Glass Hybrid, but Not Calcium Hydroxide Remineralized Artificial Residual Caries Lesions In Vitro

Objectives: For deep carious lesions, selective excavation is increasingly recommended. The resulting residual carious lesions might benefit from remineralization by lining or restoration materials. We aimed to compare remineralization of artificial residual lesions by calcium hydroxide and glass hybrid materials in combination with pulpal fluid simulation.

Methods: On the coronal aspect of human dentin discs (n=20) artificial lesions (median mineral loss ΔZ [25^th/75^th percentiles]=1643 [1301/1858] vol%×µm) were induced. One third of each disc served as baseline sample. The remaining disc was divided into 4 specimens, each being covered with one experimental material (n=20/group): Flowable composite without liner (CO), setting or non-setting calcium hydroxide plus flowable composite (CH-S, CH-NS), glass hybrid (GH). Samples were mounted in a dual-chamber device. Pulpal surfaces were exposed to simulated pulpal fluid at 2.94 kPa, while coronal surfaces were exposed to artificial saliva, and rinsed with 200 ppm NaF every 2 weeks. After 12 weeks, mineral loss differences were assessed using transversal microradiography. Electron probe microscopic analysis was additionally used to measure fluoride and strontium concentrations in exemplary samples.

Results: Mineral gain in CO was ΔΔZ=372 (115/501) vol%×µm. This was not significantly different in CH-S (ΔΔZ=317 [229/919] vol%×µm) or CH-NS (ΔΔZ=292 [130/579] vol%×µm; p>0.05/Wilcoxon-test), but was sufficiently increased in GH (ΔΔZ=1044 [751/1264] vol%×µm, p<0.001). Samples in GH showed fluoride and strontium enrichments deep into the dentin. Such enrichment was not found in CO.
Conclusions: Within the limitations of this study, glass hybrid, but not calcium hydroxide provided coronal remineralization of residual carious lesions.