Obturation……….Where are we now?
In broad terms Endodontic treatment success would indicate an absence of infection, a healing or completely resolved lesion, a functional tooth without pain or discomfort and radiographically, a reversal to a normal periodontal ligament space around the root.
Using this definition Endodontic success rates have not massively changed over the last 30 years and it’s interesting to consider why that may be. I appreciate the cases we may now choose are more challenging but is it that straight forward an answer? The advances in our technology has progressed exponentially. On a recent day at simplyendo it was noted 8 out of the 10 delegates on the 10 day programme each used magnification of some description; mostly loupes with and without lights but also microscopes. Consider the same course even 10 years ago and I am sure the numbers would have been far different. File systems have advanced without showing any suggestion of slowing down and many dental schools now teach very little hand filing- some teach none (A different debate for another day). Whilst at Dental School prior to 2004, hand filing with some use of Gates Gliddens was all I was taught and this was probably the same across all dental schools at the time. Now, there is a vast choice of instrument design to choose from and no doubt comes down to personal choice, experience, education, recommendation and possibly cost. Going back to the early question, if we can see better with magnification (and lights) and shape better with better instruments, why therefore have endodontic outcome studies failed to demonstrate an improvement in endodontic healing? Personally I feel the answer falls into 2 categories; irrigation and obturation. Improved shaping methods provide a better platform for irrigation and for obturation. As Schilder described, an unshaped canal cannot be cleaned and an unshaped canal cannot be filled. Both of these topics of irrigation and obturation are quite enormous in their own right so lets take this opportunity to look at obturation- where we have come from, where we are now and a sneak peak at the future. Does obturation hold the keys to greater, more predictable endodontic success?
Firstly why do we bother to obturate? (Sorry- I’m full of questions today!) Although we have tried our best to clean out the root canal system, we have to assume it is not truly 100% free of microorganisms so we aim to emtomb any remaing bacteria inside with gutta percha. Obturation is there to seal coronally, apically and laterally to prevent reinfection of the root canal system.
What therefore should we use to obturate? The current ESE guidelines for obturation are fairly broad and describe the use of a semi-solid material with sealer, the ideal properties for both are described as by Grossman and the reason behind why we obturate are described but nowhere does it mention gutta percha.
Could we use something else?
Over the years many other materials have been used. Way back in 1800 the first root canal fillings were obturated with Gold. ‘Endodontics’ (of a sort) had been carried out prior to this and in 1725 Lazare Riviere advised the use of clove oil for its sedative properties. In 1820 Leonard Koecker cauterized exposed pulp with a heated instrument and protected it with lead foil. (Remember this was some time prior to the 1910 advancement of local anaesthetic!) Since this early use of gold, various metals, paraffin, pastes, bamboo and even amalgam were used before Hill developed the first use of gutta percha in 1847, termed Hills Stopping. This consisted of bleached gutta percha (GP) and carbonated lime.
A little while later Perry wrapped warm GP around a gold wire and demonstrated the early use of a carrier system. It wasn’t till 1978 that Ben Johnson, from the USA, developed Thermafil® utilising essentially the same idea of warm GP heated in an oven on a plastic carrier and now more recently with the developments of Gutta Core® moving the idea along again.
Back to 1887 and the SS white company were the first dental company to manufacture GP cones. Around the same time GP was also being used as a replacement to wood to make golf balls, as it was easy to heat and roll the material to make it round. Rumour has it that as the golf ball was damaged during use it developed divots into its surface and the Lords would pass these damaged balls to their ‘servants’ only to find that the servants would then consistently hit the damaged ball further. This was due to the divots transferring pockets of air from the front of the ball to the back, reducing drag and subsequently travelling further….. hence all golf balls now have divots across their surface!! GP was also being used to splint wounds and to control haemorrhage in extracted socket wounds.
Gutta-percha is a dried coagulated extract of plants of Palaquium, Blanco genus of Sapotaceae family. These trees are natural inhabitants of south east Asia.
Chemically gutta-percha is a trans-isomer of poly isoprene and its chemical structure is 1,4,trans-polyisoprene, close to natural rubber.
Back to root canals…….. in 1893, Rollins used GP with pure oxide of mercury into root canal filling and in 1914 Callahan introduced softening and dissolution of gutta-percha with the use of rosins in obturation. A variation of a later chlorapercha technique perhaps? (If you are not familiar with this technique, look it up. A sneaky way of taking an impression of the apical preparation with GP.)
In 1947 there was a slight deviation from GP when silver points were introduced. Ever slightly more bonkers was the use of sectional silverpoints where a notch was cut into the last 3-4mm of the point prior to insertion and on its insertion it was deliberately fractured and separated at this point leaving behind this 3-4mm of silverpoint to allow space for a post in the root canal…. essentially a fractured instrument in the apical one third.
However, many Dentists were still using GP (sometimes along with silver points as a combination method) and in 1959, after suggestion from Ingle and Levine at the International Conference of Endodontics at Philadelphia, the first standardised Gutta-percha was introduced. In 1976 a group evolved into the present day International Standards Organisation (ISO) for approval of specification of root canal instruments and filling materials.
In the 1980s thermoplasticised GP was born initially with Schilder methods of warm vertical condensation and then tweaked in the early 90s with Steve Buchanan’s continuous wave of condensation.
There have been little deviations with the use of bonded obturation materials such as Epiphany with Resilon but it never really caught on as bonding inside the root canal system is fairly unpredictable due to less dentinal tubules and massive C-factor (the ratio of bonded to un-bonded walls). Also there is the argument that removing the smear layer to improve our cleaning ability is important but this probably reduces the bond strength of the resin.
Where are we then now? Whilst gutta percha remains the number one choice for endodontists there is no agreed method of how to obturate canals. The most taught and researched method of obturation is cold lateral condensation, which can be time consuming and technique sensitive. A trend amongst GDPs would be to use a single cone, which matches the last instrument in the shaping protocol and interestingly the cross sectional mass of GP in single cone obturation is relatively comparable with that of lateral condensation. Unfortunately single cone obturation relies on the assumption that canals are round which we know is most certainly not the case. Maybe we could add a few extra accessory cones to our single cone……Mike calls this single cone PLUS! Still, due to the taper of these cones to match the preparation, the middle to apical part of the canal is a single cone with sealer.
What about heated techniques? A favoured method amongst endodontists would be one of warm vertical condensation following Schilder, Buchanan or a hybrid of the two (I’m in the hybrid camp!). This technique provides predictable results (after an initial learning curve) and satisfies the principles of a 3 dimensional obturation. It can however be time consuming, has an increased risk of extrusion, the cost of more equipment and the worry that the gutta percha shrinks on cooling.
What about 1883 idea by Perry utilising a carrier? Heating GP out of the mouth in an oven (originally with a Bunsen) before placement is a carrier technique and if used correctly can provide excellent obturation results radiographically but it also has a learning curve, the cost of more equipment and due to the piston action in the canal when placing this carrier, has a significantly higher chance of extrusion of both GP and Sealer. There is very little apical control and there are suggestions to ‘measure it slightly short to prevent extrusion’- hardly an exact science. It has been shown to be quicker to obturate canals with carriers than other methods, maybe with the exception of a single cone! Historically the problems with carriers were the difficulties to remove plastic or metal carriers from the canal in retreatment or if placing a post. This has been changed somewhat now with the use of pink cross-linked gutta-percha to provide a central rigid core rather than the need for metal or plastic carriers so it isn’t so tricky to drill through for a post or in retreatment. In truth all of these methods provide similar results. Leakage occurs with all of them and although there is a plethora of lab-based studies trying to replicate the clinical situation it is difficult to compare many studies with one another- some use a vacuum, some don’t, some use dye, others microorganisms…and some both!
So with any method what actually seals the root canal? The answer is sealer of course. So maybe this is where the future is going to change our thought process. Sealer is required in all obturation methods. Sealer is there to fill the spaces between GP and the canal wall (or in cold lateral, between GP and GP also). In 1988 Grossman, who wrote many lists about ideal properties, concluded that all available root canal sealers fall short of the ideal.
What about now? Bioceramic sealers may hold the key to ensuring a suitable seal and reduce leakage in our obturation. Historically a small amount of sealer has been advised but maybe it is time to move forward to a sealer rich obturation utilising ‘hydraulic condensation’. This way we could use our single cone with a bioceramic sealer, such as BC sealer with matching GP points, which would be both quick to achieve and create a suitable seal. The single cone is tapered e.g 6% to match the last instrument so it’s not an ISO 2% taper swimming in a sea of sealer.
BC Sealer is a bioceramic sealer of MTA descent (Others are available and more will be coming). Bioceramics have a hydration and a precipitation reaction. These sealers are hydrophilic, biocompatible and antibacterial due to the high pH. This material bonds to dentine due to the hydropxyapetite formation of the sealer. One of the main benefits of using a BC sealer over a thermoplastic GP obturation is that the sealer will not shrink like GP as it cools- the sealer is already cold.
Can we just fill the canals with sealer? Well, you could but this unfortunately would make any retreatment impossible. The GP cone is necessary to help carry the cement to length and also acts as a path for retreatment by providing a channel through the sealer. The GP cones used in this technique are silanated in order to bond to the BC sealer. Studies by Trope have shown a bond between sealer and the GP, and sealer and the dentine wall. There have also been some suggestions that this type of sealer and obturation method may increase the fracture resistance of teeth treated this way. Now, I don’t want to get all too excited just yet as I remember not all that long ago when the resin based sealer called Epiphany with resilon I mentioned earlier was promoted in exactly the same way as this, bonding to dentine and helping to prevent fracture resistance with a ‘monoblock’ obturation. Admittedly the bond design was different (it required a bonding system) but it’s funny that these years later it not longer is used. I do however feel there is something different about these BC sealers. There is more inertia behind these sealers and excitement amongst endodontists. MTA has changed how we treat pulp caps, perforations, apexicifation and how we carry out microsurgical endodontics. Therefore it would make perfect sense to use an MTA material, which has been modified to be used as a sealer in our obturation. Only time will tell how or if our success rates change but this may be a further step in the right direction. The future for endo obturation is bright…….the future could be sealer!
David Baker, simplyendo
References (definitely not APA style and well spotted by our marking team!)
Quality guidelines for endodontic treatment: consensus report of the European Society of Endodontolgy.
IEJ, 39, 921-930, 2006.
Gutta- percha- an untold story.
R. Prakash, V. Gopikrishna and D. Kandaswamy
A Brief History of Endodontics
Pathways of the Pulp.
Cohen and Burns.
Chapter 9- Obturation of the Cleaned and Shaped Root Canal System.
Gutmann and Witherspoon.
8th Edition. Mosby.