C.E.T HEXtra Premium Chews with Chlorhexidine C.E.T. HEXtra Premium Chews with Chlorhexidine are patented and available exclusively through veterinarians. C.E.T. HEXtra Premium Chews combine the mechanical action of rawhide, the renowned antimicrobial power of chlorhexidine and the trusted C.E.T. name in a convenient, palatable chew for dogs.