Bi-antibiotic-impregnated bone cements (BIBCs) are widely used in orthopaedics as a prophylactic agent (depot) to address post-surgical infections. Although hardness is widely considered a viable index to measure the integrity of the cement structure, there are few specific studies involving changes in hardness characteristics of BIBCs post elution of high doses of two widely used antibiotics: tobramycin and gentamicin. Increased doses of antibiotics and increased duration of elution may also decrease the hardness of polymethyl methacrylate (PMMA) bone cement, thus increasing the chances of shattering, scratching, and deformation.In this project, we have investigated the changes in surface hardness of five different antibiotic-loaded specimens: 0.5 g tobramycin and 0.5 g gentamicin together, 1 g tobramycin, 1 g gentamicin, 5 g tobramycin and 5 g gentamicin together, and 10 g tobramycin (each added to 40 g of PMMA), post elution for various time periods (1, 3, and 21 days). The effect of hydration on the hardness of bone cement was studied to replicate in vivo conditions. The micro-indentation tester (Buehler m5103) was utilized to determine if the increased antibiotic loads would compromise the integrity of the bone cement matrix.The results demonstrated that the amount of drug initially incorporated determined the hardness of the cement post elution. As compared to the control (no antibiotic), specimens containing 1 and 10 g of antibiotic exhibited over 50% and 73% decrease in hardness, respectively. The different treatment durations (post 1 day) as well as the hydration conditions had insignificant effect on the hardness of the cement.

In the present paper, the effects of nanoclay and nano calcium carbonate on polypropylene nano composites micro hardness are assessed using Vickers test. Also, a 3D finite element model of Vickers test has been simulated by Abaqus code to compare to the experimental results. The Drucker-Prager yield criterion has been used to predict the polymeric composite plastic deformation. The Drucker-Prager parameters implemented in the numerical model are determined by a tension and a compression test separately. Two associative and non-associative plastic flow assumptions are considered and an appropriate dilation angle is derived by minimizing the error difference of experimental and the numerical results. Furthermore, micromechanical and macromechanical models are investigated to predict nanoparticles effect on the polypropylene microhardness. Although the results show that analytical models including Marsh and rule of mixture models have suitable accuracy (about 10% error), excellent results (less than 2% error) can be obtained by selecting appropriate dilation angle value in the numerical method. Moreover, experimental evidences show that adding nanoclay and nano calcium carbonate increases elastic modulus, tensile and compressive yield stress as well as microhardness of the polypropylene.

Background and Aim: Together with the controversy which exists in the efficacy of new PAC light curing units, this study evaluated the irradiation effect of plasma ARC and halogen light curing units on the microhardness of three resin composites.Materials and Methods: In this experimental study, two light - curing units including Remecure CL 15 (PAC) (with the output of 1600 mW/cm2) and Arialux (QTH) (with the output of 710 mW/cm2) were used. Six specimens of three type of resin composite were prepared in a steel mold with 2mm thickness. The three composites were CeramX (Dentsply), Heliomolar (Vivadent) and Z100 (3M). Curing time with Remecure was 5 seconds and with Arialux was as the composite manufacturer recommended. After 24 hours, vickers hardness measurements on top and bottom surfaces of each specimen were made and the bottom/top vickers hardness (BIT VHN) was determined. Microhardness of two surfaces in each group was compared by t, 2-way ANOVA and Tukey tests.Results: For CeramX composite two light curing units showed the same microhardness on the top and bottom surfaces. Heliomolar showed significantly lower values of microhardness on both surfaces and BIT VHN with Remecure. In Z100 specimens microhardness (on both surfaces) was lower with Remecure but BIT VHN was the same (P<0.05). Except Heliomolar specimens who were cured by Remecure, BIT VHN was acceptable in all groups (more than 80%).Conclusion: The efficiency of Remecure unit in manufacturers' instruction time was equivalent or lower than conventional halogen light depending on the type of resin composite

Objectives This study aimed to synthesize an herbal remineralizing paste containing the extracts of Miswak, licorice, aloe vera, propolis, and honey and compare its effect with 5% sodium fluoride (NaF) and 1. 23% acidulated phosphate fluoride (APF) on demineralized enamel microhardness. Methods This experimental study was conducted on 72 extracted sound premolars. After obtaining the extracts and synthesis of the herbal paste, the baseline microhardness was measured, and the samples underwent a 14-day pH cycling. Next, the teeth were randomly assigned to six groups (N=12) for application of (I) 5% NaF for one minute, (II) 1. 23% APF for one minute, (III) herbal paste for one minute, (IV) herbal paste for five minutes, (V) herbal paste for 15 minutes, and (VI) herbal paste for six hours. The microhardness was measured again. Data were analyzed by one-way analysis of variance (ANOVA) (alpha=0. 05). Results The mean final microhardness was significantly higher than the primary microhardness in all groups (P<0. 05). The highest microhardness was noted in group IV, followed by II, VI, I, V and III. One-way ANOVA revealed no significant difference between the final microhardness of study groups (P=0. 97). Conclusion The effect of synthesized herbal paste on demineralized enamel microhardness was comparable to that of 5% NaF and 1. 23% APF. Due to the lack of a significant difference in duration of application, this paste may be applied for one minute to benefit from its remineralizing effects.

Background: This study aimed to assess the effects of methyl ethyl ketone (MEK) and ethyl acetate (EA) on dentin microhardness, used as resin sealer solvents. Methods: Eighty halves of single-rooted teeth were randomly divided into four groups to apply MEK, EA, chloroform, or saline solution. Vickers hardness values were measured for three root levels before and after the direct application of solvents for 5 and 15 minutes or a 1-minute application with ultrasonic agitation. The results were analyzed using repeated-measures ANOVA, and adjustments were made for comparisons with Bonferroni tests. Results: The dentin microhardness decreased in all the solvent groups (P < 0. 05). The changes in microhardness increased with prolonged exposure times, except for the saline solution group. Chloroform exhibited the most significant decrease in value. Furthermore, ultrasonic agitation elicited a more substantial decline in values. Conclusion: MEK and EA might be preferred over chloroform as a solvent for resin sealers because they offer an attenuated decrease in dentin microhardness and do not have guttapercha-dissolving properties.

Background and Aims: Bleaching agents not only affect the tooth structure, but also may alter the properties of restorative materials. The aim of this in vitro study was to evaluate the effect of different bleaching regimens on the microhardness of four tooth-colored restorative materials.Materials and Methods: Eighty specimens of four restorative materials (Microhybrid resin composite (Z250 (3M, ESPE), nanohybrid composite Z350 (3M, ESPE), packable composite P60 (3M, ESPE), and resin modified glass ionomer Vitremer (3M, ESPE)) were fabricated and were polished after 24 h with Soflex discs (3M, ESPE). Then the specimens were divided into two groups: In office bleach group, 40 specimens (10 of each restorative material) were bleached with hydrogen peroxide 37.5% for 30 min in two sessions with 7 days interval. In home bleaching group, 40 specimens were bleached with carbamid peroxide 22%, 6 h a day for 14 days. Vickers microhardness test were done before and after bleaching (baseline). Finally data were evaluated using analysis of Variance.Results: Two bleaching regimens were significantly decreased the microhardness values. In Z250 resin composite, the microhardness values before and after bleaching were 95.30 and 92.67 kg/mm2, respectively. for office bleaching (P=0.011) and 95.38 and 92.39 kg/mm2 for home bleaching (P<0.001). In Z350 resin composite, the microhardness values before and after bleaching were 98.29 and 92.41 kg/mm2, for office bleaching (P<0.001) and 97.35 and 93.44 kg/mm2 for home bleaching (P<0.001) respectively. In P60 resin composite, the microhardness values before and after bleaching were 103.10 and 96.16 kg/mm2, respectively. for office bleaching (P=0.045) and 102.61 and 98.16 kg/mm2 for home bleaching (P=0.001). In resin modified glass ionomer (Vitremer), the microhardness values before and after bleaching were 56.79 and 49.41 kg/mm2, respectively. for office bleaching (P=0.004) and 54.17 and 46.50 kg/mm2 for home bleaching (P<0.001). There was no significant difference between two bleaching agents (P=0.365).Conclusion: Dental bleaching agents decrease the microhardness of tooth-colored restorative materials.

Background & Aim: Several treatment methods have been suggested for reduction of dentin hypersensitivity such as Nd:YAG laser and Seal & Protect sealant materials. However, the effects of these methods have not been yet evaluated on dentin microhardness. The aim of this study was to compare the effect of Nd:YAG laser and Seal & Protect sealant on microhardness of dentin by using Vickers indicator. Materials & Methods: This in-vitro experimental study was conducted on forty-five freshly extracted human third molars. The buccal enamel surface was removed in order to expose the underneath dentin. Samples were randomly divided into three groups. Group one, received no treatment as controls, group two were exposed to Nd:YAG laser (1 W,10 Hz ,2 min) and the samples in third group were treated by Seal & Protect. Indentations were performed using Vickers indentor at 100 gr. load. Finally the average hardness number was calculated and statistical analysis was done with ANOVA and LSD tests. Results: The results of this study demonstrated that Nd:Yag laser irradiation can increase dentin microhardness. However, it was not statistically significant (P>0.05) when compared with control group. Low level dentin microhardness was detected in Seal & Protect group when compared to other groups (P=0.01). Also, there was significant difference between the Nd:Yag laser and Seal & Protect groups (P<0.05). Conclusion: Nd:YAG laser irradiation for treatment of dentin hypersensitivity didn't decrease dentin microhardness. In contrary, using Seal & Protect can decrease dentin microhardness.