"the branch of dentistry concerned with the periodontal tissue and its disorders," 1948, from periodontia "periodontal membrane" (1914; see periodontal) + -ics. Periodontic (adj.) is attested by 1889.
"the branch of dentistry concerned with the treatment of irregularities of the teeth and jaws," 1849, from ortho- "straight, regular" + Greek odon (genitive odontos) "tooth" (from PIE root *dent- "tooth") + abstract noun ending -ia.
"act or fact of being stopped up," 1640s, from Medieval Latin occlusionem (nominative occlusio), noun of action from past-participle stem of Latin occludere (see occlude). Dentistry sense "position of the two sets of teeth relative to each other when the mouth is closed" is from 1880.
1590s, "of or pertaining to teeth," from French dental "of teeth" or Medieval Latin dentalis, from Latin dens (genitive dentis) "tooth" (from PIE root *dent- "tooth"). As "connected with or used in dentistry," 1826. In grammar, "formed or pronounced at or near the front upper teeth, with the tip or front of the tongue," 1590s. As a noun, "sound formed by placing the end of the tongue against or near the upper teeth," 1794. Related: Dentally; dentality.
"one whose occupation is to shave the beard and cut and dress the hair," c. 1300, from Anglo-French barbour (attested as a surname from early 13c.), from Old French barbeor, barbieor (13c., Modern French barbier, which has a more restricted sense than the English word), from Vulgar Latin *barbatorem, from Latin barba "beard" (see barb (n.)).
Originally also regular practitioners of minor surgery, they were restricted to hair-cutting, blood-letting, and dentistry under Henry VIII. The barber's pole (1680s) is in imitation of the ribbon used to bind the arm of one who has been bled.