Obturation Second Lecture PDF

Obturation of The Root Canal System(Part 2) By Mahmoud Ramadan Aboelseoud Lecturer of Endodontics Faculty of Dentistry Alexandria University Outline • Preparation of dentin for obturation (smear layer removal). • Techniques ( Lateral compaction technique). • Lateral condensation step by step. •...

Obturation of The Root Canal System(Part 2) By Mahmoud Ramadan Aboelseoud Lecturer of Endodontics Faculty of Dentistry Alexandria University Outline • Preparation of dentin for obturation (smear layer removal). • Techniques ( Lateral compaction technique). • Lateral condensation step by step. • Correcting obturation errors. • Advantages and disadvantages of lateral condensation. • Evaluation of obturation. Preparation of dentin for obturation • Root canal instrumentation produce a layer of organic and inorganic material called the smear layer that may also contain bacteria and their by- products. • Effect of smear layer on quality of RCT: 1. This layer covers the instrumented walls and may prevent the penetration of intracanal medicaments and sealers into the dentinal tubules 2. May interfere with the close adaptation of root filling materials to canal walls. Thick smear layer covering the canal wall • Components of the smear layer: 1. The smear layer, created by instrumentation, is primarily calcific (inorganic) in nature. 2. There is also an organic component reflecting the chemical composition of dentin. 3. The smear layer , also include bacteria. necrotic tissue and How to remove the smear layer? • Current methods of smear layer removal include: 1. Chemicals (EDTA and sodium hypochlorite solutions). 2. Sonics. 3. Ultrasonics. 4. Laser techniques – none of which are totally effective throughout the length of all canals or are used universally. • The method of choice is the alternate use of EDTA and sodium hypochlorite. • The chelator (EDTA) is very efficient in removing the inorganic (calcium salts) from the smear layer all the way to the apical third. • Sodium hypochlorite is needed to dissolve and remove the organic (dentin matrix, pulp remnants, necrotic and bacterial debris) constituents of the smear. Dentinal tubules cleaned of smear layer and opened following combined use of EDTA and sodium hypochlorite. • When the smear layer is removed, the dentin interface needs only thorough drying to be ready to receive the obturating materials. METHODS OF OBTURATING THE ROOT CANAL SPACE • Over the years, countless ways and materials have been developed to fill prepared canals. • There are the two basic procedures for obturation: I. Lateral compaction of cold gutta-percha II. Vertical compaction of warmed gutta-percha. • Other methods are variations of warmed gutta-percha. lateral Compaction of Cold Guttapercha • Root canal preparation criteria for Lateral condensation: 1. The final canal shape should be a continuous taper that matches the taper of the spreader/ plugger (Outline form) . 2. The apical area of the canal should almost be parallel (Retention form). 3. The selected spreader must reach within 1.0 to 2.0 mm of the working length (Convenience form). 4. An apical stop must be created to resist apically directed condensation (Resistance form). ISO standardized spreaders and matching gutta-percha points. A, Size #25 hand spreader and matching gutta-percha point. B, Size #25 finger spreader and matching gutta-percha point. Instruments and points are color-coded the same. • Lateral condensation is not the technique of choice in preparations that cannot meet these criteria and not all canals can be shaped to meet these criteria. • Example: 1. Teeth with large internal resorption. 2. Teeth with wide open apices. • Before starting the filling process several important steps in preparation must first be completed: 1. Spreader size determination. 2. Primary point and accessory point size determination. 3. Drying the canal. 4. Mixing and placement of the sealer. 1. Spreader size determination • Before trying in the trial point, it is mandatory to fit the spreader to reach to within 1.0 to 2.0 mm of the true working length and to match the taper of the preparation. • Spreaders are available that have been numbered to match the instrument size. • If the spreader taper is greater than the canal taper (Large spreader), there will be an apically directed force during condensation that can result in overfill. • If the taper of the canal is greater than that of the spreader (Small spreader), there is a tendency to displace the master cone coronally during condensation. • Important Note: There is a correlation between the establishment of a higher quality apical seal and the depth of spreader penetration which requires a true tapered preparation that would allow the spreader to nearly reach the apical terminus. • Remember : Length and not size. • Spreaders should always be fit into an empty canal to ensure that the force is absorbed by the gutta-percha and not the canal walls, which could result in root fracture. A spreader is premeasured and placed in the empty canal to verify penetration into the apical 1.0 to 2.0 mm. Condensation at this depth can be achieved with the assurance that the gutta-percha will absorb the pressure and not the canal walls. Spreader fit within 2 mm of the prepared canal without binding. Note the space available adjacent to the spreader. • Note: Spreaders made from nickel-titanium are available and provide increased flexibility, reduced stress, and provide deeper penetration when compared with stainless steel instruments. • NiTi spreaders are recommended in severely curved canals as stainless steel spreaders are stiff and can not penetrate deep inside the root canal. Clinical tip: A spreader size 25 or 30 is suitable to be used in most of the cases regardless of the master cone size. 2. Primary Point (master cone) Size Determination • Gutta-percha points have been standardized in size and shape to match the standardized instrument sizes. • They have even been color-coded to match the instrument’s color. • The primary point should be selected to match the size of the last instrument used at the apex and should be tested in place and confirmed radiographically. • Gutta-percha comes sterilized from the package or it may be sterilized by immersing in 2.5% or 5.25% NaOCl for 1 minute and then 96% ethyl alcohol, 70% isopropyl alcohol or distilled water is used to remove any chloride crystals that form on the GP cones. • Gutta-percha itself does not readily support bacterial growth. • The four methods used to determine the proper fit of the primary point are as follows: 1. Visual test. 2. Tactile test. 3. Patient response. 4. Radiographic test. 1. • Visual Test. To test the point visually, it should be measured and grasped with cotton pliers at a position within 1 mm short of the prepared length of the canal. • The point is then carried into the canal until the cotton pliers touch the external reference point of the tooth. • This master point should always be tried in a wet canal to simulate the lubrication of the sealer. • If the cone shows signs of distortion or buckling upon removal, this means that the cone is small and a larger cone should be selected. Master GP point A cone that appears buckled on the radiograph or upon removal is small and a larger cone should be selected or a new cone is selected and the tip is cut off . • If the point can be pushed to the root end, it might well be pushed beyond into the tissue. • Either the foramen was originally large or it has been perforated. • If the point can be extended beyond the apex, the next larger size point should be tried. • If this larger point does not go into place, the original point may be used by cutting pieces off the tip. • If the cone needs to be cut, this should be done using a scalpel blade on a glass slab to provide a smooth GP surface. • The use of scissors is not recommended as this creates irregularities on the cone tip interfering with the adaptation of the cone to the canal wall. Length-adjusted gutta-percha points. A, Size 30 gutta-percha point shortened with scissors. Distortion prevents proper placement at apical seal. B, Size 30 gutta-percha point trimmed with scalpel, allowing more perfect apical fit.. • If the working length of the tooth is correct and the point goes completely to position, the visual test has been passed. 2. Tactile Test • If the apical 3 to 4 mm of the canal have been prepared with near parallel walls (in contrast to a continuous taper), some degree of force should be required to seat the point, and, once it is in position, a pulling force should be required to dislodge it. • This is known as “tugback” ( resistance upon removal). • Tug-back can be more easily felt with GP cones larger than size 40. • The master GP cone should also show resistance to apical displacement beyond the working length. 3. Patient Response. • Patients who are not anesthetized during the treatment of a nonvital pulp or at the second appointment of a vital pulp may feel the gutta- percha penetrate the foramen. • Adjustments can then be made until it is completely comfortable. • This is a good test when the position of the foramen does not appear to be accurately determined by the radiograph or by tactile sensation. • Note: Pulp remnants from a short preparation will cause a sensation of much greater intensity than periapical tissue. • Granulation tissue( teeth with periapical lesions) may not produce any sensation at all. 4. Radiograph Test • After the visual and tactile tests for the trial point have been completed, its position must be checked by the final test—the radiograph. • The film must show the point extending to within 1 mm from the tip of the preparation. Trial point ( master cone) radiograph • The radiographic adaptation is a better criterion of evaluation than either the visual or tactile method. • The trial point radiograph presents the final opportunity to check all the previous steps of the root canal treatment. • It will show : a. If the working length of the tooth was correct. b. If instrumentation followed the curve of the canal. c. If a perforation developed. d. The relationship of the initial filling point to the preparation. Important: • If the radiograph shows that the point was forced beyond the apex, an incorrect working length has been used during instrumentation, and the operator may have wondered why the patient complained of discomfort. • The overextended point should always be shortened from the fine end and then carefully returned to proper position. • It should never be just pulled back to a new working length, in which case it would be loose in the canal. • In this new position, it should again pass the tactile and radiographic tests of trial points. It should never be manipulated so that it just appears to fit in the film. • It must fit tightly and come to a dead stop. Important Clinical Tip: • Sometimes the initial point will not go completely into place even though it is the same size as the last enlarging instrument. This condition may arise because: (1) The enlarging instrument (master apical file) was not used to its fullest extent (loose in the canal). (2) Deviation between the sizes of instruments and gutta-percha. (3) Debris remaining in the canal or was dislodged into the canal. (4) A ledge exists in the canal on which the point is catching. • In any case, the problem can be solved by one of two methods: 1. Selecting a new file of the same number and re-instrumenting the canal to full working length until the file is loose in the canal, or 2. Selecting a smaller size gutta-percha point. Trial and error will determine when the point is seated. • If a ledge has been developed in the canal wall, it must be removed. • After the initial point ( Master GP cone) has passed the trial point tests, it should be removed with cotton pliers that mark the soft point or cut with the scissors at the reference point. A, Removal of measured and tested initial gutta-percha point. Cotton pliers mark guttapercha at incisal edge. B, Standardized points are seated at the working length and trimmed at the occlusal reference point with scissors. The master points should reach to within 1.0 mm of the working length. 3. Drying the Canal • While preparations are being made to cement the filling point, an absorbent paper point should be placed in the canal to absorb moisture or blood that might accumulate. • Larger paper points are followed by smaller paper points until full length is achieved. • If there is blood on the tip of the paper point, check the working length. • Any bleeding should be stopped, the blood irrigated from the canal, and care taken to avoid penetrating beyond the apex with the final paper point as excess moisture or blood may affect the properties of the sealer. 4. Mixing and Placement of the Sealer  Mixing. • A sterile slab and spatula are used. • One or two drops of liquid are used and the cement is mixed according to the manufacturer’s directions. • The cement should be creamy in consistency but quite heavy. • Ideal consistency is achieved: 1. When the mixture can be held for 10 seconds on an inverted spatula without dropping off . 2. Will stretch between the slab and spatula 2 cm (one inch) before breaking. Root canal cement should be mixed to thick, creamy consistency, which may be strung off slab for 1 inch. • Ideal consistency permits: 1. Adequate clinical working time. 2. Minimal dimensional change. • Sealer should not be mixed too thin, but on the other hand, it must not be so viscous that it will not flow between the gutta-percha points or penetrate accessory and lateral canals or the dentin tubules. • Root canal cement/sealer may be placed in a number of ways: 1. Pumping the sealer into the canal with a gutta-percha point. 2. Carrying it in on a file or reamer, which is turned counterclockwise, pumped up and down, and wiped against all the walls. 3. Using rotary or spiral paste fillers (Lentulo Spirals) turned clockwise in one’s fingers or very slowly in a handpiece. 4. With an ultrasonic file (run without fluid coolant). A simple, effective method of sealer application. A hand file covered with sealer is inserted into the canal and spun counterclockwise to coat the canal walls. Rotary paste fillers made for contra-angle handpiece can also be rotated clockwise by finger action. Used for placing initial sealer with solid core root fillings or completely filling the canal with paste filling.  Placement of the Master Point.  The premeasured primary (or master, or initial) point is now coated with sealer and slowly moved to full working length.  The sealer acts as a lubricant. The entire surface of the cone entering the root canal is coated with a thin layer of sealer. Steps of Obturation with Lateral Compaction • Place the primary point ( master GP cone) with the sealer. • The premeasured spreader is then introduced into the canal alongside the primary point using a rotary vertical motion and moved apically to full penetration, marked on the shaft with a silicone stop. The spreader is introduced alongside the master cone to the proper apical depth. • It is the wedging force that occurs between the canal walls toward the gutta-percha that results in deformation and molding of the gutta-percha to the opposite canal walls. Longitudinal view of lateral condensation. A, With the master cone and sealer in the canal, the spreader is forced alongside the cone until it is within 1 to 2 mm. of the cone tip. B, Cone-tip is compressed toward the apical constriction to seal the foramen. C, If the spreader does not penetrate to near the tip of the gutta-percha, the cone will not be compressed into the apical portion of the preparation as the condensing force dissipates (arrows). • There is no need to apply a lateral force to the spreader. • The initial spreader may be left in place for one minute to allow the primary gutta-percha time to reconform to this pressure. • Along with the lateral force of spreading, a vertical force, although less, is also exerted. • If full penetration is still not achieved, a spreader that is a size smaller can be used, which will bind apically to the previous spreader. • Remember: adequate condensation does not occur unless the initial spreader reaches desired length ( 1-2 mm shorter than the working length). • Only light pressure (less than that used for amalgam condensation) is required during lateral compaction because the gutta-percha is not condensed (it is molded and deformed), and because as little as 1.5 kg of pressure is capable of fracturing a root . Vertical root fractures can occur with excessive compaction forces. A, Followup radiograph of a mandibular left first molar. A deep isolated periodontal probing defect was associated with the buccal aspect of the mesiobuccal root. B, Flap reflection revealed a vertical root fracture. Endodontically treated maxillary premolars serving as abutments. A. Typical periradicular radiolucencies around the two premolars. B. B. Six months after diagnosis of VRF. Separation of root segments can be seen in both teeth. • The spreader is then removed with the same reciprocating motion and is immediately followed by the first auxiliary point inserted to the full depth of the space left by the spreader . • Auxiliary cones that are the same size or smaller in diameter or taper than the spreader are used. After careful removal of the spreader, an accessory cone, lightly coated with sealer, is introduced to the apical depth created by the spreader. • This point is followed by more spreading and more points , more spreading and more points, until the entire root canal is filled. • To ensure a cohesive filling, additional sealer may be added with each point as a lubricant to facilitate full penetration. spreader is reinserted to make room for an additional accessory cone. • The accessory cone must be the last one to be placed in the canal rather than the spreader. A. The obturation process is continued until there is no more room for additional insertions of the spreader or further condensation of accessory cones (Facial view). At this point, the obturation is completed. B. Proximal view of the obturated canal. • Obturation is considered complete when the spreader can no longer penetrate the filling mass beyond the cervical line. • A radiograph is then taken (before searing) to check the previous steps and to correct any problems. • If obturation looks adequate (length, taper and density) , the protruding points are seared at the orifice of the canal with a hot instrument. • Vertical compaction with a large plugger to the softend GP will then ensure the best possible coronal seal. A, Excess gutta-percha is removed to the cervical line by inserting a hot instrument into the pulp chamber. B, Plugger is used to compress the remaining warm gutta-percha. C, Floor of the pulp chamber in posterior teeth is coated with sealer, and warm guttapercha is packed into the pulp chamber to seal any auxiliary canals that may be present. • All of the sealer and guttapercha should then be removed from the pulp chamber using a cotton pellet soaked in alcohol and a permanent or temporary filling should be placed. • A final radiograph is then taken with the restoration in place without the clamp. • Finally, obturation is evaluated on the basis of : 1. Length ( should be confined to the canal space and shorter than the radiographic apex by 1-2mm). 2. Taper (obturation should reflect proper taper of root canal preparation). 3. Density (obturation mass should have no voids and properly adapted to the canal walls). 4. Level of gutta-percha removal (1mm apical to the gingival margin in anterior teeth and 1mm apical to the canal orifice in posterior teeth) . 5. The coronal seal ( properly placed coronal restoration ). Maxillary right central incisor exhibits a lack of density and taper. Maxillary left central incisor has voids and unfilled canal space Examples of adequate obturation (reflects adequate shaping) 1. Length 2. Density 3. Taper. 4. Level of GP removal. 5. Coronal seal. Sealer puff Examples of adequate obturation (reflects adequate shaping) 1. Length (some sealer puff present above the right central). 2. Density 3. Taper. 4. Level of GP removal. 5. Coronal seal. Correcting obturation problems Advantages of making obturation verification radiograph: 1. Before the excess GP is seared off , the entire mass can usually be removed by grasping the cones with the fingers. • Fitting a new master cone & reobturation is then possible. 2. If the excess GP has been seared off, an overfill can sometimes be corrected before the sealer sets by removing all GP with files. • Note: Obturating materials extruded beyond the apex should not be treated surgically unless failure to heal is evident on recall examination. Advantages of lateral condensation 1. It is uncomplicated. 2. Requires a simple armamentarium. 3. Seals as well as any other technique in conventional situations. 4. The most important advantage above all techniques is length control. 5. Ease of retreatment. 6. Adaptation to canal walls. 7. Positive dimensional stability. 8. The ability to prepare post space. Disadvantages The only disadvantage is the difficulty in obturating teeth with An open apex Canals with internal resorption