Dental Crown Construction and Method

This invention is related to dental crowns, particularly to an inexpensive crown construction adapted for use with children who do not have their permanent teeth but require the use of a protective crown restoration for primary teeth. A stainless steel crown construction is considerably less expensive than the molded permanent crowns which are well known to the dental profession. The stainless steel construction has two problems, the first being that the "silver" color of the steel crown is not acceptable, and the second being that the use of a polymeric veneer cosmetic overlay involves difficult bonding and strength problems.

This is an inexpensive dental crown having a stainless steel cap with an outer cosmetic facing material made from a composite of polymeric material securely bonded to the front surface of the steel cap structure. A suitable bonding agent is used, such as an anaerobic material that is cured by exposure to light with the addition of an apparatus and method for removing the oxygen from the surface to be bonded.

Cut-out portions are provided at the corners of the stainless steel cap structure to enhance the attachment of the cosmetic overlay and permit the thickness of the corners of the cosmetic overlay material to be increased and thus reinforced. Also reinforcing filament fibers may be imbedded in the overlay material. These fibers extend from side to side across the stainless steel crown structure and into the cut-out portions to reinforce and tie together the corner portions of the cosmetic overlay material which is applied to the front face of the stainless steel body of the crown structure. To further enhance the attachment of the cosmetic overlay, the facial surface of the stainless steel is etched by blasting the surface with aluminum oxide which provides a microscopic textured retentive surface to which a bonding agent such as an anaerobic material will securely adhere. The crown with the bonding agent applied to the surface thereof may be cured in a vacuum to produce an optimum bonding surface having an opaque material applied thereto. The composite polymeric cosmetic material is then applied to the prepared outer surface of the preformed stainless steel backing and the crown assembly is then cured in an appropriate curing atmosphere such as in a heated vacuum with light applied thereto.

FIG. 1 is a perspective view of a completed crown embodying the invention.

FIG. 2 is a perspective view of a crown substrate with reinforcing fibers in place.

FIG. 3 is a perspective view similar to FIG. 2 showing a different configuration of the stainless steel substrate and the corner notches thereof.

FIG. 4 is a fragmentary sectional view taken substantially along the line 4--4 of FIG. 1.

As illustrated in the accompanying drawings, this invention provides an inexpensive dental crown construction which includes a structurally durable cap 10 made from a durable material such as stainless steel for enclosing a tooth to be repaired.

Said cap defines a tooth receiving cavity therewithin and has a curved front panel 10a and a curved back panel 10b with, a pair of notch openings 12 formed at the upper corners of the front panel 10a. As shown in FIG. 2, each opening extends substantially half the width of the cap.

The purpose of the openings 12 is to permit the thickness of the composite (polymeric) facing material to be increased at the corner biting areas to reinforce and strengthen these areas of the crown.

The facial surface of the stainless steel cap is blasted with aluminum oxide particles which provide a microscopically etched retentive surface which is cleaned ultrasonically and a composite bonding agent is applied and securely adheres to this surface. An MDP composite resin and adhesive has been found to be a suitable adhesive material. The bonding agent is applied and the crowns are placed in a vacuum light-curing atmosphere until the bonding agent has cured. This produces a slightly dull bonding surface to which a light colored opaque coating is applied. Composite polymeric cosmetic facing material is extruded onto the front crown surface and the crown assembly is cured with visible halogen light in a vacuum atmosphere or as prescribed by the manufacturer of the composite facing material and the facing material is ground and polished to produce the desired shape and smooth surface.

In an alternative form of the invention the center portion of the outer labial (front) surface of the crown 10 has a pair of anchoring tabs 15 extending down from between the notch openings 12 to engage and clamp filament elements of reinforcement material 16 which are embedded in the overlying cosmetic material and extend across into the two openings 12. A suitable high molecular weight polyethene filament material has proved to be satisfactory, such as GLASPAN which is the registered Trademark of Glaspan, Inc. of Exton, Pa., or RIBBOND which is the registered Trademark of Ribbon, Inc. of Seattle, Wash. The outer cosmetic polymeric material is thus securely bonded to the outer face of the stainless steel substrate by the reinforcing filament fibers 16 which extend laterally across the front of the stainless steel crown structure and into the openings 12 on each side thereof as shown in FIG. 2 where the thickness of the cosmetic overlay is also increased for added strength.

A modification of the notch configuration is illustrated in FIG. 3 where the notches are somewhat kidney-shaped and are designated by numeral 20. The filament segments 16 extend across into the notches and the area of the front crown surface as illustrated.