The capacity for remineralization of carious dentin may depend on the level of remaining mineral.
Objective: To identify remaining mineral in carious dentin lesions by relating Caries Detector (CD) stained dentin carious zones to mineral content and nanomechanical properties.
Methods: Six occlusal dentin caries lesions from extracted human 3rd molars were used. Thin sections were removed from the lesion center and polished to 0.25 µm, using diamond paste. CD stain (pink, light pink, transparent, normal) was determined in 7-10 areas 200 µm apart along the lesion, from DEJ to pulp. Polished surfaces of lesions were evaluated by atomic force microscopy (AFM) nanoindentation (Triboindenter, Hysitron, Minneapolis, MN). Elastic modulus (E) and hardness (H) data were obtained in both hydrated and dry conditions. The mineral content (volume % mineral) of each area analyzed by AFM was determined by a custom-built digital transverse microradiography system used to measure mineral loss under dry conditions.
Results:
|
CD stain |
E (GPa) – dry |
E (GPa) – wet |
Volume % mineral |
|
Pink |
5.2 (4.4) a |
1.3 (1.8) a |
11.9 (2.6) a |
|
Light pink |
12.3 (1.9) b |
6.5 (5.1) a |
24.7 (6.5) b |
|
Transparent |
19.1 (8.4) c |
13.4 (2.6) b |
35.9 (2.2) c |
|
Normal |
22.6 (2.4) c |
19.1 (1.6) c |
43.6 (2.1) d |
Different letters (a, b, c, d) indicate significant differences (p <0.05). Spearman's rank correlation relating CD stain and volume % mineral was r2 = 0.88*. Pearson's r correlation coefficient relating volume % mineral to E was r2 = 0.65* dry and r2 = 0.88* hydrated (* indicates significant difference, p<0.05).
Conclusions: CD stain can distinguish between differences in mineral content in zones of carious dentin. Hydrated nanomechanical property measurements are a better indication of mineral content than dry measurements. The most demineralized zones of dentin caries contain remnant mineral.
Support: NIH/NIDCR Grants P01DE09859 and R01DE16849