The document compares and contrasts primary and permanent teeth. Some key differences include: - Primary teeth are smaller with shorter crowns and thinner enamel and dentin layers. - Permanent teeth have larger crowns and thicker enamel and dentin. - The first permanent molar is an important tooth that erupts around 6 years of age and bears significant occlusal forces. - It plays a key role in arch development and tooth movement, so preserving it is important to prevent problems with spacing, function, and occlusion.

1. Differences between Primary and
Permanent Teeth and Importance of
First permanent molar
KARISHMA.S
II MDS

2. The human dentition is termed heterodont
• In comparison, a homodont dentition is one in which all of the teeth
are the same in form and type. This sort of dentition is found in some
of the lower vertebrates.
• Sets of teeth: Diphyodont (Human):
• 2 sets of teeth – 1. Decidous
2. Permanent.
INTRODUCTION

3.  Deciduous dentition - Eruption : about six months to two years of age
No. of teeth presents : 20
Other non-scientific name : "milk" teeth/" baby" teeth/ "temporary"
teeth.
• 2. Permanent dentition – Eruption: from 6-21 years of age.
No. of teeth presents: 32

4.  Eruption sequence follows a pattern – Incisors-First Molars-
Canines-Second molars.
 This pattern is generally followed by both arches, with the
mandibular arch preceding the maxillary arch.
 The loss of deciduous teeth tends to mirror the eruption
sequence.
 Caries susceptibility is reverse of this order

5. Three periods of dentition, since the deciduous and permanent dentitions
overlap in time.
These periods are summarized in the following manner:
1. Primary dentition period
2. Mixed dentition period
3. Permanent dentition Period

6. Morphological & Anatomical Difference b/w
Primary & Permanent Tooth
Primary Teeth
Crown:
- Shorter.
- Narrow Occlusal
table.
- Constricted in
cervical portion.
Permanent Teeth
Crown:
- Bigger
- Broad Occlusal table.
- Cervical constriction is
not well marked.

7. 1) Bluish white in color ,refractive
index similar to that of milk(
RI=1).
2) Cuspids are slender and to be
more conical.
3) Cervical ridges are more
pronounced especially on buccal
aspect of first primary molar
4) Occlusal plane is relatively flat.
5) Molars are bulbous and are
sharply constricted cervically
6) 1 st molar is smaller in
dimension than the 2nd molar
1) Grayish white to yellowish white
in color.
2) Cuspids are less conical.
3) The cervical ridges are flatter
4) Occlusal plane has relatively
curved contour.
5) They have less constriction at the
neck.
6) 1 st molar is larger in dimension
than the 2nd molar.

8. • Thinner enamel and dentin
layers.
• Enamel rods in the cervical
area directed Occlusally.
• Broad and flat contacts.
• Color is usually lighter.
• Prominent mesio-buccal
cervical bulge seen in
primary molars.
• Incisors have no
developmental grooves or
mammelons.

9.  Pulp chamber is larger in relation to crown
size.(smaller)
 Pulpal outline follows DEJ more closely.
( less closely)
 Pulp horns are closer to the outer surface.
Mesial pulp horn extends to a closer
approximation of surface than the distal
pulp horn.(comparatively away)
 High degree of cellularity and vascularity
in tissue.
 High potential for repair.
PULP

10.  Comparatively less tooth structure.
 Root canals are more ribbon like. the
radicular pulp follows a thin , tortuous
and branching path (well defined with
less branching. )
 Floor of pulp chamber is porous.
Accessory canals in primary pulp
chamber floor leads directly into
interradicular furcation.

11. PRIMARY TEETH PERMANENT TEETH
• Roots are larger and more slender in
comparison to crown size.
• Furcation is more towards cervical area
so that root trunk is smaller .
• Roots are narrower mesio-distally.
• At the cervical region, the roots of the
primary molars flare outward and
continue to flare as they approach the
apices to accommodate permanent tooth
buds.
• Undergo physiologic resorption during
shedding of primary teeth.
• Roots are shorter and bulbous
in comparison to crown.
• Placement of furcation is apical
, thus the root trunk is larger.
• Roots are broader
mesiodistally.
• Marked flaring of roots is
absent.
• Physiologic resorption is
absent.
ROOTS

12. ENAMEL
PRIMARY TEETH PERMANENT TEETH
• Bands of retzius are less common. This
maybe partly responsible for the
bluish white color.
• Neonatal lines are present in all teeth.
• Enamel is thinner and has a more
consistent depth of about 1mm
thickness throughout the entire crown
• Enamel rods at the cervical slopes
occlusally from the DEJ.
• Bands of retzius are more
common.
• Neonatal lines are only
present in 1st molars
• The enamel is thicker
and has a thickness of
about 2-3mm.
• Enamel rods are oriented
gingivally.

14. DENTIN
 Dentinal tubules are less
regular.
 Dentin thickness is half that of
permanent teeth. Thickness is
limited in some places.
 Less dense and easy to cut.
 Interglobular dentin is absent.
 Dentinal tubules are
more regular.
 Dentin is thicker.
 Dentin is denser and
difficult to cut.
 Interglobular dentin is
present.

15. PERIODONTIUM
• Cementum is very thin and of the
primary type. Secondary cementum is
characteristically absent.
• Alveolar atrophy is rare.
• Gingivitis is generally absent in a
healthy child. Similarly recession is in
frequent.
• Secondary cementum is
present.
• Alveolar atrophy occurs.
• Gingivitis is common in
adults.

16. HISTOLOGICAL DIFFERENCES
• Roots have enlarged apical
foramens. Thus , the abundant
blood supply demonstrates a more
typical inflammatory response.
• Incidence of reparative dentin
formation beneath carious lesion is
more extensive and irregular.
• Foramens are restricted. Thus
reduced blood supply favors a
calcific response and healing
by calcific scarring.
• Reparative dentin formation
is less.

17. OTHER KEY POINTS
• Primary Teeth - More prone to
acid attack, thus rapidly
demineralised to dental caries.
• Dentin is less mineralised .
• Lamina dura is relatively thick.
• Premolars –Absent
• Mesiodistal diameter of crown is
more then cervico incisal length.
• Permanent Teeth- Less prone to
caries attack.
• Dentin is more mineralised.
• Lamina dura is relatively thin.
• Premolars-Present
• Cervico incisal length is more
then the mesiodistal dimension.

19. The Importance Of The First Permanent
Molar
The first permanent molar is a very important tooth from both
functional and developmental point of view.It is otherwise known
as "six year molar"
This tooth erupts between 5 and 1/2 to 6 and 1/2 years of age.It is
the first non-succedaneous tooth to erupt in to the oral cavity.As it
has a large occlusal table,it bears the maximum load of occlusal
forces.

20.  It is considered a key to occlusion.As this tooth erupts posterior to
the deciduous second molar(milk tooth),it is also instrumental in
establishing the arch perimeter.
 The first permanent molar also has maximum root surface and so is
the most important anchorage unit used in tooth movement

21.  Due to the presence of deep pits and fissures, food lodgement is
common in this tooth resulting in rapid decay.
 Extraction or removal of this tooth leads to problems in space
management, tooth movement, mastication and occlusion.
 So every attempt should be made to save this tooth in case it
gets decayed.

22. YOUNG PERMANENT TEETH
1)Vital pulp therapy for teeth diagnosed with a normal pulp or reversible pulpitis
Protective liner/Indirect pulp treatment
Apexogenesis (root formation). Formation of the apex in vital, young,
permanent teeth can be accomplished by im-plementing the appropriate vital pulp
therapy (i.e., indirect pulp treatment, direct pulp capping, partial pulpotomy for
carious exposures and traumatic exposures).
Direct pulp cap : When a small exposure of the pulp is encountered during cavity
preparation and after hemorrhage control is obtained, the exposed pulp is capped
with a material such as calcium hydroxide88-92 or MTA92 prior to placing a
restoration that seals the tooth from microleakage

23.  Partial pulpotomy for carious exposures.
 Partial pulpotomy for traumatic exposures
(Cvek pulpotomy).
The partial pulpotomy for traumatic exposures is a
procedure in which the inflamed pulp tissue beneath an
exposure is re-moved to a depth of one to three
millimeters or more to reach the deeper healthy tissue.
Pulpal bleeding is controlled using bacteriocidal irrigants
such as sodium hypochlorite or chlorhexidine, and the site
then is covered with calcium hydroxide or MTA

24. 2)Nonvital pulp treatment
 Pulpectomy (conventional root canal treatment).
 Apexification (root end closure).