Cementation vs bonding

Zirconia lute, MDP resin, and why saliva on an intaglio is a recement.

Objectives

Choose RMGI vs MDP-resin vs adhesive bond from the ceramic.
Name the step that undoes a saliva-contaminated zirconia try-in.
Explain why silane is for glass and MDP is for zirconia.

This lesson’s protocol

Zirconia is a polycrystalline ceramic. It does not etch with HF. You either lute it (RMGI) or bond it with an MDP primer and resin. Saliva phosphates poison the surface — that is the remake nobody wants.

Zirconia lutes or takes MDP resin. Glass is the adhesive-bonding lesson. Do not silane this crown.

Step 1 · Try-in, dry

Try-in, dry

In the mouth

Seat with finger pressure. Check proximal contacts, margin, and occlusion. Do not grind on a contaminated zirconia intaglio if you still intend to bond.

From the lab

Contacts were set in CAD and verified on the model. If a contact is bulletproof in the mouth, send it back — do not sandpaper the contact into an open.

Why it exists

A crown that only seats after you lean on it is an undercut or a heavy contact. Cement will not hide that.

Read this

The joint is half the restoration

CAD can be perfect and the crown still comes off in a week. Phosphate from saliva on zirconia, eugenol from a temp, a wet finish line, or HF on the wrong ceramic — those are seating errors, not mill errors. D2 students who only know ‘put cement in it’ will learn this from remakes.

Lute vs bond

A lute (zinc phosphate, RMGI) fills a gap and needs retention form. A bond (HF + silane + resin, or MDP on zirconia) is chemistry. Lithium disilicate wants to be bonded. Zirconia can go either way. Metal still lutes. Do not silane zirconia and do not HF it.

Try-in poisons the surface

The mouth coats a zirconia intaglio in phosphate. Clean it (Ivoclean, NaOH, or a light alumina blast) before primer or resin. Phosphoric acid is not a cleaner here — it makes the phosphate worse.

Open the practice lab

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