Antimicrobial Effect of Different Sizes of Nano Zinc Oxide on Oral Microorganisms.

OBJECTIVES: The purpose of the present study was to evaluate the antimicrobial effect of various sizes and concentrations of zinc oxide (ZnO) nanoparticles on Streptococcus mutans (S. mutans), Enterococcus faecalis (E. faecalis), Lactobacillus fermentum (L. fermentum), and Candida albicans (C. albicans). MATERIALS AND METHODS: Solutions at the concentration of 10 µg/ml were prepared using 20-nm, 40-nm, and 140-nm nano ZnO (nZnO) powder. The antimicrobial effect of nZnO was determined using the disk diffusion method. The inhibition zone (mm) was measured using a ruler. Data were analyzed by analysis of variance (ANOVA) and the Bonferroni correction. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of nZnO were determined using the broth microdilution method in Mueller-Hinton Agar (MHA) for S. mutans and E. faecalis, De Man, Rogosa, and Sharpe (MRS) agar, and Sabouraud Dextrose Agar (SDA). RESULTS: The greatest inhibition zones were observed against S. mutans with 20-nm and 40-nm nZnO, while 140-nm nZnO formed the greatest inhibition zones against S. mutans and E. faecalis. The smallest inhibition zones were observed against C. albicans with the three nZnO particle sizes. The MICs for C. albicans with 40-nm and 140-nm particles and for L. fermentum with 140-nm particles were higher than 10 µg/ml. A significant correlation was found between the particle size and the antibacterial activity against S. mutans (P=0.00), L. fermentum, and E. faecalis (P<0.02). CONCLUSION: The antimicrobial activity of nZnO increases with decreasing the particle size. The greatest antimicrobial effect was observed against S. mutans and E. faecalis. S. mutans is more sensitive to the changes in the particle size compared to other bacteria.

Antimicrobial Activity of the Essential Oil Obtained from the Seed and Oleo-Gum-Resin of Ferula Assa-Foetida against Oral Pathogens.

OBJECTIVES: The objective of this study was to evaluate the antimicrobial activity of the essential oil obtained from oleo-gum-resin and seeds of Ferula assa-foetida. MATERIALS AND METHODS: Ferula assa-foetida plants were collected from Tabas, Yazd Province, Iran, during summer 2017. Then, essential oils were obtained from its seeds and oleo-gum-resin using hydrodistillation. Gas chromatography-mass spectrometry (GC-MS) test was performed to determine the contents of the essential oils. Four different concentrations of each oil were prepared (2.5, 5, 10, and 20 µg/ml), and the antimicrobial activity of each dose against four oral bacteria (Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguis, Streptococcus salivarius, and Lactobacillus rhamnosus) was evaluated using the disk diffusion method. The data were analyzed using analysis of variance (ANOVA) and Kruskal-Wallis test in SPSS 17 software. RESULTS: The GC-MS findings exhibited that the main compounds found in essential oils yielded from the seeds and oleo gum resin were (Z) -1-propenyl sec-butyl disulfide and (E) -1-propenyl sec-butyl disulfide. Ferula assa-foetida plant showed a significant antimicrobial effect (P<0.05). The essential oil from Ferula assa-foetida oleo-gum-resin had significantly stronger antibacterial properties compared to the essential oil from Ferula assa-foetida seeds (P<0.001). Both essential oils showed antibacterial properties similar to that of Chlorhexidine. The growth inhibition zone was significantly dependent on the essential oil concentration for all bacteria (P<0.05). CONCLUSION: Our study revealed that essential oils from seeds and oleo-gum-resin of Ferula assa-foetida have antimicrobial properties. More laboratory studies are required to reach a definitive conclusion.

Evaluation of micro shear bonding strength of two universal dentin bondings to superficial dentin by self etch and etch-and-rinse strategies.

BACKGROUND: Universal bondings can be used either with the etch-and-rinse or self-etch technique. Thus, the present study was done to evaluate the micro-shear bonding strength of two types of Universal Bondings to superficial dentin i.e self-etch and etch and rinse. MATERIAL AND METHODS: The samples included 70 tooth blocks taken from 35 extracted sound premolar teeth. The superficial dentin was exposed to grinding by 800 grit silicon carbide Disk. The samples were randomly divided into 5 equal groups (14 samples in each group). Scotch bond universal (3M/USA) and All bond universal (BISCO/USA) were applied by self-etch and etch and rinse technique in group 1-4 and Adper Single bond 2 (3M/USA) was used in group 5 as etch and rinse for the control group. Z250 XT (3M/USA) resin composite was bonded in tygon tube on surfaces of samples and were cured. Specimens were stored in distilled water at 37ºC for 24 h and then subjected to the micro shear bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed by two-way ANOVA and Tukey test. Failure mode was determined using a stereomicroscope under 20X magnification. Significance level was considered 0/05. RESULTS: The mean of micro-shear bonding strength and Standard Deviation of groups in Mega Pascal are respectively: 35.74 (6.21), 29.50 (3.89), 24.60 (3.53), 31.47 (4.73), 18.09 (3.87). The self-etch technique for Scotch bond Universal and the etch and rinse technique for All bond Universal showed higher micro shear bonding strength. Adper single bond 2 showed the lowest bond strength to a significant level in comparison to other groups (p<0.05). Failure mode was predominantly adhesive. CONCLUSIONS: The micro shear bonding strength of universal adhesives was highly bonding-dependent. Universal bondings had higher micro-shear bonding strength than Adper single bond 2. Key words:Bond strength, dentin, self-etch, etch-and-rinse, universal bonding.

The efficacy of eutectic mixture of local anesthetics as a topical anesthetic agent used for dental procedures: A brief review.

Dental pain management is one of the most critical aspects of modern dentistry which might affect patient's quality of life. Several methods are suggested to provide a painless situation for patients. Desensitization of the oral site using topical anesthetics is one of those methods. The improvements of topical anesthetic agents are probably one of the most important advances in dental science in the past 100 years. Most of them are safe and can be applied on oral mucosa with minimal irritation and allergic reactions. At present, these agents are various with different potent and indications. Eutectic mixture of local anesthetics (EMLA) (lidocaine + prilocaine) is a commercial anesthetic agent which has got acceptance among dental clinicians. This article provides a brief review about the efficacy of EMLA as a topical anesthetic agent when used during dental procedures.

Effect of different fiber post surface treatments on microtensile bond strength to composite resin.

STATEMENT OF PROBLEM: The interface of fiber post and composite resin is a site of potential failure of adhesion. Improving this interface adhesion through different pretreatments of the fiber post surface has been suggested, but the results are controversial. PURPOSE: The purpose of this in vitro study was to evaluate the effect on the bond strength to composite resin of pretreating glass fiber post surfaces with hydrogen peroxide, phosphoric acid, and a silane coupling agent. MATERIAL AND METHODS: Glass fiber posts were treated for 1 or 5 minutes with 30% hydrogen peroxide or 35% phosphoric acid. Treated posts were divided into silanization and no silanization groups. Control groups included no treatment or treatment with silanization alone (total of 10 groups; n=14). Composite resin was bonded to the fiber posts, and the specimens were cut into beams with the fiber post in the middle and the composite resin at both sides. The beams were attached to a mechanical testing device, and microtensile bond strength was evaluated. Fracture modes were assessed using stereomicroscopy. Statistical analysis was done with 3- and 2-way ANOVA (α=.05). Additional specimens were evaluated with a scanning electron microscope (SEM) to evaluate the effect of treatments on the characteristics of fiber post surfaces. RESULTS: The highest bond strength values were found in the group treated with phosphoric acid for 5 minutes with silanization, followed by the group treated with silanization alone. ANOVA showed a statistically significant effect for silanization (P<.05), but no statistically significant effect for surface treatment. SEM evaluation revealed cracked and dislodged superficial fibers in all groups, with no obvious difference in fiber exposure among the groups. CONCLUSIONS: The silane coupling agent had a significant effect on the bond strength of the tested glass fiber posts to composite resin, whereas 30% hydrogen peroxide or 35% phosphoric acid did not.

Is acupuncturing effective in controlling the gag reflex during dental procedures? A review of literature.

Traditional acupuncture has been introduced more than 2500 years ago which provides an alternative and complementary option during clinical practices. Its main mechanism is based on stimulating the nerves by altering the processes and perception of pain transmitters. It facilitates releasing natural pain relievers such as endorphins and serotonin. Its success for various dental procedures has been proved earlier. However, its effects on controlling the gag reflex seem to be overlooked. The gag reflex is recognized as a protective reaction for stopping the entrance of any foreign bodies into the oropharynx. Pronounced gag reflexes can have negative impacts on the quality of dental procedures. Many techniques have been suggested for managing this reflex and acupuncturing is one of those which seems to be overlooked recently. The aim of this paper is reviewing the published high-quality researches about the efficacy of this technique for eliminating the gag reflex during dental procedures.

Effects of Thermal and Mechanical Load Cycling on the Dentin Microtensile Bond Strength of Single Bond-2.

BACKGROUND: Different studies have shown the uncertain effects of thermal cycling (TC) and mechanical load cycling (MC) on the dentin microtensile bond strength (µTBS) of composites. This study designed to investigate the effects of TC and MC on the dentin µTBS of single bond-2. MATERIALS AND METHODS: Flat dentinal surface was prepared on 48 sound extracted human third molar teeth, and were bonded by single bond-2 adhesive and Z250 resin composite. The teeth were randomly divided into eight equal groups, according to the thermal/mechanical protocol. TC and MC were proceeded at 5-55°C and 90 N with 0.5 Hz. Then restorations were sectioned to shape the hour-glass form and subjected to µTBS testing at a speed of 0.5 mm/min. To evaluate the bonding failure, the specimens were observed under the scanning electron microscope. The results were statistically analyzed with analysis of variance, t-test, Tukey HSD and post-hoc by using SPSS software version 17 at a significant level of 0.05. RESULTS: µTBS of all groups were significantly lower than the control group (P < 0.001). Adhesive failure was predominant in all groups and increased with TC and MC. CONCLUSIONS: TC and MC had an adverse effect on µTBS of the tested adhesive resin to dentin.

Effect of Pre-heating on Microtensile Bond Strength of Composite Resin to Dentin.

OBJECTIVE: Direct composite resin restorations are widely used and the impact of different storage temperatures on composites is not well understood. The purpose of this study was to evaluate the microtensile bond strength of composite to dentin after different pre-curing temperatures. MATERIALS AND METHODS: Occlusal surfaces of 44 human molars were ground with diamond burs under water coolant and polished with 600 grit silicon carbide papers to obtain flat dentin surfaces. The dentin was etched with 37% phosphoric acid and bonded with Adper Single Bond 2 according to the manufacturer's instructions. The specimens were randomly divided into two groups (n=22) according to the composite resin applied: FiltekP60 and Filtek Z250. Each group included three subgroups of composite resin pre-curing temperatures (4°C, 23°C and 37°C). Composite resins were applied to the dentin surfaces in a plastic mold (8mm in diameter and 4mm in length) incrementally and cured. Twenty-two composite-to-dentin hour-glass sticks with one mm(2) cross-sectional area per group were prepared. Microtensile bond strength measurements were made using a universal testing machine at a crosshead speed of one mm/min. For statistical analysis, t-test, one-way and two-way ANOVA were used. The level of significance was set at P<0.05. RESULTS: Filtek P60 pre-heated at 37ºC had significantly higher microtensile bond strength than Filtek Z250 under the same condition. The microtensile bond strengths were not significantly different at 4ºC, 23ºC and 37ºC subgroups of each composite resin group. CONCLUSION: Filtek P60 and Filtek Z250 did not have significantly different microtensile bond strengths at 4ºC and 23ºC but Filtek P60 had significantly higher microtensile bond strength at 37 ºC. Composite and temperature interactions had significant effects on the bond strength.