In vitro Remineralization of Severely Compromised Bonded Dentin

Abstract

Biomimetic remineralization is potentially useful for remineralizing incompletely resin-infiltrated collagen matrices created by etch-and-rinse adhesives. In this study, we tested the hypothesis that structurally-altered dentin collagen cannot be remineralized to the same hierarchical order and dimension that are seen in structurally-intact dentin collagen The remineralization medium consisted of a set Portland cement/simulated body fluid system containing polycarboxylic acid and polyvinylphosphonic acid as biomimetic analogs. Remineralization of air-dried, collapsed hybrid layers was apparent after one month, with hybrid layers remineralized to 80–90% of their thickness after 2–4 months. A hypermineralized layer was seen on the hybrid layer surface and tubular orifices were occluded with apatite deposits that resembled those present in noncarious cervical dentin. Structurally-altered collagen is unlikely to be remineralized to the same hierarchical order and dimension that are seen in intact dentin. The aggressively air-dried acid-etched dentin remineralization model also sheds light on the mechanism of sclerotic dentin formation.

Remineralization of artificial dentinal caries lesions by biomimetically modified mineral trioxide aggregate

“…Moreover, degradation of the demineralized collagen matrices from the surface of the remineralized artificial caries-like lesions by endogenous matrix metalloproteinases present in dentin [28] was not observed in the present study as a result of the improved remineralization kinetics. This phenomenon has previously been observed using the proof-on-concept biomimetic remineralization strategy [47] and mimics the tubular occlusion observed in carious dentin [48]. As the experimental protocol involved placement of set MTA over the dentin lesion, such a phenomenon could not have been caused by introduction of fine MTA particles into the dentinal tubules and represented genuine intratubular apatite deposits.…”

Bioactivity of Mineral Trioxide Aggregate and Mechanism of Action

“…Prior to this report (Atmeh et al) [6], a similar hypermineralised layer was observed on the of the resin-dentine interface (i.e. hybrid layer) when set white Portland cement was used to remineralise hybrid layers created in severely compromised bonded dentine [102]. Whilst this 'mineral infiltration zone' enables a calcium silicate cement to 'bond' to dentine, it is likely to be highly brittle because type I collagen, which is responsible for the toughness of biological mineralised tissues [8,94], is destroyed by the alkalinity of the calcium silicate cements.…”

“…In this interaction, the highly caustic (alkaline) calcium silicate cement hydration products are responsible for the degradation of the collagenous component of intertubular dentine. A porous intertubular dentine layer is produced in which the collagen fibrils are depleted, leaving behind porous 'mineral ghosts' [102] that enable the permeation of high concentrations of calcium, hydroxyl and carbonate ions to form a hypermineralised layer [6]. Such a process has been termed 'alkaline etching' [6], to distinguish it from the 'acid etching' process associated with the use of dentine adhesives and glass ionomer cements.…”

Adhesive Materials with Bioprotective/Biopromoting Functions

“…This strategy reproduced both intrafibrillar and interfibrillar minerals and recapitulated the dimension and order of the apatite crystallites that are found in natural dentin [70][71][72][73]. Using this biomimetic remineralization strategy, both hybrid layers created by etch-and-rinse adhesives [68,74,75] and moderately aggressive self-etch adhesives [65,74,76], as well as 250-to 300-μm-thick completely demineralized dentin lesions, can be remineralized [77][78][79]. This bottom-up remineralization strategy does not rely on seed crystallites, and may be considered as a potentially useful mechanism in extending the longevity of resin-dentin bonds [80] via restoring the dynamic mechanical properties of the denuded collagen within the hybrid layer to approximate those of mineralized dentin [81].…”