Note: Descriptions are shown in the official language in which they were submitted.
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THERMOPLASTIC DENTURE FRAMES, METHODS FOR MAKING
THERMOPLASTIC DENTURE FRAMES AND DENTURES CONTAINING
THERMOPLASTIC DENTURE FRAMES
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No.
62/299,657,
filed February 25, 2016; U.S. Provisional Patent Application No. 62/421,532,
filed November
14, 2016; and European Patent Application number EP 16171913.3, filed May 30,
2016, which
claims priority to U.S. Provisional Patent Application No. 62/299,657, filed
February 25, 2016.
each of which is incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
The present invention relates to denture frames include at least one
poly(ether ether)
ketone polymer and at least one polyphenylsulfone polymer. The invention
further relates to
methods of making a denture frame. Still further, the invention relates to
dentures incorporating
denture frames.
BACKGROUND OF THE INVENTION
Dentures are designed to replace missing teeth. Dentures generally consist of
a
removable plate (or frame) that holds one or more teeth. Traditionally,
dentures include a metal
frame, which is desirable due to the stress resistance, durability, and stain
resistance of the
material. However, the use of metal has numerous disadvantages such as
undesirable aesthetics,
stiffness, and weight, as well as design and manufacturing limitations that
can lead to poor fit
and patient discomfort or dissatisfaction. Attempts have been made to address
some of the
deficiencies of metal by making dental prostheses from a thermoplastic polymer
such as a
poly(ether ether ketone) polymer; however a need remains for dental prostheses
with improved
toughness, flexibility, color stability and dimensional stability, leading to
improved product
lifetimes.
BRIEF DESCRIPTION OF DRAWINGS
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Fig. 1 is a schematic depiction of a top-down view of a mandibular partial
removable
denture.
Fig. 2 is a schematic depiction of a top-down view of a mandibular partial
removable
denture frame.
Fig. 3 is a schematic depiction of a top-down view of the mandibular partial
removable
denture frame of Fig. 2 positioned in a patient's mouth.
Fig. 4 is a schematic depiction of a top-down view of a portion of a denture
frame
showing a finish line.
Fig. 5 is a schematic depiction of a perspective view of a region of a denture
frame
showing a finish line.
Fig. 6 is a schematic depiction of a cross section of a finish line.
Fig. 7A and 7B are a schematic depictions of a cross section of a portion of a
denture
displaying a finish line with a cupped inner surface and a portion of an
artificial gum, where Fig.
7A depicts the denture without flex and Fig. 7B depicts the denture under
flexing.
Fig. 8 is schematic depiction of a cross section of a portion of a denture
frame showing a
finish line having a symmetric cross section.
DETAILED DESCRIPTION OF THE INVENTION
Described herein are thermoplastic denture frames having significantly
improved
lifetimes as well as comfort. The general lifetime of a denture frame (and
denture) is a function
of both its aesthetic characteristics and its mechanical characteristics. The
denture frames
described herein include a polymer compositions including at least one
poly(ether ether ketone)
("PEEK") polymer and at least one polyphenylsulfone ("PPSU") polymer.
Aesthetically, it was
surprisingly discovered that the polymer compositions have significantly
improved color
stability, relative to corresponding polymer compositions the including the at
least one PEEK
polymer as the only polymeric component of the polymer composition.
Mechanically, the
polymer compositions additionally have significantly improved toughness,
flexibility and
dimensional stability. The combination of the aesthetic characteristics and
mechanical
characteristics of the polymer compositions allows for denture frames having
improved lifetimes
and comfort.
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The general lifetime of a denture frame is a function of both its aesthetic
characteristics
and its mechanical characteristics. With respect to aesthetics, given the
desire for concealed use,
the denture frames described herein have significantly improved aesthetic
characteristics relative
to denture frames including a corresponding polymer compositions including the
at least one
PEEK polymer as the only polymer. While dentures provide a biomechanical
benefit (e.g.
increased chewing ability), the aesthetic nature of the denture significantly
impacts its customer
appeal. For example, denture frames that take on a more natural appearance in
the the oral
environment into which they are inserted are highly preferable, as they help
to conceal the
presence of the denture frame itself. Denture design elements such as color
matching, frame
thickness and fitment, among other characteristics, help to conceal the
denture when placed in
the oral cavity. However, the oral cavity is a chemically harsh environment.
Some types of
common foods and drinks (e.g. coffee and wine) can be harsh staining agents,
which come into
contact with the denture (and, of course, the denture frame) during their
intended and normal
course of use. Despite cleaning, dentures eventually stain to an extent that
they cannot be
sufficiently cleaned to maintain desirable color matching, which makes the
dentures more visibly
apparent (less concealed). As noted above, the polymer compositions described
herein have
surprisingly improved color stability (e.g. anti-staining ability), which can
prolong the usable
lifetime of the denture frame and reduce the rate at which the dentures are
replaced based on the
staining of the denture frame.
With respect to mechanical performance, the oral environment is, additionally,
a very
demanding application setting. The masticatory force generated during routine
mastication of
food can be from about 70 Newtons ("N") to 150 N, and up to 500 N to 700 N
depending on the
type of food and muscular size/density. The force is distributed along the
anterior, general
(covering the entire arch) and posterior parts of the arch formed by the
teeth. At the locations of
artificial teeth of the denture, the force is also at least partially
transferred to the denture frame.
Additionally, horizontal forces on the denture frame are generated during
mastication by occlusal
contact and by the oral musculature surrounding the denture during
mastication. Such forces can
displace the denture and denture frame in both antero-posterior and lateral
directions as well as
place tremendous impact forces on the denture frame. After repeated use, the
denture frame can
suffer mechanical failure. Relative to polymer compositions including only
PEEK polymers, the
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polymer compositions have improved toughness and flexibility, allowing for
denture frames
having increased lifetimes due to increased mechanical performance.
Still further, the denture frames described herein have improved comfort,
relative to
denture frames having a polymer compositions including PEEK polymers alone. In
conjunction
with the improved mechanical properties described above, the polymer
compositions described
herein allow for denture frames having thinner components while maintaining
desirable
mechanical properties. Not only are the resulting denture frames lighter, the
thinner components
allow for denture frames less noticeable to the wearer with respect to feel.
Moreover, as
discussed in detail below, it was surprisingly found that the denture frames
described herein,
when fabricated using selected milling methods, had significantly improved
dimensional
stability, relative to corresponding denture frames fabricated with injection
molding methods.
Accordingly, patient fitment issues are reduced.
The Polymer Composition
The denture frames include a polymer composition containing at least one PEEK
polymer
and at least one PPSU polymer. In some embodiments, the polymer composition
further
includes one or more additives. In some embodiments, each of the polymers in
the polymer
composition (or in the denture frame) is a PEEK polymer or a PPSU polymer.
As mentioned above, the polymer compositions have surprising color retention
properties. In particular, relative to corresponding polymer compositions free
of the PPSU
polymer, the polymer compositions described herein have improved color
retention. For clarity,
a corresponding polymer composition is one in which the PPSU polymer is
replaced with PEEK
polymer. For example, if a polymer composition includes at least one PEEK
polymer, at least
one PPSU polymer and additives, the corresponding polymer composition is the
one in which the
at least one PPSU polymer is replaced with the at least one PEEK polymer.
In some embodiments, the denture frames consists essentially of the polymer
composition, with respect to color stability or dimensional stability.
In some embodiments, the ratio of the concentrations of the at least one PEEK
polymer to
the at least on PPSU polymer can be 40/60 to 90/10, preferably 50/50 to 80/20,
preferably 55/45
to 75/25, preferably 58/42 to 70/30, most preferably 63/37.
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The Poly(Ether Ether Ketone) Polymer
The polymer composition includes at least one PEEK polymer. As used herein, a
PEEK
polymer denotes any polymer having, relative to the total number of moles of
recurring units, at
least 50 mol% of a recurring unit (RpEE0 represented by the following formula:
0
0 0 __
Rli Rli RI.
,(1)
where R1, at each instance, is independently selected from the group
consisting of a halogen, an
alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic
acid, an ester, an amide,
an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an
alkali or alkaline earth
metal phosphonate, an alkyl phosphonate, an amine and an quaternary ammonium;
and i, at each
instance, is an independently selected integer from 0 to 4. In some
embodiments, each i is zero.
For clarity, in Formulae (1), each of the benzene rings has 4 ¨ i ring carbons
bonded to a
hydrogen atom, where i is from 0 to 4, selected independently for each i in
Formula (1). For
example, referring to Formula (1), if i = 1 for the left most benzyl ring, 3
of those benzyl carbons
are bonded to a hydrogen and one is bonded to an
Analogous notation is used for the other
formulae herein. In some embodiments, recurring unit (RpEE0 is represented by
the following
formula:
0
____________________ 0 0
¨11 ¨K-11 /
R11 Rli Rl.
1
¨ . (2)
In some such embodiments, each i is zero.
In some embodiments, the PAEK polymer has at least about 60 mol%, at least
about 70
mol%, at least about 80 mol%, at least about 90 mol%, at least about 95 mol%
or at least about
99 mol% recurring unit (RpEE0, relative to the total number of moles of
recurring units in the
PEEK polymer. In some embodiments, the at least one PEEK polymer includes one
or more
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recurring units (R*pEEK), in addition to recurring unit (RpEEK). Each of the
one or more recurring
units (R*pppi0 is represented by Formula (1) or (2), and is distinct from each
of the other
recurring units in the polymer. In such embodiments, the total concentration
of the one or more
recurring units (R*pEEK) and the recurring unit (RpEEK) is more than about 50
mol%, at least
about 60 mol%, at least about 70 mol%, at least about 80 mol%, at least about
90 mol%, at least
about 95 mol% or at least about 99 mol%, relative to the total number of moles
of recurring units
in the PEEK polymer.
In some embodiments, the concentration of the at least one PEEK polymer,
relative to the
total weight of the polymer composition, is at least about 30 wt.%, at least
about 40 wt.%, at
least about 50 wt.% or at least about 55 wt.%. Additionally or alternatively,
the concentration of
the at least one PEEK polymer, relative to the total weight of the polymer
composition, is no
more than about 80 wt.%, no more than about 75 wt.% no more than about 70 wt.%
or no more
than about 65 wt.%. The person of ordinary skill in the art will recognize
that additional PEEK
polymer concentrations within the explicitly disclosed ranges are contemplated
and within the
scope of the present disclosure. For clarity, in embodiments in which the at
least one PEEK
polymer includes a plurality of PEEK polymers, the total concentration of the
PEEK polymers in
the polymer composition is within the ranges described above.
The Polyphenylsulfone Polymer
The polymer compositions includes at least one PPSU polymer. As used herein, a
PPSU
polymer denotes any polymer having, relative to the total number of moles of
recurring units, at
least 50 mol % of a recurring unit (RpPsu) represented by the following
formula:
0
0 0 __
I I
0
R2i
R2i R2 R2
, (3)
where R2, at each instance, is independently selected from a halogen, an
alkyl, an alkenyl, an
alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an
amide, an imide, an alkali or
alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline
earth metal phosphonate,
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an alkyl phosphonate, an amine, and a quaternary ammonium; and j, at each
instance, is an
independently selected integer from 0 to 4. Preferably each j is zero. In some
embodiments,
recurring unit (Rppsu) is represented by the following formula:
0
0 0 __
0
R2i R2j R2i R2i . (4)
In some such embodiments, each j is zero.
In some embodiments, the PPSU polymer has at least about 60 mol%, at least
about 70
mol%, at least about 80 mol%, at least about 90 mol%, at least about 95 mol%
or at least about
99 mol% recurring unit (Rppsu), relative to the total number of moles of
recurring units in the
PPSU polymer. In some embodiments, the at least one PPSU polymer includes one
or more
recurring units (R*ppsu), in addition to recurring unit (Rppsu). Each of the
one or more recurring
units (R*ppsu) is represented by Formula (1) or (2), and is distinct from each
of the other
recurring units in the polymer. In such embodiments, the total concentration
of the one or more
recurring units (R*ppsu) and the recurring unit (RpEEK) is more than about 50
mol%, at least
about 60 mol%, at least about 70 mol%, at least about 80 mol%, at least about
90 mol%, at least
about 95 mol% or at least about 99 mol%, relative to the total number of moles
of recurring units
in the PPSU polymer.
In some embodiments, the concentration of the at least one PPSU polymer,
relative to the
total weight of the polymer composition, is at least about 10 wt.%, at least
about 15 wt.%, at
least about 20 wt.%, at least about 25 wt.% or at least about 30 wt.%.
Additionally or
alternatively, the concentration of the at least one PPSU polymer, relative to
the total weight of
the polymer composition, is no more than about 60 wt.%, no more than about 50
wt.%, no more
than about 55 wt.%, no more than about 50 wt.%, no more than about 45 wt.% or
no more than
about 40 wt.%. The person of ordinary skill in the art will recognize that
additional PPSU
polymer concentration ranges within the explicitly disclosed ranges are
contemplated and within
the scope of the present disclosure. For clarity, in embodiments in which the
at least one PEEK
polymer includes a plurality of PEEK polymers, the total concentration of the
PEEK polymers in
the polymer composition is within the ranges described above.
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Additives
As noted above, in some embodiments, the polymer composition can include one
or more
additives. The additives can be selected from the group consisting of
ultraviolet light stabilizers,
antioxidants, pigments, processing aids, lubricants, and radiopaque compounds
(including, but
not limited to, barium sulfate, bismuth trioxide, bismuth oxychloride, and
bismuth subcarbonate.
Pigments can be particularly desirable additives in the polymer composition,
to impart
desirable aesthetic qualities to the denture frame. In light of the desire for
surreptitious use,
aesthetics are a significant consideration with respect to denture frames. The
more the denture
frame can be hidden from casual sight and the more the frame blends into the
oral environment,
the more concealed the use of the denture frame (and the ultimate denture).
Pigments
incorporated into the polymer composition of the denture frame to impart
aesthetic qualities to
help conceal use in the oral environment can include, but are not limited to,
TiO2 (e.g. rutile,
anatase or brookite) (white), coumarin (yellow), lapis lazul (blue) or any
combination of two or
more thereof. In embodiments in which the polymer composition includes a
pigment, the total
concentration of pigments, relative to the total weight of the polymer
composition, can be at least
about 0.1 parts per hundred by weight ("pph"), at least about 1 pph, at least
about 1 pph, at least
about 2 pph or at least about 3 pph. In some embodiments, the total
concentration of pigments,
relative to the total weight of the polymer composition, is no more than about
25 pph, no more
than about 15 pph, no more than about 10 pph or no more than about 7 pph. A
person of
ordinary skill in the art will recognize that additional ranges of total
pigment concentration
within the explicitly disclosed ranges is contemplated and within the scope of
the present
disclosure.
Significantly, applicants discovered that inclusion of particulate additives
at relatively
high loading levels can cause premature breakage of the frame. One class of
particulate
additives is inorganic particles having an average primary particle diameter
of 100 including, but
not limited to, TiO2. Particulate additives have a general spherical
appearance. Upon close
examination, crystalline particulate additives, such as inorganic particles,
have facets
corresponding to the underlying crystal lattice, but nevertheless have roughly
equivalent spatial
dimensions from the geometric center. As described below, portions of the
denture frames of
interest herein are relatively thin (e.g. having a width less than 5 mm or
even less than 2 mm).
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Frequent insertion and removal of the denture frame from the oral cavity, as
well as mastication,
during normal use places a significant amount of flexural strain on the
denture frame. Applicant
found that inclusion of particulate additives at relative high loading levels
compromises the
mechanical integrity of the denture frame and significantly reduces the
lifetime of the denture
frames. For the denture frames of interest herein, the total concentration of
particulate fillers is
less than about 30 wt. %, less than about 20 wt. %, less than about 10 wt. %,
less than about 5
wt. %, less than about 2 wt. %, relative to the total weight of the polymer
composition. The
person of ordinary skill in the art will recognize additional particular
filler concentrations within
the explicitly disclosed ranges are contemplated and within the scope of the
present disclosure.
In some embodiments, the particulate additives have an average primary
particle diameter
(length in the longest dimension of the particle) of from about 100 nanometers
("nm") to about 5
micrometers ("jam"). In such embodiments, the particulate additives can have a
distribution of
particle diameters such that at least about 80%, at least about 95%, or at
least 99% of the primary
particles have a diameter greater than about 40% of the average diameter and
less than about
700% of the average diameter. In further embodiments, the particulate
additives can have a
distribution in primary particle diameters such that at least about 80%, at
least about 95%, or at
least 99%, of the primary particles have a diameter greater than about 40% of
the average
diameter and less than about 300% of the average diameter. In alternative or
additional
embodiments, the particulate additives can have a distribution of primary
particle diameters such
that at least about 95% or at least 99% of the primary particles have a
diameter greater than about
45% of the average diameter and less than about 200% of the average diameter.
A person of
ordinary skill in the art will recognize additional ranges of average primary
particle diameter and
primary particle diameter distributions within the explicitly disclosed ranges
above are
contemplated and within the scope of the present disclosure. Primary particle
sizes (as well as
average primary particle sizes and corresponding distributions) can be
determined by
transmission electron micrographs ("TEM"). For clarity, "primary" particle
refers to the
unagglomerated particle. Due to their small size, the primary particles tend
to form agglomerates
because of vad der Waals forces. Nevertheless, the primary particles can be
clearly seen in TEM
images.
In some embodiments, the polymer composition is free of a fibrous fillers.
Fibrous fillers
include, but are not limited to, glass fibers and carbon fibers. The presence
of fibrous fillers in
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oral application settings can present health issues. Accordingly, in some
embodiments, the
polymer composition has less than about 10 wt.%, preferably less than 5 wt.%
of a fibrous filler,
relative to the total weight of the polymer composition.
Fabrication of Denture Frames
The denture frames described herein are desirably fabricated using a milling
approach.
Desirable milling approaches involve cutting a blank including the polymer
composition to
produce the denture frame (also known as subtractive manufacturing or machine
milling).
Desirably, the blanks are formed by extruding the polymer composition into a
basic shape (e.g. a
rod) subsequently cutting the shape to have the desired thickness.
Advantageously, the
fabrication method is free of injection molding approaches with respect to
blank or denture frame
fabrication.
As mentioned above it was surprisingly found that denture frames including the
polymer
composition described herein, when fabricated using selected milling methods,
had significantly
improved dimensional stability, relative to corresponding denture frames
fabricated with
injection molding methods. In injection molding, the molten polymer
composition is injected
into a mold having an inner cavity forming the negative of the intended
denture frame design or
injection molded into a mold having an inner cavity forming a blank and
subsequently milled
into a denture frame (described in detail below). It was surprisingly found
that the polymer
composition of the denture frame fabricated with injection molding techniques
exhibited
significantly compromised dimensional stability and, correspondingly, the
dimensional fidelity
of the denture frame with its original, intended design. In at least some
instances, the loss of
fidelity resulted in eventual inadequate fitment of the denture frame to the
extent that it was an
unacceptable for use in the patient's mouth. On the other hand, denture frames
fabricated using a
milling approach had significantly increased dimensional stability and
corresponding fidelity to
the design of the denture frame.
A desirable milling approach involves cutting an extruded blank (as described
below)
formed from the polymer composition to produce the denture frame. During
milling, a cutting
tool is used to remove material of the blank to form the denture frame. In one
embodiment, the
cutting tool has cutting edges (e.g. a drill bit including, but not limited
to, a router bit) that are
contacted with the blank to remove material of the blank corresponding to the
negative design of
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the denture frame. Based on the disclosure herein, the person of ordinary
skill in the art will
know how to select an appropriate cutting tool as well as use parameters such
as rotation
frequency and routing speed according the specific denture frame features and
polymer
composition. In other embodiments, a laser can be used as a cutting tool.
Based on the
disclosure herein, the person of ordinary skill in the art will know to
appropriately select a laser
and use parameters such as pulse rate and raster speed according to the
specific denture frame
features and polymer composition.
In some embodiments, the cutting tool can be desirably controlled using a
computer
processor. In such embodiments, the computer processor can be in electronic
communication
with one or more controllers that move the cutting tool and control its use
parameters (e.g.
rotation speed of a drill bit). The computer processor can also be in
electronic communication
with a memory (e.g. processor cache, random access memory or other physical
memory
including, but not limited to, a hard drive, a solid state drive, and
universal serial bus storage)
containing a digital representation of the denture frame. The computer
processor can access the
memory and control the positioning, as well as the use parameters of the
cutting tool, to remove
polymer composition from the blank and form the desired denture frame.
Examples of such
computer aided milling approaches include, but are not limited to, CAD/CAM, in
which a
computer aided design ("CAD") software is used to create digital file
containing a digital
representation of the denture frame, readable by a computer processer, and a
computer aided
manufacturing ("CAM") is used to read the digital file and control the cutting
tool to fabricate
the denture frame as described above according to the digital representation.
Machines for
implementing CAM methods moving the cutting tool or object to be milled in
various directions.
CAM machines can be 3-axis (corresponding to the 3 translation axes), 4-axis
to 6-axis (3
translation axes + 1 to 3 rotational axis) or 7-axis apparatuses. Five-axis
and 7-axis CAM
machines can be particularly desirable in light of the complicated design
features of a denture
frame. In some embodiments, the digital representation can be obtained using a
digital file
containing a digital representation of a patient's mouth, for example, obtain
by a direct optical
scan of the patient's mouth or an optical scan of a mold of a patient's mouth.
Using the scan, the
denture frame design (e.g. physical dimensions and features of the denture
frame), and
corresponding digital file, can be produced by using CAD.
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The blank is a solid block of the polymer composition. The blank can be any
shape or
size suitable for use with a milling machine. In some embodiments, cylindrical
blanks (also
known as pucks) can be desirably used. In some such embodiments, the
cylindrical blank has a
thickness ranging from about 10 millimeters ("mm") to about 70 mm or from
about 15 mm to 60
mm, and a diameter ranging from about 20 mm, from about 40 mm or from about 70
mm to
about 100 mm. The person of ordinary skill in the art will recognize
additional ranges of
thickness and diameter within the explicitly disclosed ranges are contemplated
and within the
scope of the present disclosure. The blank can be made by extruding the
polymer composition.
In some such embodiments, the polymer composition is extruded into rods having
the desired
diameter of the cylindrical blank and the rod is subsequently cut
perpendicular to the direction of
extrusion to form pucks have the desired thickness ("extruded blank"). In some
embodiments,
the polymer composition can be cut as it exits the extruder. In other
embodiments, rods can be
formed having a length larger than the blank and subsequently cut to form the
cylindrical blanks.
As noted above, while blanks may also be formed by injection molding the
polymer composition
into a mold having an inner cavity corresponding to the desired blank
dimensions, denture
frames milled from such blanks have significant dimensional instability.
Denture Frames and Dentures
In some embodiments, the denture frame is incorporated into a denture. The
denture may
be a complete denture that replaces all of a patient's teeth in a single arch
(e.g. the maxillary
(upper) or mandibular (lower) arch), or a partial denture, which replaces less
than all of a
patient's teeth in a single arch. Thus, when the denture is a partial denture,
it is designed to
accommodate a patient's existing teeth or implants. In some aspects, the
denture is a partial
removable denture that is designed to be regularly removed from the patient's
mouth for
cleaning.
Referring to Fig. 1, the components of the denture 100 include a denture frame
102,
artificial gums 104 supported by the denture frame 102, and artificial teeth
106 supported by the
artificial gums 104. The artificial gums 104 preferably include at least one
acrylic polymer, and
may be colored to match a patient's gums and mimic natural gums. Similarly,
the artificial teeth
106 mimic the shape and color of natural teeth.
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In some aspects, the dental prosthesis is a denture frame, preferably a
partial removable
denture frame. The denture frame may be formed from a single piece of plastic
and may be free
of metal. As used herein, a denture frame that is free of metal includes less
than 1 % of metal by
weight of the denture frame. As used herein, "metal" means elemental metals or
alloys thereof
such as, for example, gold, silver, platinum, nickel, aluminium, stainless
steel, etc.
In some embodiments, at least a portion of the polymer composition in the
denture frame
has a crystallinity greater than 21 %, and the polymer composition includes
less than 63 wt. % of
the PAEK based on the total weight of the polymeric material, where the
crystallinity is
determined by measurement of the enthalpy of fusion from the second heat cycle
by differential
scanning calorimetry (DSC) according to ASTM D3418-03, E1356-03, E793-06, and
E794-06.
Referring to Figs. 2 and 3, denture frame 200 includes retention grid 202,
which is a portion of
the denture frame adapted for attachment of the artificial gums (not shown).
The retention grid
includes one or more retention holes 204 extending through denture frame 200
to aid in the
attachment of the artificial gums. The holes can have an area (e.g. opening
diameter) of less than
square millimeters ("mm"), less than 7 mm2, or less than 5 mm2. The denture
frame may
include at least two, preferably at least four, preferably at least six,
preferably at least 8 or more
holes. The holes may be positioned within the retention grid to key artificial
gum material onto
the denture frame. In other words, when the artificial gums are attached to
the denture frame, the
material of the artificial gums may extend through the holes in the retention
grid to aid in
mechanical adhesion of the artificial gums to the denture frame. Depending on
the needs of the
patient, the retention grid can be flat or curved to adhere to the shape of
the patient's existing
natural gum tissue.
The denture frame may further include a finish line. Referring again to Figs.
2 and 3,
finish line 206 is a ridge in denture frame 200 that bounds the retention grid
202 on one or more
sides of retention grid 202. When the artificial gums (not shown) are attached
to denture frame
200, finish line 206 extends along and interfaces with the a border of the
artificial gums where
the artificial gums contact denture frame 200.
Applicant found that, in conjunction with the polymer composition having
improved
flexibility and durability, denture frames having finish lines with a
substantially flat inner surface
have significantly improved structural integrity when incorporated into a
denture including an
artificial gum. As described above, a denture includes a denture frame having
a finish line in
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contact with an artificial gum. The finish line has a tip, disposed towards
the top of the denture
frame, and a base, disposed towards the bottom of the denture frame. The two
surfaces between
the top and base of the finish line are referred to as the inner surface (the
surface configured to
contact the artificial gum when the denture frame is assembled into a denture)
and the outer
surface. The finish lines of interest herein have a substantially flat inner
surface, which flexes
with the artificial gum when in use in the mouth. Relative to finish line
designs in which the
inner surface is cupped to help to retain the artificial gum in the denture
frame, the stress placed
on the finish lines of interest herein resulting from flexing is significantly
reduced, due to the
substantially flat inner surface, as described in more detail below. As used
herein, a substantially
flat inner surface refers to a surface that is oriented within 20 degrees of
an axis that is
perpendicular to (i) to the base and (ii) the direction of the finish line;
("Reference Axis"). The
inner surface is oriented within 20 degrees of the Reference Axis over at
least 85 % over the
surface including the tip and extending towards the base. In some embodiments,
the inner
surface is oriented within 20 degrees of the Reference Axis over at least 90
%, at least 95 %, or
at least 99 % over the surface including the tip and extending towards the
base. In some
embodiments, the finish line has a linear distance from the tip to the base in
a cross section of the
finish line from about 0.5 mm to about 1.5 mm, over at least 90 %, at least 95
% or at least 99 %
of the length of the finish line. In some embodiments, the finish line has a
substantially flat inner
surface along at least 90 %, at least 95 %, or at least 99 % of the length of
the finish line. The
length of the finish line is its length along the tip from endpoint to
endpoint (e.g. start to finish).
The substantially flat surface can be further understood by looking at a cross
section of
the finish line perpendicular to its direction. The direction of the finish
line can be determined
by viewing a denture frame in a top down orientation. In such a perspective,
the tip of the finish
line traces out a curve. At any point along the finish line (e.g. the point at
which a cross section
is taken), its direction is oriented along the tangent line at that point.
Fig. 4 is a schematic
depiction showing a top-down view of a portion of a denture frame showing a
finish line.
Referring to Fig. 4, finish line 402 is adjacent to retention grid 404. The
orientation of finish line
402 at point 406 is along direction 408. Similarly, the orientation of finish
line 402 at point 410
is along direction 412. The length of finish line 402 is its length from
endpoint 414 to endpoint
416.
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With respect to the cross section of the finish line, Fig. 5 is a schematic
depiction of a
perspective view of a region of a denture frame showing a finish line. Denture
frame region 500
has finish line 502 adjacent retention grid 504. At point 506, finish line 502
has cross section
508, which is perpendicular to the direction of finish line axis 510. Axis 512
is in the plane of
cross section 508, and intersects base 509 of finish line 502 at point 511 on
outer surface 514 and
at point 513 on the inner surface (not labelled).
Referring to Fig. 6, finish line 502 has outer surface 514 and inner surface
516. Outer
surface 514 is oriented away from retention grid 504 and inner surface 516 is
oriented towards
retention grid 504. Inner surface 516 is a substantially flat surface. Inner
surface 516 is oriented
within 20 degrees of Reference Axis 518 over at least 85 %, at least 90 %, at
least 95 %, or at
least 99 % over the region of inner surface 516 extending from tip 520 and
towards base 509. In
some embodiments, inner surface 516 is substantially flat along at least 90 %,
at least 95 %, or at
least 99 % of the length of finish line 502.
The substantially flat inner surface allows greater flexing of the finish line
without
breaking, relative to alternative finish line designs. In particular,
alternative finish lines having a
cupped inner surface are widely used in thermoplastic denture frames, at least
because (a) they
help to hold the artificial gum in place and (b) they help to prevent food and
other debris in the
mouth from being trapped between the artificial gum and the finish line. Fig.
7 is a schematic
depiction of a cross section of a portion of a denture displaying a finish
line with a cupped inner
surface and a portion of an artificial gum. Referring to Fig. 7A, Finish line
702 has cupped inner
surface 704, which helps to retain artificial gum 706. Cupped inner surface
704 helps to restrict
movement of gum 706 in direction 708 (opposite to retention grid 710), as well
as to help
prevent debris (e.g. food) from becoming trapped between artificial gum 706
and finish line 702.
However, when used in the mouth, artificial gum 706 and finish line 702 can
flex (other
components of the denture frame can also flex). It was found that such flexing
can place
significant stress on finish line 702, which may cause breakage. Fig. 7B
depicts finish line 702
upon flexing, as previously described. Because of cupped inner surface 704, as
artificial gum
706 flexes, artificial gum 706 and finish line 702 are pushed apart, creating
cavity 714 and
causing finish line 702 to deform significantly under the applied stress, as
schematically depicted
by region 712. The applied stress can cause finish line 702 to break, for
example in region 712,
due to its relatively thin design.
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Finish lines incorporating a substantially flat inner surface can
significantly reduce the
risk of retention line and denture frame breakage. The substantially flat
inner surface reduces the
stress on the finish line upon flexing of the artificial gum, relative to a
design having a cupped
inner surface. Because the inner surface does not help to hold the artificial
gum in place (e.g. at
least partially due to the fact that surface is substantially flat), flexing
of the finish line with
flexing of the artificial gum is significantly reduced, reducing the stress
placed on the finish line.
In other words, in the absence of bonding to the retention grid, the
artificial gum can be slidably
released from the denture frame in a direction opposite from the retention
grid (e.g. direction 522
in Fig. 6, parallel to Reference Axis 518), which helps to prevent the finish
line from holding the
artificial gum in place during flexing. Furthermore, in combination with the
polymer
composition having improved flexibility, structural integrity under flexing is
still further
improved.
The outer surface of the finish line is generally shaped to form a smooth
transition from
the base to the artificial gum. In some embodiments, the magnitude (absolute
value of) the angle
of the outer surface relative to the Reference Axis is less than that of the
inner surface, over at
least 80 %, at least 90 % or at least 95 % of the region of the inner surface
extending from the tip
and towards the base. In such embodiments, the finish line has an asymmetric
cross section in a
plane perpendicular to the length of the finish line (e.g. the cross section
lacks an axis of
symmetry parallel to the Reference Axis). For example, referring again to
Figs. 5 and 6, outer
surface 514 provides a smooth transition from base 509 (at point 511) to tip
520. The magnitude
of the angle between outer surface 514 and Reference Axis 518 is greater than
the magnitude of
the angle between inner surface 516 and Reference Axis 518 over the region of
inner surface 516
from tip 520 to location 524 (at least 80 %, at least 90 % or at least 95 % of
the region of the
inner surface extending from the tip and towards the base). Moreover, cross
section 508 of finish
line 502 depicted lacks an axis of symmetry parallel to Reference Axis 518. In
other
embodiments, the magnitude of the angle of the outer surface relative to the
Reference Axis is
substantially the same (within 10 ) as that of the inner surface from the tip
to the base. In such
embodiments, the finish line has a symmetric cross section in a plane
perpendicular to the length
of the finish line (e.g. the cross section has an axis of symmetry parallel to
the Reference Axis).
For example, Fig. 8 is schematic depiction of a cross section of a portion of
a denture frame
showing a finish line having a symmetric cross section. Finish line 802 has
substantially flat
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inner surface 804 and outer surface 806. The magnitude of the angle of outer
surface 806 with
Reference Axis 808 is substantially the same magnitude of the angle of inner
surface 804 with
Reference Axis 808. Moreover, cross section of finish line 802 has an axis of
symmetry along
Reference Axis 808. Reference Axis 808 is perpendicular to axis 810.
The denture frame may also include rests or clasps, which in the context of a
partial
removable denture frame, anchor the denture frame in the patient's mouth by
friction fitting the
denture frame to the patient's existing natural teeth or implants. Applicants
have surprising
found that denture frames made from the polymer composition exhibit increased
toughness,
flexibility, and dimensional stability allowing for the use of clasps and
rests that improve fit and
retention of the denture frame.
Referring again to Figs. 2 and 3, In some embodiments, denture frame 200 may
include at
least one clasp 208 that that extends from denture frame 200 to wrap around
and grip undercut
214 of patient's natural tooth 210 or implant (not shown), thereby friction
fitting denture frame
200 in patient's mouth 212.
It was discovered that the increased flexibility and reduced brittleness of
the polymer
composition allows design of clasps that are more durable and fit farther into
the undercut of a
patient's existing teeth or implants to provide better fit and retention than
has previously been
possible with, for example, metal denture frames or denture frames having a
corresponding
polymer compositions containing PEEK as the only polymeric component of the
polymer
composition.
Referring again to Figs. 2 and 3, in some embodiments, denture frame 200
includes rests
216 that aid in holding denture frame 200 in position in patient's mouth 212.
A rest is a portion
of the denture frame extending onto the bite surface of a patient's natural
tooth or implant.
Because the rest may come into contact with an opposing tooth during chewing,
it must be
impact resistant and can become abraded. It was found that the polymer
composition is
particularly well-suited for use in rests because of its toughness and
flexibility.
EXAMPLES
The invention will be now described in more detail with reference to the
following
examples, whose purpose is merely illustrative and not intended to limit the
scope of the
invention.
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Starting Materials
The following materials were used to prepare the Examples:
KetaSpire0 PEEK KT-820 NL Q available from Solvay Specialty Polymers USA,
L.L.C.
Radel0 PPSU R-5000 NT and R-5100 P NT available from Solvay Specialty Polymers
USA,
L.L.C.
Titanium dioxide (TiO2) ¨ Grade : TiPure0 R105 available from Chemours.
Blend Preparation
Each formulation was melt compounded using a 26 mm diameter Coperion0 ZSK-26
co-
rotating partially intermeshing twin screw extruder having an L/D ratio of
48:1.
In each case, the resins and additives were fed at barrel section 1 using a
gravimetric
feeder at throughput rates in the range 30-40 lb/hr. The extruder was operated
at screw speeds of
around 200 RPM. Vacuum was applied at barrel zone 10 with a vacuum level of
about 27 inches
of mercury. A single-hole die was used for all the compounds and the molten
polymer strand
exiting the die was cooled in a water trough and then cut in a pelletizer to
form pellets
approximately 3.0 mm in length by 2.7 mm in diameter.
Injection Molding
The example formulations were injection molded to produce 3.2 mm (0.125 in)
thick
ASTM tensile and flexural specimens for mechanical property testing. Type I
tensile ASTM
specimens and 5 in x 0.5 in x 0.125 in flexural specimens were injection
molded.
Mechanical Testing
Mechanical properties were tested using injection molded test specimens which
consisted
of 1) ISO bars 80 x 10 x 4 mm, and 2) 2 x 3 x 0.125 in plaques. The following
test methods
were employed in evaluating the compositions :
ASTM D-638 : Tensile properties : tensile strength at yield, tensile modulus
and tensile
elongation at yield
ASTM D790: flexural properties
ASTM D792: density and specific gravity
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ASTM D256 : Notched Izod impact resistance
The results of the mechanical testing are shown below in Table 1.
Table 1
Example No. Cl El E2 E3
PEEK, KetaSpire KT-820 NL Q 100 62.9 62.9
62.9
PPSU, Rader R-5100 P NT -- 36.9 36.9 6.9
PPSU, Radel R-5000 NT -- -- -- 30
Zinc oxide -- 0.1 0.1 0.1
Zinc stearate -- 0.1 0.1 0.1
TiO2, TiPure R-105 (pph) -- 0 3 5
Color concentrate package (pph) -- -- 0.024 0.018
Density (g/cm) -- 1.28-1.32 1.32 --
Tensile Strength at yield (MPa) -- 84 87
87.8
Tensile Modulus (GPa) 3.5 3.1 3.22
3.18
Tensile Elongation at Yield (%) 5.2 4 6.1
6.19
Tensile Elongation at Break (%) 78 30 -- 90
Flexural Modulus (GPa) 3.7 3.1 --
3.25
Flexural Strength (MPa) 146 122 -- 128.9
Notched Izod Impact (Jim) 91 100 100
98.2
Dimensional Stability Testing
The dimensional stability of denture frames made from extruded and injection
molded
cylindrical blanks of the composition of Example 3 was assessed.
The composition of Example 3 was injection molded into cylindrical blanks
(i.e. blanks)
measuring 98 mm in diameter and 18 mm in thickness. Blanks of identical size
were also
prepared by extruding of a rod of the composition of Example 3 and cutting the
rod to form
extruded blanks.
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A mandibular impression was taken of a patient's teeth, from which a plaster
cast was
prepared. The plaster cast was scanned using a 3Shape D750 Lab Scanner to
create an electronic
model of the patient's teeth. A denture frame was designed using a computer
employing
CAD/CAM technology and identically-shaped denture frames were milled from each
blank.
Following milling, the fit of each denture frame was assessed on the cast
model by visual
inspection. A framework was considered seated when all rests on the denture
frame came into
full contact with their rest seats on the cast model. Each denture frame fit
well on the cast model
directly after milling. After approximately 24 hours, the fit of each denture
frame was reassessed
by visual inspection. While the denture frames milled from extruded blanks
continued to exhibit
good fit, the denture frames milled from injection molded blanks were found to
have distortions
of over 2 mm from their original dimensions, rending the frames unusable.
Accordingly, it was unexpectedly discovered that dimensional stability is
increased and
fit is maintained when the denture frames are milled from extruded blanks as
compared with
injection molded blanks.
Color Stability Testing
The color stability of the compositions of Example 3 and Comparative Example
Cl after
exposure to coffee (a typical staining agent found in the oral environment)
was evaluated using a
modified AL-PCL-MEC-LTM-077 test method.
Six test specimens in the form of color chips were prepared from each of the
materials by
injection molding.
A coffee staining solution was prepared by adding 20 g Nescafe ClasicoTM dark
roast
coffee, available from Nestle, to 1000 ml of boiling distilled water.
Color change for each specimen was evaluated using an XRite0 Color i7800
spectrophotometer. The spectrophotometric reflectance was measured from 360 -
750 nm, with
measurements on each test specimen made in triplicate.
Each specimen was conditioned by placing it in distilled water at 37+/-1 C for
24 hours
before spectrophotometric data was collected as a baseline measurement.
Following
conditioning, three test specimens of each material were soaked in the coffee
staining solution,
and the remaining three specimens were soaked in distilled water as a control,
at 37+/-1 C for 30
days. The test specimens were removed after 30 days and analyzed with the
spectrophotometer.
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Each test specimen was cleaned by placing it in a Ney Ultrasonic 28B cleaner
for 10 minutes at
room temperature (21 C). The cleaning solution was Ultrasonic Solution #4
Tartar and Stain
Remover available from Quala Dental Products. Spectral analysis was also
performed following
cleaning.
The color was measured according to the CIE 1976 L-a-b coordinates standard
where the
L* coordinate represents the lightness (black to white) scale, the a*
coordinate represents the
green-red chromaticity and the b* scale represents the blue-yellow
chromaticity. Delta E
[AE=((AL)2 + (Aa)2 + (Ab)2)1/2] values were calculated from the
spectrophotometer results as
the difference between each reading and the baseline measured after
conditioning and prior to
staining. The AE value was used to assess the color stability, with higher
values indicating a
higher level of staining.
The results of the color stability testing are shown below in Table 2.
Table 2
T2 Difference
Ti
After After
30 days
Cleaning Cleaning
AE
AE (T1-T2)
Composition of
Comparative
Example Cl
C2 Coffee 5.861 4.100 1.761
C4 Water 0.676 0.552 0.123
Composition of
Example E3
E4 Coffee 17.557 0.410 17.146
C5 Water 0.544 0.366 0.178
As shown in Table 2, the compositions of Example 3 and Comparative Example 1
each
exhibited increased staining after 30 days in the coffee staining solution as
shown by the AEs of
17.557 and 5.861, respectively. After cleaning, however, the composition of
Example 3
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unexpectedly exhibited a significantly greater reduction in staining and a
lower AE than the
composition of Comparative Example 1.
Should the disclosure of any patents, patent applications, and publications
which are
incorporated herein by reference conflict with the description of the present
application to the
extent that it may render a term unclear, the present description shall take
precedence.
Further Inventive Concepts:
1. A denture frame comprising:
a polymer composition comprising:
(i) from about 30 wt.% to about 80 wt.% of at least one poly(ether ether)
ketone
("PEEK") polymer, relative to the total weight of the polymer composition;
(ii) from about 10 wt.% to about 60 wt.% of at least one polyphenylsulfone
("PPSU")
polymer, relative to the total weight of the polymer composition; and
(iii) less than about 30 wt.% of a particulate filler comprising a pigment.
2. The denture frame of inventive concept 1, wherein the particulate filler
as an average
primary particle diameter of 100 nm to 5 jam.
3. The denture frame of any one of inventive concepts 1 or 2, wherein the
particulate filler
comprises TiO2.
4. The denture frame of any one of inventive concepts 1 to 3, wherein the
polymer
composition is free of a fibrous filler.
5. The denture frame of any one of the inventive concepts 1 to 4, further
comprising at least
one finish line including a substantially flat inner surface.
6. The denture frame of inventive concept 5, wherein the finish line as an
asymmetric cross
section in a plane perpendicular to the length of the finish line.
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7. The denture frame of any one of inventive concepts 1 to 6, further
comprising a retention
grid comprising at least one retention hole having an area of less than about
10 mm2.
8. A denture comprising the denture frame of any one of inventive concepts
1 to 7, wherein
the denture comprises an artificial gum disposed on the retention grid and in
contact with the
inner surface of the finish line.
9. The denture of inventive concept 8, further comprising at least one
artificial tooth in
contact with the artificial gum.
10. The denture frame of any one of inventive concepts 1 to 9, further
comprising a rest.
11. The denture frame of any one of inventive concepts 1 to 10, further
comprising a clasp.
12. The denture frame of any one of inventive concepts 1 to 11,
wherein the at least one PEEK polymer is represented by either one of the
following
formulae:
= 0
0 0 ___
Rl.
Rli RI i
and (1)
(7
)
0 0 ) 0
R11 RI; RI
¨ (2)
where Rl, at each instance, is independently selected from the group
consisting of a halogen, an
alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic
acid, an ester, an amide,
an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an
alkali or alkaline earth
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metal phosphonate, an alkyl phosphonate, an amine and an quaternary ammonium;
and i, at each
instance, is an independently selected integer from 0 to 4, preferably each i
is zero and
wherein the at least one PPSU polymer is represented by either one of the
following
formulae:
0
0 .0 0
0
R2i R2i R2i R2
and (3)
0
0 0
0
R2i R2i R2i R2
(4)
where R2, at each instance, is independently selected from a halogen, an
alkyl, an alkenyl, an
alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an
amide, an imide, an alkali or
alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline
earth metal phosphonate,
an alkyl phosphonate, an amine, and a quaternary ammonium; and j, at each
instance, is an
independently selected integer from 0 to 4, preferably each j is zero.
13. The denture frame of any one of inventive concepts to 12, wherein the
concentration of
the at least one PEEK polymer, relative to the total weight of the polymer
composition, is at least
about 30 wt.%, at least about 40 wt.%, at least about 50 wt.% or at least
about 55 wt.% and is no
more than about 80 wt.%, no more than about 75 wt.% no more than about 70 wt.%
or no more
than about 65 wt.%.
14. The denture frame of any one inventive concepts 1 to 13, wherein the
concentration of
the at least one PPSU polymer, relative to the total weight of the polymer
composition, is at least
about 10 wt.%, at least about 15 wt.%, at least about 20 wt.%, at least about
25 wt.% or at least
about 30 wt.% and is no more than about 60 wt.%, no more than about 50 wt.%,
no more than
about 55 wt.%, no more than about 50 wt.%, no more than about 45 wt.% or no
more than about
40 wt.%.
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15. The denture frame of any one of inventive concepts 1 to 14, wherein the
total
concentration of pigments, relative to the total weight of the polymer
composition, is at least
about 0.1 parts per hundred by weight ("pph"), at least about 1 pph, at least
about 1 pph, at least
about 2 pph or at least about 3 pph and no more than about 25 pph, no more
than about 15 pph,
no more than about 10 pph or no more than about 7 pph.
16. A method of forming a denture frame, the method comprising:
milling the denture frame of any one of inventive concepts 1 to 16 from a
blank
comprising a polymer composition.
17. The method inventive concept 16, wherein the blank comprises a
cylindrical blank.
18. The method of inventive concept 17, wherein the cylindrical blank has a
thickness from
about 10 mm to about 70 mm and a diameter about 20 mm to about 100 mm.
19. The method of inventive concept 18, further comprising fabricating the
blank, wherein
the fabricating comprises extruding the polymer composition into a rod having
a diameter from
about 20 mm to about 100 mm and cutting the rod to form the cylindrical blank.
20. The method of any one of inventive concepts 16 to 19, wherein the
milling comprising
milling the blank using a computer-aided manufacturing ("CNC") machine to form
the denture
frame.
21. The method of inventive concept 20, wherein:
the CNC machines includes a computer processor in electronic communication
with a
memory;
the computer processor accesses the memory to read a digital file comprising a
digital
representation of the patient's mouth; and
the CNC guides a cutting tool according to the digital representation of the
patient's
mouth to remove material from the blank and to form the denture frame.
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22. The method of inventive concept 21, further comprising creating the
digital
representation of the patient's mouth, wherein the creating comprises
performing an optical scan
of the patient's mouth.
23. The method of inventive concept 21, further comprising creating the
digital
representation of the patient's mouth, wherein the creating comprising
performing an optical
scan of a mold of the patient's mouth.
24. The method of any one of inventive concept claim 21 to 23, wherein the
cutting tool
comprises a drill bit or a laser.
26
