Do you want to get the best out of 3D-printed restorations—from a smooth surface and stable gloss to reliable temperature control during polishing? In our FAQs, you’ll find practical answers and clear guidelines related to surface roughness, plaque/biofilm, layer lines, and the right polishing workflow.
Why do 3D-printed restorations need to be polished at all?
3D printing processes create characteristic layer structures due to the layer-by-layer build-up of the object. These lead to surface roughness. Accurate polishing reduces roughness and minimizes bacterial plaque and biofilm buildup. At the same time, a smooth surface ensures enhanced color and gloss stability of the restoration in clinical use.
What types of surface textures result from 3D printing?
In additive manufacturing, the individual printed layers create so-called layer lines. Depending on the printing technology, layer thickness, and material, the following may also apply:
- Transitions between layer lines
- Fine stepped structures (stair stepping effect)
- Support contact points
- Microscopic porosity
These structures are often barely visible to the naked eye, but they significantly influence surface roughness and therefore must be smoothed during post-processing.
Are there differences in polishing between resin and filament prints?
Yes. Resin-based prints produced with SLA or DLP processes typically have a finer initial surface, whereas filament prints (FDM) may show more pronounced layer structures due to material deposition. However, the objectives and the approach remain the same: smoothing the surface, reducing roughness, and creating a stable gloss. Modern polishing systems are designed for cross-technology use with resin-based as well as filament-based print materials and do not require strictly material-dependent post-processing.
Why is a visually shiny surface not enough?
A short-term optical sheen can be created, for example, by oils. This effect suggests a smooth surface without permanently changing the actual surface structure. In contrast, polishing reduces the surface's micro-roughness. This results in a stable long-lasting gloss that remains after cleaning, mechanical stress, and prolonged clinical use.
What does a polishing workflow for 3D-printed objects look like?
Surface finishing is carried out in several coordinated steps:
- Pre-polishing to smooth layer lines and print artifacts
- Polishing with a suitable polishing paste to further reduce surface roughness
- Gloss polishing to densify the surface
- High-gloss polishing for a stable, mirror-like surface
This structured workflow using a multi-step polishing system enables reproducible results regardless of material or printing technology.
Can characterization with stains be performed before or after polishing?
As a rule, characterization is performed after pre-polishing. Pre-polishing removes print artifacts and creates a uniform surface structure After this surface preparation, stains can be applied in a controlled manner. The polishing workflow is then continued with the subsequent steps to achieve a smooth, stable surface.
Which speeds are recommended when polishing 3D-printed dental materials?
The recommended speeds depend on the respective polishing step and the instrument used. The following guidelines apply when using the Renfert Polish 3D-printed materials starter kit:
- Pre-polishing with Prepolish 3D side: approx. 6,000–10,000 rpm
- Pre-polishing with Prepolish 3D top: approx. 6,000–10,000 rpm
- Polishing with Bison brush and Renfert Polish 3D-printed materials: approx. 5,000–12,000 rpm
- Gloss polishing with a leather buff: approx. 5,000–10,000 rpm
- High-gloss polishing with a cotton buff: approx. 5,000–12,000 rpm
Key factors are consistent working pressure and controlled heat generation, especially with polymer-based materials such as 3D-printed resins or filaments. Excessive speed or high pressure can cause frictional heat and surface deformation in polymer-based materials.
How much contact pressure should be applied when polishing 3D-printed objects?
When polishing 3D-printed dental materials, use low to moderate contact pressure. The goal is for the polishing instrument to work the surface uniformly without overheating the material.
Excessive pressure can have several disadvantages:
- increased frictional heat
- smearing of the polymer surface with resins
- uneven gloss development
- faster wear of the polishing instruments.
A simple rule applies: let the polisher do the work—not the pressure.
The surface is smoothed step by step using multiple polishing stages (polishing protocol), with speed, instrument, and polishing paste matched to each other.
Why is temperature control important during polishing?
Many 3D-printed dental materials are based on polymers or polymer-bonded hybrid materials. These materials are sensitive to heat. Excessive frictional heat can cause surface deformation, loss of gloss, material smearing, or microscopic structural damage. Therefore, use appropriate speeds, suitable polishing instruments, and moderate pressure. Natural instruments such as cotton buffs or goat hair brushes can help distribute the polishing paste evenly while minimizing excessive heat generation.
