Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

50


Chapter 2
POOC02 02/18/2005 04:33PM Page 50

---

51
3
Principles of endodontics
INTRODUCTION
Endodontology is related to processes that take place in, or originate
from, contents of the pulpal chamber. Under normal conditions, 
the pulp is protected by the hard tissues of the tooth and an intact
periodontium. Kakehashi et al.
1
showed that when the dental pulps 
in germ-free rats were exposed, reactionary dentine was formed.
However, surgical exposure of teeth in rats kept in a conventional
microbial environment resulted in the development of pulpal 
necrosis and apical periodontitis. Therefore, micro-organisms (such
as those associated with the caries process) and their by-products may
gain access to the pulp and stimulate an inflammatory response. The
pulp may maintain its function, but continued stimulation will result
in its irreversible destruction and complete breakdown. A necrotic
pulp does not have a defence mechanism, and the enclosed environ-
ment of the pulp chamber is a favourable medium in which anaerobic
bacteria may proliferate. This inflammatory process may then spread
beyond the confines of the pulp chamber and into the periapical 
tissues with consequent tissue damage and resorption of periapical
bone. Early signs may be seen on a radiograph as loss of apical lamina
dura, more extensive destruction of the periapical tissues may result
in stimulation of epithelial cells in the apical region, which can then
cause formation of a cyst.
Therefore, treatment of the irreversibly damaged or necrotic pulp
should be by removal of the damaged tissue and its replacement with
a root filling, the overall aim being to control the intra-canal infection.
The canal system is cleaned with files and antimicrobial irrigating
solutions before being filled with an inert material (root filling) to pre-
vent further microbial ingress. It is also necessary to have excellent
moisture control, so that the canal system can be dried when required,
POOC03 02/18/2005 04:33PM Page 51

---

and also to ensure that contamination of the canal system with 
salivary bacteria does not occur: airway protection is also required
owing to the risk of dropping the small instruments. To achieve these
objectives, placement of a rubber dam is essential.
The response to endodontic treatment is measured in terms of 
clinical signs and symptoms and radiographic evidence of healing. 
If healing is not satisfactory it is necessary to make a decision as 
to whether the tooth should be re-treated, treated via a surgical
approach or extracted.