US 4,654,794 A · Methods for determining the proper coloring for a tooth replica

Abstract

Polychromatic light is directed at the surface of a live tooth and color data of light reflected therefrom is recorded, multiplied by the stored power distribution of a first standard illuminant and converted to three tristimulus values. Such values are compared with color values of a first group of stored color dental shades, and if a match occurs within a given tolerance, an indication of the nature of the recipe is produced. A second level search may be carried out against a substantially larger group of stored dental shades in the event of a no-match condition resulting from the first search. Excellent lifelike reproduction of the patient's tooth is enhanced by checking for least metamerism by operating upon the measured data with other illumination standards and selecting the best match under all lighting conditions. Additionally, a translucency factor is calculated, and employed to reduce the opacity of the inner opaque layer of the recipe which would otherwise be indicated should the patient's tooth not have a high degree of translucency. The calculation of a fluorescence factor also enhances excellent reproduction of the live tooth, and is employed to indicate the addition of a fluorescent ingredient to the final recipe.

Claims21

Dependent claims

A method of determining shade values for a recipe used to fabricate a color matched replica of a live tooth being examined in the mouth of a patient, comprising the steps of:

(a) directing polychromatic light at the surface of said live tooth;
(b) recording dental color data of light reflected from said live tooth consisting of a plurality of values indicative of the power distribution of wavelengths of light reflected from said tooth within each of a plurality of frequency bands in response to the execution of step (a);
(c) operating upon the color data produced in accordance with step (b) with the power distribution values of a given standard illuminant to produce modified color data;
(d) converting the modified color data produced in accordance with Step (c) to three tristimulus values by multiplying said modified color data with three standard color data templates;
(e) comparing said three tristimulus values with color values of a group of stored main color dental shades in accordance with a first level search;
(f) establishing an acceptance color difference tolerance value;
and
(g) identifying stored main color shades which are close enough to the shade represented by said three tristimulus values to satisfy said tolerance value.

5 more elements

A method of determining shade values for a recipe used to fabricate a color matched replica of a live tooth being examined in the mouth of a patient, comprising the steps of:

(a) applying polychromatic light to the surface of a color calibration chip;
(b) recording color signature data consisting of a plurality of values indicative of the power distribution of wavelengths of light reflected from said chip within each of a plurality of frequency bands in response to reflection of light from said calibration chip in accordance with executing step (a);
(c) enabling the normalization of subsequent dental color data measurements by applying a correction factor thereto produced by subtracting data recorded in accordance with step (b) from a stored set of data representing the calibration of the stored dental color data base;
(d) directing polychromatic light at the surface of said live tooth;
(e) recording dental color data of light reflected from said live tooth in response to the execution of Step (d);
(f) normalizing dental color data recorded in accordance with Step (e) by applying said correction factor thereto, said correction factor produced in accordance with Step (c);
(g) operating upon the color data produced in accordance with Step (f) with the power distribution values of a given standard illuminant to produce modified color data;
(h) converting the modified color data produced in accordance with Step (g) to three tristimulus values by multiplying said modified color data with three standard color data templates;
(i) comparing said three tristimulus values with color values of a group of stored main color dental shades in accordance with a first level search;
(j) establishing an acceptable color difference tolerance value;
and
(k) identifying stored main color shades which are close enough to the shade represented by said three tristimulus values to satisfy said tolerance value.

9 more elements

A method of determining shade values for a recipe used to fabricate a color matched replica of a live tooth being examined in the mouth of a patient, comprising the steps of:

(a) directing polychromatic light to the surface of a color calibration chip;
(b) recording color signature data consisting of a plurality of values indicative of the power distribution of wavelengths of light reflected from said chip within each of a plurality of frequency bands in response to reflection of light from said calibration chip in accordance with Step (a);
(c) enabling the normalization of subsequent dental color data measurements by applying a correction factor thereto produced by subtracting data recorded in accordance with Step (b) from a stored set of data representing the calibration of the stored dental color data base;
(d) directing polychromatic light at the surface of said live tooth;
(e) recording dental color data of light reflected from said live tooth in response to the execution of step (d);
(f) normalizing dental color data recorded in accordance with step (e) by applying said correction factor thereto, said correction factor produced in accordance with step (c);
(g) operating upon the color data produced in accordance with Step (f) with the power distribution values of a given standard illuminant to produce modified color data;
(h) converting the modified color data produced in accordance with step (g) to three tristimulus values by multiplying said modified color data with three standard color data templates;
(i) comparing said three tristimulus values with color values of a group of stored main color dental shades;
(j) establishing an acceptable color difference tolerance value;
(k) identifying stored main color shades which are close enough to the shade represented by said three tristimulus values to satisfy said tolerance value;
(l) illuminating said tooth with a dark background behind said tooth;
(m) recording the reflected dark background color resulting from the preceding step;
(n) subtracting said dark backgound color data from data recorded in accordance with Step (e) to produce translucency factor assignable to search;
(o) employing said translucency factor to reduce the opacity factor data component of a matched recipe should said translucency factor exceed a predetermined value;
(p) illuminating said tooth with light having a substantial ultraviolet component;
(q) deriving a flourescence factor by comparing the color data produced in accordance with step (p) with data produced by illuminating said tooth with light not including said substantial ultraviolet component;
and
(r) producing data indicative of the amount of a given fluorescent ingredient to be added to the recipe proportional to said fluorescence factor.

16 more elements

Dependencies are inferred from the claim text.

Methods for determining the proper coloring for a tooth replica

Life of this patent

Methods for determining the proper coloring for a tooth replica

Life of this patent

Abstract

Claims21