Hi there!
I do not have any NextDent IBT, but I plan on ordering some very soon. I am doing a lot of experimenting with 3rd party resins though, so your post does intrigue me, and maybe I can help you try to trouble shoot a little bit. We might be able to help each other out! If you wouldn’t mind, please take a look at this resin settings spreadsheet I have created, and add your testing data to it. There is already a tab created for NextDent and the IBT resin.
Also, @VAZONE has experience with printing with NextDent materials so maybe he can weigh in as well.
So my first thought would be, if the grey setting isn’t giving the laser enough power, and the DentalSG works, but has curing issues, maybe you need somewhere in between. There is an old chart that shows which settings have which laser powers:
I think that one of the FormLabs moderators said that Flexible, High Temp, and Dental SG are to the right of all of those values on the chart (but not 100% sure on that). Maybe try Flexible or High Temp, OR get a Dental SG cartridge, empty it / use it all, fill your resin tank with NextDent IBT, put empty Dental SG cartridge into Form2 and print on Dental SG settings.
I am very curious to know how it turns out, so please post back your results!
-Kevin