A Concise Guide to Endodontic Procedures

Millions of teeth are extracted every year and most dentists are doing everything possible to save teeth. But many patients feel that having a painful tooth extracted is the most economical way to solve their problem. Patients need to be told that if root canal treatment and restoration can be used to save the tooth; that getting the treatment is preferable over the long term to maintain their quality of life and ability to chew food. The patient’s own description of their pain is an important diagnostic aid. The diagnosis of pulp, periodontal tissue and dentin status should follow a consistent and logical order to ensure that a tooth is given the most appropriate endodontic treatment. A comprehensive endodontic examination is not restricted to a hot tooth and should be performed on all new and existing patients. The ideal radiograph will show the crown and cervical aspects of the tooth. Diagnosis is part science and part experience. Avoiding pitfalls will improve the success of endodontic treatment. There are appropriate and inappropriate endodontic treatments based on the pulp sensibility and differential diagnosis of the tooth. The best treatment plan is the one most likely to benefit the patient and provide them with the highest quality longest lasting endodontic care.

A high proportion of children and adults will suffer from traumatic dental injuries (TDIs) caused by sudden impact forces to teeth generated by falls, fights, sports-related injuries and traffic accidents. Immediate treatment and an accurate differential diagnosis of the type of TDI is needed to ensure the tooth is given the most appropriate treatment. The starting point is always to assess if the tooth has been completely avulsed from its socket and replanted. If the tooth has not been avulsed, the displacement of the tooth and its mobility beyond normal limits should be tested. If several teeth move as one unit, it is characteristic of an alveolar fracture. If a single tooth moves and a fracture can been seen in a radiographic, it is characteristic of a root fracture. If no root fracture can be identified in a radiograph, it suggests that the tooth has had an extrusion. A tooth which appears to be in an abnormal position because of protrusion or retrusion, has suffered from lateral luxation. A tooth which is abnormally located by intrusion out of its socket into alveolar bone, has suffered from intrusion. If the tooth has not been displaced, but is loose, has suffered from subluxation. If the tooth has not been displaced, but is not loose, and has percussion tenderness, it has suffered concussion. If the tooth has not been displaced, it is not loose, and has no percussion tenderness, it has suffered concussion. If the tooth has not been displaced, it is not loose, and has no percussion tenderness, and it has suffered a fracture above the gingiva which exposed the pulp, the tooth has suffered a complicated crown fracture. If a tooth has a crown-root fracture that has not exposed pulp, it has suffered an uncomplicated crown fracture. If a tooth has a crown-root fracture that has exposed pulp, it has suffered a complicated crown fracture. If the extent of the fracture is so minimal that no tooth structure has been lost, the tooth has suffered an infraction. If the tooth has no discernible symptoms of trauma, then it can be assumed that the tooth has no injury.

Young patients with developing immature permanent teeth present special problems to save their teeth following dental traumatic injury or caries decay. As a consequence, the endodontic treatments for traumatized immature permanent teeth with an exposed pulp can vary considerably among dentists. The apexification procedure is the most common and highest standard of care for immature teeth with a necrotic pulp or irreversible pulpitis. However the development of the teeth will cease at an immature stage of development, thus weak dentinal walls and short roots will remain. For teeth with very thin dentinal walls which are likely to fracture and need strengthening, a revascularization procedure can be used to disinfect the root canal with antibiotics and revitalize new tissue formation. The revascularization procedure is so called because it accomplishes tissue formation within the root canal by blood revascularization from the periapical tissues through the open apex. Alternatively, the necrotic and irreversible pulpitis tissues can be debrided, the root canal disinfected, and a scaffold placed inside the root canal to promote tissue formation in a regenerative endodontic procedure. Regenerative endodontic procedures should never be used to preserve deciduous (baby) teeth. There is little evidence to support the use of an endodontic revascularization procedure on an avulsed and replanted tooth, but it could strengthen the root canal walls of immature teeth and save them from being unrestorable following a fracture

Dental radiographs can show hidden dental structures such as cavities, anomalies, malignant or benign masses, impacted wisdom teeth, periapical lesions and bone resorption that cannot be seen during a visual examination. Dental materials for tooth restoration with filings and crowns, or root canal obturation and sealing can appear lighter or darker depending on the density of the material. Most dental materials contain a radiopaque material such as Barium sulphate to help visualize the material in radiographs. Bitewing radiographs are routinely used to detect tooth decay and recurrent caries under existing restorations. Periapical radiographs are taken to visualize the root apex, periapical tissues and bone surrounding teeth that a patient is complaining of being painful or/and has swelling and/or the symptoms of infection. Occlusal radiographs are taken to visualize the skeletal or pathologic anatomy of either the floor of the mouth or the palate. Panoramic radiographs are occasionally taken using extraoral films and show a broad view of the jaws, teeth, sinuses, nasal area, and temporomandibular joints and anatomic structures. Digital radiographs are an acceptable first choice for the diagnosis and treatment of dental pathology. Cone beam computed tomography (CBCT) imaging is becoming a complementary technology and in many instances can provide 3-dimensional oral pathology information that might have been overlooked on 2-dimensional images. Odontogenic cysts and tumors can be identified using radiology, clinical diagnosis and histopathology. The most common odontogenic cysts of the jaws are Periapical cysts, also called Radicular cysts, Root End Cysts, Periodontal Cysts, Apical Periodontal Cysts, and a Dental cyst; they are most commonly seen in patients aged 20 to 60 years old. Patients can worry about the radiation from radiographs, even though the amount is very low, care must always be taken to reduce your own and the patient’s exposure to radiation. But do not be afraid of re-taking radiographs that are needed to diagnose pathology and to decide on an accurate treatment plan. It is better to have good quality radiographs than have to interpret poor-quality radiographs that are out of focus and angled incorrectly.

The odontoblast cells within dental pulp create the roots of teeth through a process of dentinogenesis during tooth development. Dental pulp initially occupies the root canal space within each root of a tooth. The root canal space containing dental pulp reduces in volume throughout life, because of dentinogenesis, which is the continual calcification and mineralization process of odontoblasts. As a patient gets older their root canals become more calcified and narrower, in old age the root canals of teeth can be completely calcified with no apparent dental pulp remaining. These continuing mineralization processes within the root canals of teeth give rise to alterations in root canal morphology which can present challenges for the ideal position of the endodontic access. The goal of the access is to locate and provide the direct access of files and instruments into the root canals of the tooth. The position and design of the access is determined by the size of the pulp chamber, the age of the tooth, previous restorative efforts, the long axis of the tooth, and root curvature. The location and design of the access cavity is dictated by the pulp chamber morphology of the tooth being treated. Achieving adequate access to the root canal is the key to accomplishing endodontic success. In order to remove the dental pulp the location of the coronal pulp chamber and the pulp within the roots must be visualized. To help visualize the location of the dental pulp, there are laws to be used to help position the access and find the orifices to root canals:Root canal centrality, Root canal concentricity, Dentin color change, Symmetry 1 and 2, and Orifice location 1 and 2. If the access is not adequate for endodontic treatment, it could compromise the cleaning, shaping and obturation of the root canals which could increase the risk of treatment failure.

The success of non-surgical endodontic root canal treatment requires the use of files and instruments to remove necrotic and infected tissues. The cleaning and shaping are separate concepts but are always performed together. The goal of cleaning the root canal is the removal of necrotic pulp and infected tissues. The goal of shaping the canal is to maintain the apical foramen as small as possible in its original anatomic position. A good endodontic treatment outcome is dependent on the removal of necrotic pulp and infected tissues to a low level that cannot cause a flare up which will require retreatment. After a straight-line access cavity has been cut to allow direct access of the instruments into the root canals, and the orifices of the root canals have been identified. The next step is to instrument the root canals. The instrumentation process can be simplified by dividing the procedure in a series of steps. The majority of teeth are approximately 19-25 mm in length. Most roots are 9-15mm and most crowns are 10mm in length. An easy concept is to divide the root canal into three regions; coronal, middle and apical. Each of these regions is likely to be between 3-5mm in length. Dividing the root canal into three regions is a helpful strategy for instrumenting complicated calcified root canals with a challenging morphology. It is necessary to accurately measure tooth length in order to carry out and fulfill the basic tenets of root canal therapy. This measurement should be 0.5mm to 1mm short of the radiographic apical foramen, to create an apical stop within the tooth structure in order to confine instrumentation and the filling material. The radiograhic length is the length of the tooth as it appears on the radiograph. The estimated working length is the radiographic length minus 1mm. The final working length is -1mm substracted from the anatomical apex measure from the working length radiograph. NiTi rotary instruments have proved to be extremely successful for cleaning and shaping root canals, but they should not be used when the dentinal walls are extremely thin to avoid perforation of the root canal. Curved canals are the most challenging to instrument, because the distortion of the files and instruments will cut into the curve to reduce its angle, and place pressure on the cutting tips in an opposite direction, thereby increasing the risk of cutting a perforation. The risk of cutting a perforation in curved canals increases when larger file sizes are used. To avoid perforations, the concept of anti-curvature filing is to prepare a straight line access through the root canal to the apical region, by filing away the bulky root structure to create a displacement space, and by not touching the thin root walls which are in danger of being perforated. When a perforation occurs, it should be repaired immediately using restorative materials, with a thin liner of MTA being placed against the vital periodontal tissues or bone. The prognosis of a perforated tooth depends on the size, location, and the time taken to repair it.

Hundreds of bacterial species inhabit the mouth, because of bacterial interactions, nutrient availability and low oxygen potentials in root canals with necrotic pulp, the number of bacterial species present in endodontic infections are restricted. These selective conditions lead to the predominance of facultive and strictly anaerobic microorganisms that survive and multiply, causing infections that stimulate local bone resorption, and are more resistant to endodontic treatment. Instrumentation of the root canal alone is not sufficient to remove infected necrotic tissues. The root canal must never be instrumented dry, an irrigating solution is always needed to reduce the amount of friction between the instrument and dentin surface to prevent binding and sticking. An irrigating solution is also needed to improve the cutting effectiveness of the files and instruments, dissolve tissue, cool the file and tooth, wash debris from the root canal, and be bactericidal in areas of the canal which could not be instrumented. Sodium hypochlorite has been the most widely used root canal irrigating solution for several decades, because it is inexpensive, can quickly dissolve infected necrotic tissues and is bactericidal. Sodium hypochlorite is very toxic to tissues when undiluted and so accidental spillage is always a concern among dentists. A severe limitation of Sodium hypochlorite and most other irrigating solutions is that they are unable to dissolve the instrumentation debris on cut dentin surfaces, called smear layer. The smear layer is a 1 to 5 micron thick layer of cut debris created on the surface of instrumented dentin, composed of dentin, odontoblastic processes, non-specific inorganic contaminants and microorganisms. To remove smear layer a chelating agent must be used after the irrigating solution to help clean the instrumented root canal surfaces. The most widely used chelating agent inside the root canal is 17% ethylenediaminetetraacetic acid (EDTA). A solution of 17% EDTA is a very reliable endodontic chelating agent when used fresh and at room temperature, but its chelating effects are time sensitive. Testing and clinical evidence has shown that 17% EDTA needs to be placed inside the root canal for 1 minute to effectively dissolve organic components and smear layer. The EDTA then needs to be suctioned, dried with paper points, and/or rinsed with Sodium hypochlorite to ensure it has been completely removed from the root canal after use. The process of canal preparation with files, instruments, and irrigating solutions is usually sufficient to remove most of the necrotic and infected tissues. Some recent articles suggest that the ultrasonic activation of irrigating solutions by using a high-speed vacuum; the EndoVac system, and that a laser using photon-induced photoacoustic streaming (PIPS) can improve the debridement of root canals.

The root canal must be dried with paper points prior to its obturation, as residual irrigation fluids will leave voids. The majority of dentists will use gutta percha as the primary filling material in root-canal therapy. The reason for the success of gutta percha among dentists is because it is easy to manipulate into the root canal, it is radopaque and easily seen on radiographs, and it can be removed from the canal and be replaced when necessary. Fresh Gutta percha has good handling properties, while aged Gutta percha can become brittle. Some dentists prefer to insert the gutta percha point into the canal without altering it, while other dentists like to soften the Gutta percha with heated instruments or chemicals. The softened Gutta percha can then be condensed into the canal using lateral or vertical condensation. An advantage of Gutta percha is that it is inert to the periapical tissues if it should become extruded past the root apex. Gutta-percha filling techniques use a prefitted primary point procedure, verified by a radiograph to fit the full length of the canal and to still fit tightly in the apical region of the root canal. The largest possible gutta-percha point is normally selected according to the size of the last instrument used to the full length of the prepared canal. Thin root canals or canals with an extreme curve are more difficult to obturate with standard sizes of Gutta percha points. In these situations, heated instruments or chloroform can be used to chemically soften the gutta-percha for 5 seconds so that it can be more easily into the curvature and the minimally prepared apex. The success of endodontic treatment is dependent on the obturation of the root canal with gutta percha and sealers which can seal the entire root canal, thereby preventing microleakage and the re-infection of the root canal. The sealer is evenly coated on the prepared canal surface, with the last instrument used to spread it throughout the canal length using an up and down motion. Sealers are needed to seal the gutta percha core material and prevent microleakage. The sealer fills voids and irregularities of the root canal space left unfilled by the obturation core material. Adequate sealing of the obturation material inside the root canal is important to the success of endodontic treatment, because up to 60% of endodontic treatment failures are caused by the incomplete obturation of the root canal. Root canal sealers can vary greatly in composition and contain Zinc oxide eugenol, Calcium hydroxide, Glass ionomer, Composite resin, Silipoint, Urethane Metha-crylate, Formaldehyde, and Bis-phenol A. The quality of root canal obturation can be seen in radiographs and a poor quality of obturation can increase the risk of a flare up and treatment failure

Surgery is an integral aspect of endodontic therapy for the treatment of cases when root canal therapy is not deemed sufficient to remove the infection. Over recent years the amount of endodontic surgeries has been decreasing as the reliability and success of root canal procedures have been increasing. Periradicular surgery is not always a necessary step towards endodontic success, it should never be used as a cure for a poor endodontic root canal technique. Surgery is often assumed to be the most radical procedure; however, sometimes the surgical procedure becomes a conservative effort to avoid further tissue injury, and extraction of the tooth. Resorption of the root canal apex was an indication for surgery to remove necrotic tissue, however some clinical cases have demonstrated that periapical healing can arrest the resorptive process by nonsurgical root-canal therapy. An incompletely developed apex was once assumed to require surgery, however there are now improved regeneration techniques for saving immature teeth. The accidental extrusion of sealer and obturation core material into the periapical tissues are only candidates for surgery of they cause a persistent periapical radiolucency, swelling and pain. A horizontal fracture of the root apex may not require surgery, if the apical canal fragment contains vital tissue. Only if the apical tissue becomes necrotic, then it may be necessary to remove the apical fragment. By trial and error, it has become clear that surgery is not always in the best interests of saving a tooth if a nonsurgical treatment can suffice. The types of surgery include: Anatomical Redesigning is needed as part of periodontal treatment, for root amputation, hemisection, and bicuspidization. Apical Resection is the removal of the root end of a tooth. Bicuspidization is the separation of a multirooted tooth by a vertical cut through the furcation. Hemisection is the removal of a root and its coronal portion from a multirooted tooth. Incision and drainage is needed to release exudates from swollen soft tissues. Intentional tooth replantation may be considered when no other course of root canal treatment is possible and extraction of the hopeless tooth is inevitable. Marsupialization is a decompression technique used to reduce a massive cyst without surgical curettage. A periapical curettage is performed by removing the pathologic tissues surrounding the apex of a tooth without disturbing the root. Root Amputation is the removal of a root from a multi-rooted tooth, leaving the coronal portion of the tooth intact. Trephination requires anesthetic and is the perforation of a cortical plate to release the pressure of an exudate with alveolar bone. Surgery has become a specialized field in endodontics and most surgical cases should be referred to specialists for treatment.