My understanding is there is a problem with high blood glucose and tooth decay.
When we have high BG, our body looks for ways to get rid of the excess glucose. The best known example of this is peeing - excess peeing is a symptom of undiagnosed diabetes.
When I was first diagnosed, I was upset ... until I discovered my tears were sweet rather than salty. Another example of my body trying to get rid of the excess glucose.
With this in mind, it is not a huge step to work out when our BG is high, there may be excess glucose in our saliva. And, as our dentists have always made sure we know, sugar rots teeth.
Hence, unmanaged high BG may leads to dental problems.
People with well-managed diabetes, should not experience dental problems.
... At least that is how I understand it and my experience since diagnosis (15 years ago) reflects this.