Today’s dentists need and want to perform adhesive bonding protocols more efficiently, and many dental product manufacturers have responded to the demand for simplicity by introducing new generations of bonding agents and cements.
However, selecting the ideal bonding and cementation materials can become challenging in light of various product claims regarding bond strengths. Additionally, bonding and cementation materials—regardless of their advertised predictability—still require adherence to their recommended, step-by-step procedures to avoid restoration failure due to marginal gap formation and subsequent secondary decay development. Deviating from recommended clinical techniques when definitively seating restorations—including improperly placing bonding agents and cement—can lead to failures, remakes, unhappy patients, and lost revenue.
When permanently seating indirect restorations, a variety of factors influence long-term treatment success, including the restorative material from which the restorations were fabricated, preparation design, isolation, and the selected cement or adhesive. Depending on the case, either conventional cementation or adhesive bonding techniques can be used.
Successful conventional cementation depends upon preparation design and resistance in order for restorations to predictably attach to underlying tooth structure. For adhesive bonding, a micromechanical connection between tooth structure and the restoration is necessary.
Considering the variety of both restorative materials and cements/adhesives, it can be challenging to determine which is ideal and what techniques to perform. Fortunately, dentists can rely on their DSG Laboratory for information about predictably placing the restorations they’ve treatment planned. After all, the long-term quality and durability of the restorations DSG fabricates depends upon correct placement protocols, and using the appropriate adhesive, cements, and procedures is critical.
For example, when the dentist is treatment planning all-ceramic restorations, preparation design will be important, particularly for high-strength ceramics. In general, DSG advises that for all-ceramic restorations, the finish lines should consist of shoulder preparations with rounded internal line angles, and sharp line-angles or edges should be avoided. Deep chamfer preparations are also possible. Additionally, preparations should also accommodate the minimum material thickness required for laboratories to fabricate the anticipated restorations.
When preparations are short and have an excessive taper, the restorations should be adhesively bonded using resin cement. Adhesive resin cements—whether light-cure only or dual cure—require meticulous isolation. If predictable isolation cannot be achieved, then conventional cements can be used, particularly for high-strength ceramic restorations. Adhesive resins also require preparations to be etched and rinsed, after which they can be conditioned with an adhesive bonding agent and cured.
Feldspathic, leucite-reinforced, glass-ceramic, and fluorapatite ceramic restorations must be seated with adhesive resin cements to ensure necessary support. Veneers and partial coverage restorations, which do not enable mechanical retention, should only be adhesively bonded.
Note that when adhesive resin cements are used, the intaglio surface of glass-ceramic restorations must first be etched and silanized. Ceramic etchants contribute to retentive bonding surfaces on all-ceramic restorations and improve bonding between the resin cement and ceramic bonding surface. Silanization then mediates the bond between adhesive resins and such indirect restorative materials as glass ceramics, metal, and composite. Once these two steps are completed, adhesive resin can be placed in the restoration, the restoration seated, and appropriate light-curing performed.
Incidentally, thoroughly and predictably light-curing adhesively placed restorations is affected by several factors. These include delivering sufficient light at the correct intensity, as well as for the recommended length of time.
When preparations are long and only have a minimal taper, then the indirect restorations can be conventionally cemented. Conventional cements attached restorations to preparations by creating a hardened layer between the restoration and tooth structure. Lithium disilicate, alumina, and zirconia-based high-strength ceramics have appropriate mechanical properties to withstand occlusal loads without requiring an adhesive. However, conventional cements are contraindicated for glass-ceramic restorations.