radicular – refers to tooth root

radiograph – also known as an x-ray, image of bone and tooth structures produced through exposure to ionizing radiation

reimplantation – reinsertion of tooth into its socket following trauma that partially or completely removed it

reline – resurfacing of the tissue side of a removable denture to correct issue with fit

resin – material used in dental restorations and other dental treatments

resorption – loss of bone or structure

retainer – appliance used to ensure teeth do not return to prior misaligned state following orthodontic treatment

root – portion of the tooth that attaches the tooth into the gums and socket

root canal – pulp cavity inside the tooth root

root canal therapy – treatment of disease or injury to tooth pulp, generally involves the removal of part or all of the pulp and replacement with inert material

root planing – procedure used in the treatment of periodontal disease, involves deep cleaning of teeth at the roots to remove calculus and other substances

rubber dam – latex sheet used to isolate part of the mouth from saliva and potential contaminants during surgery