Occlusal splints: milled, 3D-printed or thermoformed?

How is each type of occlusal splint made?

A milled splint is cut from a PMMA disc polymerized at the factory; a printed splint is built layer by layer from a light-cured resin and finishes polymerizing in post-cure. A thermoformed splint is a thermoplastic sheet heated and formed, by vacuum or pressure, over a physical model of the arch. Milled and printed splints come from a CAD design made on the scan; a thermoformed one depends on the model, whether stone or printed.

Studies compare all three against the conventional processed splint, in heat-cured or self-cure acrylic. Each process covers more than one material: rigid and flexible printing resins, thermoplastic sheets of different hardness and, for milling, PEEK as well as PMMA.

Most of this is bench data. The in-mouth study that compared milled and printed splints had 49 patients and six months, and we found no clinical study comparing all three processes. The occlusal scheme, the indication and the wear schedule are your decisions.

Which occlusal splint wears least?

Among rigid splints, bench wear is similar; thermoformed splints and flexible resins wear more. In the systematic review by Grymak and colleagues (Journal of Prosthodontics, 2022), covering 11 studies, heat-cured, milled and printed splint materials did not differ from one another. Vacuum-formed material wore the most, and PEEK the least.

Lawson and colleagues (The Journal of Prosthetic Dentistry, 2025) ran the comparison again over 400,000 load cycles. Rigid printed resins wore like milled, heat-cured and light-cured materials. Thermoformed and self-cure materials wore more, and flexible printed resins wore the most.

The common thread is hardness. In Lawson’s test, the softer the material, the more it wore, with a correlation of −0.93. Grymak’s review adds that test protocols vary widely between studies and that every splint material needs polishing.

In the mouth the picture changed. In the retrospective study by Yıldıran, Kurtça and Röhlig (The Journal of Prosthetic Dentistry, 2026), printed splints showed more surface wear than milled ones after six months of use, in 49 patients.

Which occlusal splint fits best?

The milled splint was the truest to the design on the bench and fit best in the mouth. Reymus, Hickel and Keßler (Clinical Oral Investigations, 2020) printed splints in four resins and two orientations and compared them with a milled splint. The milled splint was truest to the CAD file, and the printed ones were the most repeatable; resin choice mattered most, and the authors judged the two equivalent for clinical use.

In the 2026 in-mouth study, the gap was wider: 0.039 mm of fit deviation for milled splints, in PMMA and PEEK, against 0.28 mm for printed ones. Retention over time differs too. Hickl and colleagues (The International Journal of Prosthodontics, 2024) pulled 120 mandibular splints off metal arches, cycle after cycle, until they failed. Milled and hand-made splints lasted more cycles than printed and thermoformed ones.

Does the splint material age in the mouth?

Every splint material loses properties as it ages, and the rate depends on the process. In the systematic review by de Melo-Soares and colleagues (The Journal of Prosthetic Dentistry, 2026), covering 21 studies, milled resins were the most stable after artificial aging. Heat-cured acrylic was in the middle, and self-cure acrylic did worst.

For printed splints, print and post-cure settings affected stability, and thermoformed sheets don’t always lose out. Nică and colleagues (Dentistry Journal, 2026) aged four materials in artificial saliva. Two printed resins lost more than milled PMMA and a thermoformed PETG sheet, and one of them lost more than 49% of its flexural modulus. PETG was the most stable material in the test.

What should drive the choice of process?

The process determines the material that carries out the plan, and the plan (occlusal scheme, indication, wear schedule) is yours. For a hard splint meant for long-term wear, milled has the most data on fit and stability. A rigid printed splint comes close on bench wear, but it depends on the resin, orientation and post-cure.

A thermoformed splint is formed over a physical model and wore more than rigid splints in testing, although PETG aged well in one study. Flexural and fracture strength figures for milled PMMA against processed acrylic are on our milled occlusal splint page.

What should you send the lab for a splint?

For any splint, the lab needs both arches, a bite record at the position and opening you chose, and three decisions from you. Send:

• intraoral scans of both arches, or stone models;
• a bite record at the position and opening chosen for the splint;
• the arch, the thickness and the occlusal scheme;
• a signed prescription.

At Smile Digital Lab, the splint in our catalog is milled PMMA, designed and milled here in São Paulo, Brazil. Mandibular splints, thickness and unusual guidance schemes are confirmed when the case is opened; if your case calls for a different process, ask before you send it. The intraoral scanning guide shows how to scan the bite, and the basics are in how to send a case to the lab.