Maintaining a "dry field"

Dr. Peter G. Delaney describes how proper endodontic isolation using pins will save time, money, and unnecessary stress

Proper endodontic treatment can be challenging enough without encountering isolation problems. With a standard case, isolation is usually not an issue, but with gross decay or a tooth that has already been prepped for a crown, it can be. The case study examined in this article is a tooth that has been prepped for a crown at the ideal 8-10–degree angle of convergence and requires root canal treatment (RCT). Every experienced clinician has encountered a number of these teeth and has struggled with various ways to isolate them.

One option is to refer the patient to a periodontist for an expensive and uncomfortable crown lengthening. This would allow the clinician to get below the convergence angle and obtain isolation with a rubber dam and retainer. Sometimes this is necessary if the biological width is compromised by secondary decay. If the biological width is not compromised, this procedure can be avoided.

A second option is to bond composite filling material to the tooth to create artificial undercuts. This seems to work most of the time, until a working length periapical radiograph is taken or the patient swallows, and his/her tongue engages the retainer from underneath the rubber dam, sending the retainer flying across the room and forcing you to keep the patients’ saliva from compromising the filling material.

A third, and least desirable option, is to engage the patient’s attached gingiva with the retainer. Not only is this uncomfortable for the patient when the anesthesia wears off, but also a “flying” or “sliding” rubber dam retainer is possible. Every practitioner has cringed while watching the attached gingiva tear off, a truly horrible feeling.

The fourth option, which is explained in detail below, is using dental retention pins (Coltene Whaledent). Placed vertically in the cavity preps, the pins are a very useful tool to gain added retention of filling material. By placing them horizontally into a crown-prepped tooth, a perfect artificial undercut is obtained. Four properly placed pins will not “pop off,” will not harm the soft tissue, and will not result in patient discomfort.

Case study

A 90-year-old man presented with the chief complaint of pain when biting on the lower left side. X-rays and examination reveal gross secondary decay under the crown on tooth No. 19. The old crown was removed, as was any and all present decay. There was no visible sign of pulpal exposure, thus a temporary crown was placed for an evaluation phase. After 3 weeks, the symptomology worsened, and it was determined the tooth had irreversible puplitis, and RCT was started. After administering local anesthesia and removing the crown, isolation was accomplished by placing two horizontal pins buccally and two horizontal pins lingually. A 56A retainer was placed over the pins, creating an artificial undercut to keep the retainer in place. (If necessary, the Minim™ [Coltene Whaledent] bending tool can be used to bend the pins in an apical direction to ensure an undercut is achieved.)

The RCT then was completed in a perfectly dry field. After completion, the pins were cut off flush with the crown-prepared tooth. The tooth then was restored with a post-and-core and final crown.

Concluding thoughts

The goal is that this technique will save time and unnecessary stress when isolating a crown-prepped tooth or one with gross decay. This procedure will save your patients time, unwanted discomfort, and financial distress. For the significant number of patients who desire nonmetal material in their mouths, reaming the remaining portion of the pin from the tooth and filling the void with composite resin material will yield the desired result.

Bio: Peter G. Delaney, DMD, is a general practitioner in West Hartford, Connecticut, and was voted by his peers as one of Connecticut’s Best Dentists every year from 2009 to 2011 in CT Magazine. Contact, This e-mail address is being protected from spambots. You need JavaScript enabled to view it for questions, or visit http://www.west-hartford-dentists.com