| Contents | Previous | Next |
The most challenging aspect of endodontics for the immediate future is the canal filling material to be utilized. This subject has taken up a huge amount of space in the endodontic journals of the past few years and shows no signs of subsiding.
Gutta-percha, the trans isomer of polyisoprene, has dominated the canal filling scene for well over 100 years and the results obtained, in combination with exacting canal preparation efforts, have been quite positive. Gutta-percha itself has been around for a long time. It was used in the 18th century as a component of golf balls and was used for many years in the manufacture of chewing gum. The cis isomer has been used in many rubber products, such as tires, rubber gloves, and other similar products. It has many desirable qualities as a canal filling material, including nonsupport of bacteria and substrate, compactibility into the canal, and has been used in several different forms in endodontics. These include packing of room-temperature gutta-percha, insertion of warmed injection-molded gutta-percha, and filling in conjunction with such solvents as chloroform, eucalyptol, and xylene. Its few disadvantages are its lack of rigidity to be placed deeply into curved canals and lack of length control(60).
Another mild problem is that gutta-percha for use in endodontics is naturally occurring, coming from the sap of the Indian rubber tree and, for many years, was taken from trees in the Malaysian peninsula. Because the use of rubber products has been more significant than the uses of gutta-percha, the preponderance of the yields has been away from the dental use. For the last 10 years, or so, the product has been taken from trees in the western region of Brazil where the temperatures and humidity are similar to those in Malaysia.
Despite the excellent results that it has delivered for many years in many, many cases, periodically there have been efforts to replace it with other materials. In l941 Jasper introduced silver wires or points(61). This material could be placed into canals with curvatures and had good length control, the two deficiencies associated with gutta-percha. However, there were also some problems. If the point was overextended and entered the periapical tissue, the extended portion could become corroded because of the silver content. Perhaps even more importantly, the ease of insertion led many dentists to minimize the critical factor in gaining endodontic success by failing to clean the canal properly, leaving behind bacteria and substrates. Also, the silver wires were strongly radiopaque and would give the illusion on the post-operative radiograph of a density that was deceivingly good. After a brief period of expanded use, silver points gradually went out of favor and gutta-percha was back in vogue.
Now efforts to replace gutta-percha are gaining advocates and a new product has reached the market recently as a replacement. Called Resilon, it is a synthetic, semi-crystalline aliphatic polyester named polycaprolactone which has been approved by the FDA for use in several areas of medicine and dentistry. Because it is synthetic, the material may be produced in the laboratory in accordance with the determined volume needed rather than in far away areas which require specialized delivery systems to the manufacturer.
The initial studies were published by Trope and his colleagues at the University of North Carolina(62,63). These studies usually included a specific sealer, Epiphany Primer (Pentron Clinical Technologies) and the combination of the two were reportedly responsible for a stronger root structure after canal filling. In an in vitro study, Torabinejad, et al.(64) reported 50 percent penetration along the entire canal 30 days after filling using gutta-percha and a sealer other than Epiphany. In their articles, Shipper and Trope(64,65) seem to suggest that following canal filling with presently accepted procedures, bacteria are able to infiltrate the root and potentially may be responsible for treatment failure. Ray and Trope(66) have suggested that the quality of the restoration following endodontic treatment may have more to do with treatment success than the canal filling procedure. They further recommended that resins be used for better sealing of the canal.
These statements have been accepted by a significant number of endodontists. I have particular problems with much of the data. First of all, Trope has a financial interest in Resilon and although he has been a highly recognized researcher for many years, his results are subject to question. A spate of papers and programs endorsed the Resilon material, several suggesting the use of other resin products, including resin posts for the restoration. Then Tay, originally from the University of Hong Kong, and his cohorts, at the Medical College of Georgia and the group that he developed there, undertook a number of studies( 67-70) that cast considerable doubt about the efficacy of the materials. The group in Georgia included David Pashley, who has authored or co-authored a slew of excellent papers investigating endodontic interests, including initial studies on the smear layer and the effectiveness of apical seal. For the most part, these articles did not agree with the Trope studies. The assertion concerning the claim of increased root strength has been essentially discarded.
Obviously the jury is still out on the subject of whether or not Resilon/Epiphany will replace gutta-percha as the dominant filling material used. However, it appears that the ice-jam of reliance on the old favorite probably has been broken and other synthetic materials will be investigated very soon. In my opinion, these newer and, perhaps, better substitutes will require intensive investigation before gutta-percha use is discontinued. Furthermore, it is hoped that the newer materials, yet unknown, will be reported upon by investigators without financial interest to eliminate any chance of personal bias.
Another subject that should be investigated is the proper place of one-sitting treatment. Such therapy is far from recent, with an article on the subject by Kells published in Dental Cosmos in 1887(71). Certainly the practice is very frequent among a number of dentists and it is my contention that it occurs very close to 50 per cent of the time, thus with virtually an even distribution as compared to multiple-appointment therapy. There can be no question that there are times when any practitioner leans heavily toward single-visit treatment, as when a patient suffers a clean horizontal break of a maxillary anterior tooth with minimal exposure of the pulp and no history of pain prior to the incident. By the same token, treating a tooth endodontically in a single visit when the tooth has been left open for a long period without having more than minimal canal preparation would seem to be asking for a serious exacerbation, if attempted. Even prescribing strong antibiotics probably would not offer sufficient coverage to prevent an undesirable response. The greater problem here is that endodontists have found that limiting cases to one appointment can be very remunerative, even if they decrease the total fee for the service, which few have done. Because the tooth need not be opened and then subsequently reopened to complete, the total office time is significantly decreased(72).
What is needed is a wide-ranging study of a large number of patients with efforts made to clarify the problems of single-visit treatment. Also, a clear definition of single-visit treatment must be made. Some dentists have patients in for a preliminary visit but, except for those in pain, only radiographs and an evaluation of the patient’s problem take place. The patient then is rescheduled for a future time when the tooth can be completely treated. Thus, it may take two scheduled appointments to treat a single tooth.
I know that in my own experience it is rare that I can locate and prepare the fourth canal in a maxillary molar, if present, in a reasonable appointment time (1 ½ hour or less). Merely attempting to locate it, even with magnification, may take 30 minutes or more. Mandibular first bicuspids with two canals may also be time consuming. It is my opinion that extending the appointment time (to 3 hours, for example) is counterproductive as patients do not like the very long time of keeping their mouths open with the rubber dam in place.
Even though I rarely finish a tooth in one appointment, I readily agree that there are some cases, perhaps many, when the tooth may be treated safely in a single visit. Most older studies on the subject have endorsed single-visit treatment(73-75), but most of them were reported by dentists who prefer that method of treatment. Many older articles discussing the subject from both sides of the controversy have been poorly designed and only were listing of cases that enforced the author’s position. A more recent report by Holland et al. (76) was carefully planned, but healing in dog’s teeth is much superior to that in humans.
Recently, there have been several interesting reports dealing with this situation. Many have implicated failure to successfully remove microorganisms as more responsible for healing failure than the number of appointments utilized. Trope et al. (77) studied the results of 556 cases that exhibited periapical lesions prior to treatment. The teeth were divided into 3 groups, one group treated in a single visit, a second treated in two visits, and the third treated in two appointments with calcium hydroxide placed in the canal for at least one week. After one year, evaluated by culture samples, the calcium hydroxide-treated cases were judged to be successful in 74 per cent of those teeth whereas the one-visit cases were successful in 64 per cent. The group treated in two appointments without calcium hydroxide had the poorest results. However, the authors stated that due to the differing teeth treated, no statistical analysis could be offered. However, the total percentages of success were much lower than reported in many other reports.
Saleh et al. (78) prepared canals, verified sterility, and then placed a suspension of Entoerococcus faecalis prior to canal filling at that appointment. Those teeth using sealers with strong antibacterial properties gave the best results. However, the authors warned that sealers high in antibacterial contents may be cytogenic or even mutagenic. AH Plus and Grossman’s sealer were considered the most reliable for antibacterial action with safety. Insertion of calcium hydroxide decreased the number of bacteria in the canals, but did not kill all the bacteria in the tubules.
Nair et al.(79), in an impressive study with beautiful color sections, evaluated treatment of 16 MBRs of maxillary first molars (a low number) with two canals and periapical disease in vivo. Immediately following the single-appointment therapy, the treated roots were surgically removed and evaluated microscopically. Multiple areas of canals revealed complex configurations with sites uninstrumented and many microbes. The authors speculated that treatment of this type of root in a single appointment with impressive decrease of bacteria is highly questionable. They quoted a study by Bystom and Sundqvist in 1981 that reported considerable debris, and microbes were noted in treated MBRs after five appointments. The conclusion by Nair was that the development of a bacteria-free MBR with presently used techniques is doubtful, particularly if using a single-treatment technique.
Waltimo et al. (80) reported in 2005 on an extension of the Saleh study (78) with several coauthors of the previous work. The study divided 50 teeth with chronic apical periodontitis into 3 groups. One group had one-visit treatment, the second had calcium hydroxide used as a medication for one week and the tooth treated in two appointments, and the third leaving the canal empty but sealed for one week. Only minor differences were found in the groups after one year, but the teeth where sodium hypochlorite was used as irrigant rather than calcium hydroxide being placed showed much better results. Calcium hydroxide has been recommended as intracanal medicament for the last 10 years, but this study had a different finding.
A widely informative study, with clear delineations and a proper cross section with ample post-operative follow-up evaluations, could be extremely valuable to every dentist who performs endodontic treatment and will allow the decision-making to be based on suitable criteria (81).
Endodontic therapy has reached a very high level of knowledge and usage in the past 10 years, even though the number of teeth requiring the treatment has probably decreased. The new instruments make treatment easier and the increased knowledge concerning the number and direction of the canals in each tooth is more apparent by recent studies and better radiology. It is very likely that newer replacements for gutta-percha involving synthetic materials is just over the horizon. Very few areas of dental treatment have had as much progress in evaluation and treatment in the last few years than has endodontics. I hope that this will continue for the near future, as well.