Can you figure out why are some of my pages not indexed by Google?

I checked everything and I don't know why all the articles on my site are not indexed by Google: http://dentistfind.com/dental-health

Everything else on my site is indexed and even the category pages from the blog but not the blog article pages. It baffles me. I have tried looking into the robots.txt file.

Can someone figure it out? I know there is a simple solution...

Try the following, if you're referring to those articles on the blog:
http://dentistfind.com/7-signs-that-you-need-to-see-a-dentist

Try to get more backlinks to this page: http://dentistfind.com/dental-health
So google spiders all the links on it.

Create an xml sitemap and submit it to Google wemaster tools

Optional: Add meta tag description to each article page.

You can also add the rel publisher, rel author and those tags.

Hey jingCo looking at your site the first thing I notice is that you have a permalink structure that i've never seen.

On the home page hovering over the articles dropdown then let's say teeth-whitening you get this link
http://dentistfind.com/dental-health/category/cosmetic-dentistry

Now on that category page you get this for the only article on the page
http://dentistfind.com/avoid-tooth-sensitivity

I'm wondering if you're rewriting the urls in htaccess or something?

kindly suggestion IMO only
1: 500 error on your article pages displayed on http://dentistfind.com/dental-health/page/7 as well as http://dentistfind.com/dental-health/page/6. you are using NGINX type web server, try to checking your log to see how many times Google robots encountered the 500 error.
2: too many pages with short header title, as well as empty description. no meta keywords listed is fine. But I think the appropriate title and description in tag head is necessary. especially for your article page.
3: the html of your site contains so many js/css, along with images, more than 20 http requests. in a nutshell, follow yslow or google page speed guideline to optimize it.(I don't think it prevent Google to index your page

try to use your server log or any other web traffic analytic tool that could see how/when search engine spiders to visit/crawl your pages....although crawl doesn't mean indexing. but it helps us to figure the reason out.

you has the articles posted in 2011. are they never indexed? the major Google updated Penguin really kicks many pages with spam contents(in G eyes out of their index.

hope those information is helpful.

create some quality backlinks with related site. also add your site in google webmaster tool. do social bookmarking. Ping Your site after publishing any article. also check that no one is copying your content.