国外口腔解剖乳牙.ppt

IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETH
1.Maintenance of a normal appearance. 2.Formulation Efficient mastication of food. 3.of clear speech. 4.Maintenance of a proper diet. Missing or badly decayed teeth may be one reason that young children reject foods that are difficult to chew.
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
10-The root canal of deciduous teeth are very fine.
ON THE ANTERIOR TEETH
11-Usually there are no depressions or perikymata on the labial surface of the crown of the incisors. These surfaces are smooth.

The deciduous dentition comprises fewer teeth than the permanent dentition with a total of TEN maxillary and TEN mandibular teeth.
They are as follows, in order of position from the midline: A-First (central) incisor. B-Second (lateral) incisor. C- Canine.
IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETH

The deciduous, primary, or, as they often referred to colloquially, (MILK) teeth, have a relatively short life-span before they exfoliated to be replaced by the permanent teeth. This usually occurs between the ages of 6 and13 years.
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
2-The enamel of the deciduous teeth is whiter and more opaque, which gives the crown a lighter colour than that of the permanent teeth.
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
6-In newly erupted deciduous teeth, the cusps tend to be more pointed.
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
ON THE POSTERIOR TEETH
24-The roots are widely spread beyond the confines of the crown to allow for the developing permanent successors.
ON THE POSTERIOR TEETH
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
5- Deciduous teeth have a pronounced cervical margin. The enamel bulges, instead of tapering gently, at the cemento-enaml junction, which is straighter than in the permanent teeth. This cervical bulge is accentuated in the mesiobuccal area of deciduous molars.
ON THE ANTERIOR TEETH
12-There are no mamelones on the incisal edges.
ON THE ANTERIOR TEETH
13-The cervical ridge on the facial surfaces is prominent.
ON THE ANTERIOR TEETH

The deciduous incisors and canines have permanent successor but the first and second deciduous molars are replaced by the first and second premolars respectively.
14-The cingulae are prominent or seem to bulge and occupy about one third of the cervicoincisal length lingually
15-The root is narrow mesiodistally.
ON THE POSTERIOR TEETH
3-The enamel of the deciduous teeth is more permeable and more easily worn down. The degree of permeability is lessened after the start of root resorption.
C B A
D-First molar. E-Second molar.
D E

The shorthand formula for the deciduous teeth is as follows:
I2
2பைடு நூலகம்
C 1 M2 =10
1 2
GENERAL CHARACTERISTICS
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS TEETH AND PERMANENT TEETH
4-The DEPTH OF ENAMEL is more consistent and thinner than in the permanent teeth, being from 0.5mm to 1.00mm thick.
7-The roots of the deciduous teeth are shorter, less strong and lighter in colour than those of the permanent teeth.
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH
9-The pulp chambers are larger than in the permanent teeth and follow the exterior morphology of the tooth more closely, there tends, therefore to be less depth of dentine.
16- The molar crown have a narrow chewing (occlusal table) buccolingually. 17- The molars occluosal surfaces are shallow. In other words, the cusps are short, the ridges are not pronounced,and the grooves are correspondingly not as deep.
ON THE POSTERIOR TEETH
20- There are few grooves or depressions in all surfaces of the crowns.
ON THE POSTERIOR TEETH
21-The cervical ridge is prominent mesially (it is easy to distinguish rights from left ).
8-The roots of anterior deciduous teeth are longer in proportion to the crown. The roots of posterior teeth are more divergent to allow for the developing permanent successor. They flare out from each other wider than the crown measurement ,and form a minimal common root trunk.
25-Roots are thin or slender.
ON THE POSTERIOR TEETH