Hi Jane,
Most general practice veterinarians are trained to address a majority of common dental problems, regardless of age of the patient. Most of these older dogs are in need a cleaning and possibly some extractions. I would first recommend a visit to your family veterinarian for an assessment. If there are special circumstances, they may recommend you visit a veterinary dentist who is trained in things like root canals, crowns, and more advanced procedures. Many specialists require a referral from your regular veterinarian anyway. To see what specialists are in your area, I encourage you to visit the American Veterinary Dental College website.
I wish you guys all the best.
Dr. Ryan Llera