Differences in the Prolonged Effectiveness Between Two Denture Adhesives With Different Rheological Characteristics

Aim This study aimed to investigate the differences in long-term effectiveness between two marketed denture adhesives: adhesive A (tough-grip cream; Kobayashi Pharmaceutical Co., Ltd., Osaka, Japan) and adhesive B (tough-grip cream A; Kobayashi Pharmaceutical Co., Ltd.) with different material science characteristics. Materials and methods This study consists of the following two parts: Experiment 1 - measuring material characteristics in vitro; Experiment 2 - measuring the denture movement and subjective evaluation in participants. The adhesion strength, viscosity, dynamic viscoelastic properties, and temporal changes in adhesion strength were measured in vitro. The study also investigated denture movement and subjective evaluations (stableness of the denture, duration of stableness, inhibitory effect on wobble, and inhibitory effect on slippage) after participants used the adhesives for a prolonged period (seven hours). Twelve participants were randomly divided and assigned into two protocols: protocol A (adhesive A followed by adhesive B) and protocol B (adhesive B followed by adhesive A). Results In the in vitro study, no significant differences were observed in adhesion strength or viscosity between the two adhesives. However, the storage moduli, loss moduli, and loss tangents exhibited significant differences. With respect to changes in temporal adhesion strength, adhesive B exhibited significantly higher values in the later cycles than did adhesive A. In the in vivo study, adhesive B tended to be preferred only in terms of the "duration of stableness" on the questionnaire, more than adhesive A, when the participants compared the two adhesives after they completed the two protocols. No statistical significance was observed between the two adhesives in vertical denture movement or subjective evaluations by visual analog scale (VAS). Vertical movement significantly decreased, and subjective denture stability significantly increased after five minutes compared to baseline for both adhesives. These effects were maintained seven hours later. Conclusion Our results indicate that both adhesives have sufficient long-lasting effects in clinical conditions for patients under conditions similar to those in this study, despite demonstrating different material characteristics in some factors in the in vitro study. Denture adhesives contribute to an improved quality of life and self-esteem, even for well-fitting dentures. Further studies are required to clarify the differences between denture adhesives under more severe oral conditions.