Intelligent drugs that target tumors, etc., and release therapeutics to cells that need it.  Imaging agents for MRI like gadolinium atoms in short nanotubes.  Targeted magnetic and optical nanoparticles that cause local heating to destroy tumors.  New forms of genomic sequencing and RNA profiling to detect diseases at early stages.  Cancer screening through nanomechanical measurements of cell stiffness.  Nano scaffolding for drugs to increase their local effectiveness.  Dental implants with bio-compatible nanoparticles.  Many new forms of dental treatments including antibacterial mouthwashes and toothpastes.  Miniaturized devices like pacemakers, electrical brain and nerve stimulation to overcome loss of cochlear [hearing] and vision, or to stop paralysis, seizures and fits. 

The list is quite endless.  The future of effective, cheap medical treatment and prevention will rely on many direct and indirect contributions from nanotechnology.