The purpose of this study was to examine the efficacy of N-acetyl cysteine in the treatment of burning mouth syndrome. A control group of patients with burning mouth syndrome will receive a placebo. The effect of the therapy will be monitored with the help of the visual-analogue scale (VAS) and the oral health-related quality of life questionnaire (OHIP-14).

The research will include patients who come to the Department of Oral Medicine at the Faculty of Dentistry in Zagreb, and who have been diagnosed with burning mouth syndrome. It is planned to gather a total of 60 patients, 30 patients in the treatment group and 30 in the placebo group.

The purpose and protocol of the research will be explained to the patients. If they are willing to participate, they will sign an informed consent previously approved by the Ethics Committee of the Faculty of Dentistry. They will fill in the OHIP-14 questionnaire and the VAS scale, grading from 0-10, where 0 indicates a condition without symptoms, and 10 the strongest possible intensity of symptoms. They will be randomly assigned to a therapeutic or placebo group and will receive the medicine in an unmarked box. The drug will be taken for two months at a dose of 1200 mg per day. After that, they will come for a check-up and re-complete OHIP-14 and record the intensity of symptoms according to the VAS scale.

Inclusion Criteria:

• clinical diagnosis of burning mouth syndrome

Exclusion Criteria:

• pregnancy, breastfeeding or pregnancy planning
• anamnestic data about active gastric or duodenal ulcer
• decreased levels of serum iron or B vitamins