11. Technique of tooth cavity discl

11. Technique of tooth cavity disclosure. An instrumental and medicament treatment of root canal. Modern methods of root canal cleaning and shaping. Mistakes and complications of root canal treatment.

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. Initially, emphasis was on obturation and sealing the radicular space. However, no technique or material provides a seal that is completely impervious to moisture either from the apical or coronal areas. Early prognosis studies indicated failures were attributed to incomplete obturation. This proved fallacious as obturation only reflects the adequacy of the cleaning and shaping. Canals that are poorly obturated are often incompletely cleaned and shaped. Adequate cleaning and shaping and establishing a coronal seal are the essential elements for successful treatment, with obturation being less important for short-term success. Elimination (or significant reduction) of the inflamed or necrotic pulp tissue and microorganisms are the most critical factors. The role of obturation in long-term success has not been established but may be significant in preventing recontamination either from the coronal or apical areas. Sealing the canal space after cleaning and shaping will entomb any remaining organisms3 and, with the coronal seal, prevent recontamination of the canal and periradicular tissues.
Endodontic access openings are based on the anatomy and morphology of each individual tooth group. In general, the pulp chamber morphology dictates the design of the access preparation. The internal anatomy is projected onto the external surface. The major objectives of the access openings include (1) locating all canals, (2) unimpeded straight-line access of the instruments in the canals to the apical one third or the first curve (if present), (3) removal of the chamber roof and all coronal pulp tissue, and (4) conservation of tooth structure.
Canal Morphologies
Five major canal morphologies have been identified. They include round, ribbon or figure eight, ovoid, bowling pin, kidney bean, and C-shape. With the exception of the round morphologic shape, each presents unique problems for adequate cleaning and shaping.


Figure. Common canal morphologies.
A, Round. B, Ribbon-shaped (hourglass). C, Ovoid. D, Bowling pin. E, Kidney bean-shaped. F, C-shaped.
General Principles
The general principles for endodontic access are outline form, convenience form, caries removal, and toilet of the cavity.
Outline form is the recommended shape for access of a normal tooth with radiographic evidence of a pulp chamber and canal space. The outline form assures the correct shape and location and provides straight-line access to the apical portion of the canal or to the first curvature. The access preparation must remove tooth structure that will impede the cleaning and shaping of the canal or canals. The outline form is a projection of the internal tooth anatomy onto the external root structure. The form can change with time. As an example, in anterior teeth with mesial and distal pulp horns the access is triangular. In older individuals with chamber calcification, the pulp horns are absent, so the access is ovoid.
Convenience form allows modification of the ideal outline form to facilitate unstrained instrument placement and manipulation. As an example, the use of nickel-titanium rotary instruments requires straight-line access. An access might be modified to permit placement and manipulation of the nickel-titanium instruments. Another example is a premolar exhibiting three roots. The outline form might be made more triangular to facilitate canal location.
Caries removal is essential for several reasons. First, removing caries permits the development of an aseptic environment before entering the pulp chamber and radicular space. Second, it allows assessment of restorability before treatment. Third, it provides sound tooth structure so that an adequate provisional restoration can be placed. Unsupported tooth structure is removed to ensure a coronal seal during and after treatment so that the reference point for length determination is not lost should fracture occur.
Toilet of the cavity involves preventing materials and objects from entering the chamber and canal space. A common error is entering the pulp chamber before the coronal structure or restorative materials are adequately prepared. As a result, these materials enter the canal space and may block the apical portion of the canal.
Stages of tooth’ cavity disclosure:
1. Unroofing of pulp chamber;
2. gaining straight-line access to root canal orifices;
3. final forming of carious cavity and tooth’ cavity.
Access should be designed to reduce the curvature required to negotiate the apical 1/3 of the canal and will involve removal of the entire roof of the pulp chamber, including the pulp horns. The access to cavity in anterior teeth should be midway between incisal edge and the cingulum, and in posterior teeth will vary according to the anatomy of the pulp chamber (Fig.1). Lining up a bur with the pre-operative radiograph will help to gauge the depth of preparation. The turbine handpiece should be used to gain initial access, reverting to slow speed for removal of the roof of the pulp chamber and subsequent preparation. When access is completed, the cavity should have a smooth funnel shape.
Tooth’ cavity disclosure of posterior teeth is better to do in the projections of pulp horns, with the round-shaped burs. A shaping of tooth’ cavity walls, with the help of fissure burs are performed.

Fig.1. Diagram that shows the most preferable sites for tooth cavity disclosure
Often, in an attempt to preserve tooth structure, the access openings are constricted and underprepared. This creates problems with locating canals and gaining straight-line access. Removal of restorative materials is often warranted, knowing that following treatment they will be replaced. Removal enhances visibility and may reveal undetected canals, caries, or coronal fractures. When difficulties occur with calcifications or extensive restorations, the operator can become disoriented with respect to canal morphology. The discovery of one canal can serve as a reference in locating the remaining canals. A file can be inserted and a radiograph exposed to reveal which canal has been located.
Complex restorations, such as crowns and fixed partial dentures, may have changed the coronal landmarks used in canal location. A tipped tooth might be “uprighted” or a rotated tooth “realigned.” Loss of orientation can result in the incorrect identification of a canal, and searching for the other canals in the wrong direction results in excessive removal of tooth structure, perforation, or the failure to locate and debride all canals.
Access through crowns with extensive foundations may make visibility difficult. Class V restorations may have induced coronal calcification or could have been placed directly into the pulp space or the canals. In some instances, it may be best to remove restorative materials that interfere with visualization before initiating root canal treatment. A modification of the armamentarium for teeth restored with crowns has been advocated for all-ceramic crowns. The initial outline and penetration through the restorative material are made with a round diamond bur in the high-speed handpiece with water coolant. After penetration into dentin, a fissure bur can be used. In teeth with porcelain-fused-to-metal restorations, a metal cutting bur is recommended. When possible, the access should remain in metal to reduce the potential for fracture in the porcelain. Evidence indicates that with a water coolant and careful instrumentation, diamond and carbide burs are equally effective.
In summary, aids in canal location include knowledge of pulp anatomy and morphology; parallel straight-on and angled radiographs/digital images; a sharp endodontic explorer; interim radiographs/digital images; long-shanked, slow-speed burs; ultrasonic instruments for troughing; dye staining; irrigation; transillumination; and enhanced vision with loupes or microscopy.
ACCESS OPENINGS AND CANAL LOCATION
Maxillary Central and Lateral Incisors
The maxillary central incisor has one root and one canal. In young individuals, the prominent pulp horns present require a triangular-outline form to ensure tissue and obturation materials are removed, which might cause coronal discoloration. While the canal is centered in the root at the cementoenamel junction (CEJ) and when viewing the tooth from a mesial to distal orientation, it is evident that the crown is not directly in line with the long axis of the root. For this reason the establishment of the outline form and initial penetration into enamel are made with the bur perpendicular to the lingual surface of the tooth. This outline form is made in the middle-third of the lingual surface. After penetration to the depth of 2 to 3 mm, the bur is reoriented to coincide with the long axis and lingual orientation of the root. This reduces the risk of a lateral perforation through the facial surface. An additional common error is the failure to remove the lingual shelf, which will result in inadequate access to the entire canal. The canal is located by using a sharp endodontic explorer. In cases where calcification has occurred, long-shanked burs in a slow-speed handpiece can be used. These burs move the head of the handpiece away from the tooth and enhance the ability to see exactly where the bur is placed in the tooth.

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11. the Technique of tooth Cay disclosure. An instrumental and medicament treatment of the root canal. Modern methods of root canal cleaning and shaping. Mistakes and complications of root canal treatment. 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. Initially, the emphasis was on obturation and sealing the radicular space. However, no technique or material provides a seal that is completely impervious to moisture either from the apical or coronal areas. The early prognosis studies indicated failures were attributed to incomplete obturation. This proved fallacious as obturation only reflects the adequacy of the cleaning and shaping. Canals that are poorly obturated are often incompletely cleaned and shaped. Adequate cleaning and shaping and establishing a coronal seal are the essential elements for successful treatment, with obturation being less important for short-term success. Elimination (or significant reduction) of the inflamed or necrotic pulp tissue and microorganisms are the most critical factors. The role of obturation in long-term success has not been established but may be significant in preventing recontamination either from the coronal or apical areas. Sealing the canal space after cleaning and shaping will entomb any remaining organisms3 and, with the coronal seal, to prevent recontamination of the canal and periradicular tissues.Endodontic access openings are based on the anatomy and morphology of each individual tooth group. In general, the pulp chamber morphology dictates the design of the access preparation. The internal anatomy is projected onto the external surface. The major objectives of the access openings include (1) locating all canals, (2) straight-line unimpeded access of the instruments in the canals to the apical one third or the first curve (if present), (3) removal of the chamber roof and all coronal pulp tissue, and (4) conservation of tooth structure.Canal Controlled MorphologiesFive major canal controlled morphologies have been identified. They include round, ribbon or figure eight, ovoid, bowling pin, kidney bean, and C-shape. With the exception of the round shape morphologic, each presents unique problems for adequate cleaning and shaping. Figure. Common canal controlled morphologies.A, Round. B, Ribbon-shaped (hourglass). C, Ovoid. D, Bowling pin. E, Kidney bean-shaped. F, C-shaped.General Principles The general principles for endodontic access are outline form, convenience form, caries removal, and toilet of the Cay.Outline form is the recommended shape for access of a normal tooth with radiographic evidence of a pulp chamber and canal space. The outline form assures the correct shape and location and provides straight-line access to the apical portion of the canal or to the first curvature. The access preparation must remove tooth structure that will impede the cleaning and shaping of the canal or canals. The outline form is a projection of the internal tooth anatomy onto the external root structure. The form can change with time. As an example, in anterior teeth with mesial and distal pulp horns the access is triangular. In older individuals with chamber calcification, the pulp horns are absent, so the access is ovoid.Convenience form allows modification of the ideal outline form to facilitate unstrained instrument placement and manipulation. As an example, the use of nickel-titanium rotary instruments requires straight-line access. An access might be modified to permit placement and manipulation of the nickel-titanium instruments. Another example is a premolar exhibiting three roots. The outline form might be made more triangular to facilitate canal location.Caries removal is essential for several reasons. First, removing caries permits the development of an aseptic environment before entering the pulp chamber and radicular space. Second, it allows assessment of restorability before treatment. Third, it provides sound tooth structure so that an adequate provisional restoration can be placed. Unsupported tooth structure is removed to ensure a coronal seal during and after treatment so that the reference point for length determination is not lost should fracture occur.Toilet of the Cay involves preventing the materials and objects from entering the chamber and canal space. A common error is entering the pulp chamber before the coronal structure or restorative materials are adequately prepared. As a result, these materials enter the canal space and may block the apical portion of the canal.Stages of tooth ' Cay disclosure:1. Unroofing of pulp chamber;2. gaining straight-line access to root canal various orifices;3. final habit-forming of carious tooth and Cay Cay '.Access should be designed to reduce the curvature required to negotiate the apical 1/3 of the canal and will involve removal of the entire roof of the pulp chamber, including the pulp horns. The access to Cay in anterior teeth should be midway between the incisal edge and the cingulum, and in posterior teeth will vary according to the anatomy of the pulp chamber (Fig. 1). Lining up a bur with the pre-operative radiograph will help to gauge the depth of preparation. The air turbine handpiece should be used to gain initial access, reverting to slow speed for removal of the roof of the pulp chamber and subsequent preparation. When access is completed, the Cay should have a smooth funnel shape.Tooth ' Cay disclosure of posterior teeth is better to do in the projections of pulp horns, with the round-shaped burs. A shaping of tooth ' Cay walls, with the help of fissure burs are performed. Fig. 1. Diagram that shows the most preferable sites for tooth Cay disclosureOften, in an attempt to preserve tooth structure, the access openings are constricted and underprepared. This creates problems with locating canals and gaining straight-line access. Removal of restorative materials is often warranted, knowing that following treatment they will be replaced. Removal enhances visibility and may reveal undetected canals, caries, or coronal fractures. When difficulties occur with calcifications or extensive restorations, the operator can become disoriented with respect to canal morphology. The discovery of one canal can serve as a reference in locating the remaining canals. A file can be inserted and a radiograph exposed to reveal which canal has been located.Complex restorations, such as crowns and fixed partial dentures, may have changed the coronal landmarks used in canal location. A tipped tooth might be uprighted "or a" rotated tooth "realigned." Loss of orientation can result in the incorrect identification of a canal, and searching for the other canals in the wrong direction results in excessive removal of tooth structure, perforation, or the failure to locate and debride all canals.Access through crowns with extensive foundations may make visibility difficult. Class V restorations may have induced coronal calcification or could have been placed directly into the pulp space or the canals. In some instances, it may be best to remove restorative materials that interfere with visualization before initiating root canal treatment. A modification of the armamentarium for teeth restored with crowns has been advocated for all-ceramic crowns. The initial outline and penetration through the restorative material are made with a round diamond bur in the high-speed handpiece with water coolant. After penetration into dentin, a fissure bur can be used. In teeth with porcelain-fused-to-metal restorations, a metal cutting bur is recommended. When possible, the access should remain in the metal to reduce the potential for fracture in the porcelain. Evidence indicates that with a water coolant and careful instrumentation, diamond and carbide burs are equally effective.In summary, aids in canal location include knowledge of pulp anatomy and morphology; parallel straight-on and angled radiographs/digital images; a sharp endodontic explorer; Interim radiographs/digital images; long-shanked, slow-speed burs; Ultrasonic instruments for troughing; dye staining; irrigation; transillumination; and enhanced vision with loupes or microscopy.ACCESS OPENINGS AND CANAL LOCATIONMaxillary Lateral Incisors Central andThe maxillary central incisor has one root and one canal. In young individuals, the prominent pulp horns present require a triangular-outline form to ensure tissue and obturation materials are removed, which might cause coronal discoloration. While the canal is centered in the root at the cementoenamel junction (CEJ) and when viewing the tooth from a mesial to distal orientation, it is evident that the crown is not directly in line with the long axis of the root. For this reason the establishment of the outline form and initial penetration into enamel are made with the bur perpendicular to the lingual surface of the tooth. This outline form is made in the middle-third of the lingual surface. After penetration to the depth of 2 to 3 mm, the bur is reoriented to coincide with the long axis and lingual orientation of the root. This reduces the risk of a lateral perforation through the facial surface. An additional common error is the failure to remove the lingual shelf, which will result in inadequate access to the entire canal. The canal is located by using a sharp endodontic explorer. In cases where calcification has occurred, long-shanked burs in a slow-speed handpiece can be used. These burs move the head of the handpiece away from the tooth and enhance the ability to see exactly where the bur is placed in the tooth.