Sonics and ultrasonics in endodontics /certified fixed orthodontic courses by Indian dental academy

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  • 1. SONICS AND ULTRASONICS IN ENDODONTICS INDIAN DENTAL ACADEMY Leader in Continuing Dental Education www.indiandentalacademy.com www.indiandentalacademy .com
  • 2. CONTENTSINTRODUCTIONEVOLUTIONAN INSIGHT The Physics behind Ultrasonics The Physics behind SonicsBIOPHYSICAL EFFECTS OF ENDOSONICS Cavitation Acoustic StreamingIRRIGANTSULTRASONICSSONICSA COMPARATIVE ANALYSIS Shaping of Root Canals Canal Debridement Root end Preparation Endodontic Re-treatmentIntraradicular Post RemovalSilver Point RemovalGutta Percha RemovalSealer Placement and Gutta Percha ObturationCONCLUSION www.indiandentalacademy .com
  • 3. EVOLUTIONUltrasonic instrumentation was first introduced into dentistry in the form of a drill (Ctuna,1953; Balamuth, 1967)Such instruments were used with abrasive slurry for the preparation of tooth cavities priorto restorationThis technique however was superseded by the advent of the high-speed hand piece anda further development took place when Zinner (1955) recorded the use of an ultrasonicinstrument to remove deposits from the tooth surfaceJohnson and Wilson (1957) improved upon the instrumentation and the ultrasonic scalarbecame established in the removal of dental plaque and calculusThe idea of utilizing ultrasound in Endodontic therapy was suggested in 1957 by RichmanThis was not fully developed until 1976, when Martin developed a commercial systemharnessing the properties of ultrasonic energy in the preparation and cleaning of the rootcanalTronstadt et al in 1985 were the first to report on the use of a sonic instrument forEndodonticsThese techniques were termed as Endodontics by Martin and Cunningham and have nowbecome a well recognized endodontic procedure. www.indiandentalacademy .com
  • 4. AN INSIGHTEndosonics denotes a device, which imparts sinusoidal vibration of high intensity to aroot canal instrumentThe range, which is either or above that of audible perception, i.e. at ultrasonicfrequencies (20-42 kHz)Both ultrasonic and sonic instruments are, however, similar in design, in that they consistof driver, at the end of which is clamped an endosonic file usually at an angle of 60 to 90to the long axis of the driverIt is the oscillatory pattern of the driver that determines the nature of movement of theattached fileEndosonic instrumentation differs from hand and rotary instrumentation since the cuttingof dentin is facilitated by a mechanical device that imparts a sinusoidal motion to theinstrument by the transfer of vibrational energy along the shaft. www.indiandentalacademy .com
  • 5. The Physics behind UltrasonicsThere are two basic methods of producing ultrasoundThe first is Magnetostriction, which converts electromagnetic energy into mechanicalenergyA stack of magnetostrictive metal in the handpiece is subjected to a standing andalternating magnetic field, as a result of which, vibrations are producedThe second method is based on the Piezo-electric principleA crystal is used which changes dimensions when an electrical charge is appliedThis crystal deformation is converted to mechanical oscillation with no production of heatThe magnetostrictive units have the disadvantage, when compared with thePiezo-electric, that the stack generates heat and must be cooledThis means tubing is required to carry water to the hand piece, and if the irrigant issodium hypo chloride, then the water has to be led away by more tubing, after cooling thestackA separate source by more tubing carries the sodium hypochlorite to the head of thehand pieceBoth these types work at ultrasonic frequencies and exhibit similar patterns of theoscillation www.indiandentalacademy .com
  • 6. At the ultrasonic frequencies used, the main driver oscillates in a true longitudinalmanner, and as it moves back and forth a transverse wave is generated along the lengthof the endosonic fileThis transverse oscillation is characterized by a series of Nodes and Antinodes along thelength of the file, the nodes representing sites of minimum oscillation of displacement ofthe file and the antinodes representing sites of maximum oscillation or displacementThe tip of the file that is totally unconstrained will oscillate with the greatest displacementfrom restIt is this motion of the file that almost certainly causes abrasion (filing) of the canal wallswhen the instrument is moved vertically within the canalThe energy contained in the transverse oscillation of the file is low, however, comparedto that of the driverConsequently, if the file is constrained within a tightly fitting canal the oscillatory patternwill be reduced or even eliminatedThis is inefficient and more likely to occur in curved canals than straight onesIt is apparent that transverse oscillation is not a particularly effective mode of movementfor an endodontic procedure, as it may result in irregular cutting of dentin or uncontrolledfiling in the apical third of the root canal – dependent upon whether the file is constrainedor free with the canalA true longitudinal action of the file would be an advantage, as this would enable a filingaction to take place along the total length of the root canal. www.indiandentalacademy .com
  • 7. The Physics behind SonicsSonic instruments rely on the passage of pressurized air through the instrument handpiece in order to use, operating at either or around 3-65 kHzThe sonic instruments have a main driver, which in contrast to the ultrasonic driverproduces an elliptical pattern of oscillation during activationWhen the attached file is operated in air without any physical constraint, it sets up acircular motion characterized by single antinodes at the tip and a node near the driverThe action of the driver imparts both a vertical and lateral component to the action of thefileWhen the file is constrained is essentially eliminated, and a true vertical or longitudinalfile movement remainsThis difference is oscillatory pattern may explain the reportedly superior efficiency of thesonic instrument during clinical use. www.indiandentalacademy .com
  • 8. BIOPHYSICAL EFFECTS OF ENDOSONICSCavitationCavitation is defined as the growth and subsequent violent collapse of a small gas filledpre-existing in homogeneity in the bulk fluidWhen a vibrating object is immersed in a fluid, oscillations are set up in the fluid, whichcause local increases (compression) and decreases (rarefaction) in fluid pressureDuring the rarefaction phase, at certain pressure amplitude, the liquid can fail underacoustic stress and form cavitation bubblesDuring the next positive pressure phase, these primarily vapor filled cavities implusivelycollapse, producing radiating shock wavesCavitation has been shown to be useful in the removal of tooth deposits during operationof the ultrasonic scaler, as the scaler has a larger surface area and displacementamplitude, and thus is able to generate the threshold acoustic pressure amplitudenecessary to induce cavitationAlthough it is theoretically possible that cavitational activity occurs also around theoscillating endosonic file, it is highly unlikely that a confined area such as a root canalwould increase the probability of cavitation inception. www.indiandentalacademy .com
  • 9. There are several reasons for this:The threshold power setting at which this phenomenon would occur is beyond the rangethat is normally used for endodontic purposesCavitation inception depends on free displacement amplitude of the file. This would beimpossible to achieve during instrumentation, as damping of the displacement amplitudeis inevitable when the file contacts the canal wallsThe conditions under which a boundary would enhance acoustic cavitation is one inwhich there would be a reflection of acoustic energy from the boundary with such a phasechange as to lead to generation of standing waves within the volume of the liquid beingexaminedSince it is necessary for such a boundary to be at least one half wavelength away, andthe wavelength of sound in water at a frequency of 25 kHz is 6 cm, the production ofstanding waves (and thus cavitation enhancement due to doubling of the acousticpressure amplitude) would not be possible within a root canalA root canal has thus to be at least 6 cm in diameter for standing waves to form, whichone does not encounter clinically www.indiandentalacademy .com
  • 10. Acoustic StreamingAcoustic streaming is defined as the generation of time independent, steadyunidirectional circulation of fluid in the vicinity of a small vibrating objectWhen a vibrating file is immersed in a fluid, the file is observed to generate a streamingfluid comprising two components:- The primary field consisting of rapidly moving eddies in which the fluid element oscillates about a mean position Thesuperimposed secondary field consisting a patterns of relatively slow, time I ndependent flowCharacterstically the fluid is transported from the apical end to the coronal endThese flows of liquid have a small velocity, of the order of a few centimeters per second,but because of the small dimensions involved the rate of change of velocity with distancefrom the file is highThis results in the production of large hydrodynamic shear stresses around the file, whichare more than capable of disrupting most biological materialIn a endosonic file the greatest shear stresses will be generated around points ofmaximum displacement, such as the tip of the file and the antinodes along its length andit is probable that will also be important in moving the associated irrigant around the canalso that maximum benefit is achieved from the chemical irrigantAlthough either type of endosonic instrument (sonic and ultrasonic) is capable ofproducing acoustic micro streaming, the clinical efficiency of such forces will bedependent upon the amount of file constraint that occurs – especially in tight or curvedcanals. www.indiandentalacademy .com
  • 11. IRRIGANTSThe four goals of irrigation that one must take into account are lavage of debris, tissuedissolution, antibacterial action and lubricationAlthough preliminary debridement is accomplished with hand instruments irregularitieswith debris and pulp tissue that current endodontic instrumentation could not be removedOne must therefore rely on lavage and some means of chemical dissolution of theremaining tissueConsequently, the ability of the irrigant to act as an effective organic solvent is of clinicalimportanceThis enhancing feature of the irrigant is one dimension of the improved physic chemistryof irrigation within the multi dimensional endosonic systemThere are several important aspects of irrigating root canals they use are the types orirrigant used, the quantity of irrigant, temperature of the solution and its shelf lifeThe type of irrigant that should be used is agreed by most authorities to be Sodiumhypochlorite. It fulfils most of the requirements of an ideal irrigant by being bactericidaland capable of dissolving organic debrisAn agreement has not been reached on the optimum concentrations, although Martin andCunningham have recommend 2.5 per cent. Yet, it remains the most recommendedirrigant due to its synergistic effect with Endosonics. www.indiandentalacademy .com
  • 12. The phrase ‘copious irrigation’ is often found in the literature, yet this can be misleading,as it is the quantity of irrigant that circulates to and from the apical limit of the root canalthat is important.It has been found that with an irrigant flow of 20 ml per minute, it takes around 30seconds for the irrigant to reach the most apical extent of the canal space.Thus, an irrigant with solvent qualities used in large volumes and enhanced by ultrasonicactivation and mechanical energizing will be superior to conventional irrigant actionThe temperature of the sodium hypochlorite is relevant because if it is heated from 21 to37C its ability to dissolve collagen is enhancedIt has been pointed out that with continuous irrigation there is no heating effect in thecanal, therefore it may be of benefit to preheat the irrigant in the reservoir within theendosonic unitHowever sodium hypochlorite warmed to 37C remains stable for no longer than 4 hoursbefore breaking downThe shelf life of NaOCl varies with the concentration being employedFor example it has been found that the stable shelf life of 5.25% NaOCl is 10 weeks,whereas 2.6% and 1.0% remain stable for only 1 week after mixing with water www.indiandentalacademy .com
  • 13. ULTRASONICSUltrasonic Endodontics is based on a system in which sound as an energy source (at 20to 42 kHz), activates an endodontic file resulting in three dimensional activation of the filein the surrounding mediumThe ultrasonic systems (Magnetostrictive and Piezo-electric) involve a power source towhich an endodontic file is attached with a holder and an adapterUltrasonic handpieces use K-files as a canal instrumentBeginning at ISO size 15, they range upto size 40Before a size 15 can fully function, however, the canal must be enlarged with handinstruments to a size 20Martin also designed a stiff, non-end cutting diamond file to be used in the straight part ofthe canalThe irrigants are emitted from cords on the power source and travel down the file into thecanal to be energized by the vibrations. www.indiandentalacademy .com
  • 14. SONICSThe only similarity between the ultrasonic and sonic instruments is in imparting vibrationaltype of movement for the root canal instrument, which they activateThe rest of the features such as the source of power, frequency of vibration, type ofhandpiece and root canal instruments used are all differentFurther more, unlike Ultrasonics, sonic system does not require special connections, as itinvolves only a hand pieceSonic instruments use compressed air line at a pressure of 0.4 MPa, which is alreadyavailable in the dental unit setup, as its source of powerThere are two options for irrigating the root canal while using sonic handpiecesEither the water line of the dental units can be attached to the sonic handpiece, or thewater can be cut off and the dental assistant can introduce sodium hypochlorite from asyringeSonic handpieces impart vibrations usually in the frequency of 1.5 – 3 kHz with provisionfor adjusting the frequency, in the form a ring on the handpiece.The root canal instruments which sonic handpieces use are specially designed and areunique.The three choices of files that are used with sonic handpieces are the Rispi sonic, Shapersonic and the Helio sonicThe Rispi sonic file resembles a rat-tail file and was developed by Dr.Retano SpinalThe Shaper sonic files were developed by Dr.J.M.Laurichesse and resemble a huskybarbed broach The Helio sonic file is otherwise known as Trio sonic or Triocut file andresembles a triple helix Hedstrom fileAll these instruments have safe ended non-cutting tip 1.5 – 2.0 mm in lengthThe ISO sizes of these instruments range from 15 to 40As the graduated size instruments have varying shaft sizes, the instrument must be tunedwith the unit’s tuning ring to optimum tip amplitude of 0.5 mm. www.indiandentalacademy .com
  • 15. COMPARATIVE ANALYSISShaping of Root CanalsHigh efficiency of Ultrasonics in dentin removal with reduced operator fatigue raised thehope that it would be an ideal power driven device for root canal preparationHowever, the results achieved by the ultrasonic units have ranged from outstanding todisappointingThe explanation for such wide variance in results lies in the difficulty of controlling theexact position of the tip and also the vibration of the file inside the canal curtails its hopeas a precise tool for root canal preparation, particularly the apical partOne of the uncharted problems with the ultrasonic units is their choice of enlarginginstrument – the K fileThese files are made to function best in a push-pull, in and out motionThe action of the ultrasonic units, however, is an oscillating side-to-side, transversemotionWalmsley and Williams suggested that the devices would work much better if thetransverse motion could be changed to an up and down, longitudinal oscillationMay be rather than change the configuration of motion, the problem would be bettersolved by changing thte canal instruments into a shape that functions better in anoscillating fashion www.indiandentalacademy .com
  • 16. Ultrasonics will be of use in root canal preparations of its limitations and characteristicsare fully understood. Improper use of Ultrasonics may cause straightening or excessiveremoval of the canal wall, ledging or perforationIn curved canals, only size 15 files can be usedSizes 20 and above have been shown to cause straightening of the canal and apicaltransportationIn the mesial roots of molars proper care should be shown as Ultrasonics may cause stripperforationsIt has been reported that many factors such as power setting, the interfacial forcebetween the file and dentin, direction of file oscillation, root canal geometry, type ofirrigant and the super imposition of operator assisted movement of the file may affect thefinal shape of the preparationHence, using exclusively Ultrasonics for the preparation of root canal may not be apredictable procedureHowever, if used judiciously along with hand instruments, Ultrasonics may be a usefuladjunct for root canal preparations www.indiandentalacademy .com
  • 17. The unique oscillatory pattern of sonic files has made them a powerful root canal shapingdeviceAs with the ultrasonic canal preparations, these instruments must be free to oscillate inthe canal, to rasp away at the walls and to remove necrotic debris and pulp remnantsTo accommodate the smallest instrument, size 15, the canal must be first handinstrumented upto size 20The sonic instruments, with their 1.5-2.0 mm safe tips, begin their rasping action this farremoved from the CDJ. This is known as the ‘Sonic Length’. As the instrument becomesloose in the canal, the next size instrument is used thus developing a flaring preparation.The Rispi sonic and the Shaper sonic files are more effective in canal shaping than theHelio sonicBolanos et al found that the Shaper files left the least debris in the apical third and theRispi sonic the least in the middle and coronal thirds. Hence, it is recommended that theShaper sonic files be used first and that the remaining two thirds of the canal be finishedwith the Rispi sonic.The Sonics also cause least amount of straightening of canals when compared with theUltrasonics. The sonic technique also extrudes the least amount of apical debris whencanals merely irrigated during preparation and those canals prepared and then followedby 3 minutes of ultrasonic instrumentation with a No.15 file and 5.25% NaOClThe antibacterial efficacy of irrigants in Endosonics was further proved when the viablecounts of bacteria dramatically rerduced when water as an irrigant was replaced byNaOCl. www.indiandentalacademy .com
  • 18. Root end PreparationAlthough conventional endodontic therapy has been shown to be successful in 90% ofcases, a surgical approach is frequently indicated when a treatment through the canal isnot possibleRoot end preparation and retrograde filing are commonly performed during endodontictherapy when the quality of the apical sealing is doubtfulThus, root end preparation is one of the most crucial factors in achieving success insurgical endodonticsRecently, Ultrasonic retro preparation technique was devised to address the majorshortcomings of conventional rotary bur type of preparationsThey are increasingly becoming popular and appear to have many advantages, such asmore conservative preparations, less need for beveling the root tip (decreasing thechances of micro leakage), the the ability to prepare the canal farther in a coronaldirection from the apex with parallel walls for better retentionThe dentin walls are also cleaner with less debris and smear layerThese special retro tipsare only 1/4mm in diameter, 3 mm in length, and about 1/10th the size of a conventionalmicro head handpiecePlacing them in the long axis of the canal and then activating the ultrasonic unit usethem. It vibrates in the range of 30-40 kHz and a root-end cavity is prepared with parallelwalls 2.5 to 3 mm in depth www.indiandentalacademy .com
  • 19. Continuous irrigation cools the surface and maximizes cutting and debridementAlthough Ultrasonics have made retro preparation of root apex simpler, easier and moreeffective, long term clinical studies are warrantedRetro preparations tips specially designed for periapical surgeries are also available forsonic handpiecesThey are available in three standardized sizes (#35, #45, #55) and in two different lengths(2mm, 3mm)Although they are versatile in their angulations and can adapt to the variousconfigurations of the root apex, they are not very effective when compared to theultrasonic retro preparation tips. www.indiandentalacademy .com
  • 20. ENDODONTIC RE-TREATMENTIntraradicular Post RemovalTeeth that present with intraradicular posts and periapical infections can be difficult toretreat from a coronal approachA traumatic and efficient post removal is essential for optimal non-surgical clinicalmanagement.Ultrasonics are highly efficient as post removal can be achieved with minimal loss oftooth structure and decreased risk of other root damageUltrasonic instrumentation for post removal typically involves removing coronal cementand build up material from around the post, then activating the tip of the ultrasonicinstrument against the metal postThe ultrasound energy transfers to the post and breaks down the surrounding cementuntil the post loosens and is easily removed. Sonic instruments are ineffective atremoving cemented postsIt is possible that the frequency or amplitude of the vibrations play a key role in removingthe postsRegardless of the method of sonic vibration, these instruments cannot be recommended www.indiandentalacademyfor removal of cemented posts clinically. .com
  • 21. Silver Point RemovalThe tightly fitted, well cemented silver cone that is flush with the canal orifice is achallenge to removeIn such cases, removal is enhanced through the use of ultrasonic devicesA conservative approach for removing defective silver points has been advocated by KrellIn this technique, a fine Hedstrom file is placed down into the canal alongside the silverpointThe file is then enervated by the ultrasonic tip and slowly withdrawn. A number of triesare usually necessary before the silver point is loosened and retrieved. www.indiandentalacademy .com
  • 22. Gutta Percha RemovalMany endodontist believe that endodontic success depends more on what is taken out ofthe canal (i.e. bacteria and necrotic tissue) than on what is put in itThe same is true for endodontic re-treatment. It is important to remove as much sealerand gutta percha as possible in order to uncover remnants of necrotic tissue or bacteria,which may be responsible for the endodontic failureUltrasonic instrumentation alone or with a solvent is as effective as hand instrumentationin removing gutta percha from root canalsThe ultrasonic-chloroform technique may produce residual slurry that may coat the canalwallIn contrast, when halothane is employed it results in quick retrieval of the bulk of the fillingmaterial and leave minimal residual debrisAlthough ultrasonic instrumentation require less time than hand instrumentation to attainthe working length, it uses significantly more solvent (chloroform or halothane) becausethe solvent not only acts as an irrigant but also gets volatilized www.indiandentalacademy .com
  • 23. Sealer Placement & Gutta Percha ObturationThe significance of sealer consistency and placement has not been fully appreciated bythe practicing clinicianThey constitute one of the most important variables, which determine the success ofEndodontic therapyA novel method of sealer placement is by using an ultrasonic file – run without fluidcoolant, of courseA recent study found ultrasonic endodontic sealerplacement significantly superior to handreamer placementThey found the lateral and accessory canals well filled, with a proper coverage of thesealer upto the apical orifice but not beyondA common problem encountered with this technique is the “whipping up” of the cement inthe canal and causing it to set prematurelyThis problem can be solved to an extent by replacing the ZnO-Eugenol sealer with a resinsealer like AH-26The Helio Sonic files are also equally useful for coating the canal wall with sealers and forplacing calcium hydroxide pastes www.indiandentalacademy .com
  • 24. Moreno’s ProcedureMoreno first suggested the technique of plasticizing gutta percha in the canal with anultrasonic instrumentHis technique advocated the placement of gutta percha points to virtually fill the canal.The attached endodontic instrument is then inserted into the mass and the ultrasonicinstrument is then activatedThe gutta percha gets plasticized by the friction being generatedFinal vertical compaction is done with hand or finger pluggersA variation of this technique is in not attempting to plasticize the gutta perchaUltrasonic energy is used only to condense the gutta percha mass with a spreaderThis energized spreading technique leads to a more homogenous compaction of perchawith less stress and microleakage www.indiandentalacademy .com
  • 25. CONCLUSIONIn an ultrasonic instrument the main driver oscillates in a true longitudinal manner, and asit moves back and forth a transverse wave is generated along the length of the file withthe formation of a series of Nodes and Antinodes along the length of the fileHowever, in a sonic instrument a circular motion characterized by single antinodes at thetip and a node near the driver is generatedThe action of the driver imparts both a vertical and lateral component to the action of thefileThus, when the file is constrained within a root canal, this lateral component is essentiallyeliminated, and a true vertical or longitudinal file movement remainsThis difference is oscillatory pattern may explain the reportedly superior efficiency of thesonic instrument during clinical usageContrary to earlier reports, it is highly unlikely that a confined area such as a root canalwould increase the probability of cavitation inceptionRecent research has shown that the hydrodynamic shear stresses caused by theacoustic streaming fields are responsible for many of the beneficial effects attributed tothe use of EndosonicsIrrigants play a crucial role in both short and long term success of endodontics throughtheir debriding and antimicrobial action. Sodium hypochlorite when activated withEndosonics makes a potent synergistic combination for the efficient debridement of thepulp space. www.indiandentalacademy .com
  • 26. www.indiandentalacademy.com