I have an idea for a mouth rinse I would like to patent. When performing a quick Google search, I found several patents that seem to have overlapping claims with each other. My patent would likely overlap as well. The question is why has the USPTO granted subsequent patents that seem to overlap with the prior ones. Here are two example patents:
From 1991: http://www.google.com/patents/US5089255 - covers a mouth rinse with xylitol
2008: Publication number: US 2006/0286044 A1 - covers almost any delivery vehicle for xylitol, including mouth rinses!
Can you provide some clarity on what is and isn't allowed/patentable?