Filling the root canal
At each new appointment during a root canal, it is necessary to have an anaesetic and rubber dam placed to isolate the tooth before the tooth is opened up again.
It is important that before the final root filling is placed, that each canal is free from any infection.
Signs that there may still be infection present include:
- Continued pain
- Persistent moisture in the canal.
If this is the case, the tooth may need to be re-sterilized and re-dressed and you may have to return to your dentist the following week.
The dentist will wash the canals with dental bleach and use special paper points to dry them. These are file shaped paper cones that match the different sizes of file. It is at this point they can assess if infection is still present. A nice dry paper point suggests the canal is disinfected, however, if blood or moisture is continually being seen further cleaning and re- dressing will be needed.
Assuming all the signs are good, the canals can now be filled with a special rubbery material called Gutta Percha (GP). Gutta Percha points are made of a pink, insoluble material (meaning it won’t dissolve away) and come in different shapes and sizes to correspond to the files that were used to clean out the canal and the paper points used to dry them. This ensures a nice snug fit and good seal of the canal.
There are a number of different techniques used to fill the root canal; they can be roughly divided into those that use cold GP and those that use heated GP. They all serve the same purpose, with similar success rates- to fill up the inside of the canal so bacteria can’t get in and any remaining bacteria are starved of the nutrients they need to survive.
The most common cold GP technique is called ‘cold lateral condensation’. First, sealer is applied to the walls of the canal using a file, and then the dentist carefully places the ‘master’ GP point to the length that was calculated earlier 1-2mm from the end of the root to seal the tip. This is the length we called our ‘working distance’.
Now the dentist uses a finger spreader (the same size and shape as a file but totally smooth) to push the first GP point to the side to allow another cone of GP covered in sealer to be placed into the canal next to it.
This process continues, pushing and compacting extra cones with sealer on them until the entire canal is full. This process forces the sealing cement and GP material against the sides of the canal and helps to block any extra canals coming off the main one.
When the dentist is satisfied that the canal is nicely filled, a heated instrument is used to remove the excess and condense the GP that little bit further into the canal.
Some methods involve heating up Gutta Percha and flowing the warm material into the canal. Various systems are available, perhaps the most widely known is ‘thermofil’ which uses a small plastic carrier to push the hot GP into the canal, causing it to flow and adapt to the exact shape of the inner walls. Single tapered GP points that correspond exactly to the size of the rotary files are also available.
A final X-ray is taken to ensure that the root system has been filled nicely. Generally on this X-ray we are looking at two things:
- That we have the right length root filling
- That the filling material has been compacted well.
At this stage, the top of the canal is generally sealed with appropriate cement and a temporary is placed over the tooth, ready to be restored properly next visit. Again some dentists may choose to do this all in one visit.
Once the root canal is completed, there are no particular precautions you need to take; the tooth may take a couple of days to settle down. If pain persists see- root canal pain.
In summary, the stages for a root canal are:
- Diagnosis. Confirm which tooth it is and that a root canal is the right treatment
- Shaping. Produce a gradual funnel shape in the canal, widest at the top ending just before the tip of the root (about 1-2mm)
- Cleaning. Remove bacteria and remnants of the nerve from the canal using small files and washing the canal with an antibacterial solution
- Filling. Completely fill the funnel created by shaping the canal
- Restoring the tooth. Give the tooth back its looks and ability to chew.
What goes on Top of a Root Filled Tooth?
The root filled tooth needs to have a good seal to prevent bacteria getting in and re-infecting it. The dentist will place some variation of glass ionomer, composite or amalgam to replace the missing part of the tooth.
Teeth that have had the nerve and blood supply removed during a root filling are much more brittle than those normal living teeth. This leaves them prone to fracture, which if it occurs, often leads to the tooth being lost.
Posterior (back teeth) take a lot of force during chewing and it is because of this that it is recommended by professional bodies all over the world that molar root treated teeth have full coverage restorations to protect them. What does this mean? It means that the whole occlusal (biting) surface is in one material such as porcelain, gold or even at a stretch amalgam. Both the American Dental Association and Australian Dental Association recommend this.
For the most part this means having a crown. A crown acts like a helmet encasing and protecting the tooth and most importantly, ensuring an even pressure on the tooth. It is advisable to place a crown as soon as possible after the root canal treatment (assuming the tooth has settled down). Full coverage onlays are another less used possibility.
I would not advise having a crown, if you were still having pain. However, the longer it is left, the more time the tooth has to fracture, so some dentists may protect it by placing a little metal band around it and taking it out of the bite.
It is important to understand though, that not all root treated teeth will fracture without a crown and in exceptional circumstances, it can even happen under a crown. I see patients fairly often that have had root filled teeth for years, who cannot afford a crown and so far they are without trouble. A crown will simply help protect your tooth as best possible and as root treatment is an expensive and time-consuming procedure, this investment makes sense to me. I also see patients who have run this risk- not having a crown and who haven’t been so lucky; their tooth fractured and required an extraction.
Front teeth can often just be filled with composite filling material, unless a large part of the tooth is missing and the tooth is considered weak and in need of a crown or post and crown. They take less force than the back teeth during chewing, so often filling is sufficient.
If you really can’t afford a crown but can afford a root canal, I would suggest you go ahead with the root canal treatment and ask the dentist to fill the tooth (place the core) for the time being. That way you haven’t lost your tooth and you can save for a crown. Yes, you run a small risk but what is the alternative… an extraction. Don’t get complacent though and think that just because the tooth seems fine that you no-longer need a crown- until you have it done, the tooth will remain more vulnerable to fracture.
Following a root canal:
- A filling is always needed (referred to as a core if a crown is planned but essentially the same thing)
- If the remaining tooth is weak a post may be needed
- Teeth with posts must have a crown
- Posterior (back) teeth should be crowned
- Anterior (front) teeth don’t necessarily need crowns.