Drinking a lot of alcohol, increases the risk of developing cancer of mouth, throat, tongue, lips and salivary glands.
If the heightened risk of developing oral cancer is not serious enough for anyone who drinks alcohol on a regular basis or to excess, the sugar and acidity of alcohol are major contributors to teeth erosion. As is the acid reflux which often accompanies vomiting, an all too common result of a night of heavy drinking.
Furthermore, more damage is caused if you stumble home and go straight to sleep after a big night out, only brushing your teeth the next morning. This leaves the mouth unprotected from erosion and decay all night.
Alcohol is also dehydrating. This affects the amount of saliva the mouth produces, and hence, how much protection teeth get.
Drinking lots of water both when out drinking alcohol as well as the next day recovering is one way to remedy the effects of excessive alcohol consumption, as is limiting the amount of soft drinks consumed.