In the Glossary of Endodontic Terms (7th edition, 2003) published by the American Association of Endodontists, the term “perforation” is defined as: “the mechanical or pathologic communication between the root canal system and the external tooth surface”.1 Within this explanation there is an almost endless list of clinical situations where this aberrant “communication” can lead to root canal treatment, retreatment, corrective surgery and/ or extraction. Considering the technical advances in dentistry over the past 20 years, and specifically in the discipline of endodontics, dissembling complex restorations, creating barriers, and sealing these communications is now a treatment option with some degree of predictability.
Pathologic situations (such as root resorption) aside, the mechanical or iatrogenic perforation is a procedural mishap that can wreak havoc on any dentist who performs endodontic treatment. From the inexperienced, recently-graduated dentist who simply encounters a calcified pulp chamber and has no traditional textbook “landmarks” to guide him/ her to canal orifices, to the well seasoned endodontist who may perforate the canal wall in the apical third in the course of freeing up a separated rotary file, the more difficult that a case may be, the higher the incidence that problems may occur.
Tackling the problem is easier if it is broken down into component parts: the patient, the canal system, and the perforation. Patient management includes informed consent about what happened and advising about the treatment options. Perhaps referral to a specialist would be in the best interest of the patient. Perhaps the patient may prefer to have the tooth extracted, and plan for a prosthetic replacement (Fig. 1).
In the most general terms, the more rapidly a perforation can be sealed, the better. Ideally, if treatment is performed under a surgical microscope and a rubber dam, and all of the needed repair materials are available, it has value to correct the defect at the same appointment. Alternatively, if this is not the case as outlined below, the overriding key value to the patient and clinician to promote healing is to keep bacteria from contaminating the perforation to the greatest extent possible from the time of occurrence to the time of the repair. Coronal seal between visits is critical.
The canal system, the inflamed or necrotic pulp which was the reason why the tooth was entered, still needs to be addressed. Depending on the case, it may be more efficient to wall off the perforation with a barrier material, and then finish the endodontic therapy… leaving the handling of the perforation as the final step in that one appointment. In other cases, it may be best to complete the pulpectomy, place a dressing of calcium hydroxide in the canal system, and then deal with the perforation as the priority. At a second visit, the endodontic therapy can be completed.
The advent of recent materials has facilitated treatment of perforations to a significant degree. Synthetic collagen wound dressing, such as Neocote (Citagenix Inc. Lava, QC) (Fig. 2), allow walling off the perforation site, and provide a matrix to pack the final restorative material against. The root repair material, Mineral Trioxide Aggregate (ProRoot) (Fig. 3) has been shown in numerous studies to allow significantly less leakage, better adaptation to root canal walls, less bacterial migration2-5 and formation of new cementum over the restored root interface.6 First developed as a grey cement material, a white, tooth coloured MTA has been developed for use in anterior teeth where aesthetics may be a concern (Fig. 4). The powder component mixes with sterile water, and there is an initial set at approximately five minutes. Complete setting is reported to be over a four to eight hour period. Placement of the MTA into a specific site has been made easier with the development of Dovgan MTA carriers (Quality Aspirators, Duncanville, TX) (Fig. 5), available in three different diameters, and one being “bendable” to adapt to fit into the furcation or down a canal space.
The most common locations where perforations occur are through the exterior root wall during access, the furcation floor in molars when searching for a canal orifice, progressing straight through a curved root once in the canal, and enlarging the canal to create a post space resulting in a “strip”perforation.
ACCESS
During access into a tooth with a narrow mesial-to-distal direction, the bur can be directed slightly off line and though the exterior root wall (Fig. 6). In a case like this, the perforation can be walled off with a barrier, and access can be corrected. The canal system can then be treated in the usual manner, with placement of Neocote into the perforation site and sealing with MTA at the end of treatment. The MTA will set by the time the patient returns for the permanent restorative appointment.
FURCATION
Looking for a canal orifice on the chamber floor of molars can lead to perforations into the furcation area. Once the canal systems have been treated, the final step is placing the barrier for a matrix, and sealing with root repair material (Figs. 7 & 8). In some particular cases, it may be better to locate the canals and place calcium hydroxide to get the endodontic component under control. The perforation site can then be cleaned, packed with Neocote to form a matrix, and then sealed off with MTA (Fig. 9). At the next appointment, the MTA is permanently set, and the endodontic therapy can be completed without risk of washing out of the MTA.
MISSING THE CURVE
With the advent of engine driven files, more rapidly completed treatment can be a positive. However, with speed comes an increase risk of problems. An instrument progressing straight where the canal curves can result in contact with the root wall, the ligament and the apical or radicular bone (Fig. 10). The use of the Dovgan carrier is most advantageous in a case like this, where access half way up the root requires very narrow diameter instruments and precision placement. Because the MTA material is easily washed out until it has set, sealing the perforation would be the priority in the first appointment. Endodontic therapy would be completed at the second appointment.
STRIPPING THE WALLS
Overzealous coronal shaping or post space preparation can lead to what is called a “strip” perforation. Recalling root anatomy, in cross sectional view there is often a subtle concavity to the distal root on the mesial (furcation) side. Coronal flaring can encroach upon this concave surface. Widening the space for a post space can cause the same result. Suddenly, hemorrhage can be found in the canal space! Using the same strategic approach, under medium to high power magnification, a soft compressible barrier can be placed into the defect (Neocote). The canal treatment can be carried out, with obturation finishing just apical to the defect. After replacing the barrier with fresh Neocote, the MTA can be placed to obturated the coronal third of the canal — including the perforation site — right up to the chamber floor. In Figures 11 & 12, four different cases are shown with this kind of repair and healing.
Utilizing a repair material with greater clinical and histological success than ever before, coupled with magnification, fibre optic illumination, and the use of precision instruments for placement, the bar has been raised on what can be treated and restored to full function in a patient’s natural dentition.
Dr. Steven Cohen is an endodontist on staff at Sunnybrook Hospital Dental Clinic and clinical instructor in the graduate programme of Endodontics at the University of Toronto. He maintains a private practice limited to endodontics in Mississauga, ON, Canada.
Dr. Gary Glassman is a Fellow and Endodontic Examiner for the Royal College of Dentists of Canada, Associate in Dentistry at the University of Toronto, and Endodontic Consultant fo
r Oral Health Dental Journal. He lectures internationally and maintains a private practice limited to endodontics in Toronto, ON, Canada.
Dr. Richard Mounce is in full time private practice in Portland, Oregon, USA. He lectures globally and is widely published.
Oral Health welcomes this original article.
REFERENCES
1.American Association of Endodontists. Glossary of Endodontic Terms, Seventh Edition, 2003.
2.Torabinejad M, Watson TF, Pitt Ford TR. The sealing ability of a mineral trioxide aggregate as a retrograde root filling material. J Endodontics 1993; 19; 591-5.
3.Lee SJ, Monsef M, Torabinejad M. Sealing ability of a mineral trioxide aggregate for repair of lateral root perforations. J Endodontics 1993; 19; 541-544.
4.Torabinejad M, Smith PW, Kettering JD, Pitt Ford TR. Comparative investigation of marginal adaptation of mineral trioxide aggregate and other commonly used root-end filling material. J Endodontics 1995; 21; 295-299.
5.Fischer EJ, Arens DE, Miller CH. Bacterial leakage of mineral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and super EBA as a root end filling material. J Endodontics 1998; 24; 176-9.
6.Torabinejad M, Pitt Ford TR, McKendry DJ. Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys. J Endodontics 1997; 23; 225-8.
