Powering the Calculus Away

“Picture a thin tree in the wind and a redwood tree in the wind.  Less movement happens in the thicker piece of wood than in the thinner, willowy tree.”

Q. Describe the differences between magnetostrictive and piezo ultrasonic scalers.

A. The most significant clinical differences lie in how the tips move. The magnetostrictive uses an elliptical or figure-8 motion. The magnetostrictive moves both up and down and right to left, where as the piezo is primarily a linear, up and down motion.  The way the tips contact the tooth and the way they move are different, which can affect patient comfort. They also generate power differently and the frequencies of the tips are not the same. With magnetostrictive, any surface can be used. With a piezo, only the lateral sides can be used or at least are most effective.

The tips have their maximum activity in different places. On the piezo electric, the instrument tips are most effective on the two lateral surfaces where they’re moving back and forth against the tooth. The magnetostrictive is most active on the top and bottom instead of the sides.

Q. Is there potential danger to the tooth surface when using ultrasonics?

A. The point of the tip has the most active energy and movement so it should not come into direct contact with the root surface because it could damage it. I do think there is a distinction to make, however, when dealing with a really tenacious piece of calculus. If the tip is used truly on the calculus and not on the tooth, this is the most effective way to get rid of the calculus. It is like jackhammering off the calculus deposit.  I wouldn’t want a jackhammer on the root of a tooth but sometimes I do want it on a really tough piece of calculus.  Philosophically, two rules exist in dental hygiene. Number one is that the treatment provided must be safe and number two is that treatment must be effective. Avoiding using the point on the root surface is to protect the tooth.

Q. Does tip size make a difference?

A. Choosing the right tip is important.   The thickness of the tip affects the movement—the thinner the tip, the more movement occurs. The power setting also influences how much movement happens.  With hand instruments, the lightest lateral pressure that will do the job is used to ensure maximum comfort for patients. With ultrasonics, this correlates to using the lowest power that will do the job in consideration of patient comfort. With ultrasonics, thinner tips should be used with lower power and thicker tips with higher power. The tip and the power should be dictated by the type of deposit being removed.

For heavy calculus, the thickest tips should be used with higher power. When only biofilm is being removed, the thinnest tip on the lowest power is best. With the slim style tips, half power is the maximum but quarter power or less should be used if it will accomplish the task. With a really thin tip and high power, a lot of activity and movement are happening.  Athicker piece of metal will move less. Picture a thin tree in the wind and a redwood tree in the wind. Less movement happens in the thicker piece of wood than in the thinner, willowy tree.

Q. Is there a special technique for calculus removal that is different from biofilm removal?

A. In both cases, the primary technique is to position the terminal end of the ultra-sonic tip like a periodontal probe, parallel to the long axis of the tooth and point toward the apex. This will most effectively reach the subgingival and interproximal areas. Biofilm is important to remove but it is fairly easy to get off. The main point in biofilm removal is to contact every part of the root surface.  Overlapping strokes should be used with low power and light lateral pressure. The movement can be very quick because you’re not trying to break up accretions that are firmly attached to the tooth but rather contacting deposits that can be easily disrupted. Quick and light strokes can be effective. It is a common misconception that rinsing the area and having water flow onto the root surface are effective. Certainly lavage has many benefits but I believe that getting the ultrasonic tip in contact with the biofilm is the goal. The efficacious area of action around the instrument tip is fairly narrow. I often hear hygienists talk about how much faster ultrasonic scaling is than hand scaling. In reality, it takes just as many strokes with one as the other, but with ultrasonics, the working strokes can be taken faster. Ultrasonics work by putting a lot of little microfractures into the calculus deposit that is adhering to the tooth. I think that a slower motion is more effective with heavy calculus compared to the quicker movements that work on biofilm.

Q. Do tips become less effective when worn down?

A. Definitely. With routine use tips become shorter. Because the tip has the most movement, wearing down or shortening translates to less tip movement. With consistent use, tips typically last 9 months to a year. The tip length is measurable and needs to be routinely monitored. Most manufacturers have templates that allow comparison of the current length of the ultrasonic tip to the ideal length. They illustrate how much the tips are worn and if they need replacing.

Q. Do you believe it’s acceptable to leave burnished calculus as long as the biofilm on the surface of the calculus is removed?

A. No I don’t. With ultrasonic instrumentation on very dense or tenacious calculus, it is easy to partially remove and burnish the deposits. The surface feels smooth but calculus is still present. At a re-evaluation appointment, there is a very high correlation between incomplete healing of the adjacent tissue, including bleeding on probing and residual calculus, regardless of how smooth or deplaqued it is. With patients who have regular hygiene care, operators can see how the tissue has recovered and look at where it still bleeds, which often predicts quite well where the calculus remains.  With the dental endoscope, it’s clear when the calculus is burnished smooth as opposed to removed because of the inflammation on the inside surface of the pocket opposite the residual calculus.

From Dimensions of Dental Hygiene. March 2005;3(3):18, 20.