File Name: cleaning and shaping of root canal .zip
Principles of Cleaning and Shaping Techniques. Criteria for Evaluating Cleaning and Shaping. State reasons and describe strategies for enlarging the cervical portion of the canal to promote straight-line access. Describe objectives for both cleaning and shaping and explain how to determine when these have been achieved.
Illustrate shapes of differently created preparations and draw these both in longitudinal and cross-sectional diagrams. Illustrate probable actual shapes of preparations with iatrogenic errors created in curved canals. Describe techniques for shaping canals that have irregular shapes, such as round, oval, hourglass, bowling pin, kidney bean, or ribbon.
Distinguish between apical stop, apical seat, and open apex and discuss how to manage obturation in each. Characterize the difficulties of preparation in the presence of anatomic aberrations that make complete debridement difficult. List properties of suitable irrigants and identify which irrigant meets most of the criteria. Describe in general the principles of application of ultrasonic devices for enhanced root canal disinfection.
Evaluate in general alternative means of cleaning and shaping and list advantages and disadvantages of each. Discuss nickel-titanium NiTi hand and rotary instruments and how the physical properties of this metal affect cleaning and shaping. List the principal temporary filling materials and describe techniques for their placement and removal. Successful root canal treatment is based on establishing an accurate diagnosis and developing an appropriate treatment plan; applying knowledge of tooth anatomy and morphology shape ; and performing the debridement, disinfection, and obturation of the entire root canal system.
Historically, emphasis was on obturation and sealing the radicular space. However, no technique or material provides a seal that is completely impervious to moisture from either the apical or coronal aspect. Early studies on prognosis indicated that failures were attributable to incomplete obturation.
This proved fallacious, because obturation reflects only the adequacy of the cleaning and shaping. Canals that are poorly obturated may be incompletely cleaned and shaped. Adequate cleaning and shaping and establishing a coronal seal are the essential elements of successful treatment, and obturation is less important for short-term success.
Elimination or significant reduction of the inflamed or necrotic pulp tissue and microorganisms is the most critical factor. The role of obturation in long-term success has not been established; however, obturation may be significant in preventing recontamination either from the coronal or apical direction. Sealing the canal space after cleaning and shaping helps entomb any remaining organisms and, with the coronal seal, prevents or at least delays recontamination of the canal and periradicular tissues.
However, some bacterial species have been shown to survive entombment. Nonsurgical root canal treatment is a predictable method of retaining a tooth that otherwise would require extraction. Root canal treatment in a tooth with a vital pulp is more often successful than is root canal treatment of a tooth diagnosed with a necrotic pulp and periradicular pathosis.
The reason for this difference in outcome is the persistent presence of microorganisms and their metabolic byproducts. Instruments are believed to contact and plane the canal walls to debride the canal Figs. Morphologic factors include lateral canals Fig. These aberrations make total debridement virtually impossible. Therefore, a practical objective of cleaning is to significantly reduce the irritants, not totally eliminate them.
Currently, there are no reliable clinical methods to assess cleaning efficacy. The presence of clean dentinal shavings, the color of the irrigant, and canal enlargement three file sizes beyond the first instrument to bind have been used to assess the adequacy of cleaning; however, these do not correlate well with debridement. Obtaining glassy smooth walls is a suggested indicator, but this property cannot be assessed beyond the coronal aspect of the root canal system.
The purpose of shaping is to facilitate cleaning and provide space for placing obturating materials. The main objective of shaping is to maintain or develop a continuously tapering funnel from the canal orifice to the apex.
This reduces procedural errors during apical enlargement. The degree of enlargement is partly dictated by the method of obturation. There is a correlation between the depth of spreader penetration and the quality of the apical seal. As dentin is removed from the canal walls, the root becomes less resistant to fracture. The degree of shaping is determined by preoperative root dimensions, the obturation technique, and the restorative treatment plan.
Narrow, thin roots e. Although the concept of cleaning and shaping the root canal space is simple, consensus has not been reached on some points. One example is the extent of the apical preparation. Early studies identified the dentinocemental junction as the area where the pulp ends and the periodontal ligament begins. Unfortunately, this is a histologic landmark, and its position which is irregular within the canal cannot be determined clinically.
A classic study described the apical portion of the canal with the major diameter of the foramen and the minor diameter of the constriction see Fig. The apical constriction is defined as the narrowest portion of the canal; the average distance from the foramen to the constriction was found to be 0. Also, when present, it varied in shape and in relationship to the apical foramen. Variations from the classic appearance consist of the tapering constriction, multiple constrictions, and a parallel apical canal part.
To complicate the issue, the foramen is rarely located at the anatomic apex. Recently, micro-computed tomography data have provided a more realistic portrait of the apical canal morphology Fig. Apical anatomy has also been shown to be quite variable see Fig. A study found no typical pattern for foraminal openings; it also found that no foramen coincided with the apex of the root.
The same group reported the foramen-to-apex distance to range from 0. It has also been noted that the foramen-to-constriction distance increases with age, and root resorption may destroy the classic anatomic constriction. Resorptive processes are common with pulp necrosis and apical bone resorption. Therefore root resorption is an additional factor to consider in length determination. In a prospective study, significant adverse factors influencing success and failure were the presence of a perforation, preoperative periradicular disease, and incorrect length of the root canal filling.
A meta-analysis evaluation of success and failure indicated a better success rate when the obturation was confined to the canal space. A review of several studies on endodontic outcomes confirms that extrusion of materials decreases success. Two larger studies confirmed that overfill was associated with inferior outcomes. The exact clinical point of apical termination of the preparation and obturation remains a matter of debate.
Compacting the gutta-percha and sealer against the apical dentin matrix constriction of the canal is important in creating a seal. To prevent extrusion, the cleaning and shaping procedures should be confined to the radicular space. Canals filled to the radiographic apex are actually slightly overextended.
Generalizations can be made regarding tooth anatomy and morphology, although each tooth is unique. The length of canal preparation is often emphasized, with little consideration given to important factors such as canal diameter and shape. Because morphology is variable, there is no standardized apical canal size. Traditionally, preparation techniques were determined by the desire to limit procedural errors and by the method of obturation.
A small apical preparation reduces the incidence of preparation errors discussed later but may decrease the antimicrobial efficacy of cleaning procedures. It appears that with traditional hand instruments, apical transportation occurs in many curved canals enlarged beyond a No.
The criteria for cleaning and shaping should be based on the ability to adequately deliver sufficient amounts of irrigant and not on a specific obturation technique. Larger preparation sizes have been shown to provide adequate irrigation and debris removal and significantly decrease the number of microorganisms. However, any removal of dentin has the potential to weaken radicular structure; therefore, the use of an irrigation adjunct designed to promote irrigation efficacy in smaller canals may be advantageous.
In principle, there may to be a relationship between increasing the size of the apical preparation and canal cleanliness and bacterial reduction. Instrumentation techniques that advocate minimal apical preparation may be ineffective at achieving the goal of cleaning and disinfecting the root canal space. However, this concept reaches its limits when too large a preparation leads to procedural errors and when modifications created in the hard tissue block the very anatomy that was to be cleaned Fig.
A variety of microbial species can penetrate deep into dentinal tubules. These intratubular organisms are sheltered from endodontic instruments, the action of irrigants, and intracanal medicaments. Dentin removal appears to be the primary method for decreasing their numbers.
However, it may not be possible to remove bacteria that are deep in the tubules, regardless of the technique. There is a correlation between the number of organisms present and the depth of tubular penetration ; in teeth with apical periodontitis, bacteria may penetrate the tubules to the periphery of the root.
The development of nickel-titanium instruments has dramatically changed the techniques of cleaning and shaping; these instruments have been rapidly adopted by clinicians in many countries. The primary advantage of these flexible instruments is seen in shaping, specifically a significant reduction in the incidence of preparation errors.
Neither hand instruments nor rotary files have been shown to completely debride the canal. Mechanical enlargement of the canal space dramatically reduces the number of microorganisms present in the canal, but it cannot render the canal sterile.
Therefore, the use of antimicrobial irrigants has been recommended, in addition to mechanical preparation techniques. There is currently no consensus on the most appropriate irrigant or concentration of solution, although sodium hypochlorite NaOCl is the most widely used irrigant. Unfortunately, solutions such as NaOCl that are designed to kill bacteria are often toxic to the host cells ; therefore, extrusion beyond the canal space is to be avoided.
A major factor in the effectiveness of irrigants is the volume of irrigant used during the procedure. Increasing the volume produces cleaner preparations. In the apical patency technique, small hand files are repeatedly placed to or slightly beyond the apical foramen during canal preparation Fig. A benefit of this technique during cleaning and shaping procedures is that it ensures that the working length is not lost and that the apical portion of the root is not packed with tissue, dentin debris, and bacteria see Fig.
This technique has raised some concerns about extrusion of dentinal debris, bacteria, and irrigants. However, in a recent large, retrospective study, the apical patency technique was identified as a factor possibly associated with higher success rates. Moreover, at least in vitro, microorganisms do not appear to be transported beyond the confines of the canal by patency filing.
Small files are not directly effective in debridement see Fig.
Cleaning Is the removal of all potential irritants from the root canal. This includes: Infected material Organic Remnant Microbes.
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