Combining elements of a layering composite system with a universal to simplify manufacturing of demanding anterior restorations

Case report

A 60-year-old female patient, with no relevant medical history, presented with a main complaint of an old restoration with a broken incisal edge on UL1 (Figure 2). No occlusal overloading was revealed by the functional analysis, and the cause of the restoration failure was considered to be ageing of the composite. However, the translucent area on the incisal edge of UR1 was a result of physiological wear of the palatal enamel and the tips of dentinal mamelons during protrusive function, which could also explain the failure of the existing restoration. The old restoration was well bonded to enamel despite the discolouration on the cervical area, which was a result of the slight overhang of the margin. Shade was compliant with the dental tissues, given that it was a single-shade restoration (Figures 3 and 4).

Before removing the old restoration, the broken part was repaired, and a key made of hard silicone putty (75 shore) was fabricated and modified while using rubber dam. Four incisors were isolated with rubber dam, and the old restoration was removed. Surface preparation for bonding included 29-μm particle air abrasion and acid-etching the enamel with 37% orthophosphoric acid for 30 seconds (Figure 5).

The shade distribution in this case was complex (Figure 6). A lighter area dominated the middle third (area inside the red dots), while darker areas were present at both the cervical and incisal regions. The area inside the black dots (Figure 6) was translucent and was replicated using a universal shade alone. To replicate the darker dentine areas, the dentine shade UD4 from Ena Plus HRi (Micerium SpA, Italy) was used, while UD2 from the same system was applied for lighter areas. Both composites were covered with Omnichroma (Tokuyama) as an enamel substitute, without the need for meticulous care in matching thickness. This approach helped to ensure proper optical blending of the natural tissues and the different composite shades. Cracks were reproduced with a scalpel after polishing.

Figure 7 shows a still image from the video of the procedure at the moment when the palatal shell, created using the silicone key, was transferred to the tooth to be restored. The composite on the key was Omnichroma (Tokuyama), a universal shade material, and the thickness of the palatal shell was much greater that the general guidelines for a layering technique. This makes manufacturing on the key, or directly intra-orally, much easier. It also increases the contact area with the palatal enamel, which means that is much easier to remove the silicone without damaging the composite, or without the palatal shell sticking to the silicone. Omnichroma (Tokuyama) appears whitish before polymerization, but after polymerization becomes transparent when no tissue walls are present, or it blends with cavity walls in closed cavities (Figure 8). When the silicone key was removed, the thickness of the material was notable; however, this eased and supported the following operation and handling of materials, and did not affect the appearance of the final restoration.

The proximal wall was built up with the aid of a matrix for anterior teeth (Tor VM 1388, Russia). A universal shade (Omnichroma, Tokuyama) was also used in this area to match the transitions between the different chromaticities of the dentine shades. The thickness of this wall can exceed the traditional 0.5-mm limit of the proximal wall thickness seen in classical stratification techniques (Figure 9).

Figure 10 shows the stratification of dentine shades. The different chromaticity of the two selected materials is clearly visible. The volume of this layer was determined roughly because the remaining thickness of the ‘enamel’ layer was not as important when using a universal shade rather than a highly translucent enamel shade. The universal composite was layered over the dentine shades, with the effect of blending already visible. Blending is more pronounced before polishing owing to light scattering in different directions. Polishing partially reveals the optical properties of the underlying dentine shades and creates a natural variation in colour (Figure 11).

Texture is equally important as shade since it determines how much light passes through the tooth and restoration versus how much light is scattered back to beholder's eye. It also defines the reflective surfaces that dictate the optical volume and shape of the tooth. One method to copy texture is by using articulating paper over the labial surfaces of both the natural tooth and the restoration. Then, using a pointed diamond bur (usually red or yellow coded), the necessary embrasures and shapes can be formed (Figure 12). After polishing and finishing, the natural cracks in the tooth can be copied using a #11 blade. These cracks initially appear as white lines owing to light scattering. Additional polishing with a brush and polishing paste smooths these lines, and over time, the lines resemble natural features, absorbing a small number of pigments and resembling the adjacent tooth (Figure 13).

Immediately after removing the rubber dam, the shade appears dissimilar to the adjacent natural tooth (Figure 14). This is due to dehydration. When hard tissues lose the liquid medium between the enamel prisms and collagen fibres, they appear less homogeneous optically. Light scatters more and the appearance becomes more opaque and consequently lighter in colour. Final shade matching should be assessed at a follow-up appointment, once rehydration restores the tooth's natural optical properties.

At 1-week post-operatively and after rehydration, the shade zones of the natural tooth reappeared. A difference in the shades of the cervical areas remained, but that area was unrestored. Incisal translucency was replicated to a satisfactory level (Figures 15–17).

The complete procedure required a time window of 80 minutes, significantly shorter, when compared to the time needed for the same results, but with enamel masses that needed to be controlled in thickness. Shade properties, mainly luminosity and translucency, which are thickness dependent in classical stratification, were unaltered from the lingual shell thickness, and surface texture could be easily manipulated.

Conclusions

All composite resins currently available on the market are methacrylic based, meaning different materials from different manufacturers can be co-polymerized and thus combined. Understanding the fundamentals of colour and the interaction of light with hard tissues and composites is essential for a dentist to achieve the best results in the shortest time necessary. The introduction of materials, such as universal composites, adds a valuable tool to a dentist's armamentarium. Additionally, materials that produce their optical properties structurally, rather than relying on pigments, may offer unique blending solutions that are highly efficient in terms of time and results.