Intraosseous drug delivery device and method

An intraosseous and/or hard tissue drug delivery device and method is disclosed that perforates hard tissue and provides a drug delivery passage into underlying tissue. The device of the present invention includes a hollow drill bit and a stylet removably inserted into the hollow drill bit. The stylet keeps the bore of the hollow drill bit from plugging up during drilling. The stylet is removed after drilling to permit the operator to inject medication through the bore of the hollow drill bit.

FIELD OF THE INVENTION 
This invention relates to medical devices used to deliver medication 
through or into bone and other hard tissue. In particular, this invention 
relates to a medication injection device with a hollow drill bit useful 
for delivering medication through the hollow drill bit. The invention also 
relates to a method of using the medication injection device for 
intraosseous drug delivery. 
BACKGROUND OF THE INVENTION 
Dentists often administer local anesthetic to patients to minimize pain 
during dental procedures. Many dentists and patients, however, are 
dissatisfied with the results that dentists achieve using traditional 
anesthetic injection techniques. Problems with administration of 
anesthetic include: delays between injection and effect, the long duration 
and extent of postoperative numbness for patients, and the occasional 
inability to achieve total anesthesia. 
One prior art solution was an intraosseous injection technique developed in 
the early 1900's. This intraosseous injection technique involved a 
three-step procedure. First, the gingiva over a target point of 
perforation (the point between the problem tooth and the adjacent tooth) 
was topically anesthetized. Second, a dentist drilled through the cortical 
plate of the jaw bone to create a hole. Lastly, a solution of local 
anesthetic was injected through the hole into the cancellous bone. The 
intraosseous injection technique eliminated some of the problems of the 
traditional injection. The anesthetic took effect quickly and effectively 
and caused little postoperative numbness. In addition, unlike other 
techniques, it worked well in almost all patients. However, the 
intraosseous injection technique had many problems. In addition to being 
difficult to perform, the technique produced large holes causing 
significant bone trauma with increased risk of bone infection. 
One prior improvement of the intraosseous injection technique was the 
development of the Stabident System which involved the use of a drill with 
a small diameter (0.016 inch) drill bit. The use of small drill bit 
reduced tissue damage and the risk of infection. In spite of these 
advantages, however, the Stabident System had several drawbacks. In 
particular, dentists were still required to switch to a hypodermic needle 
to inject anesthetic once a hole was drilled with the small drill bit. 
This injection step was difficult because the opening produced by the 
small drill bit was often difficult to locate because it is covered by 
soft tissue. Another problem with the Stabident system was that stainless 
still drill bits were not properly tempered, so that the drill bits 
occasionally wore out prematurely. Worn out drill bits generated excessive 
heat during use that caused heat damage to the surrounding bone tissue. In 
addition, excessive heat levels occasionally caused melt-down and 
detachment of a plastic hub attached to the drill bit, which resulted in 
the detached drill head being left inside the patient's jaw bone leading 
further complications. 
Rotary dental tools with hollow bits have been used in the past as a 
grinding tool. Such a tool has a low speed and relatively large-diameter 
hollow bit for grinding bone while supplying water to the grinding area to 
lubricate and flush particles. However, this art does not disclose a means 
to supply anesthetic or medication to a tooth. 
SUMMARY OF THE INVENTION 
In order to meet these concerns, the present invention is directed to an 
intraosseous and/or hard tissue drug delivery device and method that 
provide a easily identified drug delivery passage for the operator, which 
thereby greatly extends the applicability of the intraosseous injection 
technique. In other words, this invention is an intraosseous and/or hard 
tissue drug delivery system that perforates the hard tissue and also 
provides a clear drug delivery passage through the soft tissue. 
The device of the present invention includes a hollow drill bit and a 
stylet removably inserted into the hollow drill bit to keep the bore of 
the hollow drill bit unplugged during drilling. The stylet is removed 
after drilling to permit the operator to inject medication through the 
bore of the hollow drill bit. Preferably, the hollow drill bit of the 
present invention is a hypodermic needle having a sharpened point. 
An important feature of the invention is that the stylet is removable from 
the hollow drill bit. After the drilling, the stylet is removed and the 
tip of an injection needle is inserted into the bore of the hollow drill 
bit to dispense the medication through the bore. Another feature of the 
invention is that both the drill bit and stylet are disposable. 
An advantage of the present invention is that it provides a effective 
intraosseous drug delivery system that maximizes the applicability of 
intraosseous injection technique with minimum complications of the device 
for dental and other potential medical applications. This invention 
provides the solution to the problems of intraosseous injection heretofore 
encountered by dentists in dental anesthesia. This invention also provides 
broader applicability of the intraosseous injection technique in dental 
anesthesia and other medication. 
A preferred embodiment of the invention is a medication injection device 
that includes two basic parts: a hollow drill bit and a stylet. The stylet 
fits into the hollow drill bits from the hub end and extends through the 
entire length of the drill bit. The stylet has a enlarged handle on the 
hub end that is grasped to remove the stylet. The stylet prevents the bore 
of the hollow drill bit from plugging up during the drilling operation so 
that medication can be injected through the bore into the surrounding 
tissue after the stylet is removed. 
The hollow drill bit is preferably sized at 27 G (gauge), so it will 
produce only a very small hole in the bone. It causes no significant 
damage to the bone structure. The highly hardened drill bit with its sharp 
cutting angle provides a smooth drilling action, preventing the generation 
of excessive heat. The process of sharpening the needle tip makes the 
diameter of tip portion slightly larger than the tubing portion, so that 
the diameter of the hole produced by the hollow drill bit is slightly 
larger that the diameter of the drill bit. This prevents the drill from 
jamming into the bone. 
The stylet prevents the bore of the hollow drill bit from being plugged 
during the drilling. It also prevents any contamination from the hub side. 
Removing the stylet after drilling provides an easily identified injection 
passage for the injection needle. 
Before this invention, intraosseous injection techniques in dental 
anesthesia encountered major difficulties with both patients and dentists. 
During the early development stage of intraosseous injection, the drill 
bits would cause tremendous bone damage to the patient and create a 
greater chance of inflammation and infection. At a later stage, a special 
drill was developed, but it was difficult for dentists to find the drilled 
hole under the gum tissue. Further, the usefulness of the prior technique 
was generally limited to the front teeth, because the limited space and 
angle made the application to the back teeth much more difficult. The 
present invention has eliminated these problems. The applicable area can 
expands to the whole mouth, and the fine needle drill will not produce 
significant bone damage. 
This invention is not limited to injecting local anesthetics in dental 
applications. The invention is broadly usable for injecting a wide range 
of medications, including antibiotics, and in other medical and veterinary 
applications. 
The features and advantages described in the specification are not all 
inclusive, and particularly, many additional features and advantages will 
be apparent to one of ordinary skill in the art in view of the drawings, 
specification and claims hereof. Moreover, it should be noted that the 
language used in the specification has been principally selected for 
readability and instructional purposes, and may not have been selected to 
delineate or circumscribe the inventive subject matter, resort to the 
claims being necessary to determine such inventive subject matter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 through 14 of the drawings depict various preferred embodiments of 
the present invention for purposes of illustration only. One skilled in 
the art will readily recognize from the following discussion that 
alternative embodiments of the structures and methods illustrated herein 
may be employed without departing from the principles of the invention 
described herein. 
One aspect of the present invention is a medication injection device having 
a hollow drill bit and a stylet removably assembled in the bore of the 
hollow drill bit. The preferred embodiment of the medication injection 
device 10 is shown in FIG. 1. Medication injection device 10 includes a 
hollow drill bit 12 and a removable stylet 14. When assembled, the stylet 
14 is positioned within a bore of the hollow drill bit 12 and has a small 
handle 34 extending rearwardly from the hub end 16 of the hollow drill 
bit. 
The hollow drill bit 12 and the stylet 14 are shown in more detail in FIGS. 
2-5. As shown in FIGS. 2a and 2b, the hollow drill bit 12 has a hollow 
cylindrical hub 18 and a needle 20 extending axially from one end of the 
cylindrical hub. The cylindrical hub 18 has an axial passage 22 
therethrough and a circumferential groove 24 and a longitudinal flat 26 at 
the end opposite the needle 20. The dimensions of the hub 18 and its 
groove 24 and flat 26 are chosen so that the hollow drill bit 12 will mate 
with the spindle of a standard low-speed dental handpiece. The groove 24 
on the end of the hub 18 is the retaining site for the latch on a standard 
low-speed dental handpiece. The end of the hub 18 opposite the needle also 
has a lip 28 that serves as an attachment structure for the stylet 14. The 
cylindrical hub 18 is preferably composed of stainless steel, aluminum or 
plastic. 
The needle 20 is a preferably a 27 G (gauge) hypodermic needle, although 
larger or smaller sizes can also be used. The needle 20 is hollow with a 
bore 30 extending along its axis. The exposed end of the needle 20 is a 
sharpened tip 32. 
As the best shown in FIG. 3, the stylet 14 has a handle portion 34, a 
cylindrical body 36, and a wire 38. The handle 34 is cylindrical with a 
flat that corresponds to the flat 26 of the hollow drill bit 12. The 
handle 34 has a latch 40 that extends around and mates with the groove 26 
and lip 28 of the hub 18 of the hollow drill bit 12. The handle 34 of the 
stylet is preferably made of plastic or stainless steel. The cylindrical 
body 36 of the stylet 14 is preferably made of stainless steel with a 
plastic coating, and has a diameter slightly smaller than the inside 
diameter of the axial passage 22 of the hub. The wire 38 of the stylet 14 
is a straight stainless steel wire that precisely fits into the bore 30 of 
the hypodermic needle 20 of the hollow drill bit 12. 
As shown in FIGS. 4 and 5, the stylet 14 is mounted into the hollow drill 
bit 12 with the wire portion 38 of the stylet passing through the entire 
length of the bore 30 of the hollow drill bit to the sharpened tip 32 of 
the hypodermic needle. The handle 34 of the stylet latches onto the end of 
the hub 18 to secure the stylet to the hollow drill bit. 
In an alternative embodiment, shown in FIG. 10-14, a stylet 50 is designed 
for a tight, friction fit to the bore of a hollow drill bit 52. The handle 
54 of the stylet has a cylindrical shape with a flat, but without a latch 
like the latch 40 of stylet 14. The end of the hub 56 of the hollow drill 
bit 52 opposite the needle 58 has a groove 60 and flat 62, and has a lip 
64 that extends to the radius of the hub. The stylet 50 is secured by the 
tight fit of the middle portion 66 of the stylet to the bore 68 of the hub 
of the hollow drill bit 52. 
A method of using the medication injection device 10 according to the 
present invention will now be described with reference to FIGS. 6-9. The 
hollow drill bit and the stylet are pre-assembled and sterilized and are 
installed into the spindle of a standard low-speed dental handpiece 80. 
The handle 82 of the stylet extends out the backside of the handpiece 80, 
and the needle 84 extends out the front side. A retainer 86 of the 
handpiece 80 latches onto the retains the hollow drill bit. 
Once the medication injection device 10 is installed in the handpiece, the 
device is ready for use. The tip of the needle is positioned at the 
desired location and the handpiece is activated to drill into the subject. 
When the drilling is completed, the handpiece is stopped and the stylet is 
removed by grasping on the handle 82 and pulling the stylet out the 
backside. Removing the stylet opens the bore of the hollow drill bit for 
introduction of medication to the tip of the needle 84. After a hole has 
been drilled and the stylet removed, the operator inserts the hypodermic 
needle tip 88 of a syringe 90 containing the medication into the bore of 
the hub. The operator holds the handpiece to steady the hollow drill bit 
10 during the injection phase. When the injection is complete, the 
operator withdraws the hollow drill bit 10 from the drilled hole by moving 
the handpiece 80. 
Since the hollow drill design of the present invention provides a drug 
delivery passage passing through the covering soft tissue, the invention 
has many advantages over other existing devices. In comparison to the 
rosehead bur or reamer, this device will only drill a hole similar to the 
tiny diameter of a ordinary 27 G needle. Therefore, bone and tissue damage 
are significantly reduced. In comparison to the perforator used in 
Stabident System, the present invention provides a visible drug delivery 
passage on the surface of the soft tissue. Therefore, there is no more 
guessing and trial and error to find a tiny hole into the bone covered by 
soft tissue. Also, if it is necessary, operator may temporarily leave the 
hollow drill bit in position by removing the dental handpiece after 
releasing the retainer. This will allow the operator has the chance to 
dispense the second or more dosages to the same position. 
The application field includes, but is not necessarily limited to, dental, 
medical and veterinary medicine. In order to avoid contamination among 
patients, the drill bit and the stylet are disposable. 
While the invention has been disclosed with reference to drilling holes 
between teeth for applying a dental anesthetic, those skilled in the art 
will recognize that the invention will be useful for any procedure 
requiring the drilling of an opening and the delivery of fluid into 
tissue. From the above description, it will be apparent that the invention 
disclosed herein provides a novel and advantageous medication injection 
device and associated method of use. The foregoing discussion discloses 
and describes merely exemplary methods and embodiments of the present 
invention. As will be understood by those familiar with the art, the 
invention may be embodied in other specific forms without departing from 
the spirit or essential characteristics thereof. Accordingly, the 
disclosure of the present invention is intended to be illustrative, but 
not limiting, of the scope of the invention, which is set forth in the 
following claims.