Lesson
4
Subject: 1 .Anatomy of individual teeth.
2. Revision lesson.
3. Salivary
glands.
Anatomy of Individual Teeth
A
collection of extracted teeth in good condition is a great help in learning
anatomy.
Incisors have one root and flattened chisel-shaped
crowns. The upper crowns are much wider than their lower counterparts.
The upper
lateral incisor crown is smaller than the upper central; but the lower lateral
crown is slightly larger than the lower central.
These have large conical crowns and one
long root. The upper canine is larger than the lower
and has the longest root of the whole dentition.
The upper first premolar has two roots, one buccal and
one palatal.
The remaining premolars have one root. Each premolar
has two cusps, one buccal and one palatal or lingual.
The cusps of upper premolars are much bigger than lowers and are almost equal in
size. The lingual cusp of lower premolars is
much smaller than the buccal cusp.
Upper molars have three roots, two buccal and one palatal. The buccal roots are mesial
and distal.
Lower molars have two roots, one mesial and one distal.
Upper molars have four cusps, two buccal and two palatal. Their crowns are characterised by an oblique ridge which runs from the mesio-patatal cusp to the disto-buccal
cusp. Upper first molars often have an extra cusp on their mesio-palatal
surface.
This is called the cusp of carabelli.
Lower first molars have five cusps, three buccal and two lingual. Lower second molars
have four cusps, two buccal and two
lingual.
First molars are the largest teeth of all.
Third molars are very variable in size and number of roots and cusps. Usually
they are the smallest molars and their roots are frequently fused together.
Deciduous molars are like miniature
permanent molars. They have the same number of roots but their crowns are much
whiter and more bulbous than permanent ones. To provide space for the
developing premolars, the roots of
deciduous molars are more divergent than those of permanent molars.
Occlusion of the Teeth
When the upper and lower teeth are closed
together, they are said to be in occlusion, The arch
of the upper teeth is larger than the lower; thus upper teeth
overlap the lowers on the buccal side.
Lower buccal cusps accordingly bite into
the fissure between upper buccal and
palatal cusps.
At the midline
the mesial edges of upper and lower central
incisors form one straight vertical line. As lower central incisors are much
narrower than uppers, all the remaining lower teeth occlude with two upper
teeth — their corresponding upper tooth and the one in front.
Functions of the Teeth
Incisors and canines are for cutting up
food into smaller pieces ready for chewing.
Premolars and molars are for
chewing; their cusps grinding the food into a soft mass suitable for
swallowing.
Parts of a Tooth
All teeth no matter what type consist of
the same three parts: a root embedded
in a socket in the alveolar process of a jaw bone, a crown projecting upward from the gum and a narrowed neck between
the root and the crown, which is surrounded by
the gum. The incisors, canines and premolars have a double root. The lower molars
have two flattened roots, and the upper molars
have three conical roots. At the apex of each root is the apical foramen, which
leads successively into the root canal and root cavity.
Each tooth is composed of dentine, enamel,
cement and pulp. The dentine is the extremely sensitive yellowish portion
surrounding the pulp cavity. It forms the bulk of the tooth. The enamel is the
insensitive white covering of the crown. It is the hardest substance in the
body. In order to cut through enamel, a dentist's drill spins at about half a
million revolutions per minute. The cement is the bonelike covering of the neck
and root. The pulp is the soft core of connective tissue that contains the
nerves and blood vessels of the tooth.
Teeth are derived from the same tissue as
the skin. The enamel is formed from the embryonic epidermis, and the dentine,
pulp, and cement are formed from the embrionic dermis.
The gum also called the gingiva is the firm connective tissue covered
with mucous membrane that surrounds the alveolar process of the teeth. The gums
are usually attached to the enamel of the tooth somewhere along the crown, but
the gum line gradually recedes as we get older.
LITERATURE:
a) Þä³íà
ª.ª., Ïîòÿæåíêî Ë.Â. ϳäðó÷íèê àíãë³éñüêî¿ ìîâè. –
Ê., Âèùà øêîëà, 1994.
b) Ãóðñüêà À.². Àíãë³éñüêà ìîâà äëÿ
ñòóäåíò³â-ìåäèê³â. Ëüâ³â: Ñâ³ò, 2003.
c) Äåì÷åíêî
Î. É., Êîñòÿê Í.Â.
Àíãë³éñüêà ìîâà äëÿ ñòóäåíò³â-ìåäèê³â. Òåðíîï³ëü: Óêðìåäêíèãà,
2001.
d) Ìóõ³íà Â. Â. Àíãë³éñüêà ìîâà äëÿ ñòóäåíò³â-ñòîìàòîëîã³â.-Ì., 2003.
TEST SAMPLE:
Òåìà: Anatomy of
individual teeth.
1. Âèáåð³òü åêâ³âàëåíò ñëîâà “ÿçèê”
A. tooth
B. jaw
C. tongue
D. gum
E. gingiva
2. Âèáåð³òü ïðàâèëüíèé âàð³àíò íàïèñàííÿ ñëîâà “òð³ùèíà”
A. fissure
B. fissure
C. fishe
D. fisher
E. fisshe
3. Âèáåð³òü ïðàâèëüíèé âàð³àíò ïåðåêëàäó
ñëîâîñïîëó÷åííÿ “right angles”
A.
ïðàâ³ êóòèêè
Â. ë³â³ êðà¿
C.
ïðÿì³ êóòèêè
D.
ïëîñê³ êóòèêè
Å. íåïðàâèëüí³ êðà¿
4. Âèáåð³òü ñëîâî, ÿêå íàéêðàùå äîïîâíþº çì³ñò ðå÷åííÿ: The…is the part visible in the mouth
A. crown
B. jaw
C. neck
D. root
E. apex
5.
Âèáåð³òü ïîíÿòòÿ, ÿêå â³äïîâ³äຠâèçíà÷åííþ: The
junction of crown and root is called the …
A. neck
B. root
C. crown
D. apex
E. pulp