Ultrasound has been used for many years in periodontics to remove tartar, debride root surfaces, and to degranulate periodontal defects. In the last decade a novel family of ultrasonic-powered devices has been developed that is revolutionizing maxillofacial bone surgery.
A new surgical technique, known as piezosurgery, was invented by Vercellotti and developed by Mectron Medical Technology. The piezosurgery device (Figure 80-1) consists of a piezoelectric ultrasonic transducer powered by an ultrasonic generator, capable of driving a range of specially designed cutting inserts (Figure 80-2).17,22 Box 80-1 describes the main cutting properties of piezosurgery by Mectron, and Box 80-2 describes piezosurgery inserts. Piezoelectric bone surgery techniques have been developed for clinical applications in dentistry and are becoming state of the art for a variety of procedures.18–20,22,28,29 Recently, Piezosurgery Medical expanded development of clinical applications to other fields of medicine. The extraordinary cutting properties of piezoelectric bone surgery have been introduced and applied in maxillofacial surgery, cranial and spinal neurosurgery, and hand-foot surgery.3–13
The most compelling characteristics of piezoelectric bone surgery are low surgical trauma, exceptional control during surgery, and a fast healing response of tissues. Clinical studies demonstrate that the specificity of operation and the techniques employed with piezoelectric bone surgery make it possible to advantageously exploit differences in hard- and soft-tissue anatomy.3,23,25,26 This not only increases treatment effectiveness but it also improves postoperative recovery and healing. Experimental studies on animals have shown faster tissue healing when compared to traditional cutting instruments.3
Ideally, surgical trauma should be minimized to obtain the optimal healing, which depends on gentle management of soft and hard tissues. Surgery, by definition, alters normal physiology by interrupting the vascular supply of tissues. The degree of surgical invasiveness is extremely important for the quality of tissue healing and may effect whether wounds heal by repair or regeneration. Indeed, when surgical trauma is kept to a minimum it generates enough stimulation to favor healing mechanisms that lead to regeneration. On the other hand, surgical techniques that are more traumatic often lead to greater inflammatory responses with slow healing that may lead to repair and scarring rather than regeneration. For this reason, it is desirable to choose the least-traumatic surgical instruments and techniques for any surgical procedure. Piezoelectric bone surgery was conceived and developed precisely to overcome the limits of traditional bone-cutting instruments and to achieve the most effective treatment with the least morbidity.
From a mechanical standpoint, the effect of burs or twist drills on bone is characterized by lamellar fracturing in areas adjacent to the cut surface and the deposition of large bone fragments and debris in the endosteal spaces. This finding is thought to be, at least in part, responsible for the inflammatory process that takes place in the immediate postsurgical wound healing and for the delay of osteogenesis observed in these wounds. On the other hand, the micromechanical cutting action of piezoelectric bone surgery results in micronization of the cut bone and does not cause lamellar fracturing in adjacent bone, which may favor exposure and release of bone morphogenetic proteins and be responsible for the early onset of osteogenesis at these sites (see below). Furthermore, there may be a diminished inflammatory response since there is little or no need to remove damaged bone and surgical debris as compared to conventional rotary drilled sites.
Piezosurgery cuts mineralized tissues with microprecision. The cut is made by mechanical microvibrations at a linear range of approximately 80 µm and a frequency of 30,000 times a second. A sound wave is overmodulated on this base frequency, which generates a hammering action with very little heat because the mechanical energy necessary to produce the microvibrations is very low. This action, along with the water spray, facilitates removal of bone debris.
Piezoelectric osteotomies are easy to create, but it is important to recognize that the technique and instrument handling are different than the technique using a traditional handpiece with rotary instruments. The piezosurgery insert is applied to the bone with a relatively light stroke similar to the smooth precision used to draw a picture. Heavy pressure or force is not required. Indeed, the pressure applied by the surgeon to the piezosurgery handpiece is much lower than the pressure typically applied to a rotary or oscillating type handpiece, which uses mechanical macrovibrations for cutting. This characteristic provides maximum control during surgery and makes this technique unique especially in areas with delicate anatomy.
Piezosurgery ultrasonic microvibrations are low frequency and selective for cutting mineralized tissue only. These microvibrations are physically unable to cut soft tissue. Clearly, the most significant demonstrated benefit of piezosurgery selective cutting is the ability to preserve the integrity of soft tissues, such as the alveolar nerve, the infraorbital nerve, the maxillary sinus membrane, and the dura mater, while effectively cutting the mineralized tissue (bone) in close proximity to these tissues.
Piezosurgery creates a surgical field that is blood free during cutting because of its cavitation effect. Cavitation is a physical phenomenon that, from a clinical standpoint, happens with the nebulization of the saline solution. The slight hydropneumatic pressure applied by piezosurgery temporarily stops bleeding from both hard and soft tissues. It is important for the liquid pump to be flowing properly and for the cutting action to be intermittent to maintain optimal surface microcirculation, especially for long surgical procedures. Tissue perfusion resumes shortly after cutting (and cavitation action) is stopped.
Clinical studies comparing use of piezoelectric bone surgery with traditional rotary instruments for third molar extractions14 and periodontal surgery25 have reported better recovery and fewer postoperative symptoms in those treated with piezosurgery. Postoperative healing after piezoelectric bone surgery is characterized by minimal swelling and little bleeding and postoperative morbidity is lower compared to traditional techniques.24 Gingival tissue is typically light in color when compared to the appearance of autogenous gel of platelet-rich plasma.
There are many important clinical applications of piezoelectric bone surgery in dentistry. In fact, nearly all techniques previously performed with burs, twist drills, chisels, or oscillating saws have the potential to be performed with piezosurgery. For 10 consecutive years the author (TV) has used piezosurgery on a daily basis for oral, periodontal, and implant surgical procedures, enabling him to develop techniques and protocols for each. Readers are referred to online materials and other publications for detailed descriptions and step-by-step instructions on these piezosurgery protocols. A brief overview of basic clinical applications using piezoelectric surgery is described here.
The use of piezosurgery in periodontal surgery simplifies and improves handling of soft and hard tissues.30 In resective periodontal surgery, for example, after raising the primary flap with a traditional technique, using a scaler-shaped insert (PS2) (Figure 80-3, A) or an insert in the shape of a rounded scalpel (OP3) makes it easier to detach the secondary flap and remove inflammatory granulation tissue. This phase has little bleeding as the result of the cavitation of the saline solution (coolant). With the right inserts and power mode, the ultrasound device facilitates effective scaling, debridement, and root planing (Figure 80-3, B and C). In particular, debridement with a special diamond-coated insert enables thorough cleaning even for interproximal bone defects (Figure 80-3, D). The mechanical action of ultrasonic microvibrations, together with cavitation of the irrigation fluid (pH neutral; isotonic saline solution) eliminates bacteria, toxins, dead cells, and debris, which creates a clean physiology for healing. Healing is improved by applying ultrasound to produce micropits at the base of the defect to activate cellular response of healing mechanisms. Autogenous bone-grafting material consists of bone chips that are collected during the piezoelectric osteoplasty operation for recontouring bone irregularities (Figure 80-3, E). The result is that this technology reduces the invasiveness of traditional surgery by making surgery faster and by ensuring thorough cleaning of the periodontium. It also favors tissue healing by using bone removed in the osteoplasty procedure to graft osseous defects.
Piezosurgery in periodontal surgery redefines the guidelines that mark the border between resective treatment and regenerative treatment. Indeed, the choice between a resective technique and a regenerative technique generally depends on the depth of the bone defect, whether it is higher or lower than 3.5 mm.
The ability to work on the bone defect with magnifying systems makes it possible to exploit the benefits of piezosurgery microprecision in preparing the recipient site and stabilizing micrografts (Figure 80-3, F to H).
Clinical crown lengthening is the most common periodontal surgical (ostectomy) operation performed in otherwise healthy periodontal conditions. The indication for this procedure is usually associated with a need or desire to expose more tooth structure because of short clinical crowns and/or loss of clinical tooth structure. In general, the goal is to reposition the periodontal bone and soft tissues to a more apical position with appropriate biologic dimensions and minimal periodontal inflammation.
The clinical crown lengthening technique entails performing a periradicular ostectomy of a few millimeters, which allows repositioning of the periodontal flap in a more apical position. The positive result obtained is that the health of the treated part is preserved even though the normal gingival morphology is altered. Clinical application must include esthetic assessment, as well as an assessment on the position and health of the adjacent periodontium.
The traditional surgical technique entails raising a full-thickness flap, performing the ostectomy with manual instruments, osteoplasty with a bur for crest bone architecture recontouring, periradicular bone removal, root planing, and, finally, replacing the flap in an apical position.
The ostectomy is simple to perform using piezosurgery in direct contact with the root surface because control of the instrument during surgery is precise, even in very difficult proximity cases (piezosurgery OP3 insert). The root planing phase can be performed very effectively using blunt ultrasonic inserts (piezosurgery PP1 insert).
Saline solution cavitation reduces bleeding during surgery and facilitates debridement of the surgical area. This effect is likely responsible for the excellent soft-tissue healing result, which is always />