Effects of incorporating zinc oxide and graphene oxide nanoparticles on abrasion, translucency, and microhardness of flowable composite resin: In vitro

Background

Zinc oxide (ZnO) and graphene oxide (GO) nanoparticles (NPs) have antimicrobial properties. The present study was undertaken to evaluate the effects of incorporating these NPs and their chemical and physical blends on abrasion, translucency, and microhardness of flowable composite resin.

Materials and Methods

In the present in vitro study, flowable composite resin samples (Grandio Flow, VOCO, Germany) were evaluated in 5 groups and the sample size was 10 for each group of each experiment (n = 10) as follows: Group 1, without NPs; Group 2, with ZnO NPs; Group 3, with GO NPs; Group 4, containing a physical mixture of GO and ZnO; and Group 5, containing a chemical mixture of GO and ZnO NPs. In all the groups, 1 wt% of the NPs were incorporate into flowable composite resin. Abrasion, translucency, and microhardness of the samples were evaluated. Data were analyzed with analysis of variance, followed by post hoc Tukey's tests at the level of significance of P < 0.05.

Results

In Groups 2, 4, and 5 (all the groups containing ZnO), a significant decrease in abrasion and microhardness of flowable composite resin was observed compared to the control group. Incorporation of NPs in all the groups resulted in a significant decrease in translucency compared to the control group.

Conclusion

Incorporation of NPs into flowable composite resin resulted in a decrease in translucency. The microhardness was reduced in groups containing ZnO, but the abrasion was also reduced in these groups. The incorporation of GO did not significantly alter the abrasion and microhardness of the composite resin.

Frequency of caries in triangular-shaped radiolucencies on periapical radiographs of maxillary deciduous second molars

Background

Dentists might face various artifacts (such as triangular-shaped radiolucencies [TSRs]) during the assessment of radiographs and should be able to differentiate them from caries to avoid unnecessary treatments.

Materials and Methods

In this cross-sectional study, 109 maxillary second primary molars were evaluated in cooperative children aged 4-9 years, who had distal caries in their maxillary first primary molars. First, TSRs were recorded on periapical radiographs of each maxillary second primary molar's proximal surface. Then, after excavating distal caries in the adjacent teeth "D," a pedodontist examined the mesial surfaces of teeth "E." Chi-square test was used to compare the distribution of caries in different variables, and the kappa coefficient was applied to evaluate clinical and radiographic agreements. A P < 0.05 was considered statistically significant.

Results

Forty-four cases were found to be carious both clinically and radiographically, and 54 cases were noncarious by both methods, while for 11 cases, the diagnosis was controversial. No statistically significant difference was found between radiographic and clinical caries detection methods in children whose periapical radiographs contained TSRs, and most of the subjects had similar diagnoses. Value of caries detection sensitivity, specificity, positive predictive value, and negative predictive value in TSRs was 88%, 92%, 90%, and 90%, respectively.

Conclusion

Considering high radiographic sensitivity for caries detection in TSRs, clinicians should be more cautious about them being carious or not, and both radiographic and clinical examinations are necessary. Further, to avoid misinterpretation in radiographs, additional education is necessary for young dentists.

Effect of Popping Chocolate and Candy on Enamel Microhardness of Primary and Permanent Teeth

Aims and Objectives

Dental erosion is a common disease in children. Food diets, due to high amounts of juice, soft drinks, chewing gum, and acidic chocolate, are one of the most important risk factors in erosive processes among children. The aim of this study was to evaluate the effect of candy and chocolate on the microhardness of tooth enamel.

Materials and Methods

Two types of popping candy and one type of popping chocolate were used in this study. Thirty-three healthy permanent premolar teeth and 33 primary incisor teeth (A or B) were selected. Five grams of each popping chocolate or candy was dissolved with 2 ml of artificial saliva. Subsequently, their pH and titrable acidity (TA) as well as microhardness and surface roughness of enamel were examined in the laboratory. Data were analyzed and evaluated Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY through independent t-test, paired t-test, Tukey test, and ANOVA.

Results

The results of this study showed that only the pH of the candies was below the critical pH of the enamel (5.5) and their TA was B = 0.20 and C = 0.21. The most significant effect on the enamel microhardness of the permanent and primary teeth was by the following types of candy: orange flavor (C), strawberry flavor (B), and chocolate (A), respectively. This difference was significant (P < 0.001) and the surface roughness increased after exposure.

Conclusions

This study showed that popping chocolate and candy reduces microhardness of enamel.

Effect of diode laser irradiation on compressive strength of dental amalgam

Introduction

One of the biggest disadvantages of dental amalgam is that gaining its ultimate strength is a slow process. The use of a rapid-setting amalgam with high early compressive strength could be a better option in preventing early fractures in pediatric dentistry. The aim of this study was to determine the effect of diode laser irradiation on compressive strength of dental amalgam.

Methods

A case-control study was performed on 180 amalgam samples made at the Tehran Dental Material Research Center in 2014. Fifteen and thirty minute compressive strength of regular setting and fast setting amalgams were measured as control. In case groups, the samples were irradiated by 810nm diode laser with power of 1 and 2 watt and in pulsed and continuous mode, and compressive strength was measured after 15 and 30 minutes. Statistical analysis was performed with SPSS 18 using one and two way ANOVA and Scheffe multiple comparisons test and p<0.05 was considered significant.

Results

Numerous kinds of laser irradiation led to a significant increase in compressive strength compared to regular setting control groups. Fifteen minutes-compressive strength of regular-setting amalgam irradiated by 2 watt laser was significantly more than fast-setting control group (p<0.05).

Conclusion

Irradiation by 810nm diode laser can significantly increase the compressive strength of dental amalgam especially in the first 15 minutes.

Evaluating the Microshear Bond Strength and Microleakage of Flowable Composites Containing Zinc Oxide Nano-particles

INTRODUCTION

Preventive resin restorations (PRR) are the conservative choice for the most common carious lesions in children. Thus, new age flowable resin composites with higher filler content are readily used. The aim of this study was to evaluate the microshear bond strength and microleakage of two flowable resin composites containing different percentages of nano zinc oxide (NZnO) particles, which have proven to have antimicrobial properties.

METHODS

This experimental in-vitro study was carried out in the Dental Material Research Center of Babol University of Medical Sciences in 2015. One nanohybrid and one nanofill flowable resin composite were chosen and modified with the incorporation of 1% and 3% Wt NZnO particles. Six groups (n=10, 0%, 1%, and 3%) of resin composite sticks on dental enamel (2×2mm) were prepared to be placed in the microtensile tester. The microshear bond strength magnitude (MPa) was recorded at the point of failure. A class I box (3×0.8×1 mm) was prepared on 60 premolars and filled using the resin composites (6 groups, n=10). The specimens were immersed in a 5% basic fuschin solution and sectioned bucco-lingually to view the microleakage using a stereomicroscope. One-way ANOVA and Tukey tests for microshear and Wilcoxon and Kruskal-Wallis tests for microleakage were used to analyze the data in the IBM SPSS Statistics version 22 software.

RESULTS

The bond strength of the 3% clearfill group significantly decreased while no significant change occurred in the bond strength in other groups. The Z-350 group had significantly lower microleakage as nanoparticles increased. No significant difference was observed in the clearfill group.

CONCLUSION

Up to 3% Wt incorporation of NZnO particles will not diversely alter the bond strength, but it will be beneficial in providing antimicrobial effects with lower microleakage rates.

Non-cirrhotic portal vein thrombosis, an uncommon cause of portal hypertension - a case report

Most cases of portal hypertension follow chronic liver disease (cirrhosis) while non cirrhotic causes are occasionally seen. A case of portal hypertension secondary to non-cirrhotic portal vein thrombosis is reported. The patient was managed at the Aminu Kano Teaching Hospital Kano, Nigeria in the year 2006. She presented with recurrent massive upper gastrointestinal bleeding and was resuscitated, followed by clinical, radiological and endoscopic evaluation. She had massive splenomegaly and grade four oesophageal varices with evidence of recent bleed. There were, however, no other stigmata of chronic liver disease or portal hypertension. Abdominal computed tomography scan confirmed portal vein thrombosis. Splenectomy and ligation of short gastric veins was performed and the patient has not had any repeat episode of haematemesis or malaena six months post surgery.

Effect of sowing depth on performance of Quercus castaneifolia seedling at different levels of canopy cover

Due to failure of oak (Quercus castaneifolia C.A. Meyer) natural regeneration, investigation on the best acorn sowing depth of this species under different levels of canopy cover is an important consideration in the Caspian forests, north of Iran. For this purpose, a study site with north-facing slope, clay-loam soil and 260-280 m a.s.l. was chosen in a mixed oak forest. The experiment was conducted as a Complete Randomized Split Plot Design (CRSPD) and the measurements made in one growing season in nine fenced circular 1000 m2 plots with three canopy densities (25, 50 and 75%) at three soil depths (5, 10 and 15 cm). The results revealed that under all canopy densities the maximum seedling emergence occurred at 5 cm depth. The highest emergence rate was appeared in June and the lowest in October. Neither canopy density nor sowing depth did prominently reduce seedling establishment, but a high quotient of mortality likely could be attributed to rodent populations, particularly Hystrix indica. Under all canopies, ground line diameter decreased with increasing sowing depth, the biggest being at 5 cm depth. Neither canopy density nor sowing depth influenced the seedling height. It can be concluded that the best performance of Q. castaneifolia seedling occurs at 5 cm sowing depth and 25% canopy cover.

Effect of light and humus on survival and height growth of ash (Fraxinus excelsior L.) seedlings

In  1997, 300 3-month-old ash (Fraxinus excelsior L.) seedlings were removed out of the three    different humus types (100 seedlings from each humus type) in the  experimental forest of    Aelmoeseneie (University of Ghent) with a closed canopy, in north of  Belgium. Humus types were    described as active mull with pH of 5.3-6.5, acid mull with pH of 4.4-5.2  and moder mull with pH of    3.8-4.3. Seedlings were transplanted in plastic pots, filled by the  original soil, and placed under five    levels of light intensity (2.5, 10, 18,28 and 92%), inside and outside the  forest. Only with 92% light    intensity seedlings were watered as necessary to avoid any appreciable  water deficit.    The results after 1 growing season revealed that seedlings attained a very  high survival rate    (95.3%). Survival was the highest when seedlings grew under semi-closed  canopy (10, 18, and    28%) and also outside the forest at the 92% light intensity, compared with  those under closed    canopy (2.5%). It also confirmed that ash seedlings are shade tolerant, but  with little growth.    Height growth indicated an increasing growth response to nutrient  availability with increasing light    intensity. In fact, minimum height growth was observed in lower light  intensities (2.5 and 10%) and    the maximum value in higher light intensities (28 and 92%). Height growth  of ash seedlings    increased at humus types of active and acid mull, compared with moder  mull.    At the end of the first growing season, lack of differences in survival  rate and height growth,    produced under 18, 28 and 92% light intensity, revealed that training the  seedlings under semiclosed    canopy (18 and 26%) has a preference to those under relatively full  daylight (92%)    associated with watering. Therefore, the first year observations showed  that ash seedlings, either in    view of stem quality and growth or with regard to the facilities of  maintenance, are preferable to be    trained under intermediate light intensities (preferably 28%), at the high  nutritional humus (active    and acid mull).