Firstly, a huge congratulations for completing your examinations and the good grades!
However I would be frank that I do not know much about the admission criteria, especially for international schools, as the final decision lies with the NUS admissions website (which I assume shortlists applicants based on a bell curve system)
But i would agree with you that they tend to take the higher score, so most likely your Bio would be taken into account instead of your physics grade.
Whether or not you get into the dental course ultimately depends on the Manual dexterity test and the Multiple mini interviews as further elaborated on in the post. And the decision lies in the hands of the interviewers.
Definitely worthy to highlight the achievements and passion you have towards dentistry during your interview though!