IADR Abstract Archives
Fluoride-Based Strategies for Enamel Remineralization Cannot be Translated to Dentin
Objectives: Fluoride is often advertised to remineralize teeth but its effect on dentin remineralization requires further investigation. The Polymer-Induced Liquid-Precursor (PILP) approach has been shown to remineralize artificial lesions in dentin by reintroducing apatite mineral inside collagen fibrils (intrafibrillar mineralization). This study focuses on whether fluoride supplementation to calcium phosphate solutions can functionally remineralize artificial dentin lesions or whether the presence of a process-directing agent like poly-aspartic acid (pAsp) is required.
Methods: Dentin slices were sectioned from human molars and demineralized to create shallow (140um) or deep (700um) artificial lesions. Subsequently, specimens were immersed in remineralization solution with fluoride (0,1,2,5 ppm) for 14d or 28d and analyzed with optical microscopy, SEM, and Energy-Dispersive-X-Ray-Spectroscopy (EDX). Intrafibrillar mineralization was evaluated by measuring resistance to tissue removal from bleaching with 7% NaOCl and statistically analyzed (ANOVA, Tukey, p<0.05).
Results: Optical microscopy suggested that lesions shrink minimally after remineralization for all treatment groups (ANOVA, Tukey, p>0.05). SEM images for lesions remineralized with fluoride showed mineral precipitate (>100um) on the lesion surface. EDX analysis indicated that the main mineral phase was a mixture of hydroxyapatite and fluorapatite. The lesion zone disintegrated when exposed to bleach, indicating that remineralization failed to protect the tissue. Conversely, lesions remineralized with PILP and fluoride were resistant to bleach treatments and did not show signs of disintegration at 24h NaOCl exposure. SEM microscopy of PILP-treated specimens displayed fully remineralized dentin structurally similar to sound dentin. No surface precipitate of mineral was observed. Calcium and phosphate analysis by EDX showed a large recovery of ions throughout the entire lesion comparable to sound dentin.
Conclusions: Fluoride in calcium phosphate solution creates predominantly surface precipitation, but is unable to induce intrafibrillar mineral in collagen. Functional remineralization of dentin lesions requires the presence of pAsp. Therefore fluoride-based strategies to remineralize enamel cannot be translated for repair of carious dentin.
Methods: Dentin slices were sectioned from human molars and demineralized to create shallow (140um) or deep (700um) artificial lesions. Subsequently, specimens were immersed in remineralization solution with fluoride (0,1,2,5 ppm) for 14d or 28d and analyzed with optical microscopy, SEM, and Energy-Dispersive-X-Ray-Spectroscopy (EDX). Intrafibrillar mineralization was evaluated by measuring resistance to tissue removal from bleaching with 7% NaOCl and statistically analyzed (ANOVA, Tukey, p<0.05).
Results: Optical microscopy suggested that lesions shrink minimally after remineralization for all treatment groups (ANOVA, Tukey, p>0.05). SEM images for lesions remineralized with fluoride showed mineral precipitate (>100um) on the lesion surface. EDX analysis indicated that the main mineral phase was a mixture of hydroxyapatite and fluorapatite. The lesion zone disintegrated when exposed to bleach, indicating that remineralization failed to protect the tissue. Conversely, lesions remineralized with PILP and fluoride were resistant to bleach treatments and did not show signs of disintegration at 24h NaOCl exposure. SEM microscopy of PILP-treated specimens displayed fully remineralized dentin structurally similar to sound dentin. No surface precipitate of mineral was observed. Calcium and phosphate analysis by EDX showed a large recovery of ions throughout the entire lesion comparable to sound dentin.
Conclusions: Fluoride in calcium phosphate solution creates predominantly surface precipitation, but is unable to induce intrafibrillar mineral in collagen. Functional remineralization of dentin lesions requires the presence of pAsp. Therefore fluoride-based strategies to remineralize enamel cannot be translated for repair of carious dentin.
