Dental Drills Get a Redesign

Dr. Derek M. J. Turner, founder and chairman of ProDrive Systems accepted a challenge, which stemmed out of general frustration in his own dental practice. “The overall performance of the handpieces I was using was frustrating,” Turner says. “The handpieces are the bread and butter to the dentist – it is our main instrument for financial production because almost everything we do is done by reaching for the handpiece in one way or another.”

That frustration became a challenge when Dr. Gordon J. Christensen, during a dental meeting in early 2000, suggested to his colleagues that someone should tackle the outdated friction grip mechanism of high-speed handpieces and invent a way to update this design. Turner took on that challenge.

Immediately, on the flight home from the dental meeting, he jotted down about 40 ideas for improvements to the handpiece. Next, he met with Carlton University in Ottawa, Canada and hired some engineers to start putting more ideas together. Following these brainstorming sessions, they developed some prototypes.

“I began using these prototypes in my own dental practice, in order to continue refining them, eventually testing them with other dentists until founding ProDrive in 2002,” Turner explains. “Once the company was founded, we started raising funding, capital investment, and it has just grown from there.”

Now, the handpiece that a dentist uses has to be a very comfortable and familiar instrument to the dentist. According to Turner, there are probably five or six companies, out of more than 20 companies, that have 85% of the market share of dental handpieces in use. Often times, the handpiece that a dentist uses in their office is the same brand that they trained on during dental school. It is a handpiece that they know by feel, shape, weight, grip, with which they are comfortable.

“Knowing the market like this, and knowing that if we produced a new handpiece it would mean working to get every single dentist to switch over to a new, unfamiliar handpiece, we felt it was best if we started by just focusing on making the existing handpiece perform better,” Turner says.

Design Issues
There are air-driven and electric handpieces, but ProDrive’s main start is with a focus on the air-driven styles.
As you might have noticed on a visit to the dentist, attached to the end of the handpiece are hoses that carry water and air to the instrument. Inside the head of the handpiece fits the turbine. Among other components, the turbine consists of a chuck and impeller. When air passes through the handpiece it spins the impeller and powers the turbine. The chuck portion of the turbine accepts a bur (drill bit), which is the cutting point that makes contact with the tooth.

After taking a step back and looking at the overall design, the lack of durability, power, and concentricity were all major concerns Turner wanted to address. “It is very important that the bur runs smoothly and concentrically – dead straight – without any side-to-side vibration. So the entire turbine and bur needed improvements,” Turner explains. “Now, if we focused just on the turbine and bur, it would mean that dentists could use their existing handpiece and not give up the familiar instrument, since all they would be replacing was the turbine – making this a really marketable upgrade from the 1950s technology still in use.”

So what did they change?

Advancing the Turbine & Bur
They changed the turbine and bur, and turned it into a drive system by designing a non-round bur shank and corresponding chuck – a complete turbine and bur system that is compatible to upgrade approximately 85% of leading brand handpieces currently in use.

“Additionally, because lateral pressure is placed on a friction-grip system, the dentist is quickly wearing out the front bearings and in no time at all, sometimes just a few weeks after installing a new turbine, the dentist is starting on a graph of power versus time. He is losing power on a constant basis – the handpiece actually starts to fail from the first time it is used and as time goes by it delivers reduced power and losses the necessary concentricity,” Turner says.

Concentricity impacts quality, patient comfort, and procedure time. For example, a 0.9mm bur, while cutting, should appear as a pin, no wobble. A 0.9mm bur should drill a 0.9mm hole, perfect concentricity.

“Noise, is another issue. A handpiece and bur that have lost concentricity creates vibration, which means the entire unit runs noisier, it delivers unwanted vibration and heat generated on the tooth, and this, in turn, leads to more discomfort and longer procedures for the patient,” Turner states.

The System
Friction-grip – the round chuck that holds the round bur – is gone. To start, the bur is no longer round. Previously it was a round shaft with a cutting end on it. “There are thousands of different cutting ends – different materials such as diamond and carbide as well as sizes and shapes,” Turner explains. “ProDrive offers more than 550 different shapes and sizes of burs, in order to cater to all the nuisances the dentists require. However, beyond the vast selection of burs, we offer the non-round shank to work with our drive system.”

The typical friction-grip system is just a round shank bur that fits into a round chuck located inside the turbine. The dentist pushes a button on the back of the head of the handpiece, the chuck opens, and the dentist slides a bur into the chuck. With release of the button, the chuck closes around the bur. Immediately, the bur wiggles and moves a bit. However, as Turner explains, due to physics, once the bur is spinning you achieve better concentricity of the bur – because of a gyroscopic effect – so spinning it fast enough enables the concentricity to be correct. Yet, as soon as that bur has lateral pressure applied, such as placing it on the tooth surface for drilling, the concentricity is lost and the dentist is left with a bur that will not drill a straight path.

“The ProDrive bur has three flats on the shank. It is not a full triangle, as that would weaken the shaft, but if you look at the flats and you extended them out, they would make an equilateral triangle. Essentially, we made the cross section of the bur irregular, but it is physically equal on all sides,” Turner states. “The next change is with the chuck. Those three flats are repeated in the design of the chuck, so instead of the standard round design of friction-grip, the bur and the chuck actually have drive because the bur is locked into place inside the chuck with three flat sides – the bur and chuck fit exactly together.”
 

Most people have seen a dental handpiece while visiting their dentist, ProDrive Systems has set out to make that experience faster and quieter. Three flats on the bur, and repeated on the chuck, deliver drive handpiece, which holds the cutting instrument dentists use to repair teeth. ProDrive Systems no longer uses a round bur, helping deliver more concentricity to the instrument. A breakdown of the three parts that come together to create ProDrive Systems quieter, and more concentric bur and corresponding chuck system.

Manufacturability
“In the early days, all engineering and design was done in-house and we utilized contract manufacturing for the chuck and the bur,” Turner says. “Throughout the process we setup our own cut test, made the prototypes and would cut through many different materials with a set bur. Next, we would sterilize the handpiece, change the bur, and cut again – conducting this process repeatedly to determine if we lost any power. In addition to checking for power loss, we looked for wear on the inside of the chuck after using it 1,000 times, taking images and using magnification inspection to see where it was wearing until we perfected the system.”

Because of the microscopic tolerances required of the components in the turbine system, when they went on a search for contract manufacturing services they found that few companies were able to produce what they required. Originally, they thought aeronautical engineers could help because of their knowledge of aviation turbines, but after sending some CAD information to them, it was determined that they could not help. Turner’s next step was to contact companies in Asia, but the result was the same – they could not manufacture to the tolerances required.

“We ultimately ended up using SycoTec, the R&D Spin-off of KaVo (of Danaher) for engineering and balancing, with Meisinger and Sirona in the contract manufacturing arena,” Turner states. “Essentially we have one company manufacturing the chuck and the other company manufacturing the bur – since Meisinger had the experience for manufacturing burs, the iteration they make for us is the new shaft design that works with our chuck design, creating the drive for to the system.”

SycoTec comes in with the balancing of the system. Assembling, spinning and balancing every single ProDrive turbine, ensuring it runs true – since the concentricity issue and loss of power was the driving force behind this redesign.

Another important partner is Austrian based W&H, a world-leading handpiece brand. With decades of engineering and intricate manufacturing experience, they appreciated the impact the ProDrive System would have on dentistry. As Peter Malata, president of W&H explains, “The development of the ProDrive product is a step forward in the evolution of handpiece chucking systems for the retention of dental friction grip burs. Combining a positive fixation with a friction grip gives the potential to sustain a higher torque; e.g. a high load can be created when the bur is stopped abruptly, when drilling into a cotton swab. W&H will incorporate the ProDrive system into its turbine range in the future, as we believe there will be a noticeable benefit.”


Ready and Launched
In 2009 Turner and his company did a soft launch of the system in about seven cities across the United States. Then, in September 2009, the system launched exclusively with Patterson Dental in Canada. Jump to January 2010, and ProDrive became available from Patterson USA, Benco Dental, and members of the American Dental Cooperative. Currently in production with more than 1,000 parts per week, additional distributors are coming on line throughout the remainder of 2010.

While only having addressed the turbine and bur of the handpiece, the engineering of the ProDrive system does result in a great change from the existing design dentists have come to depend upon. We all know the existing sound of a dental drill. By simply upgrading the turbine of an existing handpiece with a ProDrive turbine, the sound is quieter, according to Turner, because chatter and vibration is reduced when the concentricity is perfected.

Looking at the overall performance benefits, Turner and his staff have now introduced their own handpiece to the dental market. Understanding the benefits they achieve with performance and concentricity leads them to believe they will be able to go change the existing standard in dentistry – delivering additional silence in the dental chair and offering increased speed to the dentist, and provide overall satisfaction from patient to provider.

Click here for the video about the ProDrive drill

ProDrive Systems
Montreal, Quebec, Canada
prodrivesystems.com