11.4 Intracoronal Temporary Restorations: IRM, Cavit, Glass Ionomer & Resin Temporaries
Key Takeaways
IRM is a polymer-reinforced zinc oxide-eugenol temporary that sedates the pulp and lasts longer than plain ZOE.
Cavit is a premixed temporary that sets on contact with moisture and needs about 3 to 4 mm of thickness to seal an endodontic access opening.
Eugenol inhibits resin polymerization, so eugenol-containing temporaries are avoided where a bonded composite restoration will be placed.
Glass ionomer interim restorations bond chemically to tooth structure and release fluoride, which suits high-caries-risk and young patients.
Occlusion and contacts are checked on every temporary, and floss is slid out sideways so that the fresh material is not dislodged.
11.4 Intracoronal Temporary Restorations: IRM, Cavit, Glass Ionomer & Resin Temporaries
Quick Answer: Competency 5.7.8 covers temporary (interim) restorative materials placed inside a cavity or access opening. Section 11.3 covers provisional crowns and bridges. Temporary fillings:
- sedate an inflamed pulp (zinc oxide-eugenol)
- seal endodontic access openings between visits
- control caries (glass ionomer interim restorations)
- protect a tooth until the final restoration is placed.
The main materials are IRM (reinforced zinc oxide-eugenol), Cavit (a premixed material that sets with moisture and needs about 3 to 4 mm of thickness to seal), glass ionomer and light-cured resin temporaries. Eugenol materials must not be used where a bonded composite restoration will be placed later.
1. Why Temporary Restorations Are Placed (5.7.8.1)
| Situation | Purpose | Usual material |
|---|---|---|
| Deep caries with a sensitive but vital pulp | Calm the pulp (obtundent effect) and wait to see whether symptoms settle | ZOE or IRM "sedative filling" |
| Between endodontic appointments | Seal the access cavity to prevent saliva and bacterial leakage into the canals | Cavit or IRM (often over a sterile cotton pellet or PTFE tape) |
| High caries risk, very young or uncooperative patients | Remove soft caries and seal the tooth until definitive care (interim therapeutic restoration) | Glass ionomer |
| Indirect inlay or onlay preparation | Protect the preparation until the restoration returns from the lab | Light-cured resin temporary or IRM |
| Lost or fractured restoration (emergency visit) | Relieve sensitivity and protect the tooth until a scheduled appointment | IRM or glass ionomer |
| Stepwise caries removal | Seal the tooth for several months to allow tertiary dentin formation before final excavation | Glass ionomer or IRM |
2. Temporary Restorative Materials
| Material | Composition and set | Advantages | Limitations |
|---|---|---|---|
| IRM (Intermediate Restorative Material) | Zinc oxide reinforced with polymer, mixed with eugenol; acid-base set | Sedative to the pulp; stronger and longer-lasting than plain ZOE (months); easy to remove | Eugenol inhibits resin polymerization, so avoid it under future composites; possible eugenol sensitivity |
| Plain ZOE temporary | Zinc oxide and eugenol | Excellent sedative effect | Weak; wears quickly |
| Cavit (premixed temporary) | Zinc oxide, calcium sulfate and other ingredients in a premixed paste; sets on contact with moisture and expands slightly | No mixing; very good seal for endodontic access openings | Low strength and wear resistance; needs about 3 to 4 mm thickness; patient should avoid chewing on it for about an hour while it hardens |
| Glass ionomer (conventional or resin-modified) | Fluoroaluminosilicate glass and polyacrylic acid | Chemical bond to tooth; fluoride release; good for interim therapeutic restorations and children | Sensitive to moisture during the early set; lower wear resistance than amalgam or composite |
| Light-cured resin temporary | Flexible resin paste cured with the curing light | Quick, no mixing, easy to remove in one piece | No sedative effect; requires a curing light |
3. Preparing and Mixing (5.7.8.2)
- IRM powder and liquid:
- Fluff the powder and dispense it with the measuring scoop.
- Dispense the eugenol drops and replace the cap at once (eugenol evaporates and oxidizes).
- On a paper pad or glass slab, incorporate the powder into the liquid in increments with a stiff spatula until the mix is a thick, putty-like consistency that does not stick to the gloved finger or instrument.
- Follow the manufacturer's powder-liquid ratio and working time. Capsule versions are triturated instead.
- Cavit: dispense directly from the tube or jar with a plastic instrument and recap immediately. It sets once in contact with moisture.
- Glass ionomer: activate and triturate capsules, or mix powder and liquid according to the instructions. Place the material while it is still glossy.
- Resin temporaries: dispense from the syringe and light-cure as directed.
4. Placement Sequence
- Isolate with cotton rolls (or a dental dam for endodontics) and dry the cavity lightly. Glass ionomer needs a moist, not desiccated, surface.
- For an endodontic access, place a sterile cotton pellet or PTFE tape over the canal orifices first, leaving enough room for 3 to 4 mm of temporary material above it.
- For a proximal cavity, place a matrix band and wedge so that the temporary has a proper contour and does not leave an overhang.
- Carry the material with a plastic filling instrument (PFI) in small increments and condense it into the cavity, working it against the walls to seal the margins.
- Contour with a carver or the PFI, and smooth the surface with a moist cotton pellet. Remove excess from the margins and embrasures.
- Check occlusion with articulating paper once the material is firm, and reduce high spots. A high temporary causes pain and fractures.
- Check proximal contacts and margins with floss. With a fresh temporary, slide the floss out sideways rather than snapping it back up through the contact, which can dislodge the material.
- Evaluate: the margins should be closed, with no overhang or voids, a comfortable bite and a smooth surface. Record the material, the tooth and the surfaces in the progress notes.
5. Removing a Temporary
At the next appointment, the temporary is removed with a spoon excavator, a scaler or a slow-speed bur. The cavity is then cleaned of all residue before the definitive restoration. Clean all eugenol residue carefully if a bonded restoration is planned. Glass ionomer temporaries are often partly kept as a base or liner if the dentist prefers.
6. Patient Instructions (5.7.8.3)
- "This is a temporary filling. It is softer than a permanent one and is meant to last only until your next appointment."
- Avoid chewing hard, crunchy or sticky foods on that side. With Cavit, do not eat on it for about an hour.
- Brush normally. When flossing next to the temporary, slide the floss out sideways.
- If the temporary breaks, falls out or feels high, or if pain, swelling or sensitivity increases, call the office.
- Keep the appointment for the final restoration. A temporary left too long can leak or fracture, letting decay return or bacteria re-enter the canals.
Between endodontic appointments, the dentist asks for Cavit over a cotton pellet in the access cavity. About how thick must the Cavit layer be to seal reliably?
About 1 mm
About 3 to 4 mm
At least 10 mm
About 0.5 mm
The dentist plans to place a bonded composite restoration at the next visit. Which temporary material should be avoided today?
Conventional glass ionomer cement
Light-cured flexible resin temporary
Resin-modified glass ionomer (RMGI)
IRM (reinforced zinc oxide-eugenol)
After placing a proximal temporary restoration, how should the assistant remove floss from the contact?
Pull it upward with a sawing motion
Snap it back up through the contact area
Cut it and leave a piece in the contact
Slide it out sideways through the embrasure
Sections you finish are checked off in the contents.