Ring of Death — Ruth J. Hartman

Dorey Cameron just wants to do her job. But that's nearly impossible when her dental patients don't show up for appointments. The bizarre accidents causing them not to appear can't be a coincidence. Someone is sabotaging her. But why? Things take a terrible turn when vandalism, mugging and murder have the police pointing the finger at Dorey. Something in her possession must be worth killing for. If Dorey can't figure out the mystery in time, will she be the next victim?