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4. Periodontic and Endodontic Instruments


a. Endodontics.

(1) Two types of endodontic treatment. Endodontics is that branch of dentistry which deals with the diagnosis and treatment of diseases of the pulp and the periapical tissues. A vital tooth is furnished with both a blood and nerve supply. When the tooth is deprived of its blood and nerve supply, through trauma or infection, it is diseased and requires endodontic treatment. Endodontic treatment or therapy is of two types: nonsurgical, or conservative, and surgical. Conservative endodontic therapy involves obturating the root canal or canals by gaining access through the crown of the tooth. It also encompasses pulp capping, pulpotomy, and pulpectomy in connection with restorative treatment. (Obturating refers to filling the entire root canal completely and densely with a non-irritating, air-tight sealing agent.) Surgical endodontic therapy involves gaining access to the root canals by removing the bone about the root end of the tooth. Sometimes a portion of the root end is removed and prepared to accept an amalgam filling.

(2) The infection process. When the pulp of a tooth is damaged beyond repair, it deteriorates. Tissues of the pulp break down, and the pulp chamber and canals become a source of infection, harboring pathogenic bacteria. These breakdown products cause a deterioration of the healthy tissue about the root end or apex of the tooth. Apical infection (tooth root infection) not only destroys this healthy tissue, but can impair the patient's health. Before the advent of endodontics, the treatment for this condition was extraction. The loss of a tooth can cause changes in the masticatory function of the teeth and mental anguish to the patient. Replacement of the tooth often requires extensive procedures. Sometimes, replacement is not feasible. Therefore, as long as supporting structures of the teeth are healthy, endodontics may be indicated to preserve the dentition in its most nearly natural form.

b. The Role of the dental assistant in Endodontics. In addition to general clinical duties, the dental assistant assigned as an assistant in endodontics will be expected to become familiar with the techniques, materials, and instruments used by the dentist.

(1) Constant awareness of need for asepsis. Most important, the dental assistant must always be aware of the need for cleanliness, disinfection, and proper sterilization. One contaminated instrument can lead to endodontic failure. Personal hygiene and tidy appearance are most reassuring to all concerned.

(2) Patient care technique. The dental assistant also should make a special effort to be extremely tactful with patients. For example, patients automatically associate the nerve of a tooth with pain. Reassuring gestures and attitude are helpful in gaining the patient's confidence.

(3) Proficiency in using x-rays. Endodontics requires the dental assistant to be familiar with basic radiographic techniques, effects of radiation, and protection of the patient by the use of a lead apron. He should review techniques for developing radiographs as he will often be required to develop them for the endodontist.

(4) Proficiency with tooth numbering system. He should be aware of the tooth numbering system and nomenclature used in the armed services, because he will be required to transcribe the information gained from each appointment to the patient's record. This is especially important when a tooth with several root canals is involved. If any doubtful situation arises, the dental assistant should always consult the dentist.

(5) Flexibility. Each dentist uses the techniques of instrumentation and the particular methods that work best for him. The endodontic assistant should be flexible enough to adjust to different techniques.

c. Techniques of Root Canal Therapy. There are three basic phases in endodontic treatment. First is the diagnostic phase in which the disease to be treated is determined and the treatment plan developed. The second is the preparatory phase, when the contents of the root canal are removed and the canal prepared for the filling material. The third involves the filling or obliteration of the canal to gain a hermetic (airtight) seal as close as possible to the cementodentinal junction, with an inert material. The dental assistant plays a key role in the successful completion of all three phases by having the necessary equipment ready at the appropriate time.

(1) Diagnosing. All root canal therapy begins with a diagnosis. First, the dentist takes an oral history of the patient's particular problem. The assistant should enter the patient's chief complaint (abbreviated C.C.) on the record. The chief complaint should be written in the patient's own words. Next, a clinical examination should be performed. The assistant should provide the basic examination setup for dentist. When the offending tooth or area is located, a periapical radiograph is taken to aid in the diagnosis. Frequently, a radiograph will not reveal any definite pathology. In this case, the assistant should be prepared to provide the dentist with auxiliary diagnostic aids. The electric pulp tester (figure 4-13) and warm and cold thermal tests are the most commonly used auxiliary diagnostic aids.

Figure 4-13. Electric pulp-tester.

(2) Preparing the canal. Once the diagnosis is made, local anesthesia may be administered by the dentist. The rubber dam is applied, and the area of the rubber dam around the affected tooth is swabbed with an iodophor or alcohol disinfectant. The dentist uses a high- speed handpiece to create an occlusal or lingual opening into the pulp chamber of the tooth. The slow-speed handpiece may be used to refine the shape and size of the opening. Next, a barbed broach may be used to remove the pulp tissue. At this point, a small file fitted with a rubber stop (figure 4-14) is placed in the root canal, and the dental assistant takes a periapical radiograph of the tooth containing the stoppered file. This is referred to as the trial-file radiograph and is used to determine the correct working length of the files used. Once the working length is determined by the dentist, all files used will be measured with the endodontic ruler and stop- pered at the correct working length. The working length, expressed in millimeters, should be recorded in the patient's treatment record. Using reamers and files of increasing size stoppered to the correct working length, the root canal can be gradually shaped and enlarged. During the filing, the canal is irrigated to provide lubrication and a flushing action on the debris. Sodium hypochlorite (5 percent solution) is usually the irrigant used, and is administered with a large plastic syringe. When filing is completed, small paper points are used to dry the root canal.

Figure 4-14. Endodontic ruler and file with rubber stop.

(3) Filling and sealing the canal. When the dentist has determined that the root canal is sufficiently enlarged, he will select and trial-fit a gutta-percha point or silver point of the same size as the last file used. Once the point passes the trial fit, it is ready to be cemented. The dental assistant mixes the root canal cement or prepares a mix of zinc oxide and eugenol that can be drawn up from the mixing slab about 1 inch without separating. The point is coated with the cement and seated into place. Depending on the technique, a plugger or a spreader, or both, is used to condense the gutta-percha in the root canal. When the root canal has been filled satisfactorily, a thick mix of zinc oxide and eugenol or zinc phosphate cement is made and plugged into the access area to completely seal the canal. Completion of the endodontic treatment may not be accomplished in a single appointment. Therefore, medicament may be placed inside the pulp chamber or canals in a cotton pellet or paper point. The access opening is then sealed with an interim restorative material such as IRM.


David L. Heiserman, Editor

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Revised: June 06, 2015