Good Vibrations: Blocking Dental Injection Pain
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Dr. Steven G. Goldberg
Thu, 2014-03-06 15:01
Millions of Americans stay out the dentist's office to avoid pain, but a new innovation could potentially render
this concern moot.
According to studies from the Dental Fears Research Clinic at the University of Washington Dental School and
the Columbia University School of Dentistry, upwards of 50 million Americans avoid the dentist due to their
fear of pain.
These statistics are alarming when you consider the consequences of pervasive dental neglect. Poor oral health
leads to bleeding, infected gums, and decaying, broken-down teeth. Also, inadequate dental care contributes to
a decline in overall health. Studies show that inflamed and infected gums can cause diabetes, pre-term delivery
and low-birth-weight babies, stroke, cardiovascular disease, and even bacterial endocarditis (which can be
deadly). Ignoring oral issues now can lead to a host of other severe health concerns later on.
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In truth, the most painful part of the entire dental appointment comes at the
very start of any given procedure: the dreaded intra-oral anesthetic
injection. This has presented a challenge for more than 150 years—but one
that’s unavoidable. The only method for anesthetizing a tooth is to deliver a
local anesthetic by a needle through the oral tissues; nothing else will reach
and anesthetize the nerves of the teeth and gums.
Topical anesthetic gels are used by a majority of dentists when delivering
local anesthetic injections. Unfortunately, topical gels numb only the tissue
surface. Higher-percentage gels may provide more profound numbness.
Care must be taken when using these gels, however, as a small percentage of
the population is allergic to the benzocaine contained within them. Also,
higher- percentage gels can cause a burning or sloughing of the oral tissue. Furthermore, some patients with a
rapid or irregular heartbeat may be negatively affected by the use of these gels.
The dental community is well aware of the need for
dentists to provide pain-free dentistry. Numerous
articles have recently been written advising dentists to
provide a more comfortable experience for their
patients. Dental Products Report recently published
articles specifically on dental injection pain, stating,
“This doesn’t have to hurt,” and “No pain, plenty to
gain.”
DentalVibe is a patented, award-winning clinical
instrument that eliminates intra-oral injection pain. It
is a cordless, AA-rechargeable-battery operated,
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handheld device similar in size and shape to an
over-the-counter battery operated toothbrush (Fig. 1). Its vibrating tip simultaneously delivers soothing,
pulsed, percussive micro-oscillations to the site where an injection is being administered.
DentalVibe uses proprietary VibraPulse pain-blocking technology, which causes the tips placed on the oral
mucosa to vibrate at a specific frequency and amplitude gently stimulating the sensory nerve receptors at the
injection site (Fig. 2). This controlled, forced wave pattern is pulsed so that it effectively maintains a closure of
the neural pain gate, thus blocking the pain of injections. The result is a redefinition of the injection process.
DentalVibe operates on the merits of the Gate Control Theory of Pain, first proposed and documented in the
journal Science by Drs. Ronald Melzack and Patrick Wall back in 1965. This theory holds that there is a
neurological “gate” located within the spinal cord—in this case, within the trigeminal ganglion—that can either
block pain signals or permit them to travel to the brain. When a counter-stimulation (in this case, vibration) is
applied during a painful occurrence (e.g., a dental injection), the sensation of vibration reaches the sensory area
of the brain first, resulting in a closure of the pain gate to the sensation of pain.
The DentalVibe hand piece weighs 3 oz. and is ergonomically designed to fit comfortably in the hand of a
clinician. Finished off with a series of strategically placed finger grips, this specific design facilitates comfort and
control for use in all areas of the mouth.
Understanding the science of the Gate Control Theory was essential to the development of a vibrating device
that acts as a counter-stimulation to alleviate injection pain. More specifically, the sensory receptors within the
oral mucosa called mechanoreceptors react to physical forces that sufficiently move them, creating action
potentials (electrical impulses) that travel along specific sensory nerve fibers up the spinal cord and on to the
brain. It is here in the somatosensory cortex area of the brain that both vibration and pain are recognized.
When both occur at the same time, the sensation of vibration travels to the brain much faster than the sensation
of pain.
Because vibration beats the injection pain to the brain, a neurological
blocking mechanism in a synapse within the spinal cord is activated and a
gating mechanism is closed, not allowing the pain signal to pass through
and make its way to the brain. The result: Pain is not felt when a counterstimulation is simultaneously applied to the injection site.
In developing a vibrating hand piece to be used as a counter-stimulation
by a dental clinician for a period of 1-2 full minutes per patient, there was
a concern that the vibration itself may be uncomfortable in the clinician’s
hand. Therefore, vibration needed to be generated at the very tip of the
instrument while the handle itself remained steady during use.
The Comfort Tip is a three-part assembly consisting of two hard plastic parts with an over-molded, soft,
non-latex elastomeric, which ties the two pieces together and is comforting to the oral tissues while in use (Fig.
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3). The forked end of the tip is curved with an angulation similar to a standard dental mirror, which aids the
dentist in retraction of the lip and cheek while administering intra-oral injections. This forked end is able to
vibrate relative to the fixed, attached portion, known as the tip sleeve. The tip is easily attached by sliding and
snapping it into place on the hand piece (Fig. 4).
To remove the tip after use, the tip sleeve itself is rotated counter-clockwise 180 deg. while the forked end stays
securely in place (Fig. 4). This causes the rubber over-mold to stretch and tear at the connection point between
the two, rendering the tip unusable, thereby preventing cross-contamination.
A common practice by dentists is to shake the lip and cheek of a patient to distract them while administering an
injection (Fig. 5). With the use of the DentalVibe, the Comfort Tip takes the place of the dentists non-injecting
hand and fingers, keeping them out of harm’s way from the needle.
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To create vibration, a standard eccentric-rotating-mass (ERM) vibration motor with an offset attached to the
motor shaft would not suffice . Instead it was necessary to generate the specific frequency and amplitude with
the specially designed Comfort Tip. According to the Gate Control Theory, this sufficiently stimulates the
sensory mechanoreceptors in the tissue without causing discomfort to the patient.
In addition, a light output was necessary to “light up” the injection site
within the oral cavity (Fig. 6). This posed a challenge because a vibrating
bulb could potentially come loose with use over a period of time. To
accomplish these requirements and force this specific frequency and
amplitude, the hand piece features a motor-driven eccentric cam, offset in
the center that co-acts with a rocker at the base of a clear light pipe.
This single part, the light pipe, serves a dual function. First, on one end of
the light pipe is a cam follower, which rides inside the eccentric cam and
delivers vibration to the other end of the pipe. Second, the main shaft of the
light pipe is solid and clear, permitting light to shine through the pipe from
a bright LED that is situated within the handpiece. The light then projects
through a lens built into the forked Comfort Tip and shines onto the
injection site, facilitating greater visibility upon clinical application.
Although the device was designed in SolidWorks, the development of
the light pipe created an engineering challenge. Ray-tracing software
designed to model light transmission made it possible to optimize light
output in the light pipe’s final design, providing the direction necessary
to illuminate the intended injection site.
The DentalVibe can be used throughout the workday in a dental
practice. Its cycle time is approximately 90 seconds on, followed by a
return to the charging base for 15 to 30 minutes before being used
again. The battery choice was an important design decision in order to avoid a memory issue creeping up over
time. The device is powered by a rechargeable, nickel-metal-hydride battery, safe for the environment and free
from memory concerns.
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Because the device is utilized in a dental operatory setting within a wet
environment, the base of the hand piece is sealed to prevent any fluid
seepage into the unit (Fig. 7). Accordingly, an inductive charging base was
developed for recharging the unit with an induction coil to create an
alternating electromagnetic field from within the charging base station. A
second induction coil in the hand piece takes the power from the
electromagnetic field and converts it back into electrical current to charge
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the battery.
Because frequency and amplitude are the keys to the effectiveness of the
DentalVibe, a custom-designed laser Interferometer is used during quality
control testing to evaluate the appropriate range of vibration, frequency,
and amplitude generated at the Comfort Tip (Fig. 8). The device was designed to be patient friendly and to look
like a vibrating toothbrush. For pediatric patients, soft and pliable finger puppets are even available.
DentalVibe is currently used by thousands of dentists throughout the US and in more than 25 countries around
the world, alleviating the last remaining source of significant dental pain: intra-oral anesthetic injections.
Dr. Steven G. Goldberg, DDS, FADFE, is the creator of DentalVibe and a practicing dentist in Boca Raton, Fla.
He is also a Fellow in the International Academy for Dental Facial Esthetics.
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