PMMA Temporary Crowns — Testing Occlusion and Esthetics Before Final Restoration

For extensive changes in occlusion — increasing vertical dimension, reconstructing multiple teeth — the laboratory can prepare PMMA temporary crowns instead of immediately fabricating the final restoration. This is not just convenience for the patient, but a risk reduction strategy.

Why PMMA temporary crowns are needed

New occlusion, changed vertical dimension, new mandibular movement patterns — the patient cannot evaluate these changes just by sitting in the chair. They need several weeks of wearing, eating, and speaking to provide honest feedback.

PMMA temporary crowns allow testing of:

• Dynamic occlusion — whether the patient experiences discomfort during chewing
• Esthetics — shape, length, and proportions of teeth in daily use
• Phonetics — pronunciation of sibilants (s, c, z), labiodentals (f, v), and dental sounds
• Vertical dimension of occlusion (VDO) — whether the patient tolerates the new mandibular position
• Canine and anterior guidance — whether dynamic occlusion functions correctly

Milled PMMA vs. chairside temporaries

Temporary crowns made chairside (e.g., from Protemp, Luxatemp) have limitations:

• Occlusion adjusted manually — imprecise
• Simplified anatomy — lack of morphological details
• Durability of 2–4 weeks — then material degradation
• Inability to transfer parameters to the final restoration

Milled PMMA in CAD/CAM:

• Occlusion digitally designed on a virtual articulator
• Full anatomy from the wax-up — the patient tests exactly the shape that will be in ceramic
• Durability of 3–6 months — sufficient for a full testing phase
• Occlusal parameters saved in the CAD design — 1:1 transfer to ceramic

Workflow with PMMA at deltalabs.

Step 1: The dentist sends a scan of the preparations, CR bite registration, and wax-up (or commissions it from us).

Step 2: We design the PMMA crowns in CAD based on the wax-up. Occlusion is set on a virtual articulator, considering canine and protrusive guidance.

Step 3: We mill the crowns from PMMA blocks (e.g., Telio CAD, Vita CAD-Temp). Color is chosen according to patient preference.

Step 4: The dentist cements the PMMA using temporary cement. The patient wears the crowns for 4–8 weeks.

Step 5: After the testing phase, the dentist provides feedback — what works, what needs correction. Corrections are implemented in the CAD design.

Step 6: The final restoration (zirconia, e.max) is milled from the corrected design.

When PMMA is necessary

• Change in VDO (vertical dimension of occlusion) — any VDO increase of >1 mm should be tested
• Full arch reconstruction (8+ units)
• Implant cases with immediate loading
• Patient with parafunctions (bruxism) — testing occlusal durability before ceramic fabrication
• Esthetic cases in the anterior segment — the patient must see the effect in their mouth

When PMMA can be omitted

• Single crowns without occlusal changes
• Restorations that do not change VDO
• Simple 3-unit bridges in stable occlusion
• Implant restorations with preserved natural occlusion

Cost vs. risk

Milled PMMA costs a fraction of a ceramic restoration. Remaking 12 zirconia crowns costs tens of thousands of zlotys. The PMMA phase, which prevents this remake, pays for itself many times over.

Patients appreciate the ability to "test drive" new teeth. This builds trust and reduces the number of complaints after the final restoration is seated.

1. How long should a patient wear PMMA?

Minimum 4 weeks. For large VDO changes — 6–8 weeks. Goal: occlusal stabilization and full neuromuscular adaptation.

2. Will PMMA last several months?

Milled PMMA from CAD/CAM blocks (Telio CAD, Vita CAD-Temp) lasts 3–6 months of normal use. Chairside temporaries degrade after 2–4 weeks.

3. Are corrections made on PMMA transferred to ceramic?

Yes — this is a key advantage of the digital workflow. Corrections made on PMMA are saved in the CAD design and automatically transferred to the final restoration design.