Aggressive older cat

Question
In the last two months, a male cat that I rescued about6 years ago and that gets along and even mentored some other rescued cats has attacked my younger cats that it mentored.  This male is neutered but has had a history of dental problems.  This cat has fought dogs, raccoons, and other bigger tomcats.  A tough cat but loves people.  The attacks have been stalking and would be vicious if intervention not used.  Spray bottles and all just deter for the moment.  I rescue cats, but this behavior has disrupted all of the rescued cats.  If I cannot stop the behavior, I may have to euthanize the cat, which is about ten to 14 years old.  At wits end and seemingly no options!

Answer
William,

Have you had the cat to a vet to check to see if there are any medical problems that might bring on this behavior, e.g. the thyroid being out of kilter?  Sudden behavior changes are usually due to a medical condition of some sort. Given the history of dental problems, I am wondering if the cat is in some amount of pain and reacting to that.  Also, dental problems will, eventually lead to kidney disease which also makes the cat very irritable.

BTW, spray bottles are highly over rated as any kind of way to modify cat behavior.  

Best regards... Norm.