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Isopropyl alcohol (IPA) is the go-to solution for washing 3D printed dental devices, yet for a range of reasons it is far from ideal. So, are there alternatives and if so, why aren’t we using them? By Dr Andrew B Cameron and A/Prof Joanne Choi
Our interest in the critical role of the post-washing phase with isopropyl alcohol in 3D printing began in 2019. While producing surgical guides in our training programs, we observed materials shattering after undergoing an autoclave cycle. After investigating the likely causes, it was found that students were leaving the surgical guides in isopropyl alcohol (IPA) for too long during cleaning. This compromised the material properties, an effect that was further exacerbated by the high temperatures of autoclaving. This outcome underscored the importance of adhering to the manufacturer’s instructions during the washing step in 3D printing, and how it can impact the final application. As researchers, it also sparked our curiosity.
You’re soaking in it
We have now explored this phenomenon across several research projects.
In collaboration with The University of Otago and Griffith University, we designed a study to test how 3D printed crowns bond after being left in IPA for varying durations: twice the recommended time (10 minutes), over lunch (one hour), and overnight (eight hours).
The results of this study were alarming. Leaving the crown in for twice the recommended time was fine. However, if the crowns are left in IPA for an hour, the bond strength is halved while eight hours of immersion results in even less bond strength.1
A similar study on 3D printed denture bases at Griffith University showed that the same principle applies to this material’s strength. Flexural strength remained stable when the material was washed for the recommended time or even doubled. However, leaving the material in IPA for 90 minutes caused significant variability in strength, and an eight-hour immersion drastically reduced it.2
The results of these studies are not isolated. We also conducted a detailed search of other studies known as a systematic review.3
This summarises the findings from all dental research examining how washing time and the choice of cleaning solution affect 3D printed parts.
The 34 studies that investigated 3D printing post-processing indicate that:
• Post-washing duration should be short (5–15 minutes). Longer than this will have detrimental effects on the material properties.
• Moderate heating (30–55°C) is optimal for enhancing washing efficiency.
Implications
So, what does this mean for your dental laboratory or clinic processes? If a 3D printed part is left in the post-wash solution, it may be tempting to use it anyway. However, if the washing time exceeds twice the duration recommended in the instructions, it’s best to reprint the item. Keeping the materials that have been over-washed—if they are biocompatible in nature—may compromise their long-term durability in the mouth.
Heating the washing solution has been explored as a method to improve the process. Consider washing dishes: hot water works better than cold. The same principle applies to post-washing 3D printed parts. However, because IPA is highly volatile, heating can raise safety concerns and increase evaporation. Still, if you work in a cold climate or during winter and notice reduced washing quality, temperature may be the reason.
But what if the material isn’t used intraorally, such as for a model? Studies show that prolonged immersion in IPA can still affect the model’s hardness and cause dimensional inaccuracies.4,5
Scientific studies have shown that IPA is an aggressive inorganic washing agent.4,5 Its effect on surface characteristics occurs because it can strip away the top layers during washing.6 This means that if a crown fits too tightly on a 3D printed model, it could be due to warping or reduced hardness of the model caused by IPA exposure, leading to wear at the contact points during laboratory handling.
Possible alternatives to IPA
We’ve wondered why manufacturers of 3D printed devices have chosen IPA as the washing solution. It likely comes down to its effectiveness: IPA’s volatility allows it to dissolve uncured photopolymers faster than other solutions.
There are potential alternatives to IPA such as tripropylene glycol monomethyl ether (TPM) or propylene glycol (PG) which are less aggressive. TPM and PG are chemically different in nature to IPA.
A big advantage of TPM, for example, is that it evaporates slowly and is non-flammable. Using TPM can reduce material waste, and from a workplace health and safety perspective, it creates a safer environment.
Solutions containing propylene glycol offer the same benefits as TPM, with a study showing that the final surface finish and hardness are comparable to those achieved with an IPA wash.6
These alternative washing solutions should not be used for biocompatible 3D printing applications unless they are recommended by the manufacturer. If research shows that these solutions match or improve the accuracy, mechanical properties, and biocompatibility of dental devices, manufacturers should take note—updating their instructions for use or considering them as post-washing options when developing new materials. For dental models, they should also be considered as viable alternatives in commercial operations.
Stay tuned in this space. We have several other investigations underway that should start to answer these questions of whether alternative washing solutions are fit for use for intraoral devices. If alternative washing solutions are proven effective, manufacturers could use this research to help dental laboratories and clinics adopt safer, more efficient, and environmentally friendly post-washing protocols. ∞
Dr Andrew B Cameron and A/Prof Joanne Choi both work in the School of Medicine and Dentistry at Griffith University.
References
1. Kagaoan, Z., Liu, X., Cameron, A., Aarts, J., & Choi, J. J. E. (2024). Prolonged post-washing in ethanol decreases bond strength of additively manufactured crown materials. Journal of Dentistry, 144. https://doi.org/10.1016/j.jdent.2024.104873
2. An, S., Tazikeh, M., Sa’Oor, S., Wang, T., & Cameron, A. (2025). Impact of isopropanol post-washing duration and post-polymerization devices on flexural properties of 3D-printed denture base: An in-vitro study. Digital Dentistry Journal, 2(2). https://doi.org/10.1016/j.ddj.2025.100020
3. Xiaoxia Wang, John M. Aarts, Nicholas C.K. Heng, Andrew B. Cameron, Joanne Jung Eun Choi (2026). Influence of different post-washing parameters on the properties of additively-manufactured dental devices – A systematic review, Journal of Dentistry,Volume 165,106315, https://doi.org/10.1016/j.jdent.2025.106315.
4. Mostafavi, D., Methani, M. M., Piedra-Cascón, W., Zandinejad, A., & Revilla-León, M. (2021). Influence of the Rinsing Postprocessing Procedures on the Manufacturing Accuracy of Vat-Polymerized Dental Model Material. Journal of Prosthodontics : Official Journal of the American College of Prosthodontists, 30(7), 610–616. https://doi.org/10.1111/jopr.13288
5. Katheng, A., Kanazawa, M., Komagamine, Y., Iwaki, M., Namano, S., & Minakuchi, S. (2022). Effect of post-rinsing time and method on accuracy of denture base manufactured with stereolithography. The Journal of Advanced Prosthodontics, 14(1), 45–55. https://doi.org/10.4047/jap.2022.14.1.45
6. Lambart, A.-L., Xepapadeas, A. B., Koos, B., Li, P., & Spintzyk, S. (2022). Rinsing postprocessing procedure of a 3D-printed orthodontic appliance material: Impact of alternative post-rinsing solutions on the roughness, flexural strength and cytotoxicity. Dental Materials, 38(8), 1344–1353. https://doi.org/10.1016/j.dental.2022.06.010
