Methylene Blue and Experimental Gingivitis

Objective: Redox agents such as methylene blue (MB) have previously been shown to reduce plaque anaerobes and periodontitis. This study evaluated its ability to inhibit experimental gingivitis.

Method: Seventy-seven subjects completed a double-blind parallel-group study comparing 0.1% MB, 0.12% chlorhexidine gluconate (CH) and placebo (PL) mouthwashes for their ability to prevent gingival inflammation and bleeding. Subjects were initially screened for gingival inflammation and bleeding and were accepted onto the pre-experimental phase of the study provided they had more than 2 bleeding sites in the 3-7 region of one mandibular quadrant. After receiving a scale and polish and oral hygiene instruction, compliant subjects followed a strict oral hygiene regime for the next 21 days in order to achieve clinically healthy gingivae. Subjects with > 5 bleeding sites per randomly assigned test quadrant were then withdrawn whilst the remainder entered the experimental phase of the study. During this phase, plaque was allowed to accumulate in the test quadrant by protecting the teeth with a toothshield during brushing. Subjects rinsed with 10ml of randomly assigned mouthwash for 1 minute twice daily, prior to brushing the remainder of the dentition with a fluoride toothpaste. After 21 days gingival inflammation and bleeding were reassessed.

Results: Analysis of Covariance was used to assess differences between product groups. The increase in gingival inflammation after 21 days was significantly less with CH (increment 0.002; p < 0.0002) and MB (increment 0.30; p < 0.03) than for PL (increment 0.45). A similar effect was observed for the increase in bleeding sites, which for CH was significantly less (increment 0.27; p < 0.03) and marginally less for MB (increment 0.33; p > 0.05) compared with PL (increment 0.43).