Which teeth are least likely to cause swelling in the buccal space posteriorly?

The maxillary canines are located in the anterior region of the dental arch and are positioned more toward the center of the mouth, as opposed to being posterior teeth. When infections occur in the vicinity of the maxillary canines, they generally do not extend into the buccal space posteriorly, meaning swelling is less likely to manifest in that area.

In contrast, the other teeth mentioned, particularly the mandibular first molars and to some extent the mandibular second premolars, are positioned more towards the posterior section of the dental arch. Infections originating from these teeth can lead to swelling in the buccal space posteriorly due to their proximity to the structures that can become affected by dental abscesses. The anatomical relationships of these teeth with surrounding tissues make the posterior buccal space more susceptible to swelling in these cases.

The maxillary first premolars, while located further toward the posterior than the canines, can still lead to swelling in the buccal space when infections occur. Therefore, among the options, the maxillary canines are indeed the least likely to be associated with this specific outcome, primarily due to their anterior location and the nature of the surrounding anatomical structures.