Periodontal disease is the most common disease of dogs and cats. Many of us have not been formally trained on how to utilize equipment used for dental cleaning safely and effectively. Since no self-respecting dog or cat will allow us to do a good job while the patient is awake, anesthesia is necessary.
During anesthesia, we should take the opportunity to perform a thorough oral and dental examination before starting the cleaning. This includes assessing the tonsils, palate, mandibular lymph nodes, buccal mucosa, tongue, and sublingual area. Many a tonsillar squamous cell carcinoma has been diagnosed early during a “routine” dental cleaning.
Because water is a necessary part of the dental cleaning, appropriate safety precautions must be taken for the technician and the patient. To reduce the quantity of aerosolized bacteria, the mouth can be rinsed with dilute chlorhexidine (0.12 percent) before scaling. This concentration of chlorhexidine is much more dilute than chlorhexidine solution that might be used on skin since high concentrations will cause ulceration of oral mucosa. This preemptive rinse may reduce the severity of the bacteremia that occurs during a dental cleaning.
The technician and all coworkers in the vicinity of the workstation should wear gloves, masks capable of high bacterial filtration, and eye protection, such as plastic goggles or disposable face shields. The patient’s eyes should be lubricated and covered to protect against entry of debris and contaminated fluid. The single most important safety precaution involves intubating the patient and checking to ensure that the endotracheal cuff is fully inflated. The air-tight seal of the cuff should be checked occasionally to prevent the patient from developing aspiration pneumonia. However, care should be taken to avoid excessive inflation of the cuff, which may result in excess pressure on the tracheal lining, or a tracheal tear. Placement of a radiopaque laparotomy sponge in the back of the throat before scaling will filter loosened debris; remembering to remove the sponge after scaling is critical.
Periodontal debridement is the term used to describe removal of hard and soft deposits from supragingival and subgingival surfaces of teeth, along with disruption of nonadherent bacteria within the sulcus. The goal of periodontal debridement is to remove bacterial endotoxins, plaque and calculus, restoring health of oral soft tissues.
Power scaling
Power scaling instruments use a water-cooled vibrating tip to remove hard and soft deposits from teeth and periodontal pockets. Vibrations are measured by frequency, or the number of times the tip moves back and forth in a second (cycles per second, also called Hertz [Hz]). Most units used in veterinary medicine are automatically tuned and have frequencies controlled by the unit. Research indicates when skillfully used, ultrasonic instrumentation is at least as effective as hand instrumentation.
Unlike hand scalers that only remove debris with direct contact, ultrasonic scalers provide the additional benefit of a stream of water coming from the tip that acts as to cool and flush debris from the sulcus. The flushing action is destructive to the biofilm by causing acoustic streaming and cavitation. Acoustic streaming is disruption of bacteria in plaque caused by churning of fluid within the confined pocket space. Cavitation is the energy created from the mist of water. As the water coolant exits the handpiece and strikes the vibrating working end, it creates thousands of water bubbles. These water bubbles implode with enough energy to disrupt bacterial cell walls.
Ultrasonic devices
Ultrasonic devices use rapid vibrations to effectively remove biofilm and calculus deposits. The transducer converts the electrical energy to mechanical energy. There are two classes of ultrasonic scalers: magnetostrictive and piezoelectric.
A magnetostrictive ultrasonic scaler may be a metal stack or a ferrite rod. The transducer in a piezoelectric ultrasonic scaler may be a quartz crystal or a ceramic disc. Ranging in frequency from 18,000 to 50,000 Hz, they are above the audible human range. Standard-size “universal” and broad tips are designed for removing medium and heavy deposits, whereas slim tip designs allow better access to subgingival pockets and furcation areas. Approximately 30 percent to 40 percent more narrow than standard tips, slim tips are approximately 0.5 mm in diameter at the blunt end and are designed to mimic periodontal probes. The slim profile enables easier access to the base of deeper pockets and improves tactility for better detection of calculus. Precision tips are extremely fragile and must be used with a light touch. Diamond-coated tips can cause soft tissue damage and excessive loss of tooth substance. Therefore, this design should be reserved for use during open-flap procedures and should be used only by highly skilled clinicians.
Tips should be replaced at least annually, or when they are bent or worn down. As the tip wears, it becomes shorter, and the effectiveness of scaling diminishes. For each millimeter of wear, a 25 percent decrease in efficiency has been noted. With magnetostrictive scalers, functional vibrations occur on the back, face (concave surface), two side (lateral) surfaces, and on the point. However, each surface has varying degrees of vibration, depending on the type of scaler used. Typically, the strongest vibrations are concentrated 2 to 4 mm from the tip. Technicians must know the specific type of unit with which they are working and must understand the differences in energy dispersal among different tip surfaces to correctly adapt the tip to the tooth for efficient scaling.
The piezoelectric scaler uses a ceramic disc or crystal as the transducer to produce the straight, linear movement of the tip. Electrical energy causes the discs to alter dimension by expanding and contracting, sending vibrations to the tip at a frequency ranging from 25 to 50 kHz. Because of the back-and-forth motion, the tip is active only on the two lateral surfaces, forcing the operator to pivot the wrist as the tip is moved around the tooth. If the other surfaces are accidentally adapted to the tooth, the operator will be warned by a different sound and by incomplete removal of debris. Limitations of effective vibrating surfaces cause the piezoelectric scaler to be more technique-sensitive than other power scalers. The ceramic disc of the transducer is fragile and is easily breakable if the handpiece is accidentally dropped.The power knob adjusts the amplitude—the distance the tip is moving back and forth in one cycle. Greater distance is higher power. Higher power is necessary to remove heavy deposits, whereas low power is satisfactory for removing plaque. It is recommended to use the lowest power setting that will accomplish the task. Low power should always be used with thin tips to prevent the tips from breaking.The water knob adjusts the flow of water through the handpiece. Because ultrasonic scalers produce heat, fluid must be adequate to prevent pulp damage caused by heat during scaling. Pressure of the water supply line to the unit must measure a minimum of 25 psi. A warm or hot handpiece is an indication that water pressure is inadequate, and the clinician must immediately stop and make adjustments by increasing the amount of water and checking the water pressure (if a portable water tank is used). With magnetostrictive units, the water knob should be turned until water exits the tip as a mist, rather than just as a straight stream. Water on the piezoelectric unit should be adjusted to a steady drip.
Though ultrasonic scalers are very helpful tools, you will also need to have hand scalers and curettes in your armamentarium. Next month’s column will cover hand instrumentation for cleaning teeth.
John R. Lewis, VMD, DAVDC Fellow, AVDC OMFS, practices at Veterinary Dentistry Specialists and teaches at Silo Academy Education Center, both in Chadds Ford, PA.