hobby-grade printers and validated workflows

[ecotan]

If a workflow is validated by a manufacturer (e.g., KeyPrint KeySplint Soft),is there any difference in terms of product safety (specifically biocompatibility) when it comes to which printer and wash/cure station is used? The Elegoo Mars 3 Pro for example is extremely affordable, and so is the Mercury Plus wash/cure. Both have validated workflows. The Phrozen Mini 4K is also listed along with the Phrozen wash/cure (and seems to be popular on this forum) but that printer is discontinued, and the Phrozen Mini 8K is not validated yet.

The build platform, resin vat, and non-stick liners are components that will touch and interact with the resin. Do these have an impact on the cured resin? Do they release any chemicals? I can't think of anything else, outside of consistency of LED lights that will impact the end product in terms of biocompatibility.

I have very low volume production so the Elegoo Mars 3 Pro or Phrozen mini 8K, (if it was validated) for example will be ideal.

 

[Car 54]

I don't know if this has anything to do with what you're looking for (denture resins) but just thought I'd post it anyway.

Phrozen Sonic Mini 8K S

So I finally repaired my printer..I had spilled resin down the side and took it apart to clean it out. Instead of taking it apart from the bottom (I now know better) I took the top off and in putting it back together, crimped the MOBO to LCD screen ribbon cable. Phrozen was good about making...

dentallabnetwork.com

 

[Foggy_in_RI]

Some build platforms are made with a metal that does not work with a biocompatible workflow.

 

[ecotan]

Some build platforms are made with a metal that does not work with a biocompatible workflow.

Would that be considered when a manufacturer is validating a workflow? That is what I am unsure of. How trustworthy are the validated workflows in terms of looking at any possible contamination? On the other hand there is no "biocompatible" certification for printers (with few exceptions perhaps).

 

[tuyere]

If it's validated and you follow the proscribed workflow with the proscribed equipment, it's fine. That's the whole point of validation, these questions have already been asked and answered by the manufacturers. The components used across all printers are pretty uniform in composition because everybody's subject to the same manufacturing and mechanical pressures- all the build platforms are aluminium because it's straightforward and cheap to die-cast to form and then fly-cut the face for finish and parallelism, almost all the resin cassette bottoms are FEP or NFEP because it's cheap, inert, tough and highly nonstick, etc. $500 printers are largely like $25000 printers in this regard, it's doing it this way or reinventing the wheel. Carbon did that, but they're an outlier in several ways, and it comes with a lot of drawbacks (extremely expensive resin cassettes with a delicate bottom coating, for example).

Some build platforms are made with a metal that does not work with a biocompatible workflow.

Do you have a source for this? Basically everybody uses aluminium for build platforms- I actually can't think of a counter-example. Wait, I think the rapidshape has a stainless build platform? But that's a major exception, and it's a weird design that others don't follow for straightforward reasons. It's assembled from machined parts, which is more expensive, labour-intensive and finicky than the one-piece machined castings that are otherwise preferred. There's also at least one zirconia build platform coming out intended for use with nanoceramic resins, but that's not an issue.

 

[Foggy_in_RI]

Thats an interesting question. Besides the 1-way and 2-way validations much of what I describe below is based on my interpretation and could be incorrect.

There are two types of validations taking place in the market today: 1-way validation and 2-way validations.

1-way validation is when a printer company "validates" a manufacturer's resin without the manufacturer's involvement. These are sketchy at best because there are no guarantees the resin company is not going to change something that would change the results from the printer. Additionally, 1-way validations means that the resin manufacturer is not on the hook for any downstream issues (adverse events) as you did not follow their IFU which should include validated printers. You and the printer company will have a good time finger pointing but at the end of the day if YOU the user violate the IFU of the resin who should be responsible?

2-way validation involves both the printer and resin manufacturer under an agreement that requires both entities to inform each other of any changes that would influence the result from the printer. With 2-way validation, if you have any issues downstream issues (adverse events); provided you followed the defined steps in the IFU the liability may be pushed back to the resin manufacturer (likely).

1-way and 2-way validation applies to the wash and curing systems as well.

 

[Foggy_in_RI]

If it's validated and you follow the proscribed workflow with the proscribed equipment, it's fine. That's the whole point of validation, these questions have already been asked and answered by the manufacturers. The components used across all printers are pretty uniform in composition because everybody's subject to the same manufacturing and mechanical pressures.



Do you have a source for this? Basically everybody uses aluminium for build platforms- I actually can't think of a counter-example. Wait, I think the rapidshape has a stainless build platform? But that's a major exception, and it's a weird design that others don't follow for straightforward reasons. There's also at least one zirconia build platform coming out intended for use with nanoceramic resins, but that's not an issue.

Formlabs needed a special build plate if you wanted to print their Temp and Crown resins.

 

[mightymouse]

Last time I checked as long as the resin is a Class 2a biocompatible FDA approved resin validated for a particular printer and curebox and you follow the manufacturer instructions your doing what is required.

Other than that there is not much we control it’s really up to the companies and the FDA. We just have to follow the instructions to a tee. Whether or not the resin and printer companies did a thorough job or the person approving at the FDA didn’t just approve it for the sake of going home faster it is out of our control.

Kind of like when the president visited Flint, Michigan during the water crisis. Took a glass up to his lip but never saw him swallow. Unfortunately we have to trust everyone is doing their job and not BS-ing us.

 

[tuyere]

Formlabs needed a special build plate if you wanted to print their Temp and Crown resins.

That's interesting, I haven't seen that with any other printer manufacturers. Form printers are odd birds with a weird curing mechanism, though, and to the OP's question, not really representative of the printers in question- cheap hobby printers are 100% LCD designs, so far as I know, and the design + conventions of those are essentially standardized because it's such a thoroughly-solved problem. Those all have anodized aluminium build plates, anodized aluminium or polyethylene (I believe) resin trays, and FEP/NFEP tray membranes. All pretty inert, as far as resin is concerned, which is pretty non-reactive outside of the whole "desperately wanting to crosslink, just give me one hit of UV light, just a taste, you know I'm good for it" thing.

If I have any real reservations with biocompatibility/resin safety, it lies in
1) the rigor of the validation processes being used by the manufacturers. I don't trust businesses to actually protect the health and interests of patients + techs if they're left to self-regulation, if doing so costs a little extra; and
2) the poor adherence of many labs to validated workflows- there are a whole lot of untrained techs following inconsistent, half-communicated protocols out there.
It's up to us to address 2, but 1 is just so far outside of our wheelhouse you end up kind of hopeless. It definitely gives me pause when it comes to permanent/long-term restorations, and everything else being equal, I encourage people to go for conventionally-manufactured appliances wherever possible. Although the superior mechanical performance is the bigger driver there, I think, printed restorations are Not Great for patient outcomes, taken as a whole.
I'm rambling now, what was the OP about again?

 

[tuyere]

One qualifier to the above: AFAIK all aluminium build platforms are anodized, but cheaper hobby ones often do not have the fly-cut build plate surface re-anodized after machining, so that surface is softer, non-anodized aluminium from the core of the plate. They're easier to scratch, for one, but they're also prone to abrasion from highly-abrasive tools or resins, which is a concern for Rodin-type nanoceramics. The aluminium oxide that can get liberated looks black- you'll see it on cleaning cloths rubbed on the build plate during cleaning- and can change the colour of resin in the trays when reused, which is why Rodin stresses not reusing any resin on the models or on the plate once you've used a scraper to pop the print off. I don't know if it impacts biocompatibility, beyond the appearance impact, but it's still important to not introduce it into the resin volume to be safe. Squeegee as much off the platform + parts as possible using a soft silicone spatula, that stuff is fine, but not once you've scraped the plate with hard tools.
There is some concern about longer-term abrasion of soft build plates from the pressurized flow of resin being squeezed repeatedly between cassette bottom and build plate, which is why people are experimenting with zirconia-faced build platforms, it's far more abrasion-resistant than aluminium, and any abrasion isn't contaminating the resin. It's still very early days for these.
Rodin has approved its resins for Phrozen printers, which may have the non-anodized build face issue. I can only assume they've wrangled with the complications of this, with their conclusion being to discard 'scraped resin', but the longer-term effectiveness of this in preventing contamination is... unclear.

And oh yeah, build platforms that are hard-anodized after machining are much more resistant to this abrasion + contamination. More expensive dental printers largely have these build platforms, it's where all that extra purchase price is (in part) going. I've been told by a printer tech that it's less of an issue to reuse scraped resin with these, but I still ask our techs to discard it regardless.

 

[ecotan]

> That's the whole point of validation, these questions have already been asked and answered by the manufacturers.
This makes sense. I guess it is either a matter of trusting those validations, or asking for more concrete documentation to back the claims up.

> Last time I checked as long as the resin is a Class 2a biocompatible FDA approved resin validated for a particular printer and curebox and you follow the manufacturer instructions your doing what is required.

The resin I mention is indeed class IIa. It's hard to find information about what goes into a "validated workflow" with respect to what documentation or standards have to be met in order to make that assertion for each specific device combination. Outside of the print/cure parameters, there isn't much information about this.

> AFAIK all aluminium build platforms are anodized, but cheaper hobby ones often do not have the fly-cut build plate surface re-anodized after machining

The Elegoo Mars 3 Pro does indeed have FEP lining, and anodized aluminum resin tank and build platform, although the build surface is raw/shiny aluminum as you described. I won't be using abrasive resin, though interesting to think of liberated contaminants that may affect the resin. I would assume that this is already factored into the biocompatibility testing though? I suppose I could clean the surfaces with soap/water to try and reduce that particular type of contamination, and not use abrasives.

> 1-way and 2-way validation applies to the wash and curing systems as well.
I assume that since this claim of validation is coming from KeyStone, then it is a higher level of standard than if it was just the printer manufacturer.

 

[rlhhds]

My thought if we stick with validated equipment and processes it shouldn't be any worries for us. The manufacturers did all the legwork developing these systems and getting approval from the FDA. So if we follow the IFU's we have done the best that can be done with the processes developed for us.

 

[Car 54]

Another Bookmarked, informative thread.