0.47 mm, P < 0.011), and overbite (-0.4 ± 0.52 mm, P < 0.004). In the regression analysis, treatment time influenced the lower incisor inclination (Beta = -0.713, P = 0.018) and OJ (Beta = -0.218, P = 0.018); patients' initial characteristics had an effect on OJ (Beta = -0.195, P = 0.011). LIMITATIONS: A larger sample size could increase the generalizability of the findings. CONCLUSION: MAD wear after a mean of 3.5 years determines statistically significant but clinically irrelevant dentoskeletal changes. Their potential occurrence should be thoroughly discussed with patients; regular follow-up visits by a specialist experienced in dental sleep medicine are also mandatory during treatment in addition to polysomnographic examinations.

Antero-Posterior Mandibular Excursion in Obstructive Sleep Apnea Patients Treated with Mandibular Advancement Device: A Retrospective Cohort Study.

Since obstructive sleep apnea (OSA) management with a mandibular advancement device (MAD) is likely to be life-long, potential changes in mandibular movements during therapy should be investigated. The purpose of this study was to use a method that has already been shown to be reliable in order to determine whether the range of antero-posterior mandibular excursion, the procedure upon which MAD titration is based, varies between baseline (T0) and at least 1 year of treatment (T1). The distance between maximal voluntary protrusion and maximal voluntary retrusion determined using the millimetric scale of the George Gauge was retrospectively collected from the medical records of 59 OSA patients treated with the MAD and compared between T0 and T1. A regression analysis was performed to evaluate the influence of treatment time, MAD therapeutic advancement and the patient's initial characteristics in excursion range variation. A statistically significant increase of 0.80 ± 1.52 mm (mean ± standard deviation, p < 0.001) was found for antero-posterior mandibular excursion. The longer the treatment time (p = 0.044) and the smaller the patient's mandibular excursion at T0 (p = 0.002), the greater the increase was. These findings could be explained by a muscle-tendon unit adaptation to the forward mandibular repositioning induced by the MAD. During MAD therapy, patients can develop a wider range of antero-posterior mandibular excursion, especially those with a smaller initial excursion capacity.