Working length determination and apex locator.ppt

Working length determination and apex locator.ppt

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  CONTENTS Introduction Anatomical considerations ofroot apex Importance of accurate working length determination Reference points Various methods of determining working length a) Non-radiographic methods  Periodontal sensitivity  Paper point measurement  Digital tactile sense 2
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  b) Radiographic methods Grossman,s method  Ingle’s method  Wein’s modification  Kuttlers method  X-ray grid system Advances in radiographic methods  Xeroradigraphy  Radiovisiography c) Electronic methods  Electronic apex locators d) Working length determination in primary teeth e) conclusion 3
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  INTRODUCTION  The removalof all pulp tissue, necrotic material and micro-organisms from the root canal is essential for endodontic success.  This can only be achieved if the length of the tooth and the root canal is determined with accuracy.(Gordon MPJ, Chandler NP. ) Int Endod J, 37, 425–437, 2004.  Therefore, determination of an accurate working length is one of the most critical steps in endodontic therapy. 4
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   Working lengthis defined as “The distance from a coronal reference point to the point at which canal preparation and obturation should terminate.” 5
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  Anatomical considerations ofroot apex  Anatomic apex: The tip or the end of the root determined morphologically.  Radiographic apex: The tip or the end of the root determined radiographically. 6
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   Apical foramen(major diameter): It is the main apical opening of the root canal. It is frequently eccentrically located away from the anatomic or radiographic apex.  Apical Constriction (Minor Apical Diameter): The apical portion of the root canal having the narrowest diameter. 7
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  9  The foramenof the main root canal may be located to one side of the anatomical apex, sometimes at distances of up to 3 mm in 50–98% of roots (Kuttler 1955, Green 1956, Pineda & Kuttler 1972).  The foramen to apical constriction is approximately 0.5 mm in the younger group and 0.8 mm in the older group for all tooth types . (Kuttler 1955, Dummer et al. 1984, Stein & Corcoran 1990).
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  Cemento-dentinal-junction :  Itis the anatomical and histological landmark where the periodontal ligament begins and the pulp ends. • The location of the CDJ ranges from 0.5 to 3.0 mm short of the anatomic apex.(Gordon MPJ, Chandler NP) Int Endod J, 37, 425–437, 2004 10
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  Importance of accurateworking length determination  Confine the instrumentation to the canal system (within dentin).  Create and maintain an apical stop or seat at the minor constriction. Optimum length has been established at 0.5-1mm short of apex.  Prevent under- instrumentation that could leave tissue and debris in the apical segment.  Prevent over- instrumentation which could cause patient discomfort, apical perforation, overfilling and pain due to damage periapical tissue, or potentially cause an infection or cyst development from the placement of irritating materials beyond the apex. Ricucci D, Int Endod J 1998;31:384-93. 11
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  -Failure to determinecorrect working length leads to, a) Incomplete instrumentation. b)Ledge formation. c)Underfilling with apical perforation. d)Persistant pain and discomfort from retained pulp tissue. 12
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  REFERENCE POINTS Coronal referencepoint  Point from which canal length is measured  Should not be diagonal lines of fracture or weakened cusps  Reproducible 14
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  Coronal reference point For Anterior- incisal edge  For Posteriors- cusp tips  If no particular reference point ---ledge can be made 15
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  STOP ATTACHMENTS(GROSSMAN)  Stopscan be made by inserting an instrument blade through a small piece of rubber dam or rubber band.  Commercial stops made of metal, silicone rubber and plastic are also available.  Tear drop silicone –rubber stops have an added advantage because they do not have to be removed from the instrument during sterilization at 450⁰F.  It can be positioned to indicate instrument curvature, a prepared gentle curvature made on the instrument blade, that facilitates insertion of the instrument into a canal orifice and penetration to the root apex in fine, tortuous canals.
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   Special tearshaped or marked rubber stops can be positioned to align with the direction of the curve placed in a pre curved stainless steel instrument.  It is critical that the stop attachment be perpendicular and not oblique to the shaft of the instrument. Instruments like sterile metric ruler or a guage like Endo-M-Bloc are used.(INGLE) Disadvantages- 1.Time consuming 2.May move up or down the shaft leading to preparations short or past the apical constriction.
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   Instruments havebeen developed with millimeter marking rings etched or grooved in to the shaft of the instrument.  These act as a built in ruler with the markings placed at 18, 19, 20, 22, and 24 mm and commonly used with rotary nickel titanium instruments.
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  Techniques Radiographic 1. Grossman’s formula 2.Ingle 3. Kuttler 4. Best 5. Bregmen 6. Bramante 7. Radiographic grids 8. Digital monitoring systems Electronic Tactile Paper Point Patients response -Audiometric method -Apex locators
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  METHODS TO DETERMINEWORKING LENGTH Non-radiographic methods  Digital tactile sense  Periodontal sensitivity  Paper point measurement 21
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  DIGITAL TACTILE SENSEMETHOD • Earliest method • Clinician detect an increase in resistance as file approaches apical 2- 3mm. • Accuracy of just 64% (Seidberg et at)  Ineffective 1. In canals with immature apex 2. In canals which are constricted throughout 3. In canals with excessive curvature • Supplementary method 22
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  APICAL PERIODONTAL SENSITIVITY Based on patient’s response to pain • In cases of inflamed tissue ---- leads to shorter determination of working length • Non-vital teeth with peri apical pathology --overestimation 23
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  PAPER POINT METHOD Most reliable in root canal with  immature apex  Apical constriction is lost due to resorption  Initial paper point is placed 0.5 mm short of the EAL indicated length. If the point comes out dry, it is advanced apically in the canal in small increments (0.25 mm) until some fluid is picked up. Another paper point is used just short of this point, and the working length is then the maximum length that a point can be placed into the canal and remains dry. 24 (OOOE 2009;108:e101-e105)
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  Radiographic methods  Grossman’smethod  Ingle’s method  Wein’s method  Kuttlers method  X-ray grid system 25
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  Grossman’s method  Diagnosticradiograph is used to estimate the working length of the tooth from occlusal to root apex  Measurement is transferred to the instrument and placed in the root canal  Radiograph is made 26 Actual tooth length = Actual Length of instrument × Radiographic tooth length Radiographic length of instrument
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  Ingle’s method 27
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  WEINE’S MODIFICATION Weine’s recommendationsfor determining working length based on radiographic evidence of root/bone resorption. A. If no root or bone resorption is evident, preparation should terminate 1.0 mm from the apical foramen. B. If bone resorption is apparent but there is no root resorption, shorten the length by 1.5 mm. C. If both root and bone resorption are apparent, shorten the length by 2.0 mm.
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  Kuttler’s method Locate Major/MinorDiameter on the radiograph. 29 Estimate length of root on radiograph. Estimate width of root on radiograph If narrow use no 10/15 file, average- no 20/25 file & wide- no 30/35.
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  • Using fileselected by width, set the stop for the WL according to the measurement of length. place the file & take a radiograph. • If file appears too long/too short by 1mm from the Minor Diameter, make the interpolation, adjust the file accordingly & retake the film. • If your file reaches the Major Diameter exactly, subtract 0.5mm from that length for <35yrs old patient & 0.67 if older. 30
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  X-ray grid system In 1963 Everett And Fixott designed a diagnostic x-ray grid for determining the length of the tooth.  Consists of lines 1mm apart running lengthwise and crosswise  Every 5th millimeter is accentuated by a heavier line to make reading easier.  Disadvantage: • Inaccurate if radiograph is bent during exposure. • May obscure the file tip. 31
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  Disadvantages of radiographs Radiation hazards to patients as well as operator  Probably time consuming  Loss of bucco-lingual details  If rubber dam in place – taking radiograph becomes difficult  Gag reflex  Observer bias 32
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  Advancements in radiographicmethod  Xeroradiography  Digital radiography  Radiovisiography 33
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  XERORADIOGRAPHY  Not widelyused in endodontics, however they are superior to conventional radiographs.  It does not require a wet chemical processing or dark rooms.  Soft tissue and bone abnormalities are visible.  The anatomic structures of the tooth and periradicular tissues appear sharper. -Better edge contrast. - Rapid imaging. -Reduction in radiation.
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  RADIOVISIOGRAPHY It has threecomponents: 1. Radio- has sensitive intraoral sensor. 2. Visio – video monitor display processing unit. 3. Graphy- high resolution printers. -ADVANTAGES- -Reduction of radiation exposure. -Instantaneous image and display. -Control of contrast. -Elimination of X-ray film. -Ability to enlarge special areas. -Potential for computer storage.
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  ELECTRONIC METHOD  Workinglength is determined by comparing the electrical resistance of apical periodontal membrane with the gingiva surrounding the tooth and both should be similar.  The devices used for this are known as ‘‘apex locators’’.  One side of the apex locator’s circuitary is connected to an endodontic instrument. The other side is connected to the patient’s body.  The electric circuit is complete when the endodontic instrument is advanced apically into the root canal until it touches the periodontal tissue. The display on the apex locator indicates that the apical area has been reached.
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  ADVANTAGE Beneficial when radiographsare difficult to read E.g.: shallow palate apical portion obstructed by impacted teeth Patients in which radiographs cannot be taken. E.g.: excessive gag reflex, radiation necrosis. Useful in verifying perforations, root bifurcations and obstructions. 39
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  DISADVANTAGES 1. Cannot bethe sole criteria used for WL as success rate is low. 2. Incorrect readings in situations: 1. Battery too low 2. Too much tissue may remain in the canal 3. Canal may be too wet 4. Blockage may be present 5. Lip clip may fall off 3. Cannot help determine canal width, curvature, number. 40
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   Capacitor –A structure of 2 conductive material with an insulator between them form an electrical device called as capacitor. 41
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  • Impedance (Z):Total amount of opposition to an alternating current Z = V I 42 (Int Endod J, 39, 595–609, 2006)
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  Electrical Features OfThe Tooth Structure  If an endodontic file penetrates inside the canal, and approaches the canal terminus, the resistance between the end of the instrument and the apical portion of the canal decreases, because the effective length of the resistive material inside the canal decreases. 43 (Int Endod J, 39, 595–609, 2006)
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  • All apexlocators function by using human body to complete electric circuit. • One side of apex locators circuits connected to an endodontic instrument and other connected to patients body How does it work ? • All apex locators function by using human body to complete electric circuit. • One side of apex locators circuits connected to an endodontic instrument and other connected to patients body
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  CLASSIFICATION  Based ontype of current flow and the opposition to the current flow, as well as the number of frequencies involved: 1.Resistance Apex Locators (First Generation) 2. Impedance Apex Locators (Second Generation) 3. Frequency Apex Locators (Third Generation) 45
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  First generation • Resistanceapex locator (by Sunada) • In 1942, SUZUKI, showed that the electrical resistance between the periodontal ligament and oral mucosa was a constant value of 6.5 kΩ • Principle: measures opposition to the flow of direct current or resistance. 46
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   Ist generationapex locators:  Root canal meter  Endodontic meter  Endodontic meter S II  Dentometer  Endoradar  Apex finder  Requires a dry environment  Pain due to high electric current 47
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  Second generation  Impedanceapex locator  Principle: measures opposition to the flow of alternating current  The property is utilized to measure distance in different canal conditions by using different frequencies. 48 .
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  Frequency of thisimpedance is directed to a speaker that develops an audible tone generated by means of low frequency oscillations.  All 2nd generation ALs have similar problems of incorrect readings with electrolytes in the canals and also in dry canals. 49 (Int Endod J, 39, 595–609, 2006)
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   Second generationApex locators The Apex Finder (Sybron Endo) visual digtal LED The Endo Analyzer (Analytic/Endo) combined apex locator and pulp tester The Digipex II -combined apex locator and pulp tester The Exact-A-Pex-LED bar graph display and audio indicator The Foramatron IV (Parkell Dental)-flashing LED light and digital LED display The Pio (Denterials Ltd., St. Louis, Mo.) 50
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  Third generation  Frequencydependent apex locators Similar to the second generation except that they use multiple frequencies to determine the distance from the end of the canal.  These units have more powerful microprocessors and are able to process the mathematical quotient and algorithm calculations required to give accurate readings. 51 (Int Endod J, 39, 595–609, 2006)
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  THE ROOT ZX Kobayashi (1991) introduced development of the self-calibration root ZX based on “ratio method” (division method)  Uses dual frequency and comparative impedence principle  It comprises two sine waves with a high and a low frequency (fH and fL respectively).  The impedance of the model is measured at each frequency and the position of the file is determined from the ratio between these two impedances: Ratio =Z(fH) Z(fL) 52
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  • Root ZXis mainly based on detecting the change in electrical capacitance that occurs near the apical constriction. • The capacitance of a root canal increases significantly at the apical constriction, and the quotient of the impedances reduces rapidly as the apical constriction is reached. • Root ZX simultaneously measures 2 impedance at 2 frequencies {high (8kHz) & low (0.4kHz)} 53 (Int Endod J, 39, 595–609, 2006)
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  Tri Auto ZX(Dentaport)  Kobayashi (1997)  Cordless electric endodontic handpiece with RootZX  Accuracy: 95% Grimberg et al (2002)  3 automatic safety mechanisms:  Auto start stop mechanism  Auto torque reverse mechanism  Auto apical reverse mechanism 55
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  Fourth generation • Bingo1020/ Raypex 4 (dentsply) • uses two separate frequencies 400Hz and 8 kHz, but only a single frequency at a time. • Position of the file tip is calculated based on the measurements of the root mean square value of the signal. 56 (Int Endod J, 39, 595–609, 2006)
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  Raypex 5 Impedance measurementbased on advanced multi-frequency system Latest digital technology Apex zoom Represents the file movement along the entire root canal Blue – Beginning Of Apical Region. Green – Apical Constriction Region Yellow – Adjacent To Apical Foramen Red – Reached Apical Foramen Red Dot – Apex has been passed 57
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  Fifth generation  Ameasuring method has been developed based on comparisons of the data taken of the electrical characteristics of the canal and additional mathematical processing.  Devices employing this method perform very well in the presence of blood and exudate but they experience considerable difficulties while operating in dry canals. 58 Journal of IMAB - Annual Proceeding (Scientific Papers) 2009, book 2
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  Sixth generation  DENAPEXLowest Power Consumption Apex Locator.  The prolonged studies have made it possible to create a steady algorithm for adapting the method for measuring the working length of the root canal depending on the canal’s moisture characteristics.  The method has been implemented in the apex locator of the so called sixth generation – the adaptive type 59 Journal of IMAB - Annual Proceeding (Scientific Papers) 2009, book 2
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  Problems associated withthe use of apex locators  Biological phenomena such as inflammation can have an effect on accuracy  Intact vital tissue, inflammatory exudate and blood can conduct electric current and cause inaccurate readings.  conductors that can cause short-circuiting are metallic restorations, caries, saliva and instruments in a second canal.  Immature or ‘blunderbuss’ apices tend to give short measurements electronically 60
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  Other uses ofApex Locators: 1. To detect root perforations 2. Aid in diagnosis of external resorption and internal resorptions 3. Help in endodontic treatment of teeth with incomplete root formation requiring apexification. 4. Also reduce the number of radiographs.
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