3D-printed aligners: need for specific cleaning protocols

Dental Tribune International

Thu. 5 June 2025

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ZAGREB, Croatia: As 3D-printed aligners gain traction, many patients and clinicians continue to apply cleaning routines that were originally developed for thermoformed appliances. However, this may be compromising aligner performance. A recent study by researchers at the University of Zagreb has investigated how common cleaning methods affect the physical and aesthetic properties of 3D-printed, polyurethane-based aligners. According to the authors, the findings underscore the importance of developing cleaning protocols that are specifically tailored to the unique properties of 3D-printed materials.

The researchers highlighted that surface roughness promotes bacterial adhesion in aligners and that patient hygiene practices and aligner material properties influence biofilm accumulation. Bacteria frequently detected on aligners include Streptococcus mutans, Lactobacillus species and Porphyromonas gingivalis—microorganisms known to play a role in the development of various dental conditions.

A total of 84 specimens made from polyurethane were produced using digital light processing and allocated to three groups based on different cleaning methods: brushing alone, brushing with toothpaste and soaking in an alkaline denture cleansing solution. Each method was used in a two-week daily cleaning routine that simulated a single phase of aligner therapy. A total of 42 specimens were evaluated for the physical and aesthetic properties of surface roughness, hardness, colour change and water absorption.

The researchers found that mechanical cleaning—especially with toothpaste—markedly increased surface roughness and hardness, potentially affecting comfort, plaque accumulation and wear resistance. In contrast, chemical cleaning with the denture cleansing solution maintained smoother surfaces and slightly reduced hardness, suggesting a gentler effect on material integrity. No significant differences in total colour change were found between the cleaning methods; however, the two brushing protocols altered surface reflection, which may reduce optical clarity.

Water absorption was measured daily in aligners immersed in a denture cleansing solution or saline over 14 days and varied notably between the groups. The saline-exposed aligners expanded steadily over time, potentially affecting fit. Immersion in the denture cleansing solution led to higher absorption initially, followed by a decline, indicating material degradation and raising concerns over long-term material stability.

In discussing the results, the authors observed a need for cleaning protocols that are material-specific and preserve stability and surface characteristics. The cleaning methods used in the study significantly affected the surface properties. These changes, though occurring over a short wear period, highlight the clinical relevance of cleaning protocols. For 3D-printed aligners, combining mechanical and chemical cleaning may offer the best balance between hygiene, appearance and material preservation.

The study, titled “Impact of various cleaning protocols on the physical and aesthetic properties of 3D-printed orthodontic aligners”, was published online on 30 May 2025 in Scientific Reports.