An inhibitory effect of xylitol-containing preparation or solution at different concentrations with or without chlorhexidine on de novo plaque formation was clinically compared. Ten adult subjects aged 26-34 years old with apparently healthy gingiva showing no sign of periodontal disease were enrolled in this study. Test materials examined this study were: 1) distilled water (negative control) (DW) , 2) 65% xylitol

By using several kinds of mouthrinse, its inhibitory effect on the early plaque formation was examined for clinical consideration.Eight adult volunteers aged 25 to 35 years old with apparently healthy gingiva showing no sign of periodontal disease were enrolled in this study. For 14 consecutive days prior to the initiation of study, tooth surface cleaning and oral hygiene instruction were performaed by a dentist. All of these mechanical cleaning manipulations were abandoned at the beginning of experiment and mouthrinsing was performedwith 10 ml of different mouthrinses for one minute a time, twice a day. At the beginning of experiment and again on Day 4, the tooth surface was totally examined by means of Silness and LOe's Plaque Index (PH) . After ecamination on Day 4, tooth surface cleaning by the dentist and brushing by the subject were restarted, followed by dincontinuation of tooth cleaning after 10 days and than mouthrinsing with other mouthrinsing agents for subsequent 4 days. Five kinds of mouthrinse were used for this purpose, including 1) distilled water (DW) , 2) 0.12% chlorhexidine (CHX) , 3) acid water prepared by an electrolysis (AW) , 4) 0.1% stannous fluoride (SnF2) and 5) 0.02% cetylpyridium chloride-containing mouthrinse ( Dentor Systema, Lion) (CPC) .Various regions such as whole tooth surface, maxilla, mandible, anterior teeth, premolar, molar, adjacent surface and buccolingual side were examined for comparison. The average PlI value was 0.75 for CHX, 1.21 for AW, 1.20 for SnF2, 1.55 for CPC and 1.61 for DW. A statistical significant differences was observed between CHX and other individual mouthrinses, between AW and CPC or DW as well as between SnF2 and CPC or DW.Further, concerning all mouthrinses examined, the PlI value for anterior tooth region was lower than those of premolar and molar regions and the value for buccolingual region was lower than that for adjacent surface.