In the field of Restorative Dentistry significant advances have been made in recent years, particularly in the area of porcelain to metal restorations. The dental ceramist, with the modern dental porcelains and wide range of metal alloys may now create a porcelain to metal restoration that effectively duplicates appearance, color and vitality of the surrounding natural dentition.
However, one aspect of creating this porcelain to metal restoration has not enjoyed significant advances or changes since its inception. That aspect is the composite proper interpretation of the natural tooth color to be duplicated, that correct color being simultaneously communicated accurately to the dental ceramist. It is the norm rather than the exception that the color is misinterpreted by the dentist, the reason being that he does not have at his disposal a wide and varied selection of colors from which to select.
In practice, the standard shade selection guide used by most dentists consists of a kit comprising sixteen shade tabs, each with a handle. Respective shade tabs being defined as a piece of porcelain or plastic, formed to the shape of an anterior tooth. Each such tab presents one numbered color image.
Currently, these sixteen tabs have been divided into four basic color groups. The groups are: reddish-brown, five tabs; reddish-yellow four tabs; grey four tabs and reddish-grey three tabs.
The practitioner dentist would select one of the tabs and place it for comparison next to the patient's natural tooth. A careful side-by-side observation would dictate whether this tab closely simulates the color of the natural tooth. If the tab does not match, then this same trial and error procedure would be repeated with numerous other tabs. After the best color match had been selected, then the number and letter denoting the selected tab was communicated to the dental ceramist. The ceramist would then rely upon that letter and number code to select the correct porcelain powders to be used for construction of the restoration itself, that would match that particular color.
In natural dentition there are many more colors and combinations of colors that appear then in this standard shade guide. One may observe that from this very limited number of colors to choose from, it would be very difficult to properly select a given color that would match reasonably close to the natural dentition; yet each day a multitude of dentists attempt to select correct tooth color by using this very limited color selecting resource. This can be and very often is a frustrating experience for the dentist and dental ceramist. This very experience of proper selection of natural tooth color and accurate communication of this selection to the dental ceramist is what is addressed by the present invention, defined as Custom Pre-formed Shade Selection System, hereinafter CPSSS.
Among the reasons why proper color selection is rendered so difficult with the system in use today, one must be conversant with color terminology. Likewise, understanding the professional terms will allow us very easily to comprehend how the CPSSS addresses and resolves the difficulties discussed. These terms will be used interchangeably to define minor art difficulties and will also be used to describe the solutions.
COLOR TERMS: Named, defined with examples.
(A) Hue: The name that identifies the color; for example red, green, yellow blue, etc. Hue may also be a combination of colors, for example: reddish-yellow, reddish-brown, etc.
(B) Chroma: The strength, intensity or saturation of the hue. For example, an avocado is deep green, displaying a high chroma. On the other hand a green apple is light green, displaying a low chroma.
(C) Value: The brightness of any color measured and understood to be in the range of white to black. Any point in between white and black will naturally comprise a certain intensity of grey. For example, one part white paint mixed with three parts black paint would yield dark grey paint. Dark grey constitutes a low value; on the other hand, one part black paint mixed with three parts white paint would result in a light grey paint, constituting a high value.
(D) Translucency: The range from transparent to opaque. For example, a glass of water is transparent; a glass of milk is opaque and a glass of water with two drops of milk stirred is translucent.
The above four terms define the color components found individually in varying degrees and cooperatively in varying ratios in every tooth color. Whereas an elementary understanding of these terms is somewhat easy, nonetheless a proper interpretation and accurate communication of the varying degrees and ratios is much more difficult. For example, each time the color is selected by the dentist he/she must select the proper hue--reddish-brown, reddish-yellow, etc. Then the chroma must be determined, that being the intensity of the hue. Next, one must determine the value of the color, which is the brightness or the amount of grey present in the color. Last, one must describe how translucent the tooth is.