The effect of 50 per cent phosphoric acid on oral soft tissues

The effect of 50 per cent phosphoric acid on oral soft tissue was studied in two investigations. In the first investigation the buccal mucosa of three rats was studied after contact with phosphoric acid for 1, 5 and 10 minutes respectively. The material of the second investigation comprised of 26 patients from whom 31 pairs of premolars were planned to be extracted for orthodontic reasons. Phosphoric acid was applied for 90 seconds on one tooth and its buccal gingival margin in each pair of teeth. After a period varying between 1 and 7 days the tooth and a section of the gingiva were extracted and prepared for microscopic examination. The second tooth in each pair was the control tooth. The study showed that only a relatively long acid application time resulted in obvious histologic changes in the mucous membrane. The phosphoric acid gave no demonstrable gingival reaction in the patients.