Fear of dental pain, despite the modern analgesia methods, is still a trigger for many patients, resulting in fear of dentistry. Pain and anxiety during the oral surgery procedures are related to each other. Since fear is a multi-caused state, it is important to analyse each causing factor. Pain sensitivity, or fear of pain, in dental office is different in each person because of various psychological aspects, but also because of genetic code. Pain mechanism is a complex system with many different pathways, resulting in possibility to feel pain. It is interesting that despite the anxiety and stress having a positive correlation with perceived pain, high stress levels may reduce the pain sensation. Stress mechanism involves pain regulation, which may result in hyperalgesia or analgesia. During the stress many organ systems are activated, including the hypothalamic secretion of beta-endorphins, causing analgesia. Therefore, beta-endorphins are secreted by pituitary gland and then spreads to all body by diffusion. However, some studies suggest that beta-endorphins can be also produced by immune cells during the inflammation. Beta-endorphins act like natural morphines, binding the mu-receptors and activating the pain reduction system, therefore beta-endorphin plasma levels correlates with expressed pain. Various studies suggest that low level of peripheral plasma beta-endorphin levels act in chronic pain and trigeminal neuralgia development. Beta-endorphins have also been found as predictive factors to set the overtraining in sports, which result in muscles overloading because of euphoric and analgesic effects. Therefore, investigators have hypothesised that beta-endorphins could be a reliable factor determining patient's pain sensitivity or chronical non-painful processes. Also, since pain rating is usually based on self-reported questionnaires, beta-endorphins evaluation may be possible objective pain evaluation. However, most studies evaluating beta-endorphins levels are based on blood samples evaluation, and blood sampling is a painful and stressful event by itself. Beta-endorphins can also be assessed in saliva, however no previous studies have evaluated the relation between saliva beta-endorphins and plasma beta-endorphins in patients with different pain sensitivity. The aim of this study is to evaluate the relationship between plasma beta-endorphin and saliva beta-endorphin levels in patients with different pain sensitivity and patients with acute pain in maxillofacial region.

Study design

* Assessment: Healthy participants will be assessed in two groups regarding the evaluation of pain in common procedures in oral surgery self-reported questionnaire. The questionnaire is composed from 10 items, including perception of pain during surgical procedures and perception of post-operative healing caused pain. Procedures, such as anaesthetic injection, wisdom tooth removal, mobile tooth extraction, stitches removal, implantation and incision are composed into questionnaire. All items must be rated in numerical rating scales (NRS) from 1 - no pain to 10 - extreme pain, according to patient's assumption. Participants to further clinical trial will be randomly selected to form two groups with low and high pain rating. Further involved participants will have to repeat pain rating questionnaires to avoid possible accidental items rating. Cold pressor test will be enrolled for both groups in further described method.
* Cold pressor test. Participants will have to hold their hand up to the wrist in 5° temperature water, since it was suggested as a medium temperature giving the results of appropriate test time and felt pain. The water temperature below 15°C is known to stimulate nociceptors and provoke pain, however the testing time is relatively to long and the minimum temperature to this test of -2°C quickly provokes pain and it encumbers time evaluation. Digital thermometer will be used to ensure even temperature during the test with error of 0,5°C. The time of first painful sensation (pain threshold) will be noted and patients will be asked to self-report the felt pain in 1-10 NRS, afterwards the time of hand withdraw will be also recorded (pain tolerance) and the pain will be rated as described before. The maximum time of the test will be 4 minutes. If at the end of 4 minutes patient is still continuing, he will be asked to rate pain felt at 4 minutes moment in 10 points NRS and the test will be withdraw.
* Patients to control - acute pain group will be assessed randomly from those, coming for help because of acute pain in oral and maxillofacial region. Patients will be asked to voluntarily participate in research, with the aim of best patient's care and least interference to the needed treatment procedures. Only patients with clinically diagnosed cause of acute pain will be enrolled, even though it is stated that pain is present for patient, whenever a patient reports pain, with the aim to avoid any psychogenic pain. Also, patients will be asked to rate their present pain in NRS and only those assessing pain not less than 4 out of 10 points will be further included, since it is described as moderate pain at 4-6 points and severe pain at 7-10 points. Also, NRS is known as appropriate numerical method, if pain is empirically tested.
* Β-endorphins evaluation. Participants from non-acute-pain group will be tested the other day than cold-pressor test to eliminate the effect of pain pressor test stimulated stress, resulting in sympathetic system activation, including β-endorphins production. Before the sampling patients will be asked to calm and stay still until they feel relaxed to avoid possible stress effect on results. The saliva samples will be collected by participants with researcher's supervision in sterile test-tubes. It is known that β-endorphins can be found in saliva, however it is not commonly used in pain evaluating researches. Afterwards the blood sampling will be provided with the aim not to produce blood collection caused stress before saliva sampling. Blood samples will be used as control samples to ensure the presence of β-endorphins in organism at exact moment and to rate the blood β-endorphins concentrations relation with saliva β-endorphin levels.
* Β-endorphins sampling in control - acute pain group will be provided at the same day as acute pain is felt. This group will be used as control, since it is presumed that acute pain and stress increases β-endorphins levels. Saliva sample will be collected by participant under the researcher's supervision. Afterwards the blood sample will be collected.
* Laboratorial examination. Will be performed according to manufacturer's recommendations.