Chipped sand dollars can be easily repaired using any of the different file types shown below,
finger nail file, hand held sanding pads work well as do rotary tools such as Dremel.You can
even rub the edge softly on a concrete floor, it works really well if you are careful.
Hint: If you sand on one edge sand on the opposite edge of sand dollar also.
If you have a rotary tool you can even change the shape of the sand dollars as pictured below.