A laser-based system and method for treatment of hard tissue enhances remineralization and fluoride uptake to improve resistance to demineralization. The system can include a laser source, an optic, and a controller for controlling the laser source and/or the optic to deliver radiation to a treatment region with desirable characteristics (e.g., to remove carbonate without damaging the tissue surface). In some cases, the system includes a handpiece having an optical element (e.g., a lens) mounted within a replaceable cartridge and adapted to modulate a laser beam to render the beam non-ablative, prior to the laser beam's delivery to the treatment region. In some embodiments, treatment with the laser can be combined with a fluoride treatment for enhanced therapeutic effect.