The study will be conducted in four groups of 20 patients in age of 20-30 years with complete dentition or single tooth loss in lateral regions, with masticatory muscle pain in the history or during examination and overuse and/or chronic tensing of the masticatory muscles. Patients will be randomly assigned to the groups.

Each person will be measured twice before and after use of selected anterior deprogrammer. The following assessment tools will be applied:

• surface electromyography of masseter and temporal muscles,
• intraoral pin-supported registration to draw a gothic arch.

Measurements will be made before and after intervention to assess the effect of anterior deprogrammer application on the tone of the selected masticatory muscles and condyles position in mandibular fossa. The first group (control) will be counsel with an explanation of the pathomechanism of masticatory muscles pain and preventive principles. In the second group, the Sliding Guide will be used for a period of 12-15 minutes, in the third Dawson B-Splint for 7 days, and in the fourth Kois deprogrammer for 14 days. Devices in group 3 and 4 will be used by patients for 24 hours a day, with breaks for oral hygiene procedures and eating/drinking.

The aim of the study is to evaluate the effectiveness of selected anterior deprogrammers.

Inclusion Criteria:

• age 20-30 years old
• complete dentition or single tooth loss in the lateral regions
• no severe systemic diseases
• masticatory muscle pain in the history or during examination
• increased masticatory muscles tension