Dentistry – Method or material for testing – treating – restoring – or... – By filling – bonding or cementing
Reexamination Certificate
1999-03-01
2001-08-07
Lewis, Ralph A. (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
By filling, bonding or cementing
C523S116000, C523S217000
Reexamination Certificate
active
06270348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, generally, to a fiber reinforced dental material for use in various restorative dental procedures and, more particularly, to a silane treated high purity chopped quartz fiber reinforced composite dental material which substantially addresses the difficulties in reestablishing interproximal contact, proximal voids, finishing, postoperative sensitivity and insufficient mechanical strengths associated with known composite materials.
2. Description of the Prior Art
Following the first introduction of posterior composites almost 40 years ago, there has been an increasing interest in its development by an esthetic-oriented patient population. The early attempts to replace silver resulted in numerous clinical failures, but the driving incentive had been created. Photocuring was a big step in reducing oxygen-inhibited polymerization that is hand mixed in during a chemical cure, which subsequently reduces strengths, and increases wear rates. During this development there has been some confusion in terminology. Microfills, actually 20-50 nanometer amorphous colloidal silica filled resins, were introduced to counteract excessive wear rates. But difficulties with high surface areas and Van der Waals forces of agglomeration prevented high filler loading due to uncontrollable thick viscosity consistencies. Nonetheless, microfill composites were easy to finish and prevented early particle “plucking” or pullout associated with larger particle filler. Soon strengths were improved with “hybrids” where larger particles were mixed in with colloidal silica. Polymerized high particle-filled composites were also ground down and mixed back into a resin paste with colloidal silica and known as “heterogeneous microfills.” Currently, “universal composites” have reduced the average particle size by improving packing fractions and increased weight and volume percentages to a point where wear rates are now approaching those of silver fillings. Be that as it may, none of the particles employed in prior art particle-filled resins were ever larger than 100-200 microns. Indeed, excessively long fillers were summarily dismissed as being impractical for finishing purposes.
As an additional historical note, the progress of Bis-GMA and silane coupling combined with radiopaque barium glass filler initiated clinical trials and commercialization of tooth colored fillings for posterior teeth in the 60's. Although none of the early posterior Bis-GMA dental composite formulations were successful, significant improvements have come in stages to stimulate the use of dental resins to such an extent that they now rival amalgam as a restorative option. In fact, 23% of all dentists now indicate that composite is their material of choice for class II restorations.
Still many problems exist with the contemporary generation of posterior composites. They are still relatively difficult to handle, although experience and familiarity reduce this trouble. Concerns over, primarily, class II composite restorations have been highlighted recently through the American Dental Association, which described the most common complaints among practicing dentists. The primary objection is the inability to restore the proximal contact. Voids, particularly in the interproximal box, are a second area of criticism. Additional concerns are in the areas of finishing effort and the occurrence of post-operative sensitivity.
SUMMARY OF THE INVENTION
Accordingly, the present invention describes a chopped fiber glass reinforcement for dental filling composites wherein the individual fibers have a preferred length of approximately 3 mm and a preferred width of approximately 10 microns. In particular, high purity chopped quartz fiber is identified as an eminent performance material speciality within this new field of dental technology in addition to the more common forms of fiber, such as E-glass (electrical grade), S-glass (high tensile strength grade), C-glass (chemical grade), etc. The chopped fibers build viscosity into a dental filling paste disproportionately relative to their lengths over standard dental composite particulate reinforcement. Increasing the viscosity improves handling ability by the dentist, thus allowing for silver amalgam-like condensation for controlled placement, reduction in porosity, elimination of edge-void defects and improved reestablishment of the interproximal contact. Fiber ductility specifically permits bending and conformation within small geometrical boundaries to approximate continuous fiber strengths without excessive breakage or voids being produced. This allows greater realization of the potential fiber composite's enabling strength capacity. Chopped fiber reinforced composite exhibits Bingham Plastic behavior, through internal fiber resin extrusion, wherein it efficiently fills surface defects and internal voids. The fiber resin pre-impregnation is emphasized which favors the potential stress transfer characteristics of the stronger fibers to the weaker matrix.
Accordingly, in an embodiment of the present invention, a dental material is disclosed which includes: a resin; and a plurality of silica-based fibers mixed into the resin, wherein each of the silica-based fibers has a length of at least 1 mm.
In an embodiment, the dental material includes silica-based fibers which have a length of at least 2 mm.
In an embodiment, the dental material includes silica-based fibers which have a length of at least 3 mm.
In an embodiment, the dental material includes silica-based fibers which are less than 60% by weight silica.
In an embodiment, the dental material includes silica-based fibers which are 60-70% by weight silica.
In an embodiment, the dental material includes silica-based fibers which are greater than 70% by weight silica.
In an embodiment, the dental material includes silica-based fibers which are quartz.
In an embodiment, the dental material further includes a radiopaque material.
In an embodiment, the radiopaque material includes Barium.
In an embodiment, the radiopaque material includes Zirconium.
In another embodiment of the present invention, a method of restoration of a dental void is disclosed which includes the steps of: providing a first dental material having silica-based fibers; compacting the first dental material into a lower area of the void so as to substantially fill the lower area; providing a second non-fibrous dental material; and applying the second non-fibrous dental material to an upper area of the void upon an upper surface of the first dental material so as to substantially fill the upper area.
In an embodiment, the method further includes the step of compacting, initially, the second non-fibrous dental material into a lowermost area of the void prior to the step of compacting the first dental material.
In an embodiment of the method, the first dental material includes a resin impregnated with the silica-based fibers wherein the silica-based fibers each have a length of at least 1 mm.
In an embodiment of the method, the first dental material includes a resin impregnated with the silica-based fibers, wherein the silica-based fibers each have a length of at least 2 mm.
In an embodiment of the method, the first dental material includes a resin impregnated with the silica-based fibers, wherein the silica-based fibers each have a length of at least 3 mm.
In an embodiment of the method, the silica-based fibers are less than 60% by weight silica.
In an embodiment of the method, the silica-based fibers are 60-70% by weight silica.
In an embodiment of the method, the silica-based fibers are greater than 70% by weight silica.
In an embodiment of the method, the silica-based fibers are quartz.
In an embodiment, the method further includes the step of impregnating the first dental material with a radiopaque material.
In an embodiment of the method, the radiopaque material includes Barium.
In an embodiment of the method, the radiopaque material includes Zirconium.
Additional features and advantages of the presen
Bell Boyd & Lloyd LLC
Lewis Ralph A.
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