Resin Root Canal Fillings: Fact or Fiction

In 2005, the first new, non-gutta percha (GP) root filling material in 50 years was launched. The manufacturers of Resilon, a synthetic resin root filling material, claimed to have significantly better sealing ability than gutta percha. The concept behind Resilon was the desirability of bonding the resin point to a resin sealer, which in turn could be bonded to the dentin walls, creating a gapless “monoblock”.
A Google search of ten studies comparing the apical leakage of GP to Resilon (R) found essentially no difference between the two materials (R leakage > GP, Hashem ’04, Pasqualini ’08; GP leakage > R, Shipper ’04, Bodrumlu ’06, Wedding ’07; GP leakage = R, Pitout ’06, Saleh ’07, Ishimura ’07, Munoz ’07, Baumgartner ’07).
Apparently, the literature does not support the superior sealing ability of Resilon, contrary to manufacturer’s claims. Something must have been happening to disrupt the “monoblock” in the critical apical third of the canal.
To get the most effective dentin bond, the smear layer needs to be removed from the dentin walls created during the cleaning and shaping process. Removing the smear layer exposes and opens the dentinal tubules, making them available to the resin sealer. In endodontics, this is accomplished with an EDTA rinse after cleaning and shaping is complete. Teixeira et al, IEJ, May ’05, found EDTA rinses of up to three minutes were unpredictable in removing the smear layer (5 of 12 showing complete smear layer removal).
Mjor et al, IEJ, July ’01, used scanning election microscopy (SEM) to look at the dentin structure in the apical third. He found the apical dentinal tubules were “irregular in direction and density” with some areas “devoid of dentinal tubules” and concluded that “obturation techniques based on the penetration of adhesives into dentinal tubules are unlikely to be successful”.
In the August 2005 edition of JOE, Tay et al. evaluated the effect of C-factor on dentin adhesion in the apical third. C-factor is the ratio of bonded to unbonded surface area – the higher the C-factor, the greater the amount of shrinkage and gap formation. Shrinkage stresses, created during polymerization of the low-filled, low-viscosity resin root canal sealers such as Epiphany, are much higher when compared with highly filled composite restorative fillings. The cone shape geometry in the apical third of the root canal system creates C-factors in the 1000 range, with limited unbonded surface area to relieve shrinkage stress. Tay concluded that “bonding of adhesive root filling materials to root canals is highly unfavourable”.

So while the “monoblock” theory is exceptionally appealing to the endo junkies and the manufacturers give us beautiful, gapless, resin filling-dentin SEM interfaces, the available literature to date just does not support the claims that resin root canal fillings are any more effective than our tried and true GP/ZOE sealer fillings. Paucity of dentinal tubules, unpredictability of smear layer removal in the apical third, and high shrinkage stresses create resin point/sealer/dentin gaps, resulting in leakage. Until I see more conclusive evidence, I’m sticking with good old gutta percha.

ABOUT DR. HOWARD BITTNER

Dr. Bittner was born and raised in the Surrey/Langley area. Following his pre-dental training at Simon Fraser University, he received his Doctor of Dental Medicine from the University of British Columbia in 1982 and his Certificate in Advanced Graduate Studies in Endodontics from Boston University’s Goldman School of Dental Medicine in 1995.

Dr. Bittner was in private practice in general dentistry for 11 years in Langley prior to his endodontic specialty training. He has a wide background in all facets of general dentistry, with advanced dental training in prosthetic dentistry from respected educational facilities such as Creating Restorative Excellence in Tacoma, Washington, and The Pankey Institute in Miami, Florida. He has been practicing the dental specialty of Endodontics since 1995.

He is a past president of the British Columbia Society of Endodontists, the Dental Specialists Society of British Columbia, and the Concentric Endodontic Study Club. Dr. Bittner is also a guest lecturer in the Faculty of Dentistry at the University of British Columbia.

On June 6, 2009, posted in: News for Doctors by