Modern materials are very tough. Depending on how well the string is made, it can be abrasive. Also, the way the string grooves are cut will make a difference.
Basically, you want as little friction on the limb tip as possible. This is where the string construction and angle of the string groove comes in.
You want the material the string contacts to be tougher than the string. That's where the overlays come in.
Some folks have gotten away with modern materials on bows without overlays. Some haven't. I haven't tried it myself--I don't have a bow I'm willing to risk damaging.
Even if I did, one bow won't tell the tale. One might survive, the next might not. One might break, but was it the string or something else? I've broken a lot of bows and heard of a lot more that never had anything other than a Dacron string on them.
I remember back when PENN 66 and B-75 came out. Some people loved them and had great results. Others ruined bows. I posted concerns on a different site (this was before TG existed) and was called pretty much everything but smart and honest for it. Funny thing...none of those people ever apologized when both materials were taken off the market, for the very reasons I had posted about.
Short answer: anything other than Dacron might damage your bow.
Chad