No, getting a Master's in OT takes 2 years (plus an additional year that it takes to apply and wait). If dentistry is what you want to do, going the OT route doesn't really show commitment to the dental field. If you are thinking about OT vs. dentistry, then that is totally up to you as to what is a better fit.
You can improve your application by making yourself more competitive in grades (taking advanced science classes through a post-bac or a Master's), improving your DAT scores, working on getting better letter of recommendations, and spending time in extracurricular activities.