The Direct Class IV Restoration: Case Report

Patient demand for aesthetic dentistry with minimally invasive procedures has resulted in the extensive use of freehand bonding of composite resin to anterior teeth.¹ Preservation of remaining tooth structure and using as much enamel as possible for bonding has made the procedure very predictable. In order to achieve maximum aesthetics, the dentist must be able to use multiple layers of composite along with opaquers and tints. The stratification and proper placement of opaquers and tints will help replicate the polychromatic characteristics of the natural dentition.
The clinician must have an understanding of color in order to replicate natural teeth. In natural teeth, different colors are distributed through the enamel and dentin; hence a variation in hue, chroma, and value renders the tooth polychromatic.² Hue, the “name of color,” constitutes the first dimension of the polychromatic effect and corresponds to the wavelength of light reflected by teeth.³ The second dimension, chroma, can be defined as the intensity of a color or the dimension of hue saturation. Value is represented as the brightness of color⁴ and is the most important of the 3 dimensions of the polychromatic effect. If the value is too low, then the tooth will appear gray or dark. Too high a value renders the tooth white or opacious. Utilization of opaquers and tints will allow the clinician to control the opacity and translucency of teeth. The dentin imparts the color of the tooth, and the enamel acts as a fiber-optic structure that conducts light through its rods to capture the color.⁴
Anatomical form must also be followed in order to replicate a natural tooth. One of the advantages of a direct resin restoration over a porcelain restoration is that the clinician is able to maintain control and customize the materials throughout the procedure. What will assist the dentist in creating the desired aesthetic result is the use of an opacious microhybrid, overlaid with a microfill, and customized with opaquers and tints. This combination of materials will mimic natural tooth structure far more effectively than using just a hybrid or microhybrid composite system alone. Since no single monochromatic composite resin can duplicate the complex orientation of colors evident in the natural dentition, the ability to select a variety of appropriate composite resin shades must be acquired.⁵
There is a distinct advantage to using a sandwich technique of microhybrid and microfill composite. The microhybrids can be used for strength and opacity. The microfills can be used for translucency and maintaining polishability. Finishing and polishing the restoration are fundamental to achieving a beautiful final aesthetic result, and they are paramount to maintaining the restoration over several years.
In tooth fractures, the extent of the trauma must be assessed clinically and radiographically before rendering treatment. If the fracture is too large for a direct composite restoration, then an indirect restoration could be used. It is very difficult to match a single anterior tooth. The technique of using direct resin as a restorative material is an acquired skill, and it requires practice to develop outstanding clinical results. The following procedure describes a process in which layers of different materials are used in order to make the restoration invisible.

CASE REPORT

Figure 1. Fractured maxillary left central incisor.	Figure 2. Preoperative smile.
Figure 3. A 2-mm-long bevel was placed.	Figure 4. Tooth etched for 20 seconds.
Figure 5. Occlusal White microhybrid applied to lingual.	Figure 6. Microhybrid applied to leading edge of the bevel.
Figure 7. Creative Color opaquer applied onto the bevel.	Figure 8. Microfill sculpted past the bevel.
Figure 9. Violet tint applied to Microfill.	Figure 10. White opaquer applied.

A 40-year-old patient presented to the office with a fracture of his maxillary left central incisor. The patient did not complain of any discomfort and stated that the fracture was more than 3 months old. Clinical evaluation revealed that the mesial edge was fractured and had accumulated stain as a result of cigarette smoking (Figure 1).  The full smile (Figure 2) shows polychromatic teeth, which would be difficult to restore using a single shade of composite resin.
The tooth was first cleaned using an air abrasion unit with 25-µm aluminum oxide polishing paste. A 2-mm bevel was placed on the facial (Figure 3) with a flame-shaped diamond bur (Brasseler USA), and an approximate 1.5-mm bevel/chamfer was placed on the lingual. Due to its ability to minimize the potential for microleakage and enhance bond strength to dentin and enamel, the total-etch technique was utilized. The preparation was etched for 20 seconds using Ultra-Etch 35% phosphoric acid gel (Ultradent Products; Figure 4). A clear matrix band was used to prevent the acid from contacting the adjacent tooth. This would be left in until the bonding agent was applied. The tooth was rinsed for 15 seconds and lightly air-dried, but not enough to desiccate the tooth. The enamel did appear frosty. The dentin could be rewetted with a wetting agent, but this was not necessary.
A fifth-generation bonding system was utilized. One-Step Plus bonding agent (Bisco) was applied in several coats over a 20-second period and lightly air-thinned to remove the solvent. This was light-cured for 20 seconds. The first material used for the lingual backing was a microhybrid material with a medium value to simulate enamel. Renamel  Micro-Hybrid Occlusal White (Cosmedent) was placed in a very thin layer of 0.3 mm or less to form a lingual rampart, and was light-cured for 20 seconds. The matrix strip was then removed, and because the adjacent tooth was not etched, it would not chemically bond to the preparation (Figure 5). The lingual layer should be viewed from the occlusal view to make sure there is still room for the internal layers. It should be thin and only placed to the leading edge of the long bevel, not onto it. If you desire, the matrix can be left in place, but it is better to form a contact without any material between the teeth. If etchant  was allowed to contact the adjacent tooth, then it would bond and be very difficult to separate the teeth. Therefore, care must be used during etching. With this technique, you are guaranteed a contact every time.
In order to block out the shine-through in the body of the tooth, a Vita shaded composite, Renamel Micro-Hybrid A-2, was used in a very thin layer and sculpted to the long bevel. Light-curing for 20 seconds was done. This was kept short of the interproximal area to allow some interproximal translucency in the final restoration. You do not want to go onto the bevel at this point, or a line of demarcation may show (Figure 6). Due to shine-through and the possibility of lowering the final value of the restoration, an opaquer was utilized as the next layer. In order to determine if an opaquer is necessary, you must look at the materials previously placed and note if you can see through them. If you can, you must use a little opaquer corresponding to the shade that you are using for the restoration, only in the area that needs blocking out. Creative Color (Cosmedent) opaquer Vita A-2 was placed onto the edge of the bevel, but not over the bevel, to achieve proper block-out (Figure 7). As we build up the multiple layers, less shine-through is evident. We still want to have some interproximal and incisal translucency, therefore we don’t place the microhybrid or opaquer in these areas.
Renamel Microfill A-2 (Cosmedent) was applied and allowed to go over the bevel, and was blended into the tooth. This was sculpted past the bevel in order not to have a line of demarcation in the final restoration (Figure 8). This layer was light-cured for 20 seconds.

Figure 11. Cured tints.	Figure 12. Cured light brown tint.
Figure 13. Renamel Incisal Light Microfill placed.	Figure 14. OS1 bur used on the lingual.
Figure 15. ET6 bur used on the facial.	Figure 16. Medium FlexiDisc.
Figure 17. Fine FlexiDisc.	Figure 18. Enamelize on a FlexiBuff.
Figure 19. Final restoration on day of completion.	Figure 20. Full smile on day of completion.

Prior to starting the restoration, a color map was developed, and it was determined that tints would be needed to recreate the same shade as the adjacent central incisor. Violet tint from the Creative Color kit was applied very thinly in the interproximal and incisal areas (Figure 9). This was cured for 20 seconds and followed by the application of Creative Color white opaque (Figure 10). The cured tints are shown in Figure 11. To expedite the procedure, a ResinKeeper (Cosmedent) was used to dispense all the materials and tints prior to starting the restoration. A lid is used to protect the material from light. To simulate a higher chroma area in the tooth, light brown tint was applied in a very thin area as dictated by the adjacent tooth. This was light-cured for 20 seconds (Figure 12). When using tints, it is important not to use them too heavily. They are very chromatic, and upon final polish will shine through the final restoration. Tints cannot be allowed to be finished on the surface. They must be covered with a final layer of resin. Renamel Incisal Light Microfill was placed over the cured tints and blended into the tooth (Figure 13). This was light-cured for 40 seconds prior to initiating the final contouring and polishing.
Initial contouring was started using an OS1 bur  (Brasseler USA; Figure 14) on the lingual. This will allow us to create the proper lingual contour. An ET6 bur (Brasseler USA; Figure 15) will create an invisible margin and allow the composite to disappear into the tooth. The motion is from composite to tooth structure. FlexiDiscs (Cosmedent) were used to create a highly polished restoration and to prevent future marginal leakage or white lines. Figures 16 and 17 show the use of the discs. A Jiffy polisher (Ultradent Products) will help create an even more highly polished surface. The final high glaze was applied using a FlexiBuff with Enamelize polishing paste (Cosmedent; Figure 18).  The final restoration on the day of completion is shown in Figure 19. The final full smile shows a highly chromatic result (Figure 20).
Without the proper use of all the materials described in this article, it would be impossible to achieve an invisible result. The polychromatic teeth cannot be recreated using one shade of composite. Proper finishing and polishing will allow the patient to maintain the restoration for several years. Direct composite resins require a certain amount of skill, and therefore, hands-on courses and daily practice will allow the clinician to reach a high level of proficiency.

References

1. Dietschi D. Free-hand composite resin restorations: a key to anterior aesthetics. Pract Periodontics Aesthet Dent. 1995;7:15-25.
2. Rinn LA. Applied theory of color. In: The Polychromatic Layering Technique: A Practical Manual for Ceramic & Acrylic Resins. Carol Stream, Ill: Quintessence Publishing; 1990:11-30.
3. Sproull RC. Color matching in dentistry. I. The three-dimensional nature of color. J Prosthet Dent. 1973;29:416-424.
4. Fahl N Jr, Denehy GE, Jackson RD. Protocol for predictable restoration of anterior teeth with composite resins. Pract Periodontics Aesthet Dent. 1995;7:13-21.
5. Kim HS, Um CM. Color differences between resin composites and shade guides. Quintessence Int. 1996;27:559-567.

Dr. Margeas received his DDS from the University of Iowa College of Dentistry in 1986 and completed an AEGD residency in 1987. He is an adjunct professor in the Department of Operative Dentistry at the University of Iowa. He is board certified by the American Board of Operative Dentistry and is a Fellow of the AGD. He has authored numerous articles on implant and restorative dentistry, and he lectures on those subjects. He is the director of The Center for Advanced Dental Education and maintains a private practice in Des Moines, Iowa. He can be reached at rcmarge@aol.com or (515) 277-6358.