How to: Control color stability with ultra-thin porcelain veneers

Creating long-lasting, vital restorations while minimizing tooth preparation is the primary objective in modern cosmetic dentistry. Clinicians and patients continue to be concerned with the reduction required for some ceramic systems, and this has led to the evolution of “ultra-thin” ceramics options. These new systems impart both beauty and strength and often permit “no-prep” and “low-prep” veneering options. Numerous advantages are inherent in using ultra-thin ceramics, including the ability to remain in enamel to ensure maximum bond strength while allowing the natural vitality of the underlying tooth to permeate the restoration.

Cement selection

Compared with thicker, more opacious ceramic systems, ultra-thin ceramics can be influenced by the underlying tooth color as well as the color of resin cement. When cementing ultra-thin ceramics, the physical stability and optical qualities of the final resin cement system chosen are tantamount. Light-cure-only veneer cements have proven to be the best option for cementing ultra-thin veneers because unlike their dual-cure counterparts, they do not use a redox initiating system as part of their polymerization mechanism.¹ Most self-curing and dual-curing (light- and self-cure) resins depend on a benzoyl peroxide reaction with aromatic tertiary amines as a coinitiator and produce a tetraammonium salt as a byproduct.  This salt typically degrades with time and visibly changes from an invisible compound to a more yellow/orange substance. This color shift of the dual-cure resin cement can cause ultra-thin veneers to negatively change color over time, and therefore these systems are discouraged for use.²

Imperative qualities of resin cement systems used for cementation of veneers include the necessity for the try-in gels to optically match the light-cured resin cement in each shade class, an intuitive nomenclature for each shade and the need for a truly “clear” translucent resin cement. Other desirable qualities in a resin cement system used for luting veneers are a medium to high viscosity to facilitate placement and clean up using the “wave” technique for light curing, and the appropriate physical properties required to provide a long-lasting bond to the tooth substrate.

Mojo working

Mojo Veneer Cement, a veneer luting resin from Pentron Clinical Technologies, incorporates all the requirements for even the most demanding ultra-thin veneer cases and for any type of veneer case where full light penetration is expected. Mojo comes in four simple and highly intuitive shades: Clear, Light, Dark and Movie Star White. Each shade comes with a try-in gel that matches the final, light-cured shade of the corresponding resin cement to ensure there will be no surprises with the final appearance of each restoration.

Each shade class of Mojo Cement permits the alteration of the final color of the veneer for various scenarios. If the restoration is too dark, the Light Shade can be used to brighten or warm the color of the restoration. If the restoration is light, the Dark Shade can be used to darken or cool the cured appearance of the restoration. Mojo “Movie Star White” is an absolute essential for clinicians treating single teeth or full cosmetic cases where the patient has bleached his or her natural teeth, demanding a “whiter than white” final color. The clear offers a truly transparent shade that allows light to pass through the veneer and cement, creating a life-like, vital restoration that mimics the natural light progression found in the healthy, non-restored dentition.

Case presentation

A 16-year-old patient presents after four years of orthodontic therapy to correct malocclusion and align the anterior maxillary incisors. Ultra-thin porcelain veneers on tooth Nos. 5–12 are planned to correct a severe Bolton discrepancy that prevented diastema closure via traditional orthodontics.

01. Without anesthesia, tooth Nos. 6–11 were recontoured to remove undercuts and facilitate porcelain margins on the mesial and distal line angles to ensure proper diastema closure. No preparation was used for tooth Nos. 5 and 12. Fig. 1 shows the minimally invasive preparations.

02. Impressions were taken with DENTSPLY Caulk’s Aquasil polyvinyl siloxane impression material and a clear Essix Retainer was used for temporization to stabilize the teeth while fabricating the restorations. Eight Ivoclar Vivadent IPS e.max ultra-thin veneers (ivoclarvivadent.com) were fabricated by the laboratory. Each restoration ranged in thickness from 0.3 – 0.5 mm. (Fig. 2).

03. Without anesthesia, the Essix retainer was removed and the restorations were filled with the Mojo Light Try-In Gel (Fig. 3). The restorations were seated on each tooth and the color assessed (Fig. 4).

04. The appropriate bonding sequence was initiated. The teeth were cleaned with a fluoride-free pumice, etched for 15 seconds with phosphoric acid and thoroughly rinsed. In this case, no dentin was exposed so the etched enamel was desiccated to reveal an ideal frosty etch pattern. Fresh silane (included in the Mojo Kit) was applied to the previously hydrofluoric acid-etched internal veneer surface, evaporated and allowed to stand for 60 seconds.

05. Pentron’s Bond 1 Adhesive was applied to the restoration and air-thinned. Simultaneously, the adhesive was applied to the teeth and air-thinned to ensure a low film thickness and to volatilize the solvents. The adhesive on the teeth was then light cured for 10 seconds per tooth surface (Fig. 5).

06. The corresponding Mojo Resin Cement (Shade Light) was injected into the veneers using the plastic applicator tip (Fig. 6).

07. Each restoration was fully seated and checked for marginal adaptation with an explorer (Fig. 7). 

08. The “wave-technique” for initial polymerization was used, whereby the undisturbed residual excess was briefly initiated by waving an LED curing light over the margins. Once polymerization had begun, the firm but not fully hardened residual excess was removed with floss and sickle scaler (Figs. 8 and 9).

09. Once all of the residual cement was removed, each tooth was additionally light cured for 20 seconds per surface to ensure complete photo-polymerization of the Mojo Resin Cement.

10. Fig. 10 shows the one week final appearance of the eight ultra-thin veneers placed. Note the lack of color variation from try-in, to resin cement placement and the one week appearance. The restorations appear vital and esthetic because of the semi-translucent light conduction of the Mojo Light Resin cement. Both the clinician and the patient were very pleased with the result. 

Closing thought

With the popularity of ultra-thin veneers on the rise, clinicians recognize the important role of the resin cement systems. By using a veneer resin cement such as Mojo Veneer Cement, dentists are able to place veneers with a reliable, color-stable system that ensures excellent physical properties, easy handling and clean-up, as well as try-in gels that match the final polymerized shade of the resin. These properties relieve guess-work and facilitate exquisite results no matter how complicated the veneer case may be.