Recovery after PILP remineralization of dentin lesions created with two cariogenic acids

Abstract

Objectives Acetate and lactate are important cariogenic acids produced by oral bacteria. They produced different residual dentin structures in artificial lesions of similar depth. We evaluated if such lesions responded in the same way to a polymer-induced-liquid-precursor(PILP) remineralization. Design Dentin blocks obtained from human third molars, divided into 6 groups(n=3). Blocks were demineralized with acetate(66 hours) or lactate(168 hours) buffer at pH 5.0 to create 140 μm target lesion depths. A-DEM and L-DEM groups received no remineralization. Other groups were remineralized for 14 days. 100 μg/mL polyaspartate was added into the remineralizing buffer for A-PIL and L-PIL, whereas A-CAP and L-CAP were treated with the same solution but without polyaspartate. Cross-sectioned blocks were examined for shrinkage and AFM-topography. Line profiles of reduced elastic modulus(Er) were obtained by AFM-based nanoindentation across the lesion. Ultrastructures were examined with TEM. Results A-PIL and L-PIL recovered in shrinkage to the original height of the dentin and it appeared normal with tubules, with increases in Er at both outer flat and inner sloped zones. At the sloped zone, acetate lesions lost more Er but recovery rate after PILP was not statistically different from lactate lesions. A-CAP and L-CAP showed surface precipitates, significantly less recovery in shrinkage or Er as compared to PILP groups. TEM-ultrastructure of PILP groups showed similar structural and mineral components in the sloped zone for lesions produced by either acid. Conclusions The PILP process provided significant recovery of both structure and mechanical properties for artificial lesions produced with acetate or lactate.

Integrating the PILP-mineralization process into a restorative dental treatment

“…This study did not apply TEM analysis to demonstrate the presence of intrafibrillar mineral, which has been shown in previous studies by our group and others [16, 20]. Instead we tested if these approaches resulted in a mechanical reinforcement of the dentin lesion which is the most critical parameter when attempting to remineralize dentin as its function is primarily mechanical.…”

“…Therefore, to examine FR of dentin, cross sections were analyzed with reflective light microscopy using an Olympus BH-2 microscope (Olympus America Inc., San Diego, CA) to determine the amount of dentin collapsed versus recovery after the remineralization cycle. This has been shown to be a useful early indicator of effective FR [20]. The lesion depth, the distance between the original intact dentin surface protected by the nail varnish and exposed treated dentin, was measured using OMAX ToupView (Touptek Photonics, Zhejiang, China).…”

“…pAsp, the nanomechanical properties of the remineralized dentin had functionally recovered [7, 8]. Elastic modulus and hardness of the fully demineralized outer zone recovered to about 60% of normal dentin values with PILP applications of 2 weeks, while calcium phosphate solutions alone did not produce any significant mechanical recuperation [9, 20]. The restoration of mechanical properties of the tissue is critical for regaining its function, and to date the PILP-approach appears to be the prime suitable method to reintroduce mineral into collagen fibrils and restore tissue properties, either partially or fully, thus we refer to this as functional remineralization (FR) [9, 20-22].…”

“…Elastic modulus and hardness of the fully demineralized outer zone recovered to about 60% of normal dentin values with PILP applications of 2 weeks, while calcium phosphate solutions alone did not produce any significant mechanical recuperation [9, 20]. The restoration of mechanical properties of the tissue is critical for regaining its function, and to date the PILP-approach appears to be the prime suitable method to reintroduce mineral into collagen fibrils and restore tissue properties, either partially or fully, thus we refer to this as functional remineralization (FR) [9, 20-22]. In addition studies on commercial silicate-based and alumo-silicate-based cements have shown promising data with regards to mineral recovery in artificial lesions but lacked evidence for a functional recovery [6, 10, 23].…”

“…Previous studies have applied standard PILP-treatments on artificial lesions by immersion of demineralized dentin cut from tooth specimens into a solution containing 4.5mM Ca 2+ , 2.2 mM PO 4 3− and between 0.1 and 1mg/ml pAsp (27kDa or 200 mer, Alamanda Polymer Inc.) for several days and weeks [9, 20]. A pure solution-based approach is not feasible for application in clinical dentistry.…”