1、THE DECIDUOUS DENTITIONINTRODUCTIONThe 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 exfoliate
2、d to be replaced 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 teet
3、h 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.D-First molar.BCDEA E-Second molar.The shorthand formula for the deciduous teeth is as follows:I 2
4、 C 1 M2 =10212GENERAL CHARACTERISTICSThe 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 TEETHPRINCIPAL DIFFERENCES BETW
5、EEN DECIDUOUS AND PERMANENT TEETH2-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 lessened after the star
6、t of root resorption.PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH4-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 TEETH5-Deciduous teeth have a pronounced cervi
7、cal 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 TEETH6-In newly erupted deciduous
8、 teeth,the cusps tend to be more pointed.PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH7-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 TEETH8-The roots of anterior de
9、ciduous 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.PRINCIPAL DIFFERENCES BETWEEN DECIDUOUS AND PERMANE
10、NT TEETH9-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 TEETH10-The root canal of deciduous teeth are very fine.PRINCIPAL DI
11、FFERENCES BETWEEN DECIDUOUS AND PERMANENT TEETH11-Usually there are no depressions or perikymata on the labial surface of the crown of the incisors.These surfaces are smooth.ON THE ANTERIOR TEETHON THE ANTERIOR TEETH12-There are no mamelones on the incisal edges.13-The cervical ridge on the facial s
12、urfaces is prominent.ON THE ANTERIOR TEETH 15-The root is narrow mesiodistally.ON THE ANTERIOR TEETH14-The cingulae are prominent or seem to bulge and occupy about one third of the cervicoincisal length linguallyON THE POSTERIOR TEETH16-The molar crown have a narrow chewing (occlusal table)buccoling
13、ually.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 TEETH18-The molar crowns are wide mesiodistally,yet very short cervico-occlusally.19-The buccal cusps of molars are not
14、 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 TEETH21-The cervical ridge is prominent mesially(it is easy to distinguish rights from left).ON THE POSTERIOR TEETH22-The second molars are la
15、rger than the first molars.23-The root furcation is near the crown,and there is little if any root trunk.ON THE POSTERIOR TEETHON THE POSTERIOR TEETH24-The roots are widely spread beyond the confines of the crown to allow for the developing permanent successors.ON THE POSTERIOR TEETHON THE POSTERIOR
16、 TEETHON THE POSTERIOR TEETH25-Roots are thin or slender.ON THE POSTERIOR TEETHON THE POSTERIOR TEETH26-The second molar roots are spread more widely than the first deciduous molar(opposite of the permanent molars).ED 67IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETHMaintenance of a normal appearance.F
17、ormulation 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.IMPORTANT FUNCTIONS OF SOUND DECIDUOUS TEETH5-Avoidance of infection and concomitant pain.An abscess from
18、 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.Chronology:Initial calcification 3-4 months in uteroCompletion of crown 4 months Eruption 7 monthsCompletion of root 1 ye
19、arsMAXILLARY FIRST(CENTRAL)DECIDUOUS INCISORMAXILLARY FIRST(CENTRAL)DECIDUOUS INCISORPRINCIPAL IDENTIFYING FEATURES:1-Rounded disto-incisal angle:sharp mesio-incisal angle.2-Similar to maxillary first permanent incisor but smaller and chubbier overall.3-Large lingual cingulum and pronounced bulge on
20、 labial surface.MAXILLARY FIRST(CENTRAL)DECIDUOUS INCISORMD MDPRINCIPAL IDENTIFYING FEATURES:4-Root tilts distally and labially from long axis of crown.5-One root canal;two pulp horns,one mesial,one distal.Mesial horn slightly larger.VARIATIONSNo noticeable variations.MAXILLARY FIRST(CENTRAL)DECIDUO
21、US INCISORMAXILLARY SECOND(LATERAL)DECIDUOUS INCISORChronology:Initial calcification 4 months in uteroCompletion of crown 5months Eruption 8-9monthsCompletion of root 1-2 yearsMAXILLARY SECOND(LATERAL)DECIDUOUS INCISORMAXILLARY SECOND(LATERAL)DECIDUOUS INCISORChronology:Initial calcification 4 month
22、s in uteroCompletion of crown 5months Eruption 8-9monthsCompletion of root 1-2 yearsChronology:Initial calcification 4 months in uteroCompletion of crown 5months Eruption 8-9monthsCompletion of root 1-2 yearsMAXILLARY SECOND(LATERAL)DECIDUOUS INCISORPRINCIPAL IDENTIFYING FEATURES:1-Similar shape to
23、maxillary deciduous central incisor but crown is smaller and narrower in proportion.2-Lingual cingulum less pronounced.MAXILLARY SECOND(LATERAL)DECIDUOUS INCISOR3-Rounded disto-incisal angle;sharp mesio-incisal angle.4-One root canal;two pulp horns,one mesial,one distal.Mesial horn slightly larger.V
24、ARIATIONS Rare,in contrast to the highly variable maxillary permanentPRINCIPAL IDENTIFYING FEATURES:MANDIBULAR FIRST(CENTRAL)DECIDUOUS INCISORChronology:Initial calcification 4 months in uteroCompletion of crown 4 months Eruption 61/2 monthsCompletion of root 1-2 yearsPRINCIPAL IDENTIFYING FEATURES:
25、1-Single tapered root more rounded than that of lower mandibular permanent incisor,tends to incline distally.2-Smalles tooth in the deciduous dentition.3-Sometimes a logitudinal groove on the distal surface of root.4-cervical margin most sinuous on mesial side.MANDIBULAR FIRST(CENTRAL)DECIDUOUS INCI
26、SORMANDIBULAR FIRST(CENTRAL)DECIDUOUS INCISORPRINCIPAL IDENTIFYING FEATURES:5-Large,convex cingulum and pronounced bulge on labial surface.6-One root canal;two pulp horns,one mesial,one distal.VARIATIONS:The pronounced cervical bulge on the labial surface may be reduced or completely absent.MANDIBUL
27、AR SECOND(LATERAL)DECIDUOUS INCISORMANDIBULAR SECOND(LATERAL)DECIDUOUS INCISORChronology:Initial calcification 4 months in uteroCompletion of crown 41/2months Eruption 7 monthsCompletion of root 1-2 yearsChronology:Initial calcification 4 months in uteroCompletion of crownEruptionPRINCIPAL IDENTIFYI
28、NG FEATURES:1-Single tapered root with round cross-section,tend to incline distally.2-Rounded disto-incisal angle;sharp mesio-incisal angle.MANDIBULAR SECOND(LATERAL)DECIDUOUS INCISORMANDIBULAR SECOND(LATERAL)DECIDUOUS INCISOR3-Incisive edge slopes downwards from mesial to slightly lower distal surf
29、ace.4-Crown may,in some cases,show twisting on root for incisive edge to follow mandibular arch.PRINCIPAL IDENTIFYING FEATURES:MANDIBULAR SECOND(LATERAL)DECIDUOUS INCISORPRINCIPAL IDENTIFYING FEATURES:5-Larger than lower first(central)deciduous incisor.6-Lingual surface may be more concave than that
30、 of the madibular central deciduous incisor.7-Single root;two pulp horns,one mesial,one distal.VARIATIONSNo noticeable variations.A feature of the deciduousdentition is its consistency in its morphology.MAXILLARY DECIDUOUS CANINEChronology:Initial calcification5 months in uteroCompletion of crown 9m
31、onthsEruption 16-20 monthsCompletion of root 3years MAXILLARY DECIDUOUS CANINEPRINCIPAL IDENTIFYING1-Mesial slope of cusp longer than distal slope.2-Conical crown with pronounced cervical bulge and pointed cusp.MAXILLARY DECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMAXILLARY D
32、ECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMAXILLARY DECIDUOUS CANINEMDFEATURES:DMMAXILLARY DECIDUOUS CANINEPRINCIPAL IDENTIFYING FEATURES 3-Labial and lingual logitudinal ridges extending from cusp tips:4-Crown more bulbous than that of maxillary pe
33、rmanent canine.MAXILLARY DECIDUOUS CANINEPRINCIPAL IDENTIFYING FEATURES:5-Diamond-shape outline rounded corners from incisal aspect.6-Cervical margin rises further incisally on the mesial than on the distal surface.DMPRINCIPAL IDENTIFYIN7-Single root often more than twice the length of the crown.Sle
34、nder taper with similar cross-section to that of the maxillary permanent canine;distally inclined.8-Single root canal;pulp chamber elongated and directed towards cusp.VARIATIONSA symmetrical and symmetrical crown forms are equally common.Otherwise no noticeable variations.MAXILLARY DECIDUOUS CANINE
35、FEATURES:MANDIBULAR DECIDUOUS CANINEMANDIBULAR DECIDUOUS CANINEChronology:Initial calcification 5months in uteroCompletion of crown 9 months Eruption 16-20 monthsCompletion of root 2-3 yearsPRINCIPAL IDENTIFYING FEATURS:1-Smaller and slimmer overall than the maxillary deciduousCanine.2-Less well-def
36、ined labial and lingual longitudenally ridges;lingual ridge often completely absent.3-Concave lingual surface.4-Distal slope longer than mesial.5-Cervical margin more sinuous on mesial side.6-Single tapering root inclines distally and slightly labially.7-Single root canal;pulp chamber elongated and
37、directed towards cusp.VARIATIONS:No noticeable variations.Lingual logitudenal ridge occasionally present on lingual surface.MANDIBULAR DECIDUOUS CANINEPRINCIPAL IDENTIFYING FEATURS:1-Smaller and slimmer overall than the maxillary deciduousCanine.2-Less well-defined labial and lingual longitudenally
38、ridges;lingual ridge often completely absent.3-Concave lingual surface.4-Distal slope longer than mesial.5-Cervical margin more sinuous on mesial side.6-Single tapering root inclines distally and slightly labially.7-Single root canal;pulp chamber elongated and directed towards cusp.VARIATIONS:No not
39、iceable variations.Lingual logitudenal ridge occasionally present on lingual surface.MAXILLARY FIRST DECIDUOUS MOLARChronology:Initial calcification 5months in uteroCompletion of crown6 months Eruption 12-16monthsCompletion of root 2-2 years PRINCIPAL IDENTIFYING FEATURES:1-Pronounced bulge on mesia
40、l side of buccal surface:molar tubercle of Zuckerkandl.2-Trapezoid coronal outline with narrow occlusal surface running mesiodistally.MAXILLARY FIRST DECIDUOUS MOLARMAXILLARY FIRST DECIDUOUS MOLARMAXILLARY FIRST DECIDUOUS MOLAR PRINCIPAL IDENTIFYING FEATURES:3-Lingual surface shorter,mesiodistally,t
41、han the buccal.4-Mesiolingual cusp largest and pointed.5-Widest labiolingual crown measurement at mesial end.MAXILLARY FIRST DECIDUOUS MOLAR PRINCIPAL IDENTIFYING FEATURES:6-Three root canals;four pulp horns:mesiobuccal,distolingual,distobuccal and mesiolingual.VARIATIONS:Palatal and distobuccl root
42、s sometimes fuse.Mesiobuccal cusp sometimes has an accessory cusp mesial to it.Distolingual cusp sometimes absent.Zuckerkandl,tubercle is occasionally scarcely discernible.MAXILLARY FIRST DECIDUOUS MOLARMAXILLARY SECOND DECIDUOUS MOLARChronology:Initial calcification 6 months in utero Completion of
43、crown 10-12 months Eruption 1-2 yearsCompletion of root 3 years PRINCIPAL IDENTIFYING FEATURES:1-Morphology of maxillary first permanent molar duplicated on a smaller scale.2-More prominent bulge on cervical part of buccal surface.MAXILLARY SECOND DECIDUOUS MOLARDDL LMM B BPRINCIPAL IDENTIFYING FEAT
44、URES:3-Roots have wider divergence than those of maxillary first permanent molar.4-Cusp of Carabelli present in most cases.MAXILLARY SECOND DECIDUOUS MOLARMAXILLARY SECOND DECIDUOUS MOLARPRINCIPAL IDENTIFYING FEATURES:5-Three root canals;three pulp horns:mesiolingual,distobuccal and distolingual.VAR
45、IATIONS:Cusp of Carabelli may be absent.Very rarely the distolingual cusp may be so reduced as to be scarcely discernible.The palatal and distobuccal roots may sometimes be fused.MANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARChronology:Initial calcif
46、ication 5months in uteroCompletion of crown 6months Eruption 12-16monthsCompletion of root 2-2 yearsPRINCIPAL IDENTIFYING FEATURES:1-Molar tubercle of Zuckerkandl:an exaggerated cervical bulge on the buccal surface of the crown over the mesial root,with a considerable cervical constriction.2-Four cu
47、sps:buccal cusps compressed labiolingually with no clear separation between them in contrast to the two lingual cusps which are clearly defined and roughly conical in shape.3-Mesiolingual cusp largest.MANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMAN
48、DIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLAR LBD MPRINCIPAL IDENTIFYING FEATURES:4-Tooth longer mesiodistally than labiolingually.5-Mesial marginal ridge more pronounced than distal.6-Two roots flattened mesiodistally.Mesial is the longer and from the mesial aspect appears rectangul
49、ar.7-Two root canals;three pulp horns;mesiobuccal,lingual,distobuccal.VARIATIONS:Mesiolingual cusp sometimes very insignificant.Buccolingual crest occasionally absent.MANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMANDIBULAR FIRST DECIDUOUS MOLARMANDI
50、BULAR FIRST DECIDUOUS MOLARMANDIBULAR SECOND DECIDUOUS MOLARChronology:Initial calcification 6months in uteroCompletion of crown 10-12months Eruption 1 -2 years Completion of root 3yearsPRINCPAL IDENTIFYING FEATURES:1-Same number of cusps and roots;similar arrangement to the mandibular first permane
