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: Theis 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