Patent Application
20110081830
The present invention relates to a method for finishing and fitting dental restorations such as, for example, dentures, bridges, crowns, onlays and inlays and smoothing fillings. The present invention also relates to an abrasive dental strip for finishing and fitting dentures, bridges, crowns, onlays and inlays and smoothing fillings.
Typically dental restorations such as dentures, bridges, crowns, inlays and onlays are formed in molds which may leave irregular surfaces on the restorations. Also, when dentists use dental restorations such as fitting bridges and crowns or applying onlays or inlays, or fillings, irregular surfaces initially result. It is particularly important with bridges, crowns, onlays, inlays and fillings that proper contouring of the material occur so that the margins and contouring between the bridge, crown, onlay, inlay or filling and the natural tooth material remaining be precise to prevent decay at the margins and provide good gingival health.
The present invention, in one aspect, provides a method for finishing and fitting dental restorations comprising the steps of
The abrasive protrusions, unitary with the base, may be arranged in rows, spiral, helix, or lattice fashion, or may be randomly spaced. The arrangement, height, and shape or the abrasive protrusions helps to define the rate of dental restoration surface removal and degree of polishing desired.
The protrusions of the abrasive material useful in the invention may be the same or different in shape. For example, various protrusions may have different bases configurations, i.e., different numbers of sides, and/or different degrees of slope with some bases approaching a circular shape. Generally, a triangular base is preferred. The triangular sides of the pyramidal protrusions and the trapezoidal sides of the butte protrusions may have an inward arcuate slope.
The abrasive material useful in the invention may be subjected to high and/or low temperature treatment. Optional performance enhancing surface treatments may be applied to the protrusions and the base surface to improve abrasive performance, increase abrasive endurance, aid in non-loading characteristics due to the lubricity of certain coatings, and reduce surface porosity.
The method of the present invention can be used, for example, on dental restorations such as dentures, bridges, crowns, inlays and onlays during fabrication thereof, hereinafter generally termed “dental fabrication”. The method is also useful, for example, in fitting and finishing bridges, crowns, onlays, inlays and fillings in dental offices, hereinafter generally termed “dental office applications”.
The abrasive material may be in the form of a flexible strip having a width preferably in the range of about 0.0625 inch to about 0.5 inch, more preferably about 0.0625 inch to about 0.25 inch. Narrower strips are generally more useful for dental office applications while wider strips are generally more useful for dental fabrication. The abrasive material may also be in the form of a disk preferably having a diameter of from about 0.5 inch to about 1.5 inches, more preferably from about 0.75 inch to 1 inch for use with a hand held high-speed rotary tool for use in both dental office applications and dental fabrication. The abrasive material in the form of still larger disks having diameters, for example, of up to 12 inches and larger are useful in dental fabrication.
The method of the present invention is particularly effective in finishing and fitting dental restorations. A strip or disk useful in the method of the present invention can provide both rapid removal of dental restoration material as well as providing the necessary finishing and smoothing whether the dental restoration material is metal such as gold, gold alloy, titanium, a cobalt-chromium alloy or nickel-chrome alloy; porcelain or porcelain fused to metal; or a composite resin.
The method of the present invention is also especially useful with dental composite resins such as, for example, a resin-based matrix of a bisphenol A-glycidyl methacrylate (BISMA), resin-like urethane dimethacrylate (UDMA), and an inorganic filler such as silicon dioxide silica with chemical initiators and catalysts. Engineered filler glasses and glass ceramics are used to provide such composites with wear resistance and translucency, the presence of which can make finishing and smoothing difficult.
In the method for finishing and fitting dental restorations of the present invention, the abrasive material is formed from stainless steel. Stainless steel is a particularly preferred base material in the present invention due to the intrinsic resistance of the material to corrosion, the ability to be sterilized, for example, by autoclave, a sterilizing liquid such as peracetic acid or gaseous sterilization with ethylene oxide, and the general aesthetic appeal. Stainless steel can also be readily reproducibly etched to form the abrasive material useful in the invention.
The method of the present invention is distinctly advantageous in that the abrasive used is formed by etching a pattern of protrusions from the material which forms the base, i.e. the abrasive substrate. Known abrasive materials, e.g., sandpaper and sanding disks have particulate such as, for example, garnet, aluminum oxide, silicon oxide, and other hard abrasive particles, adhered to a backing by a binder system. With such known abrasive materials, the particulate is dislodged from the surface of the abrasive to form dust during dental fabrication or deposit in a patient's mouth during dental office procedures. The abrasive material useful in the present invention is of a unitary structure and does not present such problems.
The etching process can be carried out using well-known resist and etching materials and processes. Prior to application of the photoresist to the base material, cleaning of the base material is preferably carried out. The resist coating can be applied using, for example, hot roll lamination, screen printing, gravure printing, dip coating and the like.
The mask which is used to provide the desired abrasive pattern surface is then placed on the resist covered base material. Good, i.e., intimate, contact between the resist coating and the mask is needed to achieve the desired pattern on the base material where the photoresist not covered by the mask is cured. Curing, or imaging, is achieved by exposure to light sufficient to cure, i.e., cross-link, the polymeric resist. The mask is then removed from the base material/photoresist/mask composite and the uncured photoresist is removed from the base material using a developing solution, or developer. If desired, the photoresist then remaining on the base material may be imaged again prior to etching to further ensure good adhesion of the photoresist to the base material during etching.
Etching is then performed on those portions of the base material not protected by the photoresist. The degree of etching can be adjusted by altering the concentration and temperature of the etchant solution and the method of application as is known to those skilled in the art. As etchant removes the base material, a certain portion of the base material under the mask also is exposed.
The rate of etching and the extent to which this is allowed to continue determines the shape of the protrusions. To achieve the pyramidal protrusions requires etching to a greater extent than etching to achieve the butte protrusions. To achieve mixed pyramidal protrusions and butte protrusions, having mask portions of differing surface areas can be used with larger mask areas producing butte protrusions and smaller mask areas producing pyramidal protrusion.
The rate of etching also determines the extent to which an inward arctuate slope is formed. Generally, a faster rate of etching results in a greater inward arc.
On thinner base materials where only one side of a substrate carries the abrasive pattern, both side of the base material may be etched to equalize metal stresses and reduce curling.
After etching, any remaining photoresist may be removed by techniques well known to those skilled in the art.
The thickness of the abrasive material is not particularly limited, but after etching should be suitably flexible where it will be used in strip form, for example, to smooth medial or distal portions of dental restorations or suitably stiff when used as a flat abrasive. Of course, stiffness can be provided, if necessary, by attachment to a stiff substrate such as, for example, a metal plate or synthetic resin plate having suitable stiffness.
In the method of the present invention the surface of the abrasive material can be heat treated, cryogenically treated or heat treated and cryogenically treated or metallurically altered, e.g., case hardening, for example, to form a thin harder layer on the surface of the base surface and protrusions to improve hardness as is well known to those skilled in the art.
Performance enhancing coatings may optionally be applied to the surface of the abrasive useful in the present invention. Preferred coatings include, for example, titanium nitride, chromium nitride, boron nitride and diamond or diamond-like coatings. Such coatings may be applied, for example, by chemical vapor deposition, plasma-assisted chemical vapor deposition, hypersonic plasma particle deposition, or physical vapor deposition, as appropriate for material being deposited as is well known in the art. Performance enhancing coatings such as, for example, nickel or chrome plating or plating in combination with diamond dust may also be applied to the abrasive material for use in the invention.
With respect to the drawings, like references number will generally be used with reference to like parts.
Preferably, the slope of the sides of the pyramidal protrusions or the butte protrusions can vary from slight, e.g., about 20° or less to about 45° or more, more preferably from about 25° to about 40°, most preferably from about 30° to 35°. In
The optional non-abrasive portion is generally formed by omission of any photoresist material during the etching of the stainless steel. The strips are preferably formed by laser cutting the strips from sheets of etched stainless steel. However, high definition plasma arc cutting and abrasive water jet cutting may be used.
In
After curing of the photoresist and removal of the mask, the uncured photoresist is removed by rinsing with a solution appropriate for the photoresist used. The substrate etches such that pyramidal protrusions or butte protrusions are formed under the areas of the cured photoresist with the base surface being formed in the areas having no photoresist. In some cases where pyramidal protrusions are being formed, the photoresist may be removed during the etching process.
In
In
In
A sheet of 420 spring tempered stainless steel having a thickness of about 0.032 inch was cleaned and passivated. A photoresist solution was coated onto the passivated stainless steel and dried. A mask having pattern as shown in
The stainless steel/photoresist/mask composite was exposed to 60 millijoules of light to effect imaging of the photoresist. The unexposed, uncrosslinked photoresist was then removed by rinsing with a developer solution. The stainless steel having the photoresist pattern thereon was re-exposed to 100 millijoules light to ensure adherence of the photo resist to the stainless steel during etching.
The stainless steel was etched to a depth of about 0.012 inch using 36 Baume ferric chloride solution at a temperature of 145° F. The resulting etched sheet was rinsed with water and the remaining photoresist was removed using an aqueous potassium hydroxide stripping solution.
The etched stainless steel was coated with titanium chromium nitride at a temperature of about 500° F. and subsequently cryogenically cooled at −300° F.
The resulting abrasive material had pyramidal protrusions with triangular bases. The height of the apexes of the protrusions from the base material was about 0.002 inch and a slope of about 30°. The resulting abrasive material was a coarse dental abrasive.
The material was satisfactory for cutting into strips or disks and exhibited excellent performance for dental fabrication and was suitable for use in dental office procedures.
A sheet of spring tempered stainless steel having a thickness of about 0.032 inch was cleaned and passivated. A photoresist solution was coated onto the passivated stainless steel and dried. A mask having pattern like that of
The stainless steel/photoresist/mask composite was exposed to 60 millijoules of light to effect imaging of the photoresist. The unexposed, uncrosslinked photoresist was then removed by rinsing with a developer solution. The stainless steel having the photoresist pattern thereon was re-exposed to 100 millijoules light to ensure adherence of the photo resist to the stainless steel during etching.
The stainless steel was etched to a depth of about 0.009 inch using 36 Baume ferric chloride solution at a temperature of 145° F. The resulting etched sheet was rinsed with water and the remaining photoresist was removed using an aqueous potassium hydroxide stripping solution.
The etched stainless steel was coated with titanium chromium nitride at a temperature of about 500° F. and subsequently cryogenically cooled at −300° F.
The resulting abrasive material had pyramidal protrusions with triangular bases. The height of the apexes of the protrusions from the base material was about 0.008 inch and the slope of the protrusions was about 30°. The resulting abrasive material was a medium dental abrasive.
The material was satisfactory for cutting into strips or disks and exhibited excellent performance for dental fabrication and was suitable for use in dental office procedures.
A sheet of 420 spring tempered stainless steel having a thickness of about 0.020 inch was cleaned and passivated. A photoresist solution was coated onto the passivated stainless steel and dried. A mask having pattern like that of
The stainless steel/photoresist/mask composite was exposed to 60 millijoules of light to effect imaging of the photoresist. The unexposed, uncrosslinked photoresist was then removed by rinsing with a developer solution. The stainless steel having the photoresist pattern thereon was re-exposed to 100 millijoules light to ensure adherence of the photo resist to the stainless steel during etching.
The stainless steel was etched to a depth of about 0.003 inch using 36 Baume ferric chloride solution at a temperature of 145° F. The resulting etched sheet was rinsed with water and the remaining photoresist was removed using an aqueous potassium hydroxide stripping solution.
The etched stainless steel was coated with titanium chromium nitride at a temperature of about 500° F. and subsequently cryogenically cooled at −300° F.
The resulting abrasive material had pyramidal protrusions with triangular bases. The height of the apexes of the protrusions from the base material was about 0.002 inch and the slope of the sides of the protrusions was about 30°. The resulting abrasive material was a fine dental abrasive.
The material was satisfactory for cutting into strips or disks and exhibited excellent performance for dental fabrication and was suitable for use in dental office procedures.
Although the present invention has been described with reference to preferred embodiments, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.
