Endodontic treatment of an upper first molar: materials, methods, and clinical challenges

By Richard E. Mounce, DDSThe patient pictured in Fig. 1 presented with severe spontaneous pain and sensitivity to cold in the upper right. The patient had seen his general dentist in order to localize the pain without success. The patient reported extreme discomfort of several weeks’ duration to cold that lingered for minutes to hours. Upon examination, tooth No. 3 provided the most extreme and sharp reaction to cold that, at first, abated completely. Minutes later, the pain became acute and centered over No. 3. Tooth No. 4 had no response to cold. Tooth No. 2 was within normal limits.

Figs. 2-3: The postoperative views of No. 3.

Fig. 5: Small apical assorted (25/.08/23 mm, 30/.06/23 mm, 35/.06/23 mm) (SybronEndo, Orange, Calif.). All of the teeth on the upper right were within normal limits to percussion, palpation, mobility, and probings. The area buccal to No. 3 was anesthetized with local anesthetic in order to confirm the diagnosis of irreversible pulpitis with the recurrence of discomfort. The pain resolved immediately once anesthetic was injected locally. No. 3 was diagnosed with irreversible pulpitis and consent for treatment obtained from the patient. This article details the clinical endodontic management of No. 3. Specifically, it details the anticipated and actual clinical challenges as well as the materials and methods used. The risk factors associated with endodontic treatment of No. 3 were assessed before starting treatment. These risk factors include:

1. The canals were moderately calcified.
2. The apical half of the mesial buccal root was severely curved.
3. The metal foundation of the crown obscured the pulp chamber.
4. The crown’s porcelain was at risk of fracture during access procedures.
5. The apex of the palatal root appeared to have periapical pathology that was inconsistent with the finding of extreme cold sensitivity. The palatal root appeared straight and relatively uncomplicated.
6. Given that this is an upper first molar, it was expected to find an MB2 canal in the mesial buccal root.

The above findings provided the following challenges:

1. The calcification present in all roots required significant time with hand K files to negotiate before rotary nickel titanium (RNT) files should be inserted.
2. The mesial buccal root apex was especially susceptible for (RNT) file fracture due to its curvature and calcification.
3. With the pulp chamber obscured, the risk of furcal perforation was high if the access was taken too far apically.
4. Access through the crown required copious water and ultrafine diamonds to prevent fracture of the porcelain.
5. The palatal root, if not carefully explored with regard to its length, could easily lead to overinstrumentation with a RNT file if inserted too rapidly without regard for the position of the minor constriction of the apical foramen (MC).

Additional clinical considerations

Additional preoperative clinical considerations to be addressed before access included the expected master apical taper and master apical diameter. The prepared master apical taper is a function of the anatomy as well as the RNT system being utilized. For RNT files that are manufactured by a grinding process and especially those with radial lands, the master apical taper is likely to be .06 along the length of the canal. For RNT files manufactured by a twisting process such as the Twisted File (SybronEndo, Orange, Calif.), it is both efficient and predictable to prepare a .08 taper in the mesial buccal (MB) and distal buccal (DB) canal and .10 taper in the palatal canal. Given that this tooth is vital yet irreversibly inflamed, the master apical diameter anticipated was approximately a #40 ISO tip size. How this master apical diameter was prepared is detailed below.

Clinical management

1. Before starting, an estimate of the true working length was determined from the initial radiographs.
2. After profound anesthesia, under the rubber dam and surgical operating microscope (SOM) (Global Surgical, St. Louis, Mo.), access was made with copious water spray. An alternative to the SOM would have been the use of HiRes 4.8X Class IV Orascoptic loupes with a light source (Orascoptic, Middleton, Wisc.). In any event, whether provided by loupes or the SOM, the value of lighting and magnification in access and subsequent treatment cannot be overstated.
3. The porcelain of the crown did not fracture using ultrafine diamonds. Once the pulp chamber was reached through the crown, a diligent effort was made to expose the various canal orifices and to provide straight-line access. The cervical dentinal triangles of the mesial buccal, distal buccal, and palatal canal were removed using TF (.10/25 for the palatal and .08/25 TF for the buccal roots) in a brushing motion up and away from the furcation.
4. TF was used to shape the coronal third of the three roots. After coronal third shaping, the MB, DB, and palatal roots were explored with a #8 hand K file and apical patency was assured. Once the #8 hand K file reached the estimated working length, an electronic apex locator determined the position of the true working length (TWL). A glide path for TF was prepared using the M4 Safety^® Handpiece (SybronEndo, Orange, Calif.) to reciprocate hand K files to the diameter of a #15 hand K file.
5. The roots were instrumented crown down with the .08/25 TF to prepare a .08 master apical taper followed by a #40 master apical diameter. The sequence in all canals was virtually identical; a .08/25 was inserted to the TWL in approximately four insertions followed by a .06/30/35 TF and .04/40 TF, each inserted once. The smaller taper of the .04 and .06 TF fit easily and predictably to TWL in each canal. The .06/30/35 TF and .04/40 TF files cut only on their tips at the apex. Working length was confirmed with electronic measurements once the first TF (.08/25) and last TF reached the TWL.
6. The MB orifice was immediately visible upon access slightly off to the mesial of a straight line between the MB orifice and the palatal orifice. The first file into the MB2 canal was the #6 hand K file inserted with gentle pressure. This #6, as were all hand K files, was precurved with an Endo-Bender^® (SybronEndo, Orange, Calif.). The #6 initially made slight progress down the MB2. The file was withdrawn, the orifice irrigated, and another precurved #6 inserted. A repetition of this action allowed a #6 hand K file to reach the apex with several insertions. Next, a #8 hand K file was inserted into the MB2 and reciprocated, followed by a #10 hand K file until both spun freely. An electronic determination of TWL was obtained in the MB2 once the #10 hand K file reached the estimated working length. The MB1 and MB2 merged at mid-root. The MB2 was enlarged to a .08 taper with a .08/25 TF and its master apical diameter confirmed to a #40.

Obturation was carried out using a .06/20 RealSeal master cone using RealSeal sealer with the Elements Obturation Unit^™ and SystemB technique (SybronEndo, Orange, Calif.). A RealSeal One Bonded Obturator could have been used in lieu of using RealSeal master cones. Using a master cone or obturator of RealSeal is a matter of personal preference — either can create a bonded obturation. A .06/20 master cone was custom fit to match the size #40 apical preparation. 3 mm was trimmed from the .06/20 RealSeal master cone to achieve tugback of the master cone at the TWL. 3 mm from the tip of a .06/20 master cone, the diameter is approximately a #38 (.38 mm). It is noteworthy that a small sealer puff is present at the apex of the three roots as a result of the SystemB technique. Such a puff is expected if patency is maintained with ideal cone fit and the correct hydraulic forces are placed upon the master cone during the SystemB downpack. No. 4 was subsequently treated with a nonvital diagnosis. The resulting obturation shows the same sealer puffs as No. 3. A clinically relevant discussion of the endodontic management of an upper first molar has been presented. Emphasis has been placed on achievement and maintenance of canal patency, prevention of iatrogenic events, and trimming master cones to fit the master apical diameter.I welcome your feedback.

Richard E. Mounce, DDS, is the author of the nonfiction book “Dead Stuck” — “one man's stories of adventure, parenting, and marriage told without heaping platitudes of political correctness.” Pacific Sky Publishing. DeadStuck.com. Dr. Mounce lectures globally and is widely published. He is in private practice in endodontics in Vancouver, Wash. Contact him at [email protected].