In Pictures: How to Clean and Retouch Old Photos w...
12. Choose the <i>Freehand</i> tool. Select the background layer and carefully draw around the undamaged left side of the mouth. Draw around a larger area than you need as it’s easier to delete pixels than to add them. Now copy the selection, <b>Ctrl-C</b>, then create a new raster layer and choose <i>Edit-Paste-Paste as New Selection</i>.
In Pictures: How to Clean and Retouch Old Photos with Paint Shop Pro