Adjunct Endodontic Procedures
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Intracoronal bleaching (aka non-vital bleaching or walk-in bleaching) can be very useful for selectively improving the aesthetics of teeth discolored due to trauma or endodontic therapy. Internal bleaching is a safe and straightforward procedure but patients should be warned about the potential cervical resorption, thought to be triggered when the bleaching solution penetrates the dentinal tubules and activates osteoclastic activity. In severe cases the subsequent damage may lead to the loss of the tooth.
Under rubber dam isolation the pulp chamber is accessed and all restorative material is cleared to a point a few millimeters below the gingival margin. A cement barrier is placed over the gutta-percha to minimize dentinal tubule penetration in order to reduce the potential risk of cervical resorption. A bleaching agent (usually sodium perborate) is mixed with saline or sterile water and packed into the pulp cavity. A cotton pellet can be inserted into the pulp chamber in order to act as a reservoir. The access site is finally sealed with a temporary filling material and tooth reviewed in 3-7 days. Once a satisfactory value is achieved, the access cavity can be definitively restored.
VITAL PULP THERAPIES
Direct and indirect pulp capping procedures aim to induce the formation of reparative dentin and the maintenance or restoration of healthy vital pulp.
An indirect pulp capping procedure involves the application of a bio-inductive lining material over a thin layer of remaining dentin. By definition there has been no pulpal exposure. In the case of deep caries removal, a two stage procedure was traditionally recommended. The first appointment involved the placement of a thin layer of medicament like calcium hydroxide or MTA, followed by a temporary restoration. At a second visit 6-8 months later, the temporary restoration, lining material, and remaining affected dentine is removed and a definitive restoration placed. More recently there has been a paradigm shift and the second appointment is no longer required. Indirect pulp capping is appropriate in the deciduous dentition in some cases. An indirect pulp capping procedure is recommended in cases where:
- A tooth fracture does not involve the pulp.
- There is an absence of pulpal symptoms or periapical pathology.
- A tooth presents with a deep carious lesion where complete removal of carious structure would likely result in pulp exposure.
A direct pulp capping procedure involves the application of a bio-inductive lining material directly into an area of exposed pulp. There is no second appointment required. A thin layer of calcium hydroxide or MTA is placed directly onto the surface of vital pulp tissue at the site of the pulp exposure, followed by a base and the final restoration. Direct pulp capping is not appropriate in the deciduous dentition. Circumstances that would be appropriate for direct pulp capping in an adult tooth are best treated with a pulpotomy in a deciduous tooth. A direct pulp capping procedure is recommended in cases where:
- A pulpal exposure was small (preferably pin-point size) in an asymptomatic tooth.
- Pulp exposure was non-carious, either due to trauma or operator error.
- Hemorrhage is easily controlled (indicates a lack of inflammation).
- Exposure permits the capping material to make direct contact with the vital pulp tissue.
A pulpotomy involves the surgical removal of a portion of the coronal portion of vital pulp in an attempt to preserve the vitality of the remaining pulp. In primary teeth, most pulpotomies are performed when a carious pulp exposure occurs and involve complete removal of the coronal pulp. On the other hand, pulp exposures resulting from complicated crown fractures in permanent teeth are mostly treated with Cvek pulpotomy, where only 1-3 mm of the coronal pulp is aseptically removed. After removal of the coronal portion of the compromised vital pulp tissue, hemostasis is obtained and a biologically acceptable bio-inductive material is applied directly to pulp tissue before restoring. A pulpotomy procedure is recommended in cases where:
- Vital pulp is exposed.
- Irreversible pulpitis is diagnosed in primary teeth.
- A temporary solution is sought before definite root canal treatment.
- A root has not completely formed.
Apexification is a method to induce the formation of an apical barrier in a necrotic tooth with an open apex. Recall, the tooth fully matures (apex closes) around 2-3 after eruption. Apexification can be accomplished by:
- Placing dense medicament (calcium hydroxide paste) in the root canal space after the instrumentation, and waiting for apical barrier formation (3-6 months), then obturating.
- Placing an artificial apical barrier using MTA, prior to immediate obturation.
Apexogenesis is a vital pulp therapy procedure performed to allow continued physiologic development and formation of the root. After the coronal pulp is amputated and hemorrhage controlled, calcium hydroxide or MTA is placed over the radicular pulp stump. The tooth is monitored radiographically with the hope of complete root formation, before conventional root canal treatment is completed. Apexogenesis is not recommended for:
- Avulsed teeth.
- Unrestorable teeth.
- Horizontally fractured teeth with a poor prognosis.
- Necrotic pulp.
PULP THERAPY MEDICAMENTS
Calcium hydroxide is an odorless white powder or paste commonly used as an inter-appointment dressing. Its primary function is antibacterial, attributable to its high pH. In addition to inhibiting bacterial colonization of the canal space, calcium hydroxide is well tolerated by pulpal tissue, encourages calcification, and inhibits the resorption process. It is used for pulp capping, partial pulpotomy, apexogenesis, apexification, and for preventing or inhibiting active root resorption.
Mineral trioxide aggregate (MTA) is a non-toxic, biocompatible portland cement derivative made of primarily fine hydrophilic particles. It consists of calcium phosphate and calcium oxide and sets in the presence of moisture. MTA has a high pH that is able to induce hard tissue formation. It is radiopaque, has a long working time and a long setting time and can be difficult to manipulate.
SURGICAL ENDODONTICS
Incision and drainage aims to evacuate purulent exudate in order to speed healing and reduce discomfort from pressure buildup. Trephination is the surgical perforation of the alveolar cortical bone, indicated if a pathway is needed through hard tissue to obtain necessary drainage. Trephination can also be used if profound anesthesia is difficult to achieve. Apical trephination involves driving a size 15 to 25 k-file through the apex of a tooth.
An apicoectomy is a surgical procedure that involves surgical access of the apex of a tooth, root apex excision, and restoration with an appropriate endodontic material. A mucoperiosteal flap is elevated and bone removed to allow direct visualization. The root end is resected and root end prepared before a biocompatible root-end filling material (usually MTA) is placed. After the wound is adequately cleaned, guided tissue regeneration techniques and/or bone grafting may be employed prior to flap replacement. If a tooth presents with failed endodontic treatment it is usually best to try and retreat using conventional root canal therapy. However, if that fails, or if the tooth has been restored with a post, core and crown, an apicoectomy should be performed. An apicoectomy procedure is recommended in cases where:
- Periradicular infection persists or worsens following endodontic treatment.
- There is marked over-extrusion of obturation material that interferes with healing.
- The apical portion of the tooth cannot be adequately cleaned and obturated (challenging anatomy, file separation etc).
Periapical curettage follows many of the same steps as an apicoectomy procedure, but the root apex is not removed.
Hemisection refers to the sectioning of a multirooted tooth through the furcation. Each portion of the root is still connected to a coronal fragment. Root resection/root amputation refers to the separation of the root(s) of a multirooted tooth leaving the crown intact. Both can be used to remove a compromised portion of a tooth while keeping another part in situ.
STERILIZATION
Endodontic instruments are contaminated with blood, organic and inorganic remnants, bacteria, and bacterial byproducts. If used in multiple appointments (not single use) they must be appropriately cleaned and sterilized. Pre-cleaning is an important step to reduce the number of contaminated microbes. Water based disinfectant-detergents are preferred. Ultrasonic cleaners are commonly used to increase the success of precleaning. An ultrasonic washer cleans by the cavitations produced by ultrasound waves. Briefly, types of sterilization include:
- Surface disinfection – endodontic files and other instruments are cleaned during canal debridement using a sponge soaked in 70% isopropyl alcohol or proprietary quaternary ammonium solutions.
- Glutaraldehyde – instruments are immersed for a sufficient period of time in solutions such as glutaraldehyde. Generally, a 24 hour soak is required to achieve adequate cold sterilization. This is not the preferred sterilization technique and seldom employed in a dental practice, reserved only for instruments that cannot tolerate heat sterilization. Practically, most clinicians would switch to single use or find an alternative that would be compatible with heat sterilization.
- Pressure sterilization – instruments are cleaned, bagged and autoclaved for 20 minutes at 121˚ C (250°F) at 15 psi. This heat-pressure combination is sufficient to kill all bacteria, spores, and viruses. Steam (most common) or chemicals can be used, but both will dull instruments. Pressure sterilization has a much faster turnaround than dry heat and is most commonly used in a general dental setting.
- Dry heat sterilization – dry heat is superior for sterilizing sharp-edged instruments since the process will not dull a cutting edge like the processes above. Higher temperatures are used compared to pressure sterilization. A common cycle is 160˚ C (320°F) for 60 minutes.
STERILIZATION CYCLES AND TESTING
Testing cleaning equipment and protocols is a very important part of proper cross-infection control. All modern autoclaves produce traceable data for each cleaning cycle. A 2016 CDC document, “CDC Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care” recommends that when running any type of autoclaved loads and cycles, users verify that their autoclave is functioning properly by carrying out the following tests:
- Vacuum test, Bowie-Dick test and Helix test daily before the autoclave is used.
- Biological and chemical checks during each sterilization cycle.
The vacuum test is run internally within the autoclave as one of its cycle options. It takes around 20-30 minutes and should be performed daily and only when the appliance is cold and empty. The test fails if it detects a leak rate in excess of 1.3 mbar/min during the 10 minutes that the test lasts for.
A Bowie-Dick test is conducted before the first processed load in an otherwise empty chamber. It is a sensitive and rapid means of detecting air leaks, inadequate air removal, inadequate steam penetration, and non-condensable gasses (e.g., air or gas from boiler additives). A Bowie-Dick test pack uses a Class II chemical indicator placed horizontally in the front, bottom section of the sterilizer rack near the door and over the drain. The test is conducted using an abbreviated cycle (3-4 minutes) with no dry time. The test should never be run longer than that 4-minute exposure.
Stream penetration tests like the Helix Test measure the effectiveness of the initial vacuum phase and, therefore, how well steam penetrates cavities. The Helix Test is placed in the sterilization chamber alone by the steam outlet (lowest tray) after an initial empty cycle is carried out.
Biological monitoring (spore testing) involves the use of biological indicators impregnated with highly resistant, non pathogenic bacterial spores to test a sterilizer’s function. Biological indicators such as the OSHA Review’s Spore Check System is used by many practices to monitor and document proper autoclave function. The main spores used are:
- Geobacillus stearothermophilus – steam/chemical sterilizers.
- Bacillus atrophaeus – dry heat sterilizers.
Chemical indicators are included in each load and can help to assess the physical conditions of each cycle and help to identify procedural errors. External indicators are applied on the outside of the sterilization packages. Internal chemical indicators should be placed inside each package next to the instruments to ensure that the sterilizing agent reaches the inside of the package. Chemical indicators designate that a package has been placed through a sterilization cycle, but do not prove that sterilization has occurred.
Ultrasonic cleaner foil tests are used in a tank after running the device for a few minutes. The foil is held like a curtain one inch above the bottom for 20 seconds. If the ultrasonic is performing properly, every part of the foil should show visible indentations.
Instruments are cleaned according to their use classification:
- Critical items – objects expected to enter sterile tissue and confer high risk of infection if they are contaminated. These instruments must be sterilized before use. Though any instrument could be classified as critical, common instruments include extraction forceps, scalers, and scalpel blades.
- Semi-critical items – objects expected to come into contact with mucous membranes or non-intact skin. These items have a lower risk of transmission but should still be sterilized. Instruments include mouth mirrors, cheek retractors, impression trays, and amalgam condensers. Digital radiography sensors are considered semi-critical but Food and Drug Administration (FDA)-cleared removable barriers are usually used.
- Non-critical items – objects expected to come into contact with intact skin only. Since intact skin provides an effective antimicrobial barrier, these items pose the least risk of transmission of infection. Non-critical instruments need only to be disinfected. Non-critical instruments include neck chains, blood pressure cuffs, facebow, and computer keypads.
