CHAPTER 6 Preparations for Implant Surgery
Most of the chapters in this book begin with warnings or caveats. This is an instructional chapter; therefore the only warning offered is that the readers, even if they do not plan to perform implant surgery itself, should acquire an understanding of the basic principles of surgery before attempting to plan or place implants. Although implant surgery is less demanding and less complex than many other kinds of oral surgery presented in this chapter, the operative path can be filled with complications. A knowledge of management is required, therefore, before the practitioner can begin the practical endeavors in implantology. For those who do intend to perform the surgery, a gentle reminder is offered to check and replenish instruments and disposable supplies before any procedure is started. Although some of the items listed in the armamentarium may seem arcane or may appear unlikely to be required, their presence prepares the surgeon for virtually any unexpected occurrence (Fig. 6-1). Also, this chapter should be read slowly, at a time of leisure, so that the practitioner can learn its contents completely. Readers must have a clear knowledge of their skill level, so that they do not find themselves in a situation in which significant corrective procedures may be required.
FIGURE 6-1. The instrument tray serves the surgeon best if mounted on a Mayo stand, which can slide beneath the chair so that delivery can be made over the patient’s chest. In addition to standard operating instruments, fiberoptic retractors, bone filters on the suction apparatus, electrosurgical equipment, and a selection of fine-toothed forceps can make the surgeon’s efforts more comfortable.
The bulk of implant surgery procedures are performed in the office operatory. The practitioner should try to assemble the equipment required for all planned procedures in this area or room, because this provides maximum convenience for the surgeon and staff and the greatest comfort for the patient. A commodious, complete operatory helps make the treatment of patients more enjoyable. Some basic concepts can be followed in the design of an implant operatory (Fig. 6-2).
FIGURE 6-2. When possible, the operatory should be dedicated to implantology. Chair controls should be foot operated, and light handles should be sterilizable. Ventilation must be excellent, and duplicate rotary instrumentation should be available. Ample countertop and storage space is mandatory, and an abundance of electrical outlets and quick-release fittings for gas, air, water, vacuum suction, oxygen, and nitrous oxide provide convenience. Monitoring and resuscitation equipment, ceiling-mounted intravenous hooks, and anesthesia arm boards and accouterments are helpful.
Adequate space must be available for the surgeon and two additional staff members, an operating chair, cabinetry, and sedation, monitoring, and resuscitative equipment. The chair should have foot controls to raise, lower, and recline it so that hands are not required to change its position during surgery. High- and low-power suction facilities must be available, as well as an arm board if sedation is planned. Positive-pressure oxygen and nitrous oxide are necessary adjuncts, and nitrogen or compressed air is required for many drilling systems. High- and low-speed handpieces are mandatory, as is high-torque, low-speed implant drilling equipment.
Adequate lighting for surgery and appropriate side lighting for supportive procedures (e.g., mixing) should be an integral part of the design for an implant center. Another important feature is a well-placed view box or computer monitor where radiographs can be seen easily during surgery. A radiographic unit should be available so that intraoperative films can be taken without moving the patient.
A bracket table or Mayo stand large enough for all needed instruments must be a part of the facility. Adequate countertop and shelving areas are essential to accommodate the requisite implant equipment (e.g., console, motors, handpieces, irrigation bottles) and devices for monitoring vital signs (e.g., GE Dinamap, Criticare, noninvasive blood pressure, pulse rate, three-lead electrocardiograph, pulse oximeter). Standby instruments for implant surgery must be located conveniently and within clear visual range, and an emergency tray or crash cart should be available.
Other valuable features include foot controls or motion activation for the sink, a plentiful supply of electrical outlets (e.g., electrical strips) above the counter, storage space for stocking implants and prosthetic parts, a fiberoptic headlight, and adequate ventilation. All items and features that make for efficient, smooth, and safe treatment should be included in the plans for an implant operatory.
Perhaps the most misunderstood (and most necessary) of all implant equipment are the surgical delivery systems. Many terms, such as consoles, motors, drills, contra-angles, and handpieces, are commonly misinterpreted as synonyms for delivery systems. These devices actually are integral components of the equipment that makes up an entire surgical delivery system. The more knowledge practitioners acquire about these components, the less time and money they will spend purchasing them, and the better chance they will have that the acquired equipment will satisfy their needs.
No single component is greater than the whole, and a better understanding on the part of the practitioner can make a difference during surgery, resulting in ease and efficacy or breakdown and failure. Despite the best maintenance, any component or system can fail. Every office, therefore, should have a backup unit.
Basically, surgical delivery systems are categorized into one of two classes, depending on the power supply. Most dentists use compressed air or nitrogen gas as the energy source for their regular high-and low-speed handpieces. Most surgical delivery systems for root form implants, however, are powered by electricity.
Until 1985, air- or nitrogen-driven systems were used to perform most root form and blade implant surgery. However, as root form implant systems became universally accepted, electrical surgical modalities, both rotary and piezosurgery, were introduced. Root form implant surgery requires high torque at low speeds, and this created a major problem with air- and nitrogen-powered systems: to receive more power, or torque, air- and nitrogen-powered handpieces require commensurately more speed. Electrical systems introduced higher torque at lower speeds.
An electrical surgical system has four basic components: a console, a motor, a handpiece, and burs or drill bits (or piezosurgical insert tips). In-depth examination of each component and its relationship to the others can help the practitioner understand the entire system. It is important not only to understand the intricacies of both electrical and air- or nitrogen-powered units, but also to comprehend the surgical demands made by the various implant systems. Some require higher speeds and less torque, whereas others require lower speeds and greater torque.
The console contains all of the electrical circuitry; the controls for speed, torque, irrigation pumps, and handpiece selection; the power source; and a light-emitting diode (LED) readout for revolutions per minute (rpm). Even the foot-controlled rheostat plugs into the unit and is powered by the console (Fig. 6-3).
FIGURE 6-3. The console, an electrical housing for low-speed, high-torque drilling equipment, should show the speed in an LED readout. It also should have adjustments for controlling the equipment, the capability to pump irrigant to the drills and to signal reverse direction, and when available, the capacity for two motors.
Power is supplied to the console directly from any standard 110-V electrical wall outlet. Consoles are produced as solid-state electronic devices. They are explosion and spark proof and lightweight (weighing 7 to 11 pounds). If implant surgery is planned in a hospital operating room, a special shockproof attachment is required for the console, and its electrical safety must be verified for the institution’s biomedical engineers. Either the manufacturer’s or the hospital’s engineering department can provide these services.
The motor housing cord plugs into the front of the console and uses its voltage supply, much the same way a cassette or CD player uses a stereo amplifier (Fig. 6-4). The tiny motors inside the housing are commonly referred to as micromotors, and they are designed to run at different speeds.
The motors most commonly used for root form implants turn at 20,000, 30,000, and 40,000 rpm. However, some motors from the same manufacturer and even the same lot can run 2000 to 3000 rpm faster or slower than others. For simplicity, these motors can be grouped into any of the three rpm ratings categories (20,000, 30,000, and 40,000). It is critical that surgeons know the motor rating, for two reasons: (1) generally, a 20,000-rpm motor has more torque (power) for bone tapping at lower speeds, and even at equal speeds, than does a motor rated at 30,000 or 40,000 rpm; and (2) because all motors loose some speed when drilling bone, a 20,000-rpm motor may not be capable of delivering the speed required to maintain the power that a high-rated motor may have.
An example can clarify the second point: Implant company A recommends using no less than 1200 rpm to perform a certain procedure. Different handpieces are available that can motors of 20,000, 30,000, or 40,000 rpm to 1200 rpm. In dense bone, electric motors often lose as much as 50 to 300 rpm per 1200 rpm (up to 25%) while cutting. The actual top speed for a 20,000-rpm motor with a reduction handpiece might drop to as low as 900 rpm at full power, which might result in burnishing of the bone. However, if the same handpiece is used with a 30,000-rpm motor, the speed could be increased another 600 rpm (to as high as 1500 rpm), which would compensate for the loss caused by the dense bone.
As a simple rule of thumb, when speeds higher than 1000 rpm are needed, a 30,000- to 40,000-rpm motor should be selected. If most of a practitioner’s procedures require less than 1000 rpm and many ultraslow procedures are expected (i.e., below 300 rpm), both a 20,000-rpm motor and a 40,000-rpm motor cut adequately at speeds well under 300 rpm; however, as may be seen in the following section, the practitioner should have many more speed-reduction handpieces.
The significance of the LED speed readout found on electrical consoles requires explanation. If a motor is rated at 20,000 rpm and a 10:1 reduction angle is chosen, the practitioner presses the 10:1 selector button on the console. The readout then shows a velocity of 2000 rpm. It is important to understand that the selector switch neither increases nor decreases actual speed; it simply calculates the change mathematically on the LED display. The only way to increase or reduce speed on any electrical or air- or nitrogen-powered system is to change the posture of a hand or foot rheostat.
Most practitioners who purchase an electrical delivery system buy the console and motor together, because one manufacturer’s motor may not couple with the console of another manufacturer. To ensure greater accuracy in readings, one brand should be chosen for all components.
The practitioner also must choose between single-motor and double-motor systems. A single-motor system can accommodate one motor. A dual arrangement allows two independent motors to be attached to a single console. The main differences between the two systems are price and versatility. With a double-motor console, the surgeon may set the motor and the handpiece for different speeds independently of each other. Motor 1, for example, can be programmed to cut at a maximum of 1200 rpm for development of an osteotomy, and motor 2 can be set to cut at 15 rpm for bone tapping. Because they cannot work simultaneously, such features as LED readout, irrigant pumps, and rheostats work only with the motor in use. If the budget permits and more than one speed range is required for certain implant surgical procedures, a double-motor system is recommended. In addition, double units eliminate the wasted time spent changing handpieces and water spray cannulas. Because most system failures occur in the motor and not the console, an additional benefit of a dual drive is the assurance of a backup device if one motor fails.
The piezoelectrical ultrasonic surgical unit is not new, but it currently is not as extensively used as perhaps it should be. The ultrasonic micro-oscillation motion of the root form diamond insert, which has a rounded end cutting tip and parallel side-cutting edges, immediately creates an osteotomy by virtue of a simple vertical sweeping motion. Also, the osteotomy can be expanded sequentially to the approximate desired diameter through use of insert tips of incrementally increasing diameter.
|Contra-Angle Reduction||Approximate Speed Range (rpm)||Approximate Power Range (rpm)|
|Contra-Angle Reduction||Approximate Speed Range (rpm)||Approximate Power Range (rpm)|
The sterility of electric motors is an issue involving cost and versatility. Most autoclavable motors cost three times as much as motors that cannot be autoclaved. Autoclavable motors usually are rated at no more than 20,000 rpm, and they run hotter than motors that cannot be autoclaved because they have no cooling vents. However, motors that cannot be autoclaved can be used with sterile, transparent drapes (e.g., Steri-Drapes, which are supplied with adhesive). These wraps are inexpensive and disposable and fit any standard electric motor (Fig. 6-5). They cover the connections at the console and allow the controls to be used through them.
The term handpiece is one of the most misused words in dentistry. Simply defined, a handpiece is any apparatus attached to an electrical or an air- or nitrogen-powered motor that accepts a bur. There are two types of handpieces: contra-angle and straight (Fig. 6-6); these enable the practitioner to increase or maintain a motor’s speed reliably.
Handpieces that reduce a motor’s top speed are referred to as speed-reduction handpieces. These are rated by the ratio of speed decrease they can achieve (e.g., a 16:1 reduction handpiece reduces a motor’s top speed by 16 times). As speed is decreased, torque is increased by the same ratio. Conversely, reduction handpieces have more power at higher speeds than at lower speeds. This phenomenon is called the handpiece power zone. With a 16:1 reduction on a 20,000-rpm motor, power is greater at 1250 rpm than at 500 rpm. Table 6-1 shows that a 16:1 reduction handpiece has near-maximum power between 950 and 1250 rpm. Below 950 rpm, both speed and power are lost rapidly. If the same 16:1 reduction handpiece is used on a 30,000-rpm motor, the top speed increases to 1875 rpm, and the power zone is found at the 1200-rpm level. It is critical that the surgeon know the motor’s top-rated speed and the handpiece power zone.
Instruments that increase a motor’s highest velocity are referred to as speed-increasing handpieces and universally are marked with a red stripe. As speed is increased by a certain ratio, power is decreased by the same ratio. For this reason, speed increases are contraindicated for root form surgery; they should be used primarily for placing blade implants.
Both speed-increasing and speed-reduction handpieces require high maintenance and are up to three times more expensive than ordinary handpieces. Generally, the higher the reduction ratio, the higher the price.
Every handpiece has more power at higher speeds than at lower speeds. It is important for the practitioner to know the speed at which the torque of each system is highest. Most of the problems that occur during root form surgery happen because changes in drill diameter are not made in sufficiently small increments and because dull drills are not changed often enough. If the practitioner observes the following six simple rules, as well as the power ranges in Tables 6-1 and 6-2, the chances for problem-free surgery are greatly enhanced:
Table 6-3 presents a list of currently available systems and some of their specifications.
|Different Console Jacks for Different Speeds||Different Motors for Different Speeds||Different Contra-Angles for Different Speeds||Tapping Capability||Reverse Capability||Audible Alarm||Autoclavable Motor||Internal Irrigation||Single Unit (1 Motor)||Double Unit (2 Motors)||Electric||Gas or Air||Variable Speed||Foot Control||Variable Irrigation Pump Flow||Output Display (rpm)|
Motor & piezo