Cementation Considerations.
Cementation is the last five minutes of a case that took weeks, and it is where a substantial share of restorative failures are determined.
Know what each cement class does
Zinc phosphate has the longest clinical record of any luting agent. It has no adhesion, relying entirely on the preparation's retention and resistance form, and it is technique-tolerant.
Glass ionomer and resin-modified glass ionomer bond chemically to tooth structure to a modest degree, release fluoride, and tolerate a slightly moist field. Resin-modified versions are stronger and less soluble than conventional glass ionomer, and they are a sensible default for retentive preparations under zirconia or metal.
Self-adhesive resin cements combine adequate strength with a simplified protocol. Adhesive resin cements, used with a separate bonding system, provide the highest bond strengths and are what a bonded lithium disilicate restoration needs to perform as designed — at the cost of the most demanding isolation and the most steps.
Match the cement to the situation
Two questions decide it: does the preparation provide retention and resistance form, and can the field be isolated properly?
A retentive preparation in a difficult field is well served by a resin-modified glass ionomer or a self-adhesive resin. A short, over-tapered preparation in a field you can isolate calls for adhesive cementation, because the bond is doing work the geometry cannot.
A short preparation in a field you cannot isolate is the difficult case, and the honest answer is usually to improve one of the two — additional retention features, or better isolation — rather than to hope a cement compensates.
Prepare the restoration surface correctly
This differs by material and the differences matter. Lithium disilicate is etched with hydrofluoric acid for the manufacturer's stated time, rinsed, dried and silanated. Zirconia is air-abraded with fine alumina and treated with a phosphate-monomer primer; hydrofluoric acid does essentially nothing to it.
Most laboratories deliver restorations with the fitting surface already prepared appropriately. What undoes it is try-in.
Saliva contact after surface treatment deposits proteins and phosphates that block the sites the primer or silane needs, and rinsing with water does not reliably remove them. A dedicated cleaning agent, or repeat air abrasion for zirconia, restores the surface. This single step is among the most commonly skipped and most consequential in the whole procedure.
Prepare the tooth surface too
The preparation carries provisional cement residue, biofilm and saliva proteins by the time the definitive restoration is being seated, and none of those improve adhesion.
Clean with pumice or an appropriate cleaning agent, rinse and dry. Where a provisional has been cemented with a eugenol-containing material, be aware that eugenol residue can interfere with resin polymerization — a eugenol-free provisional cement avoids the issue entirely where adhesive cementation is planned.
Desensitizing agents applied before cementation can also affect bonding depending on the product and the cement. Check compatibility rather than assuming.
Isolation is not optional for adhesive work
Adhesive cementation performs to specification in a dry field and unpredictably in a wet one. If rubber dam is achievable, it is the most reliable route; where it is not, retraction cord, isolation systems and careful assistance are the alternatives.
The decision worth making honestly is whether the field can be controlled at all. If it cannot, choosing a cement that tolerates moisture is a better outcome than performing an adhesive protocol badly.
This is a decision that ideally happens before the material is chosen, not at the cementation appointment.
Excess removal and timing
Removing excess cement at the correct moment is a technique in itself. Too early and the cement is still flowing and re-contaminates the margin; too late and set cement has to be cut away, risking the margin and the tissue.
Most resin cements pass through a rubbery stage where excess lifts cleanly, and a brief tack cure produces that stage predictably. Floss the interproximal areas before the cement sets fully, and check the margins circumferentially rather than only where they are visible.
Where a margin is subgingival, radiographic verification afterwards is worthwhile — retained subgingival cement is a well-documented cause of chronic inflammation.
Provisional cementation matters too
The provisional phase determines a good deal of what happens at the definitive appointment, and the cement used is part of it.
A provisional cemented too firmly is difficult to remove and risks damaging the preparation on removal. One cemented too loosely debonds, allows the tooth to move, permits ingress at the margin and irritates the tissue. Where adhesive cementation is planned for the definitive restoration, a eugenol-free provisional cement avoids interference with resin polymerization.
Removing all provisional cement residue before the definitive restoration is seated is not optional. Residue at the margin prevents complete seating and compromises the bond wherever it remains.
Torque, seating pressure and setting
A restoration should be seated with firm, sustained pressure rather than a series of pushes, and held while the cement reaches its initial set. Intermittent pressure allows partial rebound and traps cement, leaving the restoration marginally high in a way that is difficult to detect and difficult to correct.
Where a restoration is being seated on a preparation with limited escape paths for cement — a deep box, a close-fitting internal surface — vent the cement by applying it in a thin layer to the internal surfaces rather than filling the restoration.
After the initial set, verify seating before assessing occlusion. A restoration that has not seated completely will read as high, and adjusting it at that point makes the problem permanent.
Post-cementation sensitivity
Sensitivity after cementation has several possible causes and it is worth distinguishing between them rather than reassuring the patient by default.
Occlusal interference is the most common and the most easily addressed. Incomplete seating produces a high restoration with the same effect. Dentine desiccation during the procedure, cement acidity, and microleakage at an imperfect margin are the others.
Check the occlusion first, including excursions, and verify seating radiographically if there is any doubt. Sensitivity that persists beyond a few weeks with a verified occlusion and confirmed seating warrants investigation rather than observation.
In short
- Choose cement on retention form and isolation, not by habit
- Zirconia needs air abrasion and MDP primer; hydrofluoric acid does nothing to it
- Saliva contamination after try-in must be actively cleaned, not rinsed
- Eugenol provisional cement can interfere with resin polymerization
- Check occlusion and seating first when a patient reports sensitivity
More on clinical
Discuss a case
Where a case sits between options, a short conversation before preparation is usually quicker than resolving it afterwards.