Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR DRILLING
TEETH WITH A PRESSURIZED WATER JET
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of drilling teeth to remove decayed
enamel or other tooth matter and provide a surface of the proper size and
shape to receive
a dental restorative filling. More specifically, the present invention relates
to a method
and apparatus for drilling teeth with one or more high-pressure water streams
with or
without abrasive materials suspended in the water.
2. Technical Background
According to the American Dental Association survey center, in 1990 alone,
there
was an estimated 151,810,000 dental filling procedures performed in the United
States.
Currently the most widespread and notorious method for removing tooth matter
in a
cavity filling procedure is through a high speed drilling process. Drilling is
often
associated with substantial discomfort and anxiety. Most people find going to
the dentist
and having a cavity filled a very unpleasant and painful experience. Some
people even
develop phobias of visiting the dentist from the accompanying sounds, smells,
and pains
present in a typical drilling process.
A high speed dental drill is a mechanical drill that is driven by an
electrical or
pneumatic power source with a bit at the end. The drill bit is designed to
remove small
pieces of tooth as its rotating head contacts a tooth. This removal method
functions much
in the same manner as does an industrial drill when removing portions of
metals or
ceramics. A dental drill is typically handheld and easy to position in most
areas of the
2~ mouth for removing tooth decay. The drilling process often requires water
to cool the
tooth being drilled and a vacmun to remove the water and tooth debris. The
drilling
process has the advantage of being low cost and well accepted in the dental
field.
Nonetheless, drilling does have many disadvantages in dental applications.
SUBSTITUTE SHEET (RULE 26)
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cutting action of the rotating bit may damage the enamel, which may weal~en
the structure
of the tooth. The process is intrusive for the patient and the size of the
drill bit often
requires the removal of considerable more healthy material than would
otherwise be
necessary.
The patient often experiences discomfort from the grinding and vibrations in
the
vicinity of tooth nerves that may already be stressed due to decay of enamel.
During this
process, the patient hears the constant, high-pitched whine of the drill
motor, which is
associated with pain and discomfort by many people, and may be downright
frightening
for others. To compensate for the pain and discomfort of a drilling procedure,
large
amounts of pain reducer may be required which can lengthen the process as a
result of the
necessity of waiting for the medicine to tale effect. The use of medication
also increases
the cost of the procedure. The result of these problems is that the process of
drilling a
tooth entails several minutes, or even hours, of discomfort and anxiety for
tile patient.
Alternative methods of relnoving decaying tooth matter have been investigated
to
overcome the shortcomings of dental drilling. One such method is air abrasion.
Air
abrasion units use pressurized air to propel and direct small abrasive
particles onto the
tooth resulting in an abrading away of the surface. Air abrasion units are
used quite
effectively for shallow, surface cavities and tend to conserve more of the
healthy tooth
than the high speed drill. Also, because the impact of the abrasive particles
on the tooth
are so minute, vibrations are insignificant and usually pain relief injections
are not
required. This saves time and also increases comfort to the patient. However,
the air
abrasion method is not as time effective when it comes to drilling below the
outer enamel
layer of the tooth and into softer tissues. This is due, in part, because the
softer tissue just
beneath the enamel surface, called dentin, partially absorbs the impact of the
abrasive
particles. The particles tend to bounce off this portion of the tooth,
diminishing the
excavating effects of the abrasive stream.
Another alternative to drilling that has been introduced recently is laser
drilling
and cutting technology. Lasers are the most precise method of removing tooth
matter in
the dental industry. They are capable of penetrating the tooth surface and
underlying
tissues in a highly controlled fashion and with the smallest width of cut of
all of the
presently available methods. Although the use of lasers does produce a heat-
affected zone
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on areas of the tooth adjacent to the cut, several studies have shown that
these effects are
not significant enough to cause permanent damage to the health of the tooth.
Although
the laser offers significant benefit in dental applications, very few dentists
use them. This
is primarily due to the fact that they cost significantly more than
alternative methods.
Also, most dentists are not yet ready to invest in a technology without
lcnowing that it
provides significant improvements over their current method.
In developing a new decay removal method there is a need for an apparatus and
method capable of removing decayed tooth material that is better suited to
preserve a
maximum amount of healthy tooth material. Leaving as much healthy tooth matter
in
place as possible helps to maintain the overall strength of the tooth and
minimize the
chances of cracking the tooth later on. In the case of the high speed drill,
the minimum
cutting dimension is limited by the width of the cutting tool. Relatively
large amounts of
healthy tooth material have to be removed in order to sufficiently reach the
decayed
portions. The air abrasion and laser methods have the ability to make smaller
cuts and are
thus able to conserve much more of the healthy tooth than had previously been
possible.
But, with the more precise cutting abilities also comes a limitation in the
speed of the
process, type of material that can be removed, and the cost of the equipment
required.
Because these methods are able to remove only relatively tiny sections of a
tooth at a
time, they also require more time to remove larger sections of material.
Consequently, there is a need for an improved apparatus and method for
drilling
teeth. The method should be effective for rapidly removing enamel a~ld other
decayed
material with a minimum of discomfort for the patient. Thus, the apparatus
should
preferably operate quietly and with a minimum of appliance that must be
simultaneously
inserted into the patient's mouth. Furthermore, the apparatus should operate
inexpensively, and function with equipment easily integrated with current
dental office
systems. Such a device should be self cooling and accurate, so that healthy
tooth
structure is preserved. Moreover, such a method should minimize pain to the
patient and
should not be psychologically stressful for the patient, for whom the prospect
of going to
the dentist is already distressing enough.
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Summar~of the Invention
The present method and apparatus implements high pressure liquid forced
through
a small orifice, or water jet, to cut and remove decaying tooth matter for
restorative dental
procedures. Water jets are able to cut through many materials much easier than
other
methods without harming the surrounding material. The present apparatus
includes a
pressure source configured to provide a flow of pressurized liquid, such as
water, to an
applicator through a high pressure conduit. The applicator has a first orifice
positioned to
direct a first stream of the liquid against an oral surface, wherein the
velocity of the
stream of liquid ej ected from the orifice is capable of boring into tooth
matter, such as
tooth enamel.
The water jet dental tool may also have an abrasive material suspended within
the
pressurized liquid. The abrasive is typically mixed with a liquid to male a
generally
homogenized slurry. The abrasive material in the slurry may be sized from 1 to
30
microns in diameter and has a volumetric concentration of abrasive in the
range of 3% to
20%. Any number of abrasive materials may be used in the present apparatus and
method. Aluminum oxide, pumice, baling soda, and illminite are abrasives that
are
presently used in the dental field and are also capable of removing a
sufficient amount of
tooth and oral matter when used in a water j et system. The slurry is ej ected
out of the
applicator under high pressure. Typically slurry pressures may range from 250
psi to
17,000 psi and more preferably, from 500 psi to 2,500 psi. Other embodiment
may have
useful slurry pressures below 250 psi, depending on other factors, such as the
slurry and
orifice size.
The orifice in the applicator may have various shapes for different boring
requirements. The orifices in one embodiment are circular, and in another
embodiment
the orifices are elliptical. However, other shapes of orif ces may be
implemented in the
water j et for a large range of dental applications. The orifice size may be
of a range of
0.003 inches (0.076 mm) to 0.008 inches (0.203 ruin). Additionally, the
applicator may
have more than one orifice to direct a stream of water at a tooth and may
further be able to
induce cyclical variations in the liquid pressure.
The present method may also be practiced through other apparatuses by
embodying the present procedure. The process comprises pressurizing a liquid.
The
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pressure can be of any number of ranges depending upon slurry composition. The
pressurized liquid is then conveyed into an applicator. The applicator can
have any
number of orifices of a diameter sufficient to bore into teeth. The applicator
then ejects a
stream of high pressure liquid or slurry from an orifice with a velocity
sufficient to bore
into a tooth.
The operation, features, and advantages of the present apparatus and method
will
become more fully apparent from the following description and appended claims,
or may
be learned by the practice of the invention as set forth hereinafter.
Summary of the Drawings
Figure 1 is a schematic bloclc diagram of a water jet dental tool;
Figure 2 is a schematic block diagram of another possible embodiment of a
water
jet dental tool, with abrasive mixers;
Figure 3 is a cross-sectional view of a slurry applicator;
Figure 4 is a schematic bloclc diagram of another possible embodiment of a
water
jet dental tool, with an abrasive source and an intensifier pump;
Figure 5 is a cross-sectional view of an applicator having a post-ejection
abrasive
mixer;
Figure 6 is an end view of a liquid slurry orifice disk with a round orifice;
Figure 7 is an end view of a liquid slurry orifice disk with an elliptical
orifice; and
Figure 8 is a cross-sectional view of a possible embodiment of an applicator,
with
a first and second orifice.
Detailed Description
The presently preferred embodiments of the present invention will be best
understood by reference to the drawings, wherein like parts are designated by
like
numerals throughout. It will be readily understood that the components of the
present
invention, as generally described and illustrated in the figures herein, may
be arranged and
designed in a wide variety of different configurations. Thus, the following
more detailed
description of the embodiments of the apparatus, system, and method of the
present
invention, as represented in Figures 1 through 8, is not intended to limit the
scope of the
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invention, as claimed, but is merely representative of presently preferred
embodiments of
the invention.
Referring to Figure l, a water j et dental tool 10 is depicted as having a
pressurized
liquid source 12 and a liquid stream applicator 16. The pressurized liquid
source 12 and
the applicator 16 axe operably connected, such that the applicator 16 receives
a high
pressure liquid from the pressure source 12. The pressurized liquid source may
be a high
pressure liquid pump or other pressure creation device, such as a pressurized
tank of gas,
a weighted piston, or a compressed flexible bladder. The pressurized liquid
source 12 and
the applicator 16 may be connected by any liquid transferring device capable
of
withstanding high pressures. High pressure hosing, drilled sections of blocl~,
or any other
life high pressure conduits 20 may be employed in the present system 10. Once
the high
pressure liquid reaches the applicator 16, it is ejected from the water jet 10
through an
orifice 24, having a diameter that is smaller than the diameter of the high
pressure conduit
20.
The constant volumetric flow rate of such a nozzle system converts the high
pressure liquid into a high velocity liquid as it passes though the orifice.
The fine stream
of liquid 28 is directed by the applicator 16 at the desired oral matter, such
as a tooth 32,
as depicted in Figure 1. The high velocity liquid stream 28 impacts the
surface of the
tooth, causing the water to decelerate. The deceleration of the liquid stream
28 produces
a reaction force in the tooth 32 in a direction toward the tooth 32 and in the
same
direction of the liquid stream 28. Because a force equals a mass multiplied by
an
acceleration, the deceleration of the liquid multiplied by the mass of the
liquid impacting
the tooth 32 produces a force on the tooth 32 sufficient to remove tooth
matter. Figure 1
depicts a possible tooth decay removal procedure. However, this water j et
dental tool 10
is also capable of removing healthy tooth matter, such as in smoothing out
chips, or
removing soft oral matter, such as in a root canal procedure. A water jet
dental tool 10
can be used in many of the same applications as a conventional drill.
Various embodiments of the dental tool depicted in Figure 1 exist. For
example,
Figure 2 demonstrates a water j et wherein the liquid is combined with an
abrasive to
create an abrasive slurry. A slurry is a mixture of a liquid, often water, and
any of several
finely divided particle substances. The slurry travels though the water jet
system in the
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same manner as a liquid, but it additionally provides an abrasive to
facilitate removal of
tooth matter or other similar substaxlces. Tn an oral environment, the
particles selected to
mix with the liquid must be selected with consideration of applicable health
standards.
Abrasive materials, such as aluminum oxide, that are already used in dental
applications
are preferable because the material has already been approved by the United
State Food
and Drug Admiustration for dental applications. Other abrasive materials such
as
pumice, baking soda, and illminite are also safe in oral enviromnents and can
be used in
tooth matter removal. In addition to being safe, the abrasives must also have
other
important physical properties, such as particle size, volumetric
concentration, hardness,
and insolubility.
Particle size of the slurry abrasive material is a factor in determining and
controlling the amount of material removed by the liquid stream. In one
embodiment for
removing decaying tooth matter, the abrasive particle size is preferably in
the range of 1
to 30 microns. The particle size is typically classified based on the size of
screen or filter
through which the material passes. Reference in tlus section or in other
sections to
particle size should be not be construed to limit an abrasive to any one
particle size. For
example, a quantity of 20 micron ahuninum oxide may include a certain
percentage of
particles that are larger or smaller than 20 microns, as typically occurs in a
screening
process. Rather, a quantity of 20 micron aluminum oxide will be made
substantially, not
entirely, of 20 micron particles. Further, other materials may be present in a
slurry
besides a liquid and abrasive particles. For example, various types of pain
reducers or
cleaning materials may be within the slurry to provide a wide variety of
applications and
types of slurry. Also, various materials to aid in suspending the abrasive
particle in the
slurry may be used.
In a preferred embodiment, the liquid in the slurry has a 4% to 17% volumetric
concentration of abrasive. This preferred range allows for the slurry to
generally remain a
liquid, while also containing an adequate amount of abrasive for cutting. A
correct ratio
of abrasive to liquid allows for optimal functions of a water jet. The slurry
should remain
substantially liquid to allow for pressurization of the liquid in a pump,
pressure
intensifier, or other pressure source. However it is also desirable, for
safety and power
generation reasons, to have the system operate at a low range of pressures.
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While the volumetric concentration range of 4% to 17% is preferred for one
embodiment, other ranges are within the scope of this disclosure. For example,
the
present apparatus is capable of removing oral matter without the use of an
abrasive. This
may be used in situations with lughly decayed tooth or with treatment of gums.
Higher
S concentrations of abrasives may also be used with this water jet system, but
attention
must be paid to prevent the slurry from becoming a sludge. Additionally,
higher
concentrations of abrasive can create a messy residue around the work area. A
volumetric
concentration of 17% provides a good mixture for efficient cutting, but it
leaves a residue
of spray around the work area from abrasive particles. A mixture at 11%
volumetric
concentration is substantially cleaner than a higher concentration of
abrasive, but does not
cut as effectively as with 17% abrasive. Thus, the particular environment and
application
should be considered when selecting a volumetric concentration of abrasive in
the
pressurized liquid.
Presently, water is a preferred liquid for the slurry because of its safety
and
1 S availability. However, other liquids may be used so long as they are able
to create a
pressure and are able to suspend an abrasive. Such liquids may have some
desirable traits
that are absent in water. Water is an excellent solvent, which limits the
number of types
of abrasives that can be used in water jet. For example, baking soda can be
used in a
water jet application, but it dissolves in the water, thus limiting its
abrasive features.
Additionally, it can be difficult to keep such an abrasive homogenous
throughout the
system. Keeping a slurry homogenous is helpful in calibrating and timing the
duration for
exposing the tooth to a high pressure stream of slurry. A liquid, other than
water, in
which abrasives have lower solubility may be used in the water jet.
Referring back to Figure 2, this embodiment depicts a system having two
possible
2S devices and locations for mixing a slurry in a water jet dental tool 40.
The system has a
pump or other pressure source 44 that receives a liquid from a liquid source
48. An
abrasive mixer S0, S2 may be located on either side of the pump. The system
need not
have both mixers S0, S2, but will typically have one or the other. The mixer
SO on the
upstream side of pump 44, receives a measure of abrasive from the abrasive
feeder S6
based upon the volume of liquid flowing through the system. The upstream mixer
SO
receives both the liquid and the abrasive to combine them to create a slurry
of proper
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concentrations. The slurry then enters the pump where it is pressurized to a
high pressure.
Once the slurry is pressurized, it flows through the high pressure conduit 60.
The slurry
enters the applicator 64 where it is directed at the material to be cut.
However, there are
some drawbaclcs to this embodiment. The slurry being pressurized in the pump
can cause
significant wear of the pump components, causing the pump to lealc or fail.
To avoid this damage, the abrasive may be added to the pressurized liquid by a
downstream mixer 52. For this abrasive mixing process, the abrasive should be
either in
a single batch form or should be injected intermittently as a slurry into the
pressurized
liquid at a higher differential pressure stream. For a single batch inj ection
procedure, the
batch is generally fed into the system in quantities suited for limited boring
time and
depth. But, because dental restorative work typically only involves a few
dental boring
procedures per visit, the downstream mixer configuration is well suited for
dental
procedures. Alternatively, lower pressure embodiments may be able to
adequately add an
abrasive downstream of the pressure source without any additional
modifications or
operations. h~ a further embodiment, the system may not mix an abrasive with a
liquid at
all, but may simply rely upon an abrasive free liquid for the cutting
functions.
The advantages and disadvantages of each abrasive inj ection method must be
considered in selecting a design for an application. Presently, locating the
mixer 52
downstream of the pump or other pressure source is preferred to maintain the
life of the
pump or pressure source. A batch of abrasive may be loaded into the abrasive
feeder to
provide a fixed amount of abrasive for multiple oral procedures. However, a
pump
capable of pressurizing a slurry with minimal wear to the system would be
preferable.
Regardless of where the slurry is mixed, the mixture enters into the
applicator 64
as a slurry and exits the orifice 68. Figure 3 depicts a cross-sectional view
of the
applicator 64 of Figure 2. A tube or channel 72 is present in the body 76 of
the applicator
and is capable of sustaining a high pressure, such as is present in a water
jet system. The
channel 72 is shown as having a slurry running through it, as is represented
by the
particles 80 in the liquid 84. The slurry mixture travels through the channel
72 and into
nozzle 88 coupled to the end of the chamlel 72. The nozzle 88 has a collet 92
that
supports an orifice 96. The slurry is forced through the small orifice 96 by
the internal
pressure of the mixture. The dynamics of the relationship of pressure to
velocity of the
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slurry can be best related by Bernoulli's equation. Bernoulli's equation
relates liquid
pressure, velocity, density, and elevation for two points in a fluid system
with a constant
flow rate. In the water j et, the volume of the liquid entering the system is
equal to the
volume of water exiting the orifice 96, because there are no other liquid
inputs and output
sources. For this reason Bernoulli's equation is appropriate for water j et
calculations. In
the equations below, the first measurement is taken at a pressurized point in
the system
and the second measurement is taken just after the liquid exits the orifice.
The equation
states:
.P1 ~12 p2 ~22
P + ~ + gz~ = P + ~ + gzz
Wherein:
P~ - Pressure of liquid inside
the system;
PZ - Pressure of liquid exiting
the orifice;
Pl - Velocity of liquid inside
the system;
h2 - Velocity of liquid exiting
the orifice;
p - The density of the liquid;
g - Gravity;
z1 - Elevation of liquid inside the system; and
z2 - Elevation of liquid exiting the orifice.
This equation allows for a water jet system to be characterized according to
the
various design parameters. The significant factors in dental water jet
applications are the
exit velocity of the liquid stream, applicator distance from the tooth, the
internal pressure
of the liquid, size of the stream, and the density of the liquid. For example,
if an exit
velocity is known, then the above equationsmay be used to solve for the
internal pressure
required to obtain the known exit velocity. This may be useful where a dentist
understands the relationship between the cutting velocity to the cutting depth
of the slurry
stream. However, to simplify in calculating the pressure, several assumptions
can and
should be made. First, there is an assumption of minimal frictional losses as
the liquid
travels through the system. While, frictional losses do occur, neglecting
these losses
presents only a small degree of inaccuracy while greatly simplify the
calculations.
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Second, the pressure as the liquid exits the nozzle is assumed to be at
atmospheric
pressure (about 14.7 psi). Pressures at the exit location of the liquid may
actually vary
slightly, but not significantly. Third, the elevation change between the first
point and the
second point are assumed to be miumal when compared to the pressures
difference of the
two pressures. And finally, the first velocity in the water rnay be assumed to
be zero when
compared to the exit velocity at the second point. If these assumptions are
followed and
the equation is solved for the internal pressure of the water:
2
Pz = p ~2 + Pl
The equation states that to obtain a velocity of 100 inches per second to 1000
inches per second the pressure in the system should be approximately 200 psi
to 18,000
psi respectively. Thus, the exit velocity can be scaled to an associated
pressure for
calibration purposes. In the embodiment depicted in Figure 2 and Figure 3, the
preferred
operational pressures are between 250 psi and 17,000 psi. The optimum pressure
ranges
may vary depending on the preferred abrasive type, volumetric concentration,
orifice size,
liquid type, and other factors. Other pressure ranges may be preferable when
different
values and materials are used. For example, the present system may operate at
a generally
low pressure for specific applications wherein the abrasive has larger sizes
and higher
concentration. Such an embodiment would be covered within the scope of the
present
water jet dental tool.
While the pressure range of 250 psi to 17,000 psi is preferred for the present
system, the water jet is most practically operated at a range of 500 psi to
2,500 with the
currently preferred slurry characteristics, the presently preferred slurry
being an 20 micro
aluminum oxidelwater slurry having a volumetric concentration of 11 % This
pressure
range provides for controlled boring of a tooth, low-cost equipment, and safer
operation.
As is intuitive, the higher the liquid pressure, the faster the stream will
bore a hole in the
tooth. Thus to allow for optimal control of a boring procedure, a lower
pressure should
be maintained. Use of a lower pressure, will require less expensive equipment.
The cost
of high pressure pumps, valves, and hosing may limit the cost feasibility of a
water jet
dental tool. low pressure operation may allow the machine to remain
affordable. Further,
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low pressure ranges are safer than higher pressure ranges because less energy
is stored in
the liquid. An alternative embodiment may implement both high and low
pressures
during a single procedure. The system may be configured to oscillate the
pressure of the
fluid, which in tum oscillates the velocity of the fluid exiting the orifice.
The oscillating
device may be a pump capable of producing pressure spires in the fluid, or a
valve that
cuts the fluid flow at various intervals.
Returning to bacr to the figures, Figure 4 depicts an alternative embodiment
of a
water jet system having a post-ejection abrasive mixer. Similar to the system
of Figure 2,
the water jet has a low pressure liquid source 104 that feeds the liquid into
an intensifier
pump 108 that pressurizes the liquid. A typical intensifier pump 108 may
comprise of
two cylinders aligned end-to-end, one cylinder large and one cylinder small.
The pump
108 uses the simple principle of pressure equals force divided by area. As the
area
decreases the resulting force increases. Thus, as a large piston forces a
liquid into the
small cylinder, the pressure increases proportional to the difference between
the two
cylinder areas. While the pressure does increase, the system sacrifices flow
rate of the
liquid. However, because water jets require low flow rates, an intensifier
pump is well
suited for a water j et dental tool. The piston in the intensifier pump 108
may be driven by
a hydraulic 112 or pnemnatic pump, which in turn pressurizes the liquid. Once
the liquid
is pressurized, it travels through a high pressure conduit 116 and is directed
though the
applicator 120. The applicator 120 receives an abrasive from an abrasive
source 124.
The abrasive is mixed with the liquid in the applicator and the resulting
slurry is ejected
toward a tooth or other oral matter.
Tlhe applicator I20 in the present water jet dental tool may be handheld,
similar to
a dental drill type device. Tlus allows for flexibility of use of the tool in
a manner that a
dentist would be familiar. Alternatively, the applicator may be attached to a
positioning
device placed in a location over the patient's mouth and the water jet stream
may be set in
different operating locations by a flexible arm or other positioning device.
In another
embodiment, the j et may be placed above the patient at a fixed position and
the patient's
head may be adjusted to receive a stream at the desired tooth location. In
another
embodiment, the location that the liquid stream will impact a tooth can be
calibrated to
aid the dentist in positioning the applicator 120. The applicator 120 may be
equipped
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with a stylus to indicate the stream impact location. Alternatively, the
applicator may
have a light or a laser that indicates the bore location. Other embodiments of
the present
applicator 120 may exist that are consistent with the purpose and function of
the present
disclosure.
Figure 5 depicts a cross-section of the applicator having a post-ejection
abrasive
mixer. As with similar applicators, the liquid 140 travels through the channel
144 of the
applicator 120. The channel 144 is fixed within the body 148 of the applicator
and is
shown within Figure 5 as being a hose type conduit. The liquid 140 does not
have any
abrasive suspended within as it enters the nozzle 152. The nozzle in Figure 5
is generally
the same as the nozzle 64 in Figure 3. The liquid enters the nozzle 152 and is
forced out
the orifice 156 in the orifice dish 160 at high speeds. At the point of
ejection, no
abrasives are present in the stream 164. In the embodiment of Figure 5, the
abrasive 168
is mixed with the high pressure stream 164 in a refocusing nozzle 172 after it
leaves the
orifice 156. The abrasive 168 is drawn through an abrasive feeding tube 176
and into the
refocusing nozzle 172 by a vacuum created by the exiting liquid stream. Once
the
abrasive enters the refocusing nozzle 172, it is mixed with the liquid steam
164 to form a
slurry. The liquid steam 164 is once again refocused into a fine stream by the
tapered
section of refocusing nozzle and ejected to the worlcing area 178.
The water jet removal tool, as depicted in Figure 3 and Figure 5, has a collet
92,
158 supporting an orifice dish 96, 160 respectively from which the slurry is
ejected.
Figure 6 is a view of an orifice dish 180 held within a collet 182 have a
round orifice 184.
The round orifice 184 allows for a focused stream of slurry on a point of a
tooth. The
collet may have a threaded portion to be removably attached to a nozzle so
that the orifice
dish may be easily replaced without replacing the entire collet and nozzle
assembly.
Figure 7 depicts an alternative embodiment of an orifice dis1~190 having an
elliptical
orifice 194. The elliptical orifice 194 allows for removal of a rectangular
area of decayed
tooth or other oral matter. This shaped orifice provides the ability to create
wide and
shallow bores in a tooth. However, other shapes of orifices may be implemented
in the
water jet for a large range of dental applications. Additionally, the orifice
in the orifice
dish may further have a tapered exit wherein the stream diameter spreads out
as it exits
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WO 02/15810 PCT/USO1/26364
the orifice. Various degrees of taper can be used to obtain multiple stream
and spray
characteristics.
These orifice disks 180, 190 are typically made of a material that is not
easily
worn down by the abrasives, such as sapphire or diamond. The orifice size and
shape is
also an important design element of the water jet dental tool. The size of the
exit orifice
determines the amount of slurry ejected and the diameter of the cut in the
tooth. A
preferred embodiment is sized in the range of 0.003 inches (0.076 mm) to 0.008
inches
(0.203 mm). However, other sizes for various applications will be known to one
ordinarily skilled in the art. The small orifice also has a throttling effect
on the liquid as it
exits the nozzle. A throttling effect occurs as the size of the orifice is
changed during a
constant flow process according to the equations:
v~A~ = v2A2
Wherein:
Yl - Velocity of liquid inside the system;
h2 - Velocity of liquid exiting the orifice;
A1 - Cross-sectional area of the tube;
AZ - Cross-sectional area of the orifice;
While this equation demonstrates that the liquid will have a higher velocity
as it exits the
orifice, the effects of the throttling are generally nominal compared to the
large pressure
in the system. However, the throttle effect may have a noticeable effect on
water j et
systems when the pressures are lower.
Figure 8 depicts an orifice disk 200 having a first orifice 204 and a second
orifice
208. The orifices 204, 208 can be slightly angled so that the two streams 212,
216 merge
at one location on the tooth to increase the speed tooth matter is removed or
to change the
shape of the bore. Other embodiments may have more than two orifices depending
upon
the application.
The present water jet dental tool has a plurality of applications and
variations that
may be practiced as part of this disclosure. The method disclosed for removing
tooth
material using a water j et may perform many of the following steps, but may
include
alternative parameter ranges. First, a liquid is pressurized. A typical
pressure is from 250
psi to 17,000 psi, but preferably from 500 psi to 2,500 psi. The pressurized
liquid is then
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WO 02/15810 PCT/USO1/26364
conveyed to an applicator and ejected out an orifice at a velocity sufficient
to bore a hole
in a tooth. The orifice may be of the range of 0.003 inches (0.076 mm) to
0.008 inches
(0.203 mm). The method may also include a step of mixing an abrasive in the
liquid so
that abrasive is suspended in a slurry. One currently preferred abrasive is a
slurry with a
4% to 20% volumetric concentration of abrasive aluminum oxide. The abrasive
may have
a size in the range from 4 to 27 microns.
The present invention may be embodied in other specific forms without
departing
from its structures, methods, or other essential characteristics as broadly
described herein
and claimed hereinafter. The present apparatus and system may be used in other
applications as would be known to one spilled in the art, such as bone and
finger nail
etching. The described embodiments are to be considered in all respects only
as
illustrative, and not restrictive. The scope of the invention is, therefore,
indicated by the
appended claims, rather than by the foregoing description. All changes that
come within
the meaning and range of equivalency of the claims are to be embraced within
their scope.
