Removal of Impacted Third Molars: High Speed Bur or Piezosurgery?

Approximately 20 percent of the general population have impacted teeth, the majority of which are third molars.¹ Therefore, the removal of impacted teeth is one of the most common procedures to be performed in oral surgery practices.² It is also a procedure that instills fear and anxiety in many patients.

Third molar removal can range from simple extractions to overly complex and difficult procedures. As a result, there is a wide variation in the amount of pain, swelling, and trismus that occurs postoperatively and in the development of injuries to the inferior alveolar and lingual nerves.

Clinicians and researchers have continually strived to develop instrumentation to reduce these complications and improve efficiency and ease of use. At one time, third molar removal with a mallet and osteotome was state of the art. Although heat is not generated with the use of this technique, it does require the use of high forces that could lead to damage to the bone and surrounding structures. Moreover, this technique is not easily performed on the awake patient.

The development of conventional rotatory instrumentation represented a major advancement in the removal of third molars, but it was still a slow process. All this changed with the introduction of the high-speed handpiece. However, there are some drawbacks to its use. Excessive high temperatures may be produced during osteotomy that can lead to marginal osteonecrosis and impair regeneration and healing.³ Although copious irrigation directed on the bur is used to limit heat generation, this can be obscured in difficult access areas, by other instruments, adjacent soft tissues, and an increasing depth of the osteotomy.⁴ Also, burs may accidentally cut into surrounding soft tissues during osteotomy resulting in severe damage to muscles, blood vessels and nerves, especially in sites with difficult or limited access.⁵ Depending on the design of the bur and the speed and torque of the rotary handpiece, a certain degree of pressure is required to limit skipping of the bur on the bone surface when performing the osteotomy. This potentially affects the accuracy of the bone cuts, decreases fine touch sensitivity for the surgeon⁶ and increases discomfort for the nervous patient.⁷

Piezosurgery
To overcome the limitations of manual and rotatory osteotomy techniques, a novel surgical technique for the precise and selective cutting of bone without traumatizing the adjacent soft tissues has been introduced. This innovative technique is termed piezosurgery. The term “piezo” originates from the Greek word piezen, which means “to press tight, squeeze”. The instruments used in piezosurgery of bone create microvibrations that are caused by the piezoelectric effect, first described by the French physicists Jacques and Pierre Curie in 1880. This effect involves the principle of ‘Pressure Electrification’, meaning when an electric current is applied across certain materials, the material in question expands and contracts, thus producing ultrasonic vibrations.⁸ Materials used are piezoelectrical crystals such as quartz, Rochelle salt and certain types of ceramic.

When these crystals are subjected to an electrical charge in the surgical unit, they expand and contract alternately to produce ultrasonic waves. These vibrations are amplified and transferred to the insert (tip) of a handpiece which, when applied with slight pressure on the bone, results in a cavitation phenomenon – a mechanical cutting of mineralized tissue.⁷ A frequency of 25-29 kHz is used because the micromovements that are created at this frequency (ranging between 60- 210 um) cut only mineralized tissue. Soft tissues, such as nerves and blood vessels, are cut at frequencies higher than 50 kHz.⁹

Piezoelectric surgical units have a handpiece (Fig. 1) and foot switch that are connected to a main power unit that has holders for the handpiece and irrigation fluids Irrigation is controlled by a peristaltic pump. The foot switch activates the interchangeable handpiece inserts. Inserts of different sizes, shapes, and materials are available.⁷ They can be coated with titanium nitride or diamonds of different grades. Examples include the scalpel, cone compressor, bone harvester, and sharp-tipped saw. (Fig. 2)

Fig. 1

Fig. 2

Advantages and Disadvantages of Piezosurgery
A recent systematic review of the literature and meta-analysis, as well as a trial sequential analysis of the data, compared the results of using piezosurgery or conventional rotatory instruments for the removal of third molars.¹⁰ It was found that pain scores were significantly less in the piezosurgery group on days 1, 3 and 7. Trismus was also significantly less is the piezosurgery group on day 1, but not on day 7. Swelling was not significantly different in the two groups and there were also no significant differences in neurological complications. The reduction in inflammatory complications is not surprising as piezosurgery results in less injury to bone and soft tissue, which ensures a better blood supply leading to decreased inflammation and faster healing. The major difference between the two groups was surgical time, which was significantly longer using piezosurgery.

Otake, et al.¹¹ demonstrated microscopically that piezosurgery provides a smooth bony surface with no damage to soft tissues in comparison to conventional drillings. However, they also reported that it took almost three times longer to perform the cuts using piezosurgery compared to a surgical bur. Rullo et al.¹² corroborated this finding clinically, and found that for complex third molar extractions, the average time was 28% longer using piezosurgery than rotary instruments. Esteves, et al..¹³ evaluated bone healing histologically and histomorphometrically comparing piezosurgery and conventional drilling and found that the piezosurgery samples had slightly increased bone formation at 30 days but demonstrated no differences in bone healing or volume at 60 days. They concluded that bone healing dynamics were comparable using either method. Tsai et al.¹⁴ compared healing of the periodontium on the distal side of the mandibular second molar after third molar removal using the two surgical techniques by assessing attachment levels. They found there was faster wound recovery in the piezosurgery group at 1 month, but healing was not statistically different at 2 months.

In contrast to the use of rotary instruments, piezosurgery devices need only a minimal pressure to achieve a precise cut. The gentle vibration, minimal pressure and minimal noise produced by the device potentially increase patient comfort during the surgical procedures under local anesthesia.¹⁵ Increasing pressure limits the movement of the vibrating tip, decreasing effectiveness and increasing heat production.

When using piezosurgery, the operative field remains almost free of blood during the cutting procedure, greatly improving visibility for the operator. This is due to two effects – microstreaming and the cavitation effect. Microstreaming is the continuous whirling movement of fluids created by the vibrating tip that favours debris removal. The cavitation effect is caused by the implosion of gas bubbles inside terminal blood vessels producing a hemostatic effect.¹⁰

A disadvantage of piezosurgery is that high level surgical control is needed compared to conventional methods, requiring a change in technique which has a high learning curve.¹⁶ Also, the piezosurgery unit is expensive and this may be a prohibitive factor limiting widespread use.¹⁷

Conclusions
In third molar removal, piezosurgery appears to be more efficient than conventual methods in improving intraoperative visibility and patient comfort. It also may be more effective in limiting postoperative inflammatory complications and may initially result in more rapid healing. However, the high cost of the equipment is of economic concern for the surgeon, as well as the excessive surgical times. There is also a steep learning curve in its use. These disadvantages may not justify its routine use in the removal of impacted third molars.

Oral Health welcomes this original article.

Indications Bone grafting, (2) Sinus lift, (3) orthodontic surgery, (4) ankylosed teeth, (5)removal of implant or implant site preparation.

Contraindications No absolute contraindication except medical caution advised such as cardiopathy, uncontrolled diabetes, patient receiving radiotherapy, patients with pacemakers and patients with metal/ceramic crowns.

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About the Author

Robert A. Green, Oral and Maxillofacial Surgeon. Stoney Creek, Ontario. Email: oralmaxsurg@gmail.com

Daniel M. Laskin, Professor and Chairman Emeritus, Department of Oral and Maxillofacial Surgery. Virginia Commonwealth University School of Dentistry, Richmond, Virginia. Email: dmlaskin@vcu.edu