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Typical Issues in Dental UV 3D Printing (Part 5)

Release time:

2026-08-14 17:03

Typical Issues in Dental UV 3D Printing (Part 5)

The essence of stereolithography (SLA) 3D printing is layer-by-layer additive manufacturing, and at the boundaries between cured layers, a microscopic stair-step structure—known as layer lines—inevitably remains. This characteristic is an intrinsic feature of SLA; in dental applications, it can pose two potential risks: increased surface roughness creates favorable conditions for bacterial adhesion, while stress concentrations in the layer‑line regions may compromise the long-term durability of the printed part. Post‑processing significantly influences surface quality, and appropriate treatment can partially mitigate this inherent drawback.

I. Structural Characteristics and Influencing Factors of Layered Structures

Layer lines arise from the layer-by-layer curing process. During each layer’s curing, ultraviolet light penetrates the resin to induce polymerization; however, light scatters slightly at the interfaces between layers, resulting in a stepped structure in the transition zone between adjacent layers. The visibility of layer lines is influenced by the layer thickness: the thicker the layer, the more pronounced the step effect between layers and the greater the surface roughness.

The orientation of the printed part also affects the visibility of layer lines. On curved or inclined surfaces, layer lines are more pronounced than on flat surfaces, because in curved regions the boundaries of each layer do not align with the surface’s tangent direction, making the stair‑stepping effect more evident.

II. The Influence of Layered Structures on Bacterial Adhesion

Dental restorations and orthodontic appliances are exposed to the oral environment for extended periods, and their surface microstructure directly influences bacterial colonization. Studies have shown that lamellar structures may promote bacterial adhesion, as stepped surfaces provide bacteria with additional attachment sites and physical protection, making them less susceptible to removal by salivary flow or toothbrushing.

In the oral environment, bacterial adhesion is the first step in dental plaque formation. Bacteria tend to colonize and proliferate more readily on rough surfaces, potentially increasing the risk of dental caries, periodontitis, and peri-implantitis. This issue is particularly concerning for long‑term wear appliances, such as clear aligners.

III. Post-Processing for Improving Surface Quality

Although layer lines are an inherent characteristic of stereolithography, they can be mitigated through appropriate post-processing techniques. Studies have shown that post‑processing methods such as centrifugal coating can effectively fill the interlayer steps, significantly reducing surface roughness and decreasing bacterial adhesion. This approach works by depositing a uniform coating on the printed part’s surface, leveling the microscopic valleys between layers and resulting in a smoother finish.

Polishing also helps improve surface quality. Mechanical sanding removes protruding layer‑ridge peaks, reducing surface roughness; however, care must be taken to avoid over‑sanding, which can compromise the print’s geometric accuracy.

IV. Influence of Post-Curing Time on Surface Properties

Post‑curing time also affects surface wear resistance. An appropriately timed post‑cure can enhance the hardness of printed parts, resulting in a more wear‑resistant surface. However, over‑curing may render the material brittle, thereby increasing the risk of microcracking under stress.

During post‑curing, the surface polymerization reaction progresses further, increasing the crosslink density and, consequently, the surface hardness. A harder surface exhibits greater wear resistance in the oral environment and can maintain a smooth finish for a longer period.

V. Conclusion

Layer lines and surface roughness are inherent characteristics of stereolithography‑based 3D printing, arising from its layer‑by‑layer additive manufacturing process; in dental applications, they may increase the risk of bacterial adhesion. Layer thickness and print orientation are the primary factors influencing the visibility of layer lines. Post‑processing techniques such as centrifugal coating can effectively fill interlayer gaps, substantially enhancing surface quality. Post‑curing time also modulates surface hardness and wear resistance. In practice, the choice of post‑processing protocol should be tailored to the specific application’s cleaning requirements and wearing duration, striking a balance between surface smoothness and processing efficiency. For devices intended for long‑term wear, optimizing surface quality should be an integral part of the post‑processing workflow.

Disclaimer: The above content has been compiled from publicly available sources and is provided for reference only. If any infringement occurs, please contact us, and we will address it promptly.

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B-100M	Bisphenol A epoxy acrylate	Low viscosity, high hardness, high gloss, and high body.
B-113	Bisphenol A epoxy acrylate	High hardness, high gloss, high fullness, contains 20% TPGDA.
B-276H	Aliphatic polyurethane acrylate	High hardness, fast curing, excellent toughness, and low yellowing.
B-296	Aliphatic polyurethane acrylate	Fast curing, chemical resistance, yellowing resistance, impact resistance
B-296M	Polyurethane acrylate	Fast curing, resistant to polar solvents, yellowing-resistant, and impact-resistant.
B-301	Aromatic polyurethane acrylate	Fast curing, excellent toughness, and good sandability.
B-302	Aromatic polyurethane acrylate	Fast curing, high strength, excellent toughness, and good grindability.
B-368	Aliphatic polyurethane acrylate	Good toughness, excellent leveling, excellent bend resistance, and excellent heat resistance.
B-376	Aliphatic polyurethane acrylate	LED yellowing is minimal, and the nail polish formulation exhibits excellent stability.
B-609	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch resistance, and chemical resistance.
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BM3235 (PET3A)	Pentaerythritol triacrylate	Fast curing, high crosslink density, high hardness, and chemical resistance.
BM3380 (3EO-TMPTA)	Pentaerythritol triacrylate	More flexible and less irritating than TMPTA.

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Typical Issues in Dental UV 3D Printing (Part 6)

Typical Issues in Dental UV 3D Printing (Part 4)