Originally published in the September 2015 issue of Veterinary Practice News.
When it comes to extraction of firmly rooted teeth in dogs and cats, the high-speed hand piece is the most efficient tool for the job. It is used to remove bone lateral to the roots and to section multirooted teeth so that individual crown-root segments may be removed as if they were single-rooted teeth.
The high-speed hand piece is driven by air and relies on revolutions per minute (RPM) to accomplish its job. It typically runs at 200,000 to 400,000 RPM.
Because the hand piece relies on RPM and not torque, the tool is most efficient when used with a light touch and with the foot pedal pushed to the floor. Pressing too hard will result in binding of the bur and that unpleasant smell of burned hard tissue. Eye and face protection should be used at all times when using burs.
The high-speed hand piece is held with a modified pen grasp (Figure 1), which provides the best control over the tiny burs placed in the head of the hand piece. The burs are secured with a push-button mechanism, a locking latch mechanism or a wrench.
Hand pieces that use a wrench to secure the burs require more time to switch from bur to bur, but these hand pieces tend to be more durable than push-button units. A bur is placed and then tugged on to ensure it is well-seated. The high-speed hand piece uses FG burs, which stands for friction grip. Standard length FG burs are 19 mm long, whereas surgical-length FG burs are 25 mm.
In contrast to a high-speed hand piece that accepts only FG burs, a low-speed handpiece accepts a prophy angle for polishing, HP burs (44.5-mm-long straight burs often used for rabbit and rodent dentistry) and an attachment that allows for use of LA (latch attachment) burs.
The low-speed hand piece relies on torque rather than RPM. The LA burs on a low-speed hand piece do not cut through teeth with nearly the efficiency of the FG burs on a high-speed tool.
What Burs Do You Need
“What burs do I need?” is one of the most common questions I receive from general practitioners.
A large variety of burs are helpful in veterinary dentistry, and everyone has his favorites. Here I will focus on the essential list of burs for every general practice performing extractions in dogs and cats (Figure 2).
© 2015, John Lewis, VMD, NorthStar VETS
Figure 2: The essential assortment of burs for use in general practice: surgical length half-round carbide bur; surgical length No. 2 round carbide bur; surgical-length No. 4 round carbide bur; No. 701 crosscut fissure carbide bur; surgical-length No. 702 crosscut fissure carbide bur; No. 23 round diamond bur.
Round burs are helpful for removal of bone and exposure of a firmly rooted tooth root. Round burs come in sizes ranging from small to large: one-quarter, one-half, 1, 2, 4, 6, 8. A general rule of burs: the larger the working end of a bur, the more damage you will cause if the bur’s swirling vortex pulls in and wraps up adjacent soft tissue.
Therefore, I try to use the smallest size bur that gets the job done. When I am making a large window lateral to the root of a dog’s canine tooth, I will use a No. 4 round bur. When I am making that window lateral to the root of a cat’s canine tooth, I will use a No. 2 round bur.
The half-round bur is my go-to in cases where any wrong move can result in unwanted damage to adjacent soft or hard tissue. For example, the half-round bur is wonderful for removing root fragments by creating a small moat around the root and a small lateral window to allow for placement of a small dental elevator on the palatal or lingual side of the root to gently pry the root tip from its socket.
The No. 701 crosscut fissure bur is what I use to section multirooted feline teeth. Some dentists prefer a more dainty No. 699 bur for sectioning cat teeth, but make sure you are wearing eye protection because the tips of the working end can break off and go flying.
I use a surgical-length No. 702 bur to section multirooted teeth in dogs. The “L” next to a designation of No. 701 L or No. 702 L refers not to a longer overall bur length but rather to a longer cutting portion of the working end.
The No. 23 diamond bur is different from the other burs described here.
Until now, all burs discussed were carbide burs, which are burs with aggressive cutting flutes. Carbide burs melt away bone with ease and cut through tooth structure more efficiently than diamond burs. Diamond burs are less aggressive. I use diamond burs for a variety of reasons, but most commonly they are used to smooth rough edges of an extraction site before closure.
All burs can accidentally wrap up adjacent soft tissues, but diamond burs are less likely to do so compared to carbide burs.
When I teach continuing education courses to general practitioners, I often use this analogy for describing use of the high-speed hand piece and FG bur to expose tooth roots: Think of yourself as an archaeologist at a dig, looking to unearth a precious relic that must not be damaged.
At CE events, I see too few archaeologists and too many construction workers using a jackhammer. Removing the thin layer of bone that covers the lateral surface of the roots will increase your odds of removing the root, but drilling deep into the root structure will increase the chances of the root breaking when elevating with the dental elevator. Practice makes perfect.
Should used burs be discarded immediately? Some are specifically designated as single use. Many hand-piece manufacturers recommend discarding all burs after a single use to extend the life of your turbines.
I hope this overview helps clarify the use of various burs. Until next time, keep on drilling!