Tissue response in hemisectioned primary mandibular second molars

Congenital absence of mandibular second premolars occur in 2.91-3.22% of individuals, with nearly half of cases being bilateral. Interceptive hemisection of primary second molars promotes mesial drift but exposes the pulp for an extended period. This study investigates histopathological responses of pulp and associated mineralized tissues.

Children aged 7-12 in Skaraborg region, Sweden, were screened for over-retained primary mandibular second molars as part of a single-center, blinded, prospective split-mouth randomized controlled clinical trial comparing hemisection with extraction. Mesial roots of 21 hemisected teeth were collected for histopathological analysis of inflammatory infiltrate, pulpal necrosis, fibrosis, and hard tissue formation.

Mean interval between distal and mesial root extraction was 11.54 ± 4.3 months. Histopathological analysis revealed no pulpal inflammation in 14% of specimens, acute/subacute inflammation in 38%, chronic inflammation in 48%, and necrosis in 24%. Reparative tertiary dentin with capping occurred in 48% and without capping in 33%. Necrotic mineralized tissue appeared in one specimen. Three patients reported symptoms during follow-up.

Prolonged pulp exposure following hemisection induced tertiary dentinogenesis, maintaining pulp vitality for up to 17 months. Despite histological evidence of inflammation or necrosis, most cases remained asymptomatic, indicating remarkable regenerative capacity of primary pulp-dentin complex.