Oral burning can have a multitude of reasons. Recent neurophysiologic study results suggest that a primary burning mouth disorder (BMD) may be a peripheral and/or a central neuropathic disorder. The aim of this study is to first identify patients with a primary burning mouth disorder by excluding other possible causes for oral burning. By means of qualitative and quantitative sensory testing and a gustatory examination in the individual patient the investigators want to find out whether neurosensory differences exist between patients with a primary BMD and controls and whether gustatory and neurosensory deficits always coexist in BMD-patients.