OPTION 3

EXPLANATION:

• The extension of an access cavity into the coronal-most portion of the root canal has been called “coronal flaring” but may be more appropriately described as orifice modification.
• If a canal is constricted, mineralized, or difficult to access, directed enlargement of the coronal portion prior to any deep entry into the root canal is beneficial.
• This canal modification should be preceded by a scouting step, in which a small (e.g., size #10) K-file is passively placed several millimeters into the root canal. Tools for preflaring include Gates-Glidden and dedicated NiTi instruments.
• Greater volumes of irrigants can reach in canal irregularities in early stages of canal preparation because of coronal flaring
• Diagram of coronal enlargement in a more complicated maxillary posterior tooth. This maxillary molar presents several difficulties, including a narrow mesiobuccal canal that exits the pulp cavity at an angle. A possible approach in a case involving difficult entry into the root canal system is to use a small orifice shaper (OS1) after ensuring a coronal glide path with a K-file. Use of a sequence of orifice shapers (OS3 to OS1) then allows penetration into the middle third of the root canal. Wider canals can accept a second sequence of orifice shapers. Copious irrigation and securing a glide path with a size #10 K- file are prerequisites for use of NiTi rotary instruments.

1. The use of laterally cutting NiTi rotaries allows clinicians to modify the root canal orifice to form a receptacle for subsequent instrumentation.
2. This is related to removal of coronal mineralization and to relocation of the canal pathway by removal of restrictive dentin.
3. Pre-enlargement of the coronal portion of a root canal allows files unimpeded access to the apical one third and gives the clinician better tactile control in directing small, adequately precurved negotiating files.
4. One of the purported benefits of orifice modification is early access of disinfecting irrigation solutions and prevention of pushing contaminated coronal debris apically.
5. On the other hand, a documented benefit of coronal flaring is mitigation of WL changes during canal preparation.

Key Concept:

• Coronal flaring should always be done as the first step of canal preparation.
• Nevertheless, the following should be considered when planning the extent of the coronal flaring
• A wide orifice facilitates easy insertion of instruments and irrigants and allows large amounts of irrigant to be introduced into the endodontic space.
• A wide and deeply flared root canal reduces friction of the instruments and thereby reduces the risk of instrument fracture. Reduced friction allows for better control of the instrument, improves tactility, and allows more precise manipulations of the files in the apical part of the root canal.
• If an instrument has too much coronal friction, it is difficult or even impossible to direct it apically, as the friction will dictate the extent and direction of the apical preparation.
• Flaring outside of the curvature can reduce the degree of the curvature and facilitate further preparation of the middle and apical thirds of the canal.