Use in Edit mode remove doubles from the tools tab. If they still there then hovering the mouse over them and press L* and then press X and delete them.
If you kill to much select three vertices (off course you could select more ad once, but this wouldn't generate a tris) and press F to fill the hole.
You can also use the material tab to select all with the material and delete them with X, too.
*With L you can select a connected mesh, which is pretty useful if one object exist out of more than one meshes.