The importance of endodontic access in locating maxillary and mandibular molar canals.

The principle of straight-line access is discussed with particular reference to endodontic access of either maxillary or mandibular molar teeth. Modifications to the traditional triangular access opening are described that will make it easier for a practitioner to locate and instrument the fourth canal system commonly found in molar teeth. The high frequency of a fourth canal in molar teeth makes it essential to anticipate and find all canals during molar endodontic therapy. Quite frequently, the general practitioner attempting molar endodontic therapy should expect to locate a second canal in the mesiobuccal root of the maxillary molar and a second canal in the distal root of a mandibular molar. The possibility of extra roots over and above the norm should also be anticipated and looked for carefully. Proper angulation and interpretation of radiographs help to identify chamber and root anatomy. A two-step access opening is advocated when making access openings on molar teeth if a coronal crack in the crown is to be seen early in treatment. A method of unroofing the pulp chamber and pre-flaring the canal orifice to facilitate the subsequent shaping of the entire root-canal system is described. Clinical and laboratory examples are pictured to illustrate modifications or errors in the standard endodontic access opening.