What is right mandibular sinus disease?

Don't know... The mandible is the jaw, and there is no sinus in the jaw. Are you sure you don't mean right maxillary sinus disease? If so, that means the sinus (air-filled space) beneath your cheek bone above your upper teeth. As far as the 'disease' part, the most common thing is inflammation, or sinusitis, which can cause stuffy nose, pain/pressure feeling, +/- infection. Ask your md for clarification.