Something that I forgot previously. Xylitol and Erythritol are worth checking out IMO. They help increase healing of teeth and tooth enamel. Erythritol is meant to have a stronger effect than Xylitol.
Putting some of the crystals inside your mouth and allowing to mix with saliva and wash around the mouth to increase the restoring effect to the teeth. Hopefully, saliva contains the required nutrients to repair the teeth and those Sugar alcohols increase the deposition of the nutrients to the teeth. It does tend to increase hard plague in some places but you cannot have the benefits without the negative side while the harmful bacteria exist. More of a reason to seek to destroy them IMO. Which brings things back to those oral probiotic bacteria again. Altering the oral bacterial terrain can help a lot to reduce decay while fortifying the nutrients should provide what is needed to heal the teeth.
That's the theory anyway but as I said, I have a lot which is working against me ATM.