Is Bellafill best used before or after an Infini microneedling treatment?

I do Bellafill the same day as Infini for the rolling acne scars. I skin test all patients prior to Bellafill, so the first session is Infini and skin test. The second treatment will include subcision with cannula if needed and then injection using a 23g cannula deeply and needle superficially. I treat the Infini as a sterile procedure so there is no concern regarding infection. The melting point of PMMA is 160C and Infini heats only to 65-70C. There is no need for the collagen in the Bellafill other than to act as a carrier for the PMMA spheres. There was a study by Dr Lim who showed the Infini does not affect HA or calcium hydroxyapatite fillers. I believe that acne scars much be treated with multiple modalities for best results. Volume loss must be replaced with fillers. 

Great question and one we've discussed at some length when we train other docs in out BellaDiamond office.  The answer we've come up with is a bit complex, so bear with me.
Bellafill is a two component system: about 6 million spheres of Poly Methy Methacrylate, suspended in a cow collagen gel, per syringe.  I agree with the other docs, that the melting point of PMMA is higher than the resurfacing energies being used, and it's basically inert.  
However, the cow collagen carrier gel can cook!, if its close to the 1-3mm depth that most microneedling devices drive down into the tissue.  Also, we treat Bellafill injections as a semi-surgical procedure since we are putting a long lasting IMPLANT into the tissue.  We keep the skin surface VERY clean/sterile before, during and after the procedure to prevent microfilm infection which are tough to diagnose and difficult to treat....
Because Bellafill is FDA approved for at least a 5 year duration of action, as some of the docs have mentioned, there's no reason to provide two great procedures at the same time.  Let your body absorb the cow collagen and then do the microneedling weeks later, or do the microneedling and let all the holes seal and inflammation go away before placing a material that may cause inflammation (cow collagen) into the superficial tissue-especially when we inject Bellafill into the dermal/epidermal junction to help correct acne scars.
Finally, If you are doing a series of RF microneedling, you may "shrink wrap" the skin enough over time to need a little less filler, but volume is still important in almost every facial aesthetic enhancement.
Hope that helps~  Z