1] The access cavity should enable root canal instruments to be introduced into the canals to their apical constriction without undue bending and binding coronally.
2] The access cavity must be large enough to allow complete debridement of the pulp chamber otherwise it may lead to reinfection or crown discolouration.
The roof of the pulp chamber must be removed completely.If not removed completely, access to canals is difficult.Also, infected and necrotic material will be retained within the pulp chamber which may then be transferred to root canals through instumentation. Breakdown products from such remnants may responsible for the subsequent discolouration of the crown.
3] In multirooted teeth great care must be taken not to damage the floor of the pulp chamber.Not only is there a possibility of perforation but the contour of the floor is such that the openings to the root canal tend to be funnel shaped. If this natural anatomy is destroyed, subsequent instrumentation is more difficult.
4] The access cavity should funnel into the canal orifices.In multirooted teeth the orifice of the root canals should be at the periphery of the base of the access cavity so that instruments may be slipped down the walls of the cavity and into the root canal.
5] The occlusal projection of the access cavity should be larger than the base, to allow better visualization of the floor of the pulp chamber, especially if an operating microscope is used.
6] As part of the access preparation, the unsupported cusps of posterior teeth must be reduced by trimming with a tapered fissure carbide or diamond stone until a definite clearance in occlusal and lateral movement is obtained.
7] The objective of entry is to give direct access to the apical foramina, not merely to the canal orifice.
8] The likely interior anatomy of the tooth under treatment must be determined.Each tooth has a typical length no. and configuration of roots and canals. Prior to starting of the access, radiographs taken from atleast 2 different angles must be studied, knowing what combinations of interior anatomy are possible and having the information given by radiograph, the operators will be able to ascertain with great accuracy the canal system present in the tooth to be treated and the possible alternative configurations. This information gained prior to initiation of preparation will greatly facilitate the entry as well as urther treatment.
Welcome to my blog....I am Dr Pratibha Singh and I am trying to create awareness in people so that people can have healthy and beautiful smile.Smile improves our face value and giving that wonderful smile is our[dental] profession.So keep reading and updated.