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ePaper created 2018-03-23, 09:55:06 | version 1.38.0
20 RESTORATIVE Dental Tribune Middle East & Africa Edition | 1/2018 New materials for a classic indication Cementation of all-ceramic restorations using Variolink Esthetic By Dr Eduardo Mahn and Dr Juan Pablo Sánchez, Chile Metal-based single crowns are nor- mally seated using a zinc phosphate cement. All-ceramic materials have led to a change in the luting material being used for this indication. Zinc phosphate cements are seen as classic luting materials for the ce- mentation of metal-ceramic crowns. Along with all-ceramic materials, glass-ionomer cements (GIC) and res- in-modified glass-ionomer cements (RMGIC) were introduced. Gener- ally, luting cements are expected to meet certain requirements: They should provide an optimum bond to the tooth structure and restoration material. They must not be soluble in water. They should be suitable for application in thin coatings and they should offer long-term stabil- ity. This is in contrast to the proper- ties of classic cements, which are water soluble and do not establish an adhesive bond to the enamel or dentin (zinc phosphate cements) or establish only a minimally adhesive bond and only to the dentin (GICs and RMGICs). Nonetheless, these cements show reasonable survival rates if used for the appropriate in- dication even if they involve certain limitations. Problem I: opacity The opacity of the luting material is a critical issue in all-ceramic crowns as well as ceramic inlays and onlays. Almost any colour can theoretically be reproduced with ceramics by ex- ploiting their natural translucent properties. Using an opaque luting material appears to be counterpro- ductive in achieving this. Further critical issues are the limitations involved in the anterior region and the location of the cement line in the visible area in inlays and onlays. For instance, if a tooth is restored with a veneer, the basic shade of the tooth is maintained. Only the enamel is replaced, usually by using a translu- cent ceramic that covers the natural dentin. In such a case, it is essential to use a translucent luting material to achieve a favourable result. comparatively Problem II: adhesion The low bond strength of conventional cements is also problematic. Classic prepara- tions around the tooth create a high degree of friction and retention. However, the retention is significant- ly reduced in partial crowns, veneers or onlays. It is therefore advisable to use a luting material that is capable of providing a strong adhesive bond. Both problems led to the widespread use of composite luting materials. Perhaps their only disadvantage is the removal of excess material. These luting materials are not wa- ter-soluble, hard and solid and they have a high adhesive strength, which makes excess removal difficult. Early luting composites were equipped with a self-cure mechanism. Users had to wait a few minutes until the composite was almost fully set be- fore they could remove the excess material. This period of time was risky because of the moisture in the mouth. Blood or saliva could come into contact with the non-polymer- ized composite and cause damage. Dual-curing luting composites These issues led to the rise of dual- Fig. 1: Preoperative situation Fig. 2: Situation after composite build-up (Tetric N-Ceram Bulk Fill) and preparation Fig. 3a and b: Crown design in the software suite (Cerec inLab) and try-in before crystallization firing (IPS e.max) Fig. 4: Characterized and glazed crown Fig. 5: Etching and silanating with Mono- bond Etch & Prime Fig. 6: Enamel etching prior to the application of the adhesive Fig. 7: Applying Variolink Esthetic DC into the crown Fig. 8: Placing the crown Fig. 10: Final curing. Excess luting mate- rial was removed beforehand (quarter technique) Fig. 11: Seated crown after excess removal curing composites for the cemen- tation of all-ceramic crowns. Dual- curing luting composites are usually delivered in double-push syringes with a mixing tip. During extrusion, the base and catalyst are automati- cally mixed. The material can be ap- plied directly. The main advantage is that the curing process can be ac- celerated with light and excess ma- terial can be easily removed. At the same time, the self-cure mechanism ensures a reliable cure, even with relatively thick or opaque ceramic layers. Nonetheless, there are some situations in which excess material cannot be removed all that easily be- cause the setting reaction takes place too quickly or the material does not cure down to the depth of the com- posite layer. After one second of light curing, the surface is set and excess can be broken off, but the material is still paste-like at the interface to the crown or tooth. State-of-the-art luting composites such as Variolink Esthetic contain the newly developed initiator Ivo- cerin. This photoinitiator needs fewer photons to initiate the setting reaction. Excess can be polymerized en bloc and pulled off as a “ring” in one go with no uncured material left in touch with the tooth or crown (see Fig. 9). In addition, the luting composite does not contain amine, which is another advantage. Amine may be implicated in a potential dis- colouration of the cement line over time. One material – five shades Variolink Esthetic is based on the Value Shade concept. The shades are classified according to the effect to be achieved with the cement. Five shades are available: Light+, Light, Neutral, Warm and Warm+. In this way, the shade spectrum ranges from an opaque white tone (Light+) to an opaque yellow brownish shade (Warm+). In between lie shades such as a coconut water white and a neu- tral tone (very translucent) and a warm tone (comparable to A3). In ad- dition, the luting composite is avail- able in an LC (light-curing) and a DC (dual-curing) version. The LC version is designed for relatively thin resto- rations such as inlays, onlays and ve- neers. The DC version is suitable for more extensive and opaque restora- tions. The luting composite is used in conjunction with the light-curing single-component Tetric® N-Bond Universal. Fig. 9: Excess removal is easily achieved due to the new technology based on the Ivocerin photoinitiator Clinical case A 45-year-old male patient presented to the practice with a restoration on tooth 46. The tooth had been endo- dontically treated and was tempo- rized with a filling (Fig. 1). The tem- porary was removed, the tooth built up with Tetric N-Ceram Bulk Fill and then prepared for the crown resto- ration (Fig. 2). An impression was taken with a one-step two-phase im- pression technique using putty and light-body silicone. After scanning the model, the crown was designed in the software suite (inLab, Dent- sply Sirona) and milled from an IPS e.max® lithium disilicate block (Fig. 3). After the crystallization firing the crown was stained and glazed (Fig. 4). The next step was to etch and si- lanate the ceramic crown with the new glass-ceramic primer Mono- bond® Etch & Prime. This primer combines a ceramic etching and silanating component in one single material and therefore eliminates the need for the ceramic to undergo hydrofluoric acid etching (Fig. 5). Af- ter the etching and silanating step, the crown was rinsed with water and dried. Then the isolated enamel was etched (Fig. 6). ÿPage 22