ENDODONTIC ACCESS CAVITY

1.Why are access cavity preparations different from typical operative occlusal preparations?

The operative occlusal cavity preparations are based on the topography of the occlusal grooves, pits and fissures avoiding the underlying pulp. Whereas access cavities are designed to cover the pulp chamber fully, providing a straight line access to the pulp. If access preparations are restricted, then a direct access to the canal is not achieved, there is incomplete removal of the debris, insufficient dentinal wall preparation, failure to detect additional canals and improper condensation of obturating material.

 

2. When rotary endodontic instruments are used, why excess removal of coronal root dentin is not encouraged?

This is because, excess removal of coronal root dentin weakens the root walls, lateral or strip perforation can occur and the GP though well compacted, will not strengthen the root. Placement of a post also will not strengthen the root instead may lead to root fracture.

 

3. In a class III cavity with a carious exposure, why is the access not taken through the exposure?

In a class III cavity with a carious exposure, access to the pulp canal is not taken through the exposure. The caries is excavated and an interim restoration is placed and a straight line access is taken from the palatal surface of the tooth. This allows for completely involving the pulp chamber and a straight line entry to the canal space. Also the instruments are not bent and they take a straight pathway to the canal thereby preventing fracture.

 

4. Why is an access cavity preparation needed?

An access is prepared to create a smooth straight line path to the canal system and the apex. When it is correctly done, it allows for complete irrigation, proper shaping and obturation. Diagnostic radiographs help to estimate the pulp chamber position, calcifications in the chamber, canal length etc. which assist for gaining access into the pulp chamber.

 

5. What are the factors that determine the successful outcome of the endodontic treatment?

• Proper cleaning and shaping of the canal
• Disinfection
• Three dimensional obturation of the root canal system
• Above all is the preparation of a proper access cavity

 

6. Why is thorough cleansing of the endodontic space important for a favorable outcome?

Proper cleansing of the endodontic space includes cleaning the root canal as well as the pulp chamber and the pulp horns. The pulp chamber roof is completely removed which allows removal of all the pulp tissue, calcifications, all residues or traces of old filling material. If the roof of the chamber is not removed, the contents may not be removed fully which may lead to contamination or infection of the endodontic space or discoloration of the endo treated tooth.

 

7. How are endodontic probes useful in access preparation?

Endodontic probes help for the inspection and localization of canal openings. The probe explores the chamber floor and enters the canal openings displacing the calcific deposits obstructing them. They can also determine the angle between the root canals and the floor of the pulp chamber.

 

8. Why should the access cavity be wide enough to permit the entry of the endo instruments?

This is because, a narrow access cavity allows working on only one wall of the canal and the other wall remains untouched, which may lead to deformations of the apical foramen. Also the friction of the instrument shaft against the coronal obstruction has to be overcome since the force required to do so impairs the ability to sense how much working portion of the instrument is engaged against the walls and this will lead to instrument fracture.

 

9. How is the shape of the access cavity determined?

The shape of the access cavity should correspond to a slightly enlarged projection of the contour of the pulp chamber floor onto the occlusal surface of the tooth.

 

10. Why is it necessary to have all four walls of the access cavity?

The four walls of the access cavity allow:

• Correct positioning of the rubber dam
• Constant flooding of the pulp chamber with the irrigating solutions
• Reproduction of stable reference points for the rubber stops on the instruments.
• Placement of temporary medication without affecting the adjacent tissues

 

11. Why does an access cavity not take a predetermined shape?

The shape of the access cavity is determined mainly by the anatomy of the pulp chamber so that good cleaning and shaping, disinfection and complete sealing are achieved without any hindrances.

 

12. Why the access cavity is always prepared through the occlusal or the lingual surface?

It is so because, an approach other than the occlusal or the lingual would cause significant bending of the instruments which in turn results in inadequate cleaning and shaping of the canals and deformation of the apical foramen.

 

13. How is the penetration phase important in the access preparation?

The penetration phase is the one in which the pulp chamber is entered by breaking the roof of the chamber with a bur. It creates a funnel shaped opening towards the outer surface for better visibility and orientation.

 

14. What is the role of the enlargement phase in access preparation?

The penetration into the pulp chamber is enlarged in this phase in which the bur works on the dentinal walls with a brushing motion and removes all the overhangs of the dentin left behind in the preceding phase. A definitive form of the cavity begins to emerge at this phase.

 

15. How is the prepared access cavity finished?

Finishing the prepared access cavity is done with a non end cutting diamond bur to smoothen the walls of the access cavity so that the transition between the access cavity and the pulp chamber walls will be imperceptible to probing. Also the same bur is used for giving a slight flare to the access cavity in the most occlusal portion.

16. What is the difference between the access shapes of a central and lateral incisor?

The access cavity of central incisor is roughly triangular in shape whereas that of the lateral is ovoid because the lateral incisor has two closely situated pulp horns or a single central horn.

 

17. What are the pretreatments required for a tooth before beginning for endodontic therapy?

Pre endodontic management includes removal of all carious tissue, inadequate restorations and restoring the contacts and contours.