[Improvement of plaque score after oral hygiene instruction in patients with periodontitis].

The purpose of this study was to investigate the variations in oral hygiene conditions after oral hygiene instruction. We divided the patients with periodontitis into three groups according to the number of times oral hygiene instruction had to be given to achieve the O'Leary plaque control record (PCR) of 20%. The first group was those who achieved PCR 20% quickly (early achievement group). The second group was those who achieved PCR 20% gradually but slowly (slow achievement group). And the third group was those who showed no progress at all (non achievement group). Results showed that there were statistical differences among the average changes in PCR and residual plaque score (PS) of the teeth surfaces in each group. Especially the early achievement group were significantly superior to the other groups in improvement of PS of mandibular lingual surface with one oral hygiene instruction. We also have investigated differences in the probing depth, age and sex at initial treatment among these three groups. The average probing depth at initial treatment was significantly deeper in the non achievement group than in the early achievement groups, and there were more males than females in the early achievement and non achievement groups.