Written by Dino S. Javaheri, DMD Saturday, 31 July 2004 19:00
Subtle changes in the apparent size of teeth can be achieved by altering line angle, texture, and color. Teeth can be made to appear thinner, longer, shorter, smaller, or wider without changing the actual outline shape of a tooth. Such alterations only apply to incisor teeth, since all other teeth are only seen in profile from a straight-on view.
An option is to improve the position of the line angles. The general patterns for line angles of the maxillary incisors are displayed in Figure 1. The mesial line angle of a central incisor is relatively straight with a sharp curve inward toward the incisal. The distal angle is a little softer and has more of an overall curve. The lateral incisor's mesial line angle is very similar to that of the central incisor. However, the distal is quite different. The distal line angle of the lateral follows more of a c-shaped curve.
|Figure 1. Common position of line angles for maxillary incisors. |
|Figure 2. Reflective surface in white, deflective surface in black.|
|Figure 3. Preoperative view of patient with large, darkened central incisors.||Figure 4. Gingival recontour to achieve similar tooth proportions.|
|Figure 5. Length adjusted to proposed new position.||Figure 6. Depth cuts placed for veneer preparations.|
|Figure 7. Final preparation with retraction cord in place.||Figure 8. New veneers try-in. Note that veneers appear large.|
|Figure 9. Distal line angles moved medially to reduce reflective surface.|| |
Figure 10. Final restorations with reduced reflective surface
These line angles define the 2 surfaces of each incisor: reflective and deflective (Figure 2). The reflective surfaces are the areas inside the line angles. When light hits this area, it reflects right back. The areas outside the line angles are deflective areas. Light bounces off these areas and goes off to the side. Line angles can be moved to change the sizes of the reflective and deflective surfaces. The larger a reflective area that is created, the larger the tooth will appear.
A smaller-shaped reflective area makes the tooth appear smaller. Moving the line angles inward reduces the size of the reflective area, therefore making the tooth appear smaller. Moving the line angles outward increases the size of the reflective area, making the tooth appear larger.Surface texture follows the same principle as line angles. The more surface texture that is present, the more miniature deflective areas are created on a tooth, and the tooth appears smaller. The smoother the surface of the tooth, the more light reflects back, making the tooth appear larger.
Using these principles, the options to alter the perception of a tooth's size are the following:
(1) Narrower- move line angles medially, increase facial embrasure, move proximal contacts lingually, increase textured surface, and create vertical lines.
(2) Widen- move line angles laterally, decrease embrasures, move proximal contacts facial, flatten facial surface, and create horizontal lines and texture.
(3) Lengthen- flatten cervical convexity (height of contour), remove cemento-enamel junction, and create vertical texture and lines.
(4) Shorten- establish prominent cervical convexity, move cervical convexity toward incisal, emphasize cemento-enamel junction, create horizontal texture and lines, and place lingual tilt of incisal.
A 30-year-old male presented for aesthetic enhancement of his smile. His chief complaints were the color and size of his central incisors (Figure 3). His central incisors had always been large and prominent.Adding to the aesthetic concern, about 10 years ago he had fallen off of a bicycle and hit the ground hard with his face. His central incisors received much of the initial impact force. The teeth did not break and stayed vital, but changed color over time. Several attempts at bleaching had achieved limited results. Also, the results were short term, as the teeth rebounded back to their original shade within a year.
Treatment options were reviewed with the patient. The patient elected to have veneers placed on the 2 maxillary central incisors, since he was pleased with the rest of his smile. After anesthetizing the patient, a diode laser was used to recontour the tissue height of tooth No. 8 to match tooth No. 9 (Figure 4). The teeth were then shortened to achieve the new proposed incisal edge position (Figure 5). A template was taken for temporary fabrication and for laboratory communication. After that, depth cuts were placed and the veneer preparations completed (Figures 6 and 7). Extra facial reduction was done to allow room for the laboratory technician to block out the dark preparation color. A vinyl polysiloxane final impression was taken and temporary veneers were fabricated. The patient was seen a week later for evaluation and patient feedback of the new proposed length.
At the cementation appointment, the new restorations were tried in. Although the shade seemed appropriate, the restorations still appeared large (Figure 8). The enhanced surface texture was appropriate, but distal line angles of the restorations were placed laterally. This made for a large reflective surface and the appearance of large teeth. To reduce the size of the reflective surface, the distal line angles were moved medially (Figure 9). This slight adjustment gave the teeth the appearance of being narrower. The adjusted areas were polished andrestorations placed with a resin cement (Figure 10). The patient was very pleased with the restorations.CONCLUSION
Using the principles discussed in this article, the clinician can readily alter the perception of tooth size and thus positively affect the aesthetic outcome of treatment.
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