A clinical study was conducted among 200 adult males and females to compare the intrusive gingival index (GI) for estimating gingivitis with the nonintrusive and only visually applied papillary-marginal-gingivitis index (PMGI). The GI examinations were performed by a senior examiner with long experience and a junior examiner, while the PMGI was graded by only a senior examiner with long experience. A 4th examiner was included for grading bleeding sites by gentle intrusion at the orifice of the gingival crevice. Following the baseline examination by all examiners, the subjects were randomly assigned to either a group that received an oral prophylaxis immediately or to a group that received an oral prophylaxis 6 weeks after the baseline. All subjects were regraded by all examiners 4 days after the 2nd group received a prophylaxis. This delayed prophylaxis design created a difference in the responses between treatment groups. Both the GI examiners and the PMGI examiner concluded there was significantly less gingivitis in the group receiving a prophylaxis second. There were also significantly fewer bleeding sites in the group receiving a prophylaxis second as determined by both GI examiners and the bleeding-sites examiner.