Piezosurgery: Basics and Possibilities

Abstract

Useful in a variety of oral surgery procedures, piezosurgery has therapeutic features that include a micrometric cut (precise and secure action to limit tissue damage, especially to osteocytes), a selective cut (affecting mineralized tissues, but not surrounding soft tissues), and a clear surgical site (the result of the cavitation effect created by an irrigation/cooling solution and oscillating tip). Because the instrument's tip vibrates at different ultrasonic frequencies, since hard and soft tissues are cut at different frequencies, a “selective cut” enables the clinician to cut hard tissues while sparing fine anatomical structures (e.g., schneiderian membrane, nerve tissue). An oscillating tip drives the cooling-irrigation fluid, making it possible to obtain effective cooling as well as higher visibility (via cavitation effect) compared to conventional surgical instruments (rotating burs and oscillating saws), even in deep spaces. As a result, implantology surgical techniques such as bone harvesting (chips and blocks), crestal bone splitting, and sinus floor elevation can be performed with greater ease and safety.

A great number of studies demonstrate the high success rate of dental implants for both function and esthetics.^1–4 However, osseointegrated implants are only as successful as the final restorations they ultimately support. So optimal positioning of the implant is critical. This focus on the final restoration gives rise to the terms “restoration-driven implant placement” and “reverse planning,” terms that are synonymous with the goal of positioning the implant not necessarily where the most bone is but in the position ideal for prosthetic finalization.^5–9 This goal often means planning for osteoplasty in the oral region; in other words, bone grafting and bone regeneration to augment atrophic areas.

The modern science of implantology affords a variety of techniques for bone augmentation.^10–12 To avoid micromovement and to exclude undesirable cells, a variety of barrier membranes can be used.^13–17 Alternative bone grafting techniques include bone block transplants from the chin, lateral mandible, and iliac crest.^18–25 Growth factors can be added in order to accelerate angiogenesis and healing, and to stabilize the graft.^26–31 To avoid autologous bone transplants in bone with good density, the clinician may choose to perform alveolar ridge splitting.^32–39 And, to treat vertical bone loss in the posterior maxilla and/or the pneumatization of the sinus after tooth loss, sinus floor elevation is usually the most effective therapy: through a crestal or lateral access, the schneiderian membrane is elevated without perforation, and the space between bone and membrane filled by the new graft.^40–43

Piezo-electrical surgery can be used to perform many of the techniques described above, with distinct advantages over conventional surgical methods.

Materials and Methods

The Piezosurgery® device (Mectron, Italy), invented by Dr. Tomaso Vercellotti, uses a modulated functional working frequency of 25−30 kHz. At this frequency, only bone can be cut. In order to cut soft tissue, a frequency of 50 kHz is needed. When used correctly, the device virtually cannot cut the schneiderian membrane, nerves, or periosteum, so the device is recommended in cases where avoiding contact with such structures is considered vital. Nonetheless, because the mechanical energy of the device is not used to completely cut mineral structures, the energy can be passed to the soft tissue as heat. As well, mechanical damage to the soft tissue is possible (e.g., injuring the schneiderian membrane due to high pressure). However, cooling is ensured via the device's pump system. For effective cooling, the solution is refrigerated at 4°C. The flow rate and the intensity of the oscillation can be regulated.

The handpiece can be fitted with different tips for osteoplasty, osteotomy, separating soft tissue from bone, and cutting bone. For example, osteoplasty for the collection of bone particles can be executed through the use of handpiece insert osteoplasty No. 1 or insert osteoplasty No. 3. Combining 2 settings creates the working frequency of the instrument tips: 1 modulated horizontal setting of 60−200 μm and 1 vertical modulated setting of 20−60 μm. When compared to oscillating micro-saws, the movement of the Piezosurgery® scalpel tip is very small. The cutting is more precise and causes less discomfort for the patient.

When using conventional micro-saws, the clinician must apply a certain degree of pressure. By contrast, the Piezosurgery® device needs only a very small amount of pressure, which enables a highly precise cut. Too much pressure limits the movement of the tip, and heat is generated. At maximum pressure, when the tip of the instrument does not move and only heat is generated, a tone warns that bone damage is imminent. The translation speed (the speed from the tip of the instrument in contact with the bone) and the form of the tip material (diamond headed, sharp, with irregularities) have an effect on the cutting power. The operator can intuitively learn how fast a certain tip can be moved. The power of the device is 5 W (ultrasonic scaler 2 W). More power increases the cutting ability, but the device requires thicker tips, which cause thicker and more imprecise cuts. The 5-W power is the ideal compromise between speed and precision.

The bone harvest site remains almost free of blood during the cutting procedure. The reason lies in the cavitation effect created by the cooling fluid distribution and by the kind of vibration the instrument generates. By contrast, in a micro-saw, blood is moved in and out of the cutting area. However, with the piezo-instrument and its high frequency vibration in all directions, blood is essentially washed away. The consequence is an ideal visibility of the operating field. Thus, when used properly, Piezosurgery® causes less damage to the bone at the structural and cellular level compared with other techniques.⁴⁴ No other system on the market fulfills these criteria.

Oral Surgery Techniques

Specific oral surgery indications documented for using the Piezosurgery® device include dental extraction, osteogenic distraction, ridge expansion (crestal splitting), endodontic surgery, bone harvesting (chips and blocks), maxillary sinus lift, third molar extraction, alveolar nerve decompression, and cyst removal.⁴⁵ Of particular interest to the implantologist are the harvesting techniques, ridge splitting, and sinus lift procedures.

Bone Chips

Bone chips have the role of space making and guides for bone regeneration (through osteoconduction), and also for support of growth factors at the recipient site in order to speed up bone healing.^46–48 The chips are technically not transplants because the osteocytes, lacking a blood supply, do not survive. During the healing period, the chips are replaced by bone via remodeling. Autogenous bone chips are easy to harvest from the drill surface, but this bone powder is resorbed too fast, and cannot fulfill its role as a space maker and guide. Particles with sufficient volume are needed. Clinically, particles of 500 μm show best results. This particle size can be obtained with bone mills.⁴⁹ However, bone mills have the disadvantage of a high price and loss of bone material.

The Piezosurgery® device is well adapted for bone chip harvesting.⁵⁰ The osteoplasty No. 1 to osteoplasty No. 3 tips can be used with gentle scratching movements along the surface of the bone in order to obtain sufficient bone chip volume (Fig. 1). The bone is accumulated in the front of the instrument and then removed. A complication-free region for bone chip harvesting is the linea obliqua in the mandible. The incision is similar to that used for the extraction of an eighth crestal incision retromolar and a mesial paramarginal incision. It is possible to harvest also in the vicinity of the operating area, eliminating the need for a second, surgical site.

Fig. 1.: The Tipp osteoplasty No. 3 is designed to collect autogenous bone chips ideal for periodontal regeneration.Fig. 2. The delicate access for the linea obliqua approach.Fig. 3. Alveolar ridge splitting procedure can be combined with sinus floor elevation.

In periodontology, there are certain indications for autogenous bone transplants, considered the gold standard. In large flat defects around teeth, autologous bone provides better chances for healing. The success probability of regenerative measures in certain defects is low because of the anatomical conditions. Treating the defect with bone chips has advantages. The bone can be harvested with the osteoplasty No. 3 instrument from the linea obliqua and inserted in the defect.

Bone Blocks

The success of bone healing can be limited when particulate grafting material is used in nonstable spaces. In bone-surrounded spaces, particulate material works well, especially when membranes are used.^51–53 However, the particulate materials show their limits in horizontal or vertical augmentation procedures. In these cases, bone blocks give the best results. Classic donor areas are the chin, linea obliqua, and crista iliaca.

In the linea obliqua procedure, a crestal incision in the retromolar area extends intrasulcularly or paramarginally to the anterior. A releasing incision is made in the premolar region for bone exposure. The osteotomy is made via Lindemann drills and rotating discs for the horizontal incision. This horizontal osteotomy needs a large uncovering in order to provide the clinician good access and to protect the soft tissue.

Piezosurgery® makes the linea obliqua approach easier (Fig. 2). The low amplitude of the instrument tip, the optimal cooling effect, and the selective cut ensure that no injury occurs to the neighboring structures. A small access that allows undermining preparation is sufficient, and no direct visibility of the deep horizontal cut and no preparation of the N. mentalis are necessary.

Bone Splitting

The previous techniques often have the disadvantage of requiring a second surgical (donor) site, usually requiring membranes. Additionally, implants usually cannot be simultaneously inserted after particulate or bone block grafts are used, so a second surgery follows. While particulated materials can be used combined with implant insertion, micromovement of the graft material can compromise the final result.

In cases with sufficient bone height but insufficient width, bone splitting may be indicated.³⁸ No membranes are needed, and many complications are avoided (e.g., no transplants or biomaterials are used). In order to avoid bone resorption, a split thickness flap is elevated. The bone-splitting procedure respectively lingual separates the buccal from the palatal plate. The resulting space between the 2 plates has ideal regenerative and implant-integrating conditions. Augmentation materials are surrounded by bone, they have 2 directional blood vessel supplies and cell migration. There is no micromovement. These are the ideal conditions for low-risk healing. The risk of bone splitting, however, is pressure trauma, especially in D1 bone.⁵⁴ Fractures represent no problem because the periosteum is not elevated. This greenstick fracture normally heals with no complications.

Bone splitting has been used primarily in the maxilla, where bone elasticity is greater. Piezosurgery® is used in dense mineralized bone because the vertical dimension of the bone is maintained while the width permits no implant insertion. In order to perform the case in 1 stage, bone splitting is performed.⁵⁵ Because the alveolar crest will be larger after splitting, a split thickness flap is needed to cover the bone. A tension-free suture is possible in such cases. The periosteum, with its blood vessels, remains attached to the bone. An incision is made with a saw form tip (osteoplasty No. 5). Because the bone is elastic, no releasing incision on the buccal side is needed. The bone can be extended with osteotomes, and implants can be inserted in a combined drill-split technique. The remaining bone chips from the drills are sufficient for filling the space between the 2 lamellae. A tension-free suture can be performed without the use of membranes (Figs. 3–5).

Fig. 4.: The expanded ridge.Fig. 5. A 6-month result.Fig. 6. The preparation of the lateral window is done with a round diamond tip.Fig. 7. The initial dissection of the membrane is done with tip EL 1. The hydropneumatic pressure of the cooling medium helps to dissect the membrane.

Sinus Floor Elevation

The sinus floor elevation is now a routine procedure for the treatment of vertical deficiencies in the posterior maxilla.⁴² Lateral access is most common. The schneiderian membrane is prepared via a modified Caldwell-Luc technique. Membrane perforation is a risk with this procedure during the preparation of the window or during the elevation stage. In cases of recent closures of sinus-mouth communications, because of the presence of septae or for other reasons, the possibility of membrane perforation is high. Often, this perforation becomes a rupture that makes closure impossible, even with microsutures or membranes. An intact membrane is a precondition for stabilizing the graft.

Several of the risks associated with sinus lift procedures are reduced with Piezosurgery®.⁵⁶ The instrument's selective cut makes it virtually impossible for the clinician to injure the membrane while preparing the window. In cases of a thin bone wall, the osteoplasty No. 5 tip is indicated, and in cases with thick bone, the osteoplasty No. 1 tip is used for reduction, and only then the osteoplasty No. 5 tip. The remaining bone chips are collected for the graft procedure.

Manual instruments are used for the membrane preparation and can lift the membrane 2 mm around the limits of the window. After this procedure, the Piezosurgery® EL2 and EL3 elevation instruments are used. These instruments perform as conventional sinus instruments, with micro-saw settings and hydropneumatic pressure applied through the cooling saline solution. In certain situations, a handheld instrument is needed (Figs. 6, 7).

Conclusions

Piezosurgery® is a relatively new surgical technique for periodontology and implantology that can be used to complement traditional oral surgical procedures, and, in some cases, replace traditional procedures. The low pressure applied to the instrument enables a precise cut; additionally, the selective cut characteristically protects soft tissues. Nerve transpositioning, sinus floor elevations, distraction osteogenesis, and a number of other sensitive procedures are easier and safer to perform with Piezosurgery®. As a result, even less experienced, though properly trained, surgeons can perform these techniques more effectively with Piezosurgery®.

Disclosure

Dr. Schlee claims to be a lecturer on behalf of Mectron, Italy. All other authors have no affiliation with this company or its products.