What is a potential issue when a bridge extends from tooth #6 to #11?

When evaluating the construction of a dental bridge that spans from tooth #6 to #11, the potential issue of mechanical failure due to metal bending is particularly relevant. A bridge that covers multiple teeth places stress on the abutments, which are the teeth that support the artificial tooth or teeth in the middle.

When a fixed dental bridge is long, there may be considerable force applied during normal chewing and biting activities. If the supporting teeth are not sufficiently strong, or if the bridge itself is made of materials that are not able to withstand the forces exerted on them, it can result in mechanical failure. This might manifest as bending or warping of the metal frame of the bridge, leading to loosening or even fracture of the bridge.

The other options, such as decay in the abutments, gum recession, and allergic reactions to metal, while relevant dental concerns, are not direct consequences of the design and construction issues related to a long-span bridge. They do not specifically illustrate the mechanical stress and failures that can occur due to the bridge's length and the forces acting upon it. Therefore, mechanical failure from metal bending is the most pertinent concern in the context of extending bridges over multiple teeth.