How is wedging retention affected if the inlay is not sufficiently wide mesiodistally?

When an inlay is not sufficiently wide mesiodistally, the wedging retention is decreased. Wedging retention relies on the effective seating of the restoration during insertion, which is facilitated by the geometry of the inlay and the preparation it is being placed into.

A wider mesiodistal dimension allows for greater contact between the inlay and the walls of the tooth preparation, enhancing the wedging effect that secures the inlay in place. This is because a wider surface area provides more resistance against displacement forces. If the inlay is too narrow, it fails to create adequate contact with the tooth structure, which diminishes the retention. In essence, the lack of sufficient mesiodistal width means that there are fewer surfaces to create an interlocking fit, leading to a reduced wedging effect and, consequently, decreased retention of the inlay.

Other factors like the material used may influence retention in broader terms, but the fundamental geometric aspect of mesiodistal width directly correlates with how effectively the inlay can be retained through wedging principles.