Introduction
A successful endodontic treatment requires appropriate access cavity
preparation, adequate cleaning and shaping and a complete three-dimensional
obturation(1)
. The endodontic access cavity is considered the foremost step in root
canal treatment(2)
.
Preparing an adequate access cavity and identifying the canal orifice can be
challenging and may create a massive loss of tooth structure that is associated with
a higher risk of fracture and a high failure rate(3)
. Several designs of endodontic
access cavities have been proposed to minimize tooth structure loss, thus
theoretically increase mechanical stability, and fracture resistance of root-filled teeth
(4)
.
One of these designs is a traditional endodontic access cavity design. It
focuses on including all the pulp horns and deroofing the pulp chamber in order to
achieve sufficient debridement of the coronal portion of the root canal system(5)
. The
extension of access cavity preparation may decrease strength of the tooth to fracture
under functional load(6)
. A new modification of access cavity design, which is
conservative endodontic access that is a small conservative cavity allows the
clinician to access all the canal orifices and minimizes the tooth structure removal
through preserving some of the pulp chamber roof and the peri-cervical dentin)PCD)
(7)
.
Another form of ultra conservative access cavity design is truss endodontic
access. It is a direct access from the occlusal surface to expose the mesial and distal
canal orifices while leaving the intervening dentin intact(8). Factors such as
maintenance of marginal ridge integrity and width of isthmus region may be
important in reducing tooth fracture(9)
.
The development of new radio diagnostic technologies like cone beam
computed tomography(CBCT) has led to great advances in access cavity design
2
based on the concept of guided endodontics(10 ,11).The combination of CBCT and
construction of guide by surface scan aimed to gain a straight access cavity, avoid
risk of root perforation and fracture of instruments during preparation (12,13)
.
In minimally invasive access cavity designs, the space available for irrigation
solution flow is reduced due to the preservation of the pulp chamber roof. Therefore,
activation of irrigation solutions is recommended to increase the contact area and
enhance the irrigant efficiency (14). Ideal irrigants should flush out debris, dissolve
organic tissue, kill microbes, destroy microbial by- products, and remove the smear
layer in order to accomplish these objectives, there must be an effective irrigation
system(15,16)
.
Conventional irrigation system by side vented needle associated with apical
positive pressure is the traditional method used in endodontic treatment(17).The main
disadvantage of this system is that irrigant does not extend much beyond the tip of
irrigation needle which affects debridement efficacy of the irrigant(18)
.To overcome
the disadvantages of irrigant delivery by traditional methods in inaccessible areas,
the apical negative pressure system is introduced to enhance the irrigant delivery to
apical areas , irregularities of the root canal and obtain a good flow of the irrigating
solutions (19,20)
. Although the apical negative pressure is more safe than the apical
positive pressure because it applies suction rather than forceful injection(21,22)
.
Little researches were done to evaluate the cleanliness of the pulp chamber
and root canals with different access cavity designs and irrigant activation