3D printing resins in dentistry – which resin for models, splints, aligners and dentures?

The resin determines whether a print is merely a working model or a medical device that goes into the patient's mouth. Below is a short guide to the resin classes used in dentistry and what to look for when choosing them.

Biocompatibility classes – what they mean

• No patient contact – model resins (working models, orthodontic models, models for thermoforming). Accuracy, a matte surface and a low cost per liter are what matter.
• Class I / IIa (short-term contact) – surgical guides, custom trays, splints, temporary crowns. A medical device (MDR) certificate and full post-processing according to the instructions are mandatory.
• Class IIa (long-term contact) – denture bases, denture teeth, directly printed aligners, retainers. The highest requirements for strength, color stability and biocompatibility.

Models

A model resin must produce a dimensionally stable, opaque print with low shrinkage. For orthodontic models used for thermoforming, choose a heat-resistant material with a smooth surface so that the foil does not "copy" the layers.

Splints and retainers

Transparent materials that resist cracking and wear. Post-processing is crucial: thorough washing and curing in a UV chamber – ideally in a nitrogen atmosphere, which eliminates the oxygen inhibition layer and improves translucency and strength.

Surgical guides

A Class I transparent, sterilizable resin (autoclave or the method recommended by the manufacturer). Check that the manufacturer specifies a sterilization protocol – this is a prerequisite for clinical use.

Directly printed aligners

This is the biggest change of recent years: instead of thermoforming a foil over a model, the aligner is printed directly from a shape-memory resin, such as Graphy Tera Harz TC-85. Advantages: controlled thickness, no model required, and the option to design different stiffness within a single aligner. However, a dedicated nitrogen curing chamber and a step-by-step post-processing procedure are required.

Dentures

Denture bases are made from high-strength resins with a stable gingival shade (e.g. Tera Harz THD), while flexible dentures use materials with increased elasticity (Tera Harz TFDH). Denture teeth are printed separately or prefabricated teeth are used.

What to look for when choosing

1. Does the resin have a validated profile for your printer (385 or 405 nm wavelength, LCD/DLP)?
2. Does the manufacturer provide complete post-processing instructions (washing time, curing time and temperature, atmosphere)?
3. What is the real cost per case, including waste and supports?
4. Is there a safety data sheet and an MDR certificate?

You will find our full range in the 3D printing resins section. If you would like to test a material before implementing it, contact us – we will help you choose a resin for your printer and set the parameters.