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Objective Several studies have demonstrated that insufficient denture hygiene constitutes a significant risk factor for aspiration pneumonia. While various cleaning protocols have been proposed for conventional hard denture base materials, there remains a notable paucity of research specifically addressing effective cleaning strategies for resilient denture liners (RDLs). This study aimed to evaluate the efficacy of three denture cleaning methods—mechanical, chemical, and dual (combined mechanical and chemical)—for removing microbial biofilms from different denture‐liner materials using a randomized crossover clinical trial. Materials and Methods This three‐period randomized crossover clinical trial included edentulous patients wearing maxillary complete dentures embedded with specimens of a hard‐resin liner and silicone‐based and acrylic‐based RDLs. All liners were fabricated directly in the patient's mouth. Participants performed the three cleaning interventions for 2 weeks each. Swabs from the relined denture surfaces were cultured in phosphate‐buffered saline, and the colony‐forming units (CFUs) were counted. The influence of each cleaning method on the CFU count was determined. Results The dual‐cleaning method demonstrated a significant reduction in CFU count compared to mechanical cleaning, but only for the acrylic‐based RDL. No significant differences were observed between the cleaning methods for the silicone‐based RDL and hard‐resin liner. The CFU count was the highest for silicone‐based RDLs, followed by that for acrylic‐based RDLs, and hard‐resin liners. Conclusion The dual method comprising mechanical and chemical cleaning was the most effective cleaning strategy for relined dentures, although the advantage was limited to acrylic‐based RDL. Trial Registration This study was registered in the UMIN Clinical Trials Registry (UMIN000056738).

Purpose. The objective of this systematic review is to compare results concerning the properties of adhesion, roughness, and hardness of dental liners obtained in the last ten years. Methods. Searches on the databases LILACS, PubMed/Medline, Web of Science, and Cochrane Database of Systematic Reviews were supplemented with manual searches conducted between February and April of 2018. The inclusion criteria included experimental in vitro and in vivo, clinical, and laboratory studies on resilient and/or hard liners, assessment of hardness, roughness, and/or adhesion to the denture base, and physical/mechanical changes resulting from the disinfection process and changes in liners’ composition or application. Results. A total of 406 articles were identified and, from those, 44 are discussed. Twenty-four studies examined the bond strength, 13 surface roughness, and 19 the hardness. Of these 44 studies, 12 evaluated more than one property. Different substances were used in the attempt to improve adhesion. Considering roughness and hardness, the benefits of sealants have been tested, and the changes resulting from antimicrobial agents’ incorporation have been assessed. Conclusion. Adhesion to the prosthesis base is improved with surface treatments. Rough surfaces and changes in hardness compromise the material’s serviceability.

Background Digitally fabricated dentures may require relining due to continual alveolar ridge resorption. However, studies evaluating the tensile bond strength (TBS) of digitally fabricated dentures bonded to denture liners are lacking. This study aimed to evaluate the TBS of autopolymerized, heat-polymerized, milled, and 3D printed denture base materials bonded to 2 acrylic-based and 2 silicone-based denture liners, both before and after thermocycling. Additionally, the impact of thermocycling on the TBS were also evaluated. Methods The TBS of 4 different denture base materials (Palapress (PL), Vertex Rapid Simplified (VR), Smile CAM total prosthesis (SC), and NextDent denture 3D+ (ND)) bonded to 2 acrylic-based (GC Soft-Liner (GC) and Tokuyama Rebase II (RB)) and 2 silicone-based (Ufi Gel P (UP) and Sofreliner Tough M (ST)) denture liners were tested. Specimens ( n  = 8) were divided into non-thermocycling and thermocycling groups. Non-thermocycling specimens were tested after 24-hours water immersion, while thermocycling specimens were underwent 5000 cycle and were immediately tested. Mode of failure was examined under a stereomicroscope. Data were analyzed using 2-way ANOVA and Tukey HSD tests (α = 0.05), and independent samples t test (α = 0.05) for TBS between non-thermocycling and thermocycling groups. Results For the non-thermocycling groups, within the same denture liner material, no significant differences were found between denture base materials, except the ND + RB group, which had significantly lower TBS. For the thermocycling groups, within the same denture liner material, the TBS in the PL group exhibited the highest and the ND group exhibited the lowest. Within the same denture base material, in both non-thermocycling and thermocycling groups, the TBS in the ST group exhibited the highest; in contrast, that in the GC group exhibited the lowest. No significant differences were observed in TBS between non-thermocycling and thermocycling groups, except for denture base materials bonded to the ST group, SC + UP, and ND + UP groups. Conclusions Milled denture base can be relined with acrylic-based or silicone-based denture liner. However, cautions should be exercised when relining 3D printed denture base. Thermocycling did not affect TBS between acrylic-based denture liners and denture bases. In contrast, it affected the bond between silicone-based denture liner and denture base.

Purpose The aim of this in vitro study was to evaluate the changes the rheological properties of some soft lining materials, to compare the rheological properties and viscoelastic behaviour at different temperatures. Materials and methods Five soft lining materials (acrylic and silicone based) were used. the storage modulus (G’), loss modulus (G”), tan delta (tan δ) and complex viscosity (η’) were chosen and for each material, measurements were repeated at 23, 33 and 37  °C, using an oscillating rheometer. All data were statistically analyzed using the Mann Whitney U test, Kruskal Wallis test and Conover’s Multiple Comparison test at the significance level of 0.05. Results Soft lining materials had different viscoelastic properties and most of the materials showed different rheological behavior at 23, 33 and 37  °C. At the end of the test (t¹5), at all the temperatures, Sofreliner Tough M had the highest storage modulus values while Visco Gel had the highest loss Tan delta values. Conclusions There were significant changes in the rheological parameters of all the materials. Also temperature affected the initial rheological properties, and polymerization reaction of all the materials, depending on temperature increase. Clinical implications Temperature affected the initial rheological properties, and polymerization reaction of soft denture liner materials, and clinical inferences should be drawn from such studies conducted. It can be recommended to utilize viscoelastic acrylic-based temporary soft lining materials with lower storage modulus, higher tan delta value, and high viscosity in situations where pain complaint persists and tissue stress is extremely significant, provided that they are replaced often.

Objective: To determine the effects of adding a quaternary ammonium methacryloxy silicate (K18) and K18-functionalized filler (K18-Filler) on the material and antimicrobial properties of a hard denture reline material. Materials and methods: 30% K18 in methyl methacrylate (K18-MMA; 0–20 wt% of reliner) and K18-Filler (0–30 wt% of reliner) were incorporated into KoolinerTM hard denture reliner. KoolinerTM served as the control. The cure (Shore A hardness), hydrophilicity (contact angles), mechanical (3-point bend test), water sorption, and antimicrobial properties against Streptococcus mutans, S. sanguinis, and Candida albicans were determined. Results: Most K18 groups cured well and had comparable Shore A hardness values (range ~52 to 70 DHN) to that of controls (67.2 ± 1.8 DHN; Bonferroni corrected p > 0.0003). Even the softest group had hardness values within the range of commercial products. Half of the K18 groups had comparable contact angles to that of controls (range ~75° to 80° vs 83.41° ± 2.66°; Bonferroni corrected p > 0.0003), and most were within the range of commercial liners. K18-MMA and K18-Filler increased modulus but decreased ultimate transverse strength (UTS). All experimental groups had comparable or higher moduli than controls (range ~966 to 2069 MPa vs 1340 ± 119 MPa; Bonferroni corrected p < 0.0003), but only half of the experimental groups had comparable UTS to that of controls (range ~41 to 49 MPa vs 55.8 ± 1.5 MPa; Bonferroni corrected p > 0.0003). The 15% and 20% K18-MMA with 30% K18-Filler groups had significant antimicrobial activity against all three microbes (p < 0.05). However, the 15% and 20% K18-MMA with 30% K18-Filler groups had significantly higher water sorption at early time points (p < 0.05). After 8 weeks, they were comparable to each other (p > 0.05). Conclusions: K18-MMA and K18-Filler are promising antimicrobial additives that produce hard denture liners with material properties within the range of commercial products and significant antimicrobial properties against S. mutans, S. sanguinis, and C. albicans. Further development is needed to reduce water sorption.

As poor denture hygiene is related to Candida colonisation, disinfectant solutions have been proposed as an effective method of preventing denture stomatitis. This study assessed the efficacy of denture cleansers on Candida albicans and Candida glabrata adherence on denture liners. Another aim was to correlate materials’ surface roughness (Ra) to Candida adherence. Specimens of three denture liners (soft and hard polymethyl methacrylate (PMMA)-based and soft silicone-based) were prepared and had their Ra measured. Specimens were randomly divided to adherence assays with C. albicans or C. glabrata . After contamination with the fungi, specimens were treated with an enzymatic cleanser solution, a cleanser solution or a 0.5% NaOCl solution by soaking for 3, 15 or 10 min, respectively. Control group specimens were soaked in distilled water for 15 min. Number of remaining Candida cells after treatment was determined by light microscopy (×400). Analysis of variance ( α  = 0.05) showed that Ra of the silicone-based liner was lower than that of the PMMA-based liners ( p  < 0.05). The overall results showed high C. glabrata adherence ( p  < 0.001), while the lowest levels of remaining Candida cells were found for the treatment with 0.5% NaOCl ( p  = 0.0019). No difference among denture cleansers and control was found ( p  = 0.19). There was no correlation between Ra and C. albicans or C. glabrata adherence in all materials tested. The only treatment able to reduce both Candida species adherence on all materials tested was 0.5% NaOCl solution.

The purpose of this study was to investigate the tensile strength of the bond between a silicone lining material and heat-cured polymethyl methacrylate (PMMA) denture base resin after Er:YAG laser treatment with different pulse durations and energy levels. PMMA test specimens were fabricated and each received one of six surface treatments: no treatment (control), and five Er:YAG laser treatments comprising (1) 100 mJ, 1 W, long pulse duration, (2) 200 mJ, 2 W, long pulse duration, (3) 200 mJ, 2 W, very short pulse duration, (4) 300 mJ, 3 W, long pulse duration, and (5) 400 mJ, 4 W, long pulse duration. The resilient liner specimens ( n  = 15) were processed between two PMMA blocks. The tensile strengths of the bonds between the liners and PMMA were determined using a universal testing machine at a crosshead speed of 5 mm/min. The mode of failure was characterized as cohesive, adhesive, or mixed modes. One-way ANOVA and the post hoc Tukey-Kramer multiple comparisons test were used to analyze the data ( α  = 0.05). There was a statistically significantly difference in tensile bond strength between laser-treated and untreated specimens ( P  < 0.05). The 300-mJ, 3 W, long pulse duration laser treatment produced the highest mean tensile bond strength. In addition, the long pulse duration treatments resulted in greater bond strength than very short pulse duration treatment ( P  < 0.05). Laser irradiation produced significant surface texture changes of the denture base material and improved the adhesion between denture base and soft lining material. In addition, different pulse durations and energy levels were found to effectively increase the strength of the bond.

Current treatment protocols for patients diagnosed with denture stomatitis are under scrutiny, and alternative options are being explored by researchers. The aim of this systematic review was to determine if silver nanoparticles inhibit the growth of Candida albicans, and the research question addressed was: In adults, do silver nanoparticles inhibit the growth of Candida albicans in acrylic dentures and denture liners compared to normal treatment options. A systematic review was the chosen methodology, and criteria were formulated to include all types of studies, including clinical and laboratory designs where the aim was tested. Of the 18 included studies, only one was a clinical trial, and 17 were in vitro research. The inhibition of candidal growth was based on the % concentration of AgNPs included within the denture acrylic and denture liner. As the % AgNPs increased, candida growth was reduced. This was reported as a reduction of candidal colony forming units in the studies. The quality of the included studies was mostly acceptable, as seen from the structured and validated assessments completed.

This study investigated the antimicrobial efficacy and mechanical strength of hard and soft denture liners modified with benzalkonium chloride (BAC). The specimens (1 mm thickness, 8 mm diameter) were prepared by mixing 0.5, 1, 2 and 5 wt% BAC with soft (Sofreliner Medium, Tokuyama) and hard (Rebase II, Tokuyama) denture liners (n = 5/group). BAC was not added to the controls. Candida albicans ATCC 28366 (A550 = 0.5) and Streptococcus mutans Ingbritt suspensions (A550 = 0.35) were pipetted onto the specimens, and incubated for 4 h. The viable cells were collected, and determined by plate-culturing (CFU). The tests were repeated after the specimens were soaked in distilled water for 7 days. The mechanical strengths were evaluated by tear and 4-point flexural strength tests for soft and hard liners, respectively. The data were analyzed with ANOVA and Tukey’s HSD tests at p = 0.05. C. albicans viability was lost in all groups of BAC-modified soft liners (p < 0.001), and S. mutans viability was reduced (p < 0.01), except of soaked BAC 0.5 wt% group (p > 0.05). For the hard liner, BAC 5 wt% killed the C. albicans and S. mutans cells both before and after soaked in water (p < 0.001). BAC 2 wt% showed comparable tear strength with the soft liner control (p > 0.05). BAC did not reduce the flexural strength of the hard liner (p > 0.05), except of BAC 5 wt% group (p < 0.01). BAC can be a promising agent reducing the C. albicans and S. mutans viability on the soft and hard denture liner surfaces.

Failure of the bond between the acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to investigate the effect of different surface treatments (sandblasting, Er:YAG, Nd:YAG, and KTP lasers) on tensile bond strength of silicone-based soft denture liner. Polymethyl methacrylate test specimens were fabricated and each received one of eight surface treatments: untreated (control), sandblasted, Er:YAG laser irradiated, sandblasted + Er:YAG laser irradiated, Nd:YAG laser irradiated, sandblasted + Nd:YAG laser irradiated, KTP laser irradiated, and sandblasted + KTP laser irradiated. The resilient liner specimens ( n  = 15) were processed between two polymethyl methacrylate (PMMA) blocks. Bonding strength of the liners to PMMA were compared by tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min. Kruskal–Wallis and Wilcoxon tests were used to analyze the data (α = 0.05). Altering the polymethyl methacrylate surface by Er:YAG laser significantly increased the bond strengths in polymethyl methacrylate/silicone specimens, however, sandblasting before applying a lining material had a weakening effect on the bond. In addition, Nd:YAG and KTP lasers were found to be ineffective for increasing the strength of the bond.