Piezosurgery – A novel tool in modern dentistry

INTRODUCTION

Over the years, dental treatment has undergone tremendous advancements evolving into a world of painless dentistry. Traditional tools including both manual and motor-driven instruments used in osseous surgeries generated a large amount of heat that could damage the adjacent tissues or delay wound healing and hence required copious external irrigation. Moreover, these instruments exerted considerable amount of pressure and hence made treatment of fractured or brittle bones risky.^[1,2] Furthermore, the noise and macrovibrations produced by the traditional motor-driven instruments resulted in fear and stress in patients during bone cutting.^[3]

To overcome these limitations, a novel technique termed piezoelectric surgery or piezosurgery (PS) was developed which uses ultrasonic vibrations with an average frequency of 25–29 KHz, favoring selective cutting of hard tissues sparing the adjacent soft tissues.^[4] Low surgical trauma, exceptional precision, and fast healing response associated with PS lead to treatment effectiveness and improved post-operative recovery and healing.^[5]

PS is performed using piezoelectric effect, first introduced by French physicist Jacques and Pierre Curie in 1880.^[6] Piezosurgical device was first invented by Dr. Tomaso Vercelloti in 1997 in collaboration with Mectron Spa^[7] which later devised the 2^nd generation and (2004) 3^rd generation PS devices (2009).^[1]

MECHANISM OF ACTION

“Piezo” is derived from the Greek word “Piezen” meaning pressure. PS works on the principle of “pressure electrification,” according to which piezoelectric effect is detected in certain crystals such as quartz, Rochelle salt, and ceramics. Piezoelectric ultrasonic frequency is developed by passing an electric current from generator over piezoceramic rings, with resultant deformation. The resultant vibration in the transducer creates the ultrasound output which is conducted to the handpiece tip, also called an insert, which exhibits longitudinal movement enabling bone cutting by microscopic shattering of bone.^[8]

Frequency range of the micromovements is between 25 and 29 KHz, depending on the insert, with amplitude of 60– 210 μm which selectively cuts mineralized tissue. Soft tissues including the vital structures such as nerves and vessels would be incised by a frequency of above 50 KHz.^[9] The power of the device is adjusted at 5 W. A coolant is driven through the oscillating tip while in function, thereby producing a cavitation effect.^[1]

This involves vaporization of the coolant, bubble formation followed by implosion of the coolant molecule into tiny fractions of its original size. The water bubbles which explode under high pressure cause erosion and cleaning of the surgical field, thereby improving visibility and the operating skills. The cavitation effects also attribute to the antimicrobial property resulting from the fragmentation of bacterial cell wall, favoring predictable results with minimal morbidity in osseous surgery.^[10]

THE EQUIPMENT AND ITS PARTS

The PS device [Figure 1] consists of a handpiece which is controlled by a foot switch.^[1] Both receive power supply from a main unit which has holders for the handpiece and the irrigating coolant.^[8] The vibrating frequency and the cutting efficiency of the PS tip as well as the speed of irrigation are adjusted using the foot switch with the settings of the key pad in the control panel.^[11]

Close

Figure 1:

Piezosurgical unit.

Export to PPT

The irrigant refrigerated at 4°C is contained in a bottle hanging from a rod. A peristaltic pump containing the irrigating saline discharges it through a sterile tube at an adjustable rate of 0–60 ml/min to avoid overheating during bone cutting and to clear the debris from the cutting area, thereby ensuring precise cutting.^[10] A continuous irrigant flow is maintained throughout the surgery by internal safety control.^[1]

APPLICATIONS IN DENTISTRY

PS VERSUS CONVENTIONAL SURGERY

BIOLOGICAL EFFECTS OF PIEZOSURGERY

Temperature alterations associated with osseous surgeries often have an impact on the structure of the bone as well as the vitality of the bone cells.^[3] Very precise customized cutting of PS done along with minimal bleeding enhances wound healing. The continuous flow of the cool irrigant decreases the ill effects of heat generation during bone cutting thereby reducing the chances of osseous necrosis.^[16]

PS inserts do not generate pressure and vibrations in the bone when it is being prepared when compared to rotary instruments.^[15] Piezosurgical osteotomy preserved the original bone structure with minimal surface superficial roughness when compared to conventional osteotomy techniques.^[17]

Vercellotti et al. stated that the PS insert vibrated within a width of 60–200 μm at a modulated ultrasonic frequency avoiding a rise in temperature, thereby eliminating bone damage resulting in favorable osseous healing.^[18]

Expression of heat shock protein (HSP 70), a potential biomarker of stress, is relatively lower at mRNA level and at protein level in the alveolar bone following PS compared to conventional bone cutting techniques. This indicates low stress to patients helping in cell repair after PS procedure.^[19]

A few histomorphometrical, immunohistochemical, and molecular analysis comparing piezosurgery with conventional drills and oscillating saws^[18] observed similar rate of bone healing but slightly more bone formation following piezosurgery.^[16] Bone harvested using PS device was found to contain more osteoblast like cells.^[20] Stubinger et al. observed better periosteal microcirculation while using PS device for subperiosteal preparation which could be an incentive for enhanced bone metabolism.^[16]

PS device could delicately shape and thin a layer of cortical block that could support reconstructed alveolar process.^[21] Bone blocks removed by PS contained a significant number of surviving osteoblasts and osteocytes when compared to rotary instruments.^[15]

The primary stability of the implants placed using PS was found to be similar to that of conventional implant placement techniques. Moreover, osteotomy performed using PS preserves the bone microstructure, thereby facilitating bone healing resulting in optimal osseointegration which decides implant success.^[15] Piezoelectric osteotomy done in distraction osteogenesis procedure before placing implants was simple with lesser intraoperative complications when compared with conventional osteotomy procedures.^[22]

In sinus lift procedures, PS device cuts the bony window with simplicity and precision avoiding membrane perforation even in anatomically complex situations because of the shape of the bone scalpels which work with ultrasonic modulating vibrations.^[23,24]

Osseous resective surgery performed using PS device resulted in lower post-surgical inflammatory response and minimal patient morbidity with clinical results similar to rotary instrumentation 12 months postoperatively.^[25] PS device employed in crown-lengthening surgeries achieved effective bone reduction conserving the integrity of the root surface.^[3] Piezosurgery, therefore, plays a promising role in osseous surgery.

CONCLUSION

Piezosurgery is an elegant and safe bone cutting mechanism which applies ultrasonic microvibrations achieving highly predictable results. The major benefits of piezosurgery include precise bone cutting, soft-tissue protection, minimal blood loss, clear surgical field, minimal sound and vibration, and good patient comfort with optimal safety to the tooth structures. Piezosurgery, in spite of the longer intraoperative time and the need to acquire professional skill and training, has transformed highly demanding procedures into easy and highly feasible procedures even in inaccessible regions. Post-operative recovery and wound healing following PS are favorable achieving optimal bone regeneration. With the emerging technological advances, piezosurgical device will be a promising modality with numerous applications in the various disciplines of dentistry.