Mass production of shells and models for dental restorations produced by solid free-form fabrication methods

Abstract

Solid free form fabrication techniques such as fused deposition modeling and three-dimensional printing are used to create a shell used in the manufacture of a dental restoration. Three-dimensional printing includes ink-jet printing a binder into selected areas of sequentially deposited layers of powder. Each layer is created by spreading a thin layer of powder over the surface of a powder bed. Instructions for each layer may be derived directly from a CAD representation of the restoration. The area to be printed is obtained by computing the area of intersection between the desired plane and the CAD representation of the object. All the layers required for an aesthetically sound shell can be deposited concurrently slice after slice and sintered / cured simultaneously. While the layers become hardened or at least partially hardened as each of the layers is laid down, once the desired final shaped configuration is achieved and the layering process is complete, in some applications it may be desirable that the form and its contents be heated, cooled or cured at a suitably selected temperature to further promote the integrity of solid free-form structures.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of U.S. application Ser. No. 09 / 350,604 filed Jul. 9, 1999 which claims priority to U.S. Provisional Application Ser. No. 60 / 092,432 filed on Jul. 10, 1998, both which are hereby incorporated by reference.FIELD OF THE INVENTION [0002] This invention relates to dental restorations made from ceramics, glass-ceramics as well as ceramic-matrix and polymer-matrix composite materials using solid free-form fabrication methods. The invention further relates to bodies fabricated by solid free-form techniques which can provide the matrix or skeleton of dental restorations that can be further or concurrently filled with biomimetic substances. The invention also is directed to the manufacture of shells used in the manufacture of dental restorations whereby the shells are manufactured using solid free-form fabrication methods. The invention further relates to the manufacture of models used in the manufactur...

AI Technical Summary

Benefits of technology

[0010] Three-dimensional printing is used to create a dental restoration by ink-jet printing a binder into selected areas of sequentially deposited layers of powder. Each layer is created by spreading a thin layer of powder over the surface of a powder bed. Instructions for each layer may be derived directly from a CAD representation of the restoration. The area to be printed is obtained by computing the area of intersection between the desired plane and the CAD representation of the object. All the layers required for an aesthetically sound restoration can be deposited concurrently slice after slice and sintered / cured simultaneously. The amount of green body oversize is equivalent to the amount of shrinkage which occurs during sintering or curing. While the layers become hardened or at least partially hardened as each of the layers is laid down, once the desired final shaped configuration is achieved and the layering process is complete, in some applications it may be desirable that the form and its contents be heated or cured at a suitably selected temperature to further promote binding of the powder particles. The individual sliced segments or layers are joined by one or more binders to form the three dimensional structure. The unbound powder supports temporarily unconnected portions of the component as the structure is built but is removed after completion of printing.

Problems solved by technology

The fabrication of current all-ceramic dental restorations often requires extensive labor and time and the proficiency of highly skilled technicians.

Many state-of-the-art dental restorations reveal a sense of artistry that can typically only be achieved manually or “by hand.” While aesthetics are preserved with this process, microstructural inhomogeneities may appear, affecting strength and reliability.

Although pressable crowns reduce some of the skill time required, about two hours of concerted effort is necessary to complete a crown.

Pressed crowns may also suffer from similar strength and reliability problems typical of “hand made” crowns.

However, the necessary machining steps limit the choice of materials that can be used in dental restorations and sometimes compromise the strength and / or aesthetics of the finished restoration.

One of the current limitations of the CAD / CAM approach, which is not easy to overcome, is the fact that currently available systems at best produce copings that require veneering layers to provide a natural appearance.

Consequently, final processing of the crown is still in the hands of dental technicians which may limit the resulting structural reliability of the restoration.

The existing commercial CAD / CAM systems are unable to produce full crowns.

Some of the systems can machine inlays / onlays from a solid ceramic block and are not able to produce crowns or even copings.

This is an automation of steps that are otherwise performed by dental technicians and very well may not be practically advantageous.

One of the key limitations intrinsic to CAM methods is the fact that machining is not competitive technology for mass production of parts and components of any kind including dental restorations, e.g. dentures and crowns.

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