Ideally the rigid connector should attach the pontic to the more distal abutment. The platform between the implant and the abutment can be flat (buttress) or conical fit. It connects the over denture to the individual abutment. It spans over a nearly flat alluvial valley floor between bedrock abutment ridges. This can largely be prevented with proper screw design and torquing of the abutment. If the root canals of the abutment teeth are obliterated, endodontic treatment is not required. Abutment teeth require minor or no preparation. A dental lab then simultaneously fabricates an abutment and crown. Multiple factors influence the selection of appropriate abutment teeth. The total length of the Golden Gate Bridge from abutment to abutment is . Alternatively, part of a bridge abutment conveniently located behind a signal may be painted white. Pontics and abutment teeth are referred to as units. The train passes through two short tunnels, one under the Bear Mountain Bridge abutment. These surveys established that the center section had moved downstream and toward the eastern abutment. Displacements of the deck on the abutment level are measured to the nearest millimetre.