working length by different method dental
- 1. According to endodontic glossary working length is defined as “the distance from a coronal reference point to a point at which canal preparation and obturation should terminate”. WORKING LENGTH
- 2. Fig. The apical canal anatomy TERMINOLOGIES 1. Reference point: site on occlusal or the incisal surface from which measurements are made. 2. Anatomic Apex: the tip or the end of the root determined morphologically. 3. Radiographic Apex: the tip or the end of the root determined radiographically. 4. Apical Forman (major diameter): it is the main apical opening of the root canal. It is frequently eccentrically located away from the anatomic or radiographic apex. 5. Apical Constriction (Minor Diameter): It is the apical portion of the root canal having the narrowest diameter.
- 3. Methods of Determining Working Length:- A. RADIOGRAPHIC METHOD 1. Grossman’s Method 2. Ingle’s Method 3. Kuttler Method 4. Best’s Method 5. Bregman’s Method 6. Bramante’s Method 7. X-ray Grid System 8. Xero Radiography 9. Direct Digital B. NON-RADIOGRAPHIC METHOD 1. Apex Finder 2. Audiometric Method 3. Tactile Method 4. Paper Point Evaluation Method 5. Electronic Apex Locators.
- 4. A. RADIOGRAPHIC METHOD :- 1. Grossman method
- 5. 2. INGLE’S METHOD Diagnostic radiograph used to estimate working length by measuring tooth from stable reference point till radiographic apex. Substract atleast 1mm from this length On radiograph measure difference between end of instrument and radiographic apex of root -short -accurate -beyond
- 6. 3. Kuttler’s method The basis for this method’s value is the measurement provided by Kuttler relating to the distance between the major diameter (site of exiting of the canal) and the minor diameter (i.e. the CDJ). In younger patients the distance between these two positions is approx 0.5 mm and in older patients due to increased build-up of cementum the distance is approx. 0.67 mm. 4. Best’s method :- In 1960 BEST described a technique for determining the tooth length. In this method a steel pin measuring 10 mm is fixed to the labial surface of the root with utility wax keeping the pin parallel to the long axis of the tooth and a radiograph obtained. The radiograph is then carried to a gauge, which would indicate the tooth length.
- 7. 5. Bramante’s method . Calliber probes were bend at one end at right angel and this bend is inserted partially in acrylic resin in such a manner that its internal surface is in flush with the resin surface contacting the tooth surface. The probe is introduced into the root canal so that the resin touches the incisal edge or cusp tip taking care to see that the bend segment of the probe would be parallel to the mesio-distal diameters of the crown thus making it possible to visualize it on the radiograph. Then the tooth is radiographed. In this radiograph the reference points are as follows. A-Internal angle of intersection of incisal U radicular probe segment. B-Apical end of the probe C-Tooth apex Measuring the radiographic image length of the probe. A-B, measuring the radiographic image length of the tooth from A to C and then measuring the real length of the probe.
- 8. Now the following equation is applied CRD-Real tooth length CRS-Real instrument length CAD-Tooth length in radiograph CAS-Instrument length in radiograph CRD-CRS x CAD / CAS Measuring the distance between the apical end of the probe and the tooth apex in the radiograph. This measure is either added or diminished to obtain the correct length of the tooth. This is somewhat similar to that described by Ingle.
- 9. Everett & Fixott in 1963 designed a diagnostic X-ray grid system for determining the length of the tooth. Enameled copper wires are placed in plexi-glass and fixed to a regular periapical film. The grid is taped to film to lie between the tooth and film during exposure so that the pattern becomes incorporated in the finished film. 7. X-RAY GRID SYSTEM 8. XERORADIOGRPHY Xero-radiography records images produced by x-radiation but differs from conventional radiography in that it does not require wet chemicals or dark room for processing. In endodontics, Xero-radiographs permit better visualization of pulp chamber morphology, root canal configuration and root outline. This is especially evident in maxillary molars and pre molars, in which zygomatic arch and maxillary sinus super-impositions will hinder accurate visualization of dental structures. The lamina-dura is also clearly observed.
- 10. B. Non-radiographic methods :- 1. Apex finder :- Introduced by M.M.Negm in 1982 novel method of determining the length of root canal without the use of radiographs. The new instrument apex finder is used to locate the apex as well as measuring the root length. The application of this method is based on insertion of a fine plastic tapered bared shaft through a beveled tube into the root canal. When resistance to withdrawl is felt which indicates that some barbs have engaged the apical margin, the shaft is marked at the level of the cusp tip. The distance between the mark and the barbs, which caused the resistance, is measured. 2. Audio metric method -principle of electrical resistance of comparative tissue using a low frequency oscillation sound to indicate when similarity to electrical resistance has occurred by a similar sound response. By placing an instrument in the gingival sulcus and including an electric current until sound is produced and then repeating this by placing an instrument through the root canal until the same sound is heard, one can determine the length of the tooth.
- 11. 3. TACTILE METHOD :- The experienced clinician develops a keen tactile sense and can gain considerable information from passing an instrument through the canal. Following access, when interferences in the coronal third of the canal are removed, the observant clinician can detect a sudden increase in resistance, as a small file approaches the apex. Careful study of the apical anatomy discloses two facts that make tactile identification possible. i. The unresorbed canal commonly constricts just before exiting the root . ii. It frequently changes course in the last 2-3 mm. 4. Paper point evaluation The paper point may be used to detect bleeding or apical moisture. A bloody or moist tip suggests an over extended preparation. Further assessment of the apical preparation and working length should be made. The point of wetness often given an approximate location to the actual canal end point. 5. Periodontal sensitivity test
- 12. Electronics apex locator The apex of the root has a specific resistance to electric current which is measured using a pair of electrodes i.e. endodontic fie & lip clip. An electronic method for root length determination was first investigated by Custer (1918).
- 13. 1. First Generation Electronic Apex Locators (Resistance Type): These are also known as Resistance Based Apex Locator, measures opposition to the flow of direct current or resistance. Example: Root canal meter and dentometer 2. Second Generation Electronic Apex Locators (Impedance Type):- Second generation apex locators are impedance type operates on the principle that there is electrical impedance across the wall of the root canal due to the presence of transparent dentin. The tooth exhibit increase in electrical impedance across the walls of the root canal, which is greater apically than coronally. At the cemento-dentinal junction the level of impedance drops dramatically. A major disadvantage of these devices was that of electro-conductive materials gives inaccurate readings. Examples : 1. Foramatron IV, Digipex I, II, III, Endo Analyzer.
- 14. 3. Third Generation Electronic Apex Locators (Frequency dependent comparative impedance Type): Third generation EALs are similar to the 2nd generation EALs except that they use multiple frequencies to determine the distance from the end of the canal. . Since the impedance of given circuit may be substantially influenced by the frequency and the current flow, these devices have been called “Frequency Dependent”. Example: Justy II, Apex Finder, Neosono-D, Apit 7, Root ZX. 4. Fourth Generation Electronic Apex Locators (Ratio Type): These are Ratio Type apex locators which determine the impedance at five frequencies. A significant disadvantage of the fourth generation devices is that they need to perform in relatively dry or in partially dried canals. In some cases, this necessitates additional drying. Also in heavy exudates or blood it becomes inapplicable. Example: propex, iroot.
- 15. 5. Fifth Generation Electronic Apex Locators (5t GEALs) (Dual Frequency Ratio Type): It measures the capacitance and resistance of the circuit separately. It is supplied by diagnostic table that includes statistic of the file. They have best accuracy in any root canal condition (dry, wet, bleeding, saline, EDTA, NaOCl). Devices employing this method experience considerable difficulties while operating in dry canals. During clinical work it is noticed that the accuracy of electronic root canal length measurement varies with the pulp and periapical condition. Examples: Apex Locator Joypex 5, Raypex 5
- 16. Recent advances:- Tomography:- Is a radiographic technique that “slices” teeth in thin sections. Computers subsequently reassemble the sections to generate a three-dimensional image. Dental anatomy including bucco-lingual curvatures shapes of the root canal spaces and location of the apical foramen (which is important in determining or calculating the working length) can be visualized in the third-dimension. DDR- Fourth generation DDR: one of the more recent additions to Trophy’s fourth generation RVG systems is the capability of on screen point-to-point measurements using multiple additive points. This capability potentially allows for fast accurate working length estimation in roots demonstrating severe apical curvatures.
- 17. Videography and Intra-Oral Cameras:- Intra-oral videography is an non-ionizing diagnostic imaging technique. Developers are using miniature colour CCD (charge coupled device) chips. With fiber optic probes to assemble video cameras small enough to transverse periodontal defects and identify vertical root fractures. These devices are useful in endodontics as they can display canal morphology as well aid in locating canal orifices. Perforations can be visualized by inserting the fiber optic probe down the suspected canal.
- 18. No individual technique is truly satisfactory in determining endodontic working length. Modern electronic apex locators can determine this position with accuracies of greater than 90% but still have some limitations. Knowledge of apical anatomy, prudent use of radiographs and the correct use of an electronic apex locators are user friendly, less time consuming and reliable in most of the clinical situations
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