Somatosensory Investigation of Orofacial Pain Patients

Comorbidities The patients were interviewed by the same orofacial pain specialist using a questioner at the moment of the quantitative sensitive test.

Orofacial evaluation Instruments for orofacial evaluation. The questionnaires and exams were performed by one researcher only, a dentist, who ensured the clear understanding of the content by the participants before starting the protocol. All subjects underwent a standardized protocol for the evaluation of the orofacial region, including main complaint, pain characteristics [location, quality, duration, descriptors, intensity by the Visual Analog Scale (VAS), alleviation and aggravation factors], earache, headache, generalized body pain, sleep disturbances. Masticatory complaints related to parafunctional habits, laterality and the quality of mastication were also investigated. The intensity of masticatory discomfort was evaluated with the VAS. The intraoral examination included the evaluation of teeth, periodontal tissues, oral mucosa, tongue, lips, and facial skin, prostheses, occlusion and functional aspects, such as mandibular movements (mouth opening, protrusion, laterality) and temporomandibular joint (TMJ) exam (noises, spontaneous pain, or pain concomitant with movements). The muscular palpation of the head and neck was performed at the bilateral masseter, temporalis, digastrics, sternocleidomastoid, trapezius, splenius and suboccipitals. The periodontal exam was performed with adequate probes and the diagnoses made in accordance to the criteria of the American Academy of Periodontology. All participants underwent this detailed investigation for differential diagnosis with dental pain etiologies. Previous studies have shown that they can be associated with the main diagnosis of the patients.

Sensory investigation All subjects were interviewed about their perception of sensorial abnormalities such as numbness, dysesthesia, taste and smell complaints. The frequency of these abnormalities (absent, eventual, frequent, or constant) and the intensity (0-10 by VAS) were analyzed. This protocol is important for neuropathic and non-neuropathic pain diseases because somatic pain also presents sensitization and chronification.

QST. All subjects underwent a standardized protocol of QST which consists of 8 tests grouped as follows:

• gustative and olfactory thresholds;
• thermal detection thresholds for cold and warm sensations;
• mechanical detection thresholds for touch and vibration;
• mechanical pain sensitivity including superficial and deep pain thresholds. The somatosensory testing was performed at the 3 trigeminal branches (ophthalmic: fronte2 cm above the pupil, maxillary: cheek e 1 cm lateral to the nose wing, and mandibular: chin skin e 1 cm below the lip angle), at the hand dorsum (1 cm lateral to the thumb basis) and the anterior tibia skin (10 cm below the basis of patella). The evaluation was performed bilaterally in all subjects. All subjects were evaluated in the sitting position, with the head resting at a flat surface, and in a silent room with acoustic protection and the door closed. Only the participant and the researcher were in the room. All subjects were evaluated by the same researcher. The participants were oriented to keep the eyes closed during the exam, to be focused on the stimuli, and to their location (face and mouth) and characteristics. Only the researcher knew the order of the stimuli. Gustative thresholds: the following four substances, corresponding to the 4 tastes, were tested. For each test, one drop was applied at the tongue, starting with the low concentration, interleaved with one drop of distillate water, and the concentrations were tested until the subject had detected and identified the stimulus.