Quantitative T₂ mapping MRI links dental caries severity to histological pulp degeneration in human teeth

Advancing carious lesions may induce structural and degenerative changes within the dental pulp that are not directly captured by conventional diagnostic methods. This study aimed to evaluate the association between caries severity, quantitative magnetic resonance imaging MR T₂ mapping, and histological pulp degeneration (PD). Fifty-two permanent premolars scheduled for orthodontic extraction were clinically assessed using the International Caries Detection and Assessment System (ICDAS) and classified as ICDAS 0-3. Before extraction, participants underwent 3-tesla (3T) MRI using a multi-echo spin-echo T2 mapping protocol. Mean T2 relaxation times and T2 variability, defined as the standard deviation of T2 values, were calculated within manually delineated coronal pulp regions of interest (ROIs). After extraction, pulp tissues were processed for hematoxylin and eosin staining, and PD was graded on a 0-3 scale and quantified morphometrically as the proportion of affected pulp area. Histological PD was identified in 12 of 52 teeth and was observed only in carious teeth with ICDAS 2-3 lesions. Teeth with PD showed lower mean T2 relaxation times than teeth without PD (114.236 ± 28.020 ms vs. 131.740 ± 23.562 ms; p = 0.049) and lower T2 variability (33.226 ± 7.080 ms vs. 41.463 ± 8.366 ms; p = 0.006). PD grade correlated positively with ICDAS score (ρ = 0.481; p = 0.00035) and negatively with mean T2 relaxation time (ρ = -0.367; p = 0.00896) and T2 variability (ρ = -0.381; p = 0.00708). Greater morphometric PD area was also associated with lower mean T2 relaxation time and T2 variability. These findings suggest that caries severity is associated with histological pulp degeneration and reduced MRI-derived T2 parameters, supporting quantitative T2 mapping as a noninvasive approach for investigating caries-related pulpal tissue changes.