1. Create a plane object in the front viewport, click with right button on it and select Properties. Select the option "See Through" and convert it to Editable Poly.
2. Align the object conform to image 014 using Vertex, move the Vertexes to get a similar view of image 014. Use Edges Face (F4).
3. On the right viewport, align the object as the next coming image.
4. Now, select the sub-object edge and go to dialogue extrude of the model. Don't forget: when you go to extrude with the front viewport adjust with the left viewport the new position of the face, you can use Shift buttons for the extrusions.
5. Continue sculpting the model to get a similar view of image 018.
6. Now go to the polygon sub-object and make it as image 019. You're making a copy, not a new object. Edit it from the teeth until you get to the nose. Don't forget to edit the other viewports.