Tooth morphology, our primary goal

Community - Direct anteriors
24 May 2016

Reproducing esthetically pleasant anterior restorations requires that clinicians combine artistic skills with fundamental knowledge of tooth morphology, along with selection and use of appropriate composite resin materials [1]. According to Newton Fahl, “This involves comprehensive understanding of tooth shape, color and function and the teeth’s natural optical properties in order to select the most appropriate replacement materials” [2].
Today’s composite resin systems offer the clinician various enamel and dentin shades to mimic the variations of tooth opacities and translucencies [3,4]. Their main objective is to allow replication of the combined optical properties of dentin and enamel. For small anterior Class III or V restorations, only one shade may be necessary, because composite resin is relatively translucent, allowing the adjacent and underlying tooth structure to reflect or show through the restoration [5]. However, for larger through-and-through Class III and IV restorations, which have no backing tooth structure, a relatively translucent composite may not be able to mask the dark background of the oral cavity [6]. Therefore, the multilayer technique is recommended, in which an opaque material is placed beneath a translucent composite resin in an effort to create depth from within the restoration and to mask the dark background[7]. The decision of when to use this technique involves three considerations. According to Vargas [8] if the adjacent teeth or the tooth to be restored in a through and through preparation is polychromatic in nature and no incisal halo or translucency is evident, the tooth may be restored with two shades of composite resin, other wise a translucent and white opaque shades are indicated to restore the incisal translucency or a halo effect. Once the decision is made to use more than one shade, the clinician needs to know the level of translucency of the composite resins being used, since in certain brands a 2 mm thickness of the body shade (referred to as Universal) of composite resin may be enough to mask the dark background of the oral cavity [9].
Finally, it is important before restoration to evaluate the tooth morphology (line angles, developmental grooves and superficial texture) and how to reproduce those details by sculpting the composite and contouring with finishing burs and disks.
The purpose of this article is to describe in detail how one patient’s maxillary central incisors were restored using a direct composite resin technique. The previously placed layered Class IV resin composite restorations on both central incisors were removed, and the patient’s smile was enhanced using a two-shade simplified build-up technique.

Fig. 1

Img. 1 – A caries-free 25-year-old male patient expressed dissatisfaction with the appearance of his smile after recently-performed direct composite resin restorations.

Fig. 2

Img. 2 – During the examination, it was determined that the Class IV composite resin restorations on both central incisors did not match in color, contour or texture. A composite veneer was also placed on the left lateral incisor in order to “align the tooth” with the central incisors. All the restorations contained opaque white and translucent resin composite used in an attempt to simulate the natural appearance of dental tissues. The layering technique used was inadequate and the final result was compromised.

Fig. 3

Img. 3 – The right lateral incisor was used for shade selection since it had not been restored. A mild color gradient and translucency in the incisal third was found. A decision was made to replace the existing restorations using a two shade-technique, focusing mainly on establishing ideal contours and texture. Shade A2 body was selected for the ‘dentin’ aspect of the restoration by placing the shade tab in a horizontal position and matching the middle third of the tab to the middle unrestored third of the left central incisor. The facial enamel shade should generally be one shade lighter, so A1 body was selected for the facial aspect of the restoration.

Fig. 4

Img. 4 – The existing restoration on the right central incisor was removed. A 1.5 mm 75° functional-aesthetic enamel bevel was prepared using an 8888 diamond bur on the facial. The lingual bevel was a 45° functional bevel. A coarse disc was then used to extend the facial bevel inter-proximally and towards the gingival third of the facial surface to create a so-called ‘infinite bevel, with which the composite resin margin will be indistinguishable after restoration.

Fig. 5

Img. 5 – Teflon tape was placed on the adjacent teeth to prevent their being etched. This was followed by the application of 32% phosphoric acid to enamel and dentin for 15 seconds. The acid etchant was then rinsed for 30 seconds, excess water eliminated and a two-step dental adhesive applied. This adhesive was considered to provide a more reliable enamel bond than the supplied self-etching adhesive.

Fig. 6

Img. 6 – The lingual PVS matrix was then seated followed by application of the lingual layer of A2 body shade composite resin to form a lingual shell.

Fig. 7

Img. 7 – After light-curing the first increment, the PVS matrix and Teflon tape were removed and a Mylar strip placed to restore the interproximal walls and contacts. At the same time, thickness was added to the lingual shell.

Fig. 8

Img. 8 – A final 1mm A1 shade composite resin layer was applied extending from the facial bevel toward the incisal edge and onto the mesial and distal contact areas to restore the line angles.

Fig. 9

Img. 9 – After polymerization of this layer a thin lead mechanical pencil was used to establish the positions of transitional line angles according to the tooth planes.

Fig. 10

Img. 10 – The main objective was to establish correct lengths and contours.

Fig. 11

Img. 11 – After removal of the composite restoration on the left central incisor, esthetic and functional bevels were prepared and restoration completed following the same protocol described above and shown of the following images (12 and 13).

Fig. 12

Img. 12

Fig. 13

Img. 13

Fig. 14

Img. 14 – The finishing process was initiated with coarse and medium-coarse discs following the contours of the contralateral tooth, followed by the use of the 8888 fine diamond and ET6 extra fine diamond bur for texture and microanatomy. Finishing strips were used interproximally to eliminate flash and coarse medium and fine rubber polishing points were used on the lingual surface after occlusal adjustment.

Fig. 15

Img. 15 – Final esthetic evaluation of shade and texture of the restoration was done 15 days post-operatively.

Fig. 16

Img. 16 – A happy and satisfied patient is the ultimate goal of every restorative dentist, this is why simple but well executed techniques are a must.