Hydrophobic and hydrophilic effects on water structuring and adhesion in denture adhesives.

Denture adhesives are designed to be moisture-sensitive through the inclusion of a blend of polymer salts with varying degrees of water-sensitivity. This enables the adhesive to mix with saliva in vivo and activate its high tack, through the formation of a mucilaginous layer. We report for the first time, the use of differential scanning calorimetry to study a series of hydrophobic and hydrophilic polymeric systems in order to correlate water-structuring behavior with adhesion strength. Adhesive bonding of the more hydrophobic variants was higher than that of a commercial-based control and a more hydrophilic polymer system in both lap shear and tensile configurations. Water-binding data suggested that increasing the hydrophobicity of the maleic acid copolymer substituents led to decreased levels of freezing water. In comparison, increasing the hydrophilic nature of the polymer backbone gave higher levels of freezing water within the hydrated samples. The results of this study emphasize the importance of varying the levels of hydrophobic and hydrophilic components within denture adhesive formulations, alongside the types of water present within the adhesive systems. This phenomenon has shown the potential to fine-tune the adhesive properties and failure mode against poly(methyl methacrylate), surfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1355-1362, 2018.

Tunable denture adhesives using biomimetic principles for enhanced tissue adhesion in moist environments.

Nature provides many interesting examples of adhesive strategies. Of particular note, the protein glue secreted by marine mussels delivers high adhesion in wet and dynamic environments owing to existence of catechol moieties. As such, this study focuses on denture fixatives, where a non-zinc-containing commercial-based formulation has been judiciously modified by a biomimetic catechol-inspired polymer, poly(3,4-dihydroxystyrene/styrene-alt-maleic acid) in a quest to modulate adhesive performance. In vitro studies, in a lap-shear configuration, revealed that the catechol-modified components were able to enhance adhesion to both the denture base and hydrated, functional oral tissue mimic, with the resulting mode of failure prominently being adhesive rather than cohesive. These characteristics are desirable in prosthodontic fixative applications, for which temporary adhesion must be maintained, with ultimately an adhesive failure from the mucosal tissue surface preferred. These insights provide an experimental platform in the design of future biomimetic adhesive systems. STATEMENT OF SIGNIFICANCE: Mussel adhesive proteins have proven to be promising biomimetic adhesive candidates for soft tissues and here for the first time we have adapted marine adhesive technology into a denture fixative application. Importantly, we have incorporated a soft tissue mimic in our in vitro adhesion technique that more closely resembles the oral mucosa than previously studied substrates. The novel biomimetic-modified adhesives showed the ability to score the highest adhesive bonding out of all the formulations included in this study, across all moisture levels. This paper will be of major interest to the Acta Biomaterialia readership since the study has illustrated the potential of biomimetic principles in the design of effective prosthodontic tissue adhesives in a series of purpose-designed in vitro experiments in the context of the challenging features of the oral environment.