March 1, 2014
by Laurie St-Pierre, DMD, MS
Fractures of the anterior dentition are a common condition mostly among young patients. Dental materials, such as composite and ceramics offer the possibility to create highly esthetic restorations. However, when there is a considerable amount of healthy tooth structure remaining, the material of choice for most anterior restorations is composite in order to preserve sound tooth structure.7 When restoring the anterior teeth, it is crucial to obtain a restoration that is in perfect harmony with the adjacent teeth in terms of shape, shade, opacity and translucency, but this requires knowledge and skills. The purpose of this article is to briefly review the optical properties of natural dental tissues and how they may be predictably replicated using different composite shades and opacities in a direct class IV restoration illustrated with a case report. Excellent esthetic results may be obtained if the restoration is meticulously planned, the composite precisely placed, finished and polished with attention to details.
OPTICAL PROPERTIES OF ENAMEL, DENTIN AND COMPOSITE
To improve the esthetic potential of a restoration and to achieve a seamless result, the restorative dentist must understand the optical properties of enamel and dentin as well as those of composite materials.6
Natural tooth structure presents different characteristics such as opacity, translucency, fluorescence and opalescence. These variations are due to the lack of uniformity in the quantity of enamel and dentin from cervical to incisal (Fig. 1). The color and opacity of the tooth originate from dentin6, the enamel being mostly translucent and colorless.14 Opacity is more prominent in the cervical third because dentin is thicker while enamel is thinner in that area. Inversely, translucency is often more important in the incisal third, where dentin is thin or absent and enamel is thick, which may also create some effects such as the perception of dentinal lobes, a high level of translucency and sometimes, a halo effect at the incisal edge. If they are present on the adjacent teeth, these effects must be reproduced in the composite restoration.
These optical characteristics vary from patients to patients and depend also on the degree of incisal wear. Although natural teeth are often polychromatic, some patients present teeth that are mainly monochromatic. In these cases, a single shade restoration using a medium opacity or a body shade is appropriate. However, some patients, especially young patients,4 have polychromatic teeth with translucency and halo effect at the incisal edge. In these cases, polychromatic restorations using layers of different shades and opacities will help to blend the restoration in the natural tooth structure and make it imperceptible.16
Composite materials differ among manufacturers in many aspects such as their matrix composition, the size and morphology of their filler particles as well as their filler content. These variations in composition influence their handling properties, their physical and optical properties, their shades and their polishability. Newer composites generally have small particles with improved properties facilitating the creation of highly esthetic restorations.15 Moreover, most manufacturers offer a wide range of opacities for a given shade to mimic natural tooth structure and to create dentin and enamel effects (Fig. 2). Therefore, dentin must be replaced with a high opacity material, more saturated in color, and enamel with a more translucent material. However, composites and enamel usually do not have the same translucency4 and a more translucent material within the restoration is often required. The thickness of the different shades and opacities is important because if the enamel layer is too thick, the value of the restoration will be low and lead to a gray appearance. Conversely, if the dentin layer is too thick, the restoration will appear too opaque.
FIGURE 2. Composites are available in different shades and opacities to reproduce natural tooth structure. Illustrated here is a nanofill composite (ie, Filtek Supreme Ultra, 3M ESPE, St-Paul, MN, USA).
One considerable challenge for anterior restorations is shade selection. Generally composite shades are based on the Vita Classical Shade Guide (Vident, Brea, CA, USA). However, this shade guide is not made of composite and its use may lead to a restoration that is not exactly as the planned shade. To overcome this issue, it is suggested to fabricate a custom shade guide14 using the composite used in the office (Fig. 3). It is also important to evaluate the tooth while it is fully hydrated with the shade tab at the same bucco-lingual position than the evaluated tooth to avoid mismatch in light reflection. Generally, the correct enamel shade is the one obtained directly from the shade guide and the dentin shade is one shade darker.10
FIGURES 3A-E. Fabrication of a custom shade guide. An impression of an existing shade tab (ie, Vita Classical, Vident) is made using a putty material. Composite is placed and adapted into the mold and fixed to a stick. The composite is then polymerized and polished.
FIGURE 3B. FIGURE 3C.
To confirm the shade selection, some enamel-like shade composite may be placed on an unetched tooth with no adhesive at the incisal edge. This composite mock-up should cover partially the facial aspect of the tooth respecting the required restoration thickness to avoid having shade mismatch if the composite is too thin or too thick. It is advantageous to have the composite mock-up longer than the tooth in order to see the effect when there is no tooth structure behind (Fig. 4). The composite mock-up must be polymerized since its shade might change upon polymerization2 and then hydrated before evaluation.
TREATMENT PLANNING, DIAGNOSTIC WAX-UP AND LINGUAL PUTTY MATRIX
When planning a class IV restoration, a diagnostic wax-up is helpful to determine the ideal anatomical contours and symmetry. It also allows for the fabrication of a lingual putty matrix, (Fig. 5a-e) essential to control each composite layer thickness when using multiple shades and opacities. However, a diagnostic wax-up is not essential to generate a lingual putty matrix, since it may also be obtained directly intraorally with a polyvinyl siloxane after placing a composite mock-up to the desired shape.
FIGURE 5C.Lingual putty matrix covering the lingual surface and the incisal edge.
Although the preparation of a class IV is usually limited to the fracture, bevels help to mask the transition between the composite and the tooth structure17 and contribute to improve retention and marginal seal. Moreover, for an imperceptible composite-tooth margin, it is suggested to create a long irregular bevel (2-3 mm) on the facial surface, starting at the dentin-enamel junction and decreasing in thickness towards the cervical. A composite contouring disc (ie, Sof-Lex disc, 3M ESPE, St-Paul, MN, USA) may also be used to make an invisible margin and to round all sharp angles for a better composite blend17 (Figs. 6-8). The lingual bevel is usually limited to 1 mm (45).
FIGURE 8. Long irregular bevel (2-3 mm) on the facial surface and rounded angles.
For the restoration described in this case report, adhesive procedure was performed using a total etch system (ie, OptiBond FL, Kerr, Orange, CA, USA) with the adjacent teeth protected from etching with teflon tape. A nanofill composite (ie, Filtek Supreme Ultra, 3M ESPE, St-Paul, MN, USA) was then selected. The lingual matrix was placed on the teeth and composite was adapted to the matrix and to the tooth structure in a thin layer (about 0.3 mm) to create a lingual shell.5,17 This layer may be an enamel, a translucent or even a higher opacity shade depending on the desired effects the operator wants to create at the incisal edge. In the presented case, a translucent shade (ie, Amber translucent (AT)) was used to obtain high level of translucency as it was observed on the unaltered contralateral central incisor. Interproximal enamel (ie, WE) was then placed and adapted to the lingual shell (Fig. 9). Dentin shade (ie, B1D) was then applied slightly over the facial bevel to conceal the fracture line and sculpted to the desired anatomy with developmental lobes (Fig. 10). The thickness of the dentin layer is crucial at this point and should be evaluated from the incisal edge before its polymerization to ensure that an enamel layer thickness of at least 1 mm on top.
In order to allow dentinal lobes to show through the enamel layer, translucent composite (ie, Clear translucent (CT)) was applied between the dentinal lobes and between the dentin and the interproximal enamel (Fig. 11). Some effects may be added if desired using tints such as Kolor Plus (Kerr, Orange, CA, USA) at the incisal edge to accentuate the halo effect and/or sparingly on the composite surface to create diffuse hypocalcification stains. In this case, white tint was placed at the incisal edge in a thin layer to accentuate the halo effect. It is important to use these tints within the stratificati
on, because if used on the surface, they will not resist to wear and will degrade rapidly.10
FIGURE 11. Addition of clear translucent composite between the dentinal lobes and between the dentin and the interproximal enamel.
The final enamel layer (ie, WE) was then placed in one increment and carefully adapted to replicate proper line angles, anatomy and symmetry. Careful attention to details at this stage will significantly minimize excessive finishing procedures and the time associated with these (Fig. 12).
FIGURE12. Final enamel layer (WE).
FINISHING AND POLISHING
Except for occlusal adjustment, finishing and polishing are final and crucial steps to optimize esthetic results and longevity of the restorations. These steps are important to establish proper anatomical and physiological contours as well as surface texture and gloss similar to natural enamel. Finishing and polishing also help to maintain a good oral health, minimizing gingival inflammation and recurrent caries by the reduction of plaque adhesion and staining on rough surfaces.1,8,12,19 However, excessive finishing and polishing may affect marginal adaptation of the restoration,3,9,11,13,18,19 which often clinically appears as a white line at the margin. This white line is believed to be caused by the adhesive breakdown possibly due to heat, pressure and direction of rotary instruments, which should be directed from composite to tooth structure whenever possible.11
In the illustrated case, the first finishing step was to establish the length, the bucco-lingual position of the incisal edge and the incisal embrasures with a coarse finishing disc (Sof-Lex XT, 3M ESPE) according to the natural plane of the incisal edge. Then, gingival embrasures and gingival excesses were eliminated using a flame diamond finishing bur and a #12 scalpel blade. Lingual excesses were removed using a diamond egg shaped bur.
To help visualize interproximal lines angles and verify their symmetry, these lines were marked with a pencil and modified using a finishing disc (Fig. 13). Interproximal surfaces were finished with diamond strips (ex. VisionFlex (Brasseler, Savannah, GA, USA) and polished with plastic strips (eg. Epitex, GC America Alsip, IL, USA).
When proper contours were established, developmental grooves (Fig. 14) and surface texture were made with a fine diamond bur (8862.31.014, Brasseler) on a slow speed handpiece. Surface texture improves vitality and natural appearance of the restoration.
FIGURE 14. Developmental groove were marked with a pencil and contoured with a finishing diamond bur.
Finally, to obtain a glossy surface, polishing procedures were performed using a sequence of rubber polishers, starting with a coarse rubber polisher (ie, Jiffy Cup, Ultradent, South Jordan, UT, USA) and followed by a two-step polishing system (ie, HiLuster Plus, Kerr). A diamond polishing paste (ie, Porcelize 3 microns, Cosmedent, Chicago, IL, USA) on a felt buffing disc (Flexibuff mini, Cosmedent) was used for the final gloss (Figs. 15 & 16).
FIGURE15A. & B: Final facial view of immediate operative result after polishing.
FIGURE 15A. FIGURE 15B.
FIGURE 16: Incisal view of the finished restoration.
Composite restorations allow for the conservation of healthy tooth structure while meeting high esthetic patients’ expectations. Most dental composites offer a wide range of shades and opacities to restore anterior teeth. The key to success is to plan the restoration carefully and to reproduce the optical details and characteristics observable on the adjacent teeth. With a proper layering technique using multiple shades and opacities, it is possible to predictably obtain seamless restorations that are in harmony with adjacent teeth. OH
Laurie St-Pierre, DMD, MS, Assistant professor, Department of Operative Dentistry, Laval University, Quebec City, QC, Canada.
Oral Health welcomes this original article.
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