It's interesting to see customer stickiness mentioned above as...

It's interesting to see customer stickiness mentioned above as this was one of the factors I considered (probably not well enough) when buying SDI. I think SDI's particular stickiness has two limitations:
1. It only exists in certain markets where the purchasing agent (dentist) can gain by buying the product which he prefers to work without cost being a driving factor. I.e. not the South American amalgam market. Hence this part of the business is highly vulnerable to competitive pressure, has a declining cash flow and hence is difficult to value.
2. In the markets where stickiness does exist it serves only as a way of slowing customer migration and the lack of relative economies of scale probably does little to discourage larger competitors with existing sales teams in place. They will need to be vigilant to maintain their existing customer base.

Based on the above, the biggest question mark I now have is about the likely future growth of SDI's composite products as that appears to be a large driver of future value. If the current growth is coming from existing customers switching from amalgam to composite I would expect that eventually growth would plateau - but at what point? It would be interesting to know the difference in price between the two products and the rate at which the population of dentists using SDI composite fillings is growing or shrinking.