Dr. M. Lohith, MDS Sr. Lecturer

1. CEMENTUM
Presented by
Dr. M. Lohith
MDS Sr. Lecturer

2. Cementum is the calcified avascular
mesenchymal tissue that forms the outer
covering of the anatomic root

3. TWO TYPES
ACELLULAR CELLULAR
Primary secondary
Both consists of -- calcified interfibrillar matrix
-- collagen fibrils

4. TWO SOURCES OF COLLAGEN FIBERS
1. SHARPEY’S FIBERS --principal fibers of the
PDL formed by fibroblasts
2. FIBERS -- of cementum matrix and are
produced by cementoblasts

5. The portions of the principal fibers of the PDL which are
embedded in the root cementum [arrows] and in the
Alveolar bone proper [ABP] are called Sharpey’s fibers
The arrows to the right indicate the border between ABP
and the Alveolar bone [AB]

6. ACELLULAR CEMENTUM
Acellular cementum -- first to be formed
Covers the cervical third of root
Does not contain cells
Formed before the tooth reaches the
occlusal plane
Thickness ranges from 30 -230 nano microns
Sharpey’s fibers comprise of the structure
of acellular cementum

7. Acellular cementum[AC] showing incremental lines running
parallel to the long axis of the tooth – they represent the
Appositional growth of cementum
Thin lines running perpendicular to the surface are the
sharpey’s fibers of PDL

8. A B
A. A thin layer of acellular,extrinsic fiber cementum[AEFC]
with densely packed extrinsic fibers covers the peripheral
dentin
Cementoblasts and fibroblasts can be seen adjacent to the
cementum
B. SEM OF AEFC -- The extrinsic fibers attach to dentin[ left ]
and are continuous with the collagen fiber bundles[CB] of the
Periodontal ligament

9. CELLULAR CEMENTUM
Cellular cementum formed after the
tooth reaches the occlusal plane
Contains cells – cementocytes in individual
spaces [lacunae] that communicate with
each other through anastomosing canaliculi
Cellular cementum is less calcified than
the acellular type
Sharpey’s fibers occupy a smaller portion
of cellular cementum

10. A B
A. Cellular ,mixed stratified cementum[CMSC] contains cells
and intrinsic fibers
B. Cementocytes [black cells] reside in lacunae in CMSC
They communicate with each other through a network of
Cytoplasmic processes [arrows] running in canaliculi in the
Cementum

11. PDL which resides between the cementum[CMSC] is densely
packed with collagen fibers oriented parallel to root surface
[intrinsic fibers] and sharpey’s fibers[extrinsic fibers] oriented
more or less perpendicularly to cementum-dentine junction
[predentin [PD]]

12. PERMEABILITY
Cellular and Acellular cementum are very
permeable and permit diffusion of dyes
from the pulp to external root surface

13. CEMENTO - ENAMEL JUNCTION
THREE TYPES
Fail to meet Butt joint Cementum
overlaps Enamel

14. THICKNESS
Most rapid in the apical regions
Coronal half of the root varies from
16-60 nanomicrons or about thickness of a hair
Greatest thickness [150 to 200 nanomicrons]
in apical third and in furcations areas
Thicker - distal surfaces than mesial surfaces
Average thickness of 95 nanomicrons at
20yrs and 215 nanomicrons at age 60yrs

15. The cementum does not exhibit alternating periods of
resorption and apposition, but increases in thickness
throughout life by deposition of successive new layers
Cementoblast [CB] located near the surface of the
cementum[C] and between 2 inserting principal fiber bundles

16. HYPERCEMENTOSIS [cementum hyperplasia]
Hypercementosis occurs as a generalized
thickening of the cementum with nodular
enlargement of the apical third of the root
ETIOLOGY
Excessive tension from ortho.appliances or
occlusal forces
Hypercementosis of the entire dentition
occurs in patients with paget’s disease

17. RESORPTION AND REPAIR
Causes
LOCAL SYSTEMIC

18. LOCAL
Pressure from mal aligned erupting teeth
Teeth without functional antagonists
Replanted and transplanted teeth
Orthodontic tooth movement
Trauma from occlusion
Periodontal disease
Embedded teeth
Tumors
Cysts

19. SYSTEMIC
Hypothyroidism
Hereditary fibrous osteodystrophy
Paget’s disease

20. Cementum resorption is not necessarily
continuous and may alternate with periods
of repair and deposition of new cementum
Newly formed cementum is demarcated
from the root by deeply staining irregular
line termed as “reversal line”

21. Repair of previously resorbed root
The defect is filled with cellular cementum[C] which is
Separated from the older cementum[R] by an irregular line [L]
that Indicates the preexisting outline of the resorbed root
P. Periodontal ligament

22. Apex of left central incisor shortened by resorption of
cementum and dentin
Cementicle at upper right

23. Scanning electron micrograph of root exposed by
periodontal disease showing large resorption bay

24. Multinucleated osteoclast is seen at X

25. ANKYLOSIS
Fusion of cementum and alveolar bone
with obliteration of periodontal ligament
Causes :
Chronic periapical inflammation
Tooth replantation
Occlusal trauma

26. ALVEOLAR PROCESS
The portion of the maxilla and mandible
that forms and supports the tooth sockets

27. CELLS AND INTERCELLULAR MATRIX
Osteoblasts produce organic matrix of bone
Bone consists :
2/3 inorganic matter & 1/3 organic matrix

28. Bone at this site contains osteons[white circles] each of
which harbors a blood vessel located in a haversian canal
The blood vessel is surrounded by concentric,mineralized
lamellae to the osteon
The osteons in the lamellar bone are not only structural
units but also metabolic units
Thus the nutrition of the bone is secured by the blood
vessels in the haversian canals and connecting vessels in
the volkmann canals

29. Border line between the ABP and lamellar bone with an
osteon – Note the presence of haversian canal [HC]
Three active oteons [brown] with a blood vessel [red] in
the Haversian [HC]
Interstitial lamella [green] is located between the
osteons[o] Represents old and partly remodelled osteon
The ABP is presented by dark lines into the sharpey’s
fibers [SF] insert

30. Osteon with osteocytes [OC] residing in osteocyte
lacunae in the lamellar bone
The osteocytes connect via canaliculli [CAN] which
contain cytoplasmic projections of the osteocytes
Haversian canal [HC] is seen in the middle of osteon

31. Osteocytes present in the mineralized bone, communicate
with osteoblasts on the bone surface through canaliculi

32. Osteocytes [OC] and their long and delicate cytoplasmic
Processes communicate through the canaliculi[CAN]
In the Bone
The resulting canaliculi – lacunar system is essential for
cell Metabolism by allowing diffusion of nutrients and
waste products

33. Inorganic matter is minerals
Calcium
Phosphate
Hydroxyl corbonate
Citrate
traces of sodium, magnesium and fluorine
The mineral salts are in the form of
Hydroxyapatite crystals

34. Organic matrix
90% of collagen type I
with small amounts of noncollagenous
proteins such as -
Osteocalcin
Osteonectin
Bone morphogenetic protein
Phosphoproteins
Proteoglycans

35. SOCKET WALL
Bundle bone is the term given to bone
adjacent to the periodontal ligament that
contains a great number of sharpey’s fibers
characterized by thin lamellae arranged in
layers parallel to the root with intervening
appositional lines

36. BONE MARROW
In the embryo and new born the cavities of
all bones are occupied by red hemopoitic
marrow
The red marrow gradually undergoes a
physiological change to fatty or yellow
inactive type of marrow

37. PERIOSTEUM AND ENDOSTEUM
The tissue covering the outer surface of
bone is termed periosteum and the tissue
lining the internal bone cavities is called
endosteum

38. Periosteum consists
Inner layer and Outer layer
Inner layer composed of osteoblasts
surrounded by osteo-progenitor cells which
have the potential to differentiate into
osteoblasts
Outer layer rich in blood vessels and nerves
and composed of collagen fibers and
fibroblasts

39. Endosteum composed of a single layer of
osteoblasts and sometimes connective tissue

40. All active bone forming sites harbor osteoblasts
The outer surface of the bone is lined by a layer of
such Osteoblasts which, in turn, are organized in a
periosteum[P] that contains densely packed collagen fibers
On the “inner surface” of the bone I,e. in the bone marrow
space, there is a endosteum[E] which presents similar
features as the periosteum

41. INTERDENTAL SEPTUM
The interdental septum consists of
cancellous bone bordered by socket wall
cribriform plates
The distance between the crest of Al.bone
and cemento-enamel junction in young
adults varies between 0.75 and 1.49mm
[average 1.08mm] this distance increases
with age to an average of 2.81mm

42. OSSEOUS TOPOGRAPHY
Bone contour normally confirms to the
prominence of the roots
The height and thickness of the facial and
lingual bony plates are affected by the
- alignment of the teeth
- angulation of the root to the bone and
- occlusal forces

43. On teeth in labial version the margin of
the labial bone is located farther apically
On teeth in the lingual version the facial
bony plate is thicker than normal

44. FENESTRATIONS AND DEHISCENCES
Isolated areas in which the root is denuded
of bone and the root surface is covered by
periosteum and gingiva are termed
fenestrations - marginal bone is intact here
When the denuded areas extend through
the marginal bone the defect is dehiscence

45. Occur in 20% of the teeth
More in the facial teeth than the lingual
Common - anterior teeth than the posterior
Frequently bilateral

46. PHYSIOLOGICAL MIGRATION OF THE TEETH
With time and wear the proximal contact
areas of the teeth are flattened and the
teeth tend to move mesially
By age 40 it results in a reduction of
about 0.5cm in the length of a dental arch
from the midline to the third molars

47. VASCULARIZATION
BLOOD SUPPLY
Inferior and superior alveolar arteries to the
mandible and maxilla respectively and
reaches the periodontal ligament from
3 sources:
apical vessels
penetrating vessels from the alveolar bone
anastomosing vessels from the gingiva

48. VENOUS DRAINAGE
Accompanies the arterial supply
LYMPHATICS
Drain into the submaxillary lymph nodes