Oral health-related quality of life will be recorded with the Oral Health Impact Profile German 14 (OHIP-G14; Slade, 1997). The OHIP-G14 measures the subjective experience in terms of oral health (teeth, mouth, jaw and denture). It contains 14 questions (e.g. "Have you had painful aching in your mouth?") which are Likert scaled from 0 ("never") to 4 ("very often"). All questions refer to the last month. There are 7 different dimensions with two questions each (functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability and handicap). Values can be summed up to a total score, ranging between 0 and 56. Higher scores represent a more negative experience with one's oral health.

Pain perception will be calculated using the pain perception scale (Schmerzempfindungsskala, SES; Geissner, 1996). The SES is a self-assessment questionnaire for describing the subjective pain perception. It consists of two parts (part A with 14 items and part B with 10 item) which form two global scales: A = affective pain perception and B = sensoric pain perception. Every single item is based on adjective sentences like "I feel my pain is burning". Items are Likert scaled with a range from 1 ("this is not true") to 4 ("this is exactly true"). Higher values correspond to a painfully experience and represent a worse outcome. Item values are summed for every scale, therefore the scale range A is from 14 to 56 and the scale range B is from 10 to 40. Raw scale values can be transferred into the percent range.

Aspects of dream experience will be assessed using the Mannheim Dream Questionnaire (MADRE; Schredl et al., 2014) combined with a dream protocol. These include dream recall, dream types, attitude towards dreaming, what dreamers do with their dreams, and effects of dreaming on waking life. Every item measures a single aspect of dreaming and the response format gathers information about frequencies (e.g. "every morning" or "less than once a month") and contents (e.g. topics of nightmares in childhood). Scaling of the items varies between 3 to 8 points and they range between 0 (least degree of manifestation/frequency) and maximum 8 (highest degree of manifestation/frequency). No global score exists. There is one aggregate score concerning attitude towards dreams, that encompasses 6 items with a 5-point Likert scale (0 = "not at all" to 4 "totally"), e.g. "I think that dreaming is in general a very interesting phenomenon."

The stress coping questionnaire 78 (SVF-78; Janke et al., 1985) assesses individual long-term and constant strategies to cope with stress. The respondents determine by themselves how likely they apply 78 different coping styles. Coping styles refer to everyday situations. Every items starts with the phrase "If I was affected, disturbed or unsettled by someone or something", followed by a coping strategy (e.g. "I ask someone to help me"). Items are Likert scaled with a range from 0 ("not at all") to 4 ("very likely"). Higher values stand for a higher likelihood to apply the reaction in a certain situation. Two different main scales exist which sum up either positive strategies (adaptive strategies) or negative strategies (maladaptive strategies). Higher scores in positive strategies represent a stress reductive coping style. Higher scores in negative strategies represent a stress enhancing coping style. Raw values can be transferred to standardized T-scores.

The State-Trait-Anxiety Inventory (STAI; Laux et al. 1981) consists of 2 questionnaires with 20 items, respectively, and provides 20 different statements to describe ones feelings of anxiety at the moment. Half of the statements contain anxiety-present (e.g. "I feel over-excited and rattled"), the other half anxiety-absent items (e.g. "I am relaxed"). 4-point Likert scales are used with values from 1 ("not at all") to 4 ("very much so"). The trait anxiety scale comprises 20 statements to describe feelings of anxiety in general. 13 statements involve anxiety-present (e.g. "I lack self-confidence") and 7 anxiety-absent items (e.g. "I feel secure"). 4-point Likert scales allow data indication with values from 1 ("almost never") to 4 ("almost always"). The range of values is between 20 and 40 for each scale. The higher the score the more intense is the feeling of anxiety or, in relation to trait anxiety, the heavier is the anxiety disorder.

Subjective rating of the device characteristics will be evaluated by using a short questionnaire.

The presence of different forms of temporomandibular disorders will be verified by means of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD).