Shade Selection Procedures PDF

Shade selection by Dr. Ahmed Ismail Taha BDS, MSc and Phd of Fixed Prosthodontics. Lecturer at Faculty of Oral and Dental Medicine. Kafr El sheikh University.  Methods of Shade Selection I) Visual shade II) Digital shade selection...

Shade selection by Dr. Ahmed Ismail Taha BDS, MSc and Phd of Fixed Prosthodontics. Lecturer at Faculty of Oral and Dental Medicine. Kafr El sheikh University.  Methods of Shade Selection I) Visual shade II) Digital shade selection.(subjective) matching. I)Visual shade selection: (subjective) Preparatory steps: 1)Establishing a proper color environment: a) Proper correct source of light. -Initial selection is made at the chair then the patient is taken to a window & the color reconfirmed in natural daylight & under incandescent & fluorescent lighting…..why? -- Dental unit lamp should have color temperature of 5500 K which is equivalent to the temperature of natural day light b) Acceptable chromatic environment - The clinic wall should be light gray/blue which are the complementary color of yellow c) The amount of illumination - Dim light will interfere with the amount of light enter the retina less color perception - On the other hand too intense light will interfere with the differentiation of the surface texture - Therefore the proper amount of light intensity can be accurately measured by special colorimeter devices 2)Distraction exclusion: -Any distraction factors which disturb the eye from the intended focus of attention on the teeth should be eliminated e.g patient lipstick/moustache/gingival inflammation. 3)Cleanness of teeth surfaces: -The true color characteristics & the appearance of depth & translucency in a natural tooth cannot be correctly perceived unless the tooth is free of plaque & surface stains, so teeth should be scaled & stains. -Also avoid the dehydration of the teeth during shade selection as dry teeth are always show lighter value. 4)Patient position: -Patient should be seated upright. And Leveled to the observer's level. 5)Timing the shade selection: -Never postpone the shade selection to the end of the preparation appointment….why?? because eye is fatigued as a result of concentrated focusing during reduction of the abutment teeth, particularly if very bright fiber-optic illumination has been used. 6)Speed of selection: -The human eye fatigues very quickly to continuous color perception & becomes color blind. i.e the first choice is usually the best selection. N.B. The eye should also be rested by looking on a natural gray surface for some time so that balance happens to all color sensors of the retina by re- sensitizing the eye to the yellow shades of human teeth. 7)Close & distant viewing: -The close-up view is very treacherous & should be avoided. -30 cm is the ideal distance for shade selection. -The distant view increases the ability to discriminate values while relatively closer view increase ability to discriminate chroma. 8)Viewing angle: -Certain tooth or shade guides do change values due to glares. -Therefore, tooth should be viewed from different angle. 9)Shade guide: -Shade guide used should not only be made from the same material of the restoration but also from the same manufacturer. Shade selection procedure  Shade selection procedure The following procedures is designed to aid in the selection of the best shade specimen. 1) The matching process is started by quickly scanning the entire shade guide while holding it as close to the teeth as possible. 2) Short list by selection of few tabs that represent the closest match. 3) If the decision cannot be made between two tabs, hold them on either side of the tooth being matched & determine the more suitable. (choose the darker) 4) Try viewing the tabs through (squinting) half closed eye because it decreases the ability to discriminate color & increase the ability to match value. 5) Each prospective shade guide should be held next to the tooth being matched & aligned so that light reflects of the shade guide specimen in a manner similar to that of the natural teeth. 6) Matching is better to start with value & chroma then hue. Shade Distribution Chart or Images. The profile of the tooth to be replaced is drawn on a sheet of paper & the profile is divided into thirds by two vertical & two horizontal lines. It is easy from the sketch to communicate it accurately to the dental technician "ceramist" to mimic or transfer it to the ceramic restoration.  Visual shade guide The vita lumen Ivoclar Vitapan 3D classical Chromascope Master. shade guide. shade guide.  It is composed of four hues: A B C D 1. The vita lumen Each hue composed of different Chroma classical shade guide ex. Hue A composed of (A1, A2, A3, A3.5 and A4) 1. Choose the tab with the nearest hue, then select the appropriate match of chroma & value from the tabs available. A,B, C or ,D. 2. Chrome selection is next from within the same hue group e.g. select 1,2,3 or 4 from each hue group A,B,C,D. 3.Value is determined with a second shade guide whose samples are arranged in order of increasing lightness. (B1, A1, A2, D2, B2, C1, C2, D4, D3, A3, B3, A3,5, B4, C3, A4, C4) Shade matching with the use of the VITA classical (Lumin Vacuum) shade guide. (A) Selecting hue by matching samples with high chroma (e.g., A4, B4, C4, or D3) to a tooth with high chroma (i.e., canine). (B) Selecting chroma from within the hue group (e.g., B1, B2, B3, or B4). (C) Value- ordered shade guide is used to check lightness. 2. Ivoclar Chromascope shade guide 3. VITA Tooth guide 3D-MASTER (VITA North America) The concept of this system is based on the three-dimensional systematic & logical organization of tooth colors which allows for accurate shade selection. It incorporates the three colorimetric dimensions of color. Value = Lightness level. Chroma = Color saturation. Hue = Color distinction. The procedure is composed of three simplified steps in logical progression: Step 1 The value (lightness) is determined. Select the value level from the five value groups (levels 1-5) that is closet to the value of the tooth to be compared. Pull out the medium shade sample (M) from the selected value group. Step 2 The chroma (levels 1,2,3) is determined. Select the color sample of the selected M group that is closest to the tooth to be compared. Step 3 The hue (L,M,R) is determined. Check whether the natural tooth displays a more yellowish (L) or more reddish shade (R) than the color sample of the M-group that has been selected in the second step. Advantages: 1-Highest precision of shade matching. 2-User-friendly & simpler as never before. 3-Systemic & logical in three steps. 4-Reliability for the three parties concerned: dentist, patient & technician. 5- Reduced error potential. 6- All the shade tabs lies in the teeth color space shades. 7-Time-saving. 8-Immediate shades determined accurately. 9-Easy Communication with the lab.  Custom shade guide Certain teeth may be impossible to match commercial shade samples. The extensive use of surface staining has sever drawbacks; as it increase surface reflection and prevent light from being transmitted through porcelain. One approach to this problem is to extend the concept of commercial shade guide by making custom shade guide. Infinite number of shade samples can be made using combination of porcelain powders in varying distribution. But it is time consuming and is confined to specialty practice. Dentin shade guide It is used to communicate the color of the prepared tooth to the technician when translucent ceramic system are used e.g IPS EMPRESS Limitations of visual shade guides ▲ Retinal fatigue ▲ Background effects ▲ Color blindness ▲ Age of the receiver II)Digital shade matching Recently digital shade matching can be done by using computerized color measuring devices They can be classified according to the area of measuring whether : 1) Spot measuring devices: It measure the color only in 3mm2 area 2) Complete tooth surface measuring devices The Rayplicker Quickshade They can be classified according to technology of color measuring into: 1) Colorimeters. 2) Spectrophotometers. 3) spectroradiometers. 4) Digital cameras. Color Science -color measuring instruments- in Dentistry 1- Colorimeters e.g., *ShadeEye NCC Chroma Meter (Minolta – Shofu) Affected by the scattering characteristics of the material (edge loss) Color Science 2- Spectrophotometers -color measuring instruments- e.g., Vita Easyshade (Vident) in Dentistry Color Science -color measuring instruments- in Dentistry 3- Digital imaging and shade analyzers e.g., shadeVision (X-Rite) Digital color imaging + colorimetric assessment Color Science -color measuring instruments- in Dentistry 4- Hybrid instruments e.g., Spectroshade (MHT Optec) Color Science -color measuring instruments- in Dentistry e.g., ClearMatch system (Smart T tech)