I've started doing OP with olive oil (since that's all I have atm). So far I've only noticed fresher breath and a polished feel to my teeth after I brush. I've also switched from toothpaste to baking soda (sometimes mixed with salt). I noticed that it leaves my breath fresher longer than if I were to use the toothpaste I've been using. Also replaced my mouthwash with hydrogen peroxide.
I initially added a drop or two of neem and lavender to to the olive oil but I'm thinking now less is more. I also found some information on neem oil can cause infertility over a period of time (http://voices.yahoo.com/benefits-herbal-toothpaste-8201217.html?cat=5). If you look further though, there's information online where neem oil can be used as birth control (http://www.sisterzeus.com/neem.html). The infertility seems to be reversible, however, women who're pregnant should be forewarned.
Info on Neem as birth control:
http://www.discoverneem.com/neem-oil-birth-control.html
http://oneearthherbs.squarespace.com/important-herbs/neem-leaf-oil-azadirachta-indica.html
http://www.neemfoundation.org/neem-articles/neem-in-health/neem-cures/birth-control.html
The reason I was interested in natural toothpaste is because I felt that my regular toothpaste wasn't doing it for me. I also knew this guy who said he knew people who brushed throughout the day and still had bad breath, which is also kind of the case for me. So I'm hoping a natural alternative will be better.
What I've learned so far is that natural toothpastes are just as effective, if not more so, at killing bacteria as regular toothpaste. And since it's natural, it doesn't have the chemicals regular toothpaste has. So if you're interested, check it out.
http://www.dailymail.co.uk/health/article-34857/Should-use-herbal-toothpaste.html
http://www.yunadent.com/blog/herbal-toothpaste-vs-regular-toothpaste/
http://www.sooperarticles.com/health-fitness-articles/dental-care-articles/benefits-herbal-toothpaste-97104.html
http://bondibeachdental.com.au/dentist-bondi-blog/benefits-of-herbal-toothpaste/
http://www.wired.co.uk/magazine/archive/2009/10/how-to/how-to-make-ayurvedic-toothpaste
http://www.rdhmag.com/articles/print/volume-32/issue-2/columns/ayurvedic-toothpaste-perio-diagnosis-and-colored-handles.html
I've been looking at the bondibeachdental and they have some good teeth whitening remedies that you can try out.
It was mentioned somewhere that OP can cause gagging for some. I learned from a friend that if you clench your left hand in a fist it'll reduce the urge to gag. I've tried it and it works for me.