Water Sorption Behavior of Denture Base Materials

All dentures may have pores or networks of channels into which water or saliva can penetrate and if not allowed to dry completely, this fluid ingress can contribute to the undesirable growth of microorganisms. Objectives: To study the water sorption and desorption behavior of acrylic resin denture base materials. Methods: Complete upper and lower Lucitone 199 acrylic resin denture bases were subjected to long term water immersion (35 days) and then allowed to dry to constant weight with the water uptake and loss being followed by weight changes. Results: Water sorption by upper and lower dentures (1.34% and 1.45%) was lower than the commonly reported acrylic resin equilibrium uptake of 2.3%. This difference was due to the proportionately greater weight of the teeth within the denture, with the prosthetic teeth minimal water sorption. The higher level of absorbed and retained water in the lower denture compared to the upper is probably due to its greater thickness and suggests that mandibular dentures may have greater susceptibility to microbial penetration and infestation. The study showed sorption follows a sigmoidal pattern up to 30-35 days and upon drying, there is a rapid initial loss of water followed by a continuing slower rate of water loss with a relatively high level of retained water after drying to constant weight. Analysis of the data indicates that the rate of desorption is dependent upon the level of retained water within the structure. These findings suggest that in the clinical situation, where ingress of water and saliva would be accompanied by microorganisms, both fluids and pathogens would be harbored within the structure of the denture. Conclusions: Even after surface cleansing of the denture, pathogens may migrate out of the denture and colonize the sanitized denture surface. Disclosure: Research supported by GlaxoSmithKline.