Never top a tree, especially a dogwood. If these were heavily shaded and now the source of shade is suddenly gone you may have problems with burning of their foliage or stems during periods of hot sun; if it is bad enough they may be spoiled and end up being removed.

If it is a tree of some size that has been in place for years - presumably it has as it has had time to develop the current lean towards the light - it probably will not be feasible to re-orient it now, without digging it up and re-planting it with a different angle to the trunk. If the lean is strong enough (or, of course, if the tree is too big to be dug up without the equipment, experience and help of a landscape contractor - and you do not want to pay for this) even that will probably not be possible as you would end up with half of the roots being plunged into the ground lower than they were before and the other half coming out of it.