U.S. patent application number 09/862544 was filed with the patent office on 2002-01-24 for electrosurgical tool for tissue coagulation in vital pulp therapy.
Invention is credited to Livaditis, Gus J..
Application Number | 20020009687 09/862544 |
Document ID | / |
Family ID | 24500718 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009687 |
Kind Code |
A1 |
Livaditis, Gus J. |
January 24, 2002 |
Electrosurgical tool for tissue coagulation in vital pulp
therapy
Abstract
An electrosurgical tool for coagulating a tissue layer is
disclosed, having a hand piece with an electrical coupling at one
end and a head mounting a bipolar coaxial electrode at the other
end. The electrode is rotatable about its long axis and has an end
face where the two poles of the electrode are exposed. The end face
is asymmetrically arranged with respect to the long axis and allows
the same tool to be used to coagulate exposed pulp on opposite
tooth faces by manually rotating the electrode. An electrosurgical
unit connected to the electrical coupling powers the tool.
Electrodes are interchangeable and may be straight or curved and
have a dome-shaped or cut-back end face.
Inventors: |
Livaditis, Gus J.; (York,
PA) |
Correspondence
Address: |
John A. Chionchio, Esquire
Synnestvedt & Lechner LLP
Aramark Tower
1101 Market Street, Suite 2600
Philadelphia
PA
19107-2950
US
|
Family ID: |
24500718 |
Appl. No.: |
09/862544 |
Filed: |
May 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09862544 |
May 22, 2001 |
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09624116 |
Jul 24, 2000 |
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6319007 |
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Current U.S.
Class: |
433/32 ;
433/224 |
Current CPC
Class: |
A61B 2018/00589
20130101; A61C 5/40 20170201; A61B 18/1402 20130101 |
Class at
Publication: |
433/32 ;
433/224 |
International
Class: |
A61C 005/02; A61C
003/00 |
Claims
What is claimed is:
1. An electrosurgical tool for use with an electrosurgical power
unit for coagulating a tissue layer, said tool comprising: an
elongated hand piece having a butt end and a head oppositely
disposed; an electrical coupling mounted on said butt end and
adapted to connect electrically to said electrosurgical power unit;
an electrically conductive pathway arranged lengthwise along said
hand piece and connected to said electrical coupling; and an
elongated electrode mounted on said head and connected to said
electrically conductive pathway, said electrode being rotatable
about its long axis and oriented at an angle relatively to said
hand piece.
2. A tool according to claim 1, wherein said electrode is a bipolar
electrode having first and second electrode poles.
3. A tool according to claim 2, wherein said electrode is a coaxial
electrode having said first electrode pole coaxially surrounded by
said second electrode pole, an insulating layer being coaxially
positioned between said first and said second poles.
4. A tool according to claim 3, wherein said electrode has an end
face positioned distally to said head, said end face being formed
by extending said first electrode pole lengthwise beyond said
second electrode pole, said end face being oriented at an angle
relatively to said long axis.
5. A tool according to claim 4, wherein said end face is oriented
at an angle between about 15.degree. to about 45.degree. to said
long axis.
6. A tool according to claim 4, wherein said electrode is curved,
thereby orienting said end face at said angle to said long
axis.
7. A tool according to claim 3, wherein said electrode has an end
face positioned distally to said head, said end face comprising a
cut-back region formed by removing a lengthwise portion of said
second pole and said insulating layer along one side of said
electrode to expose said first pole along a portion of said one
side.
8. A tool according to claim 7, wherein said electrode is curved
about a center of curvature, said electrode having a convex side
facing away from said center of curvature and a concave side facing
toward said center of curvature.
9. A tool according to claim 8, wherein said cut-back region is
positioned on said convex side of said electrode.
10. A tool according to claim 8, wherein said cut-back region is
positioned on said concave side of said electrode.
11. A tool according to claim 1, wherein said electrode is oriented
substantially at a right angle relatively to said hand piece.
12. A tool according to claim 1, wherein said hand piece comprises
a neck portion positioned adjacent to said head, and a grip portion
positioned between said neck portion and said butt end, said neck
portion being oriented at an angle relatively to said grip
portion.
13. A tool according to claim 12, wherein said neck portion is
oriented at an angle between about 20.degree. and about
30.degree..
14. A tool according to claim 12, wherein said neck portion is
oriented at an angle of about 25.degree..
15. A tool according to claim 1, wherein said head is pivotally
mounted on said hand piece for pivoting motion about an axis
substantially perpendicular to both said hand piece and said
electrode.
16. A tool according to claim 1, wherein said head further
comprises a socket sized to receive said electrode for mounting
said electrode on said head, said socket having electrical contacts
positioned therein connecting said electrode to said electrically
conductive pathway.
17. A tool according to claim 16, wherein said head further
comprises a plurality of said sockets.
18. A tool according to claim 17 wherein said sockets are oriented
angularly with respect to one another, said electrode being
engageable with any one of said sockets to orient said electrode
angularly with respect to said head.
19. An electrosurgical tool for use with an electrosurgical power
unit for coagulating a tissue layer, said tool comprising: an
elongated hand piece having an electrical coupling positioned at
one end and a socket at the other end, said electrical coupling
being adapted to connect electrically to said electrosurgical power
unit, said socket having a pair of electrical contacts therein; an
electrically conductive pathway extending lengthwise along said
hand pieced connecting said contacts to said electrical coupling;
and an elongated coaxial bipolar electrode sized to interfit within
said socket and engage said contacts, said electrode being oriented
at an angle to said hand piece and comprising a first electrode
pole coaxially surrounded by a second electrode pole, an insulating
layer being coaxially positioned between said first and said second
poles, said electrode being rotatable about its long axis within
said socket and having an end face positioned distally to said
socket and arranged asymmetrically with respect to said long
axis.
20. A tool according to claim 19, wherein said socket is located
within a body of resilient, flexible insulating material attached
to said other end of said hand piece, said socket being sized
smaller than said electrode to provide an interference fit
therebetween so as to removably retain said electrode within said
socket and allow said electrode to rotate about said long axis.
21. A tool according to claim 19, further comprising a plurality of
said sockets positioned at said other end, said sockets being
angularly oriented relatively to one another for orienting said
electrode angularly with respect to said hand piece when received
within one of said sockets.
22. A tool according to claim 19, wherein said end face is formed
by extending said first electrode pole lengthwise beyond said
second electrode pole.
23. A tool according to claim 22, wherein said electrode is curved,
thereby orienting said end face asymmetrically with respect to said
long axis.
24. A tool according to claim 19, wherein said end face comprises a
cut-back region formed by removing a lengthwise portion of said
second pole and said insulating layer along one side of said
electrode to expose said first pole along a portion of said one
side.
25. A tool according to claim 19, wherein said electrode has a
diameter between about 18 and about 23 gage.
Description
RELATED APPLICATION
[0001] This is a continuation-in-part of U.S. application Ser. No.
09/624,116, filed Jul. 24, 2000.
FIELD OF THE INVENTION
[0002] The present invention is directed to an apparatus for
providing hemostasis of dental pulp. In particular, the present
invention is directed to an electrosurgical coagulation tool which
provides durable hemostasis to exposed dental pulp with little or
no damage to the pulp.
A. The Anatomy of the Tooth
[0003] Teeth, both primary and permanent, consist of outer enamel,
an inner layer of dentin, and a soft tissue component referred to
as the dental pulp. The pulp is enclosed by dentin, is continuous
with soft tissue in the tooth socket, begins at the tip of the
root, traverses through each root and terminates in the pulp
chamber of the coronal or visible portion of the tooth. Initially,
the dental pulp is responsible for the development of the enamel
and dentin and later continues to provide the blood supply, nerve
enervation and lymphatic drainage. The pulp responds to insult by
depositing reparative and secondary dentin to protect the pulp and
initiates an inflammatory process to combat bacterial
infection.
B. Injury to the Pulp
[0004] The tooth and pulp are typically threatened in a variety of
ways: (1) fracture of the tooth exposing the pulp to bacteria
normally present in the oral cavity; (2) dental caries (decay)
which decalcifies enamel and dentin, exposes the pulp and allows
ingress of bacteria and bacterial products, (3) dental restorative
procedures which may inadvertently expose the pulp; and (4) failure
of dental restorations through fracture or leakage, including
microleakage, allowing bacteria or bacterial by-products to reach
the pulp. For decades many factors have been blamed for causing
inflammation and necrosis (i.e., non-vitality, death) of the dental
pulp, including: (1) dental caries and associated bacteria being
the most prominent; (2) fracture and exposure to bacteria; (3)
excess heat from dental instrumentation; and (4) toxicity of dental
materials. More recently, bacterial invasion via microleakage has
been attributed as an important cause of pulpal inflammation and
necrosis.
[0005] Traditionally, when a small exposure of the pulp occurred
mechanically, by fracture of the tooth, or while excavating caries,
the exposure was promptly `capped` with various dental materials in
an attempt to prevent inflammation or necrosis of the pulp. If the
exposure was small and capping occurred immediately and with a
suitable material, pulpal necrosis could be averted. However, if
the exposure was moderate or large in size, or if capping occurred
after bacteria developed a foothold, or if the capping material
deteriorated leading to microleakage, then inflammation or necrosis
would typically occur. Materials (e.g., calcium hydroxide) which
stimulated reparative dentin formation were used for capping of the
pulp for over half a century in an attempt to stimulate health and
to restore the pulpal wall naturally via slow deposition of
reparative dentin.
C. Treatment Methods for Exposed Pulp
[0006] If the pulp progressed to necrosis, only two options were
available to the patient: (1) extraction of the tooth; or (2)
extirpation of the necrotic pulp and filling of the pulpal space
with a suitable material to prevent microleakage via the pulp space
to the surrounding bone. This second alternative is referred to as
endodontic therapy (root canal treatment). Inflamed vital dental
pulps, however, represent a substantial portion of infected pulps.
Additionally, pulps exposed intentionally for therapeutic purposes
(e.g., to support a denture) also constitute a significant portion.
These latter two groups are currently relegated to extraction or
endodontic therapy despite their vitality. Inflamed but vital pulps
are considered, under current clinical guidelines, to be
untreatable. Even teeth with relatively mild symptoms are diagnosed
as "irreversible pulpitis" and condemned to extraction or
endodontic therapy.
[0007] Over the past seven decades, the research primarily centered
around the stimulation of reparative dentin deposition and pulp
therapy was limited to small exposures on asymptomatic teeth. A few
reported exceptions involved more aggressive pulp therapy but was
limited to adolescent and young adult patients. Several
developments in the field opened the possibility of more
comprehensive pulp therapy. These included: (1) The realization
that most pulpal inflammation is due to bacteria invasion and
bacterial by-products occurring via microleakage and less due to
toxicity of dental materials; and (2) The development of materials
that adhere to dentin and which can produce a seal to prevent
microleakage (i.e., dentin adhesion products and the ability to
create a hybrid layer consisting of collagen and resin). The
ability to stimulate the deposition of reparative dentin became a
standard for demonstrating re-organization and healing of the pulp
after an insult. Despite these developments, only teeth with small
exposures or mild clinical symptoms were routinely treated while
the great majority of teeth exhibiting pulpal inflammation or
periapical inflammation (inflammation of a pulpal origin in the
bone around the tip of the root) were treated with endodontic
therapy or extraction of the tooth.
[0008] One of the obstacles in treating the pulp is the impact of
bleeding on the formation of the pulp barrier (sealing of the pulp
or the restoration of the missing pulpal wall). Bleeding during any
surgical procedure can impact on the success of treatment ranging
from (1) being a mere nuisance or compromising visibility to (2)
creating a toxic reaction (as in neurosurgery). Bleeding around the
retina during eye surgery, for example, is an important concern. In
pulp therapy, bleeding compromises visibility, jeopardizes the
dentin adhesion and creates voids or tracts within the barrier
material resulting in chronic irritation and failure of the pulp
therapy. In a very common situation, pulp therapy cannot be
instituted because the hemorrhaging cannot be controlled. In these
cases, the teeth are relegated to endodontic therapy or extraction
simply due to the uncontrolled bleeding. One might wonder why
bleeding cannot be controlled in an exposure approximately 2-4
square mm in area and consisting of very small blood vessels when
bleeding is routinely controlled in major surgical procedures where
much larger vessels are involved. A good analogy can be made with
ophthalmic surgery where even minor amounts of bleeding during the
procedure can compromise the overall therapeutic effort. In pulp
therapy, minor bleeding contaminates the surface of the dentin
preventing adhesion of the pulp barrier and jeopardizing the
valuable dentinal seal. Residual blood clots have been reported to
prevent healing and even stimulate an inflammatory response by the
release of chemotaxic components.
[0009] Another important dilemma is that the bleeding must be
controlled with little or no injury to the remaining pulp tissue.
Furthermore, hemostatic procedures and materials which do not
impact on the highly technique-sensitive dentinal adhesion process
must be selected. These two factors place severe restrictions on
the ability to control bleeding. Furthermore, temporary hemostasis
is not sufficient since numerous procedures are required to create
the pulp barrier and final restoration--any of which can cause
recurring bleeding at a critical moment. Therefore, durable
hemostasis is required with minimal or no injury (especially
lasting injury) to the pulp. The present invention provides an
apparatus which satisfies the need in the art for durable
hemostasis.
Reported Developments
[0010] Most efforts in controlling bleeding of the pulp involved
application of a cotton pellet and light pressure until
hemorrhaging ceased. This proved fairly effective with very small
exposures but was ineffective with larger exposures or hyperemic
pulps. Over the past century, pulpotomy procedures were quite
common upon exposure of the pulp. Pulpotomy procedures typically
remove the chamber portion of the pulp (the part of the pulp
enclosed by the clinical crown, the visible portion of the tooth,
as opposed to the pulp tissue contained within the root portion).
This allowed control of bleeding at the more constricted portion of
the pulp which was easier to accomplish. However, it meant
sacrificing a substantial segment of vital pulp tissue. This
approach is still quite common in children's primary teeth.
[0011] Numerous vasoconstricting (blood vessel contracting)
medicaments and even necrotizing materials have been used partly
for hemorrhage control and partly for therapeutic purposes. More
recently, with greater attention to gentle treatment of the pulp,
the selection of materials or medicaments were directed at
hemorrhage control with minimal effect on the pulp tissue and with
minimal impact on the dentin adhesion procedures. Sodium
hypochlorite (2-5%) has been advocated for use in this manner. The
present state of the art in pulpal hemostasis consists of: (1)
cotton pellet--dry, moist with water, or moist with saline; (2)
Sodium hypochlorite (2-5%) applied and rinsed; or (3) failing to
achieve hemostasis--referral for endodontics or extraction.
[0012] Monopolar electrosurgery uses an active electrode which is
very small in dimension compared to the grounding electrode
(referred to as the dispersive electrode). The applied power
concentrates the current at the narrow point or blade of the active
electrode. When sufficiently high, the current is released to the
less conductive tissue via direct contact or as a spark that jumps
to the tissue. The intense heat that is generated by this sequence
of events, which occurs thousands of times per second, coagulates
the tissue next to the active electrode. With the monopolar mode,
the current then dissipates through the body of the patient via a
path of least resistance to the dispersive electrode. Serious
consequences have been reported associated to this dispersive path.
In particular, there is the potential for necrosis of the pulp,
never before realized in dentistry and identified by the inventor,
due to a channeling effect of the dissipating current passing
through a constriction of the tissue. Monopolar electrosurgery has
been used in pulp therapy to fulgurate the pulp. Fulguration is the
destruction or ablation of tissue caused by delivering a high
frequency electrosurgical current. An electrode is applied a short
distance from the tissue and a series of high intensity sparks are
caused to jump from the electrode to the tissue causing ablation of
the tissue. Fulguration was used much like formocresol, silver
nitrate and other materials to coagulate, necrotize, cauterize,
etc., a layer of tissue or the entire pulp. Fulguration also
provided hemostasis although it is not clear whether it was ever
used solely for hemostasis. Fulguration was shown to adversely
affect the pulp and tissue surrounding the tooth. The hazards of
using monopolar electrosurgery on the dental pulp or near metallic
restorations in the tooth, has been reported in a number of
publications. These hazards are related to the monopolar mode of
electrosurgery, and accordingly, monopolar electrosurgery is
contraindicated for use on or near the dental pulp.
SUMMARY OF THE INVENTION
[0013] The apparatus concerns an electrosurgical tool for use with
a bipolar electrosurgical power unit for coagulating a tissue
layer, for example, exposed pulp of a tooth. The tool has an
elongated hand piece with a butt end and a head oppositely
disposed. An electrical coupling is mounted on the butt end and
adapted to connect electrically to the electrosurgical power unit.
An electrically conductive pathway is arranged lengthwise along the
hand piece and is connected to the electrical coupling. An
elongated electrode is mounted on the head and connected to the
electrically conductive pathway, the electrode being rotatable
about its long axis and oriented at an angle relatively to the hand
piece.
[0014] Preferably, the electrode is a coaxial bipolar electrode
having a first electrode pole coaxially surrounded by a second
electrode pole, an insulating layer being coaxially positioned
between the first and the second poles. The electrode has an end
face positioned distally to the head and asymmetrically arranged
with respect to the long axis of the electrode. In one embodiment,
the end face is formed by extending the first electrode pole
lengthwise beyond the second electrode pole, the end face being
oriented at an angle, asymmetrically relatively to the long axis by
curving the electrode. In another embodiment, the end face is a
cut-back region at the tip of the electrode formed by removing a
lengthwise portion of the second pole and the insulating layer
along one side of the electrode to expose the first pole along a
portion of the one side.
[0015] Preferably, the head has a socket sized to receive the
electrode for mounting it on the head, the socket having electrical
contacts positioned therein, connecting the electrode to the
electrically conductive pathway. The socket has a diameter smaller
than the electrode to provide an interference fit to frictionally
retain the electrode and allow it to rotate about its long axis but
also retain its set position against light contact of the end face
with a surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a side view of an electrosurgical tool according
to the invention;
[0017] FIG. 2 is a detailed sectional view of a portion of the
tool;
[0018] FIG. 3 is a perspective view of the tool in use;
[0019] FIG. 4 is a detailed sectional view of a portion of the
tool;
[0020] FIG. 5 is a perspective view of a portion of the tool
illustrating an alternate embodiment;
[0021] FIG. 6 is a side view of a component of the tool;
[0022] FIG. 7 is a view of the component shown in FIG. 6 taken
along lines 7-7;
[0023] FIG. 8 is a side view of a component of the tool;
[0024] FIG. 9 is a view of the component shown in FIG. 8 taken
along lines 9-9;
[0025] FIG. 10 is a side view of a component of the tool;
[0026] FIG. 11 is a view of the component shown in FIG. 10 taken
along lines 11-11;
[0027] FIG. 12 is a sectional view of a component of the tool;
and
[0028] FIG. 13 is a graph used to determine the optimal time and
power settings for coagulation.
DETAILED DESCRIPTION OF THE INVENTION
A. Introduction
[0029] The methods and apparatus of the present invention relate to
bipolar electrocoagulation to preserve and restore the health of
the dental pulp. While procedures for preserving the health of the
dental pulp are currently available, the present invention expands
this capability to teeth with larger pulp exposures which were
heretofore not amenable to pulp therapy. Despite the teaching in
the prior art, the apparatus of the present invention is not
limited by the size of the pulp exposure.
[0030] The mildest form of pulpal involvement are those teeth with
pulps which are exposed and which do not include any significant
pre-treatment pulpal pathology. The pulps of these teeth are
typically exposed (1) inadvertently while restoring the tooth for
objectives unrelated to the pulp; (2) intentionally exposed to
allow alignment of the tooth with other teeth during crown and
fixed bridge procedures; and (3) intentionally exposed when the
teeth are trimmed to the level of the gum and used for support of
an overdenture. Teeth which have been inadvertently exposed have
been treated frequently and successfully using calcium hydroxide
and more recently resin "capping materials" when the pulp exposure
was small. With moderate or large exposures, pulp capping was not
applied routinely or effectively.
[0031] Pulps exposed during tooth reduction for crowns (caps) or
fixed bridges were pulp capped less frequently and were usually
directed to endodontic procedures. This was because pulp capping
has not been considered a predictably successful procedure even
with asymptomatic pulps and small exposures. In contrast,
endodontic therapy is viewed as a predictable mode of treatment
(90+ percent success). Rather than risk having to perforate the
permanent crown for access in accomplishing endodontic therapy
after the crown has been cemented, teeth were often referred for
endodontic therapy upon exposure of the pulp and prior to
fabricating the permanent crown. Another disadvantage with crown
procedures is that tooth reduction at the pulp exposure site did
not provide space for capping materials and such materials often
dislodged. The present invention overcomes this problem by
specifically designing the exposure site for the pulp barrier
material, i.e., the pulpal wall is prepared with retention form,
resistance form, and space for the resinous barrier material in the
actual restoration of the wall.
[0032] The present invention also provides for teeth
(intentionally) exposed for use under overdentures. Teeth are
trimmed to the level of the gum typically exposing the pulp. Such
teeth have routinely been treated with endodontic therapy. No
successful efforts at maintaining the integrity of the pulpal
tissue in the root portion can be found in the literature. The
present invention preserves the integrity of the remaining pulp
tissue by a specific preparation of the exposure site and
restoration of the opening with a resinous barrier. The present
invention accordingly allows teeth to be saved and improves the
stability and function of traditional complete dentures.
[0033] Teeth exhibiting pulpal inflammation (pulpitis) and without
accompanying periapical lesions are considered to include greater
pathology than the intentional or mechanically exposed pulps since
these pulps have been exposed to bacteria contained in the carious
lesion or directly to the oral cavity. These teeth are routinely
diagnosed as "irreversible pulpitis" and relegated to endodontic
therapy or extraction. When acute pain is associated with other
clinical tests, the decision to treat endodontically is more
universal by current criteria. The present invention treats the
dental pulp as opposed to removing the pulp or tooth in all degrees
of pulpitis. These diseased teeth may range from nuisance level of
discomfort to the acutely painful tooth typically referred to as a
toothache or abscessed tooth.
[0034] Teeth exhibiting a periapical lesion (apical periodontitis)
are considered the most severe form of pulpal inflammation just
short of necrosis. (A periapical lesion is inflammation extending
beyond the pulp to the tissue and bone around the apex of the root,
hence the term "periapical". Such lesions are characterized by a
breakdown of the bone resulting in a radiolucency on X-rays.) Many
dentists assume that the pulp is necrotic when such a lesion is
seen on a dental radiograph. The presence of a periapical lesion is
almost universally accepted as an irreversible pulpitis or necrosis
of the pulp. Indeed, while terms such as "degenerating" or
"degenerated" periapical lesion delineating the various states of
pulpal pathology are described in dental texts, no comparable terms
such as "regenerating" periapical lesions are included in the
classification systems. This clearly signifies that the potential
for pulpal healing or treatment is not currently acknowledged by
the dental profession.
[0035] While a necrotic pulp may be irreversible, pulpal and
periapical inflammation may be successfully treated using the
apparatus and methods of the present invention. In particular, the
methods and apparatus of the present invention facilitate reversal
of periapical lesions.
B. Hemostasis
[0036] Before describing specific features and applications of
bipolar electrocoagulation in pulp therapy and restorative
dentistry, the importance of the present invention to hemostasis
should be understood.
[0037] Hemostasis is described in the medical literature to occur
in one of two ways: (1) Coaptive--whereby the vessel is grasped and
clipped, ligated, coagulated (electrosurgically welded), or
otherwise closed by bringing the walls of the vessels together.
This form is typically used with larger vessels and may also
involve coagulation of the vessel contents and shrinkage of the
vessel walls; (2) Obliterative--whereby the vessels and contents
are chemically treated or coagulated (by electrosurery or laser) so
that the resulting shrinkage of the vessel walls and blockage of
the vessel lumen by the coagulated vessel contents enables control
of bleeding. This form is typically used with small blood vessels
where grasping of the vessel would be difficult or impossible. Only
the obliterative form of hemostasis is applicable to pulp therapy.
Vessels are typically very small and access to vessels is
impossible as they are encased in a small chamber with hard tissue
walls (dentin).
[0038] While lasers can create precise coagulation of the surface
tissue, precision is essentially compromised by the presence of
blood on the surface of the pulp or other tissue. With a laser, and
previous monopolar or bipolar electrocoagulation methods, blood is
coagulated as well as the tissue. The impact of the electrical
current or laser beam is affected by the coagulating blood, thus,
compromising the precision of coagulation even though some
coagulation will occur. The present invention supersedes laser
applications in pulp therapy. For example, a coaxial electrode can
be positioned in direct contact with the exposed pulp tissue
despite a pool of blood and the surface of the tissue can be
precisely coagulated.
[0039] The precise coagulation of the present invention allows the
creation of a layer of desiccation. The term "desiccation" refers
to a specific level of coagulation between white coagulation, which
is coagulation at a lower temperature and black coagulation, which
is coagulation at a higher temperature often resulting in charring
of the tissue. Desiccation has been described in the medical
literature as the optimum level of coagulation for hemostasis.
C. Bipolar Electrocoagulation
[0040] There are two types of electrosurgery, monopolar and bipolar
electrosurgery. Electrosurgery has been in use in medicine and
dentistry for almost a century. In dentistry, it has been limited
exclusively to the monopolar variety except for limited use of
bipolar electrosurgery by oral surgeons. Both monopolar and bipolar
modes use an alternating electric current with a sinusoidal
waveform in the frequency range 500 KHZ to 4.0 MHZ. The monopolar
mode was the first to be developed (over a century ago) while the
bipolar mode was introduced by L. M. Hurd (Bipolar Electrode for
Electrocoagulation of the Interior Turbinate, Arch. of Otolaryngol,
1931; 13:442) and later introduced to neurosurgery in the 1940's
(Greenwood, J., Arch. Phys. Ther., 23:552-554 (1942)). Both modes
can generate coagulation of tissue while the monopolar mode is
superior in cutting capability. The high frequency current
possesses both traditional electric current properties and
radiating properties. The significant difference between the two
modes is the path of the dissipating current.
[0041] In the bipolar mode, the dissipating current flows directly
to the dispersive electrode which is typically the same size and
very close to the active electrode (Greenwood, supra refers to it
as "two point coagulation"). The only tissue involved in the
dissipating current is the tissue between the two electrodes. Thus,
bipolar electrosurgery provides substantially greater safety by
avoiding involvement of major vessels, nerves or other critical
tissues or organs. The bipolar mode requires approximately 20% of
the current to create the same degree of coagulation--an additional
safety feature by reducing the potential for capacitive
coupling.
[0042] The present invention applies a combination of either a
dual-prong or preferably a coaxial electrode with a bipolar
microsurgical unit to generate precise coagulation on the dental
pulp without deep injury to the pulp. The present invention
represents the first application of bipolar electrosurgery of any
form for hemostasis in pulp therapy. The combination of bipolar
electrodes, bipolar microsurgical unit, and electronic timer
generates an even higher level of precision and safety when
coagulating the surface of the dental pulp.
D. Electrodes
[0043] Bipolar electrodes can be categorized in one of three
groups: (1) Bipolar forceps with each forceps tip individually
wired are used to grasp tissue or vessels for coagulation; (2)
Two-prong electrodes with a fixed distance between the electrodes
which allows coagulation of the tissue between the two points. Two
point electrodes have been adapted in the present invention to
enable coagulation of pulpal and gingival tissue; and (3) Coaxial
electrodes utilized in ophthalmic surgery which consist of an outer
tube and an inner insulated wire forming respective outer and inner
electrode poles. Coagulation occurs in a circular "footprint"
approximately the size of the end of the coaxial electrode. The
present invention has adapted and refined the use of the coaxial
electrode for use in pulp therapy.
[0044] For purposes of bipolar coagulation, blood is a conductive
tissue and substantially influences the degree of coagulation, zone
of coagulation, optimal power output and the path of the current.
Indeed, blood behaves much like tissue and in some aspects is more
susceptible to coagulation. For example, relatively dry tissue is
less susceptible to coagulation than moist tissue. This is probably
due to the conductivity at the interface of electrode and tissue.
Blood enhances the conductivity at the interface. Unfortunately, it
also allows dissipation of the electrosurgical current creating a
wider and unpredictable zone of coagulation. These variations apply
to monopolar electrosurgery and to most forms of bipolar
electrosurgery. An important exception is the bipolar coaxial
electrode. Blood in the field influences the behavior of the
coaxial electrode minimally provided the electrode is placed in
contact with the surface of the tissue and not just in contact with
blood. Typical bipolar electrodes, on the other hand, will
coagulate both the blood and tissue affecting the power delivered
to the tissue. The exposed prongs of the other electrodes allow
dissipation of current around the electrode creating a more diffuse
coagulation. The highly desirable precision in coagulation is
lost.
[0045] The selection of a coaxial bipolar electrode [as opposed to
a parallel fixed-position dual-prong electrode (FPDP) or a
variable-position dual-prong electrode (VPDP, forceps-type)] is a
crucial factor in establishing a high level of consistency in
treatment of dental pulps. In pulp therapy, a very shallow zone of
coagulation is critical to the success of pulp therapy. The coaxial
electrode is self-limiting in area and depth of coagulation and the
area of coagulation is more consistent (a circular zone of
coagulation determined by the "footprint" of the electrode) than
other types of electrodes. Furthermore, the total zone of
coagulation is much more consistent than with other types of
electrodes. The current at the inner electrode pole is limited in
flow to the encircling outer electrode pole confining the
coagulation to the diameter of the outer tube. As the current
coagulates the tissue between the inner and outer electrode poles,
the resulting increased resistance (impedance) of the tissue
prevents further or deeper coagulation.
[0046] Coagulation in the bipolar mode always requires contact of
the electrode with the tissue. However, with the FPDP and VPDP
electrodes if the electrode penetrates the tissue surface,
additional coagulation will occur throughout the length of the
immersed segments of the electrode. Indeed, the depth of
penetration will proportionately determine the depth of
coagulation. This is undesirable in pulp therapy. The coaxial
electrode behaves differently. Since the inner electrode pole is
encased within the outer electrode pole, and since there is no
tissue between the inner and outer electrode poles except where the
inner electrode pole exits the outer electrode pole, coagulation is
limited to the end-surface of the electrode. Furthermore, as soon
as the tissue at the tip of the electrode becomes coagulated, the
impedance increases preventing further flow of current (within
reasonable power levels). Therefore, the zone of coagulation varies
little whether the coaxial electrode touches only the surface or
penetrates the surface. Under both conditions, the resulting
coagulation takes the form of a thin disc with the diameter of the
electrode. Coagulation along the shaft of the coaxial electrode
does not occur.
E. Detailed Description of the Apparatus
[0047] FIG. 1 shows the electrosurgical tool 20 according to the
invention. Tool 20 has an elongated hand piece 22 with a butt end
24 and a head 26 positioned opposite the butt end. An elongated
electrode 28, described in detail below, is mounted on and extends
outwardly from the head. An electrical coupling, preferably in the
form of standard male prongs 30 for electrically coupling to a
power cord of an electrosurgical unit (not shown, described below)
is mounted on the butt end.
[0048] Hand piece 22 is formed of a neck portion 32 adjacent to the
head 26 and a grip portion 34 positioned between the neck portion
32 and the butt end 24. Neck portion 32 is preferably oriented at
an angle 36 relatively to the grip portion 34. Angle 36 is
preferably between about 20.degree. and 30.degree. and most
preferably at about 25.degree. to accommodate the curves of the
dental arches and allow improved access of the electrode 28 to
various tooth surfaces within the oral cavity. The angular
orientation of neck portion 32 also enables a relatively wide range
of angular movement of the hand piece within the oral cavity about
the head 26 within a plane 38 defined by the neck portion 32 and
the electrode 28.
[0049] Hand piece 22 is preferably made from durable, lightweight,
inexpensive material, for example, plastic such as
polytetrafluoroethylene. Hand pieces made of these materials are
less likely to damage tooth surfaces should they come in contact
with them, will withstand repeated sterilization providing a
relatively long useful life and yet be easily and economically
replaceable when they wear out. Use of lightweight material allows
the tool to be maneuvered easily within the confines of the oral
cavity and reduces user fatigue, allowing for precise, steady
positioning of the electrode at a desired position. As a practical
matter for ease of handling and use, the grip portion 34 is
preferably about 10 cm in length and 6 to 10 mm in diameter. The
neck portion is preferably between about 2 and 3.5 cm in length and
about 5-6 mm in diameter.
[0050] FIG. 2 shows a detailed cross-sectional view of head 26 and
electrode 28. Preferably, electrode 28 is a coaxial bipolar
electrode having an inner electrode pole 40 positioned within an
insulative sleeve 42 and an outer electrode pole 44 in the form of
a tube surrounding the sleeve 42 coaxial with the inner pole 40.
Electrode 28 fits within a socket 46 within the head 26 and is
preferably oriented at an angle 48 with respect to the hand piece.
Angle 48 is preferably about 90.degree. relative to the neck
portion 32, but may be between 0.degree. (parallel to the neck
portion) to about 135.degree. for practical applications.
[0051] Socket 46 is preferably formed within a body 50 of flexible,
resilient, insulating material such as plastic and has a diameter
52 sized slightly smaller than the outer diameter 54 of the
electrode to receive the electrode in an interference fit. The
interference fit develops friction between the body 50 and the
electrode 28, thereby retaining the electrode within the socket but
allowing it to be easily removed to interchange or replace
electrodes. The interference fit also allows the electrode to be
rotated about its long axis 56 relatively to hand piece 22.
Allowing the electrode 28 to rotate about its long axis 56 provides
a significant advantage for electrodes having an end face 58 which
is asymmetrically positioned relatively to the long axis (either
because the electrode is curved as shown in FIG. 1, or the end face
is cut back as described below). The advantage is illustrated in
FIG. 3 wherein the same tool 20, shown in solid and dashed line,
may be used to coagulate exposed pulp 59 on opposite tooth surfaces
60 and 62 because the end face 58 is asymmetrically positioned with
respect to the long axis 56 (in this example, by curving the
electrode). The operator need only withdraw the tool from the oral
cavity, manually rotate the electrode 28 about axis 56 to the
desired orientation and then reposition the tool within the oral
cavity against the desired tooth surface. If electrode 28 were not
rotatable then the operator would have to change tools, a
considerable inconvenience, to treat an opposite tooth surface. The
interference fit is designed to permit the electrode to be rotated
by gripping it between the forefinger and thumb and yet have
sufficient friction so that the electrode will reliably retain the
position as set and not rotate upon mere light contact between the
end face 58 and a tooth surface or other part of the oral
cavity.
[0052] FIG. 2 also shows an electrically conductive pathway in the
form of wires 64 which are arranged lengthwise along hand piece 22
and connect the prongs 30 to the electrode poles 40 and 44 for
powering the electrode 28 by the ESU when the prongs are connected
to the ESU power cord. Wires 64 connect to their respective
electrode poles by means of contacts 66 and 68 embedded within body
50.
[0053] Preferably, the contacts 66 and 68, as well as the socket
46, are sized to accept a standard electrode end 70 which is the
same size regardless of the size of the electrode. FIG. 12 shows an
example of a larger size electrode 72 having a standard electrode
end 70 for use with the hand piece 22 according to the invention.
Standard electrode end 70 has an inner electrode pole terminal 74
which is coaxial with an insulating layer 76 and an outer electrode
pole terminal 78. Preferably, inner electrode pole terminal 74
extends lengthwise beyond the outer electrode pole terminal and has
a diameter sized to engage contact 66 within body 50 (see FIG. 2).
The outer electrode pole terminal 78 has an outer diameter sized to
engage contact 68 as well as to interfit within socket 46 (see
FIGS. 2 and 4) and provide the interference fit between the
electrode 28 and the body 50, creating the necessary friction to
retain the electrode within the socket and prevent any undesired
rotation. By standardizing the sockets, contacts and electrode ends
and making the electrodes easily interchangeable, the versatility
of the tool is increased and the duplication of tools merely to use
electrodes having different sizes or shapes is eliminated.
[0054] Versatility and ease of use of the tool are further
increased by the features shown in FIGS. 4 and 5. FIG. 4 shows a
head 26 having two sockets 46a and 46b. Socket 46b is oriented at
an angle 80 with respect to socket 46a and electrode 28 may be
inserted into either one of the sockets as needed to most
conveniently treat a particular tooth surface. As described above,
the electrode is held within the socket by friction and is
rotatable about its long axis 56. Preferably, an insulating plug
(not shown) is inserted into the socket not having an electrode to
prevent debris from accumulating within it.
[0055] FIG. 5 shows a head 26 which is pivotally mounted on neck
portion 32 between two flanking portions 81 which extend from neck
portion 32 on either side of head 26. Head 26 pivots about an axis
82 which is substantially perpendicular to both hand piece 22 and
electrode 28. The relative pivot angle 83 of the head 26 may be
adjusted manually. As shown in FIGS. 5A and 5B, head 26 is
rotatably mounted on inwardly projecting trunnions 84 extending
from flanking portions 81 and has outwardly facing side surfaces 85
which engage respective inwardly facing surfaces 86 on flanking
portions 81. Surfaces 85 and 86 preferably have interlocking teeth
87 to hold the head 26 securely in a desired angular position by
bearing contact between them. Alternately, the surfaces 85 and 86
may be textured, knurled, have detents or other means for locking
the head in a desired angular position. Preferably, flanking
portions 81 are formed of a flexible, resilient material and are
biased toward each other so as to force the surfaces 85 and 86
normally into engagement, thereby locking the head 26 in position.
However, upon manual rotation of the head 26 about axis 82, teeth
87 ride over each other, forcing the flanking portions 81 to move
outwardly and allow the head 26 to rotate. The flanking portions
are flexible and resilient and move back into their biased position
to lock the head 26 in place once the desired position is reached
and the teeth are again in interlocking, bearing contact.
[0056] As best illustrated in FIG. 5B, the trunnions 84 are
received within electrically conducting cups 88 arranged within
head 26 coaxially with axis 82. The cups 88 serve as bearings for
the rotation of head 26 and are electrically connected to
respective contacts 66 and 68 by wires 89. Trunnions 84 are also
electrically conductive and connected to wires 64. Together, the
cups 88 and trunnions 84 provide for an electrical connection
between the ESU and the electrode 28 across relatively rotating
members 32 and 26.
[0057] Various different electrodes, illustrated in FIGS. 2 and
6-12, may be used effectively with the tool 20 according to the
invention. Common to all of the electrodes is the standard end 70
engageable with the standard socket 46 regardless of electrode size
or shape. Practical sizes for electrodes vary, with the preferred
range being between 18 gauge and 23 gauge for treating dental
pulp.
[0058] The straight electrode illustrated in FIG. 2 preferably has
a dome-shaped end face 58, created by extending the inner pole 40
lengthwise beyond the insulating sleeve 42 and the outer pole 44.
The preferred lengthwise distance 90 between the inner pole 40 and
the outer pole 44 is about 0.05-0.5 mm and determines the depth of
penetration of coagulation into the tissue being treated. The
greater the distance 90 the deeper the coagulation penetration.
This relation between coagulation depth and lengthwise distance 90
is due to the nature of the bipolar coaxial electrode, which causes
coagulation only in the zone where current flows between the inner
and outer electrode poles 40 and 44. For the dome-shaped end, the
current flows in an imaginary conical segment between the poles and
the greater the distance between the poles, the greater the height
of the conical segment, and hence, the greater the depth of
penetration for coagulation. As explained previously, the advantage
of the tool according to the invention lies in the relatively
shallow coagulation depth, which is achieved by limiting the
lengthwise distance 90 between the electrode poles to within the
preferred range defined above.
[0059] As shown in FIGS. 6 and 7, the electrode 28 may also be
curved. Curved electrodes orient the end face 58 asymmetrically
with respect to the electrode's long axis 56, and when the
electrode is rotatable within socket 46, afford the significant
advantage illustrated in FIG. 3 where the same tool may be used to
treat opposite surfaces of the teeth. Alternatively to being
dome-shaped, the end face may be a cut-back type, as illustrated in
FIGS. 8-11.
[0060] FIGS. 8 and 9 show an electrode 28 having a cut-back end
face 58, wherein the outer electrode pole 44 and the insulating
sleeve 42 are cut away asymmetrically on one side of the electrode
along a region 92 at the electrode tip 94 to expose the inner
electrode pole 40. Preferably, about 40% of the electrode is
removed over a length of about 1.0-3.0 mm. Current may flow from
the inner electrode pole 40 to the outer pole 44 along the entire
length of region 92 and the cut-back results in a larger, elongated
zone of coagulation when such a tip is used to treat tooth pulp,
gingiva or other soft tissue in the oral cavity. The cut-back
electrode may be straight or curved as illustrated in FIGS. 8 and
9. When the electrode is curved, the cut-back region 92 may be
positioned on the convex side of the electrode (the side opposite
to the center of curvature 96), as shown in FIG. 8, or the cut-back
region 92 may alternatively be positioned on the concave side of
the electrode as shown in FIG. 10. Regardless of whether the
electrode is curved and has a dome-shaped end face 58 or is
cut-back, it is the asymmetric orientation of the end face
relatively to the electrode's long axis, combined with the ability
to rotate the electrode about this axis which significantly
improves the versatility of the tool.
[0061] When coagulation occurs, the coagulated tissue has a
tendency to stick to the end face of the electrode. If not removed,
the coagulant layer reduces the effectiveness of the electrode. The
choice of alloy and polishing procedures used on the electrode end
face can influence the degree of "sticking" of the coagulated
tissue. The optimal alloy used in the electrode would be determined
based primarily on a determination of which alloy provided the
greatest conductivity while resulting in minimal sticking of
coagulated tissue. Accordingly, the electrodes used in the present
invention are made of any suitable conducting material, preferably
from a non-sticking nickel and/or stainless steel alloy.
F. Electrosurgical Unit
[0062] The electrodes are preferably used with a bipolar
electrosurgical unit (ESU), which includes a timer to control the
impulses in fractions of a second. The timer can be regulated by
the operator and is pre-set for the specific electrode, ESU and
power level to be used. Some units include timers for specific
therapeutic objectives (e.g., coagulation for reduction of the size
of the uvula (8 sec range)).
[0063] Many bipolar electrosurgical units are available with a
variety of current frequencies and current types (e.g., various
waveform types, damping, work cycle).
[0064] The general requirements for a bipolar ESU are as
follows:
[0065] Power Output: 0-20 watts as measured against 100 Ohm
resistance
[0066] Power Supply: 115 V, 60 Hz (optional 220 V, 50 Hz)
[0067] Frequency: Optimum 500 KHZ (other frequencies will also
work)
[0068] Current: Optimum--smooth, non-modulated, continuous
RF-current (other currents will also work with appropriate
calibration with electrodes.)
[0069] Cable: Teflon coated twin-wire 6-10 foot cable
[0070] The ESU preferably has power output in the range of about
0.0 to about 20.0 watts. A number of criteria define what
frequencies should be used with the unit. Firstly, a frequency must
be sufficiently high to prevent stimulation of muscles and nerves.
Available electrosurgical frequencies are well above these levels.
Secondly, heat is generated by the rapid oscillation of charged
molecules caused by the alternating polarity of the alternating
electrosurgical current. This is referred to as the dielectric
effect and increases with an increase in the frequency of the
alternative current. What portion of the heat generated is due to
the dielectric effect and what portion is due to resistance
(impedance) of the tissue is unclear. Frequencies in the range of
0.5 to 4.0 MHZ are typically used in electrosurgery with the most
often used frequencies occurring in the 0.5 to 2.0 MHZ. Thirdly,
the higher frequencies (3.0 to 4.0 MHZ) result in more current loss
due to the radiating properties of electrosurgical currents. This
factor encourages the use of lower frequencies.
[0071] Low power microsurgical units range from 0-15 watts, while
high power units used for prostate resection can provide 300 or
more watts. Based on the type of tissue, the volume of tissue and
the precise nature of coagulation desired in pulpal hemostasis, an
electrosurgical unit providing power output in the range of 0-20
watts (measured against 100 Ohm resistance) is preferred.
[0072] The ESU of the present invention preferably includes an
electronic timer which can be set for the appropriate time
intervals for each electrode (0.05 to 0.5 sec) to create the
optimal level of coagulation. The optimal level of coagulation is
determined by establishing durable hemostasis with minimal surgical
wound. Durable hemostasis can be ascertained clinically using (1)
vital pulps; (2) an intact circulation; (3) actual pulp tissue; and
(4) conditions and circumstances that will be confronted in actual
pulp therapy. Minimal surgical wound can be observed and
established with each electrode design by utilizing the electrode
on tissue specimens such as beef steak, beef liver, animal
intestinal walls or animal blood vessels. An example of how to
determine the optimal level of coagulation is presented in Example
2 hereinbelow.
[0073] The implementation of the timer enables another level of
safety and precision when attempting to coagulate extremely small
areas and for extremely shallow depths. The combination of a ESU, a
coaxial electrode, and a timer allowing intervals in fractions of a
second enables the ultimate precision in coagulation. Once the
tissue at the end of the electrode coagulates, the increased
resistance (impedance) of the tissue prevents flow of current. This
self-limiting capability of the coaxial electrode replaces more
complex systems, e.g., impedance monitoring of the active electrode
or temperature monitoring of the tissue at the active
electrode.
[0074] The apparatus of the present invention establish an
electrosurgical application with unprecedented precision. The
apparatus of the present invention has as its goal a specific
therapeutic objective--to create the desiccated form of coagulation
on a small area of one type tissue (dental pulp). This is possible
in part because the tissue to be coagulated is fair uniform in
composition compared to the tissue encountered in most other
surgical procedures.
[0075] In order to establish the optimum power/time settings
("hemostatic combination"), the type of electrode, the size of each
pole of the electrode, the type of metal composing the electrode
and numerous other aspects must be considered to optimize
treatment.
[0076] The optimal configuration for the electrode is established
by the location and size of the most typical exposures expected to
be confronted. Since most exposures occur because of decay on the
mesial and distal sides of teeth (between teeth), the typical
electrode would have a right-angle bend with a 10 mm extension
beyond the bend. Preferably, an about 18 gauge electrode is used to
treat lesions due to decay while an about 23 gauge electrode is
preferably used for coagulation within the root portions in
overdenture applications.
[0077] The optimal power/time combination will provide uniform
coagulation throughout the footprint of the electrode. An example
of how to determine the optimal power/time combination is presented
in Example 3.
[0078] The coaxial design provides the most consistent, shallow and
optimal form of coagulation with the greatest safety and minimal
surgical wound. By relying on bipolar coagulation and a specific
coaxial electrode, the volume of tissue to be coagulated is
consistent, and by relying on the bipolar mode and using a coaxial
electrode configuration, the path of the current is consistent. The
frequency and current type of the ESU is established by the
manufacturer which are initially factored in the calibration of the
"hemostatic combination" and, therefore, consistent. The use of a
pre-determined optimal time which has been found to be in fractions
of a second (e.g., 0.5 sec impulse) provides another level of
consistency. Given the difficulty in manually controlling the
output of the ESU in fractions of a second, the timer is an
important component in providing consistency and a greater level of
safety to the pulp.
G. Pulp Barrier
[0079] The methods related to the present invention include use of
components for replacing the lost pulpal wall. These components are
included to provide retention for the pulp barrier independent of
the external restoration. The long term integrity of the pulp
barrier: (1) should not be linked to the stresses applied to the
external restoration; (2) should not be determined by the
success/failure of the external restoration; and (3) the pulp
barrier should not provide the principal support or retention for
the external restoration. The external restoration should rely on
traditional cavity preparation components for retention and
resistance to prevent displacement outward. This protocol, however,
emphasizes the incorporation of retentive components to also
prevent inward displacement of the external restoration. Contrary
to recommendations by many lecturers and manufacturers of adhesive
restorative materials, the adhesion that occurs between a resinous
pulp barrier and an adhering external restoration should be
directed to preventing microleakage and not relied upon for the
basic retention of the restoration. If and when an external
restoration fails or needs replacement, ideally the pulp barrier
should remain intact. Traditional cavity preparation components for
retention include undercuts, grooves or threaded pins.
[0080] The material used for replacing the lost portion of the
pulpal wall preferably comprises an adhesive resin barrier material
which creates an effective hybrid layer and is biocompatible with
the pulp. A variety of resinous materials may also prove useful as
a long-term pulp barrier.
[0081] A wide range of resins have been introduced in dentistry to
achieve adhesion between the dentin and the external restoration
with the objective of reducing microleakage and the ingress of
bacteria from the oral cavity to the internal walls of the cavity
preparation. With a substantial dentinal wall remaining over the
pulp, the biocompatibility of the resins with the pulp is not an
important concern. However, when such resins are applied in direct
contact with pulpal tissue, the biocompatibility issue is
crucial.
[0082] The methods associated with the present invention go beyond
current procedures to utilize resins as the restorative material to
reconstruct the missing pulpal wall. Hence, the resin is referred
to as a "pulp barrier" rather than a "pulp capping" material.
Traditional pulp capping materials served to provide medicaments to
the pulp, to provide thermal protection (insulation) and to
stimulate reparative dentin via a mild irritating effect on the
pulp.
[0083] A preferred resin material is a 4-META adhesive resin system
(Metabond C&B; Parkell Dental Products, Farmingdale, N.Y.)
which can be used to replace the missing segment of the pulpal wall
and which has demonstrated the ability to create an effective seal
(hybrid layer). The 4-META resin may be applied according to the
instructions of the manufacturer. Studies support a degree of
biocompatibility with pulpal tissue.
[0084] Preferably, the resin used to restore the pulpal wall
includes a visible dye such that the resin is color coded, serving
to warn dentists performing subsequent procedures not to violate
the pulpal wall barrier. A variety of dyes are known in the dental
arts, and any dye that is non-toxic and which retains its color are
preferably used in the practice of the invention.
EXAMPLES
Example 1
Pulp Hemostasis Method
[0085] The following example describes the use of the methods and
apparatus of the present invention for pulp hemostasis.
[0086] The tooth is examined clinically and radiographically.
Clinical symptoms are recorded for comparison with subsequent
evaluations. Evidence of periapical inflammation is also noted
(tenderness to percussion of the tooth and apical radiolucency).
Vitality of the tooth is determined by sensitivity to ice, electric
pulp testing or sensitivity to instrumentation such as cavity
preparation prior to local anesthetic. If the pulp is diagnosed as
necrotic, the tooth is planned for extraction or endodontic therapy
since pulp therapy is not possible.
[0087] Once vitality is established the tooth is anesthetized with
local anesthetic. If the carious lesion does not extend
subgingivally, a rubber dam may be placed for improved
isolation.
[0088] The outline form for the planned cavity preparation is
completed according to traditional guidelines avoiding temporarily
the removal of deep caries. Deep caries excavation with the
probable exposure of the pulp is postponed until the majority of
the cavity preparation is completed to minimize debris from
entering the pulpal space.
[0089] Once the cavity preparation is completed, deep caries is
removed with a large sharp spoon excavator or a round bur on a low
speed handpiece.
[0090] Caries excavation is completed despite initial exposure of
the pulp. Thorough excavation of caries should be accomplished.
Unlike past "pulp capping" procedures in which the prognosis was
considered better if the exposure was kept small, in vital pulp
therapy described in this protocol the prognosis is improved by
removal of all affected and compromised dentin. [Affected and
compromised refers to the (1) decalcification of the remaining
dentin, (2) inclusion of bacteria or bacterial by-products, and (3)
potential collapse of thin areas of dentin.] Vital pulp therapy
encourages more thorough removal of caries and affected dentin.
[0091] Bleeding of the pulp during caries excavation and cavity
preparation should be encouraged since the flushing action of the
bleeding will reduce the debris that may become incorporated in the
pulp.
[0092] Once the cavity preparation is completed, vitality of the
pulp is confirmed by the presence of both blood (intact
circulation) and pulp tissue. Blood alone can sometimes occur from
the apical region or from another canal despite a necrotic pulp in
one or more canals. Instrumentation and materials are then prepared
for hemostasis and formation of the pulp barrier (restoration of
the pulpal wall).
[0093] A Kirwan 18 g coaxial bipolar electrode used in
ophthalmology is used to provide hemostasis in pulp therapy
utilizing an Elmed Micro Electrosurgery Unit with power output
(against 100 Ohm resistance) of about 0 to about 20 watts and a
frequency of 500 MHZ. the unit is combined with an electronic timer
providing 0.5 sec interval of power with each press of the foot
switch. The power setting of the unit is set to #6 providing 5
watts of power at the unit (determining the actual power at the
tissue surface is difficult and may vary for many reasons; e.g.,
length of cable, deterioration of cable, radiating potential of
high frequency causing current loss, etc.). The electrode is
attached to the unit via a 6 foot Teflon covered cable.
[0094] The coaxial electrode is placed in contact with the pulp
tissue and the foot control is engaged to provide one impulse of
0.5 sec duration. If the exposure is larger than the end of the
electrode and bleeding is occurring from other points, the
electrode is moved and another 0.5 sec impulse is applied. This
sequence is continued until the entire surface of the pulp is
coagulated. The size of the exposure is inconsequential. If one of
the impulses did not achieve hemostasis, another impulse can be
applied over the same area. By using the coaxial electrode, the
depth of coagulation is not cumulative but more "compensatory",
i.e., tissue already coagulated develops a higher resistance
(impedance) and inhibits further coagulation while adjacent
unaffected tissue will be susceptible to coagulation. The coaxial
electrode has the capability to control the flow of current to the
area immediately under the electrode tip. Indeed the same area can
receive numerous coaxial impulses with virtually no increase in
depth of coagulation. Rarely will it be necessary to increase the
power, and when that option is selected, it is increased only one
setting (approximately 1-2 watts).
[0095] Once hemostasis is achieved, it is checked for durability by
swabbing the pulpal surface with a cotton pellet moistened with
water or saline. If bleeding recurs, coagulation is repeated.
Specific bleeding points will be more visible and readily
coagulated since most vessels have been sealed previously. The
durability check is important since it is crucial that bleeding
does not recur while the barrier is being formed.
[0096] Once durable hemostasis is accomplished, an adhesive resin
barrier material which creates an effective hybrid layer and is
biocompatible with the pulp is applied according to the
instructions of the manufacturer. (4-META adhesive resin system
(Metabond C&B; Parkell Dental Products, Farmingdale, N.Y.). The
material is applied in increments with a brush tip to minimize the
polymerization shrinkage. Additional retentive components may be
incorporated after complete setting of the barrier material. The
remaining dentin and enamel are prepared for a sealed external
restoration.
[0097] The external restoration is then placed according to
traditional procedures.
[0098] The patient is recalled 3, 6 and 12 months for recall
evaluation using the same criteria as the pre-treatment
examination.
Example 2
Determination of Optimal Coagulation
[0099] A new coaxial electrode with a given outer diameter will be
coupled with a Elmed Microsurgical Unit and a six-foot cable. The
optimal and consistent coagulation ("hemostatic combination") for
that electrode will be defined by (1) uniform coagulation
throughout the electrode "footprint" (surface area of the end of
the electrode tip), and (2) minimal depth of coagulation (0.25 to
0.5 mm depth). By varying the power output to the electrode one
will observe, with insufficient current, that a "donut"
configuration of coagulation occurs with an inner zone of
uncoagulated tissue and an outer rim of coagulation following the
outline of the outer tube of the electrode. As the power output is
increased, the zone of coagulation becomes uniform throughout the
entire surface (footprint) of the electrode tip. Further increasing
the power output is redundant with the coaxial electrode. The
coaxial electrode is self-limiting in coagulation which is one of
the highly-valued properties and safety features for applications
in pulp therapy. Increasing the power output with other types of
electrodes increases the "area" of coagulation, the "depth" of
coagulation and the "degree" of coagulation proceeding from the
lower acceptable levels of white coagulation, through the optimal
level of desiccation, to the higher unacceptable levels of black
coagulation (charring).
[0100] Thus, by varying the power levels and impulse time
intervals, an optimal "combination" can be established for each
electrode design and size.
Example 3
Determination of Optimal Power and Time Settings for ESU
[0101] To establish the optimal power/time combination, the
electrode would be used on liver tissue beginning with a fixed time
interval selected within a reasonable range of 0.01 to 1.0 seconds.
While intervals in the range of several seconds at very low power
would also create coagulation, substantial lateral heat and a
broader area of coagulation would occur which is not desirable.
Beginning with the lowest power setting on the electrosurgical
unit, areas would be coagulated on the liver until the optimal
coagulation zone is achieved (uniform coagulation throughout the
"footprint" of the electrode). The power would be increased further
to ascertain that the lower power levels provided the optimal
coagulation.
[0102] One of the lowest power output levels that achieved optimal
coagulation would then be selected (several levels may be
available) as the fixed power output level. The same process would
be repeated by varying the time interval to establish the minimum
time intervals that provide the optimal zone of coagulation. Once
both series are plotted, the minimal time is coupled with the
minimal power to establish the optimal combination for that
electrode design. Although several combinations may be found
suitable, they will all fall within a narrow range. An optimal
time/power "hemostatic combination" can readily be established in
the mid-range providing some latitude for the operator. Such a
graph is provided in FIG. 13 to illustrate how definitively the
optimum combination can be established.
* * * * *