Achieving Natural Aesthetics in Class IV Restorations

INTRODUCTION
Recognizing the unique biological architecture of the natural tooth, dentists today practice conservative procedures and minimally invasive techniques in order to preserve the maximum amount of healthy structure when restoring dentition to proper form and function.¹ This can prove challenging when combined with patient expectations for an aesthetically pleasing smile and the predilection toward biomodification and biomimetics in modern dentistry.^2-4 Additionally, visual ergonomics is of optimal importance when restoring the anterior segment of patients presenting with Class IV fractures that have been previously restored.⁵

Before Image. Preoperative view of the patient’s natural smile.	After Image. Postoperative view of the nanohybrid restorations on teeth Nos. 8 and 9. Note the lifelike aesthetics, translucency, and shade characteristics created with only 2 nanohybrid composite resin shades.

In the past, recreating the unique characteristics of natural dentition could be difficult and confusing. Manufacturers released multiple composite shades, opacities, and translucencies, all of which were required to reconstruct individualized teeth. Therefore, the direct composite placement technique became overwhelming and time consuming. Fortunately, dental material manufacturers have helped to improve and enhance dental treatments by developing direct composites that simplify the layering process. Today’s biomimetic direct composite materials reduce the amount of composite colors required to recreate aesthetic restorations and simplify and enhance predictability. These new composites address demands for minimally invasive treatments while providing increased strength and optical characteristics, universal application, improved adhesion, and optimal handling and sculptability when reconstructing the biological, aesthetic, and physical architecture of natural teeth.⁶
Among the new alternatives available are nanohybrid composite resins indicated for Class I to Class V restorations. These newly developed universal nanohybrid restoratives display greater wear resistance, enhanced color stability, long-lasting polish retention, natural dentition-like flexural strength, and low shrinkage. Although emulating natural tooth structure, shape, and shade while blending with surrounding dentition still requires careful composite selection and artful procedures during placement protocol, these new nanohybrid composite resins also enable simplified techniques.
This article describes how a nanohybrid composite resin was used to re-restore old and discolored Class IV composite restorations on teeth Nos. 8 and 9 with a predictable 2 composite layering technique.

CASE PRESENTATION
Diagnosis and Treatment Planning
A 48-year-old woman presented with 15-year-old composite resin restorations on her anterior maxillary teeth (Before Image and Figure 1). The patient was not interested in porcelain veneers or any unnecessary removal of tooth structure. She requested only reversible and repairable restorations.

Figure 1. Close-up preoperative view of teeth Nos. 8 and 9.	Figure 2. Two shades of the nanohybrid composite resin (GrandioSO [VOCO America]) chosen for use in this case were previewed.
Figure 3. Shades A1 and A2 would be used.	Figure 4. A model was created from preoperative impressions.
Figure 5. An enhanced wax-up model demonstrated anticipated treatment outcomes.	Figure 6. A putty stent was created from the enhanced model.

Before the preexisting composite restorations were removed, the patient’s occlusion was analyzed. A comprehensive intraoral examination was performed that included an oral history, radiographs, and photographs. The patient was in good health, and nothing contraindicated direct composite rerestoration of teeth Nos. 8 and 9.
Morphologic, histologic, and optical characteristics of the teeth were examined. To select the appropriate composite shade for replacing the old restorations, nanohybrid composite materials (GrandioSO [VOCO America]) in shades A1 and A2 were previewed side by side on teeth Nos. 8 and 9. This enabled the dentist to select the appropriate shades for the case (Figures 2 and 3), with shade A2 being the lingual enamel layer and shade A1 as the final composite layer.

Preparation Protocol
Before the original composite restorations were removed, a diagnostically enhanced model was created from preoperative impressions (Figures 4 and 5). This model also would be used for fabricating a high viscosity putty stent (Registrado x-tra [VOCO America]) that, when placed intraorally, would provide a spatial reference and volumetric guide for composite placement (Figures 6 and 7). This stent also would help maintain the facial/lingual line angles.⁷
The old restorations were removed (Figure 8), and teeth Nos. 8 and 9 were prepared using diamond burs. In addition, a 2.5 mm infinite facial bevel was created (Figure 9) (888.31.012 [Brasseler USA]). Combined, this preparation design supported the fracture resistance and durability needed for the restorations and facilitated imperceptible restorative margins.⁸
The Class IV preparations were then verified incisally, after which the teeth were pumiced, rinsed, and dried. The preparations were etched with 35% orthophosphoric acid (VOCOcid [VOCO America]) for 15 seconds, rinsed, and dried (Figure 10). Then, a single-dose bonding agent (Futurabond DC [VOCO America]) was applied onto the preparations using a brush for 20 seconds (Figure 11). The selected bonding agent eliminated evaporation, would not spill, and required fewer steps, thereby helping to reduce technique sensitivity. The bonding agent was air-thinned with high pressure and light-cured for 10 seconds per tooth.
Although manufacturers have developed newer generations of self-etching adhesives that demonstrate predictable long-term bonding and marginal integrity, selective enamel etching is still advocated in the literature to ensure excellent clinical results.^9-12 Enamel bonding has been shown more effective when phosphoric acid etching is performed selectively on enamel.^9-12
The putty stent was placed intraorally (Figure 12), and GrandioSO composite in shade A2 was applied in a 1.5-mm thick increment to form the lingual enamel layer and block any show-through on tooth No. 9 (Figure 13). This layer was cured for 10 seconds (note that darker shades require 20 seconds). In order to assess this lingual enamel layer, the putty stent was removed. To simulate higher value and lower chroma in the middle and incisal thirds of the maxillary central incisor, the putty stent again was placed intraorally, and the A1 composite shade was placed, sculpted, and cured for 20 seconds (Figure 14).
To re-restore tooth No. 8, shade A2 composite was placed, sculpted, and cured for 10 seconds (Figure 15). The final A1 material was applied to the anterior tooth, sculpted, and light-cured (Figure 16). Once the restorations were successfully layered with the 2 composite shades (Figure 17), the putty stent was used to verify length and width of the restorations (Figure 18).

Figure 7. The stent would be used to help maintain facial/lingual line angles.	Figure 8. The existing restorations were removed and preparation initiated.
Figure 9. View of the final bevel preparation.	Figure 10. The teeth were etched using 35% orthophosphoric acid etch (VOCOcid, [VOCO America]).
Figure 11. A single dose adhesive bonding agent (Futurabond DC [VOCO America]) was applied to the preparations using a brush.	Figure 12. The putty stent was placed intraorally to verify reduction and for use during composite placement.
Figure 13. Shade A2 was placed to create the lingual enamel layer of tooth No. 9.	Figure 14. Shade A1 was placed as the second layer to complete the restoration buildup for tooth No. 9.
Figure 15. To re-restore tooth No. 8, shade A2 composite was placed, sculpted, and cured for 20 seconds.	Figure 16. The final A1 shade of composite was applied to tooth No. 8, sculpted, and light-cured.
Figure 17. View of teeth Nos. 8 and 9 immediately following final placement of the nanohybrid composite material.	Figure 18. The putty stent was placed intraorally to verify the length and width of the restorations.
Figure 19. A disc (Sof-Lex Extra-Thin Contouring and Polishing Discs [3M ESPE]) was used to impart the mesial transitional line angle.	Figure 20. A polishing cup (Dimanto [VOCO America]) was used.
Figure 21. Then a polishing brush (Easygloss [VOCO America]) was used.	Figure 22. Finally, a polishing point (Dimanto) was used.

Figure 23. Postoperative close-up view of the completed restorations on teeth Nos. 8 and 9.

The restorations were then finished using a series of discs (Figure 19) and contour, shape, and shine cups and points.¹³ These helped to ensure that the restorations demonstrated a similar harmony and balance with the adjacent teeth, as well as with each other. These finishing steps also imparted realism by better defining line angles (eg, mesial transitional line angle). In order to create a natural-looking final luster, a one-step polishing system that, according to the manufacturer, can withstand the high surface hardness of new composite materials while providing a long-lasting, high-gloss sheen in a limited amount of time (Dimanto [VOCO America]), was used (Figures 20 to 22). The final results demonstrating the imperceptible restorations are shown in Figures 23 and After Image.

DISCUSSION
The nanohybrid composite resin (GrandioSO) chosen for use in this particular case includes 30% to 50% less resin compared to other microhybrid resin-based restoratives.¹⁴ As opposed to glass particles between 400 and 5,000 nm found in conventional composites,¹⁵ this composite resin contains very small designer nanoparticles made from dioxide filler particles grown to 20 to 40 nm, then covered with a special coating.¹⁴ Glass ceramic fillers with an average particle size of one μm combined with the designer nanoparticles create a nanohybrid composite which outperforms conventional composites that have limited use.¹⁶
The rate of polymerization shrinkage in the newest, modern generation composites reaches 2% to 2.5% when curing.15 However, the low resin content construction of this material decreases shrinkage to 1.6%, reducing stress and, as a result, eliminates the undesirable “white line” that often appears with resin-based composites during the finishing process.¹⁶
Although scientifically difficult to attain, this material has an unusually high surface hardness resulting from the increase in filler load. Conventional composite filler weights range from 70% to 77% compared to this nanohybird composite at 89%.14 In the past, such highly filled composites contained very large sized macroparticles which were snagged during polishing and caused the gloss to dull. The highest alternative composite (100 micro vickers hardness [MVH]) has proven, over time, to wear faster than tooth enamel and display surface roughness and a dull appearance.¹⁶ Due to its unusually high surface hardness (210, 9 MHV),17 this nanohybrid composite is very comparable to natural enamel (350 to 450 MVH);9 and maintains its strength, is highly polishable, and demonstrates long-term abrasion and wear resistance (18 μm, ACTA with 200,000 cycles).¹⁷
In addition, other desirable characteristics of this nanohybrid composite are high compressive and flexural strengths (439 MPa and 187 MPa, respectively) resulting in excellent wear resistance and durability.¹⁷ It requires no sculpting resin and its increased sculptability and handling, coupled with its nonsticky texture, make it easy to use. In addition, this material will retain surface smoothness and a permanently polished sheen.

CONCLUSION
Manufacturers are increasingly providing clinicians with the integrated and complementary restorative tools they need to provide aesthetic dentistry that is also minimally invasive, durable, and predictably easier to perform. As our goal is to do no harm, conservative and minimally invasive techniques are of primary importance and should be considered above all others.
The case presented here has demonstrated a technique using only 2 shades of a nanohybrid composite resin, as opposed to 3 or more, to create lifelike anterior Class IV restorations. This latest generation of composites contributes to our goal to provide less technique-sensitive treatment in biomimetic, conservative, and effective ways.

References

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Dr. Milnar is a graduate of the University of Minnesota School of Dentistry. He is an accredited member of the American Academy of Cosmetic Dentistry and a board examiner for accreditation. Dr. Milnar maintains a full-time practice in St. Paul, Minn, emphasizing appearance related dentistry. He has published numerous articles about the direct placement of composites, shade selection, and porcelain materials. Dr. Milnar is cofounder of the Minnesota Academy of Cosmetic Dentistry and lectures extensively within the US Armed forces, as well as internationally, on the subject of direct composite restorations, shade selection, and porcelain materials. He has been voted “Top Dentist” for the last several years in the Minneapolis/St. Paul Magazine. He can be reached at frank@milnardds.com.

Disclosure: Dr. Milnar received financial support from VOCO America for writing this article.