In-vitro Retention of Mandibular Advancement Devices

Introduction: Mandibular Advancement Devices (MAD) can be custom-made (CM-MAD) in a dental laboratory and are worn at night. They advance the lower jaw in a non-invasive treatment of sleep-disordered breathing. Objectives: The forces required to seat and consecutively remove a CM-MAD will be measured and followed during 730 cycles, simulating a 2-year period, for 2 protrusive positions: 3 mm and 8 mm. Methods: Dental impressions were made (Impregum Pentasoft Medium, 3M ESPE AG, Germany) from which epoxy models were produced. The CM-MAD were made (Ercoflex, Pfalzgrafenweiler, Germany) using deep-thrown foil techniques (Ercodent, Idem) in a dental lab at 3 mm protrusion (n=2) and 8 mm protrusion (n=3). The devices were finished by the dental technician as per manufacturer's instructions. The models and CM-MAD were mounted in a hydraulic testing device (Dartec Series HC10, Dartec, UK) and the forces during seating (F_S) and removal (F_R) were continuously measured at 0.25 Hz crosshead speed @ 35°C in a dry environment. Results: Graph 1 shows a typical curve of F_S and F_R at the beginning (blue) and the end (red) of the test. Graph 2 shows the means and standard deviations for the recorded peak loads for both protrusions. After a 2-yr simulation there are no statistical differences between start and end forces in both groups. The 8mm protrusion requires statistically (t-Test, 0.95% CI) higher forces both during seating and removal (p<0.002). The forces needed to remove the CM-MAD are significantly higher than seating it, both for 3mm (p<0.03) and 8mm (p<0.00003) protrusion. Conclusions: For the present patient a lower protrusion results in lower dislocating forces. Lower forces are required to seat the device as compared to the removal of it.