Direct Resin Restoration of the Maxillary Anterior Dentition
Douglas A. Terry, DDS
Patient demand for minimally invasive aesthetic dentistry has resulted in the extensive utilization of freehand bonding of composite resin to anterior teeth.1 In order to achieve a functionally successful and natural-appearing direct composite restoration, the clinician must have a comprehensive knowledge of adhesive dentistry, including the properties of composite resins, proper tooth preparation techniques, the optical properties of the natural tooth, and the four dimensions of color. The objective of this article is to demonstrate the polychromatic layering of color to fabricate ten direct resin veneer restorations for the maxillary anterior dentition (Figure 1).
The ongoing development of composite resins has been a useful advancement in the field of aesthetic dentistry. Their advancement allows for the replacement of enamel and dentin with a material that mimics the physical and optical properties of enamel and dentin as effectively as porcelain, but with less invasive preparation.2 These advances in material and adhesive technology result in improved bond strengths that facilitate the use of direct bonding for the intraoral fabrication of restorations that are clinically indistinguishable from the natural dentition.
A comprehension of the color of natural teeth is critical in the consistent selection of appropriate shades of restorative materials.3 Color has been divided into four dimensions: hue, chroma, value, and translucency.4-6
Hue is understood as "the basic color of an object" (eg, blue, green, yellow).7 In dentistry, color is represented by shade systems or with designations of A, B, C, or D in accordance with a variable scale. The A shades are reddish brown, the B shades are orange-yellow, the C shades are greenish gray, and the D shades are pinkish gray. In direct resin bonding, the hue is primarily determined by the selection of the "artificial dentin" or the underlying substrate. The hue of a tooth should always be performed under appropriate illumination with color-corrected light (~5000 K).8
Chroma can be defined as the "degree of hue saturation." Within the color scale, chroma is differentiated by various shades within a set of hues (eg, A-1, A-2, A-3, and A-4). While identical hues are frequently found at the middle and cervical thirds of a tooth, distinct hues can be identified at the incisal third due to the way light is refracted, reflected, absorbed, and transmitted. Chroma can be varied in the utilization of internal characterization through the use of modifiers and tints.
The most important dimension is value,8 which distinguishes light from dark colors. The value can be defined as the "brightness" of color.9 The selection and variation of the composite resin that reproduces the "artificial enamel layer" is a principal determinant of the value of a restored tooth.
Finally, translucency significantly affects the aesthetic, vital appearance of the tooth. The degree of translucency is determined by the amount of light that penetrates the tooth or the restoration prior to being reflected externally.9
Initially, a waxup was performed to facilitate patient education and the fabrication of a custom acrylic intraoral template to ensure accurate tooth morphology. Preoperative photographs were taken for smile line analysis. Shade selection was performed and reviewed with the patient prior to rubber dam isolation to prevent dehydration and subsequent value elevation.10
The appropriate composite material was then selected. As no single composite resin fulfills all the requirements of color, function, and aesthetics, it is necessary to select different composite materials for the "artificial enamel" and the "artificial dentin" layers.10 Accordingly, materials that offer the widest range of colors can be successfully utilized in anatomic stratification techniques.1
Once anesthesia was administered, the teeth were isolated with a rubber dam. The veneer preparations were performed using diamonds with gauged depths. A long, tapered diamond was utilized to connect a series of vertical grooves along the facial surface to provide uniform reduction of the facial surfaces.11 A cervical chamfer 0.3 mm in depth was placed supragingivally following the free gingival margin from papilla tip to papilla tip (Figure 2). The lingual aspect of the chamfer was extended 2 mm onto the lingual surface, but not on the occlusal contact area.12 The preparations were completed with a finishing disk and polished with rubber cups containing a premixed slurry of pumice and 2% chlorhexidine. The preparations were rinsed and lightly air dried. A soft metal strip was placed interproximally to isolate the prepared tooth. Using the “total etch” technique, the preparation was etched for 15 seconds with 37.5% phosphoric acid gel, rinsed for 15 seconds, dried for 5 seconds, and lightly air thinned. The dentin and enamel were remoistened with water on a cotton pellet. Once a hydrophilic adhesive agent was applied, the excess was removed, and the agent was light cured for 30 seconds. Any excess adhesive over the margins should be removed during finishing procedures to avoid adverse periodontal sequellae.
Development of the Dentin Layer
The first layer--the artificial dentin body--of A-1 shaded composite resin was applied and contoured with a short-bladed composite instrument and smoothed out with an artist’s sable brush (Figure 3). This process was repeated with a second layer of hybrid composite to form the dentin lobes (Figure 4). In order to prevent overbuilding of the artificial dentin layer, it is imperative to constantly monitor the composite material from the incisal aspect. Each increment was polymerized with a curing unit for 10 seconds.
To alter the chroma, a honey-yellow tint was thinned with clear liquid resin and applied at the gingival one third and gradually faded out at the incisal edge of the body layer. The areas underlying the mesial and distofacial line angles were highlighted with a diluted white modifier; the honey-yellow mix was used again to tint the surfaces lingual to these lines. A thick layer of the aforementioned mixture was applied to the canines to match the higher chroma of these two teeth. This process established the hue and chroma of the dentinal portion of the veneers.
Internal Color Characterization
To re-create the natural translucency of the enamel, a blue tint was thinned 20% with clear liquid resin and applied vertically at the mesial and distal line angles; increased emphasis was placed on the incisal corners to simulate translucency (Figure 5). A mixture of 40% white color modifier, 10% honey-yellow, and 50% clear liquid resin was then applied vertically at the incisal edge of the tips of the dentin lobes to accentuate their presence.
Development of the Enamel Layer
The artificial enamel was restored with incisal light microfill composite resin to achieve the proper value of the restoration. The resin was rolled into a ball and placed on the cervical region of the tooth (Figure 6). Using the short-bladed composite instruments, the composite material was sculpted and adapted to obtain an emergence profile that encased the underlying matrix cervicoincisally and mesiodistally (Figure 7). The microfilled resin was spread over the entire facial surface, and the final layer was slightly overcontoured to allow sufficient thickness for contouring and polishing.
Finishing and Polishing
The facial contouring was initiated with #8 and #16 fluted burs (Figure 8). The gingival and interproximal contouring and finishing were completed with #8 and #16 fluted burs, respectively (Figure 9). The lingual surfaces were contoured with #8 and #16 fluted burs.
Finishing strips were then used in the interproximal region; finishing on the proximal, facial, and incisal angles was performed with aluminum oxide disks and finishing strips. For characterization, finishing burs, diamonds, and rubber wheels and points were used to create similar indentations, lobes, and ridges. Ultrafine polishing disks were used to impart a high luster while maintaining the existing texture and surface anatomy (Figure 10). Each restoration was polished for 30 seconds with paste on a moistened rubber prophy cup. Superfine finishing strips were used with polishing paste to refine the interproximal regions (Figure 11). The interproximal areas were examined with dental floss to verify adequate contacts and the absence of gingival overhangs (Figure 12). Occlusion was evaluated. Any necessary equilibration was accomplished with a finishing bur. The overall aesthetics of the patient were evaluated and included analysis of shade, contour, facial anatomy, texture, and smile line (Figures 13-14-15-16-17). The postoperative result of the maxillary anterior composite veneers reflects the harmonious integration of form, function, biocompatibility, and aesthetics.13
Advances in material technology and adhesive dentistry have enabled the development of freehand bonding techniques that allow the provision of conservative treatment.10 A composite layering technique combined with proper finishing protocols can achieve harmonious restorations.14 Clinicians may apply their knowledge of color to select and place composite resin to create bonded resin veneers that closely simulate the optical properties of a natural tooth, thus preserving the direct-bonded resin option as a valuable treatment modality.
*Private practice, Houston, TX.
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