Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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INTRODUCTION
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ENDO= means inside
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DONTIC= tooth
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Endodontics may be simply defined as the branch of dental science concerned
with the study of anatomy, physiology, pathology, and treatment of the dental
pulp and periradicular region. Endodontic treatment includes any procedure
designed to maintain the health of all, or part of, the pulp. When the pulp is
diseased or injured, treatment is aimed at maintaining or restoring the health of
the periradicular tissues, usually by root canal treatment, but occasionally in
combination with endodontic surgery.
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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The principle of endodontics is to clean, shape and fill the root canal system.
We also can add the principle of doing a root canal in such a fashion that we
can restore the tooth and reestablish the occlusion. It is not particularly
beneficial if we do a root canal yet destroy the tooth in the process. It is
absolutely crucial for the success of the root canal that we be able to restore the
tooth and prevent microleakage
If these are the principles to endodontics, the four keys to endodontics are:
1.
Diagnosis.
2.
Access.
3.
Instrumentation.
4.
Obturation.
Diagnosis is certainly the most difficult aspect of endodontics,
Access is certainly the key to successful clinical endodontics.
Shaping of the canal is done by either hand or engine-driven instruments.
Cleaning is done by irrigating the canal system with one of a number of
solutions that may be antibacterial and have tissue-dissolving ability.
Obturation is achieved with gutta-percha and a root canal sealer.
The cleaning and shaping phase of endodontic treatment is regarded as the
most important. When the canal is clean, it is important that the system is not
recontaminated by microorganisms. Because of the complex anatomy of the
root canal system, complete disinfection is almost impossible to achieve. It is
important, therefore, that any remaining microorganisms in the dentinal tubules
are prevented from multiplying by the use of an antimicrobial dressing
followed by three-dimensional filling. Recontamination from the oral cavity
must be avoided, and the importance of a good coronal seal cannot be
overestimated.
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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The tooth remains very much alive after endodontic therapy, because its living
root surfaces are nourished by the adjacent tissues of the gums and jaw. Only
the interior of the tooth loses living tissue with root canal treatment.
Saving a tooth this way is better for your health than extraction, and is less
costly than replacing the missing tooth.
Is Endodontic Treatment Effective?
YES!!! Routine endodontic therapy is among the most effective procedures in
modern dental or medical practice.
Research studies of conventional
endodontic therapy document success rates of about (100% - endodontist
abilities).
The keys to success are accurate:

Diagnosis, selection of appropriate cases for treatment,

Use of proper endodontic techniques, along with meticulous attention to
detail and sterility during treatment.
Following proper endodontic therapy and restoration, treated teeth typically last
a lifetime.
In the rare instances when endodontic treatment is not successful, the tooth can
often be retreated successfully. Endodontic re-treatment can be done using
conventional methods.
SCOPE OF ENDODONTIC
The extent of the subject has altered considerably in the last 50 years. Formerly,
endodontic treatment confined itself to root canal filling techniques by
conventional methods; even endodontic surgery, which is an extension of these
methods, was considered to be in the field of oral surgery. Modern endodontics
has a much wider field and includes the following:
1.
Diagnosis of oral pain.
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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2.
Protection of the healthy pulp from disease or injury.
3.
Vital pulp therapy (direct and indirect capping).
4.
Pulpotomy (conventional and partial).
5.
Pulpectomy.
6.
Root canal treatment of infected root canals.
7.
Surgical endodontics, which includes apicectomy, hemisection root
amputation and replantation.
Value of Endodontics: Saving irreplaceable teeth

Avoiding free end saddles

Providing teeth for multiple splint abutments

Preservation of alveolar bone

Avoiding total edentulism

Facilitating restoration: after fracture of a tooth resulting in insufficient
supra-gingival structure for a crown

Aid in accommodating attachments like keys and keyways

Limiting number of artificial teeth in RPD

Preserving teeth with greater bulk
( posterior ) to serve as RPD
abutments

Retaining the most posterior bridge abutment Preserving enough teeth
for use with a fixed bridge

Lessening of bridge span

Help to obtain a more esthetic prosthetic result
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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ENDODONTIC ANATOMY
The Dental Pulp: The dental pulp is a connective tissue encased in a rigid hard
tissue. It consists of cells, ground substance, and neural and vascular supplies.
The pulp, in conjunction with the dentin that surrounds it, is referred to as the
pulpo-dentin complex. Dentin is a specialized connective tissue of
mesenchymal origin. It is laid down by highly differentiated and specialized
odontoblasts and forms the bulk of the mineralized portion of the tooth Tubules
contain the long narrow odontoblastic process. It is uncertain whether these
processes travel to the midpoint of the dentin or the full distance to the dentinenamel junction. The tubules are filled with fluid and fluid exchange may occur
from the pulp outwards or from the enamel towards the pulp.
Peritubular dentin lines the tubules and is laid down by the odontoblast process.
Peritubular dentin is thought to form as a normal consequence of aging and
may be accelerated by stimuli such as caries, attrition, and abrasion. Occlusion
of dentinal tubules by this process and by mineral crystals is called sclerosis
and gives aged teeth their characteristic translucency.
Primary dentin forms during tooth development. Secondary dentin forms once
the teeth are fully developed and is laid down evenly over the entire pulpal
surface; it is also known as physiological or regular secondary dentin
Odontoblasts cell bodies are separated from mineralized dentin by an
unmineralized layer known as predentin. Odontoblasts form a single layer of
cells, but in histological section appears as a multilayered structure because
their nuclei are at different levels. Odontoblasts are incapable of further
division once fully mature, and if damaged, may be replaced from
undifferentiated mesenchymal cells. The remainder of the pulp consists of
ground substance into which are embedded fibroblasts and inflammatory cells
and a complex network of blood vessels and nerve fibers.
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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The Functions of the Pulp
The primary function of the pulp is formative and defensive. Defense reactions
are essential to the survival of the pulp. The pulp has also been thought to act as
a sensory organ that warns against disease (i.e., loss of tooth substance) by
eliciting pain, but this is a relatively poor warning system considering the
number of teeth whose pulps become irreversibly inflamed, apparently without
warning. Any tooth deformation resulting from loads may be detected by
proprioceptors in the pulp. Although the existence of a proprioceptive
mechanism has not been proven, it does offer an explanation for the
susceptibility of pulpless teeth to fracture.
The Vascular Supply of the Pulp
The vascular system of the pulp helps it to overcome problems of encapsulation
within the rigid tooth. Arterioles from the dental arteries (A. facialis) enter
through the apical foramina and pass centrally through the pulp, giving off
lateral branches, which divide further into capillaries. Smaller vessels reach the
odontoblastic layer, where they divide extensively to form a plexus below and
within the odontoblastic layer. Venous return is collected by a network of
capillaries, which unite to form venules coursing down the central portion of
the pulp. The unique feature in this arrangement is the arteriovenous shunt,
which prevents build-up of unsustainable pressure in the rigid environment.
Lymphatic vessels have not been definitely confirmed. In general, with age, the
blood supply diminishes and its architecture becomes simpler. This diminished
blood supply may render a pulp more susceptible to irreversible damage.
The Nerve Supply of the Pulp
The dental pulp is richly innervated with sensory and autonomic nerve fibers.
These enter the pulp with the blood vessels through the apical foramina. As the
nerve bundles pass coronally they divide into smaller branches and form the
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dense plexus of Raschow. Individual axons may branch into many terminal
filaments, which in turn may enter the dentinal tubules; one axon may innervate
up to 100 dentinal tubules. Some tubules may contain several nerve fibers.
The autonomic nerve supply consists of sympathetic fibers, which control the
microcirculation. The sensory innervation consists of two (possibly three) types
of fibers. The faster conducting A-d-fibers are thought to be responsible for
sharp, localized dentinal pain experienced during drilling, probing, air drying,
application of hyperosmotic fluids, and heating or cooling dentin. The common
feature of these stimuli is that they cause rapid movement of fluid in the
dentinal tubules, which cause mechanical distortion of tissue in the pulp-dentin
border and stimulates the A-d-fibers (the hydrodynamic theory). Opening
dentinal tubules by acid etching may increase sensitivity of dentin. Conversely,
blocking the tubules, for example by composite resins or naturally by sclerosis,
prevents fluid flow and desensitizes dentin.
Stimulation of the slower conducting, unmyelinated C-fibers are thought to
give rise to the duller, throbbing, less localized pain. The C-fibers are activated
by thermal, mechanical or chemical stimuli reaching the deeper parts of the
pulp
A third type of nerve, the A-ß-fibers, is myelinated and has the most rapid
conduction velocity. These fibers are thought to respond to non-noxious
mechanical stimulation of the intact crown and may be important in regulating
mastication and loading of teeth, but they also respond to stimulation of dentin.
The Periradicular Tissues—Cementum
Cementum covers the radicular dentin. The cementum is primarily an inorganic
tissue and is more impervious than dentin. Cellular cementum contains
cementocytes which communicate with each other via canaliculi and with
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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dentin. It is usually found in the apical and furcation regions of the tooth.
Sharpey’s fibers may be embedded in cellular cementum. Acellular cementum
forms the innermost layer of cementum and is devoid of cells. It covers almost
the whole root surface in a thin hyaline layer. It contains closely packed
mineralized periodontal fibers. Intermediate cementum is found at the
cementodentinal junction and has characteristics of both cementum and dentin.
The function of cementum is to provide attachment for the periodontal ligament
fibers, which suspend the tooth from the alveolar bone, and repair.
The Periradicular Tissues— Periodontal Ligament
The periodontal ligament is a dense fibrous connective tissue that supports the
tooth and attaches it to its socket. Its principal component is collagen, which is
embedded in a gel-like matrix. The fibers are arranged in specific groups with
individual functions. These include gingival, transseptal, alveolar crest,
horizontal, oblique, and apical fibers. Functional adaptation may take place in
the broad zone known as the intermediate plexus. The main cells of the
ligament are fibroblasts with occasional inflammatory cells. The root sheath of
Hertwig, which helps root formation, does not totally involute once root
formation is complete, but degenerates into what resembles a perforated bag of
epithelial cells, sometimes described as the rests of Malassez. These cells can
proliferate when stimulated by inflammation to form a cyst.
The blood supply to the periodontal ligament originates from the inferior dental
artery. Arterioles enter the ligament near the apex of the root and from lateral
aspects of the alveolar socket and branch into capillaries within the ligament in
a polyhedric pattern along the long axis of the tooth. Collagen fibers run
through the spaces. The blood vessels are closer to the bone than to the
cementum. Venules drain the apex through apertures in the bony wall of the
socket and into the marrow spaces.
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Nerve bundles enter the periodontal ligament through numerous foramina in
the alveolar bone. They branch and end in small rounded bodies near the
cementum. The nerves carry pain, touch, and pressure sensations and form an
important part of the feedback mechanism of the masticatory apparatus.
Functions of the periodontal ligament includes proprioceptive functions and
acting as a viscoelastic cushion because of its fibers and hydraulic fluid
systems (blood vessels and their communication with vessel reservoirs in the
bone marrow and interstitial fluid of the ligament). The ligament has great
adaptive capacity; it responds to functional overload by widening to relieve the
load on the tooth. Vascular communications between the pulp and
periodontium form pathways for transmission of inflammation and
microorganisms between the tissues.
The Periradicular Tissues—Alveolar Bone
Alveolar bone supports the teeth by forming the other attachment for fibers of
the periodontal ligament. It consists of two plates of cortical bone separated by
spongy bone. In some areas, alveolar bone is thin with no spongy bone. The
alveolar bone and cortical plates are thickest in the mandible. The shape and
structure of the trabeculae of spongy bone reflect the stress-bearing
requirements of a particular site. The surfaces of the inorganic parts of bone are
lined by osteoblasts responsible for bone formation. Those cells which become
incorporated within the mineral tissue are called osteocytes and maintain
contact with each other via canaliculi; osteoclasts are responsible for bone
resorption and may be seen in the Howship’s lacunae.
Pulp space or cavity : it is arbitrary divided into the pulp chamber (coronal)
and root (radicular) canals. Pulp chamber usually described as that portion
within the crown, it is a single cavity, the dimensions and shape were vary
according to the outline of the crown and the structure of the roots and the age.
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There are projection or prolongations in the roof of the pulp chamber that
correspond to the various major cusps or lobes of the crown which is called
(pulp horn). In multirooted teeth the depth of the pulp chamber depends upon
the position of the root furcation and my extend beyond the anatomical crown.
In the young teeth the outline of the pulp chamber resembles the shape of the
exterior of the dentine. With the age the dentinal tubules and pulp chamber
becomes reduced in size particularly in the areas where there has been caries,
attrition, aberration and exposure to operative treatment, So the CHAMBER
MAY THEN BECOME IRREGULAR IN OUTLINE, in addition to reduction
in the content of the pulp. For example, in molars, the roof and floor of the
chamber show more dentin formation, eventually making the chamber almost
disclike in configuration…..
The root canals are continuous with the pulp chamber and normally their
greatest diameters is at the pulp chamber level which is called “canal orifices”.
Because the roots tend to taper toward the apex, the canals also have a tapering
from which ends in constricted openings at the root end, the “apical foramina” .
it is possible for any root of tooth to have a number of apical foramina. The
branching of the main canals to these foramina called Accessory canals and the
root apex referred to as a delta system because of its complexity. Generally ,
these aberrations are neither detectable nor predictably negotiable and are
neither well debrided nor obturated.
Lateral canals can be found anywhere along the root length and tends to be at
right angles to the main root canals especially in the coronal (furcal) and
middle third if the roots. The accessory and lateral canals may demonstrated
only by histological examination. The presence of these canals in teeth with
diseased pulps and periradicular areas allows an interchange of inflammatory
break down and bacteria from the pulp to the periradicular area and viscera
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
which may
influence
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the outcome of root canal treatment success and
maintenance of periodontal health.
Apical foramen: As the epithelial root sheath proliferates downward and away
from crown, it enclosed more dental papilla until only a basal (apical) opening
remains. At the first the foramen located usually at the end of anatomic root.
With the age and development it becomes smaller and more eccentric. This
eccentricity is more pronounced as apical Cementum forms, changing again as
Cementum deposition continues passively or in association with coronal wear
and tooth drifting. it is possible for any root of tooth to have a number of apical
foramina especially in the multirooted teeth, the largest on referred as apical
foramen and smaller as accessory canals. Apical foramen size in the mature
tooth ranges usually 0.3-0.6 mm, the largest diameters being found on the distal
canal of lower molars and palatal root of upper molars. Foramen size and
location are unpredictable and difficult to accurately determined clinically. The
average distance between the apical foramen and the most apical end of root
ranged 0.2-2.0 mm. furthermore, the apical constriction tends to occurs about
0.5-1.0 mm from apical foramen (coronally). Ideally the apical constriction
should be used as a natural “stop” in root canal treatment, and the integrity of
the constriction should be maintained during treatment if complications are to
be avoided.
Root and canal anatomy
Although root shape in cross section is variable, there are six general
configurations: round, oval, deep oval, bowling pin, kidney (bean), and
hourglass.
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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Shape and location of canals are related greatly by root shape. Different shapes
may appear at any level in a single root teeth. One root may contain tow canals,
a basic rule is to assume that the root contains two canals until proved
otherwise. The most frequent roots includes: upper premolars, MB root of
upper molars, lower incisors, lower premolars and distal root of lower molars.
Most canals are curved, and most curvatures occur in a facial-lingual direction.
Therefore, a curved canals is often undetectable on routine radiograph. As a
rule, when 2 canals occur in a root thy tend to be round to oval. In the deep
facial-lingual root with root mesial or distal concavities (hourglass or kidney
bean shaped), a single canal may have a bowling pin or hourglass shape.
Regardless of the shape in the cervical third, in the apical curvature the root
(and canal) tends to become more round to oval.
The number of canals in a root reflects the facial-lingual depth and shape of the
root at each level, the deeper the root, the more likely that there are the 2
separate definitive canals. If the root tapers toward the apical third there is a
greater likelihood that the canals will converge to exit as a single canal.
Irregularities and aberrations are frequent in fact, commonplace. This is
particularly true in posterior teeth. Such aberrations include : hills and valleys
in canal walls, intercanal communications (isthmuses between canals) and
others
Types of configurations of root canal
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Lecture one ----------------------------------------------------------------- ‫امحد غامن‬.‫د‬
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Oral pain often is difficult to pinpoint. Because of the vast network of nerves in
the mouth, the pain of a damaged or diseased tooth often is felt in another tooth
or in the head, neck or ear. An endodontist may be helpful in either diagnosing
or treating this type of pain. All endodontically treated teeth require special
restorative care and treatment (either a filling, inlay, onlay, or crown) after
endodontic care is finished.
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