LOCATING CANALS

Maxillary molars have a mesiobuccal (MB) root that usually contains two root canal systems which oftentimes communicate anatomically along their respective lengths. Histological research has shown the MB root holds a second MB2 canal approaching 100% of the time. Clinically, the MB2 root canal system can be identified and treated in approximately 75% of the cases without a microscope and in over 90% of the cases with a microscope. The MB2 system lies mesial to an imaginary line between the MB1 and palatal orifices. Access cavities need to be expanded laterally at the expense of the Mesial Marginal Ridge (MMR), rather than chasing deep at the expense of the pulpal floor, to facilitate identification and treatment. The maxillary 2nd molar should be suspected of having a second canal in the MB root until proven otherwise. Importantly, research shows that the MB1 and MB2 terminate separately in two or more foramina about 60% of the time.

Mandibular Molars routinely have significant variations within what has become known as "normal anatomy". Clinicians need to check the mesial root for a third system which may be displaced or located within the groove between the MB and mesiolingual (ML) orifices. The broad distal root commonly contains an extra canal which may be separate along its length or become contiguous following cleaning and shaping procedures. Importantly, even when the distobuccal (DB) and distolingual (DL) systems are common, deep divisions should be expected and post treatment films routinely demonstrate multiple apical portals of exit.

Piezoelectric ultrasonics in conjunction with the ProUltra ultrasonic instruments (Dentsply Tulsa Dental) provide a breakthrough in exploring for and identifying calcified, aberrant or previously missed canals. Ultrasonic systems importantly eliminate the bulky head of the conventional handpiece which notoriously blocks light and obstructs vision. Ultrasonic instruments are used with a light touch in a brush-cutting manner to progressively sand away precise amounts of dentin. Microscopes and ultrasonic instruments have led to microsonic techniques that have significantly improved vision, control and safety when searching for difficult to find canals.

Specifically, the abrasively coated SINE tips or the ENDO-2 or 3 are the ultrasonic instruments of choice for troughing along grooves such as between the MB1 and MB2 orifices. Traditionally, clinicians have searched for the MB2 system within the groove off the MB1 orifice when in fact the MB2 is mesial to this groove, under the shelf of overlying dentin. This lip of dentin can be safely sanded away and easily eliminated with ultrasonic energy. Ultrasonic instruments can also be used to chase calcified canals that are receded and have pulled down and away from the pulpal floor. Further, the tip of an ultrasonic instrument may be used to vibrate and disintegrate a pulpal stone and is safer and more efficient than drilling or trying to remove them with spoons or excavators. For additional information, I also refer you to the Ruddle on Shape•Clean•Pack DVD and/or the Ruddle on Retreatment DVD "Disassembly & Missed Canals" as each have sections that clearly show a number of methods for finding canals.

The microscope enhances diagnostics by providing the vision to observe both texture and color. Vital cases bleed and at times blood can be visualized as a small droplet above an orifice or a "red line" within a groove that emanates off an orifice / system. Additionally, a spot of blood on the side of a paper point that is placed within a shaped canal may suggest a lateral canal or the entrance to a deeply branching system. Conversely, in necrotic cases, a "white line" can be visualized as the clinician troughs along a groove. As an example, following a white line off the MB1 system towards the palatal oftentimes leads to the MB2 orifice / canal system. Yellowish, brown lines of varying widths are frequently observed on the pulpal floor of furcated teeth. It should be appreciated that these colored lines map and reveal the position of the various orifices. These anatomical color distinctions provide valuable information and when followed, typically lead to a sought after orifice and related root canal system.

Color is also a critical indicator when chasing a receded or calcified canal. Typically, a small dark brown dot is visualized and represents the position where the canal used to be. Chasing apically along this colored route typically leads to a more open canal that can be negotiated.