Thermoforming is one of the most useful things a dental office lab does. A heated plastic sheet is drawn or pressed over a stone or printed model to make bleaching and fluoride trays, custom sports guards, clear retainers, temporary appliances, and some occlusal guards. The machines are simple, but the results vary a lot with material choice, thickness, heating, and model preparation.
This guide covers vacuum vs. pressure formers, materials and thicknesses by appliance, a step-by-step technique, daily use, maintenance, troubleshooting, and buying. It is educational information about equipment and lab technique. Appliance design and indications are clinical decisions for the dentist. For deciding whether to bring appliance work in house at all, see in-office dental lab equipment.
Key takeaways
- Vacuum formers pull the softened sheet onto the model with suction; pressure formers push it on with compressed air. Pressure forming generally adapts thicker and harder materials more precisely.
- Soft EVA suits bleaching trays and sports guards; hard copolyester (PETG) suits retainers, splints, and aligner-style appliances. Always follow the sheet manufacturer's heating and indication guidance.
- Forming thins the sheet, especially over incisal edges and cusps. Start thicker than the finished thickness you need, particularly for sports guards.
- Most failures trace to a wet model, wrong heating, leaks at the frame, or clogged platform holes, not the machine itself.
- Used forming machines are good buys if the heater heats evenly, the frame seals, and vacuum or pressure holds.
What it does and how it works
Both machine types have a heater, a clamping frame that holds the sheet, and a platform for the model. The operator clamps a sheet in the frame, heats it until it softens, then brings it down over the model.
- Vacuum formers have a perforated platform connected to a vacuum motor. When the soft sheet seals over the platform, suction pulls it tight against the model. Buffalo Dental's Tray-Vac and Econo-Vac, for example, use 5 by 5 inch sheets and built-in electric vacuum motors.
- Pressure formers seal the sheet over the model in a chamber and apply compressed air from above. Erkodent lists its Erkopress motion at 6 bar of working pressure, with infrared heating, 120 mm round foils, and an automated forming and cooling cycle. Some pressure formers connect to a compressed air supply; others generate pressure internally. Check your IFU.
Many machines also offer a bead or granulate basket that embeds the model so only the area to be covered is exposed, which helps with partial coverage and deep undercuts. Buffalo Dental's Sta-Vac II combines a flat vacuum table with a bead basket.
Parts you should know
- Heater. Radiant coil or infrared element above the sheet.
- Frame and gasket. Clamps the sheet and seals it; worn gaskets leak.
- Platform or chamber. Perforated table (vacuum) or sealed pressure pot.
- Vacuum motor or air connection. The forming force.
- Timer, temperature sensor, or material program. Newer units store heating parameters by material and thickness; Erkodent uses a touchless temperature sensor on its motion units.
- Trimming tools. Scissors, a thermal knife (Buffalo Dental's ThermaKnife is one example), burs in a lab micromotor, and polishing wheels.
Which type does your practice need?
| Factor | Vacuum former | Pressure former |
|---|---|---|
| Forming force | Limited by atmospheric pressure (under 1 bar of pressure difference) | Several bar of air pressure (6 bar on one current model) |
| Adaptation with thin soft sheets | Good | Very good |
| Adaptation with thick or hard sheets | Fair; more rounding at margins | Very good; sharper detail |
| Typical uses | Bleaching and fluoride trays, simple guards, custom trays | Retainers, splints, laminated sports guards, aligner-style appliances |
| Utilities | Standard outlet | Outlet; some models need compressed air |
| Cost | Lower | Higher |
Decision guide
- Mostly bleaching and fluoride trays: a vacuum former is enough.
- Regular retainers, guards, or laminated sports guards: a pressure former pays for itself in remakes avoided.
- High volume or orthodontic practices: a pressure former with stored material programs and automated cycles saves staff time and improves consistency.
- Using printed models: check that your resin model material tolerates forming heat and pressure; many labs print solid or thick-walled models for forming.
Materials and thicknesses by appliance
Sheet manufacturers publish their own thickness and indication charts, and those govern. The table below summarizes commonly used ranges and Erkodent's published ranges as a reference. Thickness is often listed in inches in the US (0.040 inch is about 1 mm) and in millimeters elsewhere.
| Appliance | Typical material | Commonly used starting thickness | Former | Notes |
|---|---|---|---|---|
| Bleaching tray | Soft EVA | About 0.035 to 0.040 inch (roughly 0.9 to 1.0 mm) | Vacuum or pressure | Reservoirs, if the dentist wants them, are blocked out on the model first |
| Fluoride or medicament tray | Soft EVA | Similar to bleaching trays | Vacuum or pressure | Follow the dentist's design |
| Clear retainer (Essix-style) | Hard copolyester (PETG) | About 0.75 to 1.0 mm (0.030 to 0.040 inch) | Pressure preferred | Erkodent lists its aligner material at 0.6 to 1.0 mm |
| Occlusal guard or splint | Hard copolyester, soft EVA, or dual laminate | Often 1.5 to 3 mm; per design | Pressure preferred | Erkodent lists Erkodur from 0.5 to 5 mm |
| Custom sports guard | EVA, often laminated in layers | Commonly 3 to 4 mm or more before forming; multi-layer blanks exist | Pressure preferred | Erkodent's Playsafe triple is 5.5 mm (Triple Light 4.1 mm), soft-hard-soft |
| Custom impression tray or baseplate | Tray material sheet | Per product | Vacuum or pressure | Spacer on model if the design calls for it |
Why thickness drops during forming. The sheet stretches as it drapes over the model, and it stretches most over the highest points: incisal edges and cusp tips. A sheet that starts at 4 mm can finish noticeably thinner over the incisors. That is why sports guards are often made from thick or laminated blanks, and why pressure forming, which adapts faster and more evenly, helps.
Stocking sheet material sensibly
Offices tend to accumulate a drawer of half-used sheet boxes in every thickness. A tighter approach works better: stock one soft EVA thickness for bleaching and fluoride trays, one hard copolyester thickness for retainers, and one guard or sports guard material, then add others only when the dentist's designs call for them. Match sheet shape and size to your frame (square 5 by 5 inch sheets on many US vacuum formers, round blanks on many pressure formers). Keep each material's IFU with the box, because heating times differ between brands even at the same thickness. Rotate stock, because some materials absorb moisture or age on the shelf, and write the open date on the box.
Technique: step by step
A generic sequence. Follow your machine and material IFUs for temperatures, times, and cooling.
- Model. Pour a bubble-free stone model (or print one), and let stone set fully.
- Trim. Trim the base flat and thin enough that the model does not stand too tall on the platform. For bleaching trays, trim to a horseshoe with a shallow vestibule. Remove nodules and fill voids.
- Block out. Block out undercuts that would lock the appliance on the model, and add reservoirs or spacers if the dentist prescribes them. Cure light-cured block-out per its IFU.
- Dry. Let the model dry. A wet model releases steam under the hot sheet and causes bubbles and poor adaptation. Some hard sheets absorb moisture and may need drying per the material IFU.
- Position. Center the model on the platform (or in the bead basket) with the occlusal plane roughly parallel to the sheet. Leave space between multiple models.
- Heat. Clamp the sheet, remove any protective film, and heat. Older vacuum formers rely on visual sag; newer units use timers or temperature programs. Under-heating gives poor detail; over-heating thins and whitens material.
- Form. Bring the sheet down over the model and apply vacuum or pressure immediately.
- Cool. Let the appliance cool on the model for the time the IFU specifies; removing it warm distorts it.
- Remove and trim. Cut away excess sheet, remove from the model, and trim to the design line with scissors, a thermal knife, or a bur. Keep margins smooth.
- Finish. Smooth and polish edges; a flame or heat polishing step is used with some soft materials per their IFU.
- Clean and deliver. Clean and disinfect per your protocol, label, and bag with care instructions.
Tip: keep a laminated card at the machine with your settings for each material and thickness you stock. Consistency is the difference between a five-minute tray and a remake.
How to use it: daily operation
Start of day
- Check the platform is clean and holes are clear (vacuum) or the chamber seal is clean (pressure).
- Confirm air supply pressure if your pressure former uses shop air.
- Run a warm-up if the IFU calls for it.
Between cases
- Remove sheet scraps and stone crumbs from the platform and frame.
- Let the heater and frame cool to safe handling temperature before adjusting.
- Wipe the platform and handles; models and appliances should already be disinfected.
End of day
- Turn off the heater and main power.
- Clear granulate or beads from the basket and store them covered.
- Store sheets flat, in their packaging, away from heat and humidity.
Maintenance schedule
| Task | Frequency | Who | Notes |
|---|---|---|---|
| Clear platform, frame, and chamber of debris | Daily | Lab user | Stone dust clogs vacuum holes |
| Check frame gasket and chamber seal | Weekly | Staff | Cracked seals cause poor adaptation |
| Clean vacuum platform holes with a pin or brush | Weekly | Staff | Power off |
| Inspect heater for even glow or heating | Monthly | Staff | Uneven heating means element trouble |
| Check air filter or water trap on air supply (pressure formers) | Monthly | Staff | Moisture in air can mark sheets |
| Verify timer or temperature program against a test sheet | Quarterly | Staff | Compare to a known good result |
| Replace gaskets and seals | As needed or per IFU | Staff or technician | Use manufacturer parts |
| Heater element, vacuum motor, pressure system service | Per manufacturer or when failing | Technician | Electrical and pressure components are not staff repairs |
Troubleshooting
| Symptom | Likely causes | What to try | When to call a technician |
|---|---|---|---|
| Poor adaptation, rounded detail | Sheet under-heated; weak vacuum; leak at frame; clogged holes | Increase heat per IFU; clean holes; check gasket | If vacuum or pressure will not reach normal |
| Webbing or folds between models | Models too close or too tall; sheet over-heated and sagging | Form one model at a time; reduce model height; adjust heat | Rarely |
| Bubbles in the appliance | Wet model; moisture in sheet | Dry model; dry sheets per material IFU | No |
| Thin spots or holes over incisal edges | Over-heating; sheet too thin for the appliance | Reduce heat; start thicker | No |
| Hard material turns cloudy or white | Over-heating or stress from removing warm | Adjust heat; cool fully before removal | No |
| Sheet slips out of frame | Worn frame clamp; wrong sheet size | Use correct size; check clamp | If clamp is broken |
| Appliance locked on model | Undercuts not blocked out | Section carefully or remake with block-out | No |
| Heater does not heat or heats unevenly | Element or control failure | Confirm power and settings | Yes; element work is technician work |
| Pressure former will not build pressure | Air supply off or low; chamber seal leak | Check supply and seal | If supply and seal are good |
Safety and compliance
- Burns. Heaters, frames, and freshly formed sheets are hot. Use the handles and let parts cool.
- Fumes. Heating and trimming thermoplastics can release odors and fumes. Work in a ventilated area and follow the material's safety data sheet.
- Sharp tools. Thermal knives and scissors cause most lab injuries in this workflow.
- Infection control. Disinfect impressions and models before lab work and appliances before delivery, per CDC's dental infection prevention guidance and your protocol.
- Materials. Use sheets sold for intraoral dental use and follow their labeled indications. Appliance design and patient instructions are clinical decisions.
- Compressed air. Pressure formers that use shop air draw from the same compressor as your operatories. Confirm the air demand fits your compressor sizing.
- Electrical. Heater and motor repairs are technician work.
Buying new vs. used
Used former inspection checklist
- Heater reaches temperature and heats evenly across the sheet
- Vacuum former: strong suction; platform holes clear; frame gasket intact
- Pressure former: reaches rated pressure and holds it; chamber seal intact; air fittings present
- Frame locks securely and accepts sheet sizes you can still buy
- Timer, temperature sensor, or material programs work
- Test-form a sheet and inspect the adaptation
- Manual, spare gaskets, and bead or granulate basket included
Red flags: scorched or cracked housings near the heater; a machine that only works with a discontinued proprietary sheet size; a pressure former with a damaged chamber or missing safety interlock; and any unit that cannot be test-formed before purchase.
Rough price ranges
Rough ranges only; they vary by brand, model, condition, region, and year. Simple new vacuum formers commonly run from several hundred dollars to about $1,500. Pressure formers commonly run several thousand dollars, with automated models at the top. Used units often sell for well under half of new. Sheet stock is a recurring cost; price the materials you will actually use.
Forming machines are durable; heaters, gaskets, and vacuum motors are the wear items.
Brands and models you will see
Examples include:
- Buffalo Dental: Tray-Vac, Econo-Vac, and Sta-Vac II vacuum formers, EVA tray material, and the ThermaKnife.
- Erkodent: Erkoform-3d motion and Erkoform-3d+ vacuum units; Erkopress motion, Erkopress ci motion, and Erkopress 240 pressure units; Occluform-3; Erkodur, Erkoflex, and Playsafe materials.
- Scheu Dental: BIOSTAR and MINISTAR S pressure forming units and thermoforming materials.
Related guides
Forming is one station in the office lab. See model trimmers and basic lab equipment for pouring and trimming, and dental 3D printers if you want to print models for forming. For whether in-house appliances make financial sense, read in-office dental lab equipment, and browse used lab gear on the marketplace.
Always follow the manufacturer's instructions for use (IFU) for your specific model. Repairs involving electrical, pressure vessel, radiation, or gas line work belong with a qualified technician. Infection control and radiation rules vary by state. Prices are rough ranges that vary by model, condition, region, and year. ChairsideSource is not affiliated with any manufacturer named here.