Force needed to separate acrylic resin from primed and unprimed frameworks of different designs.

PURPOSE: Poor mechanical and chemical bondings at the interface between a framework and denture base resin have been responsible for many removable partial denture failures. This study tested the force necessary to separate acrylic resin bases from test frameworks using different acrylic retention designs (smooth metal plate, metal plate with bead retention, lattice retention, and mesh retention). The force needed to separate acrylic resin from primed test frameworks was also measured. MATERIALS AND METHODS: Eighty chromium-cobalt test frameworks were fabricated using preformed wax patterns and cast according to manufacturer's instructions. Half the specimens were primed prior to acrylic processing. The same base acrylic was used for all specimens. Separation forces that fractured acrylic resin from test frameworks were generated by a universal testing machine at a crosshead speed of 25 mm/min. Loads at failure and types of failure were recorded. Data were analyzed using ANOVA. RESULTS: The mean separation force of acrylic resin from unprimed retention designs was highest for the metal plate with beads (3.1 kN), followed by mesh (2.8 kN) and lattice (2.1 kN), and lowest (0.1 kN) for the smooth metal plate. The mean separation force for primed acrylic retention designs was highest for the metal plate with beads (4.2 kN), followed by mesh (3.4 kN) and smooth metal plate (3.0 kN), and lowest for lattice retention (2.6 kN). Bond failure occurred both adhesively at the interface between metal and acrylic resin and cohesively within the acrylic resin. Cohesive bond failure increased when specimens were primed. The rate of cohesive bond failure remained the same for primed mesh retention specimens. CONCLUSIONS: Significantly increased force was necessary to separate the acrylic from each design of primed test specimens compared with unprimed specimens of the same design. The primed metal plate with beads exhibited significantly greater separation force than the other three designs. Primed mesh had significantly greater separation force values than primed lattice and smooth metal plate. Primed lattice was significantly less retentive than the other three primed designs. Except for the retentive mesh specimens, there was higher occurrence of cohesive failures in the acrylic resin when the frameworks were primed.

The effect of complete dentures with a metal palate on candida species growth in HIV-infected patients.

PURPOSE: This in vivo investigation compared the oral candidal population between heat-cured acrylic resin and nickel-chromium-beryllium alloy in maxillary complete dentures in HIV-infected patients. MATERIALS AND METHODS: Split-palate maxillary complete dentures were fabricated for 19 HIV-infected patients: one-half of the palate was made in acrylic resin and the other half in nickel-chromium-beryllium. Patients were divided into low or high CD4+ lymphocyte count groups. Dentures were worn for 5 months. Palatal mucosa was clinically evaluated at baseline, 1, 3, and 5 months after denture insertion. Specimens were collected at 1, 3, and 5 months using a modified imprint culture method. Speciation of Candida was performed using a chromogenic culture medium. Two-sample t-test was employed to determine effects and significant interactions between the control and test groups and the low and high CD4+ lymphocyte groups. A chi(2) test analyzed and compared the results of the clinical evaluation (p < 0.05). RESULTS: Significant differences were observed in the colony counts between both materials during the third (p= 0.046) and fifth months (p= 0.039). The low CD4+ group demonstrated significant differences during the third (p= 0.03) and fifth months (p= 0.05). There were no significant differences between the species of Candida that colonized either material with the exception of Candida dubliniensis (p < 0.001) and "Others" (p < 0.001) during the first and fifth months. There were no significant differences on the clinical appearance of the palatal mucosa between both materials (p= 1.00). CONCLUSIONS: The metal base proved to be effective in decreasing the fungal growth typically present in complete dentures. Although overt clinical manifestations were not present, colony counts of Candida species were high in the acrylic resin denture bases of these patients. This investigation demonstrated that metal base complete dentures provide an important alternative dental service for edentulous HIV-positive and other patients who are particularly prone to higher incidences of fungal infections.

Colonization of Candida species in denture wearers with emphasis on HIV infection: a literature review.

Candida colonization in denture wearers, especially immunocompromised patients, can be disruptive to dental treatment and may be a barrier to patient health. The surface irregularities of acrylic resin are a factor in the entrapment of microorganisms. Consequently, controlling the spread of fungal infection in HIV-infected patients who wear removable prostheses and who are more susceptible to fungal infections because of their immunosuppression is of critical importance. This article reviews the literature on the colonization of Candida species in HIV-infected denture wearers using keywords such as complete dentures, candidiasis, and HIV-infection . The source for this review was representative English-language, peer-reviewed articles between the period of 1885 to 2003 obtained using Medline, as well as a hand search.