Processing denture acrylics
Merz Dental acrylics are formulated in accordance with the latest state-of-the-art. Multi-stage quality controls from the raw material to the finished product guarantee perfect processability and optimal properties. Constant monitoring of use and examinations guarantee the security of long-lasting, high-quality prosthetics. The processing of the denture base acrylic is the key to success and requires care and foresight for the well-being of the patient.
Acrylic does not cure
Additional monomer or polymer was added during the doughing phase.
Adhere to the specified dosage of powder and liquid, mixing times and doughing phases according to the respective instructions for use, use original Merz Dental measuring aids.
Note: Excess monomer can cause irritation of the mucous membranes.
Water temperature too low and / or polymerisation time too short
Cold-curing polymer 5 - 30 min (depending on the product, see also the corresponding instructions for use) at 45 °C water and 2 - 2.5 bar pressure.
First heat the heat-curing polymer to 70 °C in a water bath, hold for 20 min. Then raise the water bath to boiling temperature and boil for 30 minutes, then let it cool down slowly in the water bath.
Models, plaster counter parts, matrixes and flasks too cold
The polymerisation process does not complete on cold surfaces. This can lead to soft, uncured areas. If possible, soak models in water at room temperature.
Components for hot and cold curing (powder, liquid) mixed-up or different, incompatible components or third-party products were used.
Pay attention to the suitability and usability of the materials. Ensure that the containers are labeled. Use additional labels from Merz Dental.
Polymer 100 g dispenser (REF 10909313)
Monomer 1,000/100 ml bottle (REF 10909314)
Polymer 1,000 g storage container (REF 10909315)
Expiry date exceeded
Check the expiry date before use. Avoid direct sunlight, store in a cool place.
Use clean containers for storing materials as well as for measuring and mixing.
Whitening, discolouration basal
Improper handling of the impression
Blood, saliva and disinfectants must be carefully removed from the impression. Rinse the impression with plenty of clean water.
Plaster surface not sufficiently free of grease, oil or wax
Completely remove wax from the plaster model. Remove isolating solution containing alcohol without leaving any residue.
Isolating solution expired, incorrectly stored or contaminated
Before using the isolation, pay attention to its expiry date. Protect isolation from light, store in a cool place. Always use fresh and clean isolation, use a clean brush for application. Protect the isolation from contamination, always use a clean brush in order not to contaminate the isolation and not to apply any dried and therefore ineffective isolating particles. Rinse the brush carefully with clear water after each use.
Insufficient or missing isolation
Apply a thin layer of isolation 1 to a maximum of 2 times. Further layers do not improve the isolation. Carefully rinse off excess under a soft jet of water, there must be no "puddles of isolating solution". The isolated surface should look "greasy".
Unsuitable isolating solution used
The PremEco Line is recommended for Merz Dental acrylics.
Alginate isolation. Components of resin-refined plasters can prevent a continuous isolating film and may react with denture acrylics.
Use a different plaster if necessary.
Bubble formation and porosities
Wrong plaster type class used
It is recommended to always use type class IV plaster. Type class I and II plasters have a porous surface and soak up too much of the isolating solution.
Soaking the plaster models in the pressure pot
Soaking in the pressure pot pushes water into the gypsum pores. Models "sweat out" excess water when they are exposed to atmospheric pressure again. This lifts the isolating film from the plaster surface. Always soak models in water without pressure.
Wax removers and / or the duration of the boiling-out process influence the plaster surface
When using automatic boiling-off machines, make sure to use suitable additives and their dosage. Heat models for 5 min, remove wax in its plastic state and under no circumstances wait until it has completely liquefied in the boiling-out unit. Briefly steam off models again after they have been boiled out. Do not expose the plaster surface to thermal stress caused by boiling-off for an unnecessarily long time. Clean boiling-off units regularly!
Wax-on-plaster isolation was used
These materials often contain essential oils that prevent the alginate from isolating the plaster properly. The oil film on the plaster surface prevents the plaster from sealing with the alginate isolution. Thoroughly clean the models.
Contamination of the alginate isolating solution by gypsum particles (calcium ions) in the storage container, in the drip tray, etc.
Always use fresh isolation (disposable method), clean the brush before isolating and do not put the used brush back into the container with the alginate isolating solution.
Acrylic briefly mixed, doughing phase too short
Adhere to the mixing ratio of powder and liquid, mixing time and doughing phase according to the instructions for use.
Incorrect polymerisation pressure
Make sure that the pressure in the polymerisation unit is neither above nor below 2 - 2.5 bar. The precisely set pressure prevents the formation of bubbles at boiling point during the exothermic reaction phase.
With heat-curing acrylics
Incorrect polymerisation control, formation of boiling bubbles due to rapid heating (heat-curing polymers); First heat the heat-curing polymer to 70 °C in a water bath, hold for 20 min. Then raise the water bath to boiling temperature and boil for 30 minutes, then let it cool down slowly in the water bath.
With cold-curing acrylics
Water temperature too high in the water bath; Do not exceed a water bath temperature of 50 °C for cold-curing polymers.
Flask and / or plaster models too hot from boiling-out
Allow to cool to room temperature, plaster model not sufficiently soaked in water; Before applying the acrylic, soak plaster models in clear water at room temperature for at least 10 minutes.
Mixing-ratio not adhered to
Use of measuring aids. Pour the powder loosely into the measuring aid, but do not tap down / compact, if necessary reweigh! Too much monomer leads to greater shrinkage of the acrylic.
Too little acrylic (press process)
Make sure there is enough acrylic and press reservoir.
Acrylic inadequately placed in undercuts (press process) results in trapped air
When pressing/packing in undercuts, use small amounts of acrylic dough. In the case of heat-cure polymerisation process, “in-between-pressing” is recommended using polyethylene foil.
Pressure drop during polymerisation; If the pressure falls during polymerisation, the boiling point of the monomer falls and boiling bubbles occur.
Check and adhere to the specified polymerisation parameters. Too much monomer used. Use the measuring aids. Too much monomer causes the acrylic to shrink more strongly.
Isolation layer too thick
Apply a thin layer of isolation 1 to a maximum of 2 times. Further layers do not improve the isolation. Carefully rinse off excess under a soft jet of water, there must be no "puddles of isolation". The isolated surface should look "greasy".
Cooling down too fast
After the heat-curing process, allow the flask to cool down slowly to room temperature to avoid tension in the acrylic.
Too much pressure when polishing
Polish with low pressure using a damp cloth. Otherwise, a thermal load leads to tension, deformation and possibly "burns" on the polished surface.
Incorrect polymerisation pressure
Polymerise cold-curing polymers for 15 - 20 min at 45 °C warm water and 2 - 2.5 bar.
The doughing time of the acryic is not taken into account
Let the acrylic set until it is in a plastic state (can be modeled). Then place it into the pressure pot.
Polymerisation temperature too high for cold-curing polymers
Do not exceed 50 °C water temperature.
Thermal and mechanical stress on the acrylic after polymerisation
Avoid any thermal and mechanical stress as far as possible after curing.
Bite raise after completion
Teeth not sufficiently fixed in the matrix
Apply a tiny drop of superglue onto the labial surface of teeth and fix in the matrix. Ensure that it is completely removed after polymeriation.
Flash when using the flask technique
Due to the system, a flash remains between the flask halves when the press process is used. This causes a bite raise of 0.5 to max. 1.0 mm and can be corrected in the articulator by targeted grinding of the occlusal surfaces. If the flash is unusually thick, it must be checked whether the press pressure on the hydraulic press is sufficient; if necessary, check the pressure with a special pressure gauge. Also check the flask bracket for stability. Check the consistency of the doughed acrylic, doughing time exceeded (see instructions for use), avoid drying out of the acrylic dough by covering the mixing pot.
Press process with cold-curing polymers, the acrylic was processed too slowly in the starting polymerisation phase
If a cold-curing polymer is processed in the pressing process when polymerisation begins, the acrylic solidifies too quickly during the press process. In this case, the flask can no longer be closed exactly. The result is a raised bite. A close observation of the acrylic during the doughing phase can help. Exact “timing” for the correct processing time is crucial and may require some practice when handling cold-curing polymers. If necessary, store the monomer in a cool place, this will extend the processing time.
Trimmed undercut models are used for gel investment in the pouring process
Always trim models at right angles (90°), otherwise they cannot be repositioned correctly and the gel will deform in the process.
Bite decrease after completion
Shrinkage of the base due to high monomer content (casting process)
When using the PremEco Line casting flask, this can be redressed by placing a foil of 0.1 mm thickness between the model and the base of the flask in the dorsal area.
Acrylic on the teeth. Insufficient fixation in investment or the matrix
Apply a tiny drop of superglue on the labial surface of the teeth and fix. Ensure that it is completely removed after polymerisation. Before investing, make sure that there is no more wax on the teeth. In the case of gel investment, free the cavities of residual water before repositioning the teeth so that the teeth can be safely positioned again and are not pushed up by residual water.
Water content in the gel too low due to evaporation (casting process)
If necessary, add some water when melting.
Precision gel unusable after a short time
Gel was heated too much, severe water loss (casting process)
Store dublicating gel in a closed container after use. Add sufficient water to the gel when remelting. When using gel machines, ensure precise temperature control during the heating phase. The gel must not boil, as this would destroy its structure. It is advisable to occasionally check the temperature of the gel both during the melting phase and during the preparation with an external thermometer. The temperature set for the device can sometimes differ significantly from the required temperature (see instructions for use). If the gel is only required occasionally, it can be heated in portions in a microwave (see instructions for use).
Dentures hold poorly (poor suction)
When checking the impression, ensure that the retromolar tuberosity and / or trigonum are precisely registered.
Significant shrinkage of the denture base due to the use of too much monomer
Adhere to the mixing-ratio of powder and liquid, mixing time and doughing phase according to the instructions for use. Determine the powder-to-liquid ratio by using measuring aids or by weighing.
If the doughing phase of the acrylic is too short, so-called suction shrinkage occurs, especially in thick areas of the denture base
Adhere to the mixing-ration of powder and liquid, mixing time and doughing phase according to the instructions for use. Determine the powder-liquid ratio by using a measuring aid or by weighing.
Mucous membrane - redness, irritation, burning
Dosage not adhered to, monomer content too high during mixing
Note the mixing-ratio, use a measuring aid. To reduce the residual monomer content, store the polymerised dental restoration in the finished (sanded) but not polished state for approx. 48 hours at room temperature in water, if possible before fitting.
Pressure points from malocclusion or inaccuracies of fit
Re-articulate and grind bite raised areas after polishing, especially in dentures made by using the press process.
Rough basal surfaces
Note plaster processing. Disinfect and neutralise the impression according to the manufacturer's instructions. Avoid excessive thermal effects, keep evaporation and boiling-out to a minimum. Apply a maximum of 2 thin layers of isolating solution. Further layers do not improve the isolation, carefully rinse off excess under a soft jet of water, there must be no "puddles of isolation". The isolated surface should look "greasy". Always use fresh and clean isolating solution, always use clean brushes for application. Protect isolating solution from contamination. Rinse the brush carefully with clean water after use.
Clarify whether the patient has an allergy record, otherwise clarify which dental restoration materials have been used so far. If information is not available, a doctor should be consulted.
Processing the acrylic
If the patient is known to be sensitive to denture acrylics, we recommend further reducing the residual monomer content:
- Storing the polymerised dentures in the finished (sanded) and not highly polished state in water for up to 48 hours before delivery/incorporation
- It is essential to observe the mixing ratio and the processing instructions in the instructions for use
- If necessary, switch from the pouring to the injection method (Swiss Jet or similar)
- If necessary, switch from cold-curing to heat-curing acrylics (Promloux®, Promolux® High Impact)
These notes apply to:
- The cold-curing denture acrylics (Weropress®, Combipress, PremEco® Line)
- artConcept PLUS