The study will be a randomized controlled trial (RCT) and be approved by the institute review board of the University of Tennessee Health Science Center. The study subjects will be composed of young adults 18-35 years old in order to control effects of age on caries. Also the subjects must be Caucasian or Africa American. Young adult patients will be recruited from the UTHSC dental clinics.The baseline visit include a dental exam by one of the investigators, standard preventive dental care (e.g cleaning, application of fluoride varnish), anthropometric measurements, oral health interview survey. 100 patients who meet all inclusion and exclusion criteria will be recruited after they sign an informed consent form. These patients will be randomly assigned to 1 of 2 study groups. Randomization assignment will be stratified by age and number of teeth with caries. Two study groups will be: 1.) plasma treatment group and 2) standard treatment group. For patients in standard treatment group, they will receive composite resin restoration for all decayed teeth and standard preventive treatment (cleaning and fluoride varnish application) at baseline. For patients in plasma treatment group, they will receive plasma treatment after cavity preparation, composite resin restoration, standard preventive treatment followed by plasma treatment for non-carious teeth. Standard preventive treatment and plasma treatment will be repeated on semi-annual (6-month) recall visits. All composite restorations will be placed according to the manufacturer's instruction. Only one composite commercially available will be used during the study.