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Articulation and Resonance Lab 2
Dentition (Noncadaver Lab)
To the Instructor:
This lab is best performed using dental impressions, especially if they show pre-orthodontia
malocclusions and other malformations. Dental labs, dentists, and dental hygienists are great
sources for finding these impressions, which are wonderful study guides for your students.
You’ll probably find that individual students will donate their impressions when they see how
much good they do! You might also ask for donations of deciduous teeth while you’re at it! This
lab guide gives you general terms and discussion points. You may wish to add some of the
following images from the Image Library to the lab guide so that students will have them at hand
as a reference in the lab.
Figure
4-20
Upper and lower arches
4-20
Photo of adult arch
4-22
Landmarks of tooth
4-25
Surface references of teeth and dental arch
4-20
Types of teeth
4-23
Comparison of deciduous and permanent arches
4-23
Panaflex of emergent permanent teeth in deciduous arch
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Terms of occlusion
4-25
Terms of malorientation
4-25
Radiograph of prognathic mandible
4-20
Dental impressions revealing marked malorientations secondary to tongue
thrust
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Articulation and Resonance Lab 2
Dentition (Noncadaver Lab)
You will want to familiarize yourself with the terminology, spelling, structures, and landmarks
indicated below.
Generally:
incisors
cuspids, canines
bicuspids
molars
Structure:
crown: visible; projects above gums; 1/3 of tooth
root: embedded in alveolar process; 2/3 of tooth
cementum: thin layer of bone holding tooth in
neck: juncture of root and crown
dentin: ivory of tooth; bulk of tooth; calcified tissue; contains nerves in pulp
enamel: very dense, hardest substance in body; covers crown to root (not on root); resists
abrasion; thickest on grinding surface
Types of teeth:
central incisors: chisel-shaped; have only one root; lowers smaller than upper; lowers are
overlapped by uppers
lateral incisors: smaller than centrals; shorter root than centrals
canines (cuspids, eye teeth): lateral to lateral incisors; large; single point or cusp; good
solid root; upper larger than lower
premolars (bicuspids): first and second bicuspids in adult arch only; two cusps (points);
may have one or two roots
molars: largest; 12 in permanent arch; large, rectangular crowns; uppers smaller than
lowers. First molar is largest;
third molar (wisdom tooth) is smallest
first molar has four cusps
second molar has three or four cusps
third molar has three cusps
Tooth development:
Growth period:
formation of tooth bud (five weeks embryonic)
deposition of enamel and dentin (seven weeks embryonic)
Calcification:
enamel and dentin hardened by calcium
Eruption:
intraosseous eruption
erupts through alveolar process
calcification still occurring
bony tissues between teeth ossify to form alveoli
Clinical eruption:
tooth migrates into oral cavity
can see tooth through gum
Attrition: wear; pressure, strain wear away enamel
premature attrition can be caused by ice, pipes
wear occurs on occlusal surface, also on interproximal surfaces if adjacent teeth touch
continuous eruption
Arches:
adult = 8 per half arch; child = 5 (missing 2 bicuspids, 1 molar)
Deciduous arch:
smaller and fewer
10 teeth in each arch
each half arch has
1 central vs. 1
1 lateral vs. 1
1 canine vs. 1
2 bicuspids (none in deciduous)
2 molars vs. 3
start getting teeth at six to seven months; finish by end of second year
start shedding at six to seven years
healthy deciduous arches necessary for correct spacing of permanent teeth
Permanent arch:
successional teeth: those replacing deciduous
successionals are mature by the time deciduous erupt
when ready to erupt, push up to contact deciduous; osteoclasts develop at point of
contact; root is absorbed; deciduous tooth is shed
superadded teeth: those in addition to deciduous
bicuspids and third molar
supernumerary teeth: usually upper incisors
not supposed to be there (twinning: duplicate central incisor)
Occlusion: Mandible, teeth
Mandibular occlusion:
Class I occlusion: neutroclusion (normal orientation)
upper molars slightly posterior to lower
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Class I malocclusion: normal molar orientation but deviation in anterior portion of
arch
Class II malocclusion: mandible retruded or retracted (relative micrognathia)
Class III malocclusion: mandible overlaps maxilla (protruded mandible)
persistent open bite: cannot occlude in front
persistent closed bite: cannot occlude posterior teeth
Dental orientation (malocclusion)
axioversion: general class of orientation; tooth tipped on long axis with improper
axial inclination; includes distoversion, mesioversion, labioversion,
linguaversion
distoversion: tilting away from incisors along alveolar process
labioversion: tilting toward lip
linguaversion: tilting toward tongue
mesioversion: tilting toward incisors along alveolar ridge
infraversion: insufficient eruption to permit occlusion
supraversion: excessive eruption
torsiversion: rotated on axis