Product features
Passive, not active. The tray maintains the position the case reached. It does not move teeth — that is what separates a retainer from an aligner, and it is the single most common point of confusion.
Clear thermoformed retainer | Clear aligner | |
|---|---|---|
Function | Passive — maintains current position | Active — moves teeth through a planned sequence |
Made from | One formed tray per arch | A series of staged trays |
Case data | Finished-position model | Staged movement files |
Adjustable | No — a new tray is required | No — a new stage is required |
Full-arch coverage with a defined margin. The appliance extends from incisal edge to gingival margin, wrapping the labial and lingual surfaces and engaging the interproximal undercuts just gingival to the contact points. Retention comes from that engagement — not from thickness.
Material families. We form from a small family of thermoplastic sheets, and the family is matched to the case:
Family | Character | Typical use |
|---|---|---|
PETG / PETG copolyester | The workhorse — clear, stiff enough to retain, predictable to form | Most routine retention |
Polypropylene | Softer, more flexible, lower clarity | Short-term or interim retention |
Polyurethane (TPU) | More elastic, higher clarity retention | Cases where comfort drives wear |
Thickness specified by you, not defaulted by us. Common sheet gauges run from 0.75 mm / 0.030" to 1.0 mm / 0.040", with heavier bites sometimes specified at 1.0–1.5 mm. APOS Trends in Orthodontics Thinner trays sit lower and feel more comfortable but are thinner still after forming; thicker trays hold more stiffness but sit bulkier.
Where the gauge comes from: the sheet family is chosen for the case, and the gauge is set by the clinician directing it. Because the finished tray is thinner than the blank, the starting gauge is a case decision rather than a default — if you want a specific build, say so on the work order and we will form to it.
One lab, all three retention appliance families. We make Hawley (acrylic base with a labial wire), clear thermoformed (Essix-type), and bonded/lingual fixed wire. A lab that only makes clear trays will always tell you a clear tray is the answer; we can tell you when Hawley is the better fit, because we make that too.
Fit and finish. Checked around the entire periphery by touch and by sight — no flash, no sharp edges, minimal working of the intaglio surface so the tray keeps seating.
Essix® is a registered trademark of DENTSPLY SIRONA. We use the generic term clear thermoformed retainer to describe the appliance type and refer to Essix retainer only where the field uses that name.
Our production process: seven control points
Every retainer is made in our own facility. These are the stages, in order, and what we control at each.
# | Stage | What we do |
|---|---|---|
1 | Case intake | Receive an intraoral scan (preferred) or a conventional impression. Digital cases come in through 3Shape Communicate, Medit Link, or another platform. |
2 | Model | Print the working model from the scan. For this purpose printed models capture the surface more accurately than milled models. |
3 | Occlusion check | Cross-check the scan against the bite record, then verify the occlusion again on an articulator before forming. |
4 | Forming | Uniform heating, forming under sustained pressure, and progressive cooling under pressure until the sheet has set — the tray is not released hot. |
5 | Trim and polish | Check the entire periphery by touch and by sight for flash and sharp edges, then finish and polish with dedicated instruments. |
6 | Thickness and fit inspection | Calipers at multiple points against the specified thickness; check edge smoothness and extension; trial seating and removal on the model to judge retention; reject any tray with cracks or bubbles. |
7 | Internal surface | Only minimal adjustment. Over-working the intaglio surface is what makes a tray stop seating, so we do not chase minor roughness there. |
Why we describe forming that way. "Uniform heating, cooling under pressure until set" is not a slogan — it is the difference between an evenly formed tray and one with a thin anterior wall. Release the pressure before the sheet has set and the tray pulls back off the model, and you lose the undercut engagement that produces retention in the first place.
Case data requirements, in practice:
- Scan record — the intraoral scan you provide; the design file is produced by our technicians.
- Bite record — required where the occlusion has to be established; we ask for a wax bite registration.
- Printing — models and temporary units can be printed; we do not provide custom trays.
Quality control is a separate team of about 25 inside the facility. Because every production step runs under our own roof, a problem found at inspection is fixed at the step that caused it rather than negotiated with an outside supplier.
Why clear retainers stop fitting
Most clear retainers do not fail because the material was wrong. They fail for two predictable reasons — and both are manufacturing problems.
The tray is thinner than the sheet it started as. A laboratory study of thermoformed retainers measured the finished appliance and found that a 1 mm sheet came out at roughly 0.32 mm in the anterior region — about a third of the original gauge. Doğramacı et al., Australian Dental Journal, 2018 That loss is uneven: it tracks tooth morphology and the forming path, so a tray can feel perfect on a canine and be paper-thin over an incisal edge. The same study found no clear advantage of one thermoforming machine or material type over another for keeping thickness. In other words, equipment spec sheets do not predict the outcome. Process control does.
Retention comes from undercuts, not from thickness. If the scan, the model, or the forming step is off, the tray will seat with finger pressure and then rock loose as soon as the patient talks. That is a fit failure, and it reads to the patient as "my retainer doesn't fit."
This is why retention should be read as a manufacturing problem before a material problem — and why the whole production sequence above is built around it.
Quality control: what we actually measure
Check | Method |
|---|---|
Thickness | Calipers at multiple points, checked against the specified thickness |
Edge and extension | Smoothness, extension and model fit checked — no flash, no lifted edges |
Retention | Trial seating and removal on the stone model to assess grip |
Surface integrity | Reject any tray with cracks or bubbles |
Acceptance | Against the clinician's specification and the signed-off design |
Preventing mix-ups: patient identity through the whole workflow
A staged orthodontic case produces a lot of similar-looking trays. Confusing a stage, or confusing two patients, is a real and avoidable failure — so identity travels with the case.
- Patient number everywhere, all the way through. The patient number is carried on the work order, the model and the appliance itself throughout production.
- Each stage sealed separately and labelled. Every stage is packed in its own sealed bag and marked with which stage it is and when it is to be used.
- High-pressure cleaning, then individual packaging. Cases are cleaned under high pressure and individually bagged with the patient's identification.
Why Istar for clear retainers
We are the factory, not a broker. Istar Dental Lab was founded in 2012 and runs two production facilities, in Shenzhen and Huizhou, China. We complete the full production process in-house and do not put cases out to third-party labs.
Scale and team. Approximately 460 staff, including a dedicated QC department of about 25 and a customer service and case-coordination team of about 40. We keep roughly 50 trained backup workers to hold delivery times steady through peak season.
Track record. We serve 50+ dental laboratories, 100+ clinics, and 400+ dentists, with our main markets in the United States and across Europe (Netherlands, Germany, France, Belgium, Austria, the United Kingdom, Luxembourg, Switzerland).
Verify it yourself. We welcome factory visits and video factory inspections for clinics, labs and partners — you can see the workflow, the production floor and the QC procedure rather than take our word for it.
Working with us
Send a case — scan record plus bite registration where the occlusion must be established. Orders come in through 3Shape Communicate, Medit Link, or another platform; your scanning workflow does not have to change.
Get a technician's read — if you are not sure whether a case calls for a clear tray, a Hawley, or a bonded wire, send it and we will say how we would approach it. If a clear thermoformed retainer is not the right answer for the case, we will tell you.
Turnaround — simple retention cases move quickly; multi-stage cases are scheduled stage by stage, so you always know which stage is in production. One thing worth knowing up front: design sign-off, missing records and time spent waiting on your reply are not counted against the quoted turnaround — the clock restarts once the case data is complete and confirmed.
Talk to a person — a dedicated case coordinator follows your cases and keeps you informed of production stage. During working hours, case messages are normally answered within about an hour; outside those hours, time-zone lag can add 7–8 hours, and 12 hours is the outside limit.
[Send a case →] · [Book a video factory tour →]
FAQ
What is a clear thermoformed retainer, and how is it different from a Hawley retainer? A clear thermoformed retainer is a passive plastic tray covering the full arch, formed over a model of the finished case. A Hawley retainer uses an acrylic base with a labial wire and can be adjusted for minor tooth movement; a clear tray cannot be adjusted and is replaced when it no longer fits. See the comparison table in Product features.
Is this the same as a clear aligner? No. A retainer is passive and holds the position the case already reached. An aligner is active and moves teeth through a planned sequence. They are made from different case data and worn to different protocols.
How long will a clear retainer last? Working life depends mostly on how the tray is worn and cared for — grinding, heat exposure, and cleaning habits are the main variables. Because the finished tray is thinner than the starting sheet, a thinner build has less material to lose before retention drops. Published studies report clear retainers needing replacement on a shorter cycle than Hawley-type appliances, largely because the plastic degrades rather than being serviced. Colgate — What is an Essix retainer
Can one tray double as a night guard or a whitening tray? Not properly. A retention tray and a night guard are different appliances with different thickness requirements, and a retention tray has no reservoir for whitening gel. Where grinding is the concern, the appliance should be ordered as a guard, not as a retainer. We make guards as well as retainers, so we can take either version of the case.
How do you check thickness and fit? Calipers at multiple points against the specified thickness; edge smoothness, extension and model fit checked; seating and removal trialled on the model to judge retention; any tray with cracks or bubbles rejected. Acceptance is against the clinician's specification and the signed-off design.
How do you avoid mixing up stages or patients? The patient number is carried on the work order, model and appliance throughout; each stage is individually sealed and labelled; cases are high-pressure cleaned and individually packaged with patient identification.
Do you decide the thickness? No. Hardness and thickness are decisions for the clinician directing the case. We form, measure and document what was specified.
How do I send a case? Digital cases come through 3Shape Communicate, Medit Link, or another platform. Include the scan record and, where the occlusion must be established, a wax bite registration. Your coordinator will confirm receipt and walk you through any missing data.
References
- Doğramacı EJ, Chubb DWR, Rossi-Fedele G. Orthodontic thermoformed retainers: a two-arm laboratory study into post-fabrication outcomes. Australian Dental Journal, 2018. https://doi.org/10.1111/adj.12610
- Clear retainer — APOS Trends in Orthodontics. https://apospublications.com/clear-retainer/
- Essix Plastics — DENTSPLY SIRONA. https://www.dentsplysirona.com/en-us/discover/discover-by-brand/essix-plastics.html
- What is an Essix retainer — Colgate Oral Health. https://www.colgate.com/en-us/oral-health/adult-orthodontics/what-is-an-essix-retainer