I've just had some work done in the Phils so I thought I would offer my opinion.
I was quite lucky in that my mahal's mama knew a dentist quite well (it was a surgery in Laguna) and I had a large bridge done for a total of 18,200 PHP. This included the price of the bridge, all work, well everything.
By comparison, the cost in the UK - I never found out because the consultation fee was £95.00 alone (half the cost of the treatment in the Phils).
Am I happy wth the work? YES!!! It was superb. I had 2 temporary bridges built while my gums healed (I needed an extraction which was surprisingly painless because of the dentists skill - she had me humming Beatles tunes while it was taken out!), and the final fits almost like a glove (still some healing to do which will take time). The final fitting was done by an orthodontist and he really took a lot of effort to make sure that a) it was clinically sound, and b) it looked good. Unlike UK dentists, Filipino dentists consider the appearance of teeth to be important.
From now, I think all my dental work will be done there - the money saved pays me to visit. But the important thing is that my gums are healed well, my smile is improved by several hundred percent (my fiancee now makes fun of me smiling all the time!), and it worked out cheaper to visit my mahal and have the work done there than have it done in the UK and stay at home.
Obviously, try to find a good dentist - your mahal should be able to help here and if not, try to find one with a good reputation.
Best of luck!