Building a Better Appliance

Orthodontic Products: Were you an inventor/tinkerer before you became an orthodontist?

Chris Kesling, DDS, MS: When we were kids, we spent our weekends helping my father with projects around the house and on trips back and forth to the hardware store. I guess you could say we were exposed to my father’s creative spark through association with him over the years. He was always working on one project or another, and we just picked up things through him.

Restoring antique and classic cars was his special passion, and we spent a lot of time working with him and his mechanic on numerous antique cars over the years. With these projects, you often have to improvise and make parts from scratch because they simply aren’t available anymore. I learned a lot doing a frame-up restoration of a 1928 Model A roadster in high school. One fun project was building a “souped-up” Model T roadster. We used special brackets to lower the frame, and installed a vintage high-performance radiator and cylinder head with four valves per cylinder. We could get that thing up to almost 50 miles an hour, which was pretty fast for a model T Ford. I just finished the restoration of a 1950 Chevy pickup truck.

OP: What inspired you to invent the Tip-Edge® PLUS bracket?

Kesling: The development of the Tip-Edge PLUS bracket was a team effort between my father, Dr Parkhouse, and myself.

OP: Did you work with a company all along, or did you create a prototype that you marketed to various companies?

Kesling: TP is our family business, so we really didn’t shop the idea around to any other companies. If you do shop an idea around to companies you aren’t directly associated with, you would want to make sure you have a signed confidentiality agreement before revealing your idea.

The original Tip-Edge bracket and archwire slot were invented by my father in the mid 1980s to facilitate retraction with the edgewise appliance and eliminate the binding that occurs between the archwire and the 1925 E.H. Angle archwire slot as teeth tip during retraction. The Tip-Edge slot also allows for retraction of anterior teeth or entire arches using only very light intraoral forces (1 to 2 ounces).

Our archwire slot is unique in that its effective vertical dimension actually increases in size relative to the archwire, during retraction. After retraction and/or space closure, a full-size, .0215- x .0275-inch stainless steel wire is engaged for the last half of treatment and the teeth are brought to their final desired axial inclinations, powered originally by individual uprighting springs. This occurs as the archwire slot gradually and gently closes back down to .022 inches in the vertical dimension during final uprighting. The torque and tip built into each bracket becomes fully expressed.

OP: Has the Tip-Edge PLUS bracket done everything you wanted it to when you first envisioned it, or is there something else you would like to do with a bracket?

Kesling: The main drawback of the original Tip-Edge bracket was the uprighting springs (Side-Winders), which were required to upright teeth to their final axial inclinations. The springs were a major turnoff for many orthodontists. During my teaching at St Louis University and Case Western Reserve University, I experienced the frustration firsthand when I saw the residents trying to figure out which spring to put on which bracket as well as properly engaging the spring once it had been selected. There were some nightmare scenarios in the clinic on occasion, where a resident would manage to put the wrong spring on every bracket and the patient would manage to slip out without seeing me first. Of course, when this happened things were getting worse instead of better until their next appointment!

A few years after the invention of the original Tip-Edge bracket, I invented a modified version, which we ended up calling the “Deep-Groove” Tip-Edge bracket. It featured a conventional preadjusted edgewise archwire slot cut into the base of the Tip-Edge archwire slot. A cap was pressed into the deep groove, filling it until retraction was completed. The cap was then removed for the final stage of treatment, when uprighting and torquing of teeth to their final inclinations occurs. A special torquing auxiliary called a “Torque Bar” was then engaged into the deep groove to torque the incisors to their final inclinations.

Dr Parkhouse and I had both thought that we could somehow use this concept on all the teeth, with an underlying nickel titanium wire engaged in the deep groove to upright and torque the teeth and eliminate the need for uprighting springs. Drawings were made, and the tool and die department at TP made fixtures to cut the deep grooves into existing Tip-Edge brackets for all the teeth.

This was a fast and inexpensive way to get a few sets of prototype brackets ready for clinical testing. I immediately switched a few patients over to them midtreatment. Luckily, we didn’t spend much money or time on this R&D project! The nickel titanium wire kept slipping out from the deep groove slots under the main archwire. No matter what I tried, I couldn’t get it to remain in place.

All three of us had been toying with the idea of somehow incorporating a horizontal tunnel into the base of the bracket through which we could engage a nickel titanium wire to provide the uprighting and torquing force while a full-size, rectangular archwire was engaged in the main archwire slot. We just couldn’t figure out how we could engage the nickel titanium wire without distorting it.

About that time, I was on the program for the Mexican Orthodontic Society meeting in Ixtapa along with Dr Dwight Damon. I attended his lecture and was amazed at how much he was flexing nickel titanium wires without any permanent deformation. I believe he was using some of the copper versions that were relatively new at that time. When I saw what he was doing, I immediately knew that we could make the PLUS bracket with a horizontal tunnel work. We would be able to thread the nickel titanium wire through the tunnels without causing any permanent deformation.

When I returned, I relayed what I had seen to my father and Dr Parkhouse. Within a few weeks, we had new fixtures running and were cutting deep tunnels in conventional Tip-Edge brackets. Once again, we switched patients in the final stage of treatment over to the new brackets. Immediately, we experienced firsthand that it is possible to thread nickel titanium wires through what came to be known as “deep tunnels” without permanent deformation.

The big question then was whether or not these wires were strong enough to upright and torque teeth. We switched as many patients as possible over to the prototype brackets midtreatment. It would take us at least 9 months to find out if they had the power we needed. Using panorex and lateral head x-rays we found that, if anything, the .014-inch nickel titanium wires were uprighting the teeth faster than individual uprighting springs.

Once we were sure that the Tip-Edge PLUS prototype brackets were producing good treatment results, we went to the drawing board to design the molds for the production brackets. This allowed us to continue to refine the bracket design in several ways, including beveling the entrances to the tunnels to make it easier to thread the nickel titanium wires.

Ultimately, the elimination of the need for uprighting springs has created a renewed interest in the use of differential tooth movement by both orthodontic residents and practicing orthodontists. I would say that we are all very pleased with what we are seeing in the clinic every day with the Tip-Edge PLUS bracket. However, I am sure there will be continuing improvements on down the line. For those interested, the treatment records of several of our latest PLUS patients will be included in the second edition of Dr Richard Parkhouse’s book titled Tip-Edge Orthodontics and the PLUS Bracket, which will be published by Mosby later this year.

OP: What is the Outrigger® appliance, and how did you come to invent that?

Kesling: The Outrigger is a habit “maker” rather than a habit “breaker” appliance. It is simply an auxiliary with spring-loaded hooks on each end that protrude labially if Class II elastics are not worn. It doesn’t hurt the patient, but is simply an annoyance that reminds them that the elastics are not engaged. If the elastics are being worn, they pull the hooks down incisally into much more comfortable positions.

We always consult with the parents before placing the Outrigger and explain that it doesn’t hurt the patient but is simply a means of trying to get patients into the habit of wearing their elastics. We ask them to call and set up a special appointment to have the Outrigger removed if the incisors become edge-to-edge before their next regularly scheduled appointment. The parents, and often the patients, are relieved and pleased once we explain how the auxiliary works. By this time, the patients are tired of having me and their parents hound them about their lack of cooperation.

The Outrigger usually lasts from one to two appointments, since the continuous flexing seems to cause breakage over time. Surprisingly, the patients often ask for a new one to be engaged. If not, hopefully they have gotten into the habit of wearing their elastics and the appliance is no longer required.

OP: How is the SAL® retainer different from other retainers on the market?

Kesling: The SAL (Self Activating Loops) is a spring-aligner-type retainer that features a labial bow partially fabricated from nickel titanium wires. Conventional spring aligner bows and loops are fashioned from stainless-steel wire which tends to relax during wearing. The looped portions of the SAL labial bow are formed from nickel titanium wire to ensure permanent activation of the labial bow. This eliminates periodic retightening of the retainer.

During fabrication of the retainer, the final step is to pull the ends of the loops toward each other with power chain or a steel ligature tie. The labial acrylic portion of the bow is then salt-and-peppered directly over the ends of the labial bows and the steel tie or power chain. Once the acrylic sets up, the loops are permanently locked into activated positions that are maintained through the shape memory property of the wire from which they are formed. The result is an active retainer that never needs adjusting. With conscientious wear, the anterior teeth cannot relapse.

OP: How much clinical testing of these products do you have to do before you can sell them?

Kesling: The amount of clinical testing required depends on what the invention is designed to do. Once we determined that we could successfully thread the nickel titanium through the deep tunnels of the PLUS brackets, we had to wait 6 to 9 months before we were sure it delivered enough force to produce the desired uprighting and torque changes.

The tooth positioner was, in no small part, the result of a challenge put to my grandfather, Dr H.D. Kesling, by his good friend, Dr Charles H. Tweed, in 1940. He presented a table full of start and finish models to Charlie, who reviewed them and stated, “They look pretty good, but when are you going to finish them?” During the long drive back to Indiana from Tucson, he became determined that he was going to show Charlie just how well he could finish cases.

His determination eventually led to the development of the tooth positioner. Once the first few positioners were made and delivered, it only took a few weeks to witness the dramatic finishing abilities of this appliance. He always said that when the first few patients came back for their positioner checks, the “hair on my arms stood up” (he was pretty much bald).

R&D for the Outrigger was a much longer process due to the problems we experienced with breakage. We built a special “chewing machine” that opened and closed with an attached counter to record the number of cycles until each prototype broke. We tested different sizes of wires made from various alloys until we finally found the one combination that held up the longest. It took us at least a year and a half to 2 years of lab and clinical testing before we brought the Outrigger from conception to the market.

OP: Do you have a next invention in mind, and if so, what is it?

Kesling: Yes, we usually have at least one or two new ideas that we are kicking around in the clinic or tool-and-die area. The majority don’t ever make it to market due to one thing or another, but we have some promising ones coming down the line. I can’t say too much about them at this point, but I think at least one or two will be of great interest to most orthodontists.

Chris Kesling, DDS, MS, is the sole practitioner in the two offices of Kesling and Rocke Orthodontics. He currently holds 11 patents on various orthodontic appliances and is co-inventor of the new Tip-Edge PLUS bracket along with his father Dr Peter Kesling, and Dr Richard Parkhouse. He has financial interest in the products mentioned here. He can be reached at