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Establishing a Bonding Protocol
A system for successful indirect restorations
Over the past 15 years, there have been sweeping paradigm shifts regarding indirect substrates, bonding agents, and luting cements. Clinicians are not simply cementing gold or porcelain-fused-to-metal crowns anymore. They face challenges in bonding two new “all ceramic” substrates taking over the crown and bridge markets: zirconia and lithium disilicate.
Priming the surface of a lithium disilicate or zirconia crown creates a hydrophobic, low energy, resin-loving surface. This primed surface encourages long-lasting covalent bonds between the crown, luting cement, and the tooth. An initial mechanical bond will form without priming; however, durable chemical bonds are created by priming.1,2
Lithium disilicate’s surface requires hydrofluoric acid etching to create micromechanical retention, after which priming with a proper chemical silane leads to long-term durability.
Zirconia, by contrast, is unetchable and requires a unique zirconia primer such as Z-PRIME™ Plus. It is important for the clinician to understand how their laboratory prepares these different substrates so the office team has a bonding protocol upon receiving cases. Protocol is equally important when re-cementing a de-bonded all-ceramic substrate.
No longer must clinicians worry about proportions and timing of placement for the chemistry of bonding agents to work. Today bonding has progressed to one-bottle universal systems that are predictable and can deliver excellent bond strengths.
Previous one-bottle bonding agents could be incompatible with the dual-cure or self-cure luting cement or build-up material and leave an uncured acidic monomer on the interface of the bonding agent and luting cement. This uncured acidic monomer could render the material unable to properly cure, resulting in disastrous consequences.
A compatible universal, one bottle, bonding agent such as BISCO’s ALL-BOND UNIVERSAL® can work with direct and indirect restorative solutions. A true universal bonding agent can also be used as a priming agent for zirconia and lithium disilicate substrates, further simplifying the bonding protocol. However, lithium disilicates should be primed with a pure silane agent before a bonding agent is placed for improved durable bonds.
Luting systems can be dual-cure, light-cure, self-cure, or self-adhesive. When selecting a luting agent, a good rule of thumb is to evaluate the retentiveness of the preparation or the ratio of the preparation height to the preparation convergence. Fully retentive crowns can be bonded with self-adhesive resin cements, dual-cure or self-cure luting cement, or nonadhesive cements. Short, tapered, non-retentive preps, on the other hand, should only be bonded in place using a dual-cure cement such as DUO-LINK UNIVERSAL™ or a self-cure luting cement.
A predictable and reliable chairside protocol for zirconia and lithium disilicate restorations is a necessity today. Whether clinicians mill indirect restorations themselves, receive them from a laboratory, or re-bond these restorations when failure occurs, a thorough understanding of the bonding mechanisms facilitates a predictable and successful long-term outcome.
1. Chen L, Suh BI, Brown D, Chen X. Bonding of primed zirconia ceramics: evidence of chemical bonding and improved bond strengths. Am J Dent. 2012;25(2):103-108.
2. Kim BK, Bae HE, Shim JS, Lee KW. The influence of ceramic surface treatments on the tensile bond strength of composite resin to all-ceramic coping materials. J Prosthet Dent. 2005;94(4):357-362.
• DUO-LINK UNIVERSAL luting cement is the ultimate combination product for all indirect restorations
• ALL-BOND UNIVERSAL effectively bonds zirconia and lithium disilicate
• Z-PRIME Plus primes unetchable zirconia for more effective bonding
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About the Author
Sam Simos, DDS, is in private practice in Bolingbrook and Ottawa, Illinois.