Re: which is the most harmful to teeth, coke, diet coke or orange juice?

The pH of Pepsi is 2.5.  Diet Pepsi is 3.1.  The reason diets are
higher in pH is that aspartame degrades much quicker at a lower pH. The pH 
for OJ is around 3.4-4.0. This data suggests that soda and especially 
regular soda is potentially more harmful to teeth (but not by much). At a 
lower pH, the enamel on teeth is more rapidly broken down exposing the soft 
dentin tissue below to attack by microorganisms which ferment sugars found 
on teeth and secrete substances such as enzymes which attack and erode the 
dentin thereby "digging" a hole in the tooth or as we know it more simply 
the beginnings of a cavity.

Admin Note: the diet soda would probably have a reduced propensity for causing 
cavities because it lacks sugar, the food for cavity-causing bacteria.