Since this kind of device forces the jaw to move forward for extended periods of time, and is braced by fitting to the user’s teeth, it isn’t uncommon for them to experience some initial discomfort that will go away after some time using the device. Side effects can include: Sore/Stiff Jaw, Toothache, Teeth Moving Out of Alignment, Hyper Salivation or Mouth Dryness. The best way to limit or avoid these side effects is to have a MAD custom made. This will ensure the best fit and comfort while wearing, and any side effect experienced will seem minor in comparison to the benefit of improved sleep that the user will have.