Not really sure, that's one of the things I've been researching ... like what stringing material would work well, be natural and not break, of course.
My inspiration for the wooden teether came from this really cute Haba teether I found for DS at the local Sciencecenter. It is half wooden ring and half cylindrical rainbow beads, all wood. I believe it's on some kind of elastic band so the beads can move around a lot. I'm not sure where to get that type of thing ...
As for splintering ... I have to say that I would expect considerable and visible wear on a wooden teether before it splintered. Probably something that should be checked each day before it is given to the child.
So, I really like the wooden ring ones, I already wrote to a manufacturer today to ask about theirs being non-toxic, etc. DS also really likes the beaded kind, but I'd prefer to give him something natural vs. the plastic ones we find in the store.