We often get this question from dentists looking for confirmation on proper cementation techniques. While this isn’t typically a lab responsibility, it’s still useful to have the right information.
As is well known the cementation technique varies depending on the material being used and directly affects the final strength and longevity of the restoration. It’s essential to apply both micromechanical retention (sandblasting) and chemical retention (via specific molecules that bond surfaces together), while strictly following the protocol for preparing each surface.
Adhesive cementation is recommended in the following cases:
- Abutments that are less than 3 mm in height
- Abutments that are overly conical or tapered
- Anterior teeth, due to torsional forces during protrusion and lateral movements
- Abutments with crowns for removable partial dentures, as the clasps place traction on the crown
Maryland bridges - Fully ceramic restorations (ceramic veneers, ceramic inlays, lithium disilicate crowns, zirconia crowns)
Only surfaces that need sandblasting should be treated as follows:
Micromechanical retention treatment is done by sandblasting with 50-micron aluminum oxide for the following materials: feldspathic porcelain, monolithic or ceramic-coated lithium disilicate, monolithic or ceramic-coated zirconia, hybrid resins, and lithium silicate with zirconia filler.
Cementation protocol for metal-ceramic restorations:
- Sandblasting with 50-micron aluminum oxide
- Conventional cementation with glass ionomer or zinc phosphate cement
Cementation protocol for feldspathic porcelain:
- Sandblasting with 50-micron aluminum oxide
- Etching with 9.6% hydrofluoric acid for 2 minutes (over-etching weakens adhesive strength and ceramic flexural strength)
- Silane application: Chemical retention in feldspathic ceramics is achieved by silane molecules reacting with water, forming silanol groups that bond with the silica in feldspathic porcelain, creating a siloxane network
- Bonding application: The methacrylate group in silanes reacts with the methacrylate groups in adhesive resins
- Resin cement application and light curing
Cementation protocol for lithium disilicate:
- Etching with 5% hydrofluoric acid for 20 seconds
- Silane application
- Resin cement application and light curing
Cementation protocol for lithium silicate reinforced with zirconium oxide:
- Etching with 5% hydrofluoric acid for 20 seconds
- Silane application
- Resin cement application and light curing
Cementation protocol for hybrid resins:
- Etching with 5% hydrofluoric acid for 60 seconds
- Silane application
- Resin cement application and light curing
Cementation protocol for zirconia:
- Application of zirconia oxide primer
- Silane application
- Bonding application