Most dentists and technicians rely on the “chameleon effect” of translucent ceramic on composite to increase the predictability of achieving an esthetic outcome for posterior restorations. Because of the chameleon effect, the margins of the restoration can often seamlessly blend into the tooth and cannot be visually detected by the patient.
If there are esthetic problems with the prepared tooth structure, such as moderate to severe discoloration due to old amalgam restorations or secondary dentin formation which can be highly chromatic, those need to be masked out or it will negatively impact the value and/or color of the final restoration if it is made from a translucent material. The most common ingot used by dental technicians or block used by clinicians milling in their office is Ivoclar's e.max HT (high translucency) Press or CAD.
If the underlying tooth is of normal color and value, there will be no negative effect on the restorative outcome. Keep in mind, most restorations are being fabricated with a monolithic approach. Only minor amounts of surface stain (characterization) are being applied to achieve the best esthetic blend to the adjacent teeth. The current trend is using an ingot or block of medium translucency (MT). This slight increase in opacity can help in maintaining an esthetic outcome with varying thicknesses of the ceramic, as well as masking slight color problems.
If there is discoloration of the prepared tooth (most often the pulpal floor of a posterior tooth), the discoloration will have a negative impact on the translucent ceramic. Often the restoration will appear low value or darker than desired because the discoloration of the secondary dentin shows through the translucent restorative material. If you are relying on the chameleon affect to have the restoration ‘blend’ into remaining tooth structure, the discoloration must be masked with an opacified layer such as a base or liner.
The material I currently use is Tokyoma Estolite Color Low Chrome Opaque. It is a 56 percent filled flowable composite which is bonded to the discolored area on the pulpal floor of the tooth. If you are having a laboratory fabricate the restoration, photographs should be taken of the tooth once the tooth is modified with the opacified layer of composite. Occlusal and buccal views are recommended.
The best shade guide match from both the Vita Classical and the 3D Master shade guides should be photographed in the same image. The dental technician can then interpret what they see and decide on the most appropriate translucency of ceramic. It is not necessary for clinicians who mill in their office to take the photograph; however, they must go through the same thought process as the technician. This step is extremely critical because it determines the esthetic outcome, and I recommend that the restoration be fabricated with a monolithic technique to achieve the highest strength of the restoration.
When an opaque core is used like metal, high strength zirconia or e.max MO (medium opacity) or HO (high opacity), if the restoration is fabricated with a layering technique. The ceramist can place an opacified layer deep in the restoration, allowing space for dentin and enamel ceramic to be layered over it. This develops a translucent outcome. In this case, there is no need to alter the tooth with masking resins.
If your final restorations do not satisfy you or your patient's esthetic expectations because they are too ”dark,” consider modifications of the preparation before the restoration is fabricated!