Mandibular Torus as a New Index of Success for Mandibular Advancement Devices

Abstract

Background: In obstructive sleep apnoea (OSA), treatment with mandibular advancement devices (MADs) reduces patients' Apnoea-Hypopnoea index (AHI) scores and improves their sleepiness and quality of life. MADs are non-invasive alternatives for patients who cannot tolerate traditional continuous positive airway pressure (CPAP) therapy. The variability of responses to these devices makes it necessary to search for predictors of success. The aim of our study was to evaluate the presence of mandibular torus as a predictor of MAD efficacy in OSA and to identify other potential cephalometric factors that could influence the response to treatment.

Methods: This was a retrospective cohort study. The study included 103 patients diagnosed of OSA who met the criteria for initiation of treatment with MAD. Structural variables were collected (cephalometric and the presence or absence of mandibular torus). Statistical analysis was performed to evaluate the existence of predictive factors for the efficacy of MADs.

Results: A total of 103 patients who were consecutively referred for treatment with MAD were included (89.3% men); the mean age of the participants was 46.3 years, and the mean AHI before MAD was 31.4 (SD 16.2) and post- MAD 11.3 (SD 9.2). Thirty-three percent of patients had mandibular torus. Torus was associated with a better response (odds ratio (OR) = 2.854 (p = 0.035)) after adjustment for sex, age, body mass index (BMI; kg/m²), the angle formed by the occlusal plane to the sella-nasion plane (OCC plane to SN), overinjection, and smoking. No cephalometric predictors of efficacy were found that were predictive of MAD treatment success.

Conclusions: The presence of a mandibular torus practically triples the probability of MAD success. This is the simplest examination with the greatest benefits in terms of the efficacy of MAD treatment for OSA.

Keywords: cephalometry; mandibular advancement devices; mandibular torus; obstructive sleep apnoea.

Figure 1

Sagittal cephalometric view showing the reference parameters (points, planes, angles, and Cartesian coordinates) used in the study. Cephalometric points. Na: nasion, most anterior point of the fronto-nasal suture; S: sella, geometric centre of the sella turcica; Eb: base of the epiglottis; H: most anterior point of the body of the hyoid bone; TT: tip of the tongue; RGn: most posterior point of mandibular symphysis at the level of the mid-sagittal plane; CV4IP: most inferior point of the C4; Co: most anterior and superior point of the mandibular condyle; Gn: most anterior and inferior point of the mandible at the level of the mid-sagittal plane of the symphysis; B: most posterior point of the anterior concavity of the mandibular symphysis; Go: most posteroinferior point of the mandible; A: most posterior point of the anterior concavity of the maxillary bone. Me: inferior most point of mandibular symphysis. Po: most superior point of the external auditory canal.

Figure 2

Mandibular torus.

Figure 3

Patient flow chart.

Figure 4

ROC Curve Model 1.

Figure 5

Lateral neck X-ray of one of our patients showing Hyoid-C3 vertebra distance.