Adult canine teeth pain out of the blue. no cavities either, any ideas anybody?

Three: Bruxism, sinusitis , and the remote possibility that the tooth has become non-vital due to trauma, you will need to have it evaluated locally...

Possibly from: Possibly from clenching, grinding, malocclusion, change in medications, stress, etc. Lots of potential causes. Please call your dentist for an evaluation of your occlusion.

Sinus infection: Sinus/nasal mucosal “toothache” is a common heterotopic pain condition. Yes, a sinus infection (sinusitis) or inflammation can cause a toothache, especially in the upper rear teeth and canine. Rec.: see your dentist for definitive diagnosis and treatment.

Grinding: Could be from grinding. If your tooth has a flat edge instead of point you are grinding on it and that can cause sensitivity and soreness.