Abstract
The effect of Candida albicans biofilms and methyl methacrylate (MMA) pretreatment on the bond strength between soft denture liners and polymethyl methacrylate (PMMA) resin was analyzed. Specimens were prepared and randomly divided with respect to PMMA pretreatment, soft liner type (silicone-based or PMMA-based), and presence or absence of a C. albicans biofilm. Samples were composed of a soft denture liner bonded between two PMMA bars. Specimens (n = 10) were incubated to produce a C. albicans biofilm or stored in sterile PBS for 12 days. The tensile bond strength test was performed and failure type was determined using a stereomicroscope. Surface roughness (SR) and scanning electron microscopy (SEM) analysis were performed on denture liners (n = 8). Highest bond strength was observed in samples containing a silicone-based soft liner and stored in PBS, regardless of pretreatment (p < 0.01). Silicone-based specimens mostly underwent adhesive failures, while samples containing PMMA-based liners predominantly underwent cohesive failures. The silicone-based specimens SR decreased after 12 days of biofilm accumulation or PBS storage, while the SR of PMMA-based soft liners increased (p < 0.01). The PMMA-based soft liners surfaces presented sharp valleys and depressions, while silicone-based specimens surfaces exhibited more gentle features. In vitro exposure to C. albicans biofilms reduced the adhesion of denture liners to PMMA resin, and MMA pretreatment is recommended during relining procedures.
Highlights
Soft denture liners are used to form a comfortable interface between denture and soft oral tissues, reducing traumatic transmission of occlusal forces to severely resorbed alveolar ridges and areas recovering from surgical procedures.[1]
Denture liners were applied between two treated polymethyl methacrylate (PMMA) bars, and specimens (n = 10) were subjected to biofilm accumulation, or phosphate buffered saline (PBS) storage, in order to simulate conditions experienced by dentures in clinical applications
Cohesive failures were mainly observed in the group receiving methyl methacrylate (MMA) pretreatment and stored in PBS (Table 2)
Summary
Soft denture liners are used to form a comfortable interface between denture and soft oral tissues, reducing traumatic transmission of occlusal forces to severely resorbed alveolar ridges and areas recovering from surgical procedures.[1]. Aging of soft liner and denture base.[5] In order to prevent these problems, several denture base surface treatments have been proposed to increase the bond strength between these materials.[6]. When compared to other denture resin pretreatments,[6,7,8] methyl methacrylate (MMA) surface pretreatment increased tensile bond strength[8] and reduced microleakage between the denture base and silicone-based soft liners.[7] In order to evaluate the durability of bonds between soft liners and pretreated denture resins, previous studies have subjected specimens to distilled water storage,[9] accelerated aging in hot water,[10] or thermocycling procedures[8,11] prior to bond strength testing
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