The introduction of motorized cutting instruments has been the most important technologic advance in oral surgery. These instruments both increase the cutting speed and reduce the cutting effort exerted during osteotomy, while taking into account the surgical parameters.
In odontostomatology, the continuous circular movement is primarily used with three types of instruments: (1) drills for piercing, (2) trephines and saws for making larger holes (eg, bone harvesting), and (3) stainless steel and diamond-coated burs used with a micromotor, a handpiece, and constant irrigation with physiologic saline solution. All these rotary instruments are used at a speed of 40,000 to 50,000 rpm, with temperatures not exceeding 57°C. At 57°C, the bone proteins coagulate, resulting in irreversible tissue damage.
Because improvements in cutting instruments have aided the development of osteotomy techniques, the study of the osteotomy itself and the action of the instrument on the material remains of fundamental importance. These considerations also lead to the definition of optimal geometric characteristics of the cutting instruments, thereby minimizing the cutting effort as well as reducing the temperature. The geometry of a saw’s teeth determines its mode of action on a material (Giraud et al, 1991).
The practice of osteotomy has three major objectives:
- Excision osteotomy: Ablation of a piece of bone
- Reparation osteotomy: Anatomic correction
- Access osteotomy: Sectioning bone that prevents access to the main surgical site, which is then placed back in its original anatomic position after surgery
In summary, osteotomes can resect, trephine, and smooth bone, thereby bringing about osteotomies, osteoplasties, and osteosynthesis.
Characteristic requirements of an osteotome
- Rapid cutting to minimize the duration of surgery
- Reduced effort in cutting to give the surgeon total control of the instrument
- No bone loss or dispersion in the surgical field
- No bone tissue destruction caused by burning
- No delayed or restrained bone consolidation
- No lesions in surrounding tissues
- No undesirable biologic effects
- Ergonomic design
- Easy to sterilize
- Capable of performing osteotomies in several planes
The instruments must be autoclavable, and the technical maintenance must be simple. Deterioration and technical malfunctions of the devices must be controllable by the user. Finally, the instruments must ensure their proper cooling through irrigation in the sterile conditions necessitated by surgery.
Laser instruments are unsuitable for cutting bone because of the basic interaction of laser beams with biologic material. In all cases, laser surgery exceeds the threshold of thermal necrosis; thus, the healing and consolidation process is delayed. Laser surgery is mainly indicated for excision and soft tissue surgery and for dentin surface sterilization.
High-pressure water jet
This technique has not been sufficiently tested to determine whether it is suitable for surgical applications.
This technique, called ultrasonic-assisted osteotomy, increases the capacity of a sharp cutting tool. It superimposes the ultrasonic movement of the tip with the manual cutting movement.
The term piezosurgery applies to devices employing the piezoelectric effect to generate ultrasounds. This technique is relatively new and in continued development due to advances made with the piezosurgery machine developed by Vercelloti and the Mectron Company (Vercelloti et al 2001). Earlier studies on the same topic were published by Horton et al (1981), who spoke of ultrasonic instrumentation and by Sun et al (1997) who introduced the use of ultrasonic devices and also spoke of ultrasonic surgical instruments. Currently, we talk about ultrasonic scalpels, powerful ultrasonic devices (Michel et al 2007), and ultrasonic-assisted osteotomes. In this book, we use the term most commonly accepted in the literature: piezosurgery.
Catuna (1953) was the first to describe the cutting effects of ultrasound devices on hard tissues.
Volkov and Shepeleva in 1974 used ultrasonic devices in orthopedic bone surgery, which provided them with clinical experience that helped to simplify orthopedic surgery. However, the technique of sectioning and preparing hard tissues was first studied by Horton et al (1981) in the 1970s and 1980s in the field of oral surgery. It was further developed by maxillofacial surgeons to solve difficulties in their own practice. Stübinger et al (2005) insisted that piezoelectric instruments have known a new impetus since the 1990s. Torella et al (1998) and Vercellotti et al (2001) have gone so far as to state that the method has been perfected and adapted to practical clinical needs.
Ultrasonic devices offer five main advantages: selective cutting action, precision and cutting safety, visibility, accessibility, and better postoperative results.
Selective cutting action
Ultrasonic-assisted osteotomes are efficient at cutting mineralized tissues but inefficient at cutting soft tissues. The instrument should have a frequency of 50 kHz to cut hard tissues. Nevertheless, no soft tissue should be found between the tip and the hard tissue because it reduces the cutting effect on the mineralized tissue. Consequently, any useless contact with the soft tissues should be avoided.
There is great interest in the use of this technique during surgeries performed close to sensitive anatomic structures, such as vascular-nervous bundles, that must be protected at all costs.
It should be noted that the cutting action is less efficient at cutting Type IV bone (Lekholm and Zarb 1985) than at cutting other types of bone.
Precision and cutting safety
The microvibrations of the microtip make a precise and controlled submillimetric cut of the bone tissue. Unlike techniques that use a bur or saw, the ultrasonic-assisted osteotome generates no macrovibrations and macromovements that could affect the surgeon’s hand. In contrast, when using a bur or saw, a clinician has to resist the movements induced by the rotational torque of the instrument. As a result, a supplementary effort is made to counteract these movements, which reduces the surgeon’s sensory perception, particularly when structures of varying degrees of mineralization are encountered (Giraud et al 1991).
The microvibrations modulated by ultrasounds create an osteotomy without friction and macrovibrations. In addition, the width of the cut is much smaller than that obtained with rotary instruments (Fig 3-1). This width also depends on the size of the tip used.
Because ultrasonic-assisted osteotomes require less cutting effort, they make complex surgeries easier.