Computerized Shade Selection and the Complex Class IV Composite

The cosmetic revolution of modern dentistry has seen vast improvements in aesthetic materials and techniques. With it the dental patient’s expectations have also risen. Thirty years ago patients were ecstatic to have universal composite for any anterior restoration. Now they expect the invisible restoration.

Materials science has greatly improved since those early days. With the strength of microhybrids and the finishing ability of microfills, restorations can be made to blend with the surrounding tooth structure. The difficulty comes in selecting the proper shades of materials to be used.

Figure 1. Traditional color mapping.

Standard shade selection has always been done visually with the use of shade guides. By placing shade tabs adjacent to the tooth to be repaired, dentists have used color mapping to guide them through the restorative process (Figure 1). Problems exist, as shade selection is dependent on light source for illumination. Daylight, fluorescent light, and incandescent light all have different temperatures. Different temperatures of light produce different color spectrums of absorption and reflection. Establishing proper hue, value, and chroma as outlined in Munsel’s color wheel is dependent on operator expertise.1

Currently, new ways of shade selection exist. With the use of digital technology, subjective color selection is eliminated, making an accurate color match possible even for an inexperienced operator. Several digital systems exist in the market, each with a slightly different technology regarding how they acquire their data. The predominant use of these digital shade systems has been the matching of porcelain restorations to the existing dentition.2 This article describes the use of one of these systems (ClearMatch, Smart Technology) for shade selection in the direct placement of composites in a class IV restoration.

Technique

ClearMatch is a software program that uses images captured with a digital camera. The digital images are then manipulated on the dentist’s own computer, output to either a printer or disc, and sent to a lab. Most other digital shade-matching systems are stand-alone units and have their own built-in capture device.

ClearMatch accomplishes shade matching by a process of normalization. This means comparing an unknown color (the color of the image) with known colors, capturing the references in the same image. The software knows the color of the references and adjusts the image taken to override different cameras, different lighting conditions, and different light sources to produce a detailed color map.3 ClearMatch uses a minimum of three references to calibrate and determine the image’s color. One of three different shade systems can be utilized: Vita Classic, Vitapan 3D, or Chromoscope.

Before isolating the tooth to be restored and beginning the composite restoration, the following shade-matching technique is used:

Figure 2. Hemostat holding reference guide and known Vita shade tabs. Figure 3. Taking shade image in patient’s mouth.
Figure 4. Shade image loaded into ClearMatch for processing. Figure 5. Color-mapped image with color references.

(1) The black and white reference supplied by ClearMatch, along with one to two shade guides of the shade system you would like to use, are held in a hemostat (Figure 2).

(2) The hemostat with references is placed beside the tooth to be matched. Try to orient references on the same plane as the tooth to be matched (Figure 3).

(3) Use the office digital camera to take an image. Shoot the image at a slight angle to minimize flash reflection.

(4) Load image into software.

(5) Follow software instructions, set white, black, and shade references (Figure 4).

(6) Display or print color-mapped image (Figure 5).

Once you have printed the color-mapped image with color references along the bottom border, you are ready to isolate the tooth to be restored with a rubber dam and begin your composite restoration.

CASE STUDY

Initially the patient was seen on an emergency basis with a fractured MI on No. 8. A digital image was taken using a Fuji S-1 with a Nikon macro lens and dental dual flash, with the Vita Classic as a shade reference (Figure 3). Vita Classic was used because it matches the composite systems, Renamel microhybrid and microfill (Cosmedent), used for anterior restorations in my office. Should you use a different composite system, you can choose between Vita Classic, Vitapan 3D, or Chromoscope.

Figure 6. Pre-op image of tooth with temporary filling.

This digital image was then loaded into ClearMatch, and a color-mapped image was created (Figure 5). From this, a base shade of D3 was chosen. A composite buildup was placed to serve as a temporary restoration and help create a putty matrix to be used at the next appointment to locate incisal edge position and lingual wall position (Figure 6).

Figure 7. Preparation of No. 8 with disappearing margin.

At the second appointment, anesthetic was given, the tooth was isolated with a rubber dam, and the temporary filling was removed. A long bevel of approximately 2 to 3 mm was placed on the facial surface, and then an invisible finish line was added using a fine diamond (Figure 7). This allows the practitioner a better chance for invisible margins. The lingual was ended with a butte margin. A 10-second etch with 35% phosphoric acid was followed by a 30-second water rinse. Gluma (Heraeus Kulzer), used as a desensitizer and wetting agent, was then applied for 30 seconds, and the preparation was blotted dry with a microbrush. Excite dentin bonding agent (Ivoclar Vivadent) was applied, and an Adec air dryer was used to evaporate the solvent. The bonding agent was light cured for 20 seconds.

Cosmedent’s Renamel microhybrid and microfill composite systems were chosen for this case. Microhybrids allow for strength while the microfill is used for polishability. The advantage of using this microhybrid is that it is color coordinated with its microfill. Thus, if you want to use a C3 microfill, you can back it with a C3 microhybrid. The putty matrix created at the last appointment was placed over the tooth, and a stratification technique was then used.4 A Global surgical microscope fitted with an orange light filter was used during the procedure, so composite cure times would not be affected. A thin layer of Renamel microhybrid occlusal white was taken up the entire lingual surface to the incisal edge. At this point the color map created by ClearMatch was used (Figure 5). The adjacent tooth’s color was D3 with a ring of C3. Mirror imaging these shades created the restorative blueprint for the restoration of the fractured tooth. Renamel microhybrid composite was then layered according to the color map to the depth of the DEJ. Renamel microfill composite of the same color-mapped shades was then layered, smoothed with a sable brush, and a final layer of medium Incisal Renamel microfill was placed over the entire facial surface of the restoration. Again, the area was smoothed with a sable brush. The entire restoration was then light cured for 40 seconds with a De-Ox (Ultradent) coating. The use of De-Ox allows for complete curing of the restoration by eliminating the air-inhibited layer.

A Kavo electric latch handpiece at a slow setting along with 3M ESPE discs and Cosmedent rubber wheels were used to polish the restoration. Epitex (GC America) strips and a No. 12 scalpel helped to trim flash and refine the gingival embrasure. Cosmedent’s diamond polish with flexibuff wheels was used to obtain the restoration’s final polish. At this point the rubber dam was removed and the occlusion was checked in centric and all excursive movements.

Figures 8, 9, and 10. Final photos of restored tooth.

The patient returned  1 week later for final photos after the teeth had rehydrated (Figures 8 through 10).

Summary

By utilizing digital shade mapping, a stratified composite technique, and the proper composite system, the dental practitioner stands a greater chance of meeting patient expectations. In the case presented, the use of the ClearMatch system helped simplify shade selection, which is the greatest variable in success of anterior composite restorations.


References

1. Vanini L. Determination and communication of color using the five color dimensions of teeth. PPAD. 2001; Jan/Feb:19-26.

2. Chu S. Digital shade analysis and verification: a case report and discussion. PPAD. 2001; March:129-136.

3. Smart Technology. User’s Guide. Manual for Digital Shade System. 2001.

4. Dietschi D. Free-hand bonding in the aesthetic treatment of anterior teeth: creating the illiusion. J Aesthetic Dent. 1997;9:156-164.



Dr. Hovden practices comprehensive dentistry in Daly City, Calif. He maintains a faculty position in endodontics at University of the Pacific and has completed several postgraduate continuums in advanced dentistry at PAC~Live, The Seattle Institute, The Center for Advanced Dental Study, and Dental Education Laboratories. Dr. Hovden is a member of the ADA, AACD, AES, AGD, and AAE. He can be contacted at (650) 755-6000.