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Shade selection for FPD
This document discusses shade selection and communication between dentists and dental laboratories. It begins with an introduction to color science concepts like hue, value, chroma, and color mixing systems. It then describes common shade guides like Vita Classic and Vita 3D-Master and how to use them. Electronic shade matching devices and shade distribution charts are also introduced. Principles of shade selection and factors affecting color perception are outlined. The responsibilities of dentists and laboratories are defined, including the importance of clear communication of shade and details in work authorizations. Custom shade matching techniques using resin kits are presented to improve color matching between clinicians and technicians.
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Shade selection for FPD
- 1. Shade Selection &Lab Instruction in FPD DEPT.OF PROSTHODONTICS & CROWN & BRIDGE North Bengal Dental College & Hospital
- 2. Introduction To provide aestheticrestorations to the patients,the dentist must understand the scientific as well as artistic basis of shade selection.To accomplish this,a through knowledge of the concepts of colour & light is necessary with clear communication to the laboratory. Colour: An attribute of things that results from the light they reflect,transmit or emit in so far as this light causes a visual sensation that depends on its wavelegth. Light: Light is a form of visible energy that is part of the radiant energy spectrum.Visible light spectrum ranges from 400-700 nm. Colour mixing: In the additive or light-mixture colour mixing system;red,green,blue are the primary colours.Mixing two primary colours produces a secondary colour. Red+green=yellow ; Green+blue=cyan ; Red+blue=magenta This system applies only to combining lights & illuminants.
- 3. In the subtractiveor pigment-mixture system,the secondary colours in the additive system yellow- cyan-magenta are the primary colours. Yellow+cyan=green ; Cyan+magenta=blue ; Magenta+yellow=red In dental ceramics both additive & subtractive concepts are used.
- 4. Colour description:Two systemsmay be used to describe colour: 1. Munsell (1915) colour order system-more visually descriptive:the system describes colour possessing three dimensions- i. Hue ii. Value iii. Chroma 2. Cielab (1976) colour system-more quantitative
- 6. Colour of humanteeth: Spectrophotometer studies shows a hue range of 6 YR to 9.3 Y,a value range of 4-8 & a chroma range from 0-6. Hence the human teeth lie in the yellow-red to yellow portion of colour wheel,with value range in the lighter portion,which indicates that very dark teeth are uncommon.The chroma range is towards the lower scale,which indicates that strong colours are not found. Colour perception:This involves the participation of three factors: 1. The observer 2. The object being observed 3. The light source Observer:Perception of colour depends on the observer’s visual individuality.It depends on the age,duration of the exposure of the eye,fatigue,colour blindness.
- 7. Object: When lightfalls on an object,it is absorbed,reflected,transmitted or refracted depending on the light transmitting ability of the object.This produces characteristic quality of that colour. Light source: The light source utilized has a definite effect on the perception of colour.There are commonly three available source-natural daylight,incandescent light & fluorescent light.LED lights are also being used currrently. Example: of commercially available colour corrected lights are-Demetron shade light & Vita-Lite. Metamerism:An object appears to be having different colours when viewed under different light source.
- 8. Principles of Shade Selection 1.Teeth to be matched must be clean 2. Remove bright colors from field of view - makeup / tinted eye glasses - bright gloves - neutral operatory walls 1. View patient at eye level 2. Evaluate shade under multiple light sources 3. Make shade comparisons at beginning of appointment 4. Shade comparisons should be made quickly to avoid eye fatigue
- 9. Shade Guides Shade matchingis performed either visually (using shade guide) or by electronic shade taking devices or by shade distribution chart. Visual : Most convenient and common method of making shade selections Guides consist of shade tabs ◦ Metal backing ◦ Opaque porcelain ◦ Neck, body, and incisal color Select tab with the most natural intraoral appearance
- 10. Commercial Shade Guides invisual method • Vita Classic • Vitapan 3D –Master • Extended Range Shade Guides
- 11. Vita Classic ShadeGuide • Very popular shade guide • Tabs of similar hue are clustered into letter groups – A (red-yellow) – B (yellow) – C (grey) – D (red-yellow-gray) • Chroma is designated with numerical values • A3 = hue of red-yellow, chroma of 3 A B C D
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- 13. Vita Classic ShadeGuide Manufacturer recommended sequence for shade matching 1. Hue Selection 2. Chroma Selection 3. Value Selection 4. Final Check / Revision
- 14. Vita Classic –Step 1 (Hue Selection) • Four categories representing hue – A, yellow-red – B, yellow – C, gray – D, red-yellow-gray • Operator should select hue closest to that of natural tooth • Use area of tooth highest in chroma for hue selection – Difficult to select hue for teeth low in chroma
- 15. Vita Classic –Step 2 (Chroma Selection) • Hue selection has been made (B) • Chroma is selected from gradations within the B tabs – B1, B2, B3, B4 • Several comparisons should be made – Avoid retinal fatigue – Rest eyes between comparisons (blue-gray)
- 16. Vita Classic –Step 3 (Value Selection) • Use of second, value ordered shade guide is recommended • Value oriented shade guide – B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4, • Value best determined by squinting with comparisons made at arms length – Decreases light – Diminishes cone sensitivity, increases rod sensitivity – Tooth fading first has a lower value
- 17. Vita Classic –Step 4 (Final Check / Revision) • Potential Problem – Following value selection, tabs selected for hue and chroma may not coincide with shade tab selected for value
- 18. Vita Classic –Step 4 (Final Check / Revision) • Possible Findings / Solutions – Value of shade tab < natural teeth • Select new shade tab with higher value • Cannot increase value of restoration with extrinsic staining • Will only increase opacity, light transmisison – Value of shade tab > natural teeth • Select new shade tab with lower value (or) • Bridge difference with intrinsic or extrinsic staining
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- 20. Vita-3D – Step1 • Determine the lightness level (value) • Hold shade guide to patient’s mouth • Start with darkest group moving right to left • Select Value group 1, 2, 3, 4, or 5
- 21. Vita-3D – Step2 • Select the chroma • From your selected Value group, remove the middle tab (M) and spread the samples out like a fan • Select one of the three shade samples to determine chroma
- 22. Vita-3D – Step3 • Determine the hue • Check whether the natural tooth is more yellowish or more reddish than the shade sample selected
- 23. Vita-3D – Step4 • For more precise shade, intermediate levels for hue, value, and chroma can be given – 2.5M2 = value between 2M2 and 3m2 – 3M1.5 = chroma between 3M1 and 3M2 – 3M2 / 3L2.5 = hue between 3M2 and 3L2.5
- 24. Vita-3D – Value Modification •For more precise shade, intermediate levels for value, chroma, and hue can be given – 2.5M2 = value between 2M2 and 3M2
- 25. Vita-3D – Chroma Modification •For more precise shade, intermediate levels for value, chroma and hue can be given – 3M1.5 = chroma between 3M1 and 3M2
- 26. Vita-3D – Hue Modification •For more precise shade, intermediate levels for value, chroma and hue can be given – 3M2 / 3L2.5 = hue between 3M2 and 3L2.5
- 27. Extended Range Shade Guides •Most shade guides do not cover all the colors in the natural dentition • Some porcelain systems extend the typical range • Bleached shades • Dentin shades • Custom shade guides
- 28. Electronic shade takingdevices These are electronic instruments which record the colour of the tooth.They allow an improved understanding of colour perception & its correlationwith clinical aspects. They are divided into two categories: 1.Colourimeters: It measures the absorbance of different wavelengths of light in a solution,e.g.Shade eye-Shofu 2.Spectrophotometers:It quantitatively measures the reflection or transmission properties of a material as a function of wavelength,e.g.Easy shade-Vita.
- 29. Shade distribution chart Thetooth is divided into incisal,middle & cervical portions & the colour of each region is matched independently. Various patterns of translucency must be recognized to attain good results.In younger patients the incisal enamel is thick & very translucent.As translucency increases the value decreases.Over years of function,this enamel is lost.Similarly the thickness of the enamel on the buccal aspect also decreases & allows the dentine to dominate the shade. Individual characteristic are then marked.The surface of the tooth or the restoration determines how much of light is reflected away.This produces changes in the perceived colour of restoration.Younger teeth show a great deal of surface characterization like stippling,developmental lobes,ridges & striations.Older teeth,due to wear show a smoother,highly polished surface. .
- 30. Lab instructions To makea high-quality fixed prosthesis, all members of the dental team must understand what they can reasonably expect from each other. A mutual knowledge of individual limitations is also critical.The dentist who does not understand and appreciate the challenges faced by the technician is at a serious disadvantage when prescribing and delegating laboratory procedures . Critical to the development of sound clinical judgment is a thorough understanding of technical procedures and their rationale. MUTUAL RESPONSIBILITIES Good communication is the key to a dental team's technical success. This requires a close working relationship between the dentist and laboratory technician.Anticipating satisfactory results is absolutely unrealistic if the dentist does not have a reasonable amount of experience with, and a thorough understanding of, dental laboratory procedures.
- 31. The American DentalAssociation (ADA) has issued guidelines to improve the relationship between dentist and technicians. The dentist, being duly licensed, should: (1) Provide the laboratory with signed written instructions detailing the work which is to be performed and prescribing the appropriate materials to be used; (2) Provide the laboratory with accurate impressions,casts, interocclusal records or mountings; (3) Identify the margins, postdam, borders, relief and/or prosthetic design on all submitted cases; (4) Furnish a shade description, photograph,drawing or shade button that most closely achieves the desired results; (5) Provide a verbal or written approval for thelaboratory to proceed with the fabrication of the prosthesis or approve modifications, if notified by the laboratory that a submitted case may have questionable areas or unclear instructions and submit written approval to the laboratory after the item in question has been clarified; (6) Retain a copy of the written instructions for aperiod of time as may be required by law; (7) Follow appropriate laboratory infection control protocol as outlined in the ADA's infection control guidelines.
- 32. The dental laboratoryshould: (1) Produce dental prostheses following the written instructions provided by the dentist and using the impressions, casts, interocclusal records or mountings as submitted; (2) Review the case with the prescribing dentist for clarification if a question arises; (3) Match the shade as described in the original instructions, within the limitations of the materials available for use; (4) Notify the dentist immediately if it is determined that work on the case cannot proceed; Section 3 Laboratory Procedures (5) Fabricate the prostheses in a timely manner; (6) Inform the dentist of the materials used in the fabrication of the case; (7) Follow appropriate laboratory infection control protocol as outlined in the ADA's infection control
- 33. RESPONSIBILITIES OF THEDENTIST The dentist has the overall responsibility for the treatment rendered. Delegating many procedures to auxiliary personnel is possible if all the necessary information is provided to enable them to deliver high-quality service. However, errors such as insufficient tooth reduction, uncertainty about the location of tooth preparation margins, improper interocclusal records and articulations, and ambiguity in communicating the desired shades for esthetic restorations to the technician hamper this responsibility WORK AUTHORIZATION In addition to certain general information that is required by law, a work authorization form (Fig. 16-8)should include the following: 1. General description of the restoration to be made 2. Material specification (e.g., ADA Type IV gold) 3. Desired occlusal scheme 4. Connector design for FPDs 5. Pontic design, including the material specification for tissue contact 6. Substructure design for metal-ceramic restorations 7. Information regarding the shade selection for esthetic restorations 8. Proposed RPD design (if applicable) 9. Date of the next scheduled patient appointment
- 34. Shade Selection: With theprevalence of metalceramic restorations, dentists and technicians have become acutely aware of the difficulty involved in communicating shade selection. A thorough understanding of the principles of color science and the use of internal and surface colorants is essential to both parties. Many dentists and technicians have found a diagram of the tooth that allows specifications of multiple shades helpful (Fig. 16-10). 11 The diagram should be large enough to designate a cervical shade, an incisal shade, and any applicable individual characterization. Diagrams on most preprinted laboratory prescription forms do not provide adequate space (see Fig. 16-8), so other space must be available. A separate entry regarding the value or brightness can be helpful. When selecting a shade, the dentist should use a guide that corresponds to the ceramic system used by the technician. On occasion, it may not be possible to obtain a match with a simple shade guide (e.g., the Vita Lumin vacuum system). In those cases an alternative guide or a shade distribution chart (outlined in Chapter 23) should be used. The dentist must have excellent color perception skills and should be able to precisely transfer those onto a written prescription that includes a large, detailed diagram that allows the ceramist to accurately reproduce the shade observed and described by the clinician. Close communication and cooperation are obviously necessary, and a trial porcelain firing may be needed.
- 35. A practical alternativeto written color communication is the use of light-cured, resin-based staining kits to custom-stain a shade-tab. The closest matching shade-tab is selected and modified using stains mixed with liquid resin. Once the desired match has been obtained, the resin is light-cured, and the cus- tomized tab is sent to the dental laboratory. The ceramist then has an actual reference and can compare the work and make the required modifications, thus ensuring predictable success. If esthetic requirements are extensive or difficult to communicate through the means described above, involving dental laboratory personnel in the shade selection process may be helpful. The ADA takes the position that when a dentist requests the assistance of a dental laboratory technician in the shade selection process, this does not constitute the practice of dentistry by the technician, provided the activity is undertaken in consultation with the dentist and that it complies with the dentist's written instructions. Such assistance is most appropriately provided
- 36. Fig. 16-10. Ashade distribution chart must be adequate in size to permit inclusion of enough detail. Subtle differences observed in cervical shades are identified, as are surface details such as hypocalcification, incisal translucency, and stains.
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- 38. Reference 1.Contemporary Fixed Prosthodontics- Rosensteil,Land,Fujimoto 2.Fundamental ofFPD – Shillingburg 3.Textbook of Prosthodontics-V Rangarajan,TV Padmanabhan 4.www.google.com
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Editor's Notes
- #9 General Principles – regardless of which system is used, the principles for shade selection do not change. 1. Teeth to be matched should be cleaned of all debris and stains. If necessary ad prophy should precede tooth shade selection. 2. Brightly color lipstick/makeup should be removed and bright clothing draped. Protective gloves of bright colors should be swapped out for a neutral color. The operatory walls should not be brightly painted. 3. Patient should be viewed at eye level, so the most sensitive part of the retina will be used. 4. Shade comparisons should be made under different lighting conditions. Initial shade may be taken under a color corrected fluorescent light and then reevaluated or confirmed in natural daylight. (taking patient to an operatory window). 5. Shade comparisons should be made at the beginning of a patient’s visit. Teeth increase in value, particularly if a rubber dam is used. (DESSICATION) 6. Shade comparisons should be made quickly (REMEMBER COLOR FATIGE), with shade tabs placed just under the lip and adjacent to the teeth to be matched. This ensures that the background of both the shade tab and the tooth to be matched are the same – essential to shade matching.
- #11 Commercial Shade Guides – The most convenient method for selecting shade is with a commercially available shade guide. Each shade tab has a metal backing coated with an opaque porcelain backing, color , neck color, body color and incisal color. Shade selection consists of selecting the tabs that looks most natural in the mouth. It is reproduced by using the techniques and materials recommended by the manufacturer to replicate the colors seen in the tab. Common shade guide are grouped into categories of the same hue (A, B, C, D). To increase the color possibilities In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D).
- #12 Common shade guide are grouped into categories of the same hue (A, B, C, D). To increase the color possibilities In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D).
- #15 Hue Selection – In the popular Vita Lumin shade guide there are four hue categories. A1,A2, A3. A3.5, A4 are similar in hue, while the B shade are similar in hue. The same holds true for the C and D tabs. An operator may chose the nearest hue and then go on to select the appropriate chroma. If the intensity of chroma is low, it will be more difficult to select the proper hue. If this is the case, on should use the region of the tooth with the most intense chroma to select hue.
- #16 Chroma Selection- Once hue is selected, chroma match is chosen. For example, if a B hue is selected as the best color variety, hue is selected from the four gradations within the B tabs: B1, B2, B3, and B4. Several comparison s are usually necessary to determine the most appropriate hue and corresponding chroma. Between comparisons, glancing and a light blue object will rest the operator’s eye and help avoid retinal fatigue. Hue consistency among shade guides has not been proven and remains on of the main difficulties in maintaining a consistent shade from the shade taking appointment to placement of the final restoration.
- #17 Value Selection – Final value is selected by using a second shade guide whose samples are arranged in order of increasing lightness. The dentist can then determine if the value of the tooth is within the shade guide’s range (HIT BLEACH SHADES) Attention is then focused on the range of the shade guide that best represents the value of the tooth that relates the hue and chroma. Value is most easily determined by observing the guide and teeth to be matched at a distance, standing slightly away from the chair and squinting. ( COLOR VISION IN THE DARK) Squinting reduces the amount of light that reaches the retina. Therefore stimulation of the cones is reduced while rods become more sensitive to the increasingly achromatic conditions. The dentist should concentrate on which disappears first - the tooth of the shade tab. The one the fades first has the lower value.
- #18 After value selection has been made it is more likely that the previously selected hue and chroma will not be found in the shade tab of the value selected. One must then consider whether to revise previously selected shade sample. (SHOW BLEACH SHADE GUIDES) If the value of the shade tab is lower (darker) than that of the natural teeth, a change is usually necessary (WHY?) Because increasing the value of a restoration is not possible by means of staining. An increase in opacity will result with inadequate end result for shade. If the value of the shade tab is higher than the natural teeth on must decide whether to decrease the value by selecting a new shade tab or if the difference can be bridged the addition of intrinsic (internal) or extrinsic (external) staining. (HOW LONG DOES EXTRINSIC STAINING LAST?) Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4,
- #19 After value selection has been made it is more likely that the previously selected hue and chroma will not be found in the shade tab of the value selected. One must then consider whether to revise previously selected shade sample. (SHOW BLEACH SHADE GUIDES) If the value of the shade tab is lower (darker) than that of the natural teeth, a change is usually necessary (WHY?) Because increasing the value of a restoration is not possible by means of staining. An increase in opacity will result with inadequate end result for shade. If the value of the shade tab is higher than the natural teeth on must decide whether to decrease the value by selecting a new shade tab or if the difference can be bridged the addition of intrinsic (internal) or extrinsic (external) staining. (HOW LONG DOES EXTRINSIC STAINING LAST?) Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4,
- #20 VITAPAN 3D-MASTER SHADE GUIDE Manufacturer claims this guide covers the entire tooth color space. Shade samples are grouped in 6 lightness levels, each of which has hue and chroma variations in evenly spaced steps of 4 CIELAB units of lightness. Dimension and 2 CIELAB units of hue and chroma.. Because the tabs are evenly spaces intermediate shades can bee predictably formulated by combining porcelain powders. Manufacturer recommends selection value, hue and chroma in that order. (MAY NEED TO ELABORATE)
- #21 In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D). Al shade samples belonging to one lightness level (1- 5) have the same value (see black and white photograph). Differences within one lightness level are only with regard to the chroma and hue. These are determined in stage 2 and 3. In step 1 we are only concerned with determining the correct value (lightness level), i.e. not a single shade sample tooth (1 out of 26), but a group of shades with the same value (1 out of 5). Al shade samples of an M-group feature the same hue and lightness. They only differ in the chroma. Tips for
- #27 Intermediate values should be noted on the laboratory communication form
- #28 Most shade guides cover a more limited range of colors than is found in the natural, and altered dentition. Some porcelain systems are available which extend this range. Using two shade guides is a practical way to extend the range of the traditional commercial shade guides. (EXAMPLE – BLEACH SHADES) Dentin Shade Guides (STUMP GUIDE) When using translucent all-ceramic system for a crown or veneer (FEDLSPATHIC PORCELAIN OR IPS EMPRESS), communicating the shade of the prepared dentin is very helpful to the laboratory. One system provides specifically colored die materials that match the dentin shade guide and enable the technician to better judge restoration esthetics. Custom Shade Guide Unfortunately, some teeth can be impossible to match to commercial shade guides. It can also be difficult to exactly match the final restoration with the shade tab. The extensive use of extrinsic surface staining has severe drawbacks, Stains increase surface reflections Prevent light from being transmitted through the porcelain One approach to this dilemma is to extend the concept of a commercial shade guide with the creation of a custom shade guide. An infinite number of samples can be made by using different combinations of porcelain powders in varying distributions. This is a very time consuming procedure and typically limited to specialty practices.