Note: Descriptions are shown in the official language in which they were submitted.
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DENTAL DEV~CrE FOR GINGI~AL
R~RACTION AND CONDITIONING
~rt,is inv~nLion relaLe~ to dentistry dJId in
r~icular ~o d~viees and Ine~hods for gillgival re~racLion
an~ locali~e~ conditiol-ing as a step in complex dental
~ro~e~du~.s includirlg tooth reconstruction alld treatmellt.
Cingival retraction and conditioning is a tim~-
consumillg and somewhat traumatic ~rocedure. r t is required
for ~!xarn~le, in Lhe process of fa~bricating tooth crowns
whlct~lnust seat w~ll into the su~-~3ingi~al ar~a~ around
Lhe tooth, not to exceed the depth o the sulcus. To cast
the crown, a precision mold must be taken oL the tapered
prel)ared ~ooth to the extremes of the prepared ~ingival
~rough, which is the tiny open c3roove between Ih~yingival
tissue and th~ ground-down neck or prepared portion ~f the
tooLIl, so that the fabricated crown will extend illtO ~h~
su~-gingival area and also mate p~r~c~ly with all o~posing
tooth surfaces. To make an accurate mold,~the gin~ivaI
trough~mus~ be~kept open and fr~ed of blood, ~saliva and
d~bLis in a process known as qingival retraction.
An early and largely superseded technique of~
gillgival retractlon involves the use of a malleable coppe~r
sleeve filled with impresaion material and~adapted ~to be
oa~-efully ~ress~d and~manipulated over a ~ooth to~stress
alld distend the giO9iVd and squeexe out ~he blood and saliva
~ froln the trou(~h, after~which the lmpression i5 taken. It
is an accurate but painstaking procedure, diffioult to do
w~ll, often wasteful of time~ and traumati~ing to the
gingival Lissue.
The state of the art tachnique Eor Jingi~al
~0 r~traction superseding copper sleeve~, involves looping an
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absorbellt cord preferably treated wi-th a vasocorls~rict:incJ
chem:ical such as aluminum chloride about l:he freshly
prepared tooth and packing it into the gingival trough
using a pointed ins-tr~nent. Packinq the cord into the
trough is -te~ious al~d wasteful of time (as much as ive
minutes) because of poor visibi.lity in an extremely confined
area coupled with the inherent sponginess of ginglval
tissue whlch resists the cord placement. The cord remains
in place for several minutes holding the trough open,
absorbing saliva and blood in the trough, and treating the
traumatized tissue to control~further bleed~ing. It is
withdrawn an instant before the critical impression is taken.
In additlon to -the time taken by the dentlst installing the
cord and the inherent traumatizing of the tissue, the cord
has limited absorption ability and does not ef~ectively
protect the general area from the influx of additional;saliva.
Further, the stressful~action of packing the~cord
can create an artificially enlarged gingival trough extending
beyond the sub~gi~ngival llne where~tooth preparatlon ends,~
even to the point of occasionally tearing gingival tissue
~from~the tooth root beyond;the ~sulcus. The subséquent~Lm~
pression not infrequently~yields a crown casting having~a
~; skirt which extends beyond~the prepared portion of -the tooth
into an area in whlch -the~tooth may wlden in an almost~imper~
ceptible bulge or bump and thereafter narrow into an undercut.~
The inherent resilience of the polymerized or hardened impres-~ -
sion material enables i-t to be pulled erom~the undercut over
the enlargement, but the~memory of lts~exis-tence endures. As ~ -
a result, the finished crown, having~a rigid elongated skirt
smaller at its leading eclge than the widest diameter of ~ -tooth parts
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i-t is intended to surround, can bind in a s]ight].y
elevated pos:ition requiring the dentist to perEorm tedious
grinding operations in an attempt to achieve good crown
seating and tooth occulusion. This highly undesirable
and time-wasting characteristic has become increasingly
evident as less malleable and harder casting metals are
substituted for costly softer metals such as gold.
Accordingly, it is an object of the present
invention to provide a dental device and method for gingival
retraction and conditioning which are able without trauma
and in a fraction of the time presently required to carry
an absorbent medium into the tiny gingival trough around
the necks of prepared teeth to absorb all saliva and blood,
to entrain particulate debris, to treat against further
bleeding and to shield the entire area from encroaching saliva.
A further object Gf the invention is to provide a
dental device and method for gingival retraction and condition-
ing which do not enlarge the gingival trough beyond its natural
elastic limits and thus beyond the line of tooth preparation
and which~ therefore, result in impressions which yield castings
that do not bind before fully seating on the prepared tooth.
In the method aspect of the invention, gingival
retraction and treatment are effected by preparing a tooth
for crowning by grinding the side walls into truncated
conical configuration with the base disposed in the~sub-
~gingival area not in excess of the depth of the sulcus
to define a gingival trough between the ground-down walls
of the tooth and the flap of surrounding gingival tissue,
and placing on the tooth a body of coherent highly moldable
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flowable material haviny hydrosorbent charac-teristics at
least a-t i-ts surface. Pressure is applied on the body
axially wi-th respect to the tooth to cause the material
-to flow down the conical sides of the tooth both into and
outside of the gingival trough, to envelop the gingival
fIap while absorbing liquid blood and saliva with1n the
trough, thereby allowi.ng the flowable material to substan-
tially fill the trough to establish` balanced lateral forces
across.the flap. It is the~efore: held gently in its natural
posltion while it is conditioned aga1nst Lurther bleeding,
with the molded material shielding the entire area from
the inElux of additional sallva~. If it is de~sired to
slightly enlarge the trough without;damage to the tissue
a two-step process can be empIoyed in which a~bead of
flowable thixo~ropic material is first injected into
.trough followed by the body of flowable hydrosorbent
::
material. The ~ead then exerts gentle outward::pressure~ : ~
,
:on the elap of gingival ti~sue before the body molds~
~itself over the ou~ter wall~of the flap.
Devices and materials for clearing the::trough :~
:,
:~ and:treating the gingival tissue can take the fonn of a
small body of highly moldable~flowable coherent plastic
material treated or ~abricated to render it hydrosorbent,~
at leas-t on its surfacej but wi-thout lmpairing flowability
under~light pressure. The body has a volume capable of ~ :
-
inundating the treatment site and is molded by llgbt
pressure di.rected aIong the axis oE the tooth, Gausing
~:
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1244;26~3
it to flow down the sides of the tooth and both into and out-
side of the gingival trough to absorb blood and sallva and to
apply batanced light lateral forces across the gingival ~lap
to hold it in its natural position, or if a preliminary bead
S has been injected into the trough, to gently push the flap out-
ward to slightly enlarge the trough before the lateral balanc-
ing forces come into play. The body of material can be seated
in a thin walled open shell sized to match the size of the
treatment site and shaped to control the flow along the sides
la of the tooth into and outside of the trough.
In one embodiment of the present invention there is
provided a dental device for gingival retraction and condition~
ing prior to taking an impression comprislng a hlghly moldable
body of flowable coherent thixotropic material having a
substantial thickness st least approximating the length of the
exposed portion of a tooth ground to form a gingival~ trough
defined by a free~standi~ng flap of gingival tissue around the
base of the tooth, said body~having substantlal hydrosorbent
characteristics at least at one of its surface, said mass~
being adapted to be pressed onto the prepared tooth, whereby
pressure on the material causes it to Çlow over the tooth and
over the gingival flap to absorb the liquid matter from the
trough and to balance the lateral for~ces across the~flap to~
hold it in positionO ~ ~ ~
In one preferrsd embodlmsnt of the invention, ths
moldsble body can be formed of plastic thixotropic medium such
as hydrolyzsd high polymer silicone which can be rendsred
hydrossrbent by incorporating fibers. ~In this embodiment,~
:
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the balance and placemenk of fibers and plastic becomes
critical because the essential physical property of each
medium is antithetical to the othex and an imbalance can
render the device ineffective. Excess fibers can so effect
the moldability o the plastic that it will not enter the
gingival trough and excess plastic can render the complex of
fibers carried into the trough non-absorbent.
A mass of the thixotropic material sufficient to surround
a tooth and its associated gingival area is prepared with a
surface which includes an extremely thin layer of non-woven
united fibers rendering the surface hydrosorbent. This
structure can have a relatively short
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1656-~-F
life before the thixotropic plastic ~o inundates the fibers
that -they canno-t efeectively absorb, bu-t the freshly fiber-
faced plastic when pressed onto a prepared tooth will be
able to carry cer-tain amoun-ts of absorbing fibers into such
small areas as the gingival trough in a matter of seconds.
The ability of -the mass to convey surface fibers in-to small
or deep crevices can be enhanced by incorporatin~ additional
fibers within the body of the mass either randomly or in
layers, provided, however, that the amount by~weight of the
internal fibers be kept in a low ratio to the weight of -the
plastic.
The life and efectiveness of the product can be
~; Eurther enhanced by;1ncorporat1ng a second thiD layer of
; non-woven fibers in the surface over the first~layer without
; degradatlon of the flowability~o~f the ma~terlal. ;The first~
layer lS gripped by the plastic~f1owing lnto interstices~
n the~fiber mass, and ~he second layer can~be joln~d~to
; the first hy means;of a thin spray~of adhesive ~r~alter~
natlvely, the first layer can be~formed with enlarged
interstices in the form of pin holes or shQrt slits,
preferably amountlng ln the aggregate~Lo a small~percentage~
oE the surface area, through whioh the~plastlc~can~flow~to~
establish a mechanloal band with the~filaments of the top
layer. The resulting structure~ lS capable of fl~owing into
minute crevices such as the gingival trough and of absorbing
all liquids in the trough.
The pcoduct can be packaged as indi~idual unlts
n a emi-oylindrical carrieF shell exposing -the absorben~t
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~Z44~ 1656-A-F
surface and by means of which the device can be pressed
onto a prepared -tooth either by the dentist or by the
patient biting against the shell. Alternatively, the mass
with one or two absorbing surfaces can be contained in a
lateral sheath in a variety of configurations; rectangular,
round, oval or arcuate, for constraining the mass against
lateral flow when pressed onto a tooth. When the patient
bites on the device, the tooth opposing the prepared tooth
will act as a piston, driving the wor~ing surface of the
material into place around the tooth under the constraint
of the lateral sheath. The sheath should be collapsible at
least where it encounters other teeth and can be made at
least in part of highly absorbent material. In~one preferred
embodiment the lateral sheath can be made of both repellent
and absorbent material such as sponge, rubber or foamed pIastic.
Also, the outer or non-working surface oE the unit~can be
packed with highly absorbent material suoh as cotton or a
sponge màterial.
The absorbent layer of fibers is preferably
impregnated with a vasoconstricting chemical such~as
epinephrine or aluminum chloride to arrest bleeding~of
traumatized gingival tissue. In~the case of the two-stage
process in which a bead of flowable thixotrop1c material
is first in~jected into the trough, it`is desirable to
include the vasoconstrictor in the bead material.
: : ~
Figure l is a view in perspective of one
embodiment of the invention.
Figure 2 is a view in enlarged scale taken in
cross-section through a prepared tooth and the surrounding
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1 6 5 6 -A - F
gums and showing the absorberlt device of :Fiyure 1. in place
on the tooth and retracting tlle gingival trougll.
Figure 3 is a view in perspective showing another
embodiment of the invention.
Figure 4 is a view in perspective showing the
lateral con-tainer of the uriit of Figure 3 separated from
moldable body portion.
Figure 5 is a view in cross-sec~tion through a
tooth prepared for crowning, showing the embodimell-t o-f
:~ 10 Figure 3 in place in the patient'~s mouth and ac-tuated by ~ the oppos~ng upper tooth.
; Figure 6 is a view in perspective o~ another
: embodiment of the lnventlon~
: : Figure 7 is a view in cross-sect.ion of another: ~ :
: ~:
embodiment of~the invention~
Figure 8 is a diagramma~tlc view, hlghly bnlarged
and not in scale, illustrating the~surface and sub-sur~ace
characterlstics o~one Eorm of~ the inventlon.~
Pigure:9 is a:view similar to~that of:Figure 8,
~ illustrating~another~form o~ the invention. : ;
~: : Figures lOA, lOB and~lOC are a ser~ies of~corres~
ponding views in cross-section~1llustrating~another~
embodiment of the invention.
: DESCRIPTION OF THE PREFERRED;EMBODIUENT
: 25 ~ ~Referring to Figure 2, the new method of gingival ~ :
retraction and conditioning is illus~trated~in.process. The
~ ~ tooth ll has been prepared for rece1ving the crown by :~
: . ~ grinding the side walls down to form a genera:lly~truncated
: conical conEiguratiol- having its base in the sub-g-ngi~al
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1~44~68 :L6S6-A-F
area ~.re:Eerclbl.y al~out two--Lhiîds of the depth oE the ~ulcus,
which is the dep-th beyond which the gingival tissue is
-ti.gh-tl.y bonded to the tooth and which should in no event
be disturbed. The process of cutting down the tooth creates
the gingival trough 12 whi.ch l.S the space between the sur-
round:ing gi.ngi.val flap ~ormed by tissue l?a. The trough is
typically on the order of l.0 millimeter wide at ~he top and
3.0 millimeLers deep and will be filled wi-th blood, saliva
and debris which must be removed and ~the flow of blood :
staunched bef~re the highly critical :impresslon for making
the c}own can be taken.
In accordance with one~embodiment:~o~ the invention,~
the gingival trough 12 is~cleaned and~the tissue condi~tioned:in
~~; a swift:process which does~not dis-tort or~distend he~gingiva: ;
~nor, therefore, does it enlarge the gingival trough.~WhiIe the :
procedure~is characteri~ed ln thls~embodiment~in the~historical
: nomenclature~"gingival retractlon"~it~wlll be u~derstood that~
the:gingiva is not driven back from the tooth but~is, rather,:
carefu~lly and gently sustalned ln lts natural posi:tlon~around
20~ the~prepared~tooth. To this end,;;a~body lO of~hlghly~moldable~
material 13 having~hydrosorbent characteristics at:least at ~
its~surface l6,~1s moldad or flowe~d~by means~oE light~pressure
applied generally axially: of:the tooth, causing iL~to flow
down the side of the prepared tooth:~and both into and::outside;
25 ~ of the glngiva] trough;to envelop the ginglval;flap~in a
ma~tter of seconds while absorbing the llquid ln~the~trough;~
The forces acroas the Elap remain balanced to hold it precisely
`in its natural posit~ion. The addltlon of a~Vasoconstr}ctor such
as aluminwn chloride stops the flow of blood~where tissue
~30 might have been damaged in the prior grinding operation.
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~Z44Z6~3
'rlle coherent mass 17 is withdrawn an instarlt before the
impression is taken. Thus, ~he invention provi.ded non-
-tra~natic and swif-t ging:ival re-traction and conditioning in
wh;c}l the molda~le ma-terial is Elowed on both sides of the
gingival flap either under the light pressure of the -tooth
14 above pressing on a thin walled semi-cylindrical con-tainer
or shell 15 or, if preferred, by Einger pressure by the dentist.
Tlle core ma-terial 13 is formed of a coherent
highly moldable plastic material of high viscosi~ty. A
highly moldable material which is nevertheless sufficiently
coherent to be handled as a mass can be deflned as thixo-
tropic or dilatant. An example of such material is
hydrolyzed high polymer silicone commonly known as silicone
putty. Inorganic fillers, such as boric acld, can be used
in the material to con-trol its viscosity or rate character-
:
istics without impairing its ultimate Elowability. Qther
examples of materials having thixotropic properties lnolude
~hydrocolloids and certa1n unpolvmerized synthetic~rubbers
(bu-tanes), certain gels and sol-gels. The~ thixotropic
material5 are non-absorbent and lmpervious to :moisture and ~ ;;
cannot, therefore, be flowed lnto~a~glngival trough filled ~ ;
with blood~and saliva which block its en~ry even though it ~;
will readily flow into a dry trough. In accordance with
the invention, the thixotropic core 13 can be rendered
:
hydrosorbent by having intimately bonded thereto a thi~n
outer layer 16 of non-woven~absorbent fibers, such as wood
flbers used in making absorbent papers, cotton fibers or
-Lhe like. The non-woven fiber layer is formed as an
ex~remely thin paper-like sheet of united fibers preferably
rolled to a thickness of approximately .0~ to .07 milllmeter~.
The interstices in the ~ibar sheet placed against the
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~244~ l656-A-F
surface Oe the thixotropic core wllL receive projections
of -tl~e tllixotropic mater:ial in the form of a myriad of
tiny finger~ which mechanically bond -the fiber layer
intimately to the core. The product so foxmed, particularly
if freshly prepared, when pressed over a tooth will
retain its ab:ility to ~low into tiny depressions such
as the gingival area, but it will also carry fibers into
the trough where they absorb the liquids and allow full
penetration of the core material. 'There is a tendency,
particularly if the trough is deep and narrow, for the
fiber sheet to be torn away by the distending plastic
core to expose a leading edge of the base core material~
which is non-absorbent. To overcome this undesirable
characteristic in accordance with the present invention,
- 15 fibers 17 (best seen in Figures 8 and 9) are entrained
and dispersed in the body of the thixotropic mass,
particularly in the space immediately beneath the absorbent
surface 16. The proportion of embedded fi~ers must be
closely controlled. If embedded in~excess quantity, the
material loses its essential moldable and flowable charac-
- teristics. Using high polymer silicone putty as the base,
and fibers from paper as the entrained material, a ratio~
by weight of 3~percent fiber ~ill has been found to~ be
effective, although the ~uan-tity can~range between 2 and
4 percent. It should be noted that thé fiber-impregnated
thixotropic mass is not absorbent p~ se but~the entrained ;~ ;
f~ibers apparently react mechanically with the surface fibers~
::
to prevent -tearing and parting of the absorbent sheet over
highly distended portions of the core material, such as
those p~netrating the gingival trough.
.
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1656-A F
The single ~urface layer of absorbent mclterial
as clescribe(l a~ove can, un~er certa:in circumstance~,
exhibit a characteristic of climinishiny efEectiveness.
IE tlle thixotropic core, wi-th the passage of time or due
to pressure on the surface, penetrates the absorbent layer
toodeeply in establishing the mechanica:l bond or, if the
volume of core material in the layer becomes excessive,
the abili-ty to asborb liqu.ids declines. This effect can
be prevented in accordance with the invention by the
~10 structure shown in Figures 8 and 9;
Referring to Figure~8 in which a very small
~ I
por-tion of the device is shown in highly enlarged scale,
the thixotropic body material 13, ln addition to entraining~
randomly spaced fibers 17 in an amount corresponding to
. ~ 15~ approximately 3 percent by weight and distrlbuted more or
less uniformly throughout, has attached to its upper surface
two dlscrete layers 16a and 16b of ron-woven fibers.~ ;Eaah~
layer is preferably approximately .Q3 to~.07~millimeter~
n thick~ness. The lower layer~is intlmately bonded~to~the~
20~ core by~a myriad of fingers l8 penetrating~1nterstices~
among the;fibers. The lower layer i9 also~formed~wlth~an~
` array of perforations 19 amounting in the-aggregate to~less
than~lO~percent oE its a~rea and~through~which th~e~thixotropic~
material penetrates to engage~the underside oE the~upper~
layer 16b and mechanically bond with its fibers. As~seen
;~ ln the drawing~, the~: .le~ft-hand~aperture l9~is shown empty
o the flowable material. In the ather a~ertures, the core~
material 20 has spread among;-the fibers closes~t to the
; ~ aperture and into the fibers of the upper layer in a head~21
among the Eibers, thereby forming a mechanical bond~holding ~
; ' ::
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~Z4~68 l656-A-F
tt,e :Layers ln p].ace. '.I'he i1:lustration of FicJure a i8
clia~rammatic to show the pri.nci.ples of the .inven-t.ion
and is not intenclecl to be in scale. For example, the
apert~res 19 are preferahly made substantially larger
in diameter than the thickness oE the layers in order
to hasten the bonding of the upper layer. Howevex, by
severe]y limiting the d:irect exposure o the upper layer
to the thixo-tropic core, saturation of the upper layer or
significant encroachment at its surface by the core
material is prevented and~the ability of the fibers to
absorb liquid is preserved. The double layer construc~lon
~ of Figure 8 has a long shelf life and can withstand sub-
; ~ stantla1 molding and worklng without bri.ng~ing deleterious
quantities of the thixotroplc base material ~o the surface.
In the arrangement of Figure 9, there are shown
thixotropic core layers 22 which do not have fibers uniformIy~
~: dispersed throuqhout their mass as;in the case of Fi~ure 8.
Instead, one or more concentrated fiber layers 25 are
enbedded in parallel spaced-apar-t fashion, but never-theless
ln substantlally~the same overall weiqht ratio as in the
case of the more thinly dlstributed fibers oe:Fi~ure 8.
The thickness of the: core:material:layer 22 ~hich is~free~ ~ :
of fibers is extremely small, on the order of .5 mlllimeter,~
: ~
so -that when the device is~molded onto a tooth~and the~
25 ~ core material distends into a t:iny projection entering the
: gingival trou~h, the interior layer of fibers can mlgrate
to the upper layer:where they ~strengthen t~e upper~layer
against tearing. In Figure 9, the surface layers 23a and
23b are bonded by an adhesive layer 24 1n the form of an
aerosol spray of contact cement kept thin eno~gh so as not
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iZ~4ZG8 1656-~-F
to impair ~he porosity of the laminated structwre~
althougll ik wi.lL be unc~erstood that mechanical bonding
by :EincJers of core materi.al, as in Figure 8, can be used
as can a combination of bo-th techniques. It will be
unders-tood also -that the internal fiber layers 25, while
shown parallel to the surface layers 23a and 23b, may be
at angles, including perpendicular, thereto~
In each of the embodiments of Figures 8 and 9,
the non-woven fiber surface is sufficient1y pliant -to
permit the -thixotropic core material to EIow into small
crevices, such as the gingival trough, carrying with it a
layered mass o:E absorbent fibers which absorb substantial
volumes of ambient liquids, thus clearing the~trough. A
.1 millimeter dual layer o~ fiber,:for example, has the
abllity to absorb all of the llquid contained~in a trough~
;
3 millimeters deep without impeding the abili~ty of the~
thixotropic material to flow into the spaoe. Unexpectedly, ~:~
~he balance of forces inherent in the axially directed
: molding action around the tooth and the gingival~ tissue
; 20 coupled with the unique physloal:oharaoteristlcs~oE;the
thixotropic material:effect a complete gingival ~etraction
in a matter of seconds gently and~without trauma:.~ The fibers,~
: ; particularly the surface layers, impart suffici~ent lntegrity
~ :~` to the device to enable it, notwithstandin~ the thi~otropic
: 25 mass, to be easily ha~ndled and to maintaln~its initia~
: geometry until dellberately~molded over a tooth. ;:~
Referring to Figures 3~to 5, there is lllustrated ~ ;
another embodiment. of the invention in Which the upper
tooth 14 rather than bearing down on the shell or housin~ :~
30 portion 15 as shown in the device 10 of Figures 1 and ~,
.. ~
~24~L268
1656~A-F
bears down on the top of a column 44 of thixotroplc
material to press the column and its bottom surface 26
against tlle prepared tooth 11 to urge lt to f].ow into the
gin(Jival trough 12. In this modification, at least the
lower surface 26 includes an absorbent layer of fibers
of any one of the types described above. Irhe body or
mass 44 of thixotropic material is contained in a lateral
housing or container, best illustrated in Figure 4. The
housing 27 is comprised of a pair of side walls 28 and
29, preferably formed of an absorbent material, such as
semi-rigid cardboard. The cardboard sides 28 and 29 are
attached to a continuous flexible strip 3~ having high
tensile strength, such as Mylar film or filament-reinforced
plastic tape. The flexible strip bridges the side portions
15 at its front and back 31 and 32 and is wrapped around a
rectangular block 33 of thixotropic core material, at least
one of the exposed surfaces of which has an absorben-t layer
af-fixed thereto. The free ends of the flexible strlp 30
have affixed thereto semi-rigid cardboard tabs 34 and 35
which are brought together and secured to form a handle 36,
as shown in Figure 3. When the device~is pressed down over
the prepared tooth, either by the dentist pressing with his
fingers or by means of the patient's own tooth, the flexible
end wa~ls 31 and 32 will be;collapsed while still form1ng
a bridge restricting the flow of the thixotropic material ~:
out the ends of the device, thereby concentrating the~
molding forces over the treated area.
~ eferring to Figure 6, there is illustrated a
simpli:Eied version of the device in which the mass of moldable
thixotropic material is rounded and enveloped ~y a lateral
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~Z4~2~ 1656-A-F
wall 37 of flexlble sheet material having good tension
characteristics similar -to the material of -the strip 30 in
Figure 4. Forming the wall 37 oE thick sponge rubber is
particularly advantageous because it is both resilient and
absorbent. In such case it is preferable that the absorbent
fibers on the surface 38 overlay and be bonded to the sponge
rubber margin. One or both of the exposed end surfaces of
the thixotropic core 38 is covered with an intimatel~ bonded
layer of absorbent material. In the illustration of Figure 6,
the single absorbent surface is identified by directional arrows.
The device when clenched between the teeth, will conform to the
opposing surfaces and at the same time, the flexible wall 37
will collapse where it interferes with other teeth.` The
arrangement of Figure 6 is particularly usefuI for use in a
number of different locations in the mouth, as it can be molded
by the dentist into various elongated ovals or into an arcuate
configuration useful where the tooth line curves.
Referring to Figure 7, there is illustrated a
further modification of the design in which the thixotropic~
core material 39 and the absorbent intimately bonded surface
40 occupy only a portion of the height defined by the side
walls 41. A highly absorbent material, such as a cotton~wad
42, is fitted in the space on the non~working side of the core
39. If desired, a semi-ri~id barrier 43 can be inserted between
the absorbent cotton 42 and the thixotropic core 39 to increase
the downward pressure on the moldable material. Substantial
clearance between the edges of the semi-rigid barrier 43 and
the side walls affords pressure relief.
In each of the embodiments of the invention, it
is`preferred that the absorbent surfaces have impregnated
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1656-A-F
1;~4~6l5
therein a vasoconstricting chemical, such as epinephrine or
aluminum chloride, to assist in cond:itioning the gingival
tissue by controlling the blood flow. The chemical in the
dry powdered form can also be incorporated in the plastic core
or body medium as well as in the filler fibers, preferably by
soaking the fibers in a liquid solution of the chemical,
drying and thereafter incorporating in the core material.
A characteristic which is common to all of the
embodiments of the invention described above is rapid
balancing of the forces across the gingival flap imposed
by the flowable thixotropic material as lt flows down both
sides of the flap. This positions the flap in its natural
position and otherwise prepares the site for the subsequent
step of taking the impression of the tooth walls and the
surrounding trough so that a substantially perfectly fitting
crown can be cast. In certain situations, however, it may
be desired to retract the glngival tissue by forcing it
outwardly away from the tooth wall to form an enlar~ed
trough. The only generally known techniques for such
gingival retraction involve the use of either copper sleeves
or retraction cords which are pressed~hard into the trough~ ;
with substantial attendant trauma
In accordance with the present invention, however,
gingival retraction can be accomplished free of trauma~and
more swif~ly than prior art techniques. Broadly the retrac-
tion is accomplished by gentle fluid pressure in which,
before the pressure forces across the gingival flap are
balanced, differential pressures are established which
gently urge the flap outward while clearing the trou~h
of liquids and debris.
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~24~ 8
l~56-A-F
Referr:inc3 to Figures lOA, :1.013 elnd lOC there is
shown the le~-t side portion of a prepared tooth 45 and
surrounding gingival tissue 46 including a ging:ival flap
47 defining a gingival trough 48. The gingi.val flap 47
is, similarly -to the rendi-tion in Figures 2 and 5, somewhat
diagLamatic rather than being a scaled ana~omically precise
rendering. It i~ intended to represent a gingival flapi
which is~narrow and therefore soft, fragllR and lacking in
~ resilience. Such tissue is osp~cially~difficult -to deal
with in retraction procedures because it is~ mo t apt to be
damaged and, more importarlt, to tear away from the root of~
the tooth, creating overhangs~whieh result in~impr~sslons ~ ;~
from which mal-f;itting crowns are cast.~;~Also, such~soft
narxow ~lap tissue is subject to proIapse against the tooth,
~making~an impression of tbe ~trough~lmpossible.
Referring to Figure lOA, the gir~gival~trough~4
is shown having injected~into it a bead of flowable thixo~
tropic ~material 49 extruded f~om the~tip 50 of a dental
syringe 51. The~flowable~materiaL 49~is pr~ferably~ln th~
20~ ~middl;e range of viscositiee and ~omewhat less v~scous~than~
-the material of which the moldable bodies~10 an~ 27; ~Figùre~s
~: : :; 2 ~and 5)~ respectivel~, are formed but is preferably~oE the ~
same general character. The viscosity is;selected to~a~hi~ve
~an extrudable;~coherent bead ~hich will ~low~lnto the~trough
but not go viscous that it is dificUlt to make lt ~tay in~
the t~rough, particularly at the polnt~;of cutting of~ th~ flow
and withdrawing the syringe. Also, the viscosity of~the~
bead is related to its ~bllity to be un~ted a8 a sinyle
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: :
1~44~68 1656-A-F
structure with the material of the following mass of
treating material, as described below. At the lowest
levels of viscosity the bead becomes less capable of
joining with the following mass. As the bead flowable
material 49 is injected into the gingival trough around
the tooth, it displaces the liquids in the trough and
entrains particulate matter which might be left over from
the grinding operation. The material 49 is preferably
treated with a vasoconstricting agent of the type previously
described and it may or may not include entrained flbers
depending on the degree of viscosity desired. As best seen
in Figure lOB, the bead of material 49 is flowed into the
trough in sufficient amounts to substantially fill it. The
filling step of the process is essentially gentle and non-
traumatic with the pressure of the flowable material wlthin~the trough exerting light pressure outwardly on the gingival
flap 47 causing the trough 48 to widen slightly. The dis-
placed liquid material 52 from the~bottom of the trough
appears in the open space on the surface of the injected~
material.
A mass or body 53 of~flowable thixotropic fiber-
~impregnated and coated material 54 corresponding to the
material 13 of Figure 2 (only a portion of which is repeated
in Figure lOB) is pressed down over the prepared tooth and
~25 filIed trough. The flowing material first engages the mate-
rial 52 above the bead in the trough at which~time absorbent
layer 54 absorbs the displaced material 52. In addition, a
gentle downward pressure on the gingival tissue and the trough~
can act to further movo the gingival flap 47 awa~ from the Looth
:~Z49L'~;8
1656-A-F
.in a gentle retraction action, q'he -tim~ at whiah thi~
occurs .in the process is shown by th@ dot-da~h outl.ine
-to the left o~ the trouyh in Fig. lQB. ~s the moldable
body 53 is pressed Eurt.her down over the tooth and
ginyival tisaue, a portion Will flow over and around
-the ~ingival flap 47 aEter Whi~h the p.res~ure forces
across the gingival flap 47 b~come~balaDa2d in a ~lanner
similar to the aation of -the mo]dable bodies 10 and:27~
of Figures 2 and 5. Addit,iona.l va~oco,nat,rlcting materlals
can be incorpo~ated in the:flowable~body 53 particula~ly on
the surfa~e th~reoft The~materlal~ of~the~;in3ected bead ~
49-~and~the~flowable bod,y 53~are c,~,n!pati~le~and~ael~-a~herlng,
a oharactQrlstic which is aug~nted by ths fiber content oF
the flowabl~ body 53. Thùs the ~ea,d 49 and the body~53
: - : : : .:
15: unite as a single unitary;6tr,u~cturQ,~
Re~erring to Figure~lQe/ thq:eoin~ined bead~49;~
and moldable bady 53 are :sh~o,wn~b,eing ~ithdrawn from the~
tooth leavi~g behind a gently ret,racted and fully condi~
tioned~gingival trou.yh fro@~of~ gul~2~ n~,~pa}ti~ul~te
20~ ~ matter~and in condi-t1on Eor the in~ediate ta~lng: o~f the;
: impression from which t,he cr,oW~ ~f t.he -to,o~h will~e ::~
.: ~: ~ :
: fabricated.
; 'The ability oE th~e ~ead 49 and:th~m~ol~.a~le
body :53 to u~iLe acroas th~a,bsor~en layer S~
essential to the ~ç~e~sf~ rac,tiçe af ~his el.nb,odlmen,t
of the invention. A~ ~tate~, the ~i~e~sltY for` the
bead as it is flowed into th~ gin~i~al trough ~houl~
::
- be sufficie~tly high tQ fo.rm a coher~n~, pac~ing 1n the
; ~
: ~
:-2Q-
.
12~'~Z6~
1656-A-F
trough. Commercially available s:ilicone or vinyl polysiloxane
base materials used Eor impression taking can be used includ-
ing those sold under the trademarks Reprosil, Citricon Base,
Cuttersil Putty, Permagum and Express, although they appear to
have somewhat different abilities to bond to the absorbent
layer. A workable form oE injection material can be prepared
by blending the following materials in the indicated percentages
by weight, silicone putty 27 to 30~, vinyl polysiloxane 57 to
60~ and medium grade dental pummace 10 to 16%. The material
can be used in the syringe without the associated activators
because it is not essential that it polymerize in situ. Such
polymerization is not, however, incompatible with the process
and could in fact be desirable, if the problems of timing and
the additlonal step of mixing with the activator can be toler-
ated, because it can result in~a better pre-impression reading
of the trough preparation. In such cases pummace and silicone
putty can be eliminated in favor of simple activated vinyl
polysiloxane. Also, when the two-stage process involving~the
injected bead followed by the flowable hydrosorbent ~ody is
used, it should be noted that the body can be more viscous
because it need not penetrate the depths of the trough;
essentially it operates to apply gentle pressure~to the tissue
and the injected bead and to adhere thereto so that it is ~
-:
removed as one with the absorbent body.
If it is desired to obtain a "pre-impression"
impression of the trough using the single-stsge process, a
small charge of low viscosity, activated impression material,
such as Express, can be injected lnto the coherent body in
approximately the center thereof using a syringe. The axial
hole left by the withdrawn syringe is centered over the
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Z6~ 1656-~-F
tooth all as described above. The impression material will
flow over the prepared tooth and also be driven into the
gingival trough~ The body is held in place until the material
polymerizes. It will then adhere to the body and be removed
as one therewith, yieldin~ an impression from which the dentist
can determine the effectiveness of his preparation. The
syrlnge injection into the body is preferably preceded by
cutting through or removing the absorbent surface layer in
the area of the in~ection.
While the invention has been described having
reference to the preferred embodiments, it will be~under-
stood that it can take other forms and arrangements without
departing from the spirit of the invention. For example,
the expendible or disposable housings described above can
be replaced by re-usable housings or carriers of a variety
of shapes and sizes. The devlce can be formed in the shape
of small toroids adapted to be fitted over the prepared neck
of the tooth and then molded into the gingivaI trou~h. Also,
the device can be used for hemostasis to control bleeding
after tooth extraction or bleeding after cavity preparation
prior to filling. It can also be used effectively at the
time of crown insertion by molding it over the freshly
cemented crown where it will isolate the tooth from saliva
and blood to prevent contamination of the unhardened cement,
seal and hold the crown in occlusion, and pick up surplus
cement. While natural fibers have been described as pre-
ferred for the absorbent medium, it wi]I be understood that
certain synthetic fibers with similar characteristics can
also be used. The invention should not, therefore, be
regarded as being Iimited except as defined in the
following claims:
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