Clinical Science Kahng

Material Selection and Shade Matching for a Single Central Incisor

Introduction With regard to esthetics, the single central incisor poses the greatest re- by storative challenge for the clinician; not surprisingly, it can also be the most Luke S. Kahng, C.D.T. difficult tooth for the dental technician to match. Selecting the shade of the restoration depends in part on the material used for the understructure, and Mr. Kahng is the founder and owner of there is a wide assortment available from which to choose. The following are Capital Dental Technology Laboratory, among the most common: Inc., in Naperville, Illinois. The labora- tory specializes in all fixed restorations and its LSK 121 division provides per- An experienced technician can mask the underlying dark tooth color using sonalized custom cosmetic work. A porcelains with detailed color-masking techniques. strong proponent of collaborative den- tistry, Mr. Kahng stresses education, communication, and a team approach to patient care. A member of the AACD, Understructure Material his training has included extensive study with Russell DeVreugd, C.D.T., Dr. • Zirconia (e.g., Procera® [Nobel Biocare; Yorba Linda, CA], Lava™ [3M Frank Spear, Dr. Peter Dawson, and ESPE, St. Paul, MN], Cercon® [Dentsply Int., York, PA], Everest™ [KaVo others. America Corp.; Lake Zurich, IL], In-Ceram® [Vident; Brea, CA]) Mr. Kahng is the official clinician for --Flexural strength: approximately 1,200 MPa GC America, Bisco, and Captek. He is --Translucency: very low a frequent lecturer and program facili- tator for dentists and dental technicians, --Opacity: high and has published articles in Practical • Alumina core or glass-infiltrated alumina (e.g., Procera, In-Ceram) Procedures and Aesthetic Dentistry --Flexural strength: 450 to 700 MPa and Dental Dialogue. --Translucency: low --Opacity: moderate

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• Pressed Ceramics (leucite-re- Color of the Tooth Preparation are unlikely to replace PFM restora- inforced or lithium-disilicate If, after preparation, the underly- tions, they offer alternatives for pa- and apatite glass ceramics, e.g., ing tooth color has a dark shade (i.e., tients who demand a more natural- Empress® [Ivoclar Vivadent; between A5 and C10), the core of the looking restoration. It is the dental Amherst, NY], OPC® [Pentron; material chosen should be opacious technician’s responsibility to remain Wallingford, CT], Authentic® to mask the underlying dark color. educated about the latest materials [Jensen Industries; North However, an experienced technician and techniques; the proper function Haven, CT], GC Initial [GC can mask the underlying dark tooth of the occlusion; and the optimal America; Alsip, IL]) color using porcelains with detailed muscle position for esthetics, lon- --Flexural strength: 120 to 450 color-masking techniques. gevity, and comfort. MPa New materials are constantly be- ing introduced by manufacturers. --Translucency: high It is the dental technician’s However, it is unwise to use mate- --Opacity: low responsibility to remain educated rials until they have been used and about the latest materials and • Nonoxidizing metal (e.g., tested for a number of years. Before Captek™ [Captek; Altamonte techniques; the proper function of the occlusion; and the optimal using a new material for the first Springs, FL], Bio 2000® [Argen; muscle position for esthetics, time, the dental technician must ask San Diego, CA], Sinterkor™ longevity, and comfort. several questions, such as: How long [Pentron]) has the material been available? --Similar to porcelain-fused-to- What studies have been conducted metal (PFM) Design of the Preparation on the material? --Flexural strength: equal to porce- In addition to the material used Some metal-free restorations lain to metal for the understructure, the layer- require strict preparation --Translucency: low—equal to ing porcelain must be selected with techniques, such as a shoulder or porcelain to metal equal care. A porcelain system with a deep chamfer margin. Before internal colors will achieve maxi- --Opacity: high—equal to porce- selecting a material, the dental mum esthetics. Today’s specialized lain to metal technician must consider whether porcelains give the dental technician the tooth structure allows margins an advantage. Factors to Consider of 1.0 mm, whether the margins are subgingival or supragingival, and The choice of material depends so forth. Case Report to a large extent on factors unique A female patient disliked the ex- to each patient. No single material Patient”s Medical History isting crown on a maxillary central is ideal for every case; each will have The choice of material can be incisor, which had been cemented its advantages and drawbacks. For limited by allergies, a history of only three years previously. She re- example, the porcelain-to-oxidizing bruxism, etc. ported that she avoided smiling metal materials are susceptible to because of the crown’s unpleasant excessive opacity, which will result Durability of the Material appearance. The dentist who had in a lifeless-looking restoration and Regardless of how esthetic a res- placed the crown also had done a must be avoided. The feldspathic toration looks, it is not worth the composite build-up on the mesial porcelain materials (veneers and cost to the patient or the efforts of and incisal third of the lateral inci- jackets) of less than 0.8-mm thick- the dentist and dental technician if sor. When the crown was removed, ness tend to give a restoration exces- it lacks durability. it was determined that no modifica- sive translucency, which will result Each of these factors must be tion of the preparation was needed in a restoration that looks too gray considered in every case to achieve (Fig 1). Impressions were taken, and and dark.1 The following are some the best esthetic results. Metal-free the tooth was temporized (Fig 2). of the factors to consider when se- restorations are more similar to a Together, the dentist and the den- lecting materials: natural tooth than to an artificial tal technician conducted a custom crown. While metal-free restorations

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Figure 1: Preparation of the central incisor. Note Figure 2: Temporization of the central incisor. the slight discoloration at the incisal aspect of the preparation. Resin composite has been used to build up the mesial aspect of the lateral incisor.

Figure 3: Color mapping using a pressed ceramic Figure 4: After evaluation of the preparation, coping.2 adequate room for a pressed ceramic coping with layering porcelain technique. Shade A1 pellet with internal stain on the pressed coping. The gingival third has a gray effect and the middle third has a yellow-brown hue.

Figure 5: Sample colors of the translucent neutral, Figure 6: Sample colors after firing, made at 0.3- to enamel opal, enamel occlusal, cervical translucent, 0.4-mm thickness. These have been ground and glazed and clear fluorescence, fabricated by the technician. to simulate a final restoration.

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Figure 7: The sample color tabs are laid on top of Figure 8: Color tabs of the enamel shades. each other to assess the different color effects.

shade mapping; afterward, the den- achieve these effects, the dental tech- • The preparation design offered tal technician did a full color map- nician must make use of a porcelain sufficient room for the restora- ping (Fig 3) with the porcelain col- system with its own effect powders tion. ors that are available. and color-matching tabs and no- • The patient had no known aller- menclature. This can also be used gies, and her occlusion was not Shade Mapping and Photograpghy to match the surface characteristics a concern. Comprehensive shade mapping such as glaze, texture, and luster. • The patient was looking for a is a time-consuming process. No permanent type of restoration.3 single base shade can provide an adequate esthetic match. Different If light should reflect off the crown Based on all of these factors, in a different manner from the shades are needed in the gingival, pressed ceramics with layering por- neighboring teeth, it will betray body, and incisal thirds of the tooth, celain was the material selected for the fact that it is an artificial the restoration in this case. which also must be divided accord- restoration even if the shade is ing to its mesial and distal charac- perfect. Pressed Ceramics With Layering terizations. Standard shade tabs Porcelain can serve as a base shade and offer For the pressed ceramics, a variety a place to start; however, because If the dental technician cannot of different manufacturers’ ingots of the popularity of bleaching, es- meet the patient in person, photog- were selected for a wide assortment tablishing a base shade in itself can raphy must be used to supplement of colors, including dentin, bleached be difficult. Moreover, because the and enhance communication with (A0, A00, B0, B00 with 75% opac- thickness of the shade tabs does not the dentist. Reference photography ity), and veneer shades; occlusal match that of the finished restora- with shade tabs is a highly effective enamel light and milky; translu- tion, some color differences must means of communication. Digital cent ingots; and opaque ingots. The be anticipated when using these, as photographs show excellent detail opaque ingots (with 85% opacity) well. with regard to colors, glaze, texture, are valuable for masking discolored Unfortunately, shade guides are and luster. preparations. With pressed ceramics, not representative of the value of Master casts were fabricated. In too much translucency can occur, so real teeth, which is another reason addition to the master casts, the fol- a variety of choices are needed. The why relying on shade tab assess- lowing information was provided: opacity level of the ingots ranges ment alone can be problematic. • The preparation revealed slight from about 30% to 85%. Special shade tabs are also needed discoloration at the incisal Once the choice of material was for the opalescence, fluorescence, aspect. made, the central incisor was waxed and translucency of natural teeth. To to full contour on the cast and cut

Volume 22 • Number 1 Spring 2006 • The Journal of Cosmetic Dentistry 83 Clinical Science Kahng

Figure 9: Inside powder (IN 44–shade) is applied, Figure 10: Enamel intensive and cervical translucent followed by dentin A1 over the gingival to powders are layered in a transition of color to achieve middle third. a mammelon effect. Enamel occlusal is applied to the mesial to match the composite build-up on the lateral incisor. Enamel effect is applied to the distal aspect, giving it an enamel effect.

Figure 11: Translucent neutral covers the incisal to Figure 12: The texture and the amount of middle third to provide translucency with neutral translucency together result in a varying degree of color, allowing the underlying colors to show through. light reflection (sample fabricated by Luke S. Kahng, C.D.T.).

Figure 13: Surface texture characteristics coincide Figure 14: Crown is modified to give same texture of with those of the lateral incisor. the adjacent anterior. Surface texture checked with a silver powder marker on the surface of the centrals.

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Figure 15: Pressed ceramic coping with multilayered Figure 16: View after insertion; color matching and porcelain build-up. surface texture followed (central incisor crown).

back for the porcelain layering. The assess light transmission colors clear fluorescence powder; they can wax-up was then sprued, invested, (Fig 7). These samples allow the den- be used individually or mixed with and prepared to press. After the ce- tal technician to mimic the shadow the neutral or opal translucent. ramic has been pressed, care must zones, or areas of the restoration Enamel effect powders were used be taken to avoid overheating it (Fig 8) that will lose both chroma at the incisal area to give the natural when cutting off the sprues or modi- and brilliance. appearance that cannot be achieved fying the framework. When the cut- Inside powders and a specially de- with just one enamel shade and an back framework was ready for por- veloped, highly fluorescent primary application of translucent, the neu- celain application, the thickness was dentin, which gives the color depth tral color (Fig 11). Then the enamel evaluated to determine the amount effect, were used for the first layer powder was applied to achieve full of room available for layering por- of porcelain (Fig 9). Dentin porce- color saturation. Dentin enamel in- celain. If necessary, the shade of the lain was applied over the gingival cisal and occlusal build-up was ap- framework can be modified with and middle thirds to give the crown plied to the lingual of the crown. To internal stains (Fig 4), which can optimal chroma (i.e., saturation or complete the build-up at the contact be applied either on the pressed ce- strength of hue). The color is pro- areas, the crown was removed from ramic coping material or internally duced by reflection from the dentin. the cast. Then it was ready for bak- on the porcelain build-up, as well as The dentin porcelain was cut back to ing and firing. externally. provide room for a mammelon ef- The thickness of the porcelain fect. Enamel and enamel opal por- Surface Texture system color-matching tabs also can celain were applied to provide shade Matching the surface texture is be a problem. Sample colors of the graduation similar to that of natural just as important as matching the translucent neutral, enamel opal, incisal areas as well as translucency. shade (Fig 12). Indeed, surface tex- enamel occlusal, cervical translu- The enamel powder has a high level ture is one of the most important cent, and clear fluorescence were of opalescence in conjunction with elements of an esthetic restora- fabricated in thicknesses of 0.3 to high translucency to create an un- tion. The surface texture of an ante- 0.4 mm (Figs 5 & 6), then ground derlying background to the mam- rior tooth is on prominent display and glazed to represent a final res- melon effect (Fig 10).4 (Fig 13). For this reason, it will ap- pear heavier than the neighboring toration. The thickness of these fired A thin layer of clear fluorescence teeth. If light should reflect off the porcelain discs is important; discs powder was applied between the crown in a different manner from 0.2 mm or less will be too clear, dentin and enamels. This so-called the neighboring teeth, it will betray while those at 0.6 mm will be too sclerose dentin brings true-to-nature the fact that it is an artificial resto- thick. The translucent colors should depth into the tooth color. Translu- ration even if the shade is perfect. be placed on top of each other to cent modifiers were applied over the

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Figure 17: Lateral view to evaluate the segmentation Figure 18: Smile view showing the harmony and color of the color saturation. saturation of the central incisors.

Surface texture can affect brightness, the communication between dentist color saturation, luster, and so forth and dental technician and the den- (Fig 14). A natural tooth does not tal technician’s knowledge and tal- present an absolutely smooth sur- ent are of paramount importance in face; it is generally a gently undu- achieving a natural-looking restora- lating surface, traversed by very fine tion and a successful esthetic result. horizontal grooves. The horizontal Acknowledgement parallel ridges, or growth lines, and the small vertical ridges that run par- Case courtesy of Rick Alwan, allel to the marginal ridges help it to D.D.S., Naperville, Illinois. blend into the oral environment. References Porcelain color build-up reveals a technician’s technical ability, but the 1. Chu S, Ahmad I, Devigus A. Fundmentals of Color (chapter 3). Chicago: Quintes- surface texture reveals a technician’s sence; 2004. 5,6 esthetic touch (Fig 15). 2. Sulikowski SV, Yoshida A. Surface texture: The completed crown was A systematic approach for accurate and ef- fective communication. Quint Dent Tech placed on the prepared tooth 26:10-19, 2003. (Figs 16 & 17). The patient was very 3. Kataoka S. Nature’s Morphology (chapters pleased with the results and no longer 4 and 5). Chicago: Quintessence; 1998. found it necessary to hide her smile 4. Kois J. New paradigms for anterior tooth (Fig 18). preparation: Rationale and technique. Oral Health 88:19-30, 1998. 5. Sorensen JA, Torres TJ. Improved color Conclusion matching of metal ceramic restorations. Part 2. In: Magne P and Belser V. Bonded In terms of shade matching, the Porcelain Anterior Restorations: A Bio- single central incisor can be the mimetic Approach (pp. 83-83). Chicago: most difficult tooth for a dental Quintessence; 2002. technician to fabricate. The selection 6. Spear FM. Maintenance of the interdental papilla following anterior tooth removal. of the material for the framework is Pract Periodont Aesthet Dent 11:21-28, only the first step in this process. 1999. Several factors must be considered, ______including the design of the restora- v tion, the patient’s medical history, and the durability of the material. Once the correct material is selected,

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