Effect of Hypochlorites on the Compressive Strength and Surface Hardness of Type V Dental Stone: An In Vitro Study.

AIM: The study aimed to evaluate the compressive strength and surface hardness of a type V dental stone after hypochlorite disinfection. MATERIALS AND METHODS: Two types of specimens were made according to the American Dental Association (ADA) specification no. 25 for each wet compressive strength, dry compressive strength, and surface hardness. The specimens were split into three groups with 30 samples each according to the type of disinfection. All specimens were immersed in their respective disinfecting solutions for 30 minutes at room temperature and after removal, they were left to dry for 24 hours at room temperature. Total five cycles of immersion and drying were followed. A compressive strength test was done using a universal testing machine. Wet compressive strength was tested one hour after the last cycle and dry compressive strength was tested 7 days after the last cycle. Surface hardness was measured after 48 hours using Vickers hardness test. The results were statistically analyzed. RESULTS: There was a statistical difference between the calcium hypochlorite and sodium hypochlorite groups for both dry and wet compressive strength. The mean wet compressive strength of calcium hypochlorite was higher when compared to the sodium hypochlorite group and it was statistically significant (p = 0.042). The results were similar and statistically significant (p = 0.003) for dry compressive strength. When the mean surface hardness of the sodium hypochlorite (As) group was compared to calcium hypochlorite the results were highly significant (p = 0.0001) with the mean surface hardness of the calcium hypochlorite group more than the sodium hypochlorite group. CONCLUSION: Calcium hypochlorite used as a disinfectant showed better compressive strength and surface hardness when compared to sodium hypochlorite as a disinfectant. CLINICAL SIGNIFICANCE: Dental casts poured in the contaminated impressions which might not be disinfected at all or properly. They also come in contact with the prosthesis that might be tried inside the patient's mouth and sent to a lab for corrections without disinfecting the cast causing cross-contamination between patients, dentists, and laboratory personnel. However, immersion disinfection with sodium or calcium hypochlorite might affect important properties of the cast. Any negative effect on the mechanical or physical properties of the cast will affect the final outcome of the prosthesis.

Flexural Strength of Surface-Treated Heat-Polymerized Acrylic Resin after Repair with Aluminum Oxide-Reinforced Autopolymerizing Acrylic Resin.

BACKGROUND: A fracture of denture base in situ often occurs through a fatigue mechanism, which over a period of time leads to the formation of small cracks, resulting in fracture. AIM AND OBJECTIVE: To evaluate the flexural strength of repaired heat-polymerized acrylic resin, with different percentage of aluminum oxide (Al2O3) added to the repair resin and effect of two different surface treatments on the flexural strength of repaired heat-polymerized acrylic resin and also to evaluate quantification of filler particles using scanning electron microscopy. MATERIALS AND METHODOLOGY: Fifty specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association specification no. 12 (65 mm × 10 mm × 2.5 mm). Al2O3<50 nm particle size was silanized using metal alloy primer before incorporation in polymer. Two different percentages of Al2O3 nanoparticles, that is, 1% and 1.5% were added to autopolymerizing acrylic resin which was used as repairing material. RESULTS: The study showed that repair resin incorporated with 1.5% Al2O3 in the group surface treated with silicon carbide paper improved the flexural strength of denture base resin. A proper filler distribution and deep penetration within the polymer matrix were observed by scanning electron microscope in the same group.

Effect of incorporating seed oils on the antifungal property, surface roughness, wettability, weight change, and glucose sorption of a soft liner.

STATEMENT OF PROBLEM: The colonization of Candida albicans on soft liners causes the deterioration of material surface properties and denture stomatitis. PURPOSE: The purpose of this in vitro study was to investigate the effect of incorporating seed oil on the antifungal properties, surface roughness, wettability, weight changes, and glucose adsorption/absorption of a soft liner. MATERIAL AND METHODS: Centratherum anthelminticum, Ocimum sanctum Linn, and Linum usitatissimum seed oils were incorporated into a soft liner, and the diameter of the inhibition zone (DIZ) was calculated relative to the growth of C albicans at 24, 48, and 72 hours and 7 days. The effect of incorporating oil on wettability was evaluated with the contact angle analyzer, and effect on surface roughness was evaluated with scanning electron microscopy. Weight changes and absorption/adsorption of glucose to the soft liner were estimated. Data were analyzed by using paired Student t tests and 2-way ANOVA (α=.01). RESULTS: Soft liner with 800 µL each of C anthelminticum and O sanctum oils showed complete inhibition at 72 hours; the DIZ on day 7 were 31.66 ±1.20 mm and 29.66 ±1.46 mm, respectively. The change in weight between time intervals differed significantly between conditions (P<.01). The addition of oils decreased the surface roughness and improved wettability significantly for O sanctum and C anthelminticum specimens (P<.01). At 72 hours, 5.5 mg of glucose was detected in the positive control, whereas no glucose was detected in the oil specimens. CONCLUSIONS: The addition of the seed oils of C anthelminticum and O sanctum to the soft liner significantly reduced the growth of C albicans, improved wettability, reduced surface roughness, and minimized the absorption and adsorption of glucose.