Access Pulp Chamber
Begin access at the center of the occlusal surface with a #331 or #245 bur. Penetrate to the pulp chamber. Remove the entire chamber roof with a lateral and upward motion. Thoroughly clean the pulp chamber with copious irrigation, vigorous scraping (endo spoon excavator) and suction.

Locate Canal Orifices*
Locate all canal orifices with an endodontic explorer. For highly calcified canals use a small K-file to locate the orifices. Instrument all canals to about mid-root until a #10 K-file fits loosely. Do not instrument beyond mid-root. Remove pulp tissue from canals with barbed broaches.

*LightSpeed suggests loupes or microscope for enhanced visualization.

Move Mesial Canal Orifices
With Hedstrom files sizes 15, 20, and 25 (in that sequence) move (transport) the mesial canal orifices and coronal third of the mesial canal walls away from the furcation (see arrows). This helps avoid furca perforations with rotary instruments used for coronal flaring (Step 4). The mesial canal orifices and the coronal third of the mesial canal walls are moved mesially. By forcefully directing the Hedstrom blade mesially, the dentin at the orifices and walls is cut away with a pulling motion. This mesially directed filing is called "anticurvature filing" because it removes the coronal curve of mesial canals. When this curvature is removed, instruments can enter parallel to the long axis of the tooth rather than from the distal. This minimizes furca perforations and instrument separation.

Flare Coronally
The coronal 4 mm of the canal is flared and cleaned with G-G's, sizes 2, 3, 4, in that order. Rotaries are safe if the coronal curve has first been straightened with Hedstroms (Step 3). Use a light pecking motion to advance G-G's about 4 mm into the canal (blade length of #4 G-G). Using force may cause a ledge. Distal and palatal canals of molars having oval shapes coronally can be cleaned with G-G's directed back and forth, wiping and cleaning all walls of the oval.

Complete the StraightLine Access
Remove any remaining projections of the chamber roof with a long, tapered, high speed diamond, leaving smooth, continuous access walls from chamber floor to top of crown. Then, make a "path" from each mesial canal orifice to the top of the crown. Do this by:
a) placing the tip of the diamond (not rotating) into the canal orifice,
b) raising the tip just slightly above the orifice,
c) activating the hand piece and tilting the diamond vertically. Do not move the tip. Use the diamond the same way for the distal (Man.) and palatal canals (Max.) except that the diamond is tilted parallel to the coronal part of the canal rather than vertically. This completes a standard access (Fig. 5).

Modify The Access for Rotary Instruments
With all Ni-Ti rotaries, the most difficult canals to enter are the ML of Mandibular and MB of Maxillary molars. To make entry easier and reduce the possibility of a separation during instrumentation, the "path" to these difficult orifices must be modified.

Position the hand piece at each orifice as described in Step 5, (a) and (b). The modification to (c) of Step 5 entails further tilting of the long tapered diamond beyond the vertical towards the mesio- lingual line angle (see arrows). Modify the ML "path" by tilting the diamond until the hand piece can be withdrawn without hitting the upper teeth. For the MB "path" tilt the diamond until the hand piece can be withdrawn without hitting the lower teeth. These new "paths" make for better StraightLine™ access.