Sorbitol is regarded as an inert polyol. Xylitol/Sorbitol gum (6g polyol/day) will be used for 5 weeks. Saliva samples will be collected before and after gum use. Studying and quantifying of 16 bacterial species belonging to the normal flora by DNA-DNA hybridizations and Real-time PCR will show how xylitol influenced the oral flora in general. Comparison of MS counts in unstimulated vs. stimulated saliva will show how xylitol affected the adhesivity of the MS.