The case of the broken inserts

Nov. 12, 2013
CSI-type shows or programs like House are really popular for a good reason: they are puzzlers.

By Anne Nugent Guignon, RDH, MPH

CSI-type shows or programs like House are really popular for a good reason: they are puzzlers. Despite the fact that I'm not a big television fan, I really enjoy the plot twists and turns found in such shows, and I feel my time is vindicated every time I come up with the solution or right answers before the end of the show.

Similarly, health-care professionals are epidemiologists at heart. We ask questions and look for clues to understand why one patient has a higher risk for disease than another. In addition to understanding relative risk, we are charged with recommending and implementing preventive or therapeutic measures that interfere with or mitigate disease outbreaks.


Other columns by Anne Guignon


When a colleague posed a question about ultrasonic insert breakage last month, I dusted off my investigator's hat. Just as patients often hope for a very simple answer regarding disease development, this colleague was hoping for a simple, black-and-white cause for the breakage. Join me while I take you down the path of the CSI show called "The Mystery of the Breaking Ultrasonic Tips," which took place in a back-and-forth email dialogue -- not an ideal format to solve a mystery, but one that worked for the other hygienist. The following transcript recreates the electronic chat:

Dental hygiene colleague (DHC): Twenty-six ultrasonic insert tips have broken over the past six years in my clinical office. (She attached a photo that showed all of the broken tips lined up in a row, like dead soldiers in the morgue.) All of the broken tips are lined up in a row, like dead soldiers in the morgue. It appears that most of the tips were broken at the midpoint on the metal tip -- the point at which the insert has the biggest backbend.

Anne: This is a very interesting "case study" regarding an epidemic of insert fatigue. It's definitely not a normal clinical outcome for power-driven scalers. My initial questions include how many clinicians are using these inserts? How often do they get new inserts? Are all of the inserts the same brand and configuration?

DHC: The practice orders a dozen new tips every two years. Five hygienists work in the practice and they all share the same tips. The metal ends of the inserts are breaking. The count is now up to 26. I suspect that the inserts were manufactured using an inferior metal alloy, leading to premature breakage.

AG: There has to be a common denominator. If these were purchased over a six-year period of time, it would be very unlikely that the breakage is caused by a material failure, since the individual inserts would have come from different batches over the years.

Here are some additional questions. Have these all broken in the past couple of months, or has this been going on for years? Are the tips breaking during an appointment or during sterilization?

Any new hygienists to the mix? Any new units? Any units recently "repaired?"

The root cause, most likely, is a physical stressor to the metal tip in the insert. Since everyone in the office shares the inserts, it's hard to nail down the source of the epidemic of broken inserts, but I suspect a "typhoid Mary" clinician or a machine with bad electronic settings that are overstressing the metal. This is a logical pathway if the inserts have been breaking over the last six years.

DHC: The tips broke in the patient's mouth. Both ultrasonic units have been maintained and adjusted within the last two years. Inserts are sterilized in a new autoclave.

The inserts have the same insert shape and design and are all from a major dental manufacturer. Plastic grip housing the tip is intact, with no visible cracks. Inserts were leaking and overheating so the O-rings were replaced. Some tips bent, others broke off. The ultrasonic unit was checked again two months ago.

AG: Leakage is an insert design issue, generally an O-ring failure where the insert interfaces with the handpiece. A worn O-ring allows the water that cools the magnetostrictive stack to leak out of the handpiece.

Overheating is a sign that there is not enough fluid irrigant flowing through the magnetostrictive handpiece to the insert tip. Insufficient water flow can come from a blockage in the fluid port on the insert tip, an obstruction in the unit itself, constricted fluid flow into the unit, or a crimped water hose. Essentially, the problem can be anywhere from the source of the fluid irrigant all the way to the tip.

More questions come to mind. Are the units being hooked directly into a municipal water supply or are they being operated with a self-contained irrigant unit? Have the units been cleaned or maintained with special biofilm reduction products? If so, did the office follow the manufacturer's protocols for the products?

DHC: Once I noticed the overheating, I had the repairman adjust the water flow, plus I sent out the ultrasonic unit for repair and maintenance.

There are two different brands of units; one is manually tuned and the other is auto-tuned.

It puzzles me why these inserts are breaking. I was told that the insert company had made changes in suppliers for the metal used in their tips and that the metal was poor quality. There are others with the same problem.

AG: How can you be certain that the metal quality is poor? If a large company were using inferior metal alloys, the customer backlash would have been huge. I don't think inferior metals are the issue, because no company could remain in business over a six-year period while turning out products that fail. Sales would suffer and customer service would take a beating. No company would last under those conditions.

You mention overheating. That is not a function of poor metal; it is reflective of amplitude settings and insufficient irrigant flow.

And that is the end of email chat.

Any office should be concerned with a breakage history like in the case of our colleague outlined above, but the potential harm when an insert breaks in the mouth is more disconcerting. The prospect of a patient aspirating a broken tip into their lungs is a scenario I don't want to even think about.

The CSI process requires a timeline on "who, what, where, when, and how" concerning each case. The chat ended before all of my questions were answered, but my suspicions are still on the "who, when, and how" end of the equation.

In my heart, I believe one or more hygienists in this practice are overstressing the metal in the tips when using the manually tuned unit. I've seen this happen in other practices. Quite simply, it is a matter of physics. While metal insert tips are strong, they are not designed for high power settings with poorly adjusted amplitude and frequency settings. This insert drama upset my comfort zone. Power-driven scalers allow us to disrupt biofilm and are much easier on our bodies. We need to understand more about this amazing technology.

ANNE NUGENT GUIGNON, RDH, MPH, provides popular programs, including topics on biofilms, power driven scaling, ergonomics, hypersensitivity, and remineralization. Recipient of the 2004 Mentor of the Year Award and the 2009 ADHA Irene Newman Award, Anne has practiced clinical dental hygiene in Houston since 1971.

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