preclinical manual
DESCRIPTION
Endo Preclinical manualTRANSCRIPT
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DEN6432 (SPRING 2013)
Basic Endodontic Therapy
U. Nair
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INTRODUCTION TO PRECLINICAL ENDODONTICS
The purpose of this preclinical course is to provide practical preclinical experience in performing nonsurgical root canal treatment on uncomplicated anterior, premolar, and molar teeth and prepare the dental student in the management of pulpal and periradicular disease through various forms of clinical simulation exercises. Additionally at the end of this course you will be exposed to some exercises using Case- Based Scenarios and Team-based learning. COURSE OBJECTIVES:
At the completion of this course the student should be able to:
4. Identify all the materials and supplies necessary for all the procedures involved in this course and understand their applications in the clinic.
5. Identify patent pulp chambers and canals by means of endodontic digital
radiographs; recognize canal systems with extreme curvatures, calcifications, and other complicating anatomical/pathological features.
6. Understand and apply the buccal object rule as it relates to endodontics.
7. Prepare ideal access openings on all teeth.
8. Establish appropriate working lengths, and properly clean and shape
canals of teeth in preparation for obturation using warm condensation technique.
9. Identify, prevent, and manage procedural errors that may occur during
endodontic treatment.
10. Understand and apply appropriate clinical regimens required for endodontic treatment including: proper local anesthesia, rubber dam isolation, radiographic interpretation, restoration placement, and record- keeping.
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EVALUATION AND ATTENDANCE POLICIES Didactic Component: Evaluation of this component consists of four announced written quizzes and two written exams (mid-term and final). The quizzes will be scheduled by the course consultant and will constitute 10% of the final course grade. Two written exams will be averaged and constitute 40% of the final course grade. A grade of C (72%) on the written exams is the minimal satisfactory performance. A student will be permitted only ONE retake on each of the written exams and no retakes will be offered on the quizzes. If a student fails any of the written exams, after successfully achieve the minimum passing score (retake exam), the original grade will be used in computing the final course grade. If a student is unsuccessful on the retake examination, an E grade will be recorded on the transcript. Automatically, the student will be re-enrolled when the course is next offered. Psychomotor Component: Two psychomotor exercises (averaged) represent 50% of this course’s grade. The student must demonstrate a thorough understanding of the principles involved and be able to perform the procedures with little or no help from the faculty to pass the psychomotor exercises. A grade of C (2.0 or 72%) must be achieved ultimately in the final evaluation for each of the steps of the psychomotor exercises. A grade of E (< 2.0) will make it necessary for the student to perform the procedure again. After successfully performing the prescribed exercise again (achieving a grade of 2.0 or above) the grade will be recorded as a 2.0, and this will be used in the final grade tabulations. If any step is not successfully completed, the student will be required to re-enroll in the course. Since these procedures are repetitions of previous, non-graded exercises, failure to achieve the minimum passing grade will affect the student’s overall evaluation. It is expected that there will be individual student differences in levels of accomplishment; therefore, a grading scale is employed. The final evaluation of the psychomotor exercises must average C (2.0) to constitute a passing performance. Four or more cumulative repetitions will warrant a final grade of E (< 2.0) and necessitate the student's retaking the entire course. A retaken written exam will count towards the cumulative repetitions. Psychomotor skills appropriately incorporate some opportunity for repetition of the procedures without penalty. The initial practical exercises in this course are non-graded experiences; but definitive verbal and written critiques will be an integral part of the process. Individualized exercise repetitions will be prescribed as needed. Assessment of psychomotor skills will be determined from student performances on the psychomotor graded exercises. IMPORTANT NOTE: Since there will be allowed retakes of the written exams and repetitions of the simulated exercises, this course does not offer remediation.
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Students who fail to achieve the minimum passing grade (2.0 or above) in the written exams or psychomotor exercises will receive a grade of E, will be required to re-enroll the course, and will be send to the SPEC. A detailed description will be provided in your preclinical manual. Access Openings - the incorrect access form (outline) and position, under- or overextensions, changes in treatment plan due to overextensions, failure to identify canals and/or unroof the pulp chamber (pulp horns), presence of gouges, achievement of straight line access, finishing errors (rough walls), and perforations. The point deductions associated with these errors depend on their severity. For instance, while a moderately overextended or underextended access opening may result in a deduction of 0.50 to 0.75 point in your grade, a grossly overextended or severely gouged access may require immediate remediation. Your instructor has been calibrated to grade you according the severity of the error. However, remediation will be immediately required if one or more of the following errors are observed: 1. Change in restorative treatment plan due to overextension or gouges 2. Failure to remove the pulp horn 3. Failure to completely unroof the pulp chamber 4. Failure to identify canal(s) 5. Perforate the tooth while performing access opening Cleaning and shaping – the adequacy of the preparation flare (taper), presence of an apical stop, size of the apical preparation (overprepared x underprepared canal), length of preparation (based on radiographic assessment), and cleaning and shaping procedure errors, such as: presence of blockages, canal transportation, ledges, and perforation will be taken into consideration. The deductions will vary according the error (s) severity. Remediation is required if one or more of the following errors are observed: 1. Failure to identify canal 2. MAF extends past the working length with light apical pressure 3. Severe over- or underinstrumentation 4. Loss of more than 2.0mm in root canal working length due to canal blockage or transportation 5. Perforation of the root surface
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Obturation – length of obturation (underfilled, flush, overfilled or overextended obturations), presence of sealer overextensions, radiographic density (presence of voids in the obturation mass), GP burn out, pulp chamber cleanliness after obturation, presence of temporary restoration (whenever required), final radiograph. As above, remediation is required if one or more of the following errors are observed:
1. The obturation is 2.0mm (or more) past (overfilled) the radiographic apex.
2. The obturation is 2.0mm (or more) short (underfilled) of the radiographic apex.
3. Presence of apical void or large voids throughout the obturation
4. Obturation is overextended (material goes beyond the apex and there is no apical seal)
5. Density is inadequate throughout the length of the obturation mass.
Final psychomotor grades
The grades for the SimLab exercises vary from 1 (one) to 4 (four). After the completion of the psychomotor exercises (Spring and Summer terms), your scores will be averaged and converted using the scale below to obtain the practical (psychomotor) grade, which combined represents 50% of your final grade.
The following grading scale will be used:
4 Excellent: Superior quality
3 Acceptable: Satisfactory quality
2 Substandard: Below acceptable quality, but is correctable to at least satisfactory standard. 1 Unacceptable: Inadequate quality, but is not correctable and may require change of treatment
Letter Grade 4 point Scale Percentage Scale A 3.50-4.00 95-100 A- 3.25-3.49 92-94 B+ 3.00-3.24 88-91 B 2.75-2.99 84-87 B- 2.50-2.74 80-83 C+ 2.25-2.49 76-79
C 2.00-2.24 72-75 E < 2.00 < 72
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Final Evaluation: The final evaluation will be based on the following:
• Written Quizzes 10% • 2 Written Exams (averaged) 40% • Psychomotor 1 & 2 (averaged) 50%
Student must have 72% or higher on each of the written and psychomotor assessments.
Laboratory Phase :
The purpose of this course is to prepare the student to understand and perform the technical and mechanical aspects of endodontic therapy. At the end of the course, the student should be comfortable and be minimally competent in performing nonsurgical root canal treatment on uncomplicated anterior, premolar, and molar teeth in a clinical situation. Each student will be evaluated on a weekly basis by an assigned instructor; evaluation will be based upon organization, knowledge, neatness, use of proper infection control procedures, quality of skills, project completion, and time management. Students are encouraged to obtain their weekly grades by the assigned faculty as well their feedback.
Attendance is required for all laboratory sessions. Excused absences must be obtained from the course director. Unexcused absences will result in a lab grade of zero and may result in an incomplete or course failure. Unless otherwise indicated, all laboratory projects must be completed during the scheduled laboratory sessions.
During all clinical simulations, the use of eye protection, masks, and gloves is mandatory. Failure to follow universal precautions will result in a deduction of points
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LABORATORIES I, II and III (1/08/2013, 1/15/2012, 1/29/2012)
INTRODUCTION TO INSTRUMENTS, ACCESS OPENINGS AND WORKING LENGTH DETERMINATION (#9, 24, 4, 20, 14, and 30)
(YOU HAVE 3 SESIONS PROVIDED FOR THIS PROJECT) Objective: The general objective of this laboratory session is to prepare the student to be able to perform access openings on teeth requiring endodontic treatment and to obtain an understanding of the root canal anatomy. Upon completion of this laboratory, the student should be able to prepare proper access openings on the following teeth: mandibular incisor, mandibular premolar, maxillary incisor, maxillary cuspid, and maxillary premolar. The student will also determine the working length for root canal therapy.
STUDENT supplies:
1. Endodontic Instrument Tray with the following instruments: a. Mirror b. #23/0 explorer/probe c. 31 L spoon excavator d. 2 pairs of cotton pliers e. DG 16 Endo explorer f. #1 Glick Plugger g. 5/7 and 9/11 Pluggers h. Cement Spatula i. Young’s frame j. FileMate, suction tips, irrigating syringe and rulers k. RD clamps l. Access bur kit ( # 2, #4, #6 round carbide burs, Endo Z bur) m. 2 file stands with hand files, rotary files and Gates Glidden drills n. Iris scissors and hemostats
2. Plastic storage box with your rotary motors and obturation equipment
(Motors will be collected in the box at the end of the course)
3. High speed and slow speed (friction and latch head) handpieces
During all endo lab sessions, it is required of you to establish a well organized work area and instrument set up. Your lab bench table should always be covered with whitepaper available in the lab.
These supplies will be used throughout the course
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The clinical mirror, the #23/0 explorer/probe, and the DG16 endodontic explorer instruments are very helpful when performing diagnosis and access openings. The curved end of the #23/0 explorer/probe is effective when inspecting for retentive areas, certifying the complete removal of the pulp chamber roof.
Aspiration tip for suction
The FileMate has pre-measured slots in which files are inserted to set them to the desirable length.
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Plastic Box: (one box signed out to 2 students) Contents: Cleaning and shaping equipments Endodontic Rotary Motor
Obturation equipments Buchanan Pluggers (size 1 and 2)
These pluggers are used to compact the gutta-percha.
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Downpack with System B
Pluggers for System B (.04, .06, .08, .10 and .12 Tapers)
Backfill with Calamus
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Assignment:
1. Read the appropriate chapter in the textbook, use the Preclinical manual as a Guide
2. Prepare access openings on the following teeth (in this prescribed order): Tooth #
9, 24, 4, 20,14 and 30
3. Each tooth must be evaluated by an instructor before proceeding to the next tooth.
ACCESS OPENING
The primary objective of an access opening is to provide a straight-line access to the root canal system so the canals can be properly instrumented and prepared prior to proper obturation. This step in endodontic therapy plays a significant role in the overall prognosis of the treatment. An access opening is much more than a hole into the roof of the pulp chamber. It is the pathway through which you will enter the pulp chamber. It is the pathway through which you will remove the pulp tissue irritants, and dentinal debris, shape the canals, and finally seal the root canal system. The access opening in anterior teeth is made on the lingual surface and in posterior teeth on the occlusal surface. The location and shape of the access opening is dictated by the morphology of the tooth and the root canal system. Therefore, the initial radiograph is an essential aid in visualizing the location and size of the pulp chamber and root canals.
There are three general principles to remember: 1. The pulp chamber and the canals are usually located in the center of the
crown and the roots.
2. The shape of the pulp chamber is very much the same as the external shape of the tooth surface on which the access opening is made.
3. A quality preoperative radiograph is essential.
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MAXILLARY INCISORS
Inspecting the lingual enamel surface, visualize the shape and location of the pulp chamber within the crown. It is in the middle of the crown and has the triangular shape of the crown. The student should begin the access opening using a high speed #2 round bur held perpendicular to the lingual enamel surface in the middle of crown (Fig 1)
Fig. 1
The student may pencil in the desired outline on the surface before penetrating with a bur. Outline the triangular shape of the opening, cutting through the enamel into the dentin.
Now switch to a standard round #2 or #4 round bur at slow speed. Place the bur in the center of the external outline form just created and penetrate through the dentin into the pulp chamber. In this step, the bur is not perpendicular to the enamel surface but parallel to the long axis of the tooth (See Fig 2).
Fig. 2
A common mistake in access openings for the anterior teeth is to continue drilling
through the dentin with the bur at a right angle to the lingual surface. This will result in perforation of the labial surface or a gouging of the labial wall of the pulp chamber. A meticulous examination of the preoperative radiograph is a MUST; it will be used as a
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guide to the depth of penetration of the bur into the pulp chamber. In some instants, the bur will not drop into the pulpal space due to a calcified chamber, making the procedure a little more difficult. When in the chamber, the opening in the roof may be enlarged by withdrawing the rotating bur (along the lingual wall) outward against the root. This will assist in the removal of the lingual triangle.
The lingual wall of the access preparation should now drop straight down into the canal so that the canal can be seen through the access opening.
The refinement of the access opening can be performed with an endo Z bur and it can be evaluated with the use of an endodontic explorer to be certain that the roof of the chamber has been completely removed.
Check for removal of pulp horns and lingual shoulder and achieve straight line access
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1. Maxillary Central
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2. Maxillary Lateral Incisor
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MANDIBULAR INCISORS The mandibular incisors have one of the highest failure rates in endodontic treatment. An inadequate access opening is probably responsible for many of the failures since approximately 40% of these teeth have two canals. When a second canal is present, it is usually lingual to the main canal. The normal radiographic view of the pulp chamber and canals represents the narrow mesiodistal diameter of the root canal. One must realize, however, that the labiolingual diameter of that same pulp is always larger, anywhere from 2 to 8 times the mesiodistal measurement. The access opening, therefore, must be designed to give straight-line access into this canal as well to allow for the identification of a possible lingual canal. The opening may be very narrow mesiodistally, but is larger in a labiolingual, or gingivoincisal direction.
The access opening in mandibular anterior teeth is triangular to ovoid. After initial penetration of the enamel with a small round high speed bur, the outline is prepared with the bur perpendicular to the enamel surface. Penetration through the dentin into the pulp chamber should be done at slow speed using a standard length latch type #2 round bur starting in the center of the lingual surface of the tooth. Since only a narrow mesiodistal access opening is necessary, the smaller round bur provides the necessary width without the possibility of gouging of the coronal portion at the cervical level of the tooth, possibly leading to perforation of the narrow neck at the cementoenamel junction. Penetration into the pulp chamber and final shaping of the entry should be done with the shank of the bur against the incisal edge of the tooth. Once penetration into the roof of the pulp chamber has been established with the small round bur, the tip of the bur is inserted into this opening and the shape is completed with this instrument. The bur is "lifted" labially and lingually to remove the remaining dentin comprising the roof of the pulp chamber. Students commonly error by unroofing only the labial portion of the pulp chamber. As stated previously, one must remember to look for a second canal usually towards the lingual. But remember no encroachment on cingulum or marginal ridges. Since the mandibular anterior teeth are usually retained in the mouth longer than the rest of the dentition and are smaller, they may have calcified chambers and canals which are difficult to locate. The student should check with an instructor if the chamber or canal cannot be located.
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Mandibular central and lateral incisor
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MAXILLARY AND MANDIBULAR CUSPIDS
The maxillary cuspid usually has one root and one canal and is the longest tooth
in the dental arch; the mandibular cuspid also has one root and one canal. The maxillary and mandibular cuspid teeth have similarities when making the access openings. These teeth present a narrow canal on a normal radiograph. This tooth is also very wide in a labiolingual direction.
The enamel is penetrated with a small round high speed bur perpendicular to the middle of the lingual aspect of the crown. This bur is then used to form the access outline which will not entirely mimic the external outline of the tooth. The outline form will be more of an ovoid preparation rather than a triangular one.
Entry is gained into the tooth using a carbide #2 or #4 round bur in the middle of the outline form just produced. The bur is directed in the long axis of the tooth as in the case of the other anterior teeth.
Canine
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1. Maxillary Canine
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2. Mandibular Canine
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Maxillary Premolars Maxillary first premolars are most commonly birooted (65%) with a buccal and a
palatal root; 85% of maxillary first premolars have two canals; 6% of maxillary first premolars may have three roots and three separate canals. Maxillary second premolars most often have one root and one canal (75%). The outline form for maxillary premolars is ovoid in a buccal-palatal dimension. The student should picture the outline of the pulp as if he or she could see it from the occlusal view. It is in the center of the tooth and is much broader buccolingually than it is mesiodistally. Begin with a high speed 1157 bur perpendicular to the occlusal surface and outline the roof of the pulp chamber, penetrating through the enamel into the dentin. For any access preparation, it is important to begin small and gradually enlarge it to the desired shape and form.
When the outline is completed, use a slow speed carbide #4 bur in the center of the occlusal outline to penetrate through the dentin into the pulp chamber. When you feel the bur drop into the pulpal space you are ready for the next step.
Using the slow speed #4 bur or a 1157 bur in a high-speed handpiece with water, place the tip of the bur through the hole in the roof of the pulp chamber and with the bur rotating, move the bur from buccal to lingual with outward strokes to completely unroof the chamber. The outward action of the bur completes the mesiodistal width without any further effort. Do not get into the habit of drilling into the chamber of posterior teeth as perforations of the furcation of the multirooted ones may occur; use of the endo-Z bur decreases the chances for gouging the floor and perforating. In addition, avoid using the surgical length burs in these multirooted teeth so that a furcation perforation is prevented.
There is a distinct danger of gouging the mesiodistal diameter of the chamber. This is a common error caused by pendulating the bur inside the pulp chamber. Remember that the walls must be perpendicular or slightly divergent to the occlusal surface, not undercut. Due to the concavity of the mesial surface of these teeth, gouging in a mesial direction can result in a proximal perforation. This perforation will severely weaken the coronal structure and can cause subsequent fracturing of the undermined crown. A mesial or distal cervical perforation is not easy to repair and may affect the prognosis of this tooth.
Once the access has been completed, the student should note that the canal orifices are located at the buccal and lingual extremities of the pulp chamber. Examine the pulp chamber floor to ascertain whether there are two canal orifices visible. The opening into the chamber should resemble the access opening, being longer buccolingually than mesiodistally. Probe with the endodontic explorer to see if you can identify two canals.
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3. Maxillary first premolar
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Maxillary second premolar
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MANDIBULAR PREMOLARS
Mandibular premolars most often have one root and one canal. Mandibular first premolars have a bifurcated canal system 25% of the time; the level of the bifurcation can be at the middle or apical third of the root, making this tooth very difficult to manage endodontically. The occlusal surface of these teeth is usually ovoid. This shape determines the shape of the pulp chamber and the access opening.
The pulp chamber is in the center of the crown. The most common error in making the access opening in mandibular premolars is the tendency to continue with the bur perpendicular to the occlusal surface, which may cause the bur to exit at the buccal cervical surface with a perforation of the tooth, or even worse, below the level of the alveolar bone.
The penetration of the enamel is accomplished with the a small round bur held perpendicular to the occlusal surface. Then the standard length #4 round bur is used in a slow speed handpiece to drop into the pulp chamber; the long axis of the bur is tipped overthe buccal cusp and this path of entry is used in unroofing the pulp chamber and in preparing the funnel shaped entrance to the chamber. The endo-Z bur may be used to unroof the chamber. Students commonly error by unroofing only the buccal portion of the pulpal chamber.
Mandibular Premolar
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Mandibular first premolar
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Mandibular second premolar
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MANDIBULAR MOLARS
Mandibular first molars usually have two roots, mesial and distal. The mesial root has two canals, mesiobuccal and mesiolingual. The distal root usually has one canal but can have two canals 30% of the time. Mandibular second molars are smaller coronally than first molars and normally have two roots and three canals like first molars. The distal root may contain more than one canal but it is less common than the mandibular first. C- shaped canal systems are sometimes seen in mandibular second molars. The access opening into mandibular molars, like all other access openings, is initially made with a 1157 high speed bur held perpendicular to the occlusal surface. The opening is started in the center of the tooth, and the final outline is somewhat trapezoidal in shape, with the base of the trapezoid on a line drawn from the tip of the mesiobuccal cusp to the tip of the mesiolingual cusp. This line is at least 3 mm from the mesial marginal ridge. Keep in mind that many mandibular molars have crowns that are tilted lingually, so that it is necessary to make the opening sufficiently toward the buccal to gain direct access into the mesiobuccal canal.
Mandibular molar (access outline)
A common error in mandibular molar access openings is to make the enamel outline too near the lingual surface with subsequent perforation of the lingual surface at the gingival level. Keep in mind that your objective is to completely remove the roof of the pulp chamber and to leave the floor of the chamber intact.
After the outline has been prepared through the enamel with the 1157 bur, a standard length #4 or #6 low speed round bur is used to penetrate into the roof of the chamber. At this time a #6 round bur is used in a pull stroke to completely unroof the chamber so that the canal orifices can be seen. Do not cut on the floor of the pulp chamber as you will destroy its natural anatomy. It is that anatomy that helps you locate the canal orifices. Burring on the pulp chamber floor often leads to a perforation in the furcation area which may not be successfully repaired. Once an opening through the roof has been made with the round bur, a endo-Z bur in a high-speed handpiece with water can also be used to unroof the chamber. It is moved laterally to unroof the chamber Use of this bur reduces gouging and the risk of perforation of the floor of the pulp chamber.
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The surgical length burs are never used during access preparation of maxillary or mandibular molars; due to their length, use of these burs may increase the chance of gouging and perforation through the floor of the chamber. Once the roof has been removed, identify all canal orifices with an endodontic explorer.
MAXILLARY MOLARS
The maxillary first molar is the largest tooth in volume with a complex root canal system. Maxillary first molars most often have three roots: mesiobuccal, distobuccal, and palatal. The mesiobuccal root curves to the distal and is thin mesiodistally and broad buccopalatally. The mesiobuccal root has a high incidence of second canals located between the mesiobuccal orifice and the palatal orifice (reports range from 60% to 75%); it is often referred to as the mesiolingual canal. The distobuccal root has one canal and most often curves to the mesial. The palatal root has one canal and it is the longest; the apical third often curves to the buccal. The maxillary second molar most often has three roots and three canals. The three roots are grouped closer together with the orifices of the canals often closer than in the first molar. The maxillary molar is the outstanding exception to the dictum that the pulp chamber is located in the middle of the crown. The guide for the location and shape of the pulp chamber, and therefore the access opening, is determined by the triangular shape of that portion of the crown outlined by the mesiobucal, distobuccal and mesiolingual cusps. The distal border of this triangle is represented by the disto-oblique ridge, completely omitting the distolingual cusp. The access opening should not cross the oblique ridge. The access opening in the maxillary molar is intiated in the central fossa and is triangular in shape. The base of the triangle is towards the buccal and the apex towards the palatal.
Visualize the roof and the pulp chamber within this triangle. With a high speed 1157 bur, start in the central fossa and outline the access opening into the dentin with the bur held perpendicular to the occlusal surface.
Maxillary molar ( access outline) When the outline is completed, use a low speed #4 or #6 round bur to penetrate through the dentin into the pulp chamber. When you feel the bur drop in the pulpal space, do not continue any further. The next objective is the complete unroofing of the chamber and any change or alteration of the floor of the chamber must be avoided, both for fear of
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perforation of the floor, and to be able to use the sloping floor to guide your instruments readily into each of the canals. Using a withdrawal stroke, completely unroof the chamber. Use a #4 or #6 standard length round bur for this purpose. A safe-ended diamond can also be used for unroofing the chamber. The floor of the pulp chamber will appear a darker shade than the dentinal roof and the floor will taper into the orifice of each canal. If visual inspection appears to show a flat white floor with 3 holes in it, you probably have only exposed the pulpal horns of the chamber and have not unroofed the chamber. If you are in doubt, check with an instructor at this point. A perforation of the floor most likely will necessitate the removal of the tooth.
Never use a surgical length bur in preparing the access opening for any molar. In most cases the orifices are sufficiently tapered for subsequent procedures and good access is provided merely by the complete unroofing of the pulp chamber. It is important not to encroach on the anatomy of the floor or walls of the chamber. Once the access is complete, identify all of the canal orifices with an endodontic explorer. With the high incidence of four canals in maxillary molars, it is better to assume that there are four canals until proven otherwise. Critique the access opening prior to the instructor evaluation.
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Maxillary first molar
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Mandibular First molar
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OUTLINE OF ACCESS OPENINGS
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CHAPTER II
WORKING LENGTH DETERMINATION CLEANING AND SHAPING
(BIOMECHANICAL PREPARATION)
The ultimate success of endodontic treatment is primarily dependent upon the proper cleaning, shaping, and filling of the root canal system. More specifically, the objectives of endodontic treatment include the complete removal of pulp tissue, irritants, and organic debris from the pulp chamber and radicular canals as well as the enlargement and subsequent filling or obturation of those canals. The cleaning and proper shaping of the canals, also known as biomechanical or chemomechanical preparation, requires the use of specially designed hand and rotary instruments known as endodontic files as well as irrigating solutions to dissolve necrotic pulp tissue, chemically desinfect the intricate canal ramifications, as well as enlarge the root canal space.
Objectives: Upon completion of this exercise, the student should:
1. Understand the various types of endodontic instruments available as well as the design, use, and resultant shape created by the use of each instrument.
2. Understand overall objectives of cleaning and shaping and be able
to properly prepare the canal to receive a gutta-percha filling.
3. Understand the concept of the flare and crown-down canal preparation.
4. Describe the method of “working length“ determination.
5. Understand the concepts of circumferential filing, anti-curvature
filing, and recapitulation. 7. Understand the use of rotary instruments (Gates-Glidden drills) for
preparing or flaring the coronal one-third of canals. 8. Understand the use of the Profile® rotary file series for
preparing the canal
Biological And Mechanical Objectives of Cleaning and Shaping
Removal of the pulp tissue, canal contents, and adjacent dentinal areas and the preparation of the apical area and canal walls to receive a final filling material constitutes the most important phase of endodontic treatment. Biologically, it is essential that all cleaning and shaping (i.e. biomechanical instrumentation or preparation) be confined to the root canal space. Thus, an accurate determination of the working length is necessary in order to avoid under-instrumentation or over-instrumentation. Working length is defined as the distance from a reference point on a tooth (such as incisal edge or cusp tip) to the point where the root canal filling should terminate. This statement provides the parameters necessary to measure, prepare, and fill the entire length of the root canal
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space. The working length terminates at the apical constriction, which is usually, but NOT ALWAYS 1 mm short of the radiographic apex. Canal preparation at the exact radiographic apex would destroy the natural constriction at the cemento-dentinal junction as this constriction helps to provide the necessary matrix to resist overfilling beyond the apical foramen.
Once the working length has been determined, the clinician must develop a cavity preparation within each canal that is conceptually a continuously tapering funnel preparation in three dimensions. The narrowest part of the canal is located at the cemento-dentinal junction where an apical seat or stop is prepared to confine the filling material within the canal. This is primarily accomplished through the use of endodontic hand instruments.
WORKING LENGTH DETERMINATION 1. The entire length of the tooth is measured from the diagnostic radiograph using a reproducible reference point. Reference points are concise landmarks which are selected as a visual aid. As stated before, these usually are incisal edges or cusp tips. The selection of a reference point should also be tailored to the clinical situation at hand. This requires the selection of a reference point that can make positive reproducible contact with the stop and with only a minimal deflection of the instrument. Depth of instrument penetration can be visually controlled by noting when the silicone rubber stop* on an endodontic instrument reaches the reference point or landmark during canal preparation. This landmark must be recorded, must be stable, and must be reproducible between appointments.
*Silicone rubber stops are used to help maintain the proper working length between successive files and to regulate the depth of instrument penetration. Correct stop placement aids in determining and maintaining length. Always place the stop at right angles to the file shaft. Since positional instability is a major disadvantage in using the movable rubber stops, it is essential to develop the habit of remeasuring before re- entering the root canal. 2. One millimeter is subtracted from this measurement; this is the trial length measurement and must be recorded in the record. This length is essentially an "estimated
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working length" measurement since it represents the distance from an external reference point to the apical constriction (i.e. the termination of the root canal system). 3. This measurement is now transferred to a hand File (NOT smaller than a size 15 in order to be radiographically visible). The distance on the file is determined by the placement of the rubber stopper at 90° to the long axis of the file. Any deviation from 90° can result in an error in measurement of up to 1.0 mm. The use of the endodontic finger ruler facilitates proper measurement. 4. The canal must be first lubricated with an irrigant prior to any file insertion. The file is carefully inserted in the canal until the rubber stop contacts the predetermined reference point. A radiograph of the tooth with the file in position is then taken. This radiograph is called trial length radiograph. 5. If the file is one millimeter short of the radiographic apex, the trial length becomes the working length and no other changes are made to it. The trial length is recorded as the working length. If the trial file length is no more than 1.5 mm short of or longer than the desired working length, the appropriate length adjustments are made and subsequently recorded. If the file length is beyond the 1.5 mm limit (long or short) from the ideal working length, another radiograph must be taken. Once the working lengths have been established and recorded for all canals along with their respective reference points, cleaning and shaping of the canal system can begin. 6. The same procedure is followed irrespective of the number of canals in a tooth. In a multi-rooted or multi-canaled tooth, the trial length files are inserted into all of the canals at the same time and only one radiograph is taken. One does not determine the working length of a tooth with multiple canals by radiographing each canal individually.
Endodontic Instruments
In the preparation of a root canal, the student must have a working knowledge of the action of each instrument used if it is to be used effectively and efficiently. Thus, one must thoroughly understand the differences which exist between the various endodontic instruments available before one can begin to objectively use them.
Endodontic files are intracanal instruments used to clean and shape the root canal space. All of these instruments are manufactured according to ISO standards. The dimensions of the instruments are designated according to diameters of the instruments at specified positions along the length of the instrument. The diameter at the tip is known as D0 and the diameter at the last flute is D16. The cutting spiral edge of the instrument is 16 mm in length. The diameter of the file increases at the rate of 0.02 mm per millimeter of the file length. This means, for example, that a size 15 file has a 0.15 mm diameter at its tip and a 0.47 mm diameter 16 mm from the tip of the instrument. The color coding for the handles of the files is developed for easy selection. Five colors are used beginning with white for size 15, yellow (20), red (25), blue (30), green (35), black (40), and then repeating with white for size 45 and so on. The size 8 file and size 10 file have a gray
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handle and a purple handle respectively but these colors are not repeated for any other size instrument. The instruments, due to the variation in tooth length, are available in 3 different lengths: 21 mm, 25 mm, and 31mm. However, the length between D0 and D16 is always the same; what varies is the distance between D16 and the handle. During this course and in the clinic, the student will be using 25 mm length files, each with a rubber stop.
BARBED BROACH ( Not frequently used anymore) A barbed broach is an instrument which has pointed triangular barbs deflecting outward from the main shaft of the instrument. These points are sharp and will pierce tissue. This instrument is designed for removing pulp tissue and is not used for any aspects of canal shaping. In addition, the projecting barbs of the instrument limit its use to wide canals.
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Upon insertion into the canal, the barbs "hug" the shaft of the instrument. Upon its removal, the barbs engage pulpal tissue and allow its removal.
Barbed Broach
K FILES These files are made from wire which is typically square in cross section. After twisting the blank wire counterclockwise to produce an inclined plane with a subsequent cutting edge, flutes are created which increase in diameter toward the handle of the instrument. It is the outer edge of each flute which is sharp and is the working cutting edge of the instrument. It should be used in a push/pull motion and is more tightly-twisted than a corresponding sized reamer.
K-FLEX FILES
These files are made from wire which is rhomboidal in cross section. After the twisting of this wire, flutes are created as in the case of the K - type file. The difference in this instrument is that only alternate flutes engage the canal wall allowing additional debris to be carried along the instrument due to the smaller alternate flutes. This instrument is also sharper since the flutes will engage the canal wall at a more perpendicular angle. The rhomboidal design also creates a more flexible instrument. These files should be used in a push/pull motion.
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FLEX-O-FILES These files are K-type files that are triangular in cross-section, thus improving flexibility as well as cutting efficiency. These instruments have a safe-ended tip with a smaller tip angle in an attempt to reduce ledging and canal transportation. The primary difference between this instrument and a standard K-type file is that the cross-section is smaller and the angle of the blades created are more perpendicular. Thus, this instrument is sharper since the flutes will engage the canal wall at a more perpendicular angle. The triangular design creates a flexible instrument but also one that may break more easily if not used properly. These files are in the preclinical and clinical file boxes.
Flex-O File
Summary: K-type, D-type (rhomboid), and triangular files are all instruments used in the cleaning and shaping of the root canal. Their most efficient cutting action is achieved mainly on the withdrawal or "pull stroke" of the file against the canal wall. The file is also capable of cutting in both directions and may be used in a rasping motion. The latter technique may force debris apically if one is not careful.
REAMERS These instruments are made from wire which is triangular in cross section like the triangular files. However, twisting this wire configuration fewer times than a file results in fewer flutes than a K-type file. In addition, the flutes are farther apart which allows for greater collection of debris. The active cutting edge of this instrument is located at the extreme edge of each flute. This instrument is used to enlarge a root canal. This can be accomplished by turning the reamer so that the blade will shave or plane the dentin wall. Care must be taken in the use of a reamer, since this turning action, if met by significant resistance, may cause instrument breakage. Reamers are more flexible and more fragile than K-type files due to their cross sectional shape. Reamers can be used quite effectively to prepare and clean larger canals, can be useful in the removal of gutta percha, and are helpful in creating post space. The fine reamers needed for small canals will tend to untwist when met with the resistance of the canal wall and thus will not be effective. The acceptable action of the reamer is a clockwise turning to engage and shave the dentin wall while resisting the tendency to move apically as would a screw.
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HEDSTROM FILES These files are made from a round wire blank on which a rotating cutter has been used to produce triangular segments. The result is a cutting surface consisting of a series of "cones" which increase in diameter towards the handle of the instrument. The design creates a very sharp edge and dictates that the instrument be used only on a withdrawal from the canal. Any rotation should be avoided since this will cause the file to bind in the canal wall predisposing these files to fracture. They should be used in outward motion only. Frequently used for gutta-percha removal during retreatment.
Hedstrom File
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ROTARY INSTRUMENTATION Introduction:
Over the last few years, significant changes have been made regarding instrumentation techniques in endodontics. However, the goal still remains the same: “a root canal system cleansed of its organic remnants and shaped in a continuously tapering funnel to receive a three dimensional filling of the entire root canal space.”
The proper access preparation is the most critical step prior to the cleaning and shaping of root canal systems. The goal of this phase of treatment should be to gain straight line access to the apical foramen or in the case of curved canals, to the point of maximum canal curvature. The coronal cervical bulge should always be removed when accessing a molar tooth. Restorations that may interfere with the ability of a file to negotiate and explore the apical portion of the canal should also be removed. Material:
Nickel titanium has several characteristics which differentiate it from other metals
such as stainless steel. The superelasticity allows them to return to their original shape upon unloading after significant deformation making these nickel titanium endodontic files more flexible, better able to conform to canal curvature than stainless steel files. However, these files are still subject to fracture when not proper used.
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ProFile® Vortex™ ® instruments feature:
ProFile® Vortex™ instruments feature: • 11mm handle • Safe ended tip • Active blade • Patented variable helical angle • .04 and .06 tapers • ISO sizes 15 through 50
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Table 1: ISO Standard 0.02 Tapered Hand Files Files # Color
Code
Diameter at
Do in mm
Diameter at
D16 in mm
10 Purple 0.10 0.42
15 White 0.15 0.47
20 Yellow 0.20 0.52
25 Red 0.25 0.57
30 Blue 0.30 0.62
35 Green 0.35 0.67
40 Black 0.40 0.72
45 White 0.45 0.77
50 Yellow 0.50 0.82
55 Red 0.55 0.87
60 Blue 0.60 0.92
70 Green 0.70 0.97
80 Black 0.80 1.02
Table 2 : Vortex Blue 0.04 Tapered Rotary Files
Files # Color
Stripe
Code
Diameter
at Do in
mm
Diameter at
D16 in mm
20 Yellow 0.20 0.84
25 Red 0.25 0.89
30 Blue 0.30 0.94
35 Green 0.35 0.99
40 Black 0.40 1.04
45 White 0.45 1.09
50 Yellow 0.50 1.14
55 Red 0.55 1.19
FILE LENGTH: The 0.04 and 0.06 taper series instruments can be purchased in different lengths. The most common and the one that will be used in the laboratory is 25 mm.
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Notice that length of cutting surface is 16mm. This is from D0 to D16.
Cleaning and shaping
Mechanical cleaning and shaping of root canals has been attempted in the past with a variety of instrumentation technique and instruments. A recent development in file design has produced tapered files made of nickel titanium which the manufacturer claims will increase efficiency, will decrease file breakage and canal transportation if used properly.
These files have various characteristics that contribute to less transportation and breakage. Non cutting tips also allows the tip to act as a guide, with most of the cutting occurring above the file tip.
These files require controlled high torque; therefore, regular slow speed handpieces must not be used. The ideal RPM suggested by the manufactures is 500 RPM used with these files. Always maintain the same RPM; DO NOT MOVE YOUR FOOT UP AND DOWN WHEN USING ROTARY FILES, as this will cause sudden stress on the file resulting in damage to the instrument.
Hand files are used as an important part of the procedure. Flex-O-Files hand files (.02 taper) are used in sizes 8, 10 and occasionally 15 to check canal patency. Larger sizes will still be utilized for the preparation of the apical third of the canal in case the canal has a severe dilaceration , and also to verify a proper apical stop.
The student should remember, as previously mentioned that every canal is curved and every canal is unique. You must consider the cleaning and shaping of root canal system as the artful phase of Endodontics.
CLEANING AND SHAPING USING ! THE CROWN DOWN TECHNIQUE Once the working length has been established, the next step is the pre-flare of the middle and coronal aspect of the canal system. Copious and frequent irrigation with sodium hypochlorite (in this case water) is necessary to keep loosened debris in solution for easy removal, to help dissolve pulp tissue, and to facilitate instrument lubrication.
1. Following access, establish trial length, and passively shape the canal with a #15 , #20, hand File. Remember that you have not reached working length.
2. Irrigate canal and passively use the #2 Gates-Glidden drill (equivalent to #70 file) in the coronal 1/3. Make sure the drill is rotating prior to placing into the orifice. The drill must not bind and no pressure should be placed on it apically. Use it very carefully in an up and down motion, making sure there is more pressure away from curve as it is withdrawn or moved up the canal.
3. Re-irrigate canal and follow with a #3 Gates-Glidden drill (equivalent to #90 file). Reirrigate and recapitulate with a #10 Flex-O-File to the trial length.
4. Place a #15 file to the trial length. Confirm WL as described above 5. Proceed with the normal cleaning and shaping sequence up to the file that might
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feel some resistance (#20-30) with larger maxillary incisors. 6. The guideline for the termination of the apical preparation is dependent on the
original size, shape, and degree of curvature of the canal and root. The minimum size must always be size 30.
7. The last ROTARY file used to working length after proper canal cleaning is referred to as the Master Apical File (MAF). This is the largest file used to create the apical seat or stop.
These are the recommended MAF sizes for each tooth or canal:
Maxillary centrals #35-50 (.04 or .06 taper) Maxillary laterals #35-50 (.04 or .06 taper) Maxillary canine #35-50 (.04 or .06 taper) Maxillary premolars #30-40 (.04 or .06 taper) Maxillary molars mb/db: #30-‐35 (0.04 or 0.06 taper)
Palatal: #35-‐50 (.04 or .06 taper)
Mandibular incisor #25-‐50 (.04 or .06 taper)
Mandibular canines #30-‐50 (.04 or .06 taper)
Mandibular premolars #30-‐40 (.04 or .06 taper)
Mandibular molars mb/ml: #25-‐30 (0.04 or 0.06 taper) Distal: #30-‐40 (.04 or .06 taper)
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Vortex Blue Technique 1. Access tooth and locate all canals. Identify canals with a DG16.
Place # 8, #10 or #15 Flex-O-File hand instruments to determine canal patency. Use Gates Glidden to remove the lingual pulpal horn or cervical bulge.
2. Establish WL 3. After negotiating the canal with a 0.02-tapered hand instrument
(Flex-O-File), start with the Gates Glidden bur #3, followed by the #2 and # 1Work up to size 20 hand file.
4. Set motor at 500 RPM and torque level of 2 or 3. 5. Use Vortex Blue orifice openers to enlarge the coronal third of the
canal. Use 30/.12 taper for larger canals and 25/.08 taper for smaller canals.
6. For bigger canals: Maxillary centrals, laterals, maxillary and mandibular canines, single canal premolars, palatal root of maxillary molars and single canal distal root of mandibular molars: Use 0.06 taper Vortex Blue files
7. All other canals use 0.04 taper Vortex Blue files 8. Start with size 50 Vortex Blue and work crown down till WL is
reached. a. The aim of this step is not to reach the working length. Each file
will be moving more apically. Remember that : “ YOU WILL NOT REACH WL WITH THE ROTARY FILE RIGHT-WAY, NEVER FORCE A FILE, LET THE CANAL ANATOMY DICTATE HOW FAR YOU CAN GO”
b. Do not force the files; when you feel resistance pull back. Ideally the tip should only act as a guide, with cutting occurring coronal to the tip. SHOULD NOT USE THE FILE MORE THAN 3 TIMES. Return to the hand file #10 or #15 to ensure patency. Never use any rotary instrument in a canal that has not been negotiated by a hand-file instrument to a minimum size 15 (Flex-O-File).
c. When cleaning small to medium size canals, enlarging the coronal third of the canal is often necessary to allow the rotary instrument in the canal (not more than half of the working length of the canal).
9. Now work Vortex Blue to WL to the size indicated in the table above 10. Hand files 0.02 (Flex-O-Files) to verify your apical stop and establish
your MAF radiograph.
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LABORATORY SESSION IV. Vand VI 2/5/13, 2/12/13, and 2/19/13 You have 3 lab sessions and 1 make up session to complete this
CLEANING AND SHAPING OBJECTIVE:
Upon completion of the technical aspects of this exercise, the student should be able to:
Biomechanically prepare the accessed teeth.
PROCEDURE:
1. Review the chapter on trial file length and working length determination and cleaning and shaping.
2. Biomechanically prepare the canal at the established working length.
CLEANING AND SHAPING
1. Files should be set to the established working length 2. A small amount of irrigant (use water for this exercise) should be placed in the
chamber of the tooth during biomechanical preparation. 3. Once the file is at working length, it is withdrawn with pressure exerted on the
wall of the canal. Remember, all the work done with a file occurs on the withdrawal stroke. This procedure is repeated with short withdrawal strokes (2-3 mm) around the entire circumference of the canal (circumferential filing). After many of these strokes, the file will feel quite loose in the canal when seated to working length. It is at this time that the next larger size file is introduced. Always use the files in sequence and always irrigate between files. If the next file will not go to working length, it should not be forced; return to the previously used size. Remember to recapitulate.
4. After you had obtained a minimal size file (#15) to WL, use your hand file passively, work with the GGlidden and then your Profile rotary files as previously described.
5. The entire canal is prepared with the repeated use of irrigant (water in the lab) at least after the use of each file. If the student does not use copious irrigation as indicated, these filings will end up at the "apex" of the canal. This "dentinal debris" can be seen at the base of the canal. In an actual tooth, a similar collection of dentin filings (dentin mud) may prevent the operator from reaching working length or may result in debris pushed into the periapical tissues.
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6. Once the cleaning and shaping is completed, study the shape of the canal for evidence of an adequately tapered preparation. Test the degree of taper by inserting a Hand file (MAF) with a rubber stop positioned to the working length. The characteristics of the completed preparation should be:
a. a smooth continually tapering funnel from the orifice to the apical constriction.
b. all irregularities removed from the canal wall. c. entire preparation in sound dentin terminating just short of the cemento-
dentinal junction. d. an apical stop formed by continual integrity of the apical constricture in
order to create an apical wall against which the gutta percha can be condensed.
7. There are several factors that should be considered in determining the size to which a canal should be filed or prepared to. There are two frequently mentioned rules of thumb:
a. file two sizes beyond the first file which binds.
b. file until clean white dentinal shavings are produced
Neither rule is adequate. There are other factors which are important in this determination:
a. the original size of the canal - a calcified canal may cause a #15 file to bind. In the palatal canal of a maxillary molar, two sizes beyond this is a #25 file which is inadequate for debridement and proper obturation of a canal of this size. Some idea of canal size can be determined from the original x-ray by "eye-balling" the width of the projected final file size against the width of the canal as seen in the radiograph.
b. the shape or curve of the canal - the presence of a curve in the canal limits the
size to which a canal can be prepared without risking the removal of excess tooth tissue or creating ledges, perforations, or zips.
c. the diameter of the root - many roots appear large in the middle and
occlusal one-third. Often, however, there is considerable narrowing in the apical one-third which is frequently associated with a curvature of the canal. This morphology is common in maxillary lateral incisors, for example.
d. knowledge of canal morphology - nothing can substitute for a thorough
understanding of root canal morphology. One must be aware of the size, shape, curvature, cross-sectional view of the tooth in question, etc. to intelligently determine the proper size to which a canal is prepared.
e. experience- past experiences with similar teeth offer significant
information upon which to refer in the treatment of future cases. Every tooth
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treated provides its own valuable lesson. When all else fails, rely on the experience of your instructors to aid you in determining to what size a canal should be filed.
Have your instructor evaluate your biomechanical preparation and assist with the size of your MAF.
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LABORATORY SESSION VII, VIII and IX OBTURATION
3/12/13, 3/19/13 and 3/26/13 (You have 3 lab sessions and 1 make up session to complete this step)
OBJECTIVES:
Upon completion of this exercise, the student should be able to:
1. Fit a master gutta percha cone into the prepared canal 1. Obturate the root canal system with gutta-percha and sealer using warm
condensation. 2. Take a final radiograph
After the master cone has been properly fitted, the objective is to seal off the root
canal system from the supporting tissues and from the oral environment. Certain criteria must be achieved before the root canal system is ready to be obturated clinically:
1. The canals must be dry.
2. The tooth should be asymptomatic Follow the step-by-step protocol for obturating,
Take a digital radiograph of the completed obturation and critique the obturation. The radiograph should indicate a well-condensed, homogeneous filling, throughout the entire length of the prepared canal space; there should be no voids.. The obturation should reflect a continuously tapering funnel preparation.
The gutta percha core filling is intended to fill as much of the prepared canal as is possible. The more completely the canal is occupied with solid core material (gutta- percha), the better the seal. STEP BY STEP TECHNIQUE OF FITTING THE MASTER GUTTA-PERCHA CONE AND WARM CONDENSATION The purpose of obturation is to develop a 3-dimensional, ideal seal throughout the entirety of the root canal system. In order to achieve this, a core filling material known as gutta-percha, in conjunction with a root canal cement or sealer, is compacted inside the root canal. The method of condensation used is known as warm condensation. Gutta-percha Gutta-percha, a trans-polyisoprene isomer of rubber, is the recommended material that is used to fill a root canal. It is supplied as cones containing approximately 2 0 % gutta percha, 60-65% zinc oxide and 15-20% waxes, opacifiers, and coloring agents.
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Endodontic sealer cement The sealing of the root canal is impossible to achieve by condensing gutta-percha alone. Similarly, sealing the canal and apical foramen with root canal sealer cement alone will result in dissolution and absorption of the sealer by periradicular tissue fluids. The best fluid-tight seal is obtained by condensing gutta-percha in combination with a root canal sealer cement. The sealer cement acts as a binder and a filler between the walls of the root canal and the additional auxiliary gutta-percha cones. Most endodontic sealers contain zinc oxide and eugenol, although there are calcium hydroxide-based sealers as well as resin types. The root canal sealer that will be used in the preclinic and clinic will be a zinc oxide eugenol sealer. PRIOR TO OBTURATION
1. Irrigate and thoroughly dry canal with absorbent paper points. The next step is to make sure that the master apical file will seat to the working length and that it cannot be pushed further apically. If this happens, it means that there is no apical retention form or stop and that the gutta-percha will most likely be extruded beyond the apex during the condensation. In this situation, the resistance form must be re-prepared to provide an apical stop before the fitting of the master cone.
Cone Selection
Endodontic Team care AAE,Dentsply 1. A master gutta-percha cone is chosen that approximates the length, shape and size of the prepared canal. The cone is fit snugly to your WL. Then, a radiographic image is
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obtained to verify the length. 2. Following the gutta-percha cone selection, the sealer is placed into the canal with the MAF and the master cone is lightly coated on its apical half and placed in the canal.
Endodontic Team care AAE,Dentsply
3. The System B is used with the proper tip, usually 0.06 taper to properly sear off and remove coronal segments of gutta-percha and to transfer heat to the remaining portion of the master cone. A cold compactor is used to compact the softened portion of the cone apically and laterally.
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4. The Calamus is used now to back fill the canal with remaining warm gutta-percha. With the needle in its proper position in the canal, the gutta-percha is passively injected into the root canal system, avoiding apical pressure on the needle. In 2 to 5 seconds the softened material fills the apical segment and begins to lift the needle out of the tooth . During this lifting by the softened, flowing mass the middle and coronal portions of the canal are continuously filled until the needle reaches the canal orifice. If necessary, additional amounts of gutta-percha can be easily injected to achieve complete obturation. Do not use excessive compaction pressures but fold the material in on itself as previously described for vertical compaction.
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At this point a radiograph is obtained to check the quality of fill. Check obturation on radiograph for length control and density.
Once the obturation is verified, burn out to the orifice using the System B tip.
Place cotton pellet in the chamber and seal access cavity with temporary filling material (Cavit). Smooth the filling material with a wet cotton pellet.