Ultrasonics in endodontics

Ultrasonics In Endodontics

1. Ultrasonics in Endodontics Dr. Deepesh Mehta (Batch 2018) 1

2. Introduction History Ultrasound Biophysical Effects of Ultrasonics Ultrasonic Tips Application in Endodontics Guidelines Conclusion References Content 2

3. During the past few decades endodontic treatment has benefited from the development of new techniques and equipment, which have improved outcome and predictability. Ultrasonics (US) have found indispensable applications in a number of dental procedures in periodontology , to a much lesser extent in restorative dentistry, while being very prominently used in endodontics. 3 Introduction

4. Since its introduction, US has become increasingly more useful in applications such as gaining access to canal openings, cleaning and shaping, obturation of root canals, removal of intracanal materials and obstructions, and endodontic surgery. 4

5. The use of ultrasonics was first introduced in dentistry in 1951 for cavity preparations using an abrasive slurry. It never became popular, because it had to compete with the much more effective and convenient high-speed handpieces . 1955- Zinner reported the use of an ultrasonic instrument to remove deposits from the tooth surface. This was improved upon by Johnson and Wilson, and the ultrasonic scaler became an established tool in the removal of dental calculus and plaque. 5 History

6. The concept of using US in endodontics was first introduced by Richman in 1957, who first wrote about its application to root canal therapy and root resection. During the 1960s, researchers investigated the use of ultrasonics for cleaning instruments, removing stains from acrylic resin dentures, and in precision metal casting for dental purposes. In 1976, the term endosonics was coined by Martin and Cunningham and was defined as the ultrasonic and synergistic system of root canal instrumentation and disinfection. 6

7. Ultrasound is sound energy with a frequency above the range of human hearing, which is 20 kHz. The range of frequencies employed in the original ultrasonic units was between 25 and 40 kHz. Subsequently the so-called low-frequency ultrasonic handpieces operating from 1 to 8 kHz were developed, which produce lower shear stresses, thus causing less alteration to the tooth surface. 7 Ultrasound

8. There are two basic methods of producing ultrasound. The first is magnetostriction , which converts electromagnetic energy into mechanical energy. The principle of magnetostriction was discovered by James Joule in 1847. A stack of magnetostrictive metal strips in a handpiece is subjected to a standing and alternating magnetic field, as a result of which vibrations are produced. 8

9. The second method is based on the piezoelectric principle, in which a crystal is used that changes dimension when an electrical charge is applied. Deformation of this crystal is converted into mechanical oscillation without producing heat. The tips of these units work in a linear, back-and-forth, “piston-like” motion, which is ideal for endodontics 9

10. Magnetostictive Piezoelectric Active Surfaces

11. The physical effects created by the production of ultrasound are acoustic microstreaming , heat, cavitational activity. 12 Biophysical effects of Ultrasonics

12. The file oscillations are primarily responsible for the production of acoustic streaming, which is the movement of fluid in a vortex-like motion around the file when pressure waves are projected through it. Acoustic streaming may also be associated with the occurrence of cavitation . 13 Acoustic streaming

13. Cavitation refers to the oscillatory motions of gas-filled bubbles in an acoustic field, bubbles that are powered by energy from the ultrasonic field. The microscopic bubbles are formed and then collapse and explode, resulting in localized areas of pressure and heat production. This transient type of cavitational activity has been shown to occur around the tips of ultrasonic scalers . 14 Cavitation

14. Thermal imaging has been used to show that piezoelectric ultrasonic devices, as well as magnetostrictive ultrasonic units, produce heat when in contact with tooth structure or dental materials due to friction. The general heating effect can be minimized by using low and medium power settings, and also light contact, but water should be used to cool the tooth structure. 15 Heat

15. Ultrasonic activation is also able to increase the temperature of the surrounding irrigant in a root canal up to 10 degrees Celsius. It has been shown that heating sodium hypochlorite greatly increases tissue dissolution. 16

16. When an ultrasonic device is used with water coolant, aerosols are produced that can contain microorganisms and even blood contamination. These aerosols can remain airborne for some time. The use of an extraoral high-volume evacuation is able to significantly reduce the aerosols produced. The use of a preprocedural mouthrinse of 0.12% chlorhexidine or 0.05% cetylpyridinium chloride has also been shown to significantly reduce the microbial content of dental aerosols. 17 Aerosols

17. The current evidence on the effect of ultrasonic dental equipment on cardiovascular implantable electronic devices (pacemakers) is inconclusive. Current guidelines recommend the avoidance of magnetostrictive devices on those patients with pacemakers, whereas the use of piezoelectric devices does not appear to affect pacemakers. 18 Pacemakers

18. A great variety of ultrasonic tips are commercially available for endodontic, periodontal, surgical, and general practice uses. The tips manufactured by various companies are often able to be used on different piezoelectric ultrasonic devices, but one must check that the thread pattern on the unit and the tip is compatible. 19 Current Endodontic Ultrasonic Tips

19. Two different thread patterns, an E-thread and an S-thread, are currently used. The tips are also manufactured from a range of metal alloys, such as stainless-steel and titanium alloys, and can be coated with an abrasive such as diamond or zirconium nitride in order to increase the cutting efficiency of the tip. Many of the tips incorporate a built-in water port so that debris can be washed away and cooling can take place if desired. 20

20. Almost every ultrasonic tip for endodontic use incorporates a contra-angle bend that allows the clinician to have a virtually unobstructed view into the working area, and is most easily used with the aid of a surgical operating microscope. 21 ProUltra Endo Tips

21. Surgical endodontic ultrasonic tips incorporate a second bend placed closer to the end of the tip in order to allow parallel access to the root canal when creating retro-preparations. 22 ProUltra Surgical Endo Tips

22. As a result of the variety of tips available, there is an appropriate tip design for virtually every step of endodontic treatment, from access to obturation, each to be used in the recommended power setting range. 23

23. The ProUltra Endo Tips are numbered from 1 through 8, and are designed to address most intracoronal and intracanal procedures. These were designed by Dr. Clifford Ruddle . 24 Access Refinement Tips

24. ProUltra Endo Tips #1 through #5 are made of stainless-steel and are zirconium nitride-coated instruments for increased efficiency in cutting. ProUltra Endo Tips #6, #7, and #8 (20 mm, 24 mm, and 27 mm, respectively) are made from a titanium alloy. 25

25. ProUltra Endo #1 (17 mm) and #2 (17 mm) can be used from medium to high power, and feature a wider tip and design features suited to coronal disassembly, post removal, and the removal of larger pulp stones. ProUltra Endo #3 (17 mm), #4 (19 mm), and #5 (24 mm) are used from low to medium power, and feature increasingly longer and finer tips, suited to searching for hidden canals, troughing fine fins and narrow isthmuses, and removing separated instruments within the root canal. 26

26. ProUltra Endo Tips #6, #7, and #8 (20 mm, 24 mm, and 27 mm, respectively) are made from a titanium alloy and are used in the lower power range only. Due to the titanium alloy construction, these end-cutting tips have inherent flexibility and are mainly used for apical obstructions. 27

27. The ProUltra Endo Tips do not have a water port; water is used intermittently to wash away debris or for its cooling effects. The CPR line of tips from Obtura Spartan, also numbered from #1 to #8, are of similar design but are coated with diamond grit and have a water port. 28 CPR Ultrasonic Tips

28. Specialized tips designed specifically for the vibration of posts, such as the VT tip by SybronEndo or the VibraPost by B&L Biotech, feature a wide and blunt end designed to be placed, at maximum power, against a metal post. 29 SybronEndo VT B&L Biotech VibraPost

29. The BUC tips from Obtura Spartan are also a series of six access refinement tips. The range of six BUC tips feature a rounded tip, a flat disk-like tip for planing smooth pulp chamber floors, and a pointed, active tip for apical cutting. They are diamond-coated and contain a water port. 30

30. The ProUltra Surgical Endo Tips are a set of six instruments made from stainless-steel coated with zirconium nitride, like the ProUltra Endo Tips. However, the surgical tips have a water port, placed near the tip for better water delivery. When used during microsurgery, the various double angles allow specific tips to be used in certain quadrants of the mouth, and to reach difficult areas. The tip allows a 3 mm retropreparation to be made. 31

31. The KiS microsurgical tips by Obtura Spartan are a similar set of ten tips. These tips are also double-angled, feature a water port, have a 3-mm cutting surface and 0.5-mm tip diameter, but are coated with diamond grit. 32

32. The BK-3 tips from SybronEndo feature a microsurgical tip with three angled bends, providing access and visibility. The CT Tips, UT Tips, and SJ Tips from SybronEndo each address larger, moderate, and very fine retro-preparations, respectively. Designed by Dr. Gary Carr, they are made of stainless-steel, are uncoated, and feature a water port. Several of these tips are also available in a diamond-coated version. 33 UT Tips S J Tips BK-3 Tips

33. Recently, two ultrasonic irrigation needles have been available in the commercial market that have the additional feature of delivering irrigant during use either by a hand-held syringe or a peristaltic pump. They have been found to be at least as effective or more effective than other irrigation methods. 34 Ultrasonic Irrigation Systems

34. One such needle, the ProUltra ® PiezoFlow ™ Ultrasonic Irrigation Needle, is a 25-gauge flat open-ended needle made from stainless steel that is tightened into the ultrasonic handpiece with a wrench and used in the mid-range power setting in fully instrumented canals. A syringe or other irrigation source is attached to the Luer -lock connection on the ultrasonic needle through which irrigant is delivered. 35

35. The VPro ™ Stream Clean Ultrasonic Irrigation System (Vista) is a similar system except that the ultrasonic irrigation needle is a 30-gauge flat open-ended needle that is constructed from nickel–titanium. Much caution needs to be exercised when using an irrigation needle with a flat open-ended needle; the apical pressures created with a flat open-ended needle can be several-fold higher at irrigation flow rates exceeding 4 mL /min than when closed-ended side-vented needles are used. 36

36. The following is a list of the most frequent applications of US in endodontics, which will be reviewed in detail: Access refinement, finding calcified canals, and removal of attached pulp stones. Removal of intracanal obstructions (separated instruments, root canal posts, silver points, and fractured metallic posts). Increased action of irrigating solutions. Ultrasonic condensation of gutta-percha. 37 Applications in Endodontics

37. Placement of mineral trioxide aggregate (MTA). Surgical endodontics: Root-end cavity preparation and refinement and placement of root-end obturation material. Root canal preparation 38

38. One of the challenges in endodontics is to locate canals, particularly in cases in which the orifice has become occluded by secondary dentin or calcified dentin secondary to the placement of restorative materials or pulpotomies . In conventional access procedures, ultrasonic tips are useful for access refinement, location of MB2 canals in upper molars and accessory canals in other teeth, location of calcified canals in any tooth, and removal of attached pulp stones. 39 Access Refinement, Finding Calcified Canals, and Removal of Attached Pulp Stones

39. One of the most important advantages of ultrasonic tips is that they do not rotate, thus enhancing safety and control, while maintaining a high cutting efficiency. This is especially important when the risk of perforation is high. Care should be exercised while searching for canal orifices, as aggressive cutting may cause an undesired modification of the anatomy of the pulp chamber. 40

40. Clinicians are frequently challenged by endodontically treated teeth that have obstructions such as hard impenetrable pastes, separated instruments, silver points, or posts in their roots. If endodontic treatment has failed, these obstructions need to be removed to perform nonsurgical retreatment. Ultrasonic energy has proven effective as an adjunct in the removal of silver points, fractured instruments, and cemented posts. It has often been advocated for the removal of broken instruments because the ultrasonic tips or endosonic files may be used deep in the root canal system. 41 Removal of Intracanal Obstructions

41. The removal of an obstacle from a root canal must be performed with a minimum of damage to the tooth and the surrounding tissues. Too much destruction of tooth structure will complicate the restorative phase and as a result will most likely decrease the overall prognosis. 42

42. US has provided clinicians with a useful adjunct to facilitate post removal with minimal loss of tooth structure and root damage. Several studies point to the fact that ultrasonic vibration of posts facilitates their removal while conserving tooth structure and reducing the possibility of fractures or root perforations. 43

43. The effectiveness of irrigation relies on both the mechanical flushing action and the chemical ability of irrigants to dissolve tissue. Furthermore, the flushing action of irrigants helps to remove organic and dentinal debris and microorganisms from the canal. The flushing action from syringe irrigation is relatively weak and dependent not only on the anatomy of the root canal but also on the depth of placement and the diameter of the needle. It has been shown that irrigants can only progress 1 mm beyond the tip of the needle. 44 Increased Action of Irrigating Solutions

44. The only effective way to clean webs and fins is through movement of the irrigation solution, as they cannot be mechanically cleaned. US is a useful adjunct in cleaning these difficult anatomical features. It has been demonstrated that an irrigant in conjunction with ultrasonic vibration, which generates a continuous movement of the irrigant, is directly associated with the effectiveness of the cleaning of the root canal space. The flushing action of irrigants may be enhanced by using US. This seems to improve the efficacy of irrigation solutions in removing organic and inorganic debris from root canal walls. 45

45. The ability of NaOCl to dissolve collagen is enhanced with heat; therefore, the effect of heat on the irrigant produced by ultrasonic action plays an important role. Furthermore, van der Sluis et al. have postulated that ultrasonic irrigation should be more effective in removing debris from root canals with greater tapers. It appeared to be important to apply the ultrasonic instrument after canal preparation had been completed. Thirty seconds to 1 minute of ultrasonic activation seems to be sufficient to produce clean canals, whereas others recommend 2 minutes. 46

46. The technique of ultrasonic activation of an irrigant after instrumentation has been completed has been referred to as passive ultrasonic irrigation. The term passive is used to denote the intention to simply activate the irrigant, and not to cut or contact the dentin with the activated file, thus differentiating it from previous efforts to ultrasonically instrument the root canal walls. However, a recent study has shown that the file-to-wall contact during passive ultrasonic irrigation was actually rather significant; the file was in contact with the wall 20% of the activation time. As a result, it was recommended amending the term “passive ultrasonic irrigation” to “ultrasonically activated irrigation.” 47 Passive Ultrasonic Irrigation

47. Continuous ultrasonic irrigation is achieved by simultaneously and continuously delivering irrigation during ultrasonic activation through a water port incorporated into the ultrasonic tip. Unlike passive ultrasonic irrigation, the replenishment of irrigant with a conventional syringe between ultrasonic file activations is not required. Continuous ultrasonic irrigation has been shown to be more effective in clearing apically placed debris than other irrigation modalities. When comparing passive ultrasonic irrigation and continuous ultrasonic irrigation, both modalities have been shown to perform similarly in the removal of debris in a root canal. 48 Continuous Ultrasonic Irrigation

48. In another study, both modalities performed comparably and better than conventional syringe irrigation in the penetration of irrigant into simulated lateral canals. Infected lateral canals are a possible cause of recurrent or late endodontic treatment failure; delivering irrigant to the entire root canal system, including lateral canals, is important for the predictable long-term success of endodontic treatment. 49

49. Ultrasonically activated spreaders have been used to thermoplasticize gutta-percha in a warm lateral condensation technique. In some in vitro experiments, this was demonstrated to be superior to conventional lateral condensation with respect to sealing properties and density of gutta-percha. Ultrasonic spreaders that vibrate linearly and produce heat, thus thermoplasticizing the gutta-percha, achieved a more homogeneous mass with a decrease in number and size of voids and produced a more complete three-dimensional obturation of the root canal system. This technique has also been evaluated clinically with favorable results. 50 Ultrasonic Condensation of Gutta-Percha

50. Witherspoon and Ham described the use of US to aid in the placement of MTA. It was demonstrated that, with the adjunct of US, a significantly better seal with MTA was achieved. Placement of MTA with ultrasonic vibration and an endodontic condenser improved the flow, settling, and compaction of MTA. Furthermore, the ultrasonically condensed MTA appeared denser radiographically , with fewer voids. 51 Placement of Mineral Trioxide Aggregate (MTA)

51. Recent developments of new instruments and techniques have significantly enhanced the treatment outcome in apicoectomy with retrofilling . As the prognosis of endodontic surgery is highly dependent on good obturation and sealing of the root canal, an optimal cavity preparation is an essential prerequisite for an adequate root-end filling after apicoectomy . Since sonically or ultrasonically driven microsurgical retrotips became commercially available in the early 1990s, this new technique of retrograde root canal instrumentation has been established as an essential adjunct in endodontic surgery. 52 Surgical Endodontics

52. The first root-end preparation using modified ultrasonic inserts following an apicoectomy is attributed to Bertrand et al. Ultrasonic retrotips come in a variety of shapes and angles, thus improving some steps during the surgical procedures. At first glance, the most relevant clinical advantages are the enhanced access to root ends in a limited working space. This leads to a smaller osteotomy for surgical access because of the advantage of using various angulations and the small size of the retrotips . Ultrasonic tips can also be used to polish root end material and apical surfaces. Utilizing specific ultrasonic tips for refinement of the external radicular surface may be beneficial in the elimination of extraradicular bacteria, which may be responsible for infection 53

53. It is recommended that ultrasonic tips be used with a light touch and be kept moving during use, as an excessive force can significantly reduce the displacement amplitude of the tip. Studies have used a range of different contact loads, from 15-200 g of force, but a recent study has determined that the average trained endodontist uses 15 g of downward force during ultrasonic instrumentation. 54 Guidelines

54. Excessive forces or use of the tip in extremely narrow canals can also cause the ultrasonic tip to stall, in which case contact with the material being cut should be momentarily broken in order to allow the oscillations to re-establish themselves through the tip. The use of inappropriately high power settings can result in breakage of a tip in as little as 10seconds. 55

55. One final concern in the safe use of ultrasonic tips is the generation and transmission of heat to the supporting dental structures. The production of heat is not necessarily a terrible consequence and can be harnessed for a beneficial purpose, such as to increase the temperature of irrigants during ultrasonically activated irrigation. However, it has been shown that a temperature rise in the supporting bone beyond 47°C for a certain period of time can produce irreversible damage. 56

56. Intermittent use of the ultrasonic, with copious air or water coolant, has been shown to be effective in reducing the potential for serious heat-related injury to the periodontal tissues. 57

57. The piezoelectric ultrasonic device has the potential to become routinely incorporated into almost every component of endodontic treatment, re-treatment, and apical microsurgery. It is already indispensable as a precise tool with which the most challenging clinical situations, such as finding hidden root canals and removing root canal obstructions, can be done with relative ease, predictability, and conservancy. 58 Conclusion

58. Finally, integration of new technologies such as US, leading to improved techniques and use of materials, has changed the way endodontics is being practiced today. It can be concluded that ultrasonics is a good adjunct for irrigation, but cannot be recommended for routine root canal preparation. Ultrasonics can be helpful in selected situations. 59

59. Cohen’s Pathways of the Pulp: 11 th Edition. Ingle’s Endodontics: 7 th Edition. Gianluca Plotino et al. Ultrasonics in Endodontics: A Review of the Literature. Journal of Endodontics 2007, 33(2):81-95. Ellen Park. Ultrasonics in endodontics. Endodontic Topics 2013; 29; 125–159. 60 References