Maya Modeling :: Split Polygon And Can't Merge Border?

I have a model of gums and a set of teeth. What I am trying to do is create an animation where the fourth tooth back on each side of the upper gums disappear then create a blendshape causing the front teeth to move back and fill in the gaps as well as condense the gums so there isn't a gap here either. I am not exactly sure what the best way to do this would be, I am newer to Maya. My question is; Is there and easier way to do this because once I delete the faces and have a divides mesh I go to Mesh->Seperate and select Vertex mode on both and combine the meshes manually by selecting each vertex with the move tool and while holding "V" dragging the vertex over to the adjacent vertex on the opposite mesh. The issue im having is that the width of the mesh starts smaller upfront and progressivly gets bigger as you move to the back of the gums so by deleting a middle section the two meshes dont line up. The back mesh is much wider than the front. I am also worried that when i go to create a Blendshape to transition from the origional mesh to the new shortened one that will pull the teeth back to a perfect smile. I have heard that when creating a BS both meshes need to have the same number of Vertices and after removing a section mine wont. I am also concerned because after the two meshes have been sewn using this process I am left with an ugly point of intersection all the way around my mesh that has proven difficult to blend using the 'Sculpt Geometry Tool' with a falloff/Soft Mod.