Note: Descriptions are shown in the official language in which they were submitted.
13141~9
Descr~tion
DENTAL HYGIE~E DEVICE
Technical Field
This invention relates to dental hygiene devices.
Specifically, the invention relates to a method and appara-
tus for cleaning soft, non-calcified bacterial plaque from
the teeth and gingival areas at home on a substantially
daily basis.
Backqround Art
The presence of periodontal diseases in a signi-
ficant portion of the population has indicated a need for
methods and devices to prevent the formation of bacterial
plaque colonies in the periodontal areas. It is well
established that plaque bacteria are the primary cause of
periodontal diseases. Various devices have been made
available to professional dentists and periodontists to
periodically remove tartar or calculus (largely calcified
plaque deposits) from the teeth at regular intervals~ In
addition to passive instruments for scraping this calcified
material from the roots of the teeth, devices employing
sonic energy at hi~h levels to remove calculus are also
available. These devices typically employ high enerqy
levels at ultrasonic frequencies to impart substantial
energy to the hardened plaque (calculus~ to disrupt it.
Thus, these devices serve to destroy calcified plaque
colonies after they have formed rigid structures.
These devices are unsuitable for daily home use
due to the high energy levels which a~e transferred to the
teeth. In the hands of a non-professional, such devices
can cause severe damage to the teeth and surrounding soft
tissues. While applying high~energy levels to the teeth
and subgingival areas at relatively extended intervals
2 13141~9
between applications destroys existing rigid calcified
structures, lt does not prevent the formation of these
calcified ~tructures. It is ~nown that bacterial pla~ue,
over time, undergoes a multilayer building process, involv-
S ing the sequential addition of more and more differentspecies of orqanisms to the plaque mass. It is the later
stages of plaque development, and the later species of
bacteria, that are believed to be the most important in the
etiology o~ periodontal diseases. Certain gram-negative
bacteria and spirochetes are believed likely to be of
greatest importance. Thus, the presently available devices
are not suitable for daily home use and do not disrupt the
multilayer building process in the formation s~age to
prevent periodontal diseases.
Furthermore, these devices cannot prevent perio-
dontal disease even if used on a regular basis. This is
because the energy levels associated with these devices
would be disruptive to the tooth and gum structure if so
used in an attempt to destroy plaque colonies before they
mature to the complex later stages and before the process
of calcification has occurred.
Disclosure of Invention
The present invention allows the daily applica-
tion of sonic energy to the teeth and subgingival areas sothat plaque may be disrupted and destroyed before matura-
tion to the complex pathologic state and before calcifi-
cation has occurred. The normal flushing action of the
mouth and gingival crevices will remove the destroyed or
demobilized bacteria from the gingival areas, thus effec-
tively preventing, or stopping, periodontal disease and
substantially reducing the need for scaling of hard
calculus by dental professionals.
The invention achieves this objective by utili2-
ing a piezoelectric, multimorph transducer which is causedto vibrate at its resonant frequency or multiples thereof.
These frequencies are in the subaudio range to provide ~or
3 131~1~9
the disruption and removal of plaque and for interrupting
and limiting the process of plaque maturation and develop-
ment at energy levels which are harmless to the surrounding
soft tissues. Thus the device may be used at home on a
substantially daily basis to prevent the development of
pathogenic bacterial flora and the formation of hardened
plaque tcalculus) which, when formed, requires removal by
professional dental personnel using high energy devices or
scaling.
The transducer is mounted on a non-conducting
handle in a cantilevered fashion. That is, one end of the
transducer is firmly attached to the handle while the un-
attached end is free ~o vibrate. Thus the transducer forms
an oscillator having maximum displacement at the free end
of the transducer. In one embodiment, the transducer is
driven by appropriate means at the transducer's resonant
frequency. The transducer has a substantially rectangular
shape, wherein the length of the transducer is substan-
tially greater than the width and the thickness of the
transducer is substantially less than the width. Thus the
resonant frequency of the transducer is substantially
determined by the geometry thereof.
An applicator member (in one embodiment, a brush)
is fixed to the ~ree end of the transducer and extends from
the transducer to scrub exposed surace~ of the teeth and
to transmit the vibrations of the transducer to the subgin-
gival axeas. Mild cavitation is caused within the subgin-
gival fluids and has been found to disrupt adherent plaque
colonies and to demobilize motile bacteria without harming
the surrounding soft tissue.
Means for generating a high-voltage, sonic fre-
quency signal for transmission to the transducer are
included to drive the transducer at its resonant frequency
or at mult;ples of the resonant frequency.
In one embodiment, the transducer is electrically
insulated by a flexible covering, protecting the user from
electrical shock. An isolated power drive unit further
4 131~159
isolates the user from low-~requency, high-current signals
which are known to cause physiological stimulation. The
power drive unit is constructed so that the driving signal
is embedded in an amplitude-modulated, high-frequency
carrier wave, so that if a short occurs or if there are
imperfections in the isolated supply, allowing some current
leakage between the user and the powe~ drive unit, only
high-frequency power will be transferred to the user, which
does not induce physiological stimulation.
In another embodiment, the transducer is
s~rrounded by a hood at least longitudinally coextensive
with the transducer and spaced sufficiently apart from the
transducer to allow the transducer to vibrate freely within
the hood. The hood has an open side to allow vibrations to
be transferred from the transducer in the direction of the
open side. Thus, when the device is used in the mouth,
vibrations from the transducer will only be transferred in
one direction, shielding the transducer ~rom vibration
dampening contact with the chqek and other oral tissues. A
flexible protective covering or fluid-exclusion sheath
surrounds the hood and the exposed surface of the trans-
ducer to prevent fluid from entering the space between the-
transducer and the hood. The sheath is bonded to the trans-
ducer along the exposed surface of the transducer. An
applicator is attached to the outward side of the sheath,
proximal to the free end of the transducer, and extends
therefrom to transfer the vibrations from the transducer to
the teeth and gingival areas.
The transducer itself has at least two layers of
piezoelectric material having opposite polarity, bonded to
an intermediate conducting layer. Means for applying an
electrical signal to the unbonded surfaces of the piezoelec-
tric layers are provided so that the transducer may bend in
response to an electrical signal.
The applicator serves to co~ple the vibrations of
the transducer to the gingival and subgingival fluid so
that mild cavitation can be caused within the fluid to
131~1~9
destroy and demobilize motile plaque bacteria. ~he appli-
cator can be a brush having a plurality of bristles sized
to enter the subgingival crevices and pockets to contact
the fluid therein. The shape of the bristles can be varied
to provide penetration into the gingival crevices and
pockets. In one embodiment, the applicator is a second
piezoelectric, mùltimorph transducer attached to and extend-
ing from the ~urface of the first transducer so that vibra-
tion will be produced in two directions. Furthermore, the
transducer applicator may be attached to different surfaces
of the first transducer so that in different embodiments,
the transducer applicators will vibrate orthogonally
compared to each other~
In another embodiment~ one or more transducers
are used. The transducers are mounted perpendicularly to
the longitudinal axis of the handle, and serve as the appli-
cators. In this embodiment the applicators are constructed
from a resilient polymer material exhibiting piezoelectric
characteristics. The transducer applicators may have
various pointed or reduced end shapes for coupling sonic
energy to the teeth and subgingival fluid.
In a further embodiment, the transducer is remov-
ably attached to the handle, providing a dental hygiene
device having a replaceable transducer.
Brief Description of the Drawinqs
Figure 1 is an isometric view of a dental hygiene
device of the present invention and a power drive uni~
therefor.
Figure 2 is a diagram of the device of Figure 1
shown in use.
Figure 3 is an enlarged scale, sectional side
elevational view taken substantially along the line 3-3 of
~igure 1.
Figure 4 is a schematic drawing and circuit
diagram of the device and power drive unit of Figure 1.
, . . . .
- - ~
6 131~159
Figure 5 is a fragmentary side elevational view
of a piezoelectric biomorph transducer used in the device
of Figure 1.
Figure ~ is a fragmentary side elevational view
of an alternative piezoelectric bimorph transducer includ-
ing a spring.
Figure 7 is a fragmentary sectional side view of
an alternative embodiment of the invention having a plural-
ity of transducers extending perpendicularly from the longi-
tudinal axis of the handle.
Figure 8 is an isometric view of another alterna-
tive embodiment of the invention having an applicator
extending perpendicularly to the direction of vibrati~n.
Figure 9 is a fragmentary isometric view of yet
another alternative embodiment of the invention having a
transducer with a hood.
Figure 10 is an enlarged scale, fragmentary
sectional side elevational view taken substantially along
the line 10-10 of Figure 9 with the addition of a sheath
around the hood.
Figure 11 is a fragmentary isometric view of
another alternative embodiment of the inventio~ providing
dual-motion.
Figure 12 is a fragmentary isometric view of a
second alternative embodiment oP the invention providin~
dual-motion.
Figures 13 through 15 are frontal elevations of
various transducer configurations usable with the devices
of Figures 7, 11 and 12.
Figure 16 is a detailed circuit diagram of a
second embodiment of the powér drive unit of Figure 1.
Best Mode for Carryin~ Out the Invention
Referring now in detail to the drawings, the
reference numerals herein refer to like numbered parts in
the drawings.
7 1314~9
A dental hygiene device 20, in accordance with
the present invention, is shown in Figure 1. The device 20
has a handle 22, a transducer 24, and an applicator 26.
The device 20 is energized by a low-frequency, high-
voltage, low-power driving signal from an isolated power
drive unit 28. The 6i~nal is transferred to the device 20
through low-frequency wires 30. The power drive unit is
energized by conventional house current through an alterna-
ting current power line 32.
In one embodiment, as seen in Figures l and 3,the transducer 24 has a length substantially greater than
its width and a thickness substantially less than its width.
The transducer extends longitudinally from the handle 22.
The transducer is moun~ed in a cantilevered fashion in the
handle, that is, a first attached end 34 of the transducer
projects within and i6 rigidly attached to the handle 22.
A second, free end 36 o the transducer is free to vibrate
with displacement in a direction indicated ~y double headed
arrow 37, generally perpendicular to the longitudinal axis
of the transducer.
The transducer, constructed in this manner, be-
comes a resonator such that the maximum displacement of the
free end will occur at the resonant ~requency for the trans-
ducer; the resonant frequency being ~efined substantiallyby the length and mass of the transducer. Thus, the free
end 36 of the transducer will undergo maximum displacement
when the transducer i6 driven at its resonant frequency.
The fundamental mode of vibration for the transducer is
defined by: fo - C/L2 106 Hz, where L is equal to the free
length (the distance which the transducer extends from the
handle) of the transducer, and where C is a constant pri-
marily related to the mass and stiffness of the transducer.
Other modes, or hanmonics, of the fundamental frequency can
be applied to the transducer, resulting in a smaller dis-
placement of the free end Qf the transducer.
.
8 1314159
The applicator 26 extends transversely from the
longitudinal axis o~ the transducer 24 and i8 firmly attach-
ed ~o a face 40 of the transducer near its free end
36. The applicator can be a brush having a plurality of
bris~les sized to enter subgingival crevices and pockets to
transmit the vibrations from the free end of the transducer
to the fluids within these areas.
The dimensions and mass of the transducer are
selected so that the resonant fre~uency of the transducer
24 will be within the range of about 200 to 500 ~ertz, with
an optimum frequency of about 350 Rertz. It has been found
that at this frequency, mild cavitation occurs within the
subgingival fluid sufficient to disrupt and remove plaque
and to demobilize motile rods and spirochetes without damag-
ing the surrounding soft tissues. It is highly preferredthat the device be used daily to destroy and disrupt plaque
colonies while still ~oft, allowing the normal flushing
action of the mouth and gingival crevice fluids to remove
the destroyed and disrupted plaque colonies. Daily use
will also prevent the for~ation of hard, calcified plaque
(calculus) which can only be removed by dental profession-
als. It has been shown that application of this device to
human plaque for about five seconds results in dispersion
of the plaque and the bacteria responsible for plaque forma-
~5 tion with demobilization of the flagellated and ~pirochetebacteria, without damage to human epithelial and white
blood cells.
The device 20 is shown in Figure 3 with an elec-
trically non-conducting, elastic covering 42 which covers
the exposed surfaces of the transducer 24. ~hè applicator
26 is attached to the elastic covering at the free end 36
of the transducer. A low-frequency driving signal is
transmitted to the transducer by internal wires 44 from a
pair of contacts 46 which are adapted to engage the low-
~5 frequency wires 30. The wires 44 extend the length of thehandle within the handle.
9 1314159
It is highly preferred to clamp the transducer 2q
to the handle 22 at a nodal point 48 near the attached end
34 of the transducer~ The attached end is clamped between
an upper restraining handle portion 50 and a lower restrain-
ing handle portion 52. A cavity 54 is provided within therestraining handle portions 50 that a ~econd vibrating end
portion 56 of the transducer inward of the nodal point 48,
may vibrate freely within the handle. Mounting ~he trars-
ducer in this fashion prevents transmission of any
vibra~on from the ~ransducer to the hDndle, preventing
unpleasant vibrations in the handle. The transducer may be
made selectively detachable from the handle.
A detailed view of the transducer 24 is provided
in Pigure 5. The transducer has an upper conducting plate
5~ and a lower conducting plate 60 for introducing an alter-
nating electric field across an upper piezoelectric plate
64 and a lower piezoelectric plate 66 positioned there-
between. The upper and lower conducting plates may be
applied to the piezoelectric plates by any appropriate
means including vacuum deposition. In one configuration,
the upper and lower piezoelectric plates have opposing
polarities. Thus, when an electric field i5 applied across
the conducting plates, one piezoelectric plate will tend to
lengthen while the other will tend to shorten. The re~ult
is a bending or concavity produced in the transducer.
When the polarity of the electric field across
the upper and lower conducting plates is reversed, the
transducer will bend in the opposite direction. Thus,
application of an alternating electric field across the
transducer will cause the transducer to vibrate. Mounting
the transducer in the cantilevered fashion as described
will cause the transducer to vibrate as a resonator when
the alternating electric field is applied to the transducer
at the correct frequency, providing for maximum deflection
of the applicator 26 in a diréction perpendicular to the
lonqitudinal axis of the transducer.
(,~, 1 ` :
~ `~
lo 13141~9
An intermediate conducting layer 68 is provided
between the upper piezoelectric plate 64 and the lower
piezoelectric plate 66. The conducting layer serves to
provide electrical continuity between the piezoelectric
plates and to bond the piezoelectric plates together In
Figure 6, a leaf spring 70 has been bonded to the exposed
surface of the upper conducting plate 58 to alter the
natural resonant frequency of the transducer.
In another configuration, the polarities of piezo-
electric plates 66 and 64 are not opposed but are in thesame direction. Bowever, the upper conducting plate 58 and
the lower conducting plate 60 are electrically connected
together and to one side of the drive circuit. The other
side of the drive circuit is connected to the intermediate
conducting layer 68. This is the preferred configuration
since it requires half the voltage to produce the same
vibration and force described in the earlier configuration.
More than two layers of piezoelectric material
can be used in the transducer. Numerous other combinations
of polarity directions and interconnections can be imple-
mented in order to enhance the mechanical driving response
of the transducer and to minimize the required excitation
or drive voltage.
~igure 2 illustrates the dental hygiene device 20
in use. It is highly desired to remove both adherent supra-
gingival plaque 72 and adherent subgingival plaque 74 from
the tooth 75~ The device 20 delivers subsonic energy,
indicated schematically by the line 76, which is generated
by the cantilivered transducer 24, through the applicator
26 tc the tooth 75 and periodontal pocXet 78. Direct scrub-
bing action against the too~h 75 can be used to remove the
supragingival plaque 72 while the ~ingival fluid 79 couples
the sonic energy to the periodontal pocket 78. By causing
subsonic vibrations at the predetermined frequency, mild
3~ cavitation will occur within the gingival fluid, removing
the adherent subgingival plaque 74. The subsonic energy
associated with operation of the transducer at approxi-
ll 13141~9
mately 350 cycles per second w~ll additionally dama~e anddemobilize the motile bacteria of nonadherent plaque within
the gingival fluid, thereby preventing their attachment to
epithelium or tooth surface, and facilitating their removal
from the pocket or sulcus by gingival fluid flow. While
the vibrating energy level is sufficient to p~oduce sub-
sonic vibrations within the gingual fluid to cause mild
cavitation within the fluid to disrupt soft plaque colonies
from the surface of the teeth and gingival areas, and to
demobilize bacteria, it is insufficient to disrupt or
damage the surrounding soft tissues 84.
A second embodiment of the device 90 of the
present invention is shown in Figure 8. The applicator 26
is mounted to the free end 36 of the transducer 24 from a
surface 92 of the transducer defined by its length and
thickness, and extends generally from the surface. Thus
the applicator extends in a direction transverse to the
direction of displacement 37 of the transducer as the trans-
ducer vibrates.
Figures 9 and 10 show a third embodiment of the
device 100 of the present invention wherein the handle 22
has a longitudinally extending hood 102 projecting beyond
the free end 36 of the transducer 24. The hood 102
encloses the transducer on all but one side from which the
applicator 26 extends to protect the inside of the user' 8
cheek and other oral tlssue from contacting the vibrating
transducer and the vibration of the transducer from being
dampened by such con~act when positioned inside the mouth
during use. A front portion 104 and side portions 106 of
the hood shield the end and side surfaces of the transducer.
The front and side portions extend outwardly at least
coextensive with the botto~ face 40 of the transducer when
not vibrating. The hood 102 and its fxont side portions
104 and 106 are each spaced sufficiently apart from the
transducer 2~ to provide a space 107 therebetween which
allows the transducer to vibrate freely without touching
the hood.
.. . . . . .. _ _ _ _ . .
12 131~159
In ~igure 10, a flexible fluid-exclusion sheath
108 is provided to encapsulate the hood 102 and the trans-
ducer 24 to prevent fluid frQm entering the space 107 there-
between. The sheath is attached to the face 40 of the
S transducer 24, and ~he applicator 26 is attached to the
sheath in the vicinity of the free end 36 of the transducer
to utilize the maximum displacement of the transducer at
the free end.
A fourth embodiment of the device 120 is shown in
Figure 11. A second transducer 122 i~ mounted perpendicu-
larly to the first transducer 24 at the free end 36 thereof
and extends generally from the face of the transducer
defined by its length and width in the direction of maximum
displacement 37 for the first transducer. The second trans-
ducer i8 capable of excitation independent of the firsttransducer. Thus, the ~econd transducer is capable of
vibrating in a direction, indicated by a double-headed
arrow 123, generally parallel to the longitudinal axis of
the first transducer. The second transducer can be con-
structed from any number of piezoelectric polymers havingresilient characteristics. An insulator 124 is provided
between and connects the second transducer to the first
transducer to prevent communication of electrical signals
from the first transducer to the second transducer. In a
variation o the fourth embodiment, the first transducer 24
and the second transducer 122 are electrically connected in
parallel. Each transducer is thus excitable by a common
driving signal.
A fifth embodiment of the device 130 is illus-
trated in Figure 12 using a second transducer 132. The
second transducer 132 is mounted perpendicularly to the
first txansducer 24 at its free end 36 and extends general-
ly from the face of the transducer defined by its length
and thickness in the direction perpendicular to the direc-
tion o displacement 37 of t~e first transducer. In thisembodiment, the second transducer 132 is also capable of
vibrating in a direction, indicated by a double-headed
13 1 ~14159
arrow 135, generally parallel to the longitudinal axis of
the transducer. An insulator 136 i6 provided between and
connects the second transducer to the first transducer to
prevent communication of electrical 6~qnals from the first
transducer to the second transducer.
Figure 7 illustrates a six~h embodiment of the
device 140 wh~rein a plurality of transducers 141 extend
generally perpendicularly from an end portion 142 of the
handle 22 relative to its longitudial axis. The trans-
ducers used with this embodiment and those shown in Pigures11 and 12, can assume the various confiqurations shown in
Figures 13, 14 and 15. Each of these coniigurations has a
plurality of tapered or pointed fingers 144 to couple sonic
energy with the subgingival fluid.
Figure 16 illustrates an electrical schematic
diagram for the isolated power drive unit 28. The drive
unit has a drive oscillator 160 which generates a sinu-
soidal siynal at the desired transducer operating frequency.
A summing amplifier 162 sums the sinusoidal signal from the
drive oscillator with a direct-current signal applied to
the line 164, resulting in a DC-biased, increased-ampli-
tude, sinusoidal signal on the line 166.
A carrier oscillator l68 generates a high-
frequency square wave on the line 170 of a frequency at
least five times higher than the desired transducer operat-
ing frequency. Further, the frequency of the square wave
is sufficiently high enough to prevent physiological stimu-
lation when applied to humans. An inverter 172 inverts the
phase of the square wave from the carrier oscillator. A
pair of solid-state, high-frequency switches 174 and 176
are provided. The first switch 174 is enabled by the
square wave signal from the carrier oscillator 168, and the
second switch 176 is enabled by the inverted square wave
signal from the inverter 172. Thus, each switch turns on
and off at the carrier frequency and acts reciprocally;
that is, when the first switch conducts, the second switch
does not, and vice versa.
131~1~9
14
A convent~on~l s~ep-up isolation transformer 178
having a three-tap primary winding and a secondary output
winding is provided. Each outermost primary ~ap iB con-
nected through one of the switches to ground. The center
primary tap receives the resulting signal on the line 166
from the summing amplifier 162, causing an amplitude-modu-
lated output signal to appear across the secondary output
winding of the isolation transformer. The output signal
has a carrier frequency at the frequency of the carrier
oscillator and an envelope frequency at the frequency of
the drive oscillator. For the transducer 24 presently
being used, the isolation transformer has a turns ratio
suitable for stepping up the amplified sinusoidal signal on
the line 166 to an amplitude of approximately 150 volts.
Other turns ratios may be substituted to provide sufficient
voltage to drive transducers having differing piezoelectric
characteristics. The ~C-biased, amplified sinusoidal
signal on the line 166 is DC-biased 60 tllat the solid-state
switches 174 and 176 will conduct when enabled by the
signal from the carrier os-cillator.
A demodulator 182 is provided to receive the
amplitude-modulated output signal from the transformer and
to recover the sinusoidal signal produced by the drive
oscillator 160. The demodulator may consist of a conven-
tional full-wave rectifier with a smoothing capacitor to
provide a smooth sinusoidal wave, DC-biased and at the
envelope frequency. A capacitor 184 removes the DC bias
present in the sinusoidal wave from the demodulator. Thus
a rectified sinusoidal signal is presented for transmission
to the transducer. This signal has the same frequency as
the drive oscillator signal, but the amplitude o its
voltage is significantly stepped up. The isolated power
drive unit 28 thus provides a relatively low-frequency,
sinusoidal signal for the transducer 24 which is isolated
from any potential low-freguéncy, high-current signals
which may leak through the isolation transformer 178 if a
failure occurs.
~ l~l~la~
In ~igure 4, an alternative embodiment of the
power drive unit 200 i8 shown. The power drive unit has a
DC power supply to energize an oscillator and an amplifier.
The oscillator produces a sinusoidal signal at the desired
operating frequency for the transducer 24. The amplifier
amplifies the oscill~tor signal and introduces the signal
to the primary winding of an isolation transformer. The
amplifier also serves to buffer the oscillator from the
transformer. The isolation transformer has a turns ratio
sufficien~ to step up the amplified ~inusoidal signal to
drive the transducer from the secondary winding of the
transormer. In addition to the power drive units
described, batteries, rechargeable or otherwise, can be
substituted for the alternating current power sources.
Various other embodiments and variations of the
present invention are also contemplated. The scope of the
present invention is not to be limited to the above descrip-
tion but is to be defined according to the claims which
follow.
! 30
