No abstract

The field of dental materials has undergone more of a revolution than an evolution over the past 100 y. The development of new products, especially in the past half century, has occurred at a staggering pace, and their introduction to the market has been equally impressive. The movement has mostly come in the area of improved esthetics, marked by the gradual replacement of dental amalgam with dental composite and all-metal and porcelain-fused-to-metal indirect restorations with reinforced dental ceramics, all made possible by the rapid improvements in dental adhesive materials. This article covers the time course of dental materials development over the past century in which the Journal of Dental Research has been published. While there have been advances in nearly all materials used in the field, this article focuses on several areas, including dental amalgam, dental composites and light curing, dental adhesives and dental cements, ceramics, and new functional repair materials. A few short statements on future advances will be included at the end.

Objectives We studied artificial dentin lesions in human teeth generated by lactate and acetate buffers (pH 5.0), the two most abundant acids in caries. The objective of this study was to determine differences in mechanical properties, mineral density profiles and ultrastructural variations of two different artificial lesions with the same approximate depth. Methods 0.05 M (pH 5.0) acetate or lactate buffer was used to create 1) 180 μm-deep lesions in non-carious human dentin blocks (acetate 130 h; lactate 14days); (2) demineralized, ~180 μm-thick non-carious dentin discs (3 weeks). We performed nanoindentation to determine mechanical properties across the hydrated lesions, and micro X-ray computed tomography (MicroXCT) to determine mineral profiles. Ultrastructure in lesions was analyzed by TEM/selected area electron diffraction (SAED). Demineralized dentin discs were analyzed by small angle X-ray scattering (SAXS). Results Diffusion-dominated demineralization was shown based on the linearity between lesion depths versus the square root of exposure time in either solution, with faster kinetics in acetate buffer. Nanoindentation revealed lactate induced a significantly sharper transition in reduced elastic modulus across the lesions. MicroXCT showed lactate demineralized lesions had swelling and more disorganized matrix structure, whereas acetate lesions had abrupt X-ray absorption near the margin. At the ultrastructural level, TEM showed lactate was more effective in removing minerals from the collagenous matrix, which was confirmed by SAXS analysis. Conclusions These findings indicated the different acids yielded lesions with different characteristics that could influence lesion formation resulting in their distinct predominance in different caries activities, and these differences may impact strategies for dentin caries remineralization.

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.