20 or 30 is removed and fitted to the user 39 s mouth teeth and gums just like an eva appliance as is well known it is also well known that illness infection tooth decay and or periodontal disease is caused by bacteria fungus yeast and virus these microbials can grow and multiply on dental appliances when the appliances are being stored between uses as well as when the appliance is actually being worn or used antimicrobial substances which are non toxic and free of heavy metal or resisting the growth of the microbials may include chlorinated phenol e g 5 chloro 2 2 4 dichlorophenoxy phenol polyhexamethylene biguanide hydrochloride phmb doxycycline chlorhexidine metronidazole thymol eucalypol and methyl salycilate triclosan u00ae from siba giegy of switzerland is also available incorporating an antimicrobial agent into the low density polyethylene during the manufacture of the dental appliance 10 20 or 30 is achieved by incorporating the agent into the synthetic polymeric master batch the antimicrobial agent is suitably placed into the batch in a concentration as high as 10 which will permit a let down ratio resulting in the final concentration of the antimicrobial agent and the dental appliance of about 0 005 to about 2 by weight by encapsulating the antimicrobial agent into the polymer batch mix the agents survive molten temperatures approximately or above 350 u00b0 f and thus the antimicrobial agent loses none of its biocidal properties in the formation.