How many mls of saliva does it take for someone to prevent tooth decay?

It Doesnt: Saliva in itself will not prevent decay. Saliva is the bodies natural acidic buffer. Saliva helps neutralize the erosive effects of acid on teeth as well as aid in the digestion of food. Lack of saliva (as in a side effect of radiation therapy) can lead to rampant decay.

Saliva can't PREVENT: Saliva can't prevent tooth decay, but its "absence" can promote it. Saliva contains bicarbonate--a buffer to the acids contained in foods, drinks and bacterial plaque. An acidic (low ph) diet will dissolve tooth structure when ph dips below 5.5. A healthy mouth exists at ph 7.2-7.4. Check your meds, break the sugar habits, check your gut (indigestion/reflux) and clean your teeth twice daily..

Not just saliva: While normal saliva-production is important for cavity control, proper hygiene with brushing and flossing is just as important. If you have dry-mouth syndrome, biotene products may help!