Has a guideline been set for the optimal pH level in the mouth?

My thought is that improper pH might might be a factor in bacterial growth and tooth decay. Supporting the idea is this research summary that implicates low pH (high acidity) to Fluorosis.

Notes:

Since posting this I have become convinced that this is a thing so I have added some baking soda to my fluoride mouthwash to raise my oral pH (lower the acidity) and prevent fluorosis.