What type of teeth are usually affected by premature extraction leading to loss of arch length?

Premature extraction of teeth can significantly affect the alignment and spacing within the dental arch. In the case of the deciduous molars, their early loss can lead to significant consequences for arch length. These molars serve as important space holders for the permanent teeth that will erupt later.

When a deciduous molar is lost prematurely, there is a risk that the adjacent teeth can drift or shift into the resulting gap. This shifting can decrease the available space necessary for the proper eruption of the permanent molars, leading to crowding or misalignment in the dental arch.

Deciduous incisors, while important for aesthetics and function, don't hold the same amount of space for the permanent dentition as the molars do. Permanent incisors and permanent molars, though critical as well, are not directly impacted by the premature loss of deciduous teeth. Therefore, the deciduous molar is the most critical tooth whose premature extraction can adversely affect arch length due to its role in maintaining the spacing required for proper alignment of the permanent dentition.