Earlier in this series of articles, we started by looking at the etiology of midline diastemas and then examined some of the challenges you might encounter during evaluation and treatment. Now, let’s get into the specifics of providing that treatment as we look at the restoration process.
Restoration with Direct Resin: Step-by-Step
I prefer to restore one central incisor at a time, starting by optimizing the mesiodistal width and inclination of the mesial surface, and then building the other central incisor to the restored incisor.
Although this takes slightly more time than restoring both centrals simultaneously, the risk of having centrals of dissimilar width and a midline cant is eliminated, which reduces stress and the potential for re-treatment.
The first stage, then, is to measure the interincisal distance — the distance between the distals of both central incisors (Figure 1). The best and most accurate way to do this is with a digital vernier caliper with fine jaws. This measurement is divided by two to give the final restored width of one central incisor.
The tooth is then prepared (Figure 2). Any existing restorations and caries are removed; a # 12 scalpel blade or a sharp sickle scaler can be useful to remove any debris at the gingival without causing bleeding. Any staining, along with the aprismatic enamel layer, is removed with particle abrasion. (For more on this technique, see this article.)
Finally, the interproximal is finished with a Brassler Coarse metal strip.
For larger diastemas (2-3mm), a putty matrix fabricated from a diagnostic mockup can be used to guide the restoration; however, for smaller diastemas (1-2mm) there is not enough space for the putty matrix to be a practical solution. In these cases, I use a different matrix.
A good solution is a metal sectional posterior matrix of heavier gauge (for example, a Garrison M200). The matrix is placed into the sulcus (Figure 3).
If pressure from a digit is used to adapt the matrix palatally (Figure 4), the band will torque, creating a nice emergence profile.
The band can be wedged if necessary (often required with intermediate diastema, less so with simple). Teflon tape or VursaWedge are good options here. If a rubber dam has been placed with floss ties, the matrix can easily be placed between the floss tie and the tooth. The floss tie will then double as the wedge to secure the band.
The tooth is then etched, primed, and adhesive placed. I prefer a fourth-generation dentin bonding agent due to the higher bond strengths.
The restoration is then built to half of the buccolingual thickness of the anticipated final tooth with an opaque (sometimes called dentin) resin mass.
It is critical to use an opaque resin for the palatal half of an intermediate diastema closure because if a universal chromatic enamel alone is used, the restoration will be too translucent and will appear gray (Figure 5). This is a common error.
The opaque resin is placed with a flap plastic such as an IPCL and carefully adapted to the tooth with a #3 brush and modelling resin and then polymerized.
You will note that at this stage, the resin is deliberately overbuilt. This allows some tolerance to adjust the restoration to the required mesiodistal width and to correct the angulation of the midline. The operator should not attempt to create the ideal final incisor width at this stage.
The restoration is then built to full contour with a universal chromatic enamel [Figure 6] and again adapted with a modeling resin and brush.
The chromatic enamel is more translucent than the opaque composite, creating a lifelike appearance on the facial surface.
The resin is then polymerized. Glycerine is then placed on the restoration surface, and the restoration is again polymerized to remove the oxygen-inhibited layer, as described in this article. The completed restoration should be too wide.
The digital vernier gauge is then reset to the width of one restored central incisor and taken back to the tooth [Figure 8]. A propelling pencil is used to mark the ideal position of the final mesial contact point.
The mesial is then finished with metal strips and discs, taking care not to create a cant. This is best achieved by sitting the patient upright and working face-to-face with the patient rather than in the conventional operating position. With good lip retraction, the disc is held parallel to the nose and at right angles to the interpupillary axis to create the correct mesial contour. Discs progress from coarse to medium, fine, and superfine to create a highly polished contact point. Care should be taken to form a mesial line angle on the facial and facial and palatal embrasures to facilitate flossing [Figures 9 and 10].
On completion, the mesio-distal width is confirmed with the caliper before progressing to the next phase.
The next stage is to place the metal matrix on the contralateral incisor. The procedure is then repeated. The width of this tooth has already been defined by correcting the width of the initial incisor to be restored. This means that the second step is much faster.
Both incisors are then finished and polished with # 12 scalpel blades, finishing strips, and discs/silicone points.
At this point, occlusion is checked, and the patient is dismissed.
A Clinical Case
In this case, the patient presented with a midline diastema and an existing incongruous Class 4 resin restoration on his 2.1. The treatment plan was to restore both teeth with direct resin.
Typically, I find it more efficient to restore the simplest tooth firs t— that is 1.1 in this case.
The tooth was isolated with a rubber dam and floss ties, and the existing restoration in 2.1 removed. Particle abrasion was performed.
Tooth 1.1 was restored with a metal matrix and two opacities of composite resin (opaque and chromatic enamel). The width of the tooth and the cant of the midline were corrected and polished.
An achromatic enamel shell was built onto 2.1 using a putty matrix fabricated from a diagnostic waxup. This should be no greater than 0.3mm in section.
Dentin (opaque) composite was placed.
Then, chromatic, and achromatic enamels were placed in addition to some effects.
Finally, both teeth were polished to mimic natural enamel: the final image demonstrates great esthetic integration and good tissue health.
This concludes this series on midline diastema restoration using a direct resin approach. I hope you have found it informative and useful.
Jason Smithson, BDS (Lond), DipRestDentRCS (Eng), is a member of Spear Resident Faculty.