‘When Your Teeth looks Unaesthetic; It Will Give You Reason to Visit Dental Hospital’

SHADE SELECTION

Shade selection and determination to match the patient’s dentition is one of the most challenging task of cosmetic dentistry. As general practitioners, we frequently face the problem of an unmatched and lifeless ceramic restorations and these mistakes are often attributed to the failure of the technician to produce life-like restorations  and roles of the operator also has significant roles.

Certain things should be taken into consideration during shade selection..

Vision

The retina is light sensitive portion of eye containing both the rods and cones  that contain chemicals like rhodopsin and iodopsin respectively which decompose and expose to light and in process it excites rods (dim light vision) and cones (color vision) .

1. Color

Color is property of a surface or a substance due to absorption of certain light rays and reflection of others within the range of wavelength (380nm to 750 nm; violet dark red) adequate to excite the retinal receptors.

Quantitatively, color has to be determined by three dimensional quantity specified by the three variables;

Hue, chroma and value

• Hue

It is a basic color of an object, may be primary  or combination of color ,such as red ,green and yellow.

• Chroma

It is a degree of saturation, intensity or strength of a hue like red, Pink may be of same hue but red has high chroma and Pink has a low chroma.

1. Metamerism: it is a phenomenon in which objects that appear to be color-matched under one type of light may appeared different when illuminated by a different light source. So, shade should be matched under more than one type of light to overcome the problem of metamerism.

Shade should be selected under standardized light condition.

The illumination should be (1000-2000)laxes. The ideal temperature is 5000+1000/-750k. The light should shine on the patient’s teeth approximately at an angle 45 degree lateral. If there is no standarized illumination in the dental clinic in day light.

iii.      Value:-

it is an amount of lightness or darkness in a hue. Color is dependent on four factors:

1. The observer
2. The object
3. The light source
4. The surrounding or environment

Each of four is equally important and when anyone of them is altered perception of color changes.

Shade Selection Sequences:

1. Aids: The shade guide is used by the clinician and the porcelain used by the technician should be from the same manufacturers so that there will be no problem occurring in procedures for proper color matching.
2. Time: Shade selection should be done prior to tooth preparation.
3. Light source: It can have definite effect on the perception of a color. There are basically three light sources commonly found in the dental office.

They are as follow;

• Natural light: it is extremely variable with time .There is an uneven distribution in morning and evening.
• Artificial light: It lacks equal distribution of a color.
• Incandescent light: it is produced by heat. Predominately red, yellow and blue.so, it tends to make red yellow stronger than blues weaker.
• Fluorescent light: It is high in blue-green energy and low in red.so blue is stronger and red is weaker. For example; Ceramic crowns or composite restorations that lacks fluorescening agent appears like missing teeth when viewed with a black light .

Preparation of patient :

• The patients should remove cosmetic (lipstick) and other distraction like earrings before shade matching is performed.

• Use natural gray drape for the patients.
• Teeth should be cleaned before an attempt of shade mas
• Stand between the patient and the light source.
• The viewing distance should be an arm’s length (50 -70) centimeters between the mouth of the patient and the eyes of the operator.
• selection, a color fatigue occurs .

Process for vita classic shade system:

• Matching process is began by quickly scanning the shade system.
• A general assessment of the hue is by passing the shade guide along the teeth and looking at the middle third for the body color. This determines the color group (A,B,C,D), Red brown, red yellow, gray and red gray respectively in decreasing order of values; lighest to darkest  :B₁,A₁,B_2,D_2,A_2,C₁,C_2,D₄,A_3,D₃,B₃,A3.5,B_4,C_3,A₄,C
• The intensity of chroma is then recorded for the body of the tooth from the selected group of colors (1,2,3,4 for vita ).
• Tabs are held either side of tooth when making a choice between two closely matching shade tabs.
• 0riginal portion of the shade tabs is matched with the gingival portion of the tooth.
• The incisal end of the tab is compared with area of the natural teeth.
• If a shade falls between two tabs then we should always select tab with low chroma.
• It is easier to change the chroma and value of restoration than the hue, so it’s more important to choose the right hue during shade selection.
• Make a shift selection, always accept your first decision.

There is also 3D shade selection = vita pan 3D master; in which we first select values rather than hue {five value groups -(1,2,3,4,5) which his closest to the tooth to be compared}.

References:

• Phillip’s book of dental materials .13^th
• Textbook of physiology; Guyton &Hall .
• Shade selection : problem & solution -Alvin vector Penster , April 1968 compendium

With due respect and lots of love, I would like to show my immense gratitude to all of my respected teachers especially respected Sir, Professor of Prosthodontics, Dr. Binod Acharya, he was head of department of Prosthodontics at Nepal Medical college,  Attarkhel and currently living in United Kingdom (U.K) and respected ma’am ,Assistant  professor of Conservative and Endodontics ; Dr. Rojin Joshi, she is working  in department of her respected field at Nepal medical college , Attarkhel , both of them have been guiding and loving me since the undergraduate period of my life and always give space to improve myself everyday authentically and little details of my professional works , skills and personal growth of  my life .