U.S. patent application number 12/233448 was filed with the patent office on 2009-02-19 for apparatus and method for root canal obturation.
Invention is credited to Randall Rex Calvert.
Application Number | 20090047634 12/233448 |
Document ID | / |
Family ID | 40363247 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090047634 |
Kind Code |
A1 |
Calvert; Randall Rex |
February 19, 2009 |
APPARATUS AND METHOD FOR ROOT CANAL OBTURATION
Abstract
The present invention is directed to root canal obturation in a
tooth. In one embodiment, a plug is positioned in a root canal and
bonded to the root canal by applying a light-curing adhesive to the
canal and exposing the plug to a light source to bond the plug to
the root canal. In another embodiment, a carrier is disclosed
having an optically transmissive plug portion for insertion into
the canal. In still another embodiment, the plug portion of the
carrier includes an optical fiber to transmit light from a light
source into the plug portion. In still yet another embodiment, a
filler material is heated and injected into the root canal in a
semi-liquid state and exposed to light to cure the adhesive.
Inventors: |
Calvert; Randall Rex;
(Bellevue, WA) |
Correspondence
Address: |
BLACK LOWE & GRAHAM, PLLC
701 FIFTH AVENUE, SUITE 4800
SEATTLE
WA
98104
US
|
Family ID: |
40363247 |
Appl. No.: |
12/233448 |
Filed: |
September 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11392462 |
Mar 28, 2006 |
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12233448 |
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11101969 |
Apr 8, 2005 |
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11392462 |
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10035544 |
Dec 28, 2001 |
7125254 |
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11101969 |
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Current U.S.
Class: |
433/224 ;
433/81 |
Current CPC
Class: |
A61C 5/55 20170201; A61C
5/50 20170201; A61C 19/003 20130101 |
Class at
Publication: |
433/224 ;
433/81 |
International
Class: |
A61C 5/02 20060101
A61C005/02 |
Claims
1. A plug configured to be implanted into an endodontically
prepared root canal of a tooth, comprising: an elongated body
comprised of a biologically compatible, nonporous, resilient
material of uniform composition having a distal end and a proximal
end and having a length to allow the distal end to be positioned
adjacent to an apical portion of the tooth when the body is
inserted in the root canal of the tooth, the body occupying
substantially an entire volume of the root canal when implanted;
and an adhesive compound provided on a surface of the elongated
body and adapted to be interposed between the elongated body and an
inner surface of the root canal, the adhesive compound being
configured to chemically bond the body to the inner surface of the
root canal; wherein the elongated body is formed from a material
such that an interior of the elongated body is resilient after
being chemically bonded to the inner surface of the root canal.
2. The plug of claim 1, wherein the elongated body is formed
entirely of an optically transmissible resilient material.
3. The plug of claim 2, wherein the adhesive compound further
comprises a dual cure adhesive having a first curing rate when the
adhesive is exposed to illumination and a second curing rate when
the adhesive is not exposed to illumination.
4. The plug of claim 1, wherein the elongated body is formed from a
polymethylmethacrylate.
5. The plug of claim 1, wherein the elongated body is formed from
silicon-based organic polymer polydimethylsiloxane.
6. The plug of claim 1, wherein the elongated body is formed from a
composition of butyl methacrylate polymer and butyl methacrylate
monomer.
7. The plug of claim 1, wherein the elongated body is formed from a
thermoplastic polymer.
8. A method for obturating a root canal passage in a tooth,
comprising: applying a light-curing adhesive to the root canal
passage or to a plug; implanting the plug into the root canal
passage, the plug being optically transmissive and formed of a
resilient material and sealing an apical portion of the root canal
when implanted; and exposing a portion of the plug to a light
source to cure the adhesive, the adhesive being formed from a
composition whereby the plug is chemically bonded to the root canal
when implanted; wherein the plug is formed from a material that
cooperates with the light-curing adhesive such that the plug
remains resilient after the adhesive is cured.
9. The method of claim 8, wherein the plug is formed entirely of an
optically transmissible resilient material.
10. The method of claim 8, wherein the plug is formed from a
composition including a butyl methacrylate.
11. The method of claim 8, wherein the plug is formed from
silicone.
12. The method of claim 8, wherein the adhesive compound further
comprises a dual cure adhesive having a first curing rate when the
adhesive is exposed to illumination and a second curing rate when
the adhesive is not exposed to illumination.
13. The method of claim 8, further comprising heating the plug
prior to insertion into the root canal passage.
14. The method of claim 8, further comprising forming an access
opening in a crown of the tooth prior to inserting the plug, and
further wherein the plug is inserted such that it fills the root
canal but does not fill the access opening formed in the crown in
the tooth.
15. The method of claim 8, further comprising: providing a
plurality of plugs, the plurality of plugs having a plurality of
different sizes adapted to conform to the size and contours of a
corresponding plurality of root canals; and selecting the plug from
the plurality of plugs, the selected plug having a distal end, a
proximal end, and a length sufficient to allow the distal end to be
positioned adjacent to an apical portion of the tooth when the plug
portion is implanted in the root canal of the tooth, the distal end
extending to the apical portion and substantially abutting the
walls of the root canal when the plug is implanted, the plug
further having an elongated support portion.
16. The method of claim 15, wherein the elongated support portion
tapers from the proximal end to the distal end.
17. The method of claim 16, wherein the elongated support portion
further includes a handle.
18. The method of claim 8, wherein the plug is formed from a first
component of a two-component bonding system and the adhesive is
formed from a catalyst component of a two-component bonding
system.
19. The method of claim 8, wherein the adhesive comprises a
two-part bonding system and further wherein the step of applying
the adhesive comprises applying a first part of the two-part
bonding system to the plug and applying a second part of the
two-part bonding system to the root canal passage.
20. The method of claim 8, wherein the plug is formed as a pellet,
and further wherein the step of implanting comprises heating the
pellet to a flowable state and injecting the flowable pellet into
the root canal.
Description
PRIORITY CLAIM
[0001] This application is a continuation-in-part of application
Ser. No. 11/392,462, filed Mar. 28, 2006; which is a continuation
of U.S. application Ser. No. 11/101,969, filed Apr. 8, 2005; which
is a continuation of U.S. application Ser. No. 10/035,544, filed
Dec. 28, 2001 (now U.S. Pat. No. 7,125,254), each of which is
hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to root canal therapy, and
more particularly, to an apparatus and method for performing root
canal obturation.
BACKGROUND OF THE INVENTION
[0003] The root canal procedure is a well-known endodontic therapy
for the treatment of pulp necrosis, inflammation, and for the
retreatment of previously obturated canals that have failed. The
procedure generally includes removing at least a portion of the
tooth crown to expose the canal system, followed by the extraction
of the contents from the one or more canals of the tooth. The
canals are then generally subjected to mechanical shaping
operations, such as reaming or filing in order to reduce and/or
remove various irregularities within the canal, and to prepare the
canal to receive a filling material. While the canals are shaped,
the canals are regularly cleaned with a variety of solutions to
remove material dislodged by the shaping operations, and to prepare
the canals to receive a filling material. The filling material is
generally tightly packed into the canals to form a seal within the
canals to prevent leakage into the canal spaces. An additional
filling material is then generally placed in the crown opening.
Alternatively, a replacement crown may be affixed to the tooth to
complete the procedure. When the coronal tooth structure is broken
down, it becomes necessary to place a post within the canal space.
In these situations, the canal is obturated to the apex and the
coronal portion of the canal is left unfilled providing space or
room for a post to be affixed. Note that root canal treatment
(obturation) and post placement (as described above) are two
separate procedures.
[0004] In most instances, complete obturation of the canals is
complicated by the internal shape of the canals. The canals are
generally curved, and often have an irregular cross sectional area
along the length of the canal. Additionally, the canals frequently
have lateral fissures, or passages, that radiate outwardly from the
interior of the canal.
[0005] Accordingly, the filling material and the method used to
obturate the canals must be capable of adequately conforming to the
curved and/or irregular shape of the canals, and to substantially
fill and seal the canals, including the lateral fissures, if the
therapy is to be successful. One prior art endodontic technique
employs silver points in conjunction with a sealer to obturate the
canal passage. The silver point is a relatively slender and
slightly tapered metal insert that, when properly positioned in the
canal, extends to or near the foramen at the apical tip of the
root. Since the silver point generally has a diameter that is less
than the diameter of the canal, the sealer is employed solely to
fill the space between the silver point and the interior surface of
the canal. The sealer is a relatively viscous semi-fluid material
that does not chemically interact with either the silver point or
the tooth material and does not form an adhesive bond with the
silver point or the surrounding tooth material. Instead, the sealer
serves as an interface material between the canal wall and the
silver point to prevent the migration of liquid substances along
the interface region between the tooth and the silver point.
[0006] Although the silver point technique is relatively simple and
may be relatively quickly administered, a principal disadvantage is
that the silver point does not adequately "cork" the apical foramen
to create the desired seal. Further, the technique generally cannot
subject the relatively viscous sealer material to sufficient
hydrostatic pressure to ensure that all of the irregular spaces and
lateral fissures in the interface region are sufficiently filled,
since the sealer is generally incapable of adequately migrating
into either the irregular spaces, or the minute lateral fissures or
accessory canals that radiate outwardly from the root canal
passage. Consequently, the use of silver points in root canal
therapy exhibits a relatively high degree of failure, which often
necessitates the retreatment of the affected tooth.
[0007] Various other prior art endodontic techniques use an elastic
material, called gutta percha, as the filling material. Gutta
percha is a natural rubber material that is semi-rigid at room
temperatures that becomes more plastic, or semi-liquid upon
heating. The gutta percha material is generally formed into
relatively long and slender tapered points that may be introduced
into the root canal by either a vertical condensation or a lateral
condensation method.
[0008] In the vertical condensation method, the gutta percha point
is introduced into the canal with a relatively viscous sealer
applied to the inner surfaces of the canal.
[0009] The point is heated and a relatively small amount of gutta
percha is removed from the canal leaving a softened portion of
gutta perch a within the canal. This portion within the canal is
subjected to vertical compression by a tool called a plugger to
form a relatively densely compressed mass within the canal of the
tooth. The process of heating the point, removing a small portion,
and condensing the remaining portion is repeated two or more times.
This technique thus subjects the gutta percha material to
significant hydrostatic pressure, which forces the sealer and the
softened gutta percha into the small irregularities and accessory
canals found within the root. The condensing process is complete
when the apical three to five millimeters of the canal is sealed
with thermally softened gutta percha that conforms to the irregular
shape of the canal. Another technique called "continuous wave" is
often used where the gutta percha is heated and compressed in a
single down-packing motion, still providing the hydrostatic
pressure as described above and leaving a similar portion of the
gutta percha at the apex for vertical compaction. The next step is
to "back fill" the remaining unfilled portion of the canal. One
common method to accomplish the backfilling procedure is to inject
warm gutta percha material into the canal with a "gutta percha gun"
such as the Obtura system, available from SpartanObtura Inc. of
Fenton, Mo. According to this method, a gutta percha pellet is
inserted into the gun and heated to a predetermined temperature.
The thermally softened gutta percha is expressed in small
increments into the canal through a narrow tip of the gun starting
at the most recently condensed portion of gutta percha. Vertical
condensation then proceeds by compressing the material with the
plugger to compact the gutta percha while it is cooling. The
process of expressing a small amount of gutta percha into the canal
followed by vertical compaction is repeated until the canal is
filled to the desired length.
[0010] An alternative method for obturating the canal space that
entails fewer steps and less equipment than the foregoing method is
to utilize a commercially-available gutta percha carrier unit. The
unit comprises an elongated, axisymmetric plastic portion having a
small handle at one end, and a mass of gutta percha disposed on an
opposing end that extends along a portion of the length of the
plastic portion. In this method, the operator places a sealer into
the canal and, while holding the handle of the unit, heats the
gutta percha on the carrier to soften it. The gutta percha disposed
on the unit is then introduced into the canal. The portion of the
carrier protruding from the tooth is then removed and the root
canal procedure is complete.
[0011] In the lateral condensation method, a main gutta percha
point is introduced into the root canal. A narrow tipped
instrument, known as a spreader, is inserted into the canal along
side of the main gutta percha point. When the instrument is
removed, a space is formed into which another point of gutta percha
is inserted. The spreader is reinserted, followed by the successive
introduction of additional points surrounding the main point until
the root canal is completely filled. As in vertical condensation, a
sealer is used to provide a relatively fluid impermeable interface
between the tooth and the gutta percha material.
[0012] Although the foregoing techniques constitute a substantial
improvement over the silver point technique, numerous drawbacks
still exist. For example, the introduction of gutta percha points
into the canal, either by the vertical or lateral condensation
methods discussed above, is generally time consuming, and requires
a high degree of skill to ensure that the therapy is successful.
For example, in the vertical condensation method, the force applied
to the material must be sufficient to create sufficient hydrostatic
force to compress the gutta percha and sealer into all of the
internal spaces in the canal. However, the application of excessive
force to the gutta percha may cause the tooth to be inadvertently
fractured, or otherwise damaged. In addition, the application of
excessive force to the gutta percha material may cause the
material, or the sealer to be extruded through the apical foramen
and into the surrounding tissue to form an impacted mass of
material that may lead to localized irritation, or even
inflammation of the periapical tissue. Still further, the viscous
sealer employed is generally unable to fully migrate into minute
fissures, or to chemically bond with the tooth or the filler
material, as discussed above.
[0013] Although using the gutta percha carrier unit, as discussed
more fully above, has greatly simplified the process of obturating
the root canal, there are additional drawbacks associated with this
method. With the vertical or lateral condensation techniques, the
main or master cone can be trimmed to size or chemically softened
for proper seating and then radiographed while lodged in the canal
to verify that the proper length has been achieved. This
pre-fitting procedure is accomplished prior to the actual
obturation process, but cannot be performed with the carrier
technique. Consequently, the operator usually has a single
opportunity to heat the gutta percha on the carrier and insert it
into the canal in an attempt to properly seat the gutta percha to
the desired length. Further, when retreatment of a root canal is
required where the canal has been previously obturated with a
carrier unit, the retreatment is more difficult due to the presence
of the plastic carrier, which causes the material to be more
difficult to remove, since the carrier unit may not dissolve in any
of the conventional solvents typically used to remove root canal
filling materials. Accordingly, a significant amount of time may be
expended by the operator in removing and repairing the failed
treatment. If the canal is only filled with gutta percha as in the
vertical or lateral techniques mentioned above, retrieval of the
gutta percha for creation of post space or retreatment of the root
canal is relatively easy.
[0014] Although the use of gutta percha has greatly improved the
success rate of endodontic treatment, this success relies on the
ability of gutta percha to mechanically "plug" the various openings
of the canal, since the sealer does not provide bonding or
chemo-mechanical adherence between the tooth material and the gutta
percha material.
[0015] Chemical bonding agents have been successfully used in
general dentistry for a number of years to bond composite and
porcelain restorations onto and into teeth. Studies have shown that
when such bonding agents are used as filling materials to seal the
coronal portion of canals filled with gutta percha, the bonded area
is impervious to leakage. Accordingly, there is a need in the art
for an apparatus and method for obturating the canal utilizing a
similar bonding agent that will greatly improve the seal of the
canal while generally reducing the time and the relatively high
degree of skill required to perform the procedure.
SUMMARY OF THE INVENTION
[0016] The present invention is directed to an apparatus and method
for obturating a canal in a tooth. In one version of the present
invention, a plug is provided that may be positioned in a canal of
a tooth. The plug is similar in size, shape and flexibility to the
currently available gutta percha and with which dentists are
familiar. Preferably, the plug is formed from a material that
remains resilient even after it is bonded in place. The plug is
optically transparent or translucent. The canal is sealed by
placing a light-cured or dual-cured adhesive and/or composite into
the canal prior to the insertion of the plug. The plug is exposed
to a light source to transmit the light into the canal causing the
adhesive to set.
[0017] In another preferred form of the present invention, a
carrier having an optically translucent or transparent plug portion
is disclosed. A light-cured or dual-cured adhesive is introduced
into the canal and the plug may be softened by heat prior to the
introduction of the carrier into the canal. A light source is used
to cure the adhesive. The carrier may be optically transparent or
translucent.
[0018] In still another example of the invention, a carner having
an optically transparent or translucent plug portion is disclosed.
The plug portion includes an optical fiber that extends through the
plug portion to transmit light from a light source into the
canal.
[0019] In still yet another example of the invention, a plug, or
alternatively, a carrier that includes a plug portion is disclosed
that includes a phosphorescent material that is exposed to light
prior to insertion into the canal. The light-charged plug or plug
portion is inserted into the canal and exposed to a light source to
cure the adhesive.
[0020] In still another version, a plug, or alternatively, a
carrier that includes a plug portion is disclosed that includes a
radioactive isotope that has a relatively-short half-life. The
radioactive emissions from the plug or plug portion activates the
adhesive to set once the plug or plug portion is positioned in the
canal.
[0021] In still another version, a plug, or alternatively, a
carrier that includes a plug portion is disclosed that includes a
base part of a two part bonding system. A catalyst is then applied
to the canal to bond the plug or plug portion to the canal.
Alternatively, the plug or plug portion is formulated to be the
catalyst, and a base compound is applied to the canal.
[0022] Examples of surface contact vinyl addition polymerization in
the health care field include polymerization of methyl methacrylate
bone cement, various acrylate dental resins, and orthodontic no-mix
bracket adhesives. In all of these examples, various
polymethacrylate resin shapes (most commonly beads or fibers but
could easily be other shapes such as cones or long fibers) are
coated with a free radical initiator by shaking the shapes in
benzoyl peroxide powder.
[0023] These shapes are packaged and stored until time of use. Then
they are mixed with a liquid or pressed into paste containing an
activator (usually a tertiary amine such as N,N-dimethyl
paratoluidone). The amine cleaves the benzoyl peroxide at the O--O
bond, creating free radical reactive species which begin the vinyl
addition polymerization at the C.dbd.C sites. These growing polymer
chains capture and polymerize with the polymer shapes forming a
unified, polymerized mass.
[0024] A polymer cone shape (for example methacrylate,
methacrylate-impregnated isobutene rubber, or another
methacrylate-impregnated biologically compatible material) could be
coated with benzoyl peroxide (or another free radical initiator) in
the above referenced manner and when placed into a liquid or paste
environment, which has the proper activator, the polymerization
process would begin and continue to completion. The result would be
the polymerized shape being captured both physically and chemically
by the polymerization process yielding one mass which could be the
root canal filling material.
[0025] In still another example, small particles or pellets of the
same resilient material that is disclosed above are formed of an
optically transparent or translucent material similar in size and
shape as the currently available gutta percha particles that are
inserted in to a gutta percha gun for placement of the optically
transparent or translucent material into the canal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Preferred and alternative examples of the present invention
are described in detail below with reference to the following
drawings:
[0027] FIG. 1 is a plan view of a plug for root canal obturation
according to an embodiment of the invention;
[0028] FIG. 2 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the plug of FIG.
1 according to an embodiment of the invention;
[0029] FIG. 3 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the plug of FIG.
1 according to an embodiment of the invention;
[0030] FIG. 4 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the plug of FIG.
1 according to another embodiment of the invention;
[0031] FIG. 5 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the plug of FIG.
1 according to another embodiment of the invention;
[0032] FIG. 6 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the plug of FIG.
1 according to another embodiment of the invention;
[0033] FIG. 7 is a plan view of a carrier for root canal obturation
according to still another embodiment of the invention;
[0034] FIG. 8 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 7 according to yet another embodiment of the invention;
[0035] FIG. 9 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 7 according to yet another embodiment of the invention;
[0036] FIG. 10 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 7 according to yet another embodiment of the invention;
[0037] FIG. 11 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 7 according to yet another embodiment of the invention.
[0038] FIG. 12 is a plan view of a carrier for root canal
obturation according to still yet another embodiment of the
invention;
[0039] FIG. 13 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 12 according to yet another embodiment of the invention;
[0040] FIG. 14 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 12 according to yet another embodiment of the invention;
[0041] FIG. 15 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal using the carrier of
FIG. 12 according to yet another embodiment of the invention;
[0042] FIG. 16 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal according to an
embodiment of the invention; and
[0043] FIG. 17 is a cross sectional view of a tooth illustrating a
step in a method for obturating a root canal according to an
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0044] The present invention is generally directed to root canal
therapy. More particularly, the invention relates to a method and
apparatus for root canal obturation. Many of the specific details
of certain embodiments of the invention are set forth in the
following description and in FIGS. 1 through 17 to provide a
thorough understanding of such embodiments. One skilled in the art
will understand, however, that the present invention may be
practiced without several of the details described in the following
description. Furthermore, in the following description, an
optically transmissive material will be understood to refer to an
optically transparent or an optically translucent material.
[0045] An optically transparent material will be understood to
refer to a material that is capable of transmitting at least a
portion of the incident radiation applied to the material, and an
optically translucent material will be understood to refer to a
material that is capable of transmitting at least a portion of the
incident radiation applied to the material, while simultaneously
diffusing the radiation as it passes through the material. Still
further, unless otherwise indicated, the terms transparent and
translucent are not to be interpreted as wavelength dependent
properties of the materials. Moreover, in the description that
follows, it is understood that the figures related to the various
embodiments are not to be interpreted as conveying any specific or
relative physical dimension, and that specific or relative
dimensions related to the various embodiments, if stated, are not
to be considered limiting unless the claims expressly state
otherwise.
[0046] FIG. 1 is a plan view of a plug 10 for root canal obturation
according to an embodiment of the invention. The plug 10 is
comprised of an elongated body 1 having a distal end 2 and a
proximal end 3 that may taper from the proximal end 3 towards the
distal end 2 so that the plug 10 may be positioned within the
generally tapered root canal of a tooth with the distal end 2
adjacent to an apical portion of the tooth. The plug 10 may further
be suitably proportioned to fill the root canal in the tooth by
providing a range of sizes that are selectable by an endodontist.
For example, the plug 10 may be manufactured in standardized sizes
or feather tip sizes, or sizes customized to fit a predetermined
taper of currently available endodontic rotary instruments that
vary in overall length, width, degree of taper, or any combination
of length, width and taper, in order to more closely adapt to the
generally unique features of a given root canal.
[0047] The plug 10 may be formed from any flexible and resilient
polymer material that is optically transparent or optically
translucent and suitable for biological implantation. For example,
the plug 10 may be comprised of silicones such as silicon-based
organic polymer polydimethylsiloxane (PDMS) used for medical
implants, polyethylenes, polyurethanes, polytetraflouroethylenes,
polymethylmethacrylates (PMMA) and polytetraflourethyenes (PTFE)
and related thermoplastic polymers, among other materials.
[0048] In a particularly preferred version of the invention, the
plug is formed from a material that is resilient in its initial
state upon insertion into the tooth and retains its resilient
quality after being bonded with the tooth. Some of the above
materials are suitable for use in this preferred version. In one
example, the plug is formed from a polymethylmethacrylate, and more
particularly from butyl methacrylate polymer (BMA-P) blended with
butyl methacrylate monomer (BMA-M) creating a curable composition
known as Talon as described in U.S. Pat. Nos. 5,646,216 and
5,328,362. One suitable commercially available form of butyl
methacrylate is sold under the name Talon in a liquid form that can
be poured or injected into a mold and cured to form the plug in the
desired shape. The resulting plug is clear and resilient, and
nonporous. The plug can further be trimmed or heat-softened and
shaped in order to better match the plug to the shape of the
opening it is intended to fill.
[0049] The plug 10 may also include compounds that augment the
opacity of the plug 10 when the plug 10 is subjected to
radiographic examination. Accordingly, radio-opacifiers comprised
of compounds of barium or bismuth may be used, although other
suitable radio-opacifiers are known in the art. The plug 10 is
formulated to be generally compatible with numerous light-curing
adhesive compounds or dual-curing compounds to allow the plug 10 to
be chemically bonded to an interior surface of a root canal upon
exposure of the plug 10 to a light source. In this sense, "bonded"
does not mean merely held in place, but rather a chemical
alteration of at least a portion of the plug in order to bond the
plug to the surface of the root canal. Accordingly, the
light-curing adhesive may include self-etching self-adhering resin
polymers, light activated methylacrylate resins such as iBond
(obtained from Heraeus Kulzer), glyceroldimethylacrylate dihydrogen
phosphate (GPDM) such as Maxcem (obtained by Kerr Dental),
acrylics, cyanoacrylates, and silicones that are light curing
and/or dual-curing, although other compounds may also be used.
Bonding the plug 10 to the interior surface of the root canal will
be discussed in greater detail below.
[0050] FIGS. 2 through 6 are cross sectional views of a tooth 22
that show the steps in a method for obturating a root canal 26 in
the tooth 22 with a plug 10 according to an embodiment of the
invention. In FIG. 2, the tooth 22 has been endodontically prepared
for root canal obturation by first removing a portion of the crown
23 to form an access opening 24. The access opening 24 permits
canal contents (not shown) to be removed from the tooth 22, and to
expose the interior portions of the root canals 26. The root canals
26 are then commonly subjected to numerous mechanical shaping
operations, 10 including reaming or filing to obtain a root canal
26 with relatively long and slowly tapering walls 28. Prior to the
introduction of obturation material into the canals 26, the canals
26 are regularly irrigated with cleaning or etching solutions to
remove residual pulpal material and any dentin debris from the
tooth 22 during the mechanical shaping of the canals 26.
[0051] Still referring to FIG. 2, the plug 10 is placed in the root
canal 26 with the distal end 2 (as shown in FIG. 1) positioned
adjacent to an apical foramen 29 of the tooth 22. The position of
the plug 10 may be examined by radiographic techniques, such as
x-ray imaging, to ensure that the plug 10 properly extends to or
near the apical foramen 29. The plug 10 may be trimmed with
scissors or softened with heat, chloroform or other suitable
solvents to conform to the contour of the canal 26. When it has
been determined that the plug 10 is properly proportioned for the
canal 26, and the canal 26 has been thoroughly dried, etched, and
primed, a light-curing adhesive or dual-curing adhesive may be
applied to the walls 28 of the root canal 26, and the plug 10 is
repositioned within the root canal 26. Alternatively, the adhesive
may also be applied directly to the plug 10 prior to positioning
the plug 10 into the root canal 26.
[0052] The light-curing adhesive is a relatively low viscosity
adhesive material that may be primarily composed of a blend of
monomers, oligomers, and polymers containing the acrylate
functionality, with photoinitiators having the appropriate light
sensitivity added to the blend. Upon exposure to light of the
proper intensity and spectral output, the photoinitiator in the
adhesive decomposes to yield free radicals, which then initiate
polymerization of the adhesive through the acrylate groups to
create a thermoset polymer. The light-curing adhesive may have a
viscosity in the range of at least about 0.5 centipoise (cP) to at
least about 1.5 cP. An example of a suitable light-curing adhesive
is the PRIME & BOND NT light-polymerizable dental adhesive
available from the L. D. Caulk Division of Dentsply International,
Inc. of York, Pa. Another preferred dual-curing adhesive is
commercially available under the name Maxcem, although other
alternatives may exist. The plug 10 may be subjected to a slight
positioning force to ensure that the plug 10 is properly seated in
the root canal 26. Turning now to FIG. 3, a light source 31
produces light 34 at a wavelength that activates the light-curing
or dual-curing adhesive to bond the plug 10 to the walls 28 of the
root canal 26. In one version in which the plug 10 is comprised of
a transparent or translucent material, the light 34 is transmitted
through the material and along the length of the plug 10 to
activate the light-curing or dual-curing adhesive interposed
between the walls 28 of the root canal 26 and the plug 10. The plug
10 is thus positionally fixed and sealably secured by way of the
light curing adhesive in the root canal 26. An example of a
suitable light source 31 that is commonly employed by dentists is
the SPECTRUM 800 curing light, which is available from the L. D.
Caulk Division of Dentsply International, Inc. of York, P A.
Alternatively, the light source 31 may be comprised of other
sources of illumination that provide light at various wavelengths,
or a collimated light source such as a laser that is coupled to an
optical fiber to transmit the light 34 to the upper portion 32 of
the plug 10 may be used.
[0053] Still referring to FIG. 3, after the plug 10 has become
positionally fixed and sealably secured in the canal 26, the upper
portion 32 projecting upwardly from the plug 10 may be removed with
a burr attached to a hand piece (not shown), or by thermally
severing the upper portion 32 with a heated probe (also not shown),
or by still other means to form a generally smooth terminal surface
40, at an upper end of the root canal 26, as shown in FIG. 4.
[0054] When the plug is formed from the preferred resilient
materials or other substitutes as described above, the plug retains
its resilient qualities even after being bonded in place in the
canal. This resilient quality is particularly advantageous in the
event the plug must be removed or replaced for some reason. Using
some conventional root canal techniques, the canal is filled with a
material that is extremely hard, and typically at least as hard as
dentin. Consequently, they are extremely difficult to remove,
requiring lengthy and tedious drilling. By contrast, a plug in
accordance with the present invention may be far more easily
removed to allow access, replacement, or other procedures as may be
necessary.
[0055] Referring to FIG. 4, additional root canals 26 present in
the tooth 22 may be obturated by positioning a plug 10 into the
canal 26 through the opening 24, as previously described. The plug
10 may then be positionally fixed and sealably secured to the wall
28 of the root canal 26 by exposing an upper portion 50 of the plug
10 to the light 34 to cure the adhesive, as shown in FIG. 5. The
upper portion 50 may then be removed so that a smooth terminal
surface 60 is formed, as shown in FIG. 6. An alternative 5 approach
that may be used to achieve the foregoing is to deposit the
adhesive into each canal of the tooth having multiple canals,
followed by placement of the plugs 10 into each canal. The plugs 10
may then be simultaneously exposed to the light 34 to seal all the
canals 26 at the same time. In either case, following the
obturation of all of the root canals 26 present in the tooth 22,
the opening 24 may be restored by any conventional method 10
presently used in dentistry.
[0056] In still another embodiment of the invention, the plug 10
and the adhesive compound may form complementary parts of a
two-part bonding system. With reference still to FIGS. 1 through 6,
the plug 10 may be comprised of a base component of the two-part
system, while a relatively low viscosity catalyst component that
activates the bonding 15 properties of the base component is
applied to the wall 28 of the root canal 26. Since the bond between
the plug 10 and the root canal surfaces is formed without the use
of a light-curing bonding compound, it is not necessary to expose
the plug 10 to a light source, as shown in FIGS. 3 and 5. In
addition, a "dual cure" adhesive system that contains a
photocatalyst to aid curing may also be used that would permit the
plug 10 and the adhesive to cure chemically and by exposure to
light.
[0057] In yet another embodiment of the invention, the plug 10 may
include a phosphorescent material capable of producing
photoluminescence within the plug 10 after exposure of the plug 10
to an external source of light for a predetermined period of time.
The photoluminescence of the plug 10 thus provides the light
necessary to cure the previously-applied light-curing adhesive.
Accordingly, the plug 10 may include various organic or inorganic
compounds that are capable of phosphorescence. For example, various
formulations comprised of anhydrous zinc sulfide and/or calcium
tungstate may be used, which are commercially available as LUMILUX
luminescent pigments from Allied Signal Specialty Chemicals, Inc.
of Morristown, N.J. Since the photoluminescence produced by the
phosphorescent material generally has a characteristic rate of
decay after the external light source is removed, the
photoluminescence must generally persist for a length of time that
is sufficient to allow the plug 10 to be positioned within the root
canal 26 after excitation of the luminescent material by the
external light source, and to permit the light-curing bonding
compound to be completely activated.
[0058] In yet still another embodiment of the invention, the plug
10 may include a radioisotope having a short half-life that
activates a bonding compound distributed on the root canal wall 28
by exposing the bonding compound to alpha or beta decay, or through
the emission of gamma radiation from the radioisotope in the plug
10.
[0059] The foregoing embodiments advantageously permit a root canal
to be more reliably obturated than heretofore possible by using a
relatively low viscosity adhesive material with the optically
transmissive plug. Since the adhesive material is capable of
migrating into lateral fissures and chemically bonding to the tooth
and the plug material, a dentist will be able to produce a more
reliable root canal obturation in generally less time than the
prior-art gutta percha condensation methods currently require.
Moreover, a dentist will be able to perform a root canal obturation
in fewer steps with the foregoing embodiments than was heretofore
possible. Thus, dentists with less general experience in root canal
obturation will be able to routinely perform root canal obturations
that have a higher probability of success than was previously
obtainable. Still further, the disclosed method may be practiced
with dental equipment that is commonly available in the dentist's
office. For example, light-curing resins are commonly used in a
variety of dental procedures so that suitable light sources to cure
the resins are also generally present.
[0060] FIG. 7 is a plan view of a carrier 70 for root canal
obturation according to still another embodiment of the invention.
The carrier 70 includes a plug portion 71 having a distal end 72
and a proximal end 73 that may taper from the proximal end 73
towards the distal end 72 so that the plug portion 71 may be
positioned within the generally tapered root canal of a tooth. The
plug portion 71 may be formed from any optically transparent or
translucent polymer suitable for biological implantation, which may
include any of the materials previously identified in connection
with other embodiments of the invention. The plug portion 71
further includes a central support portion 77 that is mostly
embedded in the plug portion 71, which extends from the plug
portion 71 to a handle 78. This support may be optically
transparent or translucent allowing better penetration of light
from the curing light source.
[0061] FIGS. 8 through 10 are cross sectional views of a tooth 22
that show the 5 steps in a method for obturating a root canal 26 in
a tooth 22 with the carrier 70 according to another embodiment of
the invention. For brevity, the following method will be described
as applied to a single root canal. It is understood, however, that
there may be more than a single root canal in a tooth, and that the
method described below may be applied in succession to each of the
root canals in the tooth. Referring now to FIG. 8, the 10 plug
portion 71 is introduced through the opening 24 and positioned in
the root canal 26 by manual manipulation of the carrier 70. As
previously described, the position of the plug portion 71 may be
radiographically imaged to ensure that the plug portion 71 properly
extends to the apical foramen 29 of the tooth 22. When it has been
determined that the plug portion 71 is properly positioned in the
canal 26, the plug portion 71 may be withdrawn from the canal 26,
and a relatively low viscosity light-curing or dual-curing adhesive
may then be applied to the walls 28 of the root canal 26. The
adhesive may alternatively be applied directly to the plug portion
71 prior to positioning the plug portion 71 into the root canal 26.
The knob 78 may be used to manipulate the carrier 70 and to apply
slight positioning forces to the carrier 70 to properly seat the
plug portion 71 in the root canal 26, 20 as shown in FIG. 9. As
previously described, the plug portion 71 may optionally be
softened by heating the plug portion 71 with an external thermal
source before insertion into the canal, allowing the plug to more
accurately fit within the canal. Turning now to FIG. 10, the plug
portion 71 of the carrier 70 may be exposed to light 34 from a
light source 31 to provide illumination for activation of the
adhesive. When the adhesive has been fully cured, the central
support portion 25 77 and the handle 78 of the carrier 70 may be
severed from the plug portion 71 using a burr mounted in a hand
piece, or by other means, to leave the plug portion 71 positioned
in the canal 26, as shown in FIG. 11. A portion of the carrier 77
will remain within the plug portion that is imbedded within the
canal.
[0062] FIG. 12 is a plan view of a carrier 80 for root canal
obturation according to still yet another embodiment of the
invention. The carrier 80 includes a plug portion 81 having a
distal end 72 and a proximal end 73 that may taper from the
proximal end 73 towards the distal end 72 so that the plug portion
81 may be positioned within the generally tapered root canal of a
tooth. The plug portion 81 may be formed from any optically
transparent or translucent polymer, as discussed in connection with
the previous embodiment. The plug portion 81 further includes an
optical fiber 82 that extends from a handle 78 and along a central
support portion 83 having an open interior 84 and into the plug
portion 81. The optical fiber 82 is comprised of an optically
transparent polymeric material having generally a higher rigidity
than the material comprising the plug portion 81 so that the
optical fiber 82 may act cooperatively with the central support
portion 83 and the knob 78 to guide and properly position the plug
portion 81 in the root canal of a tooth. An example of an optical
fiber 82 that is suitable for use in this embodiment is the
LUMILEEN polymethyl methacrylate (PMMA) optical fiber material
available from PolyOptical, Inc. (Irvine Calif., although other
suitable alternatives exist.
[0063] Still referring to FIG. 12, the carrier 80 may be coupled to
a light source 15 31 through a fiber optic cable 85. The light
source 31 may include an incandescent light source, although other
sources of light may be used. For example, a coherent light source,
such as a laser may also be used.
[0064] FIGS. 13 through 15 are cross sectional views of a tooth 22
that show the steps in a method for obturating a root canal 26 in a
tooth 22 with the carrier 80 according 20 to still yet another
embodiment of the invention. For brevity, the following method will
be described as applied to a single root canal. Referring now to
FIG. 13, the plug portion 81 is introduced through the opening 24
and positioned in the root canal 26 by manual manipulation of the
carrier 80. As previously described, the position of the plug
portion 81 may be radiographically imaged to ensure that the plug
portion 81 properly extends to the apical foramen 29 of the tooth
22. When it has been determined that the plug portion 81 is
properly positioned in the canal 26, the plug portion 81 may be
withdrawn from the canal 26, and a relatively low viscosity
light-curing or dual-curing adhesive may then be applied to the
walls 28 of the root canal 26. The adhesive may alternatively be
applied directly to the plug portion 81 prior to positioning the
plug portion 81 into the root canal 26. The knob 78 may be used to
manipulate the carrier 80 and to apply slight positioning forces to
the carrier 80 to properly seat the plug portion 81 in the root
canal 26. As previously described, the plug portion 81 may
optionally be softened by heating the plug portion 81.
[0065] Turning now to FIG. 14, a light source 31 is activated to
transmit light 5 from the source 31 to the carrier 80 along a fiber
optic cable 85. Light is then propagated along the optical fiber 82
(as shown in FIG. 12) and dispersed within the plug portion 81 to
provide illumination for activation of the light-curing adhesive.
The central support portion 83 and the handle 78 of the carrier 80
may then be severed from the plug portion 81 using a burr mounted
in a hand piece, or by other means, as shown in FIG. 15.
[0066] In addition to the advantages described previously, the
foregoing embodiments advantageously permit the plug portion to be
more conveniently manipulated and positioned within the canal.
Moreover, the fiber optic element positioned within the plug
advantageously permits a greater and more uniform level of
illumination to be achieved within the plug portion since the
optical fiber extends relatively deeply into the root canal, which
further assists the light-curing adhesive to cure.
[0067] FIGS. 16 and 17 are cross sectional views of a tooth 22 that
show the steps in a method for obturating a root canal in the tooth
22 according to still yet another embodiment of the invention.
Referring now to FIG. 11, a filler material 100 is introduced into
the root canal 26 in a flowable or semi-liquid form by a thermal
heating device 101 that dispenses the filler material 100 through a
filler tube 102 that is inserted through the opening 24 in the
tooth 22. One suitable thermal heating device 100 is the Obtura IT
gutta percha gun, available from Spartan/Obtura, Inc. of Fenton,
Mo. Prior to the introduction of the material into the canal 26, a
relatively low viscosity light-curing adhesive is applied to the
walls 28 of the root canal 26. The filler material 100 may be
comprised of any optically transparent or translucent polymer
suitable for biological implantation, which may include any of the
materials previously identified in connection with other
embodiments of the invention. The plug or filler material 100 may
be supplied to the thermal heating device 101 in a solid form,
which may include particles or bead-like pellets of the material
100, in addition to other shapes. The material 100 is melted by the
heat generated within the device 101 to form a flowable, plastic
material 100 which may be also be pressurized by the device 101 so
that the material 100 may be expelled from the device 101 through
the filler tube 102 and into the root canal 26. This embodiment
also allows for the "back-filling" step following the vertical
condensation technique.
[0068] Turning now to FIG. 17, following the solidification of the
material 100 within the root canal 26, light 34 emitted from a
light source 31 may be introduced through the opening 24 to expose
the material 100. The light 34 is transmitted along the length of
the material 100 and activates the adhesive previously applied to
the walls 28 of the root canal 26. The material 100 is thus
adhesively fixed and sealably secured within the root canal 26.
After the material returns to body temperature, it remains
resilient, thus allowing for its removal as is similar to the plug
disclosed in the invention.
[0069] While the preferred embodiment of the invention has been
illustrated and described, as noted above, many changes can be made
without departing from the spirit and scope of the invention.
Accordingly, the scope of the invention is not limited by the
disclosure of the preferred embodiment. Instead, the invention
should be determined entirely by reference to the claims that
follow.
* * * * *