Isolating the tooth
The dentist will begin by isolating the teeth with a rubber dam. This is done to isolate the tooth’s canals from bacteria outside and also keeps it dry. Moreover gives the dentist a nice, isolated work-area where she can concentrate on the tooth.
The rubber dam is a latex sheet with a hole which will allow the treated teeth to be exposed whilst sealing of the rest of the teeth. This sheet is then clamped to keep it in place within the mouth.
Creating the access cavity
To clean the root canals of the tooth, the dentist has to drill a hole through the tooth’s surface and dentin and reach its pulp chamber. With the back-teeth, the dentist will have to chisel the tooth’s central grinding surface to reach the tooth’s canals and with the front-teeth the opening will be made backside. This hole will allow the dentist to get access to the infection at the canals and will also enable to remove infected bits of teeth.
Measuring the canals
The length of the canals vary quite a bit and measuring them accurately is a key component of the treatment which will enable the dentist to treat the canals adequately without leaving it incomplete and also not going beyond the length. The dentist can determine the length by placing a metal file(used to clean) inside the canal and then taking an Xray. This will tell the dentist how far the file is inside the root canal and with a simple calculation can determine how much further the file should go.
Alternatively, the dentist can also use an electronic measuring device. The device has 2 wire leads, one is clipped to the file and the other is gently clipped to patients lip – the device will beep when the file reaches the end of the canal. Teeth can have several canals and each of them will have to be measured if they are infected.
Cleaning the root canal
Cleaning and shaping a tooth is the whole purpose of the root canal process. Cleaning removes debri, bacteria, infected, dead and live tissue from the canals and the pulp chamber. The shaping of the tooth is done to remove infected bits and also to enable getting an optimal shape to facilitate filling and if needed placing a crown.
Tooth is cleaned with the help of root canal files which are basically tapered metal(1) with rough contour(2) and a holding area(4) and a plastic stopper(3) that can be slid as needed to mark the workable section. The dentist will have files of varying curvature and sizes to fit the differently curved canals.
The files are moved along the canal with a twirling motion sych that the abrasive surface of the file scrapes and removes infected tissues from the canal. Often upto 6 different files of varying sizes are used so as to scrape any infected tissue lodged against the walls of the canal.
This cleaning process with files can be done either by hand or with the help of a dental drill. Tooth irrigation is important right through the filing process to facilitate the removal of the scraped debris. Sodium hypochlorite which is also a disinfectant is the preferred choice.
Sealing the canals
Once the canals are cleaned, it is then time to seal it with a filling. A rubber compound called “gutta pecha“ is commonly employed as a permanent sealer. Gutta pecha resembles the files used to clean the canals and have a cone like shape.. Several such cones are used to ensure that the canal is stuffed tight.
Before inserting them into the hollow cleaned canals a paste is applied on them so that the various rubber cones adhere better to each other and form a water tight sealant inside the root canal. The dentist may alternatively use a dental glue-gun device that can warm the rubber compound and introduce it into the canal in the form of a paste.
Filling and Restoration
Once the tooth is clean and free of infection in the canals, the tooth is internally stable, but it still has that access cavity that needs to be closed. Depending on the tooth’s residual stability and strength, the dentist can advice the patient on a crown or a filling.
Filling it with a dental restorative method is usually ok if the access cavity is small and the teeth didn’t already suffer from structural instabilities due to the trauma of the root canal procedure and other inherent infections of the canal, otherwise a crown is the sensible option. A good crown can extend the life and health of the tooth after a root canal.
The above chart is a visual representation of a study performed by medline that evaluated 1609 patients over a decade and found that crown restorations on teeth with moderate instabilities after root canal exhibited significantly better life. The crown is like a shell protecting the tooth, whereas filling is just plugging the cavity with restorative material and works like cement in layman terms, so – the above result is to be expected. Infact with molars that have fractures and bigger access cavity, the benefits of crown are even more significant.