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Material Selection and Shade Matching for a Single Central Incisor

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Material Selection and Shade Matching for a Single Central Incisor 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 80 The Journal of Cosmetic Dentistry • Spring 2006 Volume 22 • Number 1 CLINICAL SCIENCE KAHNG • 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 Volume 22 • Number 1 Spring 2006 • The Journal of Cosmetic Dentistry 81 CLINICAL SCIENCE KAHNG 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. 82 The Journal of Cosmetic Dentistry • Spring 2006 Volume 22 • Number 1 CLINICAL SCIENCE KAHNG 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.
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