What is a common characteristic of a primary molar that may complicate extraction techniques?

A common characteristic of primary molars that may complicate extraction techniques is the presence of un-resorbed roots. In primary teeth, the roots are intended to resorb over time as the permanent teeth develop and come in. If extraction is attempted before the roots have undergone sufficient resorption, they may be more firmly anchored in the bone, leading to complications during the extraction process. This can require additional techniques or tools in order to safely and effectively remove the tooth, making the extraction more difficult than it would be for a primary molar with properly resorbed roots.

In contrast, deep caries, while they may complicate treatment in general, are not specific to the extraction technique itself. Multiple crowns may also not necessarily impede the extraction unless they interfere with the surrounding structures, and severe mobility, while indicating potential issues, would not complicate extraction but rather suggest that extraction could occur more easily. Thus, un-resorbed roots distinctly pose a challenge in the context of extracting primary molars.