Which pulp horn is most likely to be exposed in the preparation of a large cavity in permanent molars?

The mesio-buccal pulp horn in upper first molars is often the most likely to be exposed during the preparation of a large cavity. This is primarily due to the anatomy of the tooth and the general pattern of caries. The mesio-buccal cusp tends to be one of the more prominent areas in upper first molars and is typically closest to the cavity being prepared.

When extensive decay occurs, the preparation often requires access to this area, leading to a higher likelihood of pulp exposure. The positioning and angulation of the mesio-buccal horn make it vulnerable during cavity preparation, mainly because it's located towards the buccal aspect of the tooth where decay commonly initiates.

In the case of the other pulp horns, while they may be at risk depending on the specific decay pattern or preparation design, the mesio-buccal pulp horn is specifically noted in dental practices as the one most associated with large cavity preparations in upper first molars. This anatomical consideration is crucial for dentists to understand to anticipate potential complications during restorative procedures.