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Objectives: The aim of this in vitro study was to evaluate the tensile bond strength of two hard denture relining materials on denture bases fabricated from conventional, subtractive, and additive polymers. In addition, this study assessed the effect of a polymer to resin primer on the tensile bond strength of hard denture liners to different denture bases.Methods: A total of 120 hard relined denture base samples were fabricated, 40 per denture base group (Lucitone 199, Ivo Base CAD, and NextDent Denture 3D+). For each denture base group 20 samples were hard relined with one of two chair side hard denture liner (GC Reline, MucoHard). Among the hard reline groups, 10 of each group was primed with a composite to PMMA primer (Visio.link). All samples underwent thermocycling. The adhesive strength was evaluated through tensile testing. The surface contact angle was measured on each denture group sample to evaluate thewettability of the material. The data was analyzed using Inverse-variance weighted linear regression. Results: In this study overall the denture bases relined with MucoHard denture liner had significantly higherbond strength than the GC reline groups (P0.05). The highest bond strength was achieved with the combination of MucoHard denture liner and primed 3D printed denture bases. MucoHard denture liner has overall significantly higher tensile bond strength in comparison to GC reline. (P

OBJECTIVE: To assess the effect of denture cleansers on the mechanical and optical properties such as color stability, surface hardness, surface roughness, and flexural strength of the 3D printed denture acrylics in comparison to heat polymerized denture acrylics. MATERIALS AND METHODS: A total of 216 disc specimens (12 mm × 2mm) were made from Lucitone Digital Print, DENTCA Denture Base II, Formlabs denture resin, and Lucitone 199. Each type of acrylic was divided into four sub-groups, Efferdent, Polident, dish soap and control group in water. Specimens of each material were exposed to a total of 28 cycles of immersion in denture cleanser, while being stored in water in an incubator at 37°C in between cycles to test for color stability, surface roughness, microhardness and biaxial flexural strength. Baseline values were obtained for color, hardness, surface roughness, and biaxial flexural strength using a CIE L*a*b* color space by spectrophotometer, Vickers microhardness in hardness tester, line Ra by profilometer, and ball-on-three-ball fixture with universal testing machine respectively. Color, surface roughness, and surface hardness values were obtained at the 8th, 16th, and 28th cycles in order to compare color stability along with changes in surface roughness and surface hardness. Biaxial flexural strength values were performed for specimens at the 28th cycle as a destructive test to compare values of treated and untreated specimens. SEM analysis was performed to assess fracture behavior and microstructural changes. The differences between the tested materials and the treatment effects were statistically analyzed using the Tukey HSD test (a=0.05) and MANOVA test (a=0.05) RESULTS: The greatest significant change in color was seen in Lucitone 199 specimens (P value

This study aims to compare the physical properties of denture base resin after staining by beverages, treatment by four cleaning methods, and selecting the optimal cleaning method. Two hundred and ninety square Lucitone dental acrylic specimens were fabricated. Three relevant experiences are performed. Part I will compare cleaning methods effects on physical properties of denture resin. The purpose of this part is to test the effects of different cleaning methods on the physical properties of the denture resin on ideal condition (without stain). Part II will compare the staining effects on denture resin. The purpose of this part is to find the impact of different dyes on the physical properties of the denture resin without cleaning. Part III will compare staining and cleaning effects on denture resin. The purpose of this part is to select the best cleaning methods with less defect and more efficient for denture cleaning. Significance differences are found between different cleaning methods and stains. For all stain, denture cleanser combined brushing is more efficient to remove the stain than other cleaning methods. However, this method causes significate damage to denture base resin. Meanwhile, ultrasonic combine denture cleanser showed lower changes in surface roughness, weight and thickness, and higher surface hardness. In red wine staining, cleaning denture with ultrasound only showed lower differences and higher surface hardness. Within the scope of this study, the optimal selections of denture base cleaning methods for different stains are suggested. For coffee and tea stains, ultrasonication after cleanser application causes fewer effects on physical properties and better efficiency for stain removal than other cleaning methods. For red wine stains, cleaning dentures with ultrasound only cause a fewer impact on material properties and more efficient stain removal. In the clinic, home-care and cleaning protocol should explain to denture patient at the delivery appointment. Instead of giving the universal instruction, customization cleaning protocols are preferred to individual patients. Social hobbies especially the diet of the patient should be analyzed individually. According to the present study, a customized combined cleaning protocol can recommend to the individual patient and the improvement of denture longevity can be predicted.

Denture stomatitis and denture-related halitosis are two of the most prevalent denture related infectious diseases. The establishment of denture biofilm models for disease-associated pathogens is essential in further investigating the pathogenesis of these diseases. Chapter I and II of this thesis reported the successful development of denture biofilm model for Candida albican, the main pathogen of denterun stomatitis; as well as the denture models for halitosis-related bacteria, including Klebsiella pneumonia, Fusobacterium nucleatum, Tannerella forsythia, Veillonella atypica. We further demonstrated that the established denture models can be used for evaluating efficacy of denture-cleansers. Chapter III is focused on further exploring the association between denture stomatitis and denture-related halitosis. We revealed the interaction between C. albican and halitosis related pathogens using in vitro co-aggregation assay. A further investigation of the possible association between stomatitis-associated C. albicans and halitosis-associated bacteria in vivo is necessary.