OP, yes, the PS is basically for "why you and why dentistry"
talk about that in WHATEVER way you want...and just make sure it is unique/stands out, not "oh, i like people and stuff"...adcoms know you like people and want to help..make it an original and interesting read
at one interview, i was complimented about my writing skills, but thats all she said, "you are a wonderful writer" ....didnt talk about specifics in the essay. dont know if that was good or bad actually.