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.

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.

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.

Access for the maxillary lateral incisor is similar to that for the central incisor. A triangular access is indicated in young patients with pulp horns, and as the pulp horns recede, the outline form becomes ovoid.

Maxillary Canines

Maxillary canines exhibit one canal in a single root. Generally, pulp horns are absent so the outline form is ovoid in the middle third of the lingual surface. As attrition occurs, the chamber appears to move more incisally because of the loss of structure. In cross-section the pulp will be wide in a faciolingual direction when compared to the mesiodistal dimension.

Maxillary Premolars

 The  maxillary  first  and  second  premolars  exhibit  a  similar  coronal  structure  so  the  outline  form  is  similar  for  both  teeth,  is centered  in  the  crown,  and  exhibits  an  ovoid  shape  in  the  faciolingual  direction.  An  important anatomic consideration with these teeth is the mesial concavity at the CEJ. This is an area in which a lateral perforation is likely  to  occur.  When  two  canals  are  present,  the  canal  orifices  are  located  under  the  buccal  and  lingual  cusp  tips  equal distance from a line drawn through the center of the chamber in a mesial to distal direction. The cross-sectional morphology exhibits a kidney bean– or ribbon-shaped configuration. In rare instances when three canals are present, the outline form is triangular with the base to the facial and the apex toward the lingual.

Maxillary Molars

 The maxillary first and second molars have similar access outline forms. The outline form is triangular and located in the mesial half of the tooth, with the base to the facial and the apex toward the lingual. The transverse or oblique ridge is left mostly intact. The external references for canal location serve as a guide in developing the outline form. The  mesiobuccal  canal  orifice  lies  slightly  distal  to  the  mesiobuccal  cusp  tip.  The  distobuccal  canal  orifice  lies  distal  and slightly lingual to the main mesiobuccal canal and is in line with the buccal groove. The lingual or palatal canal orifice generally exhibits  the  largest  orifice  and  lies  slightly  distal  to  the  mesiolingual  cusp  tip.  The  mesiobuccal  root  is  very  broad  in  a buccolingual direction, thus a small second canal is common. The mesiolingual canal orifice (commonly referred to as the MB2canal) is located lingual to the main mesiobuccal canal (MB1 canal) from 1 to 3 mm and is slightly mesial to a line drawn from the mesiobuccal to the lingual or palatal canal. The initial movement of the canal from the chamber is ofteot toward the apex but laterally toward the mesial. Removal of the coronal dentin (cornice) in this area permits exposure of the canal as it begins to move apically and facilitates negotiation. In addition, the operating microscope is a valuable aid.

Mandibular Central and Lateral Incisors

 The mandibular incisors are narrow in the mesiodistal dimension and broad faciolingually. There may be one canal with an ovoid or ribbon-shaped configuration or there can be two canals. When there are two canals, the facial canal is easier to locate and is generally straighter than the lingual canal, which is often shielded by a lingual shelf. Since the tooth is often tipped facially, the lingual canal is difficult to locate and perforations primarily occur on the facial surface. The  narrow  mesiodistal  dimension  of  these  teeth  makes  access  and  canal  location  difficult.  In  young patients  with mesiodistal pulp horns the outline form is triangular with the base incisally and the apex gingivally. As the pulp recedes over time and the pulp horns disappear, the shape becomes more ovoid. The access is positioned in the middle-thirds of the lingual surface.  Because  of  the  small  size  of  these  teeth  and  the  presence  of  mesiodistal  concavities, access must be precisely positioned. The initial outline form is established into dentin with the bur perpendicular to the lingual surface. When a depth of 2 to 3 mm is reached, the orientation of the bur is reoriented along the long axis of the root. Because the percentage of teeth with two canals is reported to be 25% to 40%,41,42 the lingual surface of the chamber and canal must be diligently explored with a small precurved stainless steel file. A Gates-Glidden drill is used on the lingual to remove the dentin shelf.

In  cases  of  attrition,  the  access  moves  toward  the  incisal  surface.  With  the  use  of  nickel-titanium  rotary instruments, straight-line access is imperative. A more incisal approach on the lingual or facial surface is justified. A modification of the access for the incisors is a facial approach.44 This provides better visibility and can be employed when there is crowding or when the canal is receded below the CEJ.

Mandibular Canines

The mandibular canines usually exhibit a long slender crown when compared to the maxillary canine, which is shorter and wider in a mesiodistal direction. The tooth may exhibit one or two roots. The root is broad in a faciolingual dimension and therefore may contain two canals. The outline form is ovoid and positioned in the middle-third of the crown on the lingual surface. On  access  opening  into  the  chamber,  the  lingual  surface  should  be  explored  for  the presence of a lingual canal. As attrition occurs, the access will need to be more incisal, and in severe cases, it may actually include the incisal edge of the tooth.

Mandibular Premolars

The mandibular premolars appear to be easy teeth to treat, but the anatomy may be complex. One, two, or three roots are possible, and canals often divide deep within the root in these complex morphologic configurations. The crown of the first premolar exhibits a prominent buccal cusp and a vestigial lingual cusp. In addition, there is a lingual constriction. Mesiodistal projections reveal that the chamber and canal orifice are positioned buccally. The access is therefore ovoid in a buccolingual dimension and positioned buccal to the central groove. It extends just short of the buccal cusp tip. The mandibular second premolar has a prominent buccal cusp, but the lingual cusp can be more prominent than with the first premolar. There is also a lingual constriction, so the outline form is ovoid from buccal to lingual and positioned.

Mandibular Molars

The  mandibular  molars  are  similar  in  anatomic  configuration;  however,  there  are  subtle  differences.  The  most  common mandibular first molar configuration is two canals in the mesial root, although three have been reported, and one canal in the distal root. The presence of a second canal in the distal root is 30% to 35%. The roots often exhibit a kidney bean shape in cross-section with the concavity in the furcal region. The most common configuration for the mandibular second molar is two canals in the mesial root and one canal in the distal root. The incidence of four canals is low.

The coronal reference points for canal location in the mandibular molar roots are influenced by the position of the crown on the root and by the lingual tipping of these teeth in the arch. The mesiobuccal canal orifice is located slightly distal to the mesiobuccal cusp tip. The mesiolingual canal orifice is located in the area of the central groove area and slightly distal when compared to the mesiobuccal canal. The distal canal is located near the intersection of the buccal, lingual, and central grooves. When a distobuccal canal is present, the orifice can be found buccal to the main distal canal and often is slightly  more  mesial.  The  mandibular  first  molar  may  even  exhibit  a  distinct  separate  extra  distal  root.  Because  of  these anatomic relationships, the access outline form is rectangular or trapezoidal and positioned in the mesiobuccal portion of the crown.

Examples of access openings prepared in extracted teeth are given here. It is important to recognize: (1) the location of the access relative to occlusal or lingual landmarks (marginal ridge and cusp tips) and (2) the size and shape of the access relative to the size and shape of the occlusal or lingual surface.

 

 

Goals of endodontic access

Acces preparation is the most important phase of the technical aspects of root canal treatment. The bulk of procedural errors and treatment difficulties are related to errors or problems in obtaining adequate access (Fig. 2).

Unroofing of the Pulp Chamber

Unroofing the chamber and removing the coronal pulp facilitates the clinician’s ability to visualize the chamber floor and aids in locating the canals. Complete removal of tissue and debris prevents subsequent infection. Unroofing the chamber and removing the coronal pulp (in vital cases) allow the clinician to see the pulpal floor. In cases of observable canals, most or all of the canal orifices may be easily located before the chamber is completely unroofed, but the clinician may however miss canals.

Visualization  of  the  internal  anatomy  is  enhanced  during  access  by  using  a  fiberoptic  handpiece  and  microscopy. Illumination  is  a  key  factor. A  sharp  endodontic  explorer  can  be  used  for  detection  of  the  canal  orifice  or  to  aggressively dislodge calcifications. When a canal is located, a small file or pathfinding instrument (.06, .08, or .10 stainless steel file) is used to explore the canal and determine patency close to the apical foramen. Care should be exercised during this process to prevent  forcing  tissue  apically,  which  might  result  in  canal  blockage.  This  procedure  is  performed  in  the presence of irrigant or lubricant.

Figure. A, Maxillary first molar exhibits extensive mesial caries. B, Histologic section of pulp tissue from the palatal canal reveals extensive

calcification. Early canal exploration should be done with small files to prevent forcing the tissue and calcification apically and blocking the canal.

 

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.

 

   

Figure. Access preparation of maxillary molar

 A, Maxillary left first molar. Note the calcification in the chamber. B, The outline form established and dentin removed apically in layers. C, Exposure of the pulp horns.

D, The use of a Mueller bur to completely unroof the chamber. Note the visibility and ability for precise removal of dentin. E, The completed access. The mesiobuccal canal is evident under the mesiobuccal cusp tip, the distobuccal canal is found opposite the buccal groove and slightly lingual to the main mesiobuccal canal, and the palatal canal is located under the mesiolingual cusp tip. Note the identification of the mesiolingual canal (arrow). F, Removal of the dentinal cornice that covers the mesiolingual canal to reveal the canal orifice.

The ideals of endodontic access are as follows:

1.                       Complete removal of the chamber roof

2.                       Removal of coronal pulp

3.                       Straight-line access to facilitate placement of endodontic instruments.

During  the  access  preparation,  the  cervical  bulge  that  overlies  the  canal  orifices  of  the  mesiobuccal  and  mesiolingual canals  is  removed,  which  permits  straight-line  access  to  the  first  curve  or  apical  portion  of  the  root  by decreasing the emergence profile. This also enhances entry into the canals.

 

Figure.  Basic steps in access preparation.

A, The access cavity is outlined deep into dentin and close to the estimated depth of access with the high-speed handpiece. B, Penetration and unroofing are achieved by fissure high-speed bur or slow-speed latch-type burs. Other bur configurations are acceptable. C, Canal orifices are located and identified with an endodontic explorer. Small files are used to negotiate to the estimated working length. D, The dentin shelf that overlies and obscures the orifices is removed.

Facilitation of Instrument Placement

Although contemporary endodontic techniques require fewer instruments, the overall thrust of endodontic cleaning and shaping continues to be the serial placement into the root canal system of variably sized, tapered, or shaped instruments. This serial placement of instruments is greatly facilitated by spending a few extra minutes on the access preparation.

  Common terms and expressions used for endodontic disease conditions and treatment procedures

 

Pulpitis  Inflammation of the dental pulp. Symptomatic and asymptomatic pulpitis, as well as irreversible and reversible pulpitis, are commonly used terms to specify lesions with and without painful symptoms. The terms total and partial pulpitis are also in use.

Pulp necrosis.  Pulp death. Pulp chamber is without of a functional pulp tissue. Necrosis can be more or less complete, i.e. partial or total.

Apical periodontitis.  An inflammatory reaction of the tissues surrounding the root apex of a tooth. Symptomatic/asymptomatic apical periodontitis and acute/chronic apical periodontitis, respectively, are applied to indicate lesions with and without overt clinical symptoms such as pain, swelling and tenderness. Dental or apical granuloma is a histological term for an established lesion. Apical, periapical and periradicular are interchangeable terms to state the location of the process at or near the root tip.

Pulp capping (lining placing)   Treatment procedure aimed at preserving a dental pulp that has been exposed to the oral environment.

Partial pulpotomy   Treatment procedure by which the most (often inflamed) superficial portion (1–2 mm) of the coronal pulp is surgically removed with the aim of preserving the remaining tissue.

Pulpotomy (amputation)   Treatment procedure by which the coronal pulp tissue is surgically removed with the aim of preserving the remaining tissue. The term pulpotomy is also used to describe a pain-relieving procedure in an emergency treatment of symptomatic pulpitis.

Pulpectomy (extirpation)   Treatment procedure by which entire pulp tissue (often inflamed) is surgically removed and replaced with a root filling.

(RCT)  Root canal treatment   Treatment of teeth with necrotic pulps where root canals are often infected.

Non-surgical retreatment    Treatment of root filled teeth with clinical and/or radiographic signs of root canal infection, where root fillings are removed, canals disinfected and refilled. May also be carried out to improve the technical quality of previous root fillings.

Surgical retreatment   Treatment procedure by which the root apex of a tooth is surgically accessed to manage a root canal infection that has not been successfully treated by RCT. Retrograde endodontics or surgical endodontics are other terms for this procedure.

Apexification – treatment procedure by which closure of root apex is promoted by calcium hydroxide, in teeth where loss of vitality has occurred before normal growth and development of the tooth was completed.

Apexogenesis – treatment procedure by which the preservation of the radicular pulp tissue allows continuing development and apical maturation of teeth with open apices.

Traditional discussions of canal preparation have recognized cleaning and shaping as two distinct processes. Cleaning –refer to the debridement of the root canal space and shaping as the step to prepare the canal for obturation. All clinically accepted endodontic instruments and instrumentation techniques attempt to perform both processes simultaneously.

Debridement of the root canal space includes removal of vital and necrotic tissue, bacteria, bacterial byproducts, and dentinal debris created during the cleaning and shaping process. Irrigation and disinfection are integral parts of debridement.

PRINCIPLES OF SHAPING 

The purpose of shaping is to facilitate cleaning and provide space for placing the obturating materials. The main objective of shaping is to maintain or develop a continuously tapering funnel from the canal orifice to the apex. This decreases procedural errors when enlarging apically. The degree of enlargement is often dictated by the method of obturation. For lateral compaction of  gutta–percha,  the  canal  should  be  enlarged  sufficiently  to  permit  placement  of  the  spreader  to  within  1  to  2  mm  of  the corrected working length. There is a correlation between the depth of spreader penetration and the quality of the apical seal. For warm vertical compaction techniques, the coronal enlargement must permit the placement of the pluggers to within 3 to 5 mm of the corrected working length. As  dentin  is  removed  from  the  canal  walls,  the  root  is  weakened. The  degree  of  shaping  is  determined  by  the preoperative  root  dimension,  the  obturation  technique,  and  the  restorative  treatment  plan.  Narrow  thin  roots,  such  as  the mandibular incisors, cannot be enlarged to the same d Cleaning and shaping are separate and distinct concepts but are performed concurrently. The criteria of canal preparation include developing a continuously tapered funnel, maintaining the original shape of the canal, maintaining the apical foramen in its original position, keeping the apical opening as small as possible, and developing glassy smooth walls.6 The cleaning and shaping  procedures  are  designed  to  maintain  an  apical  matrix  for  compacting  the  obturating  material  regardless  of  the obturation technique. Knowledge of a variety of techniques and instruments for treatment of the myriad variations in canal anatomy is required. There is no consensus on which technique or instrument design or type is clinically superioregree as more bulky roots such as the maxillary central incisors. Post placement is also a determining factor in the amount of coronal dentin removal.

 

Manipulations of root canal treatment (RCT) are carried out manually or with the help of rotary instruments by several treatment methods, the most widespread  among them are:

•              apical-crown – envisage treatment from the apical hole to canal orifices with gradually increasing of  instrument diameter( e.g. from №10 -№ 40)

•              crown-apical – envisage root canal treatment that starts from canal orifices to apical hole with a gradual decrease in instrument diameter(e.g. from №40 –№ 10)

•              hybrid method of treatment – have been developed out of the two methods. Starting coronally with larger instruments, often power driven, one works down the straight portion of the canal with progressively smaller instruments, that is the crown-down approach. Then at this point, the procedure is reversed, starting at the apex with small instruments, and gradually, increasing in size as one works back up the canal, that is the ‘step-back’ approach. This hybrid approach could be called the crown-down – step-back technique or ‘modified double-flared technique’.

 

 

Step-back technique. (Fig. 3, 4)An apical part of the root canal is prepared first and the canal is then widened from apex to crown. Blockage of canals may occur using this technique, and irrigation can be difficult. After determining the WL, the first active instrument to be inserted should be fine (№ 08, 10 or 15) 0,02 tapered, stainless steel file, curved and coated with lubricant. The most important part of the Step-back preparation is the reuse of files; one size smaller than the last one (recapitulation) used to prevent dentine shavings from building up and causing blockage of the canal. Irrigation alone may not be efficient in these cases for preventing clogging. Once the apical preparation is complete № 2 or 3 Gates Glidden are used to further funnel the preparation coronally.

 

 

An example of step-back preparation in a moderately curved canal.

 

 

Crown-down technique. (Fig. 5) At first (along with several others) prepares the coronal part of the canal before the apical part. This has advantages and is the preferred technique. Initially H-file № 15, 20 is penetrated root canal; then Gates Glidden drills (№2, 3), flaring the coronal segment of root canal is used; determination of the WL and creation of an apical stop; then shaping the remaining canal in crown-down approach, using decreasing size of instruments in sequence.

 

Anticurvature filing.  It was developed to minimize the possibility of creating a ‘strip’ perforation on the inner walls of curved root canals. It is used in conjunction with other techniques or preparation, and the essential principle is the direction of most force away from the curvature. The walls on the opposite side from the curve are instrumented more than the inner walls resulting in a decrease of the overall degree of canal curvature. Bottom Line: Anti-curvature approach can preserve dentinal thickness near furcation. It also gives a more straight line access deeper into the canal.

Balanced force technique. (Fig. 6) It’s involves using blunt-tipped files with an anticlockwise rotation whilst applying an apically directed force. It requires practise to master but is particularly useful when preparing the apical part of severely curved canals.

 

The balanced force technique recognizes the fact that instruments are guided by the canal walls when rotated. Because the files  will  cut  in  both  a  clockwise  and  counterclockwise  rotation,  the  balanced  force  concept  of  instrumentation  consists  of placing  the  file  to  length  and  then  a  clockwise  rotation  (less  than  180  degrees)  engages  dentin.  This  is  followed  by  a counterclockwise  rotation  (at  least  120  degrees)  with  apical  pressure  to  cut  and  enlarge  the  canal.  The  degree  of  apical pressure varies from light pressure with small instruments to heavy pressure with large instruments. The clockwise rotation pulls  the  instrument  into  the  canal  in  an  apical  direction.  The  counterclockwise  cutting  rotation  forces  the  file  in  a  coronal direction while cutting circumferentially. After the cutting rotation, the file is repositioned and the process is repeated until the corrected working length is reached. At this point, a final clockwise rotation is employed to evacuate the debris.

Advantages of orifice enlargement (Fig. 7)

Effectively, ⇓ the curvature in the coronal part of the root canal, allowing straighter access for files to the apical region. It therefore reduces the possibility of apical transportation (zipping). 

It allows improved access for the flow of irrigant solution within the canal. 

It reduces the probability of apical extrusion of infected material as most of the canal debris is removed before apical instrumentation takes place. This is particularly important because the majority of bacteria of an infected root canal are located in the coronal region.

 

General Considerations of shaping and cleaning root canals

 

The following principles and concepts should be applied regardless of the instruments or technique selected:

1. Initial canal exploration is always performed with smaller files to gauge canal size, shape, and configuration.

2. Files are always manipulated in a canal filled with an irrigant or lubricant present.

3. Copious irrigation is used between each instrument in the canal.

4. Coronal preflaring (passive step-back technique) with hand instruments will facilitate placing larger working length files (either hand or rotary) and will reduce procedural errors such as loss of working length and canal transportation.

5. Apical canal enlargement is gradual, using sequentially larger files from apical to coronal, regardless of flaring technique.

6. Debris is loosened and dentin is removed from all walls on the outstroke (circumferential filing) or with a rotating (reaming) action at or close to working length.

7. Instrument binding or dentin removal on insertion should be avoided. Files are teased to length using a watch-winding or “twiddling” action. This is a back-and-forth rotating motion of the files (approximately a quarter turn) between the thumb and forefinger, continually working the file apically. Careful file insertion (twiddling) followed by planing on the outstroke will help to avoid apical packing of debris and minimize extrusion of debris into the periradicular tissues.

8. Reaming is defined as the clockwise rotation of the file. Generally, the instruments are placed into the canal until binding is encountered. The instrument is then rotated clockwise 180 to 360 degrees to cut and plane the walls. When withdrawn, the instrument tip is pushed alternately against all walls. The pushing motion is analogous to the action of a paintbrush. Overall, this is a turn and pull.

9. Filing is defined as placing the file into the canal and withdrawing it along the path of insertion to scrape the wall. There is very little rotation on the outward cutting stroke. The scraping or rasping action removes the tissue and cuts superficial dentin from the canal wall.

10. Turn-pull filing involves placing the file into the canal until binding. The instrument is then rotated to engage the dentin and withdrawn with lateral pressure against the canal walls.

11. Circumferential filing is used for canals that exhibit cross-sectional shapes that are not round. The file is placed into the canal and withdrawn in a directional manner against the mesial, distal, buccal, and lingual walls.

12. Regardless of the technique, after each insertion the file is removed and the flutes are cleaned of debris; the file can then be reinserted into the canal to plane the next wall. Debris is removed from the file by wiping it with an alcohol-soaked gauze or a cotton roll.

13. The canal is effectively cleaned only where the files actually contact and plane the walls. Inaccessible regions are poorly debrided.

14. Recapitulation is done to loosen debris by rotating the MAF or a smaller size at the corrected working length followed by irrigation to mechanically remove the material. During recapitulation, the canal walls are not planed and the canal should not be enlarged.

15. Small, long, curved, and round canals are the most difficult and tedious to enlarge. They require extra caution during preparation because they are the most prone to loss of length and transportation.

16. Overenlargement of curved canals by files attempting to straighten themselves will to lead to procedural errors.

17. Overpreparation of canal walls toward the furcation may result in a stripping perforation in the danger zone where root dentin is thinner.

18. It is neither desirable nor necessary to try to remove created steps or other slight irregularities created during canal preparation.

19. Instruments, irrigants, debris, and obturating materials should be contained within the canal. These are all known physical or chemical irritants that will induce periradicular inflammation and may delay or compromise healing.

20. Creation of an apical stop may be impossible if the apical foramen is already very large. An apical taper (seat) is attempted but with care. Overusing large files aggravates the problem by creating an even larger apical opening.

21. Forcing or locking (binding) files into dentin produces unwanted torsional force. This tends to untwist or wrap-up or will weaken and break the instrument.

 

CRITERIA FOR EVALUATING CLEANING AND SHAPING

 

After cleaning and shaping procedures, the canal should exhibit “glassy smooth” walls and there should be no evidence of dentin filings, debris, or irrigant in the canal. This is determined by pressing the MAF against each wall in an outward stroke. Shaping  is  evaluated  by  assessing  the  canal  taper  and  identifying  the  apical  configuration.  For  obturation  with  lateral compaction,  the  finger  spreader  should  go  loosely  to  within  1  mm  of  the  corrected  working  length.  For  warm  vertical compaction, the plugger should reach to within 5 mm of the corrected working length (Figure 15-26).

 

Figure 15-26. The coronal taper is assessed using the spreader or plugger depth of penetration.

A, With lateral compaction, a finger spreader should fit loosely 1.0 mm from the corrected working length with space adjacent to the spreader.

B, For warm vertical compaction, the plugger should go to within 5.0 mm of the corrected working length.

 

The apical configuration is identified as an apical stop, apical seat, or open. This is accomplished by placing the MAF to the corrected working. If the MAF goes past the corrected working length, the apical configuration is open. If the MAF stops at the corrected working length, a file one or two sizes smaller is placed to the corrected working length. If this file stops, the apical configuration is a stop. When the smaller file goes past the corrected working length, the apical configuration is a seat.

 

PRINCIPLES OF CLEANING

 

Nonsurgical root canal treatment is a predictable method of retaining a tooth that otherwise would require extraction. Success of root canal treatment in a tooth with a vital pulp is higher than that of a tooth that is necrotic with periradicular pathosis. The difference is the persistent irritation of necrotic tissue remnants and the inability to remove the microorganisms and their by-products.  The  most  significant  factors  affecting  this  process  are  tooth  anatomy  and  morphology  and  the  instruments  an irrigants available for treatment. Instruments must contact and plane the canal walls to debride the canal. Morphologic factors include lateral and accessory canals, canal curvatures, canal wall irregularities, fins, and isthmuses. These aberrations make total dйbridement virtually impossible. Therefore, the objective of cleaning is to reduce the irritants, not totally eliminate them.

 Currently, there are no reliable methods to assess cleaning. 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 dйbridement. Obtaining glassy smooth walls is a preferred indicator. The properly prepared canals should feel smooth in all dimensions when the tip of a small file is pushed against the canal walls. This indicates that files have had contact and planed all accessible canal walls, thereby maximizing dйbridement (recognizing that total debridement usually does not occur).

 

Passing and enlargement of root canal (especially narrow and sclerosed) is not always possible to implement using only endodontic instruments. In such cases, additional chemical expansion is conducted. Such technique involves the use of different types of acids for decalcification of dentin.

 

LUBRICANTS

Lubricants facilitate file manipulation during cleaning and shaping. They are an aid in initial canal negotiation, especially in small constricted canals without taper. They reduce torsional forces on the instruments and decrease the potential for fracture. Glycerin is a mild alcohol that is inexpensive, nontoxic, aseptic, and somewhat soluble. A small amount can be placed along the shaft of the file or deposited in the canal orifice. Counterclockwise rotation of the file carries the material apically. The file can then be worked to length using a watch winding or “twiddling” motion. Paste lubricants can incorporate chelators. One advantage to paste lubricants is that they can suspend dentinal debris and prevent apical compaction. One proprietary product consists of glycol, urea peroxide, and ethylenediaminetetraacetic acid (EDTA)  in  a  special  water-soluble  base.  It  has  been  demonstrated  to  exhibit  an  antimicrobial  action.  Another  type  is composed of 19% EDTA in a water-soluble viscous solution. A disadvantage to these EDTA compounds appears to be the deactivation of NaOCl by reducing the available chlorine and potential toxicity. The addition of EDTA to the lubricants has not proved to be effective. In general, files remove dentin faster than the chelators can soften the canal walls. Aqueous solutions, such as NaOCl, should be used instead of paste lubricants when using nickel-titanium rotary techniques to reduce torque.

 

SMEAR LAYER

 

During the cleaning and shaping, organic pulpal materials and inorganic dentinal debris accumulate on the radicular canal wall, producing an amorphous, irregular smear layer. With pulp necrosis, the smear layer may be contaminated with bacteria  and  their  metabolic  by-products.  The  smear  layer  is  superficial,  with  a thickness of 1 to 5 μm, and debris can be packed into the dentinal tubules in varying distances.

Figure.  A, A canal wall with the smear layer present. B, The smear layer removed with 17% EDTA.

 

There is not a consensus on removing the smear layer before obturation. The advantages and disadvantages of the smear  layer  removal  remain  controversial;  however,  evidence  generally  supports  removing  the  smear  layer  prior  to obturation. The organic debris present in the smear layer might constitute substrate for bacterial growth, and it has been suggested  that  the  smear  layer  prohibits  sealer  contact  with  the  canal  wall,  which  permits  leakage.  In  addition,  viable microorganisms in the dentinal tubules may use the smear layer as a substrate for sustained growth. When the smear layer is not removed, it may slowly disintegrate with leaking obturation materials, or it may be removed by acids and enzymes that are produced by viable bacteria left in the tubules or that enter via coronal leakage. The presence of a smear layer may also interfere with the action and effectiveness of root canal irrigants and interappointment disinfectants.

With smear layer removal, filling materials adapt better to the canal wall. Removal of the smear layer also enhances the adhesion of sealers to dentin and tubular penetration and permits the penetration of all sealers to varying depths. Removal of the smear layer reduces both coronal and apical leakage.

 

DECALCIFYING AGENTS

EDTA

Removal of the smear layer is accomplished with acids or other chelating agents such as ethylenediamine tetraacetic acid (EDTA)  after  cleaning  and  shaping.  Irrigation  with  17%  EDTA  for  1  minute  followed  by  a  final  rinse  with  NaOCl  is  a recommended method. Chelators remove the inorganic components and leave the organic tissue elements intact. NaOCl is theecessary for removal of the remaining organic components. Citric acid has also been shown to be an effective method for removing the smear layer, as has tetracycline. Demineralization results in removal of the smear layer and plugs and enlargement of the tubules. The action is most effective in the coronal and middle thirds of the canal and reduced apically. Reduced activity may be a reflection of canal size or anatomic variations such as irregular or sclerotic tubules. The variable structure of the apical dentin presents a challenge during endodontic obturation with adhesive materials. The recommended time for removal of the smear layer with EDTA is 1 minute. The small particles of the smear layer are primarily inorganic with a high surface to mass ratio, which facilitates removal by acids and chelators. EDTA exposure over 10 minutes causes excessive removal of both peritubular and intratubular dentin.

For chemical enlargement of a root canal a small amount of gel product is applied to endodontic instruments and instrumental treatment of root canal is performed. The procedure is repeated several times. After obtaining the required result, canal is washed with solution of sodium hypochlorite or distilled water.

 

Drugs for chemical enlargement of root canals

 

Root canal treatment should include thorough instrumental debridement and medicament treatment as well (antiseptic solutions), these two procedures should go together.

 

IRRIGANTS.

These are required to flush out debris and lubricate instruments. Dilute sodium hypochlorite is generally considered to be the best irrigant as it is bactericidal and dissolves organic debris. The normal concentration is 2.5% available chlorine. Chelating agents which soften dentine by their demineralizing action are particularly helpful when trying to negotiate sclerosed or blocked canals. It is recommended to coat instrument in antiseptic solution every time it is inserted into root canal, because irrigants not only cleans the root canal, but also dissolves flakes of debris on the working part of instrument.

Irrigation does not completely debride the canal. NaOCl will not remove tissue from areas that are not touched by files. In fact, no techniques appear able to completely clean the root canal space. Frequent irrigation is necessary to flush and remove the debris generated by the mechanical action of the instruments.

Solutions that can be used as irrigants in medicament treatment of root canals: 3% sodium hypochlorite sol., 0,2% chlorhexidini, 1% sol. Chloramine, 2-5% Iodide sol., 3% H₂O₂ , Dikamfen, Formokrezol (used for antiseptic treatment of root canals in the case of apical periodontitis)

INTRACANAL MEDICAMENTS

 Intracanal  medicaments  have  a  long  history  of  use  as  interim  appointment  dressings.  They  have  been  employed  for  the following three purposes: (1) to reduce interappointment pain, (2) to decrease the bacterial count and prevent regrowth, and (3) to render the canal contents inert. Some common agents are listed in Box 1 below.

Box.1  Groupings of Commonly Used Intracanal Medicaments

Phenols and Aldehydes

The  majority  of  the  medicaments  exhibit  nonspecific  action  and  can  destroy  host  tissues,  as  well  as  microbes. Historically, it was thought that these agents were effective, although their use was based on opinion and empiricism. The phenols and aldehydes are toxic, and the aldehydes are fixative agents. When placed in the radicular space, they have access to the periradicular tissues and the systemic circulation.  Research has demonstrated that their clinical use is not justified.  Clinical studies assessing the ability of these agents to prevent or control interappointment pain indicate that they are not effective.

Corticosteroids

 Corticosteroids  are  antiinflammatory  agents  that  have  been  advocated  for  decreasing  postoperative  pain  by  suppressing inflammation. The use of corticosteroids as intracanal medicaments may decrease lower-level postoperative pain in certain situations; however, evidence also suggests that they may be ineffective, particularly with greater pain levels. Cases of irreversible pulpitis and cases in which the patient is experiencing acute apical periodontitis are examples where steroid use might be beneficial.

Sodium Hypochlorite

The most common irrigant is NaOCl, which is also known as household bleach. Advantages to NaOCl include the mechanical flushing of debris from the canal, the ability of the solution to dissolve vital and necrotic tissue, the antimicrobial action of the solution, and the lubricating action. In addition, it is inexpensive and readily available. Free  chlorine  in  NaOCl  dissolves  necrotic  tissue  by  breaking  down  proteins  into  amino  acids.  There  is  no  proven appropriate concentration of NaOCl, but concentrations ranging from 0.5% to 5.25% have been recommended. A common concentration is 2.5%, which decreases the potential for toxicity yet still maintains some tissue dissolving and antimicrobial activity. Because the action of the irrigant is related to the amount of free chlorine, decreasing the concentration can be compensated by increasing the volume. Warming the solution can also increase the effectiveness of the solution. However, NaOCl has limitations to tissue dissolution in the canal, because of limited contact with tissues in all areas of the canal. Because of toxicity, extrusion is to be avoided. The irrigating needle must be placed loosely in the canal (Figure 15-6). Insertion to binding and slight withdrawal minimizes the potential for possible extrusion of sodium hypochlorite in periradicular tissues. Special care should be exercised when irrigating a canal with an open apex. To control the depth of insertion the needle is bent slightly at the appropriate length or a rubber stopper is placed on the needle.

Figure 15-6 For effective irrigation the needle must be placed in the apical one-third of the root and must not bind.

 

Chlorhexidine

 Chlorhexidine has recently been advocated as an intracanal medicament. A 2% gel is recommended. It can be used alone in gel form or mixed with calcium hydroxide. When used with calcium hydroxide, the antimicrobial activity is greater than when calcium hydroxide is mixed with saline, and periradicular healing is enhanced.  Chlorhexidine possesses a broad spectrum of antimicrobial activity, provides a sustained action, and has little toxicity. Two  percent  chlorhexidine  has  similar  antimicrobial  action  as  5.25%  NaOCl  and  is  more  effective  against Enterococcus faecalis.  NaOCl  and  chlorhexidine  are  synergistic  in  their  ability  to  eliminate  microorganisms.  A  disadvantage  of chlorhexidine is its inability to dissolve necrotic tissue and remove the smear layer.

Calcium Hydroxide

One intracanal agent that is effective in inhibiting microbial growth in canals is calcium hydroxide. Calcium hydroxide has antimicrobial activity that is a result of the alkaline pH, and it may aid in dissolving necrotic tissue remnants and bacteria and their by-products. Interappointment calcium hydroxide in the canal demonstrates no pain-reduction effects. Calcium hydroxide has been recommended for use in teeth with necrotic pulp tissue and bacterial contamination. It probably has little benefit with vital pulps. Calcium hydroxide can be placed as a dry powder; as a powder mixed with a liquid such as local anesthetic solution, saline, water, or glycerin to form a thick paste; or as a proprietary paste supplied in a syringe (Figure 15-27).  A  lentulo  spiral  is  effective  and  efficient  for  placement.  Spinning  the  paste  into  the  canal  by  rotating  a  file counterclockwise and using an injection technique is not as effective. It is important to place the material deeply and densely for  maximum  effectiveness.  To  accomplish  this,  straight-line  access  with  Gates-Glidden  drills  or  nickel-titanium  rotary  files should  be  performed  and  the  apical  portion  of  the  canal  prepared  to  a  No.  25  file  or  greater.  Removal  after  placement  is difficult, and this is especially true in the apical portion of the root.

 

Figure 15-27 Calcium hydroxide placement. A, Calcium hydroxide mixed with glycerin to form a thick paste. B, Placement with a lentulo spiral. C,

Injection of a proprietary paste. D, Compaction of calcium hydroxide powder with a plugger.

 

DELIVERY OF IRRIGANTS

Syringe

Commercial endodontic syringes have a fine bore to allow delivery of irrigant into the apical part of the root canal system. Gauge 27 needles are manufactured with a cut away tip to allow irrigant to pass out sideways and reduce the risk of apical extrusion.

Intracanal medicaments are advocated to:

• Eliminate bacteria after chemomechanical instrumentation

• Reduce inflammation of the periapical tissues

• Dissolve remaining organic material

• Counteract coronal microleakage.

 

Prepared root canal for sealing, regardless of the method of instrumental treatment, must fulfill the following criteria as follows:

– To be sufficiently enlarged;

– To have a conical shape;

– To have formed an apical stop;

– Do not contain a necrotic dentin;

– Do not have typical smell (when it was apical periodontitis);

– To be cleaned and dried;

– Do not have a painful reaction to percussion (when it was apical periodontitis).

 

 

COMMON ERRORS IN CANAL PREPARATION

Loss of working length has several causes, including failure to have an adequate reference point from which the corrected working length is determined, packing tissue and debris in the apical portion of the canal, ledge formation, and inaccurate measurements of files.

 

Errors in access:

■ Inadequate Preparation

Errors in access preparations are varied. A  common  error  is  inadequate  preparation,  which  has  several significant consequences. Direct effects are decreased access and visibility, which prevents locating the canals. The ability to remove the coronal pulp tissue and subsequent obturation materials is limited, and straight-line access cannot be achieved. Inadequate  straight-line  access  can  indirectly  lead  to  errors  during  the  cleaning  and  shaping.  When  files  are  deflected  by coronal interferences, procedural errors, such as loss of working length, apical transportation, ledging, and apical perforation, are likely in curved canals. A No. 25 file or above has a straightening force that overcomes the confining resistance of the dentin wall. The file cuts on the outer surface apical to the curvature and the inner wall coronal to the curve. Adequate straight-line access decreases the canal curvature and reduces the coronal interferences, allowing the instrument to work more freely in the canal.

■ Excessive Removal of Tooth Structure

 The  excessive  removal  of  tooth  structure  has  direct  consequences  and  unlike  inadequate  preparation  is  irreversible  and cannot be corrected. A minimum consequence is weakening the tooth and subsequent coronal fracture. Evidence indicates that appropriate access and strategic removal of tooth structure that does not involve the marginal ridges will not significantly weaken  the  remaining  coronal  structure.48  The  marginal  ridges  provide  the  faciolingual  strength  to  the  crown;  access openings do not require removal of tooth structure in this area. The ultimate result of removing excessive tooth structure is perforation. Perforations in single-rooted teeth are located on the lateral surface. In multirooted teeth, perforations may be lateral or furcal.

 

► Incomplete debridement: short working length, missed canals. 

► Lateral perforation: often occurs as a result of poor access. (Fig. 8)

► Apical perforation: makes filling difficult. (Fig. 8)

► Ledge formation: can be very difficult to bypass.

► Apical transportation (zipping) (Fig. 8) A file will tend to straighten out when used in a curved canal and straightening can transport the apical part of the preparation away from the curvature. The use of flexible files reduces the likelihood of this happening.  Apical transportation and zipping occur when the restoring force of the file exceeds the threshold for cutting dentin in a cylindrical nontapering curved canal (Figures 15-9  and 15-10). When this apical transportation continues with larger and larger  files,  a  “teardrop”  shape  develops  and apical perforation  can  occur  on  the  lateral  root  surface  (see Figure  15-9). Transportation in curved canals begins with a No. 25 file. Enlargement of curved canals at the corrected working length beyond a No. 25 file can be done only when an adequate coronal flare is developed.

 

Figure 15-9.  Procedural errors of canal transportation, zipping and strip perforation, occur during standardized preparation when files remove

dentin from the outer canal wall apical to the curve and from the inner wall coronal to the curve. This is related to the restoring force (stiffness) of the

files. Note in the apical portion the transportation takes the shape of a tear drop as the larger files are used.

 

Figure 15-10.  The canals have been transported, and there are apical perforations.

 

► Elbow formation When apical zipping happens, a narrowing often occurs coronal to this in the canal such that the canal is hourglass in shape. This narrowing is termed an elbow. 

► Strip perforation A perforation occurring in the inner or furcal wall of a curved root canal, usually towards the coronal end.

Figure.  Straight-line access can result in stripping perforations in the furcal areas of molars.

 A, The use of large Gates-Glidden drills and overpreparation has resulted in the stripping perforation. B, Note that the perforation is in the concavity of the furcation.

 

SOME ENDODONTIC PROBLEMS AND THEIR MANAGEMENT

Fractured instruments. Sometimes it is possible to get hold of the fractured portion with a pair of fine mosquitos. If not, insertion of a fine file beside the instrument may dislodge it. Should the fractured piece be lodged in the apical portion of the canal it may be better to fill the canal below it and keep it under observation, resorting to an apicectomy as a last-ditch solution.

Instrument fracture occurs with torsional and cyclic fatigue. Locking the flutes of a file in the canal wall while continuing to rotate the coronal portion of the instrument is an example of torsional fatigue (Figure 15-11). Cyclic fatigue results when strain develops in the metal.

 

 

Fractured instrument removal. Ultrasonic vibration may be used to facilitate fractured instrument removal. The clinician must take care to ascertain the type of metalic obstruction because nickel-titanium (NiTi) and stainless steel respond differently to ultrasonic vibration. Direct ultrasonic vibration causes NiTi to fragment, so the clinician must work carefully around the fragment. Stainless steel is more resistant to vibration and responds to it by subsequently loosening.

Ultrasonic vibration is applied directly to stainless steel files. Fine inserts can be used to work counter-clockwise around broken instruments. This technique often results in an “unscrewing” action that assists in removal.

Recurrent symptoms/intractable infection If thorough cleaning and repeated dressing of the canal with calcium hydroxide are unsuccessful, it may be necessary to do an apicectomy. Do not routinely turn to surgery for failed cases consider retreatment in the first instance.

If careful exploration with a small file is unsuccessful, investigation of the expected position of the canal entrance with a small round bur may help. Once the canal is found, a No. 8 or 10 file should be used to try and negotiate it, using EDTA, File Eze, or RC Prep as a lubricant, and the canal prepared and filled conventionally. Success rates of 80% have been reported for canals that were hairline or undetectable on radiographs. Occasionally, a total blockage of the canal is encountered, in which case the filling is placed to this level and/or an apicectomy done.

Pulp stones in the pulp chamber can usually be flicked out. If they occur in the canal use EDTA and a small file to try and dislodge them.

Figure. Calcifications (pulp stones [or denticles]) are visualized in the chambers.

Their discrete appearance surrounded by radiolucent spaces shows

these calcifications to be natural and not formed in response to irritation.

 

 

Pain following instrumentation. This is usually due to instruments or irrigants, or to debris being forced into the apical tissues. Placement of a small amount of Ledermix(Antibiotic/steroid paste ) in the canal may provide symptomatic relief, but care is required not to breach the apex. Occasionally, an acute flare-up of a previously asymptomatic tooth occurs following initial instrumentation this is called a phoenix abscess. Loss of face is saved by warning patients that this can happen. Affected teeth should be opened and irrigated and if possible resealed. This may need to be repeated after 24-48 h.

Perforations can be iatrogenic or caused by resorption

In the latter case, dressing with non-setting calcium hydroxide may help to arrest the resorption and promote formation of a calcific barrier. Increasingly MTA is being used for the repair of perforations and in surgical endodontics as a retrograde filling material with excellent results. Management of traumatic perforations depends upon their size and position.

Figure A, Extensive internal resorption defect (arrow). B, Four years after treatment. Special cleaning, shaping, and obturating techniques

(lateral condensation plus thermoplasticized) were required, resulting in successful treatment.

 

Pulp chamber floor If small perfortion, one can cover with calcium hydroxide and fill with GP or GI, but if large, hemisection or extraction may be necessary.

Lateral perforation If this occurs near the gingival margin it can be incorporated in the final restoration of the crown, e.g. a diaphragm post and core crown. If in the middle 1/3, the remainder of the canal may be cleaned by passing instruments down the side of the wall opposite the perforation. Then the canal can be filled with GP, using a lateral condensation technique to try and occlude the perforation as well. Larger perforations may require a surgical approach and in multirooted teeth hemisection or extraction may be unavoidable.  

Apical 1/3 It is usually worth trying a vertical condensation technique to attempt to fill both the perforation and the remainder of the canal. If this is unsuccessful an apicectomy will be required.

Ledge formation If this occurs, return to a small file curved at the apex to the working length and use this to try and file away the ledge, using EDTA or RC– Prep as lubricants.

 

Information was prepared by Levkiv M.O.