The investigators will perform a 1-year clinical trial measuring objective compliance during mandibular advancement device (MAD) treatment.

The investigators will enroll 50 patients that received treatment with a titratable, duobloc MAD (RespiDent Butterfly®, RespiDent, Nijlen, Belgium) and participated in the original study "Objective versus subjective compliance with oral appliance therapy for obstructive sleep apnea hypopnea syndrome", registered at Clinical Trials.gov (NCT01284881).

Active microsensors (TheraMon®,Handelsagentur Gschladt, Hargelsberg, Austria) are provided by the Handelsagentur Gschladt without any costs. The sampling interval of the recording will be done at a rate of 1 measurement per 15 minutes (every 900 seconds). Using this sample interval, the capacity of the active microsensor allows for data acquisition during a 100 day period.

A follow-up appointment is scheduled +/- 265 days after the start of the original study. A second follow-up visit is scheduled again 1 year after the start of the original study.

The objective measurement of MAD wear time (total hours of wear time and the mean hours of wear per night over the respective period) will be based on the assumption that the MAD has been worn when the chip records a temperature intraorally.

This clinical trial is an extension to trial 10/48/340, registered at Clinical Trials.gov (NCT01284881).

Inclusion Criteria:

• clinical diagnosis of sleep-disordered breathing
• started treatment with a titratable, duobloc mandibular advancement device
• participated in original study 10/48/340 (3 month follow-up of compliance during treatment with mandibular advancement device)

Exclusion Criteria:

• dental exclusion criteria for mandibular advancement devices
• medical contra-indications for mandibular advancement devices