first Facebook ad campaign completely failed

If you're targeting dentists than why is your age range 23+? It should probably be at lowest 30 years of age.

Your campaign objectives matter a lot. On one hand you can use Facebook ads to build a fan page, which has long-term value, and on the other you can use it to get some quick traffic, which has short term value.

I'm guessing you spent your money on the traffic part. In this case you'd want to very carefully niche down to your target audience so that your ad isn't seen by people who aren't interested or don't qualify for your site.

You also want to segment your target audience, and run different ad sets for each audience. Facebook ads start with an overarching campaign, which consist of different ad sets, each of which has its own group of ads.

The beauty of this is you can separately schedule ad sets. So if segment A of your audience only looks at Facebook in the morning, and segment B in the evening, then you can schedule ad set A in the morning, and ad set B in the evening.

With each ad set, try different variations of the ad. Use different images and ad copy. Facebook will automatically optimise for the one that performs best.

An alternative to driving traffic to your site, as I mentioned earlier, is to create a fan page and use fb ads to increase likes. You can then post interesting material to the page and engage your audience. Once you build trust with them they'll sign up on your site and start sharing your content with others.

I've explained all this in detail in this post - Facebook Ads for E-commerce: Getting Started | Open a Store Now

Give it a quick read and if you have any questions, feel free to ask. If you use fb ads correctly, you can really benefit a lot for very little cash.

Good luck!

"First campaign failed" shows that you might have the wrong approach. You can say that it failed only until you've kept trying different things for a while. Try to build on the things that seem to work.

Having said that Facebook might be a hard platform to use for B2B marketing. I'm sure many do, but especially those little ads in the right-hand side are invisible for the user and always full of consumer products. People are not surfing it as professionals, but for goofing off with their pals.