March 24

Anatomy Notes March 24, 2009 Dentition Permanent teeth: 8 in each quadrant (32) 2 upper and 2 lower quadrants 4 types of teeth Incisors: designed for cutting, central and lateral Cuspids: canine; designed for tearing Bicuspids: premolars; 1st and 2nd bicuspids Molars: designed for grinding; (1st, 2nd, and 3rd molars) Baby Teeth Total of 20; (5 in each quadrant) Central incisor, lateral incisor, cuspid, 1st molar, and 2nd molar Molars in position of permanent premolars Teeth usually begin to erupt at 6 months or so (lower central incisors) and continue to ~2 years Permanent teeth begin to develop in utero as tooth buds just as primary teeth that prelude them Stage of mixed dentition (age 6- puberty): some primaries and some permanent Permanent teeth usually erupt beginning ~6 years till ~13 years, except for 3rd molars which may or may not erupt until ~25 or not at all Old age: edentulous tooth loss, alveolar process reabsorbed, jaw size reduced inferiorly-superiorly Parts of a tooth Root Crown: visible 1/3 of the tooth Neck: where the crown and the root meet Enamel: hard surface of crown Pulp: where nerve resides inside tooth Cementum: thin layer of bone where tooth is held in its socket Dental Occlusion Class 1 occlusion: normal relationship bt the molars of the dental arches; upper teeth overlap lower teeth anteriorly; lower 1st molar is ½ tooth advanced beyond upper 1st molar Class 1 malocclusion: orientation of molars is normal, but incisors are abnormal Cross bite: a lower tooth has more a buccal position than the upper tooth (single or group, anterior or posterior) Open bite: anterior upper and lower teeth do not meet with jaw closed, sometimes seen in severe tongue thrust Class II macocclusion (overbite): lower 1st molar is retracted at least 1 tooth behind upper 1st molar Class III malocclusion (underbite): lower 1st molar is more than 1 tooth advanced beyond upper 1st molar Common Terms Lingual: tongue side Buccal: cheek side Labioversion: tooth out of arch alignment toward the lips Linguaversion: tooth out of arch alignment toward the tongue Disoversion: tooth tilts away from the midline Mesioversion: tooth tilts toward the midline ***Table 7-2 pg. 305*** Function for speech Serves as a ?place of articulation? for some speech sounds (f,v) Serves as a cutting edge for the airstream of sibilants (s,z) Lends support for cheeks and lips thus affection resonance Malocclusion incisors and permanent teeth can lead to distorted speech