Ultrasonics in Endodontics: Part 1
Fig. 1

Magnetostriction converts electromagnetic energy into mechanical energy. 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. A magnetostrictive device creates more of an elliptical motion, which is not ideal for either surgical or nonsurgical endodontic use and have also the disadvantage that the stack generates heat, thus requiring adequate cooling.

Ultrasonics in Endodontics: Part 1
Fig. 2

Based on the piezoelectric principle, which uses a crystal that changes dimension when an electrical charge is applied. Deformation of this crystal is converted into mechanical oscillation without heat production.
Piezoelectric units have some advantages with respect to earlier magnetostrictive units as they offer more cycles per second, 40 versus 24 kHz. The tips of these units work in a linear, back-and-forth, piston-like motion, which is ideal for endodontic applications.

Ultrasonics in Endodontics: Part 1
Fig. 3

Besides ultrasonic devices, also sonic instruments are used in endodontics, with a frequency from 1500 to 6000 hz (Micro-Mega Sonic Air, KaVo SonicFlex Endo) for detection and preparation of the canal orifices, for removal of soft materials and for canal preparation with continuous irrigation.

Ultrasonics in Endodontics: Part 1
Fig. 4

Another sonic device (EndoActivator) is used to activate intra-canal irrigants during endodontic treatment.

Ultrasonics in Endodontics: Part 1
Fig. 5

Piezosurgery devices have been developed for bone surgery, and have found applications in endodontic surgery, for osteotomy, root-end resection and retropreparation. A recent literature review (Abella JOE 2014) found no published data on the effect of piezosurgery on the outcomes of endodontic surgery; no study has evaluated the effect of piezosurgery on root-end resection, and only one has investigated root-end morphology after retrograde cavity preparation using piezosurgery. From anecdotical reports, it looks that piezosurgery results in less bleeding, less swelling and less postoperative pain.

Ultrasonics in Endodontics: Part 1
Fig. 6

To this day, a variety of ultrasonic tips have been introduced on the market, both for orthograde and retrograde RCT.
All of these can normally be used on different piezoelectric ultrasonic devices, but one must check that the thread pattern on the unit and the tip is compatible (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.
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.

Ultrasonics in Endodontics: Part 1
Fig. 7

The active tip makes an extremely effective tool when used for fiber post and obstacles present in pulp chamber removal and in all the circumstances in which there is a good view and a low risk of creating iatrogenic injury.
The smooth tip is useful in the cases in which cutting action is not necessary on the tip but is exerted by the body of the instrument. This is useful in pulp stone and intracanal obstructions (such as post) removal.

Ultrasonics in Endodontics: Part 1
Fig. 8

The diamond coating of an ultrasonic tip makes it much more effective and abrasive.
This kind of tip, especially if used without irrigation, tend to get soiled with dentinal debris thus loosing cutting efficacy. Furthermore, the diamond part is likely to, overtime, get consumed and to detach from its site.
Surface coatings on ultrasonic tips are intended to increase efficiency and durability; diamond-coated tips have been shown to require less time than stainless-steel tips or zirconium nitride tips to cut similar preparations.

Ultrasonics in Endodontics: Part 1
Fig. 9

Among the uncoated diamond tips we can find those with a smooth surface and those milled surface.
The tips with milled surface have a higher lateral cutting ability and longer lasting even compared to the coated diamond tips.

Ultrasonics in Endodontics: Part 1
Fig. 10

The ultrasonic tips Nickel-Titanium are much more fragile than stainless-steel, are used to work at a low intensity within the channel. They should be activated when in contact with the canal walls otherwise they tend to fracture.

Ultrasonics in Endodontics: Part 1
Fig. 11

The endodontic instruments as K-files mounted on Endochuck or as independent files inserts may be used for:
- Activation of irrigants to increase its effectiveness
- Removal of obstacles intracanal, especially positioned in the medium-apical third canal (like broken files)
- Allow the achieving and positioning of MTA in the third apical canal

Ultrasonics in Endodontics: Part 1
Fig. 12

Ultrasonic technique has changed completely the endodontic surgery, opening the way towards endodontic microsurgery, along with magnification and coaxial illumination. Specially designed ultrasonic tips are used for root-end preparation, allowing an accurate, centered and deep preparation of the canal.

Ultrasonics in Endodontics: Part 1
Fig. 13

As for the root canal instruments, also for the use of the ultrasonic instruments, it is appropriate to make a clinical classification according to the tooth section in which they must operate.
Therefore the choice of each tip type (active/non active, smooth/milled), the intensity of use, the use with or without water will be in close relationship with the area in which it will have to work.

Ultrasonics in Endodontics: Part 1
Fig. 14
Ultrasonics in Endodontics: Part 1
Fig. 15
Ultrasonics in Endodontics: Part 1
Fig. 16


It is interesting to consider that only 20 years ago, the rationale for the use of ultrasonics in endodontics was considered controversial, as it is now an integral tool during most tasks and challenges of root canal therapy.
In the next article, Ultrasonics in Endodontics Part 2, we will look at the different tips available on the market in relation to the site application and the clinical purpose.


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