Effect of comonomer of methacrylic acid on flexural strength and adhesion of Staphylococcus aureus to heat polymerized poly (methyl methacrylate) resin: An in vitro study.

AIMS AND OBJECTIVE: The purpose of the present study was to evaluate and compare flexural strength and Staphylococcus aureus adhesion of heat-activated poly (methyl methacrylate [MMA]) resin modified with a comonomer of methacrylic acid (MAA) and MMA monomer. MATERIALS AND METHODS: Comonomer preparation was done with the addition of varying concentration of MAA (0, 15, 20, and 25 wt %) to the MMA of conventional heat-activated denture base resin to prepare the specimens. Prepared specimens were stored in distilled water at 37°C for 1 day and 1 week before the evaluation of flexural strength and microbial adhesion. Flexural strength was measured using a universal testing machine at a crosshead speed for 2 mm/min (n = 10). Microbial adhesion (colony-forming unit [CFU]) was evaluated against S. aureus using a quadrant streaking method (n = 5). Data were subjected to one-way ANOVA, and the significant differences among the results were subjected to Tukey's HSD test. P < 0.05 was considered statistically significant. RESULTS: Addition of MAA to the MMA monomer was found to significantly reduce the adhesion of S. aureus for all the groups. Reduction of CFU of S. aureus was found be more significant for Group 3 as compared to control, both at 1-day (P < 0.001) and 1-week (P < 0.002) storage in distilled water. However, no statistically significant changes in the flexural strength were observed with the addition of MAA at 1-day (P = 0.52) and 1-week (P = 0.88) time interval. CONCLUSION: Addition of MAA to conventional denture base resin reduced the microbial adhesion without significantly affecting the flexural strength.

Comparative evaluation of shear bond strength of two different chairside soft liners to heat processed acrylic denture base resin: An in vitro study.

BACKGROUND: Chairside softliners are used more frequently than is reported and studies regarding the bond strength of chairside softliners to heat-polymerized denture base resin are few and limited. Hence, this study was conducted to comparatively evaluate the shear bond strength of two chairside soft relining materials viz., autopolymerizing plasticized acrylic resin liner and a silicone-based liner bonded to heat polymerized polymethyl methacrylate denture base resin and to analyze the mode of interfacial bond failure. MATERIALS AND METHODS: Forty test specimens (n = 40) were prepared by bonding plasticized acrylic- and silicone-based soft liner to heat polymerized acrylic resin blocks. Twenty specimens, ten from each group, were subjected to thermal cycling and later to shear bond strength testing. The debonded specimens were then qualitatively analyzed for the mode of failure using scanning electron microscopy. The results obtained were tabulated and statistically analyzed. RESULTS: The mean shear bond strength values obtained for acrylic-based soft liner before and after thermal cycling were 0.3365 ± 0.025 MPa and 0.3164 ± 0.04 MPa, respectively. The mean shear bond strength values obtained for silicone-based soft liner before and after thermal cycling were 0.4159 ± 0.025 MPa and 0.4335 ± 0.02 MPa, respectively. Silicone-based soft liner showed higher shear bond strength than the acrylic-based both before and after thermal cycling (P = 0.0001). Scanning electron microscopy analysis showed a predominantly mixed mode of failure with silicone-based liner and predominantly adhesive mode of failure with acrylic-based soft liner. CONCLUSION: The silicone-based soft liner showed higher shear bond strength to heat polymerized acrylic resin than acrylic-based soft liner both before and after thermal cycling.

Comparative study of the shear bond strength of various veneering materials on grade II commercially pure titanium.

PURPOSE: To compare the shear bond strength of various veneering materials to grade II commercially pure titanium (CP-Ti). MATERIALS AND METHODS: Thirty specimens of CP-Ti disc with 9 mm diameter and 10 mm height were divided into three experimental groups. Each group was bonded to heat-polymerized acrylic resin (Lucitone 199), porcelain (Triceram), and indirect composite (Sinfony) with 7 mm diameter and 2 mm height. For the control group (n=10), Lucitone 199 were applied on type IV gold alloy castings. All samples were thermocycled for 5000 cycles in 5-55℃ water. The maximum shear bond strength (MPa) was measured with a Universal Testing Machine. After the shear bond strength test, the failure mode was assessed with an optic microscope and a scanning electron microscope. Statistical analysis was carried out with a Kruskal-Wallis Test and Mann-Whitney Test. RESULTS: The mean shear bond strength and standard deviations for experimental groups were as follows: Ti-Lucitone 199 (12.11 ± 4.44 MPa); Ti-Triceram (11.09 ± 1.66 MPa); Ti-Sinfony (4.32 ± 0.64 MPa). All of these experimental groups showed lower shear bond strength than the control group (16.14 ± 1.89 MPa). However, there was no statistically significant difference between the Ti-Lucitone 199 group and the control group, and the Ti-Lucitone 199 group and the Ti-Triceram group. Most of the failure patterns in all experimental groups were adhesive failures. CONCLUSION: The shear bond strength of veneering materials such as heat-polymerized acrylic resin, porcelain, and indirect composite to CP-Ti was compatible to that of heatpolymerized acrylic resin to cast gold alloy.

Comparative study of the shear bond strength of various veneering materials on grade II commercially pure titanium

PURPOSE: To compare the shear bond strength of various veneering materials to grade II commercially pure titanium (CP-Ti). MATERIALS AND METHODS: Thirty specimens of CP-Ti disc with 9 mm diameter and 10 mm height were divided into three experimental groups. Each group was bonded to heat-polymerized acrylic resin (Lucitone 199), porcelain (Triceram), and indirect composite (Sinfony) with 7 mm diameter and 2 mm height. For the control group (n=10), Lucitone 199 were applied on type IV gold alloy castings. All samples were thermocycled for 5000 cycles in 5-55degrees C water. The maximum shear bond strength (MPa) was measured with a Universal Testing Machine. After the shear bond strength test, the failure mode was assessed with an optic microscope and a scanning electron microscope. Statistical analysis was carried out with a Kruskal-Wallis Test and Mann-Whitney Test. RESULTS: The mean shear bond strength and standard deviations for experimental groups were as follows: Ti-Lucitone 199 (12.11 +/- 4.44 MPa); Ti-Triceram (11.09 +/- 1.66 MPa); Ti-Sinfony (4.32 +/- 0.64 MPa). All of these experimental groups showed lower shear bond strength than the control group (16.14 +/- 1.89 MPa). However, there was no statistically significant difference between the Ti-Lucitone 199 group and the control group, and the Ti-Lucitone 199 group and the Ti-Triceram group. Most of the failure patterns in all experimental groups were adhesive failures. CONCLUSION: The shear bond strength of veneering materials such as heat-polymerized acrylic resin, porcelain, and indirect composite to CP-Ti was compatible to that of heatpolymerized acrylic resin to cast gold alloy.

Effect of denture cleansers on metal ion release and surface roughness of denture base materials

Chemical disinfectants are usually associated with mechanical methods to remove stains and reduce biofilm formation. This study evaluated the effect of disinfectants on release of metal ions and surface roughness of commercially pure titanium, metal alloys, and heat-polymerized acrylic resin, simulating 180 immersion trials. Disk-shaped specimens were fabricated with commercially pure titanium (Tritan), nickel-chromium-molybdenum-titanium (Vi-Star), nickel-chromium (Fit Cast-SB Plus), and nickel-chromium-beryllium (Fit Cast-V) alloys. Each cast disk was invested in the flasks, incorporating the metal disk to the heat-polymerized acrylic resin. The specimens (n=5) were immersed in these solutions: sodium hypochlorite 0.05%, Periogard, Cepacol, Corega Tabs, Medical Interporous, and Polident. Deionized water was used as a control. The quantitative analysis of metal ion release was performed using inductively coupled plasma mass spectrometry (ELAN DRC II). A surface analyzer (Surftest SJ-201P) was used to measure the surface roughness (µm). Data were recorded before and after the immersions and evaluated by two-way ANOVA and Tukey's test (α=0.05). The nickel release proved most significant with the Vi-Star and Fit Cast-V alloys after immersion in Medical Interporous. There was a significant difference in surface roughness of the resin (p=0.011) after immersion. Cepacol caused significantly higher resin roughness. The immersion products had no influence on metal roughness (p=0.388). It could be concluded that the tested alloys can be considered safe for removable denture fabrication, but disinfectant solutions as Cepacol and Medical Interporous tablet for daily denture immersion should be used with caution because it caused greater resin surface roughness and greater ion release, respectively.

Desinfetantes químicos são normalmente associados a métodos mecânicos para remover manchas e reduzir a formação do biofilme. Este estudo avaliou o efeito de desinfetantes na liberação de íons metálicos e na rugosidade superficial do titânio comercialmente puro, ligas metálicas e resina acrílica termopolimerizável, simulando 180 ensaios de imersões. Espécimes em formato de discos foram confeccionados com titânio comercialmente puro (Tritan), liga de níquel-cromo-molibdênio-titânio (Vi-Star), liga de níquel-cromo (Fit Cast-SB Plus) e liga de níquel-cromo-berílio (Fit Cast-V). Os espécimes (n=5) foram imersos nestas soluções: hipoclorito de sódio a 0,05%, Periogard, Cepacol, Corega Tabs, Medical Interporous e Polident. Como controle, foi utilizada a água deionizada. A análise quantitativa de liberação de íons metálicos foi realizada por meio de espectrometria de massa com plasma indutivamente acoplado (ELAN DRC II). O rugosímetro (Surftest SJ-201P) foi utilizado para medir a rugosidade superficial (µm). Os dados foram registrados antes e depois das imersões e avaliados por ANOVA com dois fatores e teste de Tukey (α=0,05). A liberação de níquel provou ser mais expressiva nas ligas Vi-Star e Fit Cast-V após a imersão em Medical Interporous. Houve diferença significante na rugosidade superficial da resina (p=0,011) após a imersão. O Cepacol causou maior rugosidade superficial de forma significativa. Os produtos de imersão não influenciaram nos resultados da rugosidade do metal (p=0,388). Pode-se concluir que as ligas metálicas testadas podem ser consideradas seguras para a fabricação de próteses removíveis, mas as soluções desinfetantes como o Cepacol e a pastilha Medical Interporous para a imersão diária da prótese devem ser utilizados com cautela, pois causaram maior rugosidade superficial da resina e maior liberação de íons, respectivamente.