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College of DentistryCollege of Dentistry
Human Dentition IIHuman Dentition II
Deciduous TeethDeciduous Teeth
Dr. Hazem Al AjramiDr. Hazem Al Ajrami

Deciduous teeth are that teeth which function
during childhood and then they are shed and
replaced by permanent teeth. 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.
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These teeth emerge in children between the ages
of 6 months and 2 years. Beginning at the age of
6 years, these teeth are gradually replaced by the
teeth of the permanent dentition. There are 20
teeth in the deciduous dentition: 10 maxillary
and 10 mandibular teeth.
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They are as follows, in order of position from the
midline:
Central incisor.
Lateral incisor.
Canine.
First molar.
Second molar.
There are no premolars. 66

Common nicknames for them are primaryCommon nicknames for them are primary
teeth, milk teeth, baby teeth, or temporaryteeth, milk teeth, baby teeth, or temporary
teeth, all of which, unfortunately, denote a tackteeth, all of which, unfortunately, denote a tack
of importance.of importance.
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The deciduous teeth are actually in the mouthThe deciduous teeth are actually in the mouth
functioning for from about 6 monthsfunctioning for from about 6 months
(mandibular central incisor) to 10 years(mandibular central incisor) to 10 years
(maxillary canine).(maxillary canine).
They play a very important role during theThey play a very important role during the
childhood in the proper alignment, spacing,childhood in the proper alignment, spacing,
and occlusion of the permanent dentition.and occlusion of the permanent dentition.
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When deciduous teeth are lose prematurely,When deciduous teeth are lose prematurely,
this can cause destructive results and should bethis can cause destructive results and should be
avoided.avoided.
When teeth of the permanent dentition replaceWhen teeth of the permanent dentition replace
deciduous teeth, the deciduous anterior teethdeciduous teeth, the deciduous anterior teeth
are replaces by the permanent anterior teethare replaces by the permanent anterior teeth
and the deciduous molars are replace by theand the deciduous molars are replace by the
premolars.premolars.
The permanent molars have no predecessors inThe permanent molars have no predecessors in
the deciduous dentition and come in posteriorthe deciduous dentition and come in posterior
to the deciduous molars.to the deciduous molars.
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Important functions of sound deciduous teeth:Important functions of sound deciduous teeth:
1.1. Efficient mastication of food.Efficient mastication of food.
2.2. Maintenance of a normal facial appearance.Maintenance of a normal facial appearance.
3.3. Formulation of clear speech.Formulation of clear speech.
4.4. Maintenance of a proper diet. Missing or badlyMaintenance of a proper diet. Missing or badly
decayed teeth may be one reason that youngdecayed teeth may be one reason that young
children reject foods that are difficult to chew.children reject foods that are difficult to chew.
5.5. Avoidance of infection and concomitant pain. AnAvoidance of infection and concomitant pain. An
abscess from a tooth developing beneath it.abscess from a tooth developing beneath it.
6.6. Maintenance of space and arch continuity for theMaintenance of space and arch continuity for the
emergence of permanent teeth.emergence of permanent teeth.
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Eruption time of deciduous dentition:Eruption time of deciduous dentition:
 The first deciduous teeth to erupt are usually theThe first deciduous teeth to erupt are usually the
mandibular central incisors, at about 6 months ofmandibular central incisors, at about 6 months of
age; the last tooth to emerge, thus completing theage; the last tooth to emerge, thus completing the
deciduous dentition, are the maxillary seconddeciduous dentition, are the maxillary second
molars, at about 24 months of age.molars, at about 24 months of age.
 The complete deciduous dentition is in the mouthThe complete deciduous dentition is in the mouth
from 2 years to 6 years of age, where nofrom 2 years to 6 years of age, where no
permanent teeth are present.permanent teeth are present. 1616

 Shortly after the fourth year of age, as the maxillaShortly after the fourth year of age, as the maxilla
and the mandible grow larger, spaces developand the mandible grow larger, spaces develop
between the deciduous teeth. This makes spacebetween the deciduous teeth. This makes space
for the permanent incisors and canines, which arefor the permanent incisors and canines, which are
considerably wider than their predecessors.considerably wider than their predecessors.
 The first permanent teeth to erupt are usually theThe first permanent teeth to erupt are usually the
mandibular first molars and then the maxillarymandibular first molars and then the maxillary
first molars. They appear distal to the secondfirst molars. They appear distal to the second
deciduous molars when a child is about 6 years ofdeciduous molars when a child is about 6 years of
age.age.
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 It is important to recognize that these areIt is important to recognize that these are
permanent teeth and to care for thempermanent teeth and to care for them
accordingly. They are commonly called 6-yearaccordingly. They are commonly called 6-year
molars. With their eruption, the mixedmolars. With their eruption, the mixed
dentition period begins. Permanent incisorsdentition period begins. Permanent incisors
begin to replace deciduous incisors at about 6begin to replace deciduous incisors at about 6
to 7 years of age (mandibular preceding theto 7 years of age (mandibular preceding the
maxillary).maxillary).
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 The last deciduous teeth to be lost are theThe last deciduous teeth to be lost are the
maxillary canines at 9 to 12 years of age. Nearlymaxillary canines at 9 to 12 years of age. Nearly
a year earlier, the deciduous second molars area year earlier, the deciduous second molars are
shed. They are replaced by the second premolarsshed. They are replaced by the second premolars
of the permanent dentition.of the permanent dentition.
 The mixed dentition (both deciduous andThe mixed dentition (both deciduous and
permanent teeth) is present from 6 years until 12permanent teeth) is present from 6 years until 12
years of age. Usually 24 teeth are present in theyears of age. Usually 24 teeth are present in the
mixed dentition (including the 6-year molars).mixed dentition (including the 6-year molars).
2020

Characteristics of deciduous teeth:Characteristics of deciduous teeth:
Generally:Generally:
Deciduous teeth are:Deciduous teeth are:
1.1. Smaller in size than the analogous permanentSmaller in size than the analogous permanent
teeth.teeth.
2.2. The enamel is whiter in color and more opaque,The enamel is whiter in color and more opaque,
which gives the crown a lighter color than thatwhich gives the crown a lighter color than that
of the permanent teeth.of the permanent teeth.
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3.3. The enamel of the deciduous teeth is lessThe enamel of the deciduous teeth is less
mineralized, more permeable and more easilymineralized, more permeable and more easily
worn down.worn down.
4.4. They have shorter crowns with respect toThey have shorter crowns with respect to
their roots.their roots.
5.5. The crowns have a marked constriction at theThe crowns have a marked constriction at the
cervix.cervix.
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6.6. The enamel seems to bulge close to the cervicalThe enamel seems to bulge close to the cervical
lines rather than gradually tapering.lines rather than gradually tapering.
7.7. The layers of enamel and dentin are thinner.The layers of enamel and dentin are thinner.
8.8. The pulp cavities are proportionally larger thanThe pulp cavities are proportionally larger than
on permanent teeth. The pulp horns are high.on permanent teeth. The pulp horns are high.
9.9. Deciduous teeth have more consistent shapesDeciduous teeth have more consistent shapes
than the permanent dentition (fewer anomalies).than the permanent dentition (fewer anomalies).
10.10. The crowns on deciduous teeth appear bulbous.The crowns on deciduous teeth appear bulbous.
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On the anterior teeth:On the anterior teeth:
11.11.Usually there are no depressions orUsually there are no depressions or
perikymata on the labial surface of the crownsperikymata on the labial surface of the crowns
of the incisors. These surfaces are smooth.of the incisors. These surfaces are smooth.
12.12.The cervical ridge on the facial surface isThe cervical ridge on the facial surface is
prominent.prominent.
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13.13. There are no mamelones on the incisal edges.There are no mamelones on the incisal edges.
14.14. The cingula are prominent or seem to bulge andThe cingula are prominent or seem to bulge and
occupy about one third of the cervico-incisaloccupy about one third of the cervico-incisal
length lingually.length lingually.
15.15. The root is narrow mesiodistally.The root is narrow mesiodistally.
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On the posterior teeth:On the posterior teeth:
16.16.The molar crowns have a narrow chewingThe molar crowns have a narrow chewing
surface (occlusal table) buccolingually.surface (occlusal table) buccolingually.
17.17.The molar occlusal surfaces are shallow. InThe molar occlusal surfaces are shallow. In
other words, the cusps are short, the ridges areother words, the cusps are short, the ridges are
not pronounced, and the grooves arenot pronounced, and the grooves are
correspondingly not as deep.correspondingly not as deep.
18.18.The molar crowns are wide mesiodistally, yetThe molar crowns are wide mesiodistally, yet
very short cervico-occlusally.very short cervico-occlusally. 2727

19.19. The buccal cusps on molars are not pointed orThe buccal cusps on molars are not pointed or
sharp, with their cusp slopes meeting at asharp, with their cusp slopes meeting at a
very wide obtuse angle.very wide obtuse angle.
20.20. There are few grooves or depressions in allThere are few grooves or depressions in all
surfaces of the crowns.surfaces of the crowns.
21.21. The cervical ridge is prominent mesially (it isThe cervical ridge is prominent mesially (it is
easy to distinguish rights from lefts).easy to distinguish rights from lefts).
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22.22. The second molars are larger than the firstThe second molars are larger than the first
molars.molars.
23.23. The root furcation is near the crown, and thereThe root furcation is near the crown, and there
is little if any root trunk.is little if any root trunk.
24.24. The roots are widely spread beyond theThe roots are widely spread beyond the
confines of the crown to allow for theconfines of the crown to allow for the
developing permanent successors.developing permanent successors.
25.25. Roots are thin or slender.Roots are thin or slender.
26.26. The second molar roots are spread moreThe second molar roots are spread more
widely than the first deciduous molar (oppositewidely than the first deciduous molar (opposite
of the permanent molars).of the permanent molars).
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H.d. ii-06 [1]

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H.d. ii-06 [1]