There are different ways to treat pulp and periapical disorders in endodontics. The aim is to render the contents of the pulpa chamber and root canal harmless for the area around the apex. If harmful stimuli cannot reach the area around the apex, no deviation will occur or continue to exist.
Endodontic treatments are carried out under rubber dam to prevent contamination with saliva and microorganisms. In order to be able to properly estimate the axis direction of the element during the opening of the pulp chamber, the rubber dam is only installed after the channels have been looked up.
More and more dentists use an operating microscope in endodontics. With some microscopes, a magnification of 24x the normal image can be achieved. This makes narrow root canal entrances easier to find and the treatment can be carried out more precisely (see image below).
Recurrent procedures in endodontics are preparation and cleaning of the pulp cavity and closing the root canals. In addition, there are some special endodontic treatments, which will be discussed later.
Complete preparation and cleaning of the pulp cavity
This endodontic treatment removes the entire contents of the pulp chamber and root canal. The root canals get such a shape (preparation) that a good apical closure is possible. The procedure of treatment is as follows.
- A solo photo of the element in question is made for the treatment (starting photo).
- If the element to be treated is vital, local anesthesia is given.
- With a fast turning corner piece and a straight diamond drill, a cavity is drilled well into the dentine. For incisives and cuspidates, the endodontic opening is palatinally resp. prepared linguistically and with premolars and molars in the occlusal plane.
- With a large, round steel drill in a slowly rotating corner piece, a perforation is made to the pulp chamber.
- With a special drill with a non-sharpening point, the roof of the pulpa room is completely removed. The walls of the opening are finished without damaging the bottom of the pulp chamber.
- The entrances to the root canals are looked up with a thin file or with a straight probe.
- Rubber dam is installed; the work site is disinfected with, for example, alcohol.
- From this stage, all the instruments to be used must be sterile.
- The root canal entrances are widened to improve accessibility (see image below).
The cleaning and shaping of the root canals can now begin. The purpose of this is to rid the root canal of all remains of pulp tissue and to render any microorganisms present harmless. The design is also important to be able to make a good channel filling to the root point.
Cleaning and shaping can be carried out in various ways. The following hand tools are available for this purpose: the Torpan file, the reamer and the Hedström file. In addition to the hand instruments, mechanically driven instruments are often used to prepare root canals (see image below).
There are various hold and file systems in use. It is important that a system consists of reamers and / or files that are arranged according to increasing thickness and whose length is adjustable. The root canals differ in diameter and length.
The thickness of the instruments is indicated by colors, numbers or grooves. This coding is the same internationally for all systems. We speak of the ISO classification. For example, a file with point thickness 15 always has a white-colored cup. The instruments can be conveniently stored in the so-called endobox (see image below).
The files can be adjusted to length with round discs made of rubber or silicone. The correct length is set with a measuring block (see images below).
For the various mechanical file systems, special files are placed in an endo angle. The corner piece brings the file in an up-and-down and / or rotating movement, depending on the system used. A length stop can usually be applied to the file; some systems have grooves on the file, from which the length can be read. The endo angle can be equipped with an irrigation system for sodium hypochlorite.
Irrigation is an essential support when preparing the root canal. Irrigation is understood to mean rinsing the root canal during preparation to support mechanical cleaning. The most suitable flushing agent is a 6% solution of sodium hypochlorite (NaOCl). The beneficial effect of NaOCl is based on chemical and mechanical effects:
- The chemical effects consist of disinfecting the pulp cavity and dissolving organic substances, such as tissue residues.
- The mechanical effects mean that pulp residues, filings, pus and blood are washed away and files and reamers can be handled more easily.
NaOCl inactivates upon contact with organic substances. In order to maximize its effect, the liquid must therefore be constantly refreshed during preparation. And it must be in direct contact with the tissue residues to be dissolved. Ultrasonic irrigation improves the rinse aid result. In addition to NaOCl, irrigation is performed with EDTA, chlorhexidine and physiological saline.
To prepare the root canal, the root canal is filed conically or funnel-shaped. This is possible in three ways:
- With the step-back method, the correct length is first filed to the main file. After this, files will be filed half an millimeter shorter with ever thicker files.
- With the step-down or crown-down method, first a thicker file is filed up to a few millimeters before the root point. Subsequently, filings are filed with increasingly thinner files to the final length.
- Machine preparation. Rotary files are often conically shaped or taped.
The method for preparing and cleaning the root canals is described on the basis of the step-back method.
- The initial photo is used to estimate the distance between a certain nodule or incisal edge (the reference point) and the location in the channel to which one wants to file: the provisional length. A thin file is set with the measuring block, so that the instrument length corresponds to the estimated value.
- The set file is placed in the channel until the stop encounters the reference knobs. The final length is now determined by taking a length photo or with an electronic length determiner (ELB). If the definitive length is known, all required files are set to this length (working length) (see image below).
- Starting with the thinnest file, each root canal is prepared. The file is brought to the working length in the channel and scraped up from apical to coronal, on all sides. When this is easy, the next, slightly thicker file is transferred. After each file the channel is flushed with NaOCl.
- If the apical part is clean after the use of a few thickness-increasing files, the subsequent file is set 0.5 to 1 mm shorter. This is repeated until the entire root canal is prepared in this way.
- The last file used at working length is called the main file. Finally, this main file completes the steps in the step-back preparation.
- After filing, the root canal is once again rinsed with NaOCl and then dried with paper points.
Closing root canals
Closing the root canals can be done after the preparation and cleaning of the root canal, so still in the same session. If the channel cannot be made dry, for example due to the presence of inflammatory moisture periapically, or if closure is not possible due to a lack of time, this will be done in the second session. In that case, the root canals are temporarily filled with calcium hydroxide (Ca (OH) 2) using a lentulone needle or a syringe with a special tip. Sometimes a sterile cotton ball is placed in the pulp cavity. There will be a temporary filling in the coronal part.
Many methods can be used to permanently close a root canal. The following methods are discussed:
- Lateral condensation (possibly combined with vertical condensation);
- Finish with warm gutta-percha.
Usually gutta-percha is used, a rubbery, thermoplastic filling material. Gutta percha pins are supplied in the same thicknesses as files and reamers. The entire root canal is filled with this material. The procedure is as follows.
- After cleaning and shaping the root canal, a gutta percha pin with the same thickness (same number) as the main file is selected. The pin is fitted and must reach the working length in the channel. A pinch in the gutta-percha is made with tweezers to mark the working length. This pin is now the main pin.
- The so-called spreader is then fitted. A spreader is a smooth metal needle that is used to push the gutta percha pins laterally against the channel wall (lateral condensation). The thickest spreader (A, B, C or D), which reaches the working length, is set to length.
- Finally, the stopper (English: plugger) is fitted. With this, the gutta percha mass is condensed vertically.
- After drying the root canal, the main pin in the root canal is cemented with root canal cement. The spreader is introduced into the channel next to the main pin (lateral condensation) to make room for a thinner (15 or 20) secondary pin. This is supplied with a small amount of cement and placed. This pin will come a little less far into the channel. After lateral condensation, another secondary pin follows. This procedure is repeated until the entire channel is filled.
- In the end, the 'grove' of gutta percha pins sticking out of the pulpa room is removed with a hot instrument to the canal entrance. With the stopper, the gutta-percha cement is now condensed as much as possible vertically in the channel.
- A so-called heat carrier can be used to obtain an even more homogeneous filling or to partially empty the root canal again for a post. After heating the instrument, the tip is placed in the gutta percha mass and excess material can be removed. The remaining gutta percha mass can then be condensed vertically again. There are also heat carriers on the market that operate on the mains or on batteries. The carrier is brought cold into the channel next to the gutta-percha and then the mass is heated for 10 seconds and condensed horizontally. After ten seconds the carrier is removed from the channel again and the procedure is repeated after placement of the secondary pins. This heat carrier can also be used to condense vertically (see images below).
Closure with warm gutta-percha
When closed with warm gutta-percha, the main pin is placed in a root canal pre-lubricated with cement. The pin is then made plastic with a hot instrument. The soft gutta percha is then condensed to apical and lateral up to 5 mm before the root point with a plugger. The rest of the channel is injected with heated gutta percha from a pressure syringe through a needle into the root canal. The heated gutta percha is applied in small portions and pressed in between with a root canal stopper until the entire canal is filled. This method is called obturation technique (see figure below).
Another system uses a carrying pin. This is a metal or plastic marker coated with gutta-percha. After preparation, the correct size is determined with a special pen. The pin thus selected is then heated in a special oven for four to seven minutes, depending on the thickness of the pin. The pin is then placed in the root canal pre-lubricated with cement with firm pressure. The metal or plastic pin is therefore not the filling material here, but acts as a carrier for the heated gutta-percha. If the pin is correctly positioned, a notch is drilled into the pin just above the channel entrance. The coronal part of the pin is broken off and removed. The gutta-percha is then pushed into the root canal entrance with a hand stopper.