Investors in Align Technology (NASDAQ: ALGN) have had plenty to be optimistic about. The orthodontics-maker has proven time and again its ability to continue to find new markets for its Invisalign transparent teeth-straighteners, and that growth has recently been accelerating. The company was among of the best performers of 2017, and it has returned a massive 60% so far this year.With that type of outperformance, investors will be looking for any cracks in the veneer when Align reports financial results for the 2018 second quarter on July 25, after the close of the market.