Cementation Navigation: A guide to proper cementation protocols for different restoration types and clinical situations

Dentists today rely increasingly on their partners in the dental laboratory for information about how to predictably place today’s restorations. Laboratories therefore need a thorough understanding of not only the restorative material used in the fabrication of the dental restoration, but also the cementation options and protocols to provide dentists with specific details about the options available.

For example, depending on the case, laboratories can advise dentists to place restorations using either conventional cementation or adhesive bonding techniques.

Conventional cementation combines preparation design and resistance to attach restorations to underlying tooth structure. Adhesive bonding, on the other hand, produces a micromechanical retention and chemical bond between the tooth structure and the restoration.

Multiple factors influence cement selection. These include the restorative material, preparation design, necessary bond strengths, isolation capability and desired esthetic outcomes. This article provides laboratories with an overview of conventional and adhesive cement classifications suitable for reviewing with their dentist customers.

Cement Classifications

Adhesive resin cements: Adhesive resin cements-a category that includes self-cured universal resin cements, light- and dual-cure resin cements, and self-adhesive resin cements-are superior options for all-ceramic restorations. In general resin cements require tooth preparation to be etched with phosphoric acid, rinsed with water, dried and then conditioned with the adhesive bonding agent. With adhesive resin cements, internal aspects of all glass-ceramic restorations are etched following manufacturer’s instructions and silanized before seating, followed by adhesive cement application in the restoration and cured upon placement. This leads to maximum, high-level bond strengths.

Adhesive resin cements require meticulous isolation procedures. When good isolation cannot be ensured, conventional cements may be considered for cementation of high-strength ceramic restoration such as those constructed from lithium disilicate or oxide ceramics. Adhesive resin cements can be self-cure, dual-cure or light-cure.

Self-cured universal resin cements: Self-cured universal resin cements such as Ivoclar Vivadent’s Multilink Automix incorporate self-curing cement with a light-cure option for very high immediate and long-term bond strength values. Multilink Automix is used in combination with the self-etching and self-curing Primer A/B. While acting as a sealant for dentin, it also provides good marginal adaptation and high bond strength. Clinical trials have proven Multilink Automix’s long-term success and reduced post-operative sensitivity. It is suitable for the adhesive cementation of indirect restorations (inlays, onlays, crowns, bridges and root posts) made of metal, metal-ceramic, glass-ceramics, lithium disilicate, oxide ceramics and composite resins with enamel and dentin (Fig. A).

Light-cure and dual-cure resin cements: Variolink® Veneer, a light-cure esthetic resin cement from Ivoclar Vivadent, is amine free for long-term shade stability and has been developed for adhesive cementation of esthetic anterior restorations such as veneers. This microfilled, purely light-cured resin cement offers seven light-cured value shades to enhance the esthetics of the final restoration. The Medium Value (MV 0) is very translucent and has little effect on the final restoration. The High Values allow the clinician to brighten or increase the value and the Low Values provide a “warming” effect to the final restoration. It is indicated for cementing composite restorations and delicate ceramic restorations with thickness less than 2 mm (Fig. B).

The dual-cure version of this cement is Variolink II, a microhybrid cement available in 6 base shades and 2 catalyst shades as well as in 3 different degrees of viscosity. It demonstrates a high degree of radiopacity and is indicated for adhesive luting of ceramic and composite restorations such as inlays, onlays, metal free bridges and veneers made in lab or chairside (Fig. C). Variolink II is a dual-cure resin cement, however, it also may be applied in a light-curing technique only, such as for luting of veneers. For this purpose only Variolink II Base is to be used.

Self-adhesive resin cements: Self-adhesive resin cements demonstrate some of the advantages of resin cements and the convenience of conventional cements, including moderate level bond strengths. Self-adhesive cements are contraindicated for use with intermediate strength glass-ceramic restorations such as those constructed of IPS Empress or feldspathic ceramic.

Ivoclar Vivadent’s SpeedCEM is an example of a self-adhesive cement. It can be used with high-strength ceramics to help maximize clinical efficiency. A self-adhesive, self-curing composite luting cement, SpeedCEM can be optionally light cured and also offers easy, quick and universal application. It offers the additional advantages of a resin cement, such as intermediate bond strength and translucency, as well as lower water solubility. SpeedCEM consists of an adhesive monomer that enables stable chemical bonds to zirconium oxide metal restorations. Therefore, it is suitable for cementing indirect restorations made of metal, metal-ceramics, lithium disilicate, oxide ceramics and fiber-reinforced resin composites (Fig. D).

Conventional Cements: Conventional luting cements connect restorations and underlying tooth structure by creating a hardened, cement layer between the restoration and tooth. To ensure success, retentive tooth preparation design is essential to ensure retention when using conventional cements. Conventional cements are contraindicated for use with glass-ceramic restorations.

Surface Treatment

All glass-ceramic restorations are etched and silanized before adhesive cementation. However, silanization is not required for conventional cementation of IPS e.max lithium disilicate. A ceramic etching gel, such as IPS Ceramic Etching Gel from Ivoclar Vivadent, is used to produce retentive bonding surfaces on all-ceramic restorations and enhance the bonding effect between the luting composite and ceramic bonding surface.

For adhesive and self-adhesive cementation of IPS e.max lithium disilicate (LS2) restorations, as well as the adhesive cementation of IPS Empress, the restorations are silanized using Monobond Plus (Fig. E). Monobond Plus is a universal single-component restorative primer mediating an adhesive bond between the luting composite (e.g. from the Variolink and Multilink product lines) and all indirect restorative materials including glass and oxide ceramics, metal, zirconia, composites, and fiber-reinforced composites.

Material Based Requirements

Intermediate strength glass-ceramics (i.e., those with a high glassy content) obtain additional support from adhesive bonding and must be adhesively cemented using a resin cement. Therefore, feldspathic, leucite-reinforced and fluorapatite ceramic restorations should be cemented with adhesive resin cements.

High-strength ceramics such as lithium disilicate materials (IPS e.max CAD, IPS e.max Press), alumina, and zirconia-based ceramics demonstrate good mechanical properties and can withstand occlusal loads in the absence of an adhesive. Although conventional cementation is permissible for these ceramics, adhesive cementation offers multiple advantages and remains the material of choice for these restorations. In fact, high-strength ceramics can be placed using self-adhesive cementation techniques, thereby gaining good bond strength while also taking advantage of a simple cementation protocol.

Preparation Requirements

Preparation design is significant in cement selection for high-strength ceramics. Preparations lacking adequate mechanical retention such as short preparations of less than 4 mm, or preparations with taper in excess of 8° should be adhesively bonded using a resin cement. If preparations demonstrate adequate mechanical retention with a length greater than 4 mm and a minimal taper of less than 8°, restorations may be conventionally cemented. Because veneers and partial coverage restorations lack mechanical retention, they can only be adhesively bonded.

Generally, successful outcomes with all-ceramic restorations are only achieved when preparation guidelines are closely followed and account for minimum thickness requirements. According to basic preparation guidelines for all-ceramic restorations, sharp line-angles or edges should be avoided. Shoulder preparations with rounded internal line angles (modified shoulder) are the finish lines of choice. Deep chamfer preparations also are acceptable. Preparations should reflect at least the minimum thickness allowed for the material’s use.

Conclusion

The quality and durability of the restorations that laboratories fabricate is predicated on dentists using the correct placement protocols. Selecting the most appropriate adhesive and conventional cementation materials and techniques are critical in achieving successful results. The clinically proven Ivoclar Vivadent adhesive and conventional cementation materials have been thoroughly tried and tested for their respective indications. This article has outlined some key considerations related to restoration placement that laboratories can share with their customers.