Temporary cements: eugenol is comfortable for the patient and harmful to the definitive bond

A temporary cement must hold well enough not to come loose and loosely enough to permit removal without damage. It is a balance, and most problems arise from choosing one extreme.

The fundamental distinction is between cements with and without eugenol. Eugenol has a sedative effect on the pulp documented for over a century, and on a freshly prepared vital abutment it appreciably reduces sensitivity.

The difficulty is that eugenol inhibits polymerisation of resin materials. Residues remain in the dentine even after mechanical cleaning, and those residues interfere with the adhesive applied weeks later.

The rule that follows is clear: if the definitive restoration will be adhesively cemented — glass ceramics, veneers, inlays — the provisional must contain no eugenol. The benefit in sensitivity does not offset the loss of adhesion.

If instead definitive cementation will be conventional or self-adhesive on a retentive preparation, eugenol is acceptable and the patient benefits from it.

Eugenol-free zinc oxide cements retain much of the mechanical properties without the interference. They are now the default choice in most cases, precisely because they do not force an early decision.

Resin temporary cements offer higher retention and suit long-term provisionals or poorly retentive preparations. Their removal is more difficult, however, and on a fragile provisional may fracture it.

Retention can be calibrated, and the technique is worth knowing. Applying cement only to the internal occlusal portion of the provisional, leaving the axial walls free, reduces the force needed for removal without compromising the seal.

A film of petroleum jelly on the axial walls of the abutment has the same effect and is simpler still, but should be used only with well-fitting provisionals: on a loose one it reduces retention too far.

Removing residues before definitive cementation is the step determining adhesion, and the one performed most hastily. An abutment that looks clean retains a film of cement in its irregularities.

Mechanical cleaning with a cup and oil-free abrasive paste is the minimum. Air abrasion with aluminium oxide at low pressure is more effective, and on abutments due to receive an adhesive restoration it should be routine.

The check is made with a probe and on a dry surface: an area with cement residue appears duller and less reflective than clean dentine. It is a difference visible once one knows what to look for.

In summary: no eugenol if bonding will follow, retention calibrated by applying cement only where needed, and abutment cleaning that extends to air abrasion when the definitive will be adhesive.