Form and function

Question 1

demands on teeth

Answer 1

cutting and grinding (biting, chewing)
function in aggressive environment (high cyclical contact stresses, chemically aggressive (pH), communication, aesthetics

Question 2

tooth tissue function

Answer 2

enamel: resilient surface to prevent wear of tooth & chemical resistance
dentine: toughness to grind food
cementum: protects dentine, and attachement site for P.L.
P.L= connects tooth to bone, shock absorber
Alveolar bone= lines tooth socket, holds teeth, connects w/ rest of body

Question 3

human teeth

Answer 3

4 types
incisors: 8 in children & adult
cuspids or canines: 4 in children & adult
biscuspids or premolars: 8 in adults
molars: 12 in adult, 8 children

Question 4

function & shape

Answer 4

incisors: for cutting food. compressive forces, brittle = chipping = sharp, single root. 155N

cuspids/canines: tearing, shearing food, compressive, little shear, conical, single root. 390N

bicuspids/premolars: crushing, grinding food, shear w/ compression, flattened w/ ridges, 1/2 roots per tooth. 288N

molars: crushing, grinding food, shear w/ compression, large & flattend, 2/3 roots per tooth. 1st=390N, 2nd=800N

Question 5

thermal properites

Answer 5

Enamel Conductivity 0.0092 J s-1 cm-2
Dentin Conductivity 0.0063 J s-1 cm-2
Coefficient of thermal expansion of teeth
11.4x10^6 K-1

metal based crown ceramics coefficient < metal = 0.5x10^-6 deg C-1. cooling the metal contraction > ceramic = ceramic in compression

Question 6

Optical properties

Answer 6

opacity: prevents transmission of light –> dentine is opaque
translucency: permits passage of light but disperses light –> enamel
transparency: allows passage of light w/out distortion
fluorescence: emission of light on excitation –> enamel under uv light