chrisains - 5:03 pm on Jan 26, 2011 (gmt 0)
You have kinda answered your own question, as you have the list of URLs therefore you know where the duplication is coming from ;-)
Parameter driven URLs can be seen as a form of duplication by search engines, for example...
...although these are technically the same HTML page (endodontics-c-8.html), a search engine will see the parameters as separate URLs therefore causing potential duplication issues.
In this case it looks as though the duplication stems from refinement options on the page, for example "order by price", "order A to Z" and such like, which cause the parameters to change.
How bad is it? Well its not brilliant that's for sure - Zen Cart is well know for being non-search friendly. But it depends on the context of the page and what you are trying to achieve. I would always advise trying to minimise duplication where possible.
How can it be fixed? Depending on the context of the page you may wish to try implementing the canonical tag - [googlewebmastercentral.blogspot.com...]
This may help in the short term, but it is not a directive which is currently followed by all search engines.
Long term you should look at rectifying the root cause of the duplication, the architecture of the website, to avoid duplication.