ACCESS CAVITIES Dr Saidah Tootla 1 Despite advances there is always a
chance of error in endodontic therapy, and diligence in the involved procedures is necessary. 2 it
is important that the access preparation be precise Entering a tooth without an adequate radiograph is a fools errand.
3 4 Preoperative radiographs are essential because they tell us where
pulp chambers are located in relationship to coronal surfaces, and at what angles canals enter pulp chambers 5 Gaining
access to root canals, wherein the root canal instruments can be slipped easily into the canals to reach the apical portion, is the most important starting point of the root canal treatment. Before you lift that hand piece to start access cavity
preparation, stop and think about the following three points: 6 7
Have you refreshed the knowledge of the morphology and anatomy of the tooth you are going to treat? Have you taken a good look at the tooth in the oral cavity? Its shape, size, tilt and
morphology need careful consideration. Have you spent sufficient time studying the radiograph? 8
When the access preparation is cut too small, it is often impossible to find all the canals in the tooth. Even if all the canals are located, it sets the stage for negotiation difficulties, file breakage, and
unnecessary frustration during obturation procedures (Figure 1). 9 10 Conversely,
access cavities that are cut too big are a betrayal of the clinicians first admonishment to do no harm, increasing the short-term possibility of perforation and the long-term probability of tooth and root fracture.
11 CHOOSE SAFE, EFFECTIVE BURS choosing the wrong bur can presage a poor access result
burs that are too large will inevitably increase the size of the final cavity preparation as well as significantly increase the potential for tooth perforation 12
#2 round is ideal for anterior and premolar access a #4 is optimal for molar access 13
As soon as the author drops into the chamber, the round bur has accomplished its purpose and is replaced with a tapered diamond bur.
14 In anterior and premolar teeth, the convenience form is afforded by extending the preparation from buccal to lingual; the conservation
form is accomplished by preserving tooth structure in the mesial to distal dimension 15 Anterior - Triangular
16 Canines - ovoid 17 Premolar - Round
18 In posterior teeth, the line-angle extensions are cut to the working cusps and stop 1 mm to 2 mm short of the idling cusps.
19 In maxillary premolars and molars, the line angle extensions are taken to the palatal cusps (working) and
are short of the buccal cusps (idling) 20 Molar - Rhomboid 21
Conversely, in mandibular premolars and molars the line angle extensions are taken to the buccal and are short of the lingual cusps 22
23 Straight-line access Success in modern endodontic treatment may be dependent upon a
well-designed access cavity to permit straight-line access to all the main root canals 24 25
26 Flexural stress will be increased if the instrument must negotiate past an overhang; arrow A indicates overhang preventing continuous straight line access; arrow B indicates point of greatest curvature on .
outside wall of canal 27 Showing a canal opened to the apex to a No. 20 reamer or file; arrow indicates the thickest, most engaged part of NiTi, most prone to fracture
28 Questions??? 29
