Anterior Esthetic Restorations Fabricated Using a Spectrophotometer
John D. Da Silva; Shigemi Nagai
Color matching a central incisor presents one of the most significant clinical challenges. Color matching is routinely performed using dental shade guides and is dependent on individual visual perception. Although a number of shade guide systems are available for clinical use, the color space of currently available dental shade guides is limited in that they do not represent the full spectrum of color found in natural teeth.1-5 There are problems associated with an individual’s perceptual ability. Color discrimination ability differs from individual to individual and visual color selection depends on several factors, such as the shape, size, position, surrounding illumination, and background color.6-8 Variation in any factor may result in an altered perception of color. A tooth is composed of stratiform semi-translucent layers of enamel and dentin that absorb, reflect, transmit, or refract part or all incident light, thereby producing the “quality” of the tooth’s color.9 Different light sources produce distinctive distributions of light energy that alter an observer’s perception of color. Different lighting conditions can impact color perception. Light sources may be a critical factor in visual color matching, considering the optical properties of the natural tooth. Digital photography has gained popularity as a method to convey color information to dental laboratories. However, the quality of these images is also influenced by lighting conditions that can undermine the integrity of the color acuity.10,11
Instruments such as spectrophotometers generally can provide more systematic and precise measurements because of their ability to measure the amount of light reflected from objects over a full spectral wavelength. Digital image capture also provides a visual image of a target tooth. This should theoretically improve communication with the dental laboratory for more precise color matching. These instruments have been developed to obtain the most accurate shade to improve patient satisfaction with the esthetics of a restoration, and to reduce the number of visits necessary to produce an acceptable result.
A new 2-dimensional spectrophotometer, Crystaleye® (Olympus, Shinjuku, Tokyo, Japan), was used to produce central incisor metal-ceramic crowns. This system has several potential advantages because it is handheld and can acquire the spectral image of the dentition. The supporting software provides sophisticated visual images and numerical data based on spectrophotometric measurements. In addition, digital pictures of the individual tooth, the prepared tooth, the arch, and the patient’s face can be acquired using the device.
CLINCAL CASE REPORT
Three patients in need of a single maxillary central incisor crown with an intact contralateral incisor are presented in this article. Each patient had a tooth prepared for a metal-ceramic crown with a 1.5-mm shoulder. Impressions were made with a polyether impression material (Impregum; 3M ESPE, St. Paul, MN) and a stock tray (Sani-Trays®, Waterpik, Ft. Collins, CO). Provisional crowns were fabricated (Alike; GC America, Alsip, IL) and luted with provisional luting cement (TempBond®; Kerr Corporation, Orange, CA) A metal-ceramic crown was fabricated using the tooth-color information from the spectrophoto-meter (Figure 1View Figure and Figure 2). This spectrophotometer uses seven light-emitting diodes as an illumination source with 45º/0º geometry. Before data acquisition, the instrument was calibrated using a calibration plate (Olympus).
Images of the maxillary arch and full face were captured with the spectrophotometer. The spectral data from the tooth was acquired by capturing an image of the tooth (Figure 3). The reflectance values from 400 to 700 nm with 1-nm intervals for each pixel were transferred from the spectrophotometer to a computer. The data was transferred to the dental laboratory, where it was analyzed for the best shade match and correlated to a shade guide in three regions—incisal, middle, and cervical—per tooth (Figure 4). The shade data for five shade-guide systems (VITAPAN Classical and VITAPAN 3D Master®, Vident, Brea, CA; Noritake Shade Guide, Noritake Co, Inc, Fair Lawn, NJ; Vintage Halo NCC, Shofu Dental Corporation, San Marcos, CA; and IPS Chromascope, Ivo-clar Vivadent, Inc, Amherst, NY) are incorporated into the software. Split images and inverted images can be shown for each tooth and any shade-guide tab. Color mapping for color coordinates—lightness, yellowness, and redness—can be displayed (Figure 5). In the dental laboratory, all of the software functions were used for the fabrication of individual crowns and the color of the fabricated crowns was measured and modified as necessary, before leaving the laboratory, as a quality check. The use of the spectrophotometer allowed the dental technician to reproduce the detailed color, form, and translucency found in the adjacent central incisor crowns. The restorations mimicked what was present in the contralateral central incisor, allowing for a highly acceptable esthetic result (Figure 6, Figure 7, Figure 8).
The use of the handheld spectrophotometer to capture tooth color data was quick, simple, and accurate. The data file generated was then transmitted to the laboratory and opened with the dedicated software package. This allowed for the simplification of the color-matching procedure and freed up the dentist’s time. In practice, a dental assistant could easily be trained to acquire the images necessary, then save and transmit the data to the dental laboratory in a few minutes before the dentist sees the patient. Two requirements for clinical color matching are correct color perception and visual assessment by the clinician and then the accurate transfer of information to the laboratory. From a laboratory perspective, precise visual information with an anatomic color analysis is important. The addition of shade-tab numbers anatomically matched to the target tooth provides the laboratory with more complete information. Conventional or digital photography has also been used to convey information to the dental laboratory; however, image quality is a critical factor. An inferior image provides little information and may create confusion. Superior image quality can improve tooth-color reproduction and numerical color data described by simple figures or tables and add additional useful information. The combination of color data and photographic images provided by the spectrophotometer allows for a comprehensive assessment tooth color. The spectrophotometric system also allows the dental technician to check the color of the restoration before returning the case to the dentist.
Dr. Da Silva is a current consultant for Olympus.
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|Figure 1 Tooth data acquisition.||Figure 2 Face/arch data acquisition.|
|Figure 3 Images captured by the spectrophotometer. The color of the arch and face will be corrected using the spectral data of the tooth.||Figure 4 Numerical data. Color data for the selected region are provided.|
|Figure 5 Image display and color mapping.||Figure 6 Case 1, restoration on tooth No. 8. |
Note: Left and right are two separate images.
|Figure 7 Case 2, restoration on tooth No. 8.||Figure 8 Case 3, restoration on tooth No. 8. |
Note: Left and right are two separate images.
|About the Authors|
John D. Da Silva, DMD, MPH, ScM
|Shigemi Nagai, PhD, DDS |
Harvard University School of Dental Medicine