口腔解剖生理学之国外---THE_DECIDUOUS_DENTITION乳牙-精选文档.ppt
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1、INTRODUCTION,The word deciduous comes from a Latin word meaning to fall off. Deciduous teeth fall off or are shed like leaves from a deciduous tree.,The deciduous, primary, or, as they often referred to colloquially, (MILK) teeth, have a relatively short life-span before they exfoliated to be replac
2、ed by the permanent teeth. This usually occurs between the ages of 6 and13 years.,The deciduous incisors and canines have permanent successor but the first and second deciduous molars are replaced by the first and second premolars respectively.,The deciduous dentition comprises fewer teeth than the
3、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. D-First molar.,B,C,D,E,A,E-Second molar.,The shorthand formula for the deciduous teeth is as follo
4、ws: I 2 C 1 M2 =10,2,1,2,GENERAL CHARACTERISTICS,The deciduous teeth generally have several important differences in morphology, composition, size colour as listed below: 1-The deciduous teeth are smaller than the permanent teeth.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH,PRINCIPAL
5、 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. 3-The enamel of the deciduous teeth is more permeable and more easily worn down. The degree of permeability is le
6、ssened after the start of root resorption.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS 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.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS TEETH AND PERMANENT TEETH,5- Deciduous te
7、eth 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.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT
8、TEETH,6-In newly erupted deciduous teeth, the cusps tend to be more pointed.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH,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 PE
9、RMANENT TEETH,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.,PRINCIP
10、AL 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.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH,10-The root ca
11、nal of deciduous teeth are very fine.,PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH,11-Usually there are no depressions or perikymata on the labial surface of the crown of the incisors. These surfaces are smooth.,ON THE ANTERIOR TEETH,ON THE ANTERIOR TEETH,12-There are no mamelones on
12、the incisal edges.,13-The cervical ridge on the facial surfaces is prominent.,ON THE ANTERIOR TEETH,15-The root is narrow mesiodistally.,ON THE ANTERIOR TEETH,14-The cingulae are prominent or seem to bulge and occupy about one third of the cervicoincisal length lingually,ON THE POSTERIOR TEETH,16- T
13、he 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,18-The molar crowns are wide mesiodistally,
14、yet very short cervico- occlusally. 19-The buccal cusps of molars are not pointed or sharp, with cusp slopes meeting at a very wide obtuse angle.,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
15、distinguish rights from left ).,ON THE POSTERIOR TEETH,22- The second molars are larger than the first molars. 23-The root furcation is near the crown, and there is little if any root trunk.,ON THE POSTERIOR TEETH,ON THE POSTERIOR TEETH,24-The roots are widely spread beyond the confines of the crown
16、 to allow for the developing permanent successors.,ON THE POSTERIOR TEETH,ON THE POSTERIOR TEETH,ON THE POSTERIOR TEETH,25-Roots are thin or slender.,ON THE POSTERIOR TEETH,ON THE POSTERIOR TEETH,26-The second molar roots are spread more widely than the first deciduous molar ( opposite of the perman
17、ent molars).,E,D,6,7,IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETH,Maintenance of a normal appearance. Formulation Efficient mastication of food. of clear speech. Maintenance of a proper diet. Missing or badly decayed teeth may be one reason that young children reject foods that are difficult to chew
18、.,IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETH,5-Avoidance of infection and concomitant pain .An abscess from a deciduous tooth can cause dark spots (Turners spots) on the permanent tooth developing beneath it. 6-Maintenance of space and arch continuity for the emergence of permanent teeth.,Chronolo
19、gy: Initial calcification 3-4 months in utero Completion of crown 4 months Eruption 7 months Completion of root 1 years,MAXILLARY FIRST(CENTRAL) DECIDUOUS INCISOR,MAXILLARY FIRST(CENTRAL) DECIDUOUS INCISOR,PRINCIPAL IDENTIFYING FEATURES: 1- Rounded disto-incisal angle: sharp mesio-incisal angle. 2-S
20、imilar to maxillary first permanent incisor but smaller and chubbier overall. 3-Large lingual cingulum and pronounced bulge on labial surface.,MAXILLARY FIRST(CENTRAL) DECIDUOUS INCISOR,M,D,M,D,PRINCIPAL IDENTIFYING FEATURES: 4-Root tilts distally and labially from long axis of crown. 5-One root can
21、al; two pulp horns, one mesial, one distal. Mesial horn slightly larger. VARIATIONS No noticeable variations.,MAXILLARY FIRST(CENTRAL) DECIDUOUS INCISOR,MAXILLARY SECOND (LATERAL) DECIDUOUS INCISOR,Chronology: Initial calcification 4 months in utero Completion of crown 5months Eruption 8-9months Com
22、pletion of root 1 -2 years,MAXILLARY SECOND (LATERAL) DECIDUOUS INCISOR,MAXILLARY SECOND (LATERAL) DECIDUOUS INCISOR,Chronology: Initial calcification 4 months in utero Completion of crown 5months Eruption 8-9months Completion of root 1 -2 years,Chronology: Initial calcification 4 months in utero Co
23、mpletion of crown 5months Eruption 8-9months Completion of root 1 -2 years,MAXILLARY SECOND (LATERAL) DECIDUOUS INCISOR,PRINCIPAL IDENTIFYING FEATURES: 1-Similar shape to maxillary deciduous central incisor but crown is smaller and narrower in proportion. 2-Lingual cingulum less pronounced.,MAXILLAR
24、Y SECOND (LATERAL) DECIDUOUS INCISOR,3-Rounded disto-incisal angle ;sharp mesio-incisal angle. 4-One root canal; two pulp horns, one mesial ,one distal. Mesial horn slightly larger. VARIATIONS Rare, in contrast to the highly variable maxillary permanent,PRINCIPAL IDENTIFYING FEATURES:,MANDIBULAR FIR
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