Novamin is caught in a classic consumer product study quagmire. It's a proprietary, IP-wrapped solution. This leaves extraordinarily few people with an interest in proving its efficacy. Who is going to pay to study it? And the answer is that only people with a strong financial interest in its effectiveness are willing to study it, and those studies have little credibility due to bias.
The vast majority of consumer products you use have no peer reviewed research behind them for the same reason.
But we know its method of function, and the theory behind its operation. People using the product often find reduced sensitivity (I went from really bad sensitivity to no sensitivity) and a whitening effect. Eh, good enough for me.
And it's interesting that this submission is about a product that has a virtually identical method of operation - calcium and phosphorous ions.