Ultrasonic and Sonic Instrumentation

Core Review

Technology Overview

Ultrasonic scalers operate at frequencies of 18,000-50,000 cycles per second (Hz). They convert electrical energy into mechanical vibrations at the working tip. Water flows through the handpiece or tip for cooling, lavage, and cavitation effects.

Sonic scalers operate at lower frequencies (2,500-8,000 Hz) and are driven by compressed air rather than electrical current. They are less commonly used but are available in some practice settings.

Magnetostrictive Ultrasonic Systems

Mechanism:

• Electrical current passes through a coil in the handpiece, creating a magnetic field
• The magnetic field causes a stack of nickel-alloy (or ferromagnetic) strips in the insert to expand and contract
• This oscillation produces elliptical (orbital) tip motion
• Frequency: 18,000-45,000 Hz (typically 25,000 or 30,000 Hz)

Tip Motion:

• Elliptical (orbital): The tip moves in a three-dimensional elliptical pattern
• All surfaces of the tip are active: Because of the elliptical motion, all sides of the magnetostrictive tip are capable of scaling. You can use the lateral surfaces, the back, and the tip face — any portion of the tip that contacts the tooth can remove deposits
• This means adaptation is more forgiving — the tip does not need to be precisely oriented to a specific surface

Insert Types:

• 25 kHz inserts: Larger amplitude (stroke), more powerful. For heavy calculus removal. Stack typically contains more metal strips.
• 30 kHz inserts: Smaller amplitude, gentler. For biofilm disruption, light calculus, and sensitive patients.
• Tip designs: Universal (straight), right/left curved, furcation-specific, and implant-specific

Water Flow:

• Water passes through the handpiece, around the insert
• Functions: (1) cooling the tip to prevent thermal injury to the tooth, (2) flushing/irrigating the pocket to remove debris and bacteria (lavage), (3) creating cavitation (formation and implosion of microscopic bubbles that disrupt biofilm)
• Adequate water flow is non-negotiable — without it, the tooth can be thermally damaged within seconds

Piezoelectric Ultrasonic Systems

Mechanism:

• Electrical current passes through a crystal (typically quartz or ceramic) in the handpiece
• The crystal deforms in response to the electrical charge (piezoelectric effect), causing mechanical vibration
• The vibration is transmitted to the working tip
• Frequency: 25,000-50,000 Hz

Tip Motion:

• Linear (back-and-forth): The tip moves primarily in a single plane — forward and backward
• Only the LATERAL surfaces are active: Because the motion is linear (not elliptical), only the sides of the piezoelectric tip effectively remove deposits. The tip face and back do not move sufficiently to scale
• This means adaptation is more technique-sensitive — the lateral surface must be adapted to the tooth for effective scaling

Tip Design:

• Threaded or screw-in tips that attach to the handpiece
• A wide variety of tips are available for different applications
• Tips are typically thinner and finer than magnetostrictive inserts, allowing better access to tight pockets and furcations

Comparison: Magnetostrictive vs. Piezoelectric

Water: The Critical Third Component

Water is not optional in ultrasonic scaling. Its functions:

1. Cooling: The vibrating tip generates frictional heat. Without water, the tooth surface can rapidly reach temperatures that damage the pulp. Adequate water flow prevents thermal injury.

1. Irrigation/Lavage: The water flushes the subgingival pocket, washing away debris, blood, and dislodged bacteria and calculus fragments. This improves visibility and reduces bacterial load.

1. Cavitation: Ultrasonic vibration in a liquid medium creates microscopic bubbles that form and implode. This implosion releases energy that disrupts bacterial cell walls and biofilm. Cavitation occurs even at sites the tip does not directly contact.

1. Acoustic microstreaming: The ultrasonic energy creates tiny currents in the irrigant fluid that help disrupt biofilm and propel fluid into inaccessible areas.

Water adjustment: The water flow should produce a visible mist or spray at the tip. For subgingival use, the water should create a cooling lavage without flooding the field so rapidly that visibility is lost.

Clinical Application

Indications for Ultrasonic Instrumentation:

• Heavy supragingival and subgingival calculus
• Moderate to deep probing depths (≥4 mm; the lavage and cavitation reach areas the tip cannot contact directly)
• Furcation involvement (narrow tips, cavitation benefit)
• Time efficiency — ultrasonic debridement is faster than hand instrumentation for moderate to heavy deposits
• Reduced operator fatigue for extensive scaling
• Removal of orthodontic cement after bracket removal (with appropriate tip)

Contraindications and Precautions:

Absolute Contraindications:

• Patients with communicable diseases transmitted by aerosols (active tuberculosis) are generally not candidates for ultrasonic scaling due to aerosol generation
• This is mitigated by appropriate PPE, high-volume evacuation, and pre-procedural rinsing

Precautions (use with caution or modify technique):

• Cardiac pacemakers: Older, unshielded pacemakers could be affected by magnetostrictive ultrasonic electromagnetic fields. Current pacemakers are shielded and generally safe. Consult the patient's cardiologist. Piezoelectric units do not generate a magnetic field.
• Implanted defibrillators: Similar considerations. Consult the cardiologist.
• Communicable diseases (hepatitis, HIV): Standard precautions apply. The risk is to the clinician and other patients via aerosol contamination. Use high-volume evacuation, pre-procedural antimicrobial rinse, and appropriate PPE.
• Demineralized tooth surfaces: Ultrasonic tips can aggressively remove softened tooth structure. Use with caution around white spot lesions and early carious lesions.
• Hypersensitivity: Ultrasonic vibration and cold water spray may cause discomfort. Use warmed water if available; start with lower power.
• Exposed dentin/cementum: Lower power settings to minimize sensitivity and tooth structure removal.
• Children: Use with caution; developing teeth have larger pulp chambers and thinner dentin.
• Respiratory compromise: Patients with COPD, asthma, or recent respiratory infection may have difficulty tolerating the water spray and aerosol. Use high-volume evacuation and consider hand instrumentation.
• Dysphagia: Patients with difficulty swallowing may aspirate water. Careful positioning, high-volume evacuation, and brief treatment periods.
• Porcelain/ceramic restorations: Ultrasonic tips can scratch or chip porcelain surfaces. Use specialized tips (plastic or Teflon-coated) or avoid ultrasonic instrumentation on these surfaces.

Contraindications for Sonic Scalers:

• Sonic scalers operate on compressed air. Use with caution in patients with compromised respiratory function.

Power Settings and Technique

Power (amplitude):

• Higher power = larger tip stroke (amplitude) = more aggressive calculus removal = more heat
• Lower power = smaller tip stroke = gentler debridement = less heat
• General approach: Start with lower power and increase as needed. The appropriate power is the lowest that effectively removes deposits.
• For heavy calculus: moderate to high power
• For biofilm disruption and light calculus: low power
• For implant maintenance: very low power with specialized tip (plastic, carbon, or Teflon-coated)

Tip Adaptation:

• The vibrating tip must contact the calculus or tooth surface, not the soft tissue wall of the pocket
• For magnetostrictive: adapt any surface of the tip (lateral, face, or back) to the deposit. Use a feather-light, paintbrush-like stroke.
• For piezoelectric: adapt the LATERAL surface. Orient the tip so the side contacts the deposit.
• Working angulation: approximately 0-15° for maximum effectiveness (this is different from hand instruments, which require 70-80°)
• Tip should be in constant, light contact with the tooth — do NOT press firmly (increased pressure dampens the vibration and reduces effectiveness)

Stroke:

• Use light, overlapping, rapid strokes
• Let the machine do the work — minimal lateral pressure is needed
• The tip should feel like it is "floating" over the surface
• Avoid prolonged contact on a single spot (heat buildup)

Aerosol Management and Infection Control

Ultrasonic instrumentation generates significant aerosols — a cloud of microscopic water droplets, blood, saliva, and microorganisms that can remain airborne for extended periods. Infection control measures include:

1. Pre-procedural antimicrobial rinse:

• Patient rinses with chlorhexidine gluconate 0.12%, essential oil mouthrinse, or povidone-iodine for 30-60 seconds before treatment
• Reduces the microbial load in the oral cavity, decreasing the infectious potential of the aerosol

2. High-volume evacuation (HVE):

• The assistant or clinician uses large-bore suction to capture the aerosol at its source
• HVE removes approximately 90% or more of aerosolized particles
• Position the HVE tip as close to the working area as possible without interfering with instrumentation

3. Personal protective equipment (PPE):

• N95 or equivalent respirator mask (not just a surgical mask)
• Face shield or eye protection
• Gown
• Gloves

4. Environmental controls:

• Treatment room ventilation
• Air filtration systems (HEPA)
• Allow adequate time between patients for aerosol settling

5. Dental unit waterlines:

• Ultrasonic scalers draw water from the dental unit waterlines. These lines can harbor biofilm (bacteria, fungi).
• Regular waterline maintenance: flushing, chemical treatment, and monitoring
• Use of sterile water or water that meets EPA standards for drinking water (<500 CFU/mL)

Sonic Scalers

Mechanism: Compressed air drives a rotor in the handpiece, producing oscillation of the attached tip. Frequency: 2,500-8,000 Hz.

Tip motion: Elliptical, similar to magnetostrictive ultrasonic but at a much lower frequency. All tip surfaces are active.

Advantages:

• Less expensive than ultrasonic systems
• Attaches to the existing dental unit air supply (no separate electrical unit needed)
• Less heat generation, less water needed

Disadvantages:

• Less effective on heavy calculus (lower frequency and power)
• Louder than ultrasonics
• Compressed air may be uncomfortable for some patients
• Larger tip size, less access in tight areas

Implant Maintenance

Special considerations for ultrasonic instrumentation around dental implants:

• Standard metal tips will SCRATCH and damage titanium implant surfaces — they must NEVER contact the implant
• Use plastic, carbon-fiber, or Teflon/PEEK-coated tips specifically designed for implant maintenance
• Use low power
• Focus instrumentation on the implant abutment and prosthetic components, not the implant body (which should be osseointegrated and not exposed)
• If the implant body is exposed (recession, peri-implantitis), use plastic/coated tips with extreme care

Clinical Application

You are treating a patient with Stage III, Grade B generalized periodontitis. The patient has a cardiac pacemaker (implanted 2015). You plan to use a piezoelectric ultrasonic scaler for efficiency.

Pre-treatment: Verify that the pacemaker is shielded (most post-2000 models are). Document the pacemaker type and cardiologist clearance. Because piezoelectric units do not generate a magnetic field, they are safer for pacemaker patients than magnetostrictive units.

During treatment: Use high-volume evacuation, pre-procedural chlorhexidine rinse, appropriate PPE including N95 mask. Adapt piezoelectric lateral surfaces to deposits. Use moderate power for heavy posterior calculus, lower power for biofilm disruption in shallower pockets.

Post-treatment: Allow aerosol settling time before removing PPE. Clean and disinfect the operatory.

Common Traps

• TRAP: Confusing magnetostrictive and piezoelectric tip motion. Magnetostrictive = elliptical, all surfaces. Piezoelectric = linear, laterals only.
• TRAP: Thinking all surfaces of a piezoelectric tip are active. Only the lateral surfaces are clinically effective.
• TRAP: Using a magnetostrictive ultrasonic on a patient with an unshielded pacemaker. The magnetic field can interfere. Consult the cardiologist; consider piezoelectric.
• TRAP: Using metal tips on dental implants. This scratches the titanium surface, creating roughness that promotes biofilm accumulation and peri-implantitis.
• TRAP: Forgetting that water is mandatory. An ultrasonic tip without water can cause thermal pulp damage within seconds.