Histology and physiology of the pulp

Histology and physiology of the pulp

1. y of pulp

Histology and physiolog

prepared by:
d ulkareem/B-D- g Dr. Fatima B. sadia/ B.D.S
supervised by:
onservative Dentistry

M.SC- of C

Dr. Rand A. Ab

Dr. Hashim M. Hussein/

2. Introdu

e The dental pulp is soft tissue
of mesenchymal origin located in
center of a tooth. It consists of
specialized cells, odontoblasts,
arranged peripherally in direct
contact with dentin matrix.

This close relationship between
odontoblasts and dentin is known
as “pulp-dentin complex
surrounded by rigid walls and so Y 4
is unable to expand in response to Tooth Anatomy

injury.

blood vessels

3. we om tissue und rer in fhe ody

+ Pulp is surrounded by rigid walls and so is unable
to expand in response to injury as a part of the
inflammatory process. Therefore, pulpal tissue is
susceptible to change in pressure affecting the pain
threshold.

+ There is minimal collateral blood supply to pulp
tissue.

« The pulp is composed almost entirely of simple
connective tissue. At its periphery there is a layer of
highly specialized cells, the odontoblasts.
Secondary dentin is gradually deposited as a
physiological process which reduces the blood supply
and therefore, the resistance to infection or trauma.

4. ° The innervation of pulp tissue is both simple and
complex.

v Simple: in that there are only free nerve
endings and consequently the pulp lacks
proprioception.

v Complex: because of innervation of the
odontoblast processes which produces a high
level of sensitivity to thermal and chemical
change.

5. | Development of dental pul

° The pulp originates from ectomesenchymal
cells of dental papilla.

° Dental pulp is identified when these cells
mature and dentin is formed.

e Basically the development of tooth is
divided into bud, cap and bell stage.

6. cells of dental lamina proliferate and produce a bud like
projection into adjacent ectomesenchyme.

Oral ectoderm

Dental lamina
Enamel organ = : Central
Peripheral : £ polyhedral cells
columnar cells =a? VS
Condensation of

ectomesenchyme

Developing bone

7. ntal lamina
proliferate to form a concavity which produces cap
like appearance.

Oral ectoderm
Dental lamina
Outer enamel
epithelium
Dental follicle

Inner enamel
epithelium
Dental papilla

Stellate
reticulum

8. enamel epithelia are joined is called cervical loop. As the coils
of loop proliferate, enamel organ assumes bell stage.

» The differentiation of epithelial and mesenchymal cells into
ameloblasts and odontoblasts occur during bell stage.

Collapsed stellate
reticulum

Ameloblasts

Enamel

Dentin —£ 3 - Outer enamel

9. + The pulp is initially called as dental papilla; it is
designated as pulp only when dentin forms around it.

+ The differentiation of odontoblasts from undifferentiated
ectomesenchymal cells is accomplished by interaction of
cell and signaling molecules mediated through basal
lamina and extracellular matrix.

+ The dental papilla has high cell density and the rich
vascular supply as a result of proliferation of cells with
in it.

10. e cells of dental papilla appear as undifferentiated
mesenchymal cells, gradually these cells differentiate into
fibroblasts.

¢ The formation of dentin by odontoblasts heralds the
conversion of dental papilla into pulp. The boundary
between inner enamel epithelium and odontoblast form
the future DEJ.

+ The junction of inner and outer enamel epithelium at the
basal margin of enamel organ represent the future CEJ.

+ As the crown formation with enamel and dentin
deposition continues, growth and organization of
pulp vasculature occurs.

11. + At the same time as tooth develops unmyelinated
sensory nerves and autonomic nerves grow into
pulpal tissue.

+ Myelinated fibers develop and mature at a slower rate,
plexus of Raschkow does not develop until after tooth
has erupted.

12. + When pulp is examined histologically, it can be
distinguished into four distinct zones from periphery
to center of the pulp:

Odontoblastic process
Predentin

Odontoblast

Odontoblast nucleus
Cell free zone

Cell rich zone

Parietal layer

13. Dentin

Odontoblast process

Predentin

Desmosome-like junction
Odontoblast

Capillary

Nerve fiber

Cell-poor
Zone

Cell-rich
zone

FIG. 12-2 Diagrammatic representation of the odontoblast layer and subodontoblastic region of the pulp.

14. N

layer 14%,
Cell-poor zone — AAA

o Aye .,
Cell-rich zone 8 215, »
Ns Gy

Pulp proper— *
Ñ be

FIG. 12-1 Morphologic zones of the mature pulp.

15. Contents of the pulp
+ Cells i. Odontoblasts
ii. Fibroblasts
iii. Undifferentiated mesenchymal cells
iv. Defense cells
— Macrophages
— Plasma cells
— Mast cells
. Collagen fibers
— Typel
— Typell
ii. Ground substance
— Glycosaminoglycans
— Glycoproteins
— Water
« Blood vessels Arterioles, venules, capillaries
+ Lymphatics Draining to submandibular, submental and
deep cervical nodes
. Subodontoblastic plexus of Raschkow
. Sensory afferent from Vth nerve and superior
cervical ganglion

« Matrix

- Nerves

16. Odontoblasts

+ Encountered first when pulp is approached from dentin.

+ Number ranges from 59,000 to 76,000/mm? in coronal dentin

+ Number is lesser in root dentin.

+ Morphology reflects their functional activity.

+ Synthesize mainly type | collagen, proteoglycans.

+ When irritated, secretes collagen and large crystals into tubule
lumen, resulting in reduced permeability.

Predentin

Microtubule Secretory vesicle

Lysosome

Mitochondria
Centriole
Golgi complex

Cilia ne

Nucleus

Nucieolus

17. Differentiation of odontoblast cells

18. ts
; Fibroblasts

« Greatest in numbers.
« ‘Peter Pan'as they “never grow up".
+ Remain in relatively undifferentiated state.

Type | collagen is synthesized by odontoblasts and osteoblasts;
fibroblasts synthesize types 1, III, V and VII collagen.

D =

NG, LT.
4p — Fibroblast

19. Defense Cells: — nn
_ Hisfiocı

istiocytes and macrophages.
Polymorphonuclear leukocytes.
Lymphocytes.
Mast cells.

Mast cell Fibroblast Macrophage

20. Extracellular Components: The — extracellular
components include fibers and ground substance of pulp.

o Fibers:

+ The fibers are principally Type I and Type III collagen.

» Collagen is synthesized and secreted by odontoblasts and
fibroblasts.

» The overall collagen content of the pulp increases with
age, while the ratio between Type I and Type III remains
stable.

21. + Fibers are more numerous in radicular pulp than
coronal and greatest concentration of collagen
generally occurs in the most apical portion of the

pulp.

e This fact is of practical significance when a
pulpectomy is performed during the course of
endodontic treatment.

e Engaging the pulp with a barbed broach in the region
of the apex affords a better opportunity to remove
the tissue intact than does engaging the broach more
coronally, where the pulp is more gelatinous and
liable to tear.

22. eS
Ground substance:
* Glycosaminoglycans.
+ Glycoproteins.

+ Water.

Functions of ground substance

+ Forms the bulk of the pulp.

+ Supports the cells,

« Acts as medium for transport of nutrients from the vasculature
to the cells and of metabolites from the cells to the vasculature.

23. ortive elements
Arterial supply of teeth

External carotid artery

Mandibular Pterygoid Pterygopalatine
(first) (second) (third)
Infraorbital Posterior-superior
artery alveolar artery

Inferior
alveolar
branch

Anterior-superior
alveolar ai

rtery

\cisors + Molars
Canines + Premolars

24. Venous drainage of teeth

Veins from teeth and
other tributaries

Pterygoid plexus

Retromandibular vein

External or internal
jugular vein

25. ymphatic drainage of teeth

Maxillary teeth

+ Mandibular molars

« Mandibular premolars
Submaxillary
gland

« Mandibular canines

Superficial and deep
cervical nodes

Mandibular teeth

Mandibular
incisors

Submental
gland

26. Apical foramen

27. e Walls of arterioles and
venules are associated
with smooth muscles
which are innervated by
unmyelinated sympathetic
fibers. Arteriovenous

shunt

Arteriole

Metarteriole

True capillaries

Small venule

Venul
Vascular smooth u

muscle cells:

e When stimulated by
stimulus (e.g. epinephrine
containing local
anesthetics), muscle fibers Lymph vessel
contract, decreasing the
blood supply.

28. pal response to inflammation

+ Whenever there is inflammatory reaction, there is
release of lysosomal enzymes which cause hydrolysis
of collagen and the release of kinins.

e These changes further lead to increased vascular
permeability. The escaping fluid accumulates in the
pulp interstitial space. Since space in the pulp is
confined so, pressure within the pulp chamber rises.

+ In severe inflammation, lymphatics are closed
resulting in continued increase in fluid and pulp
pressure which may result in pulp necrosis.

29. Effect of posture on pulpal flow

+ In normal upright posture, there is less pressure effect
in the structures of head. When a person is upright,
baroreceptors maintain high degree of sympathetic
stimulation which leads to slight vasoconstriction.

+ On lying down, the gravitational effect disappears; there is
sudden increase in pulpal blood pressure and thus
corresponding rise in tissue pressure which leads to pain in
lying down position or reclining position. Lying down
increases blood flow to the pulp by removal of both
gravitational and baroreceptor effect.

30. Clinical correlation

A. Temperature changes:
1. Increase in temperature:
A 10° to 15°C increase in pulp temperature causes
arteriolar dilation and increase in intrapulpal pressure of
2.5 mm Hg/°C but it is transient in nature.
> The irreversible changes occur when vasodilation is
sustained by heating the pulp to 45%C for prolonged
periods, resulting in persistent increase in pulp pressure.
2. Decrease in temperature:
> It has been seen that at temperature lower than — 2°C, the
pulp tissue exhibits immediate pulpal pathology like
vascular engorgement and necrosis.

31. B. Local anesthetics:

+ The effect of local anesthetics on pulp vasculature is
mainly due to presence of vasoconstrictor in anesthetic
solution.

+ For example, presence of epinephrine in local anesthetic
causes decrease in blood flow in the pulp which is due to
stimulation of a-adrenergic receptors located in pulpal
blood vessels.

C. General anesthetics:
+ Produce effect on the velocity of blood flow in the pulp.

32. During endodontic therapy, if only some part of pulp is
extirpated, the profuse bleeding occurs whereas there
would be less hemorrhage if pulp is extirpated closer to
apex of the tooth.

+ This is because of increase diameter of the vessels in the
central part of the pulp.

E. Aging:
+ With increasing age, pulp shows decrease in vascularity,

increase in fibrosis, narrowing of diameter of blood
vessels and decrease in circulation.

e Finally, the circulation becomes impaired because of
atherosclerotic changes and calcifications in the blood
vessel leading to cell atrophy and cell death.

33. ° Dental pulp is abundantly innervated by both sensory
as well as autonomic nerve fibers. The nerve fibers
enter the pulp through apical foramen along with blood
vessels.

Anterior and middle
superior alveolar
nerve

superior
alveolar
nerve

Lingual
nerve

Inferior alveolar i , Long buccal
nerve

Mental and
incisive
nerve

35. er entering the pulp, the nerve bundles run coronally
and divide into smaller branches until a single axons
form a dense network near the pulp-dentin margin,
termed as plexus of Raschkow.

Innervation
density

A: > 40%
B:4-8% [ee]

e Also the individual axons may
branch into numerous
terminal filaments which enter
the dentinal tubules.

c:0.2-1% [EH

36. e Pain is complex phenomenon which is in form of the
evoked potential in the tooth that initiated signals to
the brain.

+ Regardless of the nature of sensory stimulus, i.e.
mechanical, chemical or thermal, almost all afferent
impulses from the pulp result in pain.

e The dental pulp contains both sensory and motor
nerves. The sensory nerves are encased in myelin
sheath.

37. a ann an
Classification of Nerve Fibers

Conduction
Type of Fiber Function Diameter (um) Velocity (m/sec)
A-alpha Motor, 12-20 70-120
proprioception
A-beta Pressure, touch 5-12 30-70
A-gamma Motor, to muscle 3-6 15-30
spindles
A-delta Pain, 15 6-30
temperature,
touch
B Preganglionic <3 3-15
autonomic
C dorsal root Pain 0.4-1 0.5-2
Sympathetic Postganglionic 0.3-1.3 0.7-2.3

sympathetic

38. e The myelin sheath is largely composed of fatty
substances or lipids and proteins. Myelin appears to be
internal proliferation of Schwann cells.

° The unmyelinated fibers are surrounded by single layer
of Schwann cells, but in these myelin spirals are absent.
The unmyelinated nerves are usually found in autonomic
nervous system.

e The nerve fibers are classified according to their
diameter, velocity of conduction and function. The fibers
having largest diameter are classified as A fibers while
those having smallest diameter are classified as C fibers

39. De The A delta fibers are faster conducting and are
responsible for localized, sharp dentinal pain. The C
fibers are slower conducting fibers and are considered
responsible for dull and throbbing pain.

Location of Intradental
Sensory Nerves

The pain receptors
transmit their message
to the central nervous
system at different
rates depending upon -
size, diameter and rss

C-fibers, unmyelinated
coating of the nerves. Schematic drawing illustrating the location of A and C fibers

in the dental pulp. Myelinated A fibers are located in the periphery of the pulp,
Penetrating the inner part of dentin. Unmyelinated C fibers are located in the
deeper part of the pulp proper.

40. ¿q ___— —
Difference between A-delta and C-fibers

A-delta fibers
High conduction
velocity (6-30 m/sec)
Myelinated
Pain is well localized
Low threshold
Sharp, quick and pricking pain

C-fibers
Slow conduction
velocity (0.5-2 m/sec)
Unmyelinated
Not well localized
High threshold
Dull and lingering pain

+ Thermal, chemical or mechanical stimuli stimulate C fibers resulting
in dull, poorly localized and throbbing pain. Electrical pulp tester
stimulates A delta fibers first because of their lower threshold.

+ As the intensity of stimulus is increased along with A delta fibers,
some of the C fibers also get stimulated resulting in strong
unpleasant sensation.

+ 80% of nerves of pulp are C fibers and remaining are A-delta fibers.

41. Anatomy of dental pulp '

» Pulp lies in the center of tooth and shape:
miniature form of tooth. |

» It is a unique connective tissue composed pri
from gelatin ground substance containing E
fibers and fiber bundles. \

i

» Embedded in this stroma, blood
vessels, lymphatics and nerve fibers.
This space is called pulp cavity
which is divided into pulp chamber
and root. PA soot cana

ET
ET

Pulp chamber

42. Pulp chamber

Is that portion of the pulp cavity contai
in the crown or body of the tooth, consists
a single cavity with projections (pulp hor
into the cusps of the tooth.

Pulp chamber

Pulp horn

43. Root canal

>

>

OO
PETT

Is that portion of pulp cavity which extends |
orifice to the apical foramen. \

The shape of root canal varies with size, shape
of the roots in different teeth. In most cases, nu
root canals correspond to number of roots but a rı
have more than one canal.

‘Meyer’ stated that roots which are round and
shaped usually contain one canal but roots whic
elliptical with flat or concave surface frequentl
more than one canals.

D
a =

44. The apical foramen

The apical foramen is
an aperture at or near
the apex of a root
through which nerves
and blood vessels of the
pulp enter or leave the
pulp cavity.

45. Normally, it is present near the apex, ¢
shape and location of foramen is seel
post-eruptive phase due to functional
(tongue pressure, mesial drift) acting.
tooth which leads to cementum resorpti
deposition on the walls of foramen.

This whole process resulted in new foramen
from the apex.

WWW

46. In young newly erupted teeth, it is wide open but as) the
root develops, apical foramen becomes narrower.

1 2 3 4 5

The inner surface of the apex becomes lined with the
cementum which may extend for a short distance into the
root canal.

Thus we can say that DCJ does not necessarily occur at the
apical end of root, but may occur within the’ main root
canal.

47. « Multiple foramina are frequent phenomenon in |
teeth. Majority of single rooted teeth have single «
terminate in a single foramina. \

Classification of root canal morpho

Weine 1969 Vertucciet al 1984

A À A

Type! Typen Type tit

IRA

Type I Type I] Type Ill Type IV Typev Type vi Type vu

A
as

48. Accessory canals ws
» They are lateral branches of the main

canal that form a communication
between the pulp and periodontium.

» Accessory canals contain connective
tissue and vessels and can be seen
anywhere from furcation to apex but
tend to be more common in apical
third and in posterior teeth.

Accessory and
lateral canals

» Exact mechanism of their formation is not known
occur in areas of premature loss of root sheath cells be
these cells induce formation of odontoblasts.

They also develop where developing root encounter:
vessel. If vessel is located in this area, wher:

forming; hard tissue may develop around it ma
canal from radicular pulp.

49. Functions of pulp

Nutrition: blood supply for pulp and dentin.

Sensation: Through the nervous system, pulp
sensations mediated through enamel or denti
higher nerve centers. Pulp transmits pain and
temperature and touch. \

Formative: The pulp involve in the support, main
and continued formation of dentin.

Defensive: Triggering of inflammatory and
response.

Protective: Development and formation of secon
tertiary dentin which increase the coverage of

50. Age changes in the pulp

Increase in peritubular dentin, dentinal sclerosis, and
number of dead tracts. Dentinal sclerosis produce
gradual decrease in dentinal permeability as the dent
tubules become progressively reduced in diameter.

Gradual decrease in the cellularity and increase in t
number and thickness of collagen fibers, particularly in t
radicular pulp.

The odontoblasts decrease in size and number, and-t
may disappear altogether in certain areas of the p
particularly on the pulpal floor over the bifurcation or
trifurcation areas of multi-rooted teeth.

51. » Possibility of reduced ability of pulp to react \
to the irritants and repair itself.

» Degeneration and loss of myelinated and
unmyelinated axons. This results in decrease
in sensitivity.

» Reduction in number of blood vessels.

52. 2° cementui

« Continued formation of
secondary dentin throughout life 2 dentin
gradually reduces the size of the
pulp chamber and root canals.

« Presence of dystrophic _
calcification and pulp
stones; the thick collagen Pulp stone
fibers may serve as foci for Linear
pulpal calcification. BE

53. Pulp stones are nodular calcified
masses appearing in either coronal
and radicular pulp or both of these.

The larger calcifications are called
denticles or pulp stones. It is seen
that pulp stones are present in at
least 50% of teeth.

Pulp stones may form either due to
some injury or natural phenomenon.

54. Classification of pulp stone
+ According to structure
— True
— False
- According to size
— Fine
— Diffuse
+ According to location
— Free
— Attached
— Embedded

lined by odontoblasts. These are rare
and are usually located close to apical
foramen. E

False stone: Formed from
degenerating cells which mineralize
They may arise around vessels.

55. - According to size:
- Fine.

- Diffuse: Diffuse calcifications are also know
calcifications because of their longitudinal orientatio
found more frequently in the root canals, but can also b
the coronal portion of the pulp. They are aligned clo
blood vessels, nerves or collagen bundles.

+ According to location:

Free pulp

- Free stone: not related to pulp space 3. PE. AU

wall, surrounded by soft tissue. ns er Pup
Oa Des

- Adherent stone: attached to wall of se P

pulp stone

space, not fully enclosed by

Dentin

Embedded stone: enclosed within ses
nal wall, less attached than the ””*"”
ve. A

56. Clinical significance of pulp stones
Presence of pulp stones may alter the internal anatomy of
the pulp cavity, making the access opening of tooth difficult?

They may deflect or engage the tip of endodontic
instrument.

Since the pulp stone can originate in response to chronic
irritation, the pulp chamber which appears to have diffuse
and obscure outline may represent large number Gf

irregular pulp stones which may indicate chronic irritation
of the pulp. sai

LE
|

it \
E

4

£

57. Pulpal reactions to traumatic injuries

» Pulpal reactions to traumatic injuries can
vary from immediate pulpal death to long-
term slow pulp canal mineralization.

« The prognosis of pulpal healing and survival,
following trauma, depends on the degree and
type of trauma, age of the patient and the
condition of the tooth in the posttraumatic
period.

» The pulpal reactions to traumatic injuries,
based on the prognosis of pulpal healing, are

classified into three main categories:

58. Category 1: Pulp with very poor prognosis for he

+ In these cases, the traumatic incident resul
pulpal necrosis in a matter of days to a month
thus requires endodontic therapy soon thereafte

+ It is usually seen in cases of an extensive cro
fracture together with subluxation, an extrusi
luxation, an intrusive luxation or a lateral luxation.

Subluxation: injury to the supporting apparatus of the
tooth that results in increased mobility.

Luxation: injury that causes displacement of the tooth
in the coronal, apical or lateral direction.

59. Category 2. Pulp with a moderate prognosis for hf

» In these cases, tooth shows rapid pulpal minerali
within a period of 1.5-2 years. \

« Subluxation injury, concussion injury and lat
luxation injury are the main types of traumatic inju
in this category.

+ It requires endodontic therapy.

Concussion: injury to the supporting apparatus of the tooth
that result in clear sensitivity to percussion. /

60. Category 3. Pulp with a very good prognosis for heal

» These teeth show slow pulp canal mineralization,
rarely require endodontic therapy. \

+ They usually contain vital pulp tissue and under
very slow mineralization of the pulp canal, over
period of five years or more. \

61. Calcific metamorphosis (CM)

Calcific metamorphosis is defined as a pulpal respons
trauma that is characterized by deposition of hard tis
within the root canal space. Approximately 4-24%
traumatized teeth develop varying degrees of pul
obliteration.

The frequency of CM depends on the extent and severity
the injury and the stage of the root development at th
time of the event.

Calcific metamorphosis occurs commonly in young adu
because of trauma. It is evident usually in the ante
region of the mouth and can partially or totally obliterate
the canal space radiographically.

62. » The literature is clear that calcific changes
may be a response to a wide range of
stimulants: operative procedures,
restorative materials, caries, tooth
abrasion, periodontal disease, pulp
inflammation, pulp capping, trauma and
ageing. Some may be idiopathic.

+ Use of fixed splints like orthodontic
bands/acrylic fixation can cause additional
trauma to the already traumatized periodontal
ligament due to forceful placement of the
bands.

63. Several hypotheses of CM

v Restriction of the pulp’s neurovascular supply wi
after healing, leads to an increased deposition of dentine.

v Uncontrollable mineralization because of the failure
normal functioning of self-limiting pyrophosphata:
enzyme. A reduced capillary permeability following t
increased number of calcium ions could reduce serum flo
within the dental pulp, resulting in a low concentration
inhibitory pyrophosphate ions.

Y Loss of the parasympathetic inhibition could cause
reduction in pulpal blood supply that could result in cellu
respiratory depression, leading to pathological mineralizati
of the pulp and, eventually, obliteration of the root canal.

64. Clinical picture of calcific
metamorphosis is a tooth with
darker in hue than the adjacent
teeth and exhibits a dark yellow
color because of decrease in
translucency from greater thickness
of dentin under the enamel.

However, not all such teeth become discolored, and there is ne:
correlation between amount of discoloration and degree of C

Responses to heat and cold decrease with time and the response
to electric pulp tests may be normal in the early stages but absent
in the later stages.

Teeth with CM may or may not have symptoms, depending on
the status of pulp tissue within the mineralized canals.

65. The radiographic appearance of CM is partial or
obliteration of the pulp canal space, with a n
periodontal membrane space and intact lamina dura.

When CM is associated with apical periodontitis
thickening of the periodontal ligament space
periradicular radiolucency may be observed, with
without subjective symptoms.

66. Management of pulp canal obliterati

Pulp canal obliteration nn
er E
‘Symptomatic and/or radiographic No symptoms or radiographic signs of
signs of periapical pathosis periapical pathosis
Row canal treatment No discolouration Discolouration andor sesthetic
required concern
| AS
Discolouration and! Elective root Vital bleaching
een, nr names]
LE |
+ Pa

Partial coverage Non vital Unsatisfactory Satisfactory
restoration bleaching result result

‘Satisfactory result ] Option 2

67. A. Endodontic treatment of teeth

+ Endodontic treatment should be performed only in
those cases where signs or symptoms of apical
periodontitis appear.

+ It should be initiated in teeth with tenderness to
percussion, PAI (periapical index) scores 23 and a
negative response to sensibility testing.

The PAI index was classified by Orstavik et al. in 1986 as following:

Grade 1: Normal periapical structures.

Grade 2: Small changes in periapical bone structure.

Grade 3: Changes in periapical bone structure with some mineral
characteristic of apical periodontitis.

Grade 4: Periodontitis with well-defined radiolucent area.

Grade 5: Sever periodontitis with exacerbating features and bone expansion.

68. Success in root canal treatment is
based on proper debridement,
cleaning and disinfection of root
canal space of microbial
contaminants and pulpal debris and
their obturation.

Figure 3. Pre-operative radiograph showing
calcified canals.

Figure 4. Canal negotiation and working length
determination.

Figure 5. Post-operative radiograph — obturation.

69. + This may be clinically difficult to achieve in these
cases owing to calcified pulpal space and root
canals and the presence of the unusual canal
morphology created by the calcification process.

\

+ The prognosis of teeth with CM treated with non-
surgical endodontic treatment has shown an
overall success rate of 80-89%.

The success rate for roots without periapical
radiolucency is reported to be 98% and with
preoperative periapical radiolucencies is 63%.

70. Access opening

+ The access cavity in these teeth should be
of normal size and shape, similar to that
opened in teeth with normal pulpal
extension.

+ Secondly, it is equally important to be
thorough with the normal root canal
anatomy, geometric pattern of canal
orifices, and their potential variations.

+ If necessary, rubber dam should not be
applied until the canal(s) have been , access cavity: similar to non
identified to ensure that access cavity
preparation is following the long axis of the
roots.

71. Penetration

« Long-necked round drills or long shank
burs (tapered diamond) may be used with
a gentle brush stroke action.

+ Small long shank excavators or ultrasonic
endodontic tips are also effective in
removing the pulp mineralization and
stones.

b. Initial penetration: 45°

« An access cavity is started by penetration
at 45° to the long axis.

However, continued penetration at the same
calcified canals will result in perforation of th
surface below the gingival attachment. —

72. + Therefore, if the canals are not located aft
of penetration, the bur must be rotated pare
long axis of the tooth in order to prevent pı
In deep excavations, the bur may be chan
long-shank No.2 round bur. \

e. Access Preparation: Parallel to lona avis

73. Canal orifice exploration and dor
« The most important instrument
for orifice location and

exploration is the DG-16
endodontic explorer.

+ Sometimes, a change in the color of dentine in the ce
root will indicate the position of the canal.

« Tertiary dentine overlying the canal entrances m
differentiated from physiological secondary dentine
whiter/opaque appearance, compared to the yellow/gr
of secondary dentine.

Use of magnification devices (loupes and
ultrasonic are equally helpful for locating root ca

74. « An advantage of using ultrasonic tips over burs for the |
of mineralized canals is that they maintain ‘hi
efficiency without rotation, enhancing the safet
over the instrument and reducing the risk of perforations.

A
+ During the initial phase, larger size troughing tips with a limi

diamond-coated extension should be used.

+ Subsequently, thinner and longer tips should be used in deeper a
so as to maintain a clear vision.

+ Sometimes a contrast medium can be used to disclose a root
which was not seen in earlier radiographs.

75. + Compared to unaided vision,
magnification device, especially microscop
enhances the visibility of the canal orifice and
root canal to a much greater depth, avoiding
unnecessary removal of tooth structure and chance
of perforations. It is an easier and more preci
method of locating the canal orifices.

76. Radiographic confirmation of canal location

* To reduce the chances of tooth perforation, it is
proposed to take at least two radiographs at different
angulations in order to establish and indicate the
angulation of the bur/drill in the root and the position of
the root canal.

+ Usually, one straight angulation radiograph and
another from either the mesial or the distal projection
are taken.

+ On deeper penetration of the bur, as the bur head
becomes closer to the canal projection, the information
gathered by considering only one projection, either
mesial or distally, may be insufficient, misleading and
incorrect.

77. « Therefore, in most of the cases, a third radiograph is
obligatory. The first radiograph is straight-on, the second
radiograph is taken with a 20° horizontal angle with the
cone shifted distally, and the third radiograph also has a
20° horizontal angle with the cone directed mesially.

m

No Angulation change in
bur/drill position

Figure 8. Radiographic confirmation of canal location.

78. |

Canal negotiation

* Once the orifice is exposed and the canal
has been identified with a DG16 probe, a
small file (06, 08 or 10 K-file) with lubricant
is placed into the orifice, and is used gently
in watch winding action to negotiate the ~
canal.

DIE 1 0 LI
02493701721

+ Instruments like Canal Pathfinder,
Pathfinder CS or Canal Orifice Shapers can
also aid in canal negotiation as these can
penetrate even highly mineralized canals.

Rigid ‘C-Pilot’ hand files = :
are also available that are rm ~ Be sensi
specifically designed to N = -— ET)
negotiate mineralized 2

canals. 12.5 e ——

79. « Though the use of chelating agents have been
advocated for locating the difficult-to-find orifices
by sealing them in the chamber between
appointments, their clinical usefulness remains
doubtful.

» These chelators fail to soften the mineralized pulp
chamber for access to the patent root canal and
can slightly alter the walls, thereby limiting the
ability of instruments to be guided along the hard
dentine.

« Thus, chelating agents are seldom of value in
locating the orifice and can only be used to soften
the canal after it has been located and during the
canal preparation.

80. Cleaning and shaping

Root canals may be cleaned, shaped and filled in the
conventional manner. The following important points should be
kept in mind during cleaning and shaping of mineralized canals:

.

Use the thinnest possible file initially to negotiate
the root canal up to the apical foramen.

Too early a change to a larger file may lead to a
false route or accumulation of dentinal debris in the
root canal.

Advance instruments slowly in the calcified canals.
Inspect before every re-insertion.

Irrigate copiously with 2.5-5.25% NaOCl. This
lubricates the canal, dissolves the organic debris
and keeps dentine chips suspended in the solution.

81. « Use chelating pastes or solutions
facilitate widening of the canal. |

+ Use ultrasonic instruments in the pul
chamber to loosen the debris.

The use of newer nickel-titanium rota
systems is highly useful and should
considered, when possible. :

82. B. Surgical endodontics

+ Symptomatic teeth that exhibit
complete CM radiographically, or
cases in which the canals cannot be
found and negotiated by routine
endodontic treatment, are good
candidates for periradicular surgery
and subsequent retro-filling.

83. References

1.

Fonseca GM, Fonseca MM. Calcific metamorphosis
with pathological root resorption in permanent
teeth: morphohistometric evaluation of two cases.
Int. J. Morphol. 2015; 33(2):712-718.

Malhotra N, Mala K. Calcific metamorphosis.
Literature review and clinical strategies. Dent
Update. 2013; 40(1):47-60.

McCabe PS, Dummer PM. Pulp canal obliteration:
an endodontic diagnosis and treatment challenge.
Int Endod J. 2012; 45(2):177-197.

Garg N, Garg A. Textbook of Endodontics, 3 ed.
Jaypee Brothers Medical Publishers (P) Ltd, New
Delhi, India, 2014; chapter 2: Pulp and periradicular
tissue.

Cohen S, Hargreaves KM, Berman LH. Cohen's
pathways of the pulp, 11' ed. Elsevier Inc. St. Louis,
Missouri, 2016; chapter 12: Structure and functions
of the dentin-pulp complex.