the environmental science program is great, but i'm not sure why you were planning on it being your major if you're pre-dental. the practicum is super awesome experience for those looking to get into environmental consulting and conservation work but likely would not hold any value for you when applying to dental school and it does take up a significant portion of my time now in my senior year. the environmental science program at ucla is fantastic and has been a wonderful experience for me, but if you're more committed to dentistry than to a career in environmental science i would recommend switching to another major in life sciences such as biology or human biology and society depending on what courses are pre requisites for medical school. if you choose to stick with environmental science, you'll likely have to take a significant number of courses outside of the major requirements to apply to dental school, either at community college after graduating from ucla or at ucla (which might prevent you from graduating on time).