For MOST schools... Prereqs must be done prior to the summer of matriculation.  However, it seems not all are so kind, 
"
  A minimum of 3 years college course work completed in a U.S. or Canadian college or university is required. To  be considered, an applicant must have documentation certifying  completion of a minimum of 90 semester credit hours at the time of  application.
       The college work must include:
                English Composition & Rhetoric             6 hours
               Biology or Zoology (with Lab)                 8 hours 
               Inorganic Chemistry (with Lab)                8 hours
               Organic Chemistry (with Lab)                  8 hours 
               Physics (with Lab)                                   8 hours
  These are firm requirements regardless of undergraduate or graduate preparation."
that is from WVU dental school.  So do not apply there.  
Good luck!