Estimation of demand for tea and coffee in Australia

This study attempts to review the basic principles of the consumer demand theory in order to estimate the demand for tea and coffee in Australia. Generally the study of consumer demand theory is important because it can be used in development and production planning. Some of the commonly used systems of demand equations for empirical studies are explained. The study also attempts to explain a habit formation hypothesis and incorporate the hypothesis in the systems of demand equations. On this basis, three models of demand equations with and without habit formation are used to estimate the demand for tea and coffee in Australia. It is shown that none of the models satisfy all the general restrictions imposed on demand equations, since each one has some advantages and some disadvantages. However, through the comparison of these models it is shown that a habit formation model is justified. Tea in the Australian consumption pattern is an inferior good while coffee is a normal commodity. On the basis of the alternative functional forms, it seems that the double logarithmic system is a better model for estimating the demand for a single commodity such as tea or coffee

A Comparison between the Antimicrobial Effects of Triple Antibiotic Paste and Calcium Hydroxide against Entrococcus Faecalis

Introduction: The purpose of this study was to determine the in vitro antimicrobial ability against Entrococcus (E.) faecalis of triple antibiotic paste and its components compared with calcium hydroxide mixtures. Materials and Methods: An agar well diffusion assay and MIC method were used to determine the efficacy of the experimental medicaments in removing E. faecalis. Medicaments were divided into 9 groups; triple antibiotic powder with saline or chlorhexidine, metronidazole, ciprofloxacin, minocycline antibiotics were also separately tested (with normal saline), and Ca(OH)2 (plus normal saline or 2% chlorhexidine). These medicaments were evaluated at four concentrations of 25, 50, 100 and 200 µg per mL in an agar well diffusion test. The diameters of the growth inhibition zones for each group were recorded and compared. The minimum inhibitory concentrations (MIC) of tested medicaments that are required to kill E. faecalis were also determined. The differences between groups were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Results: The largest inhibition zones were observed for the triple antibiotic mixture/saline, triple antibiotic mixture/2% chlorhexidine and minocycline/saline, and the smallest for Ca(OH)2/saline, Ca(OH)2/2% chlorhexidine. Concentration increases produced greater antibacterial effects in all groups. The MIC determination method showed similar results. Conclusion: The results suggest that the triple antibiotic paste with either 2% chlorhexidine or normal saline would be the preferred medicament against E. faecalis and, among its three components, minocycline has the greatest antibacterial effect

Comparison of apical debris extrusion using a conventional and two rotary techniques

INTRODUCTION: Preparation techniques and instruments produce and push debris out of canals. This can induce inflammation within the periapical area. Therefore, instrumentation that causes less extrusion of debris is more desirable. The purpose of this in vitro study was to evaluate the quantity of debris extruded from the apical foramen during root canal preparation by using one hand, and two rotary instrumentation techniques. MATERIALS AND METHODS: Three different groups each with 12 mesiobuccal roots of human maxillary first molar were instrumented using either step-back technique with hand instruments, FlexMaster or Mtwo rotary system. Debris extruded from the apical foramen during canal preparation was collected. The mean dry weights of debris were compared using one-way ANOVA. RESULTS: Step-back group had a significantly greater mean weight of debris compared to the other two groups (P<0.05). Mtwo group had the lowest mean weight of debris, though it was not significantly different from FlexMaster group. CONCLUSION: According to this study, the engine driven techniques were associated with less apical debris extrusion. [Iranian Endodontic Journal 2009;4(4):135-8

Success Rate and Time for Bypassing the Fractured Segments of Four NiTi Rotary Instruments

Introduction: The aim of this in vitro study was to compare the success rate and time required for bypassing the fractured segments of four different nickel-titanium (NiTi) rotary systems. Methods and Materials: This study was conducted on the mesiobuccal canals of 60 mandibular molars with fully-formed apices. Fifteen Flex Master, K3, RaCe and Hero Shaper instruments with 0.04 taper and tip size of #30 and 25 mm in length, were obtained. These instruments were notched at a point 3 mm from the tip of the instrument and were driven into the canals using a handpiece until the instruments fractured and became lodged therein. In the next step, an endodontist tried to bypass the fractured segment using K-files. The number of bypassed samples and the time required for bypassing of each sample were recorded. The Chi-square test was used to compare the bypassing rate among the experimental groups. One-way analysis of variance followed by Tukey’s post hoc test was conducted to compare the time taken for bypassing of the fractured fragments. Results: One instrument in Flex Master group and two broken segments in each of the K3 and Hero groups were not bypassed. All of the samples in RaCe group were bypassed. No significant difference was found among four tested groups regarding rate of bypassing (P=0.738). The time taken to bypass fragments in the Hero group was significantly more than in those of K3 (P=0.047) and RaCe (P=0.024). Conclusion: Under the limitations of this study, design features of rotary files can influence the time needed to bypass separated fragments.Keywords: Instrument Fracture; Instrument Separation; File Fracture; Fractured Instrument; NiTi Rotary File; Root Canal Treatmen

Diagnosis and Treatment of a Type III Dens Invagination Using Cone-Beam Computed Tomography

A 20-year-old man presented with the history of pain and swelling in the anterior maxillary segment. The periapical radiography was indicative of a dental anomaly in right maxillary lateral incisor. Due to the insufficient information from conventional radiography, cone-beam computed tomography (CBCT) was ordered. CBCT showed apical root resorption, large apical lucency and two separate canals with distinct apical foramen (Oehlers type III dens invagination). The CBCT image was used as a guide for dentine removal with an ultrasonic tip. Conventional root canal therapy was done using lateral compaction technique. One-and two-year follow-up radiographies revealed periapical repair and absence of symptoms.Keywords: Cone-Beam Computed Tomography; Dens Invagination; Maxillary Lateral Inciso

Effect of Different Water-to-powder Ratios on the Solubility and Microhardness of Calcium-Enriched Mixture Cement

Introduction: The aim of this study was to evaluate the effect of different water-to-powder (WP) proportions on the microhardness and water solubility of calcium-enriched mixture (CEM) cement. Methods and Materials: One gram of CEM cement powder was mixed with 0.33 mL, 0.4 mL or 0.5 mL CEM liquid. For water solubility, a total of 60 specimens were prepared (n=20 per each ratio) in the disk-shaped stainless-steel molds with a height of 1.5±0.1 mm and internal diameter of 10.0±0.1 mm. The specimens of each WP ratio were randomly divided into two subgroups: half (n=10) were immersed for one day and the other half (n=10), were kept for 21 days in distilled water. The solubility was calculated as a percentage of the weight loss. To measure microhardness, a total of 30 samples were prepared (10 per each ratio, n=10). The mixtures were transferred to metallic cylindrical molds with internal dimensions of 6±0.1 mm height and 4±0.1 mm diameters. After 4 days the specimens were subjected to Vicker's test. The data were analyzed using two-way ANOVA and post-hoc Tukey’s tests at a significance level of 0.05. Results: The 0.33 WP ratio showed significantly greater microhardness value (25.98±2.77) compared to 0.4 and 0.5 proportions (P=0.004 and P<0.001 respectively). Significant differences were observed between water solubility values of different WP ratios at both time intervals (P<0.001). At both time intervals, 0.33 and 0.5 WP ratios exhibited the lowest and highest solubility, respectively. Conclusion: According to the results of this in vitro study, higher WP ratios result in lower microhardness and higher water solubility of the CEM cement. Therefore, the 0.33 WP ratio would be the ideal proportion.Keywords:Calcium-Enriched Mixture; CEM Cement; Microhardness; Solubility; Water-to-powder Ratio

Effect of Different Water-to-Powder Ratios on the Compressive Strength of Calcium-enriched Mixture Cement

Introduction: Calcium-enriched Mixture (CEM) cement is an endodontic reparative material available in the form of powder and liquid. The purpose of this in vitro study was to determine the effect of different water-to-powder (WP) proportions on the compressive strength (CS) of the cement. Method Materials and: One gram of CEM cement powder was mixed with either 0.33 g, 0.4 g or 0.5 g CEM liquid. The mixture was transferred to metallic cylindrical molds (n=10) with internal dimensions of 6±0.1 mm height and 4 ±0.1 mm diameter. After 4 days, the specimens were subjected to compressive strength tests using a universal testing machine. The data were analyzed by One-way ANOVA and Tukey’s tests at a significance level of 0.05. Results: Statically significant difference was found among experimental groups (P<0.05). The 0.33 WP ratio showed significantly greater CS value compared to 0.4 and 0.5 proportions (P=0.012 and P=0.000, respectively). The CS of 0.4 WP ratio was also significantly higher than that of 0.5 WP ratio (P=0.014). Conclusion: According to the results, higher WP ratios results in lower CS of the cement.Keywords: Calcium-enriched Mixture; CEM cement; Compressive Strength; Water-to-Powder Rati

Effect of Propylene Glycol on the Bond Strength of Two Endodontic Cements

Introduction: This study evaluated the effect of propylene glycol (PG) on the push-out bond strength of calcium-enriched mixture (CEM) cement compared to mineral trioxide aggregate (MTA). Methods and Materials: The lumens of two hundred 2±0.2 mm-thick root sections from human extracted teeth were prepared to achieve a diameter of 1.3 mm. The samples were then allocated into eight groups of 25 on the basis of the materials used (MTA or CEM cement) and different proportions of PG (0%, 20%, 505, and 100%). In each group, 0.4 mL of the liquid was mixed with 1 g MTA or CEM cement. After incubation, the push-out strength of the samples was measured using a universal testing machine. Data were analyzed using the two-way ANOVA followed by one-way ANOVA and student’s t-test. Results: The MTA group showed significantly higher bond strength in comparison with CEM group (P≤0.001). Also 100% and 20% PG increased the bond strength of MTA (P≤0.001). For CEM cement, 100% and 50% PG decreased the bond strength (P≤0.001). Conclusion: This in vitro study demonstrated that while PG increased the push-out bond strength of MTA, it is not recommended for mixing with CEM cement.Keywords: Bond Strength; Calcium-Enriched Mixture; Mineral Trioxide Aggregate; Propylene Glyco

The Effect of Chlorhexidine on the Push-Out Bond Strength of Calcium-Enriched Mixture Cement

Introduction: The aim of this in vitro study was to evaluate the effect of 2% chlorhexidine (CHX) on the push-out bond strength (BS) of calcium-enriched mixture (CEM) cement. Methods and Materials: Root-dentin slices from 60 single-rooted human teeth with the lumen diameter of 1.3 mm were used. The samples were randomly divided into 4 groups (n=15), and their lumens were filled with CEM cement mixed with either its specific provided liquid (groups 1 and 3) or 2% CHX (groups 2 and 4). The specimens were incubated at 37°C for 3 days (groups 1 and 2) and 21 days (groups 3 and 4). The push-out BS were measured using a universal testing machine. The slices were examined under a light microscope at 40× magnification to determine the nature of bond failure. The data were analyzed using the two-way ANOVA. For subgroup analysis the student t-test was applied. The level of significance was set at 0.05. Results: After three days, there was no significant difference between groups 1 and 2 (P=0.892). In the 21-day specimens the BS in group 3 (CEM) was significantly greater than group 4 (CEM+CHX) (P=0.009). There was no significant difference in BS between 3 and 21-day samples in groups 2 and 4 (CEM+CHX) (P=0.44). However, the mean BS after 21 days was significantly greater compared to 3-day samples in groups 1 and 3 (P=0.015). The bond failure in all groups was predominantly of cohesive type. Conclusion: Mixing of CEM with 2% CHX had an adversely affected the bond strength of this cement

Effect of a New Imidazolium-based Silver Nanoparticle Irrigant on the Bond Strength of Epoxy Resin Sealer to Root Canal Dentine

Introduction: The aim of this study was to evaluate the effect of a new imidazolium-based silver nanoparticle (ImSNP) root canal irrigant on the bond strength of AH-Plus sealer to root canal dentine. Methods and Materials: Forty single-rooted extracted human teeth were used in this study. The crowns were resected and according to the irrigation solutions used during root canal preparation, the roots were divided into 5 groups (n=8): Group 1: normal saline (control group), Group 2: 2.5% Sodium Hypochlorite (NaOCl), Group 3: 2.5% NaOCl+17% ethylene diamin tetracetic acid (EDTA), Group 4: silver nanoparticles (AgNPs), Group 5: AgNPs +17% EDTA. After root canal instrumentation, the canals were filled with AH-Plus. Then, after 7 days, 2 or 3 dentine disks were obtained from the mid-root of each sample. Bond strength was measured by the push-out test. Additionally, failure patterns were classified as adhesive, cohesive and mixed. Data were statistically analyzed by one-way ANOVA and Tamhane post hoc tests. The level of significance was set at 0.05. Results: There was no statistically significant differences between groups (P>0.05). Groups 4 (AgNPs), 3 (2.5% NaOCl+17% EDTA) and 2 (2.5% NaOCl) showed statistically higher bond strength compared to group 1 (control group) (P<0.05). Also, Group 4 showed a significant difference with group 5 (AgNPs+17% EDTA) (P=0.017). The failure patterns were mainly cohesive. Conclusion: This in vitro study showed that, when used without EDTA, AgNPs improved the bond strength of AH-Plus to radicular dentine.Keywords: AH-Plus Sealer; Push-out Test; Silver Nanoparticles; Sodium Hypochlorit