What does it mean when someone says "I never have any cavities"?

As a practicing dentist I sometimes encounter new patients, who have loved their previous dentist and are especially proud of how their teeth 'never need work'. I often hear this remark with a sense of dread; Allthogh it can mean they have great teeth, it sometimes can be a tip off that their prior dentist was not detecting some dental problems. In such a situation, It can be awkward telling them the bad news, and I am always concerned that my potential new patient will not believe me If it turns out that they do have a number of dental problems. After all they trusted and loved their old dentist and I am the 'new kid in town' and it definitely can turn out to be a case of "shoot the messenger". Often patients do not want to believe bad news and seek a second and third opinion ( often from their friends and family) before having a unwanted dental procedure.