Should Mt Gambier flournate there water supply?

Yes fluoride improves strength of children's teeth

BUT:

fluoridating the water supply is a poor way to achieve this as many people drink bottled or filtered water so all that fluoride is being used in showers, gardens etc.

better (and cheaper) to provide free fluoride tablets to all school children (fluoride doesn't work on adult teeth). Even better: put it in soft drinks so the people with highest risk get the most fluoride!

Flouride is very important for tooth development in children and young adults. EPA says a flouride concentration of one milligram per liter is the optimal dosage. If your municipal water supply flouridates the water--it needs to monitor the concentration closely because prolonged use of water with "too high" concentrations of Fl can be harnful to the teeth. Excessive Fl will cause mottling (melting of tooth enamel). Most municipalities with over 5,000 water connections are required to Flouridate by law---smaller municipalities have the option of voting rather to flouridate or not.