Selecting Cement for Prosthetic Work – Adhesion vs. Conventional

The lab technician sends a crown—sometimes without cement information. The dentist chooses what they always use. The restoration then needs to be sent back.

The problem is that cement selection is not a formality after preparation is complete. It is a decision that impacts the marginal seal, durability, and predictability of the restoration for years to come. For silicate ceramics (e.max, feldspar), adhesive cementation is not an option but a prerequisite for survival. For zirconia, it depends on the actual retention.

Material Properties Determine the Cement, Not Vice Versa

Incorrect approach: Choose the cement, then look for a material compatible with it.

Correct approach: Understand the mechanical properties of the material (strength, elasticity) and derive which cement will ensure sufficient bonding from that.

Silicate Ceramics (e.max CAD/Press, feldspar, Empress):

• Strength: 360–530 MPa
• Brittleness: High (lack of plasticity)
• Adhesion to dentin: Poor without chemical pre-treatment

Hydrofluoric acid (HF) etching creates surface porosity. Silane acts as a functional chemical bridge between the glass and resin. The resin cement flows into the polarized surface and infiltrates the porous network. This provides true adhesion, which dentin alone cannot achieve.

Without this protocol, the restoration is prone to debonding under load or fracture in the area of residual cement.

Zirconia (monolithic, hybrid-zirconia, HT zirconia):

• Strength: 800–1000+ MPa
• Stiffness: High, minimal elasticity
• Adhesion: Both adhesive and mechanical retention are possible

For zirconia with good custom abutment dimensions (≥7 mm) and taper (≤6°), conventional cement is sufficient. Mechanical interlock in the microporosity is adequate. Adhesion is not a sine qua non condition here.

However, if the custom abutment is short (≤5 mm) or the taper is large, adhesion becomes a substitute for retention. In this case, an MDP (monophosphate) primer creates a durable chemical bond with zirconia and resin.

Adhesive Cementation – Mandatory for Brittle Materials

Silicate Ceramics (e.max, feldspar, ceramic onlays):

Mandatory protocol:

1. HF etching: 20–60 seconds (depends on glass thickness)
2. Rinse and dry
3. Silane primer (e.g., Espe Silane, Ivoclar silanizer): 1 minute
4. Dual-cure cement: Variolink Esthetic, RelyX Ultimate, Panavia V5
5. Absolute isolation (rubber dam) – reduces saliva access, improves polymerization
6. Light curing: 40–60 seconds (depends on cement and thickness)

Consequence of error: Omitting HF or silanization results in poor adhesion. Under masticatory loads, micro-movements begin. The cycle of thermal contraction-expansion expands the gaps. Bacteria penetrate deeper – leading to secondary caries at the margin.

Ceramic onlays and inlays: Exactly the same principles. The ceramic surface must be etched and silanized.

Maryland adhesive bridges (zirconia): Adhesive cementation only. The zirconia wing requires an MDP primer – it creates a chemical bond.

Ceramic endocrowns: Like e.max – adhesion is mandatory.

Conventional Cementation – When it's Sufficient

Monolithic zirconia with adequate retention:

• Custom abutment ≥7 mm
• Wall taper ≤6°
• Mechanical interlock is sufficient

Conventional cement: GIC (Glass Ionomer Cement), RMGI (Resin-Modified GIC), or a mixture. Adhesion is not required here – mechanical retention is at play.

Zirconia with poor geometry (short custom abutment, taper >8°): Adhesion takes over the role of mechanical retention. MDP primer + dual-cure resin cement.

Metal and porcelain-fused-to-metal (PFM): The strength of metal restorations does not depend on the cement – metal is hard and rigid. Conventional cement or RMGI.

Temporary prostheses (PMMA): Temporary cementation: Temp-Bond, Protemp, or regular zinc oxide eugenol. The restoration should be easy to remove without damage.

Comparison: Material vs. Cement vs. Indication

Errors in Cement Selection – and their Consequences

Error 1: Cementing e.max with conventional cement. Consequence: You send the restoration to the patient without a true bond. Masticatory forces cause micro-movements. The gap between the ceramic and the tooth becomes a harbor for bacteria. Within 6–18 months – secondary caries or debonding. The patient returns: "It fell off."

Error 2: Omitting silanization for e.max. Consequence: Silane primer is the chemical bridge. Without it, adhesion to HF-etched ceramic is poor. The restoration will debond.

Error 3: Cementing zirconia with poor retention using conventional cement. Consequence: A short custom abutment (<5 mm) or large taper (>8°) means mechanical interlock is insufficient. Conventional cement does not chemically bond to zirconia. The restoration is prone to debonding.

Error 4: No rubber dam for adhesive cement. Consequence: Saliva and moisture enter the gap. Cementation does not proceed correctly. Weaker bond.