16 patients will be included. Each patient receives 2 dental implants. One of them is coated with a drug, zoledronate, to improve fixation. Fixation is measured by vibration resonance frequency analysis at insertion and 2, 4, 6 and 8 weeks after insertion.The 2 implants in each patient are compared. We expect to find an early improvement (higher resonance frequency) in the coated implant.