مجله تحقیق در علوم دندانپزشکی
سال هفدهم شماره 4 (پیاپی 66، زمستان 1399)

On December 2019, a large number of pneumonia cases with unknown etiology were reported in Wuhan, China. In specimens taken from the throat with a swab, a new virus was founded, which was called COVID-19 by WHO. Due to the small number of studies, we decided to investigate the role of the oral cavity in this disease.

Due to the composite structure of the jaw bone, gelatin and beta-calcium phosphate (b-TCP) biomaterials have been used repeatedly in bone tissue engineering. Despite the desirable properties of scaffolds made, their application has been limited due to their poor mechanical properties and high degradability. The aim of this study was to investigate the effect of clinoptilolite biomaterial with unique mechanical properties such as remarkable mechanical properties, low degradation rate and highly favorable biocompatibility properties in gelatin and b-TCP scaffolds.

Preparation of porous scaffold as a template was made leading to freeze drying method using weight percent of 50 for gelatin, 25 b-TCP and 25 Clinoptilolite. SEM analysis and image j software was used in order to evaluation of scaffold surface and finding of porosity frequency. Finally, compressive strength of scaffold was evaluated. 

In clinoptilolite / b-TCP / Gelatin scaffolds, porosity up to 250 nanometers was recorded which was the best for angiogenesis. In addition to gelatin, clinoptilolite also had a positive effect on porosity. Using compressive strength analysis, increasing of Youngchr('39')s modulus was also observed from 100 to 166 mega Pascal by that Clinoptilolite is the most effective agent in modifying this modulus.

Considering the results, clinoptilolite that in addition to improving and enhancing the mechanical properties of composite scaffolds, had a significant effect on the increase in the size and porosity of jaw bone tissue engineering scaffolds. According to the obtained characteristics it can be said that the sample presented is in accordance with the properties of extracellular scaffold (ECM) of jaw bone tissue and would be a suitable choice in tissue engineering of this type of bone.

Candida-albicans is a normal floor and one of the opportunistic pathogens in the oral cavity. There are various treatments for this infection, including nystatin. Considering the high potential of plant extracts, including green tea, in the field of antimicrobial activity, this study was designed to investigate the effect of green tea extract on Candida albicans species.

Initially, the aqueous-alcoholic extract of green tea at different concentrations was prepared. Broth micro dilution method was used to determine the MIC. From the contents of different wells containing less concentrations of green tea and no candidate growth was observed, 10 micro liter of dextrose agar substrate was removed and the lowest amount of green tea, which showed less growth was considered as minimum fungicidal concentration (MFC). Also, 50% and 100% green tea extracts of the discs were prepared to determine the size of the growth medium in the culture medium. Data analyzed using STATA software 14. 

MIC and MFC for green tea extract start at a concentration of 256 mg / ml. It was also found that the inhibition zone was equal to zero in both concentrations of 50% and 100% for the green tea extract.

It seems, green tea has antifungal effect in very high concentration rather than oral usage and also, as mouthwash and just with direct contact.

Biocompatibility in some respects depends on the corrosion behavior of dental alloys. The purpose of this study was to investigate the effect of surface passivation of a cobalt chromium alloy on corrosion behavior.

In this experimental study, 20 samples of Flexicast dental alloy were prepared according to ADA97 standard and after casting, the samples were polished to the mirror surface. Electrolytic passivation was employed by immersion of one first series of samples in Na2SO4 solution for 24 hours at room temperature. The second series of specimens was not passivated. Surface morphology and chemical composition before and after passivation studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to investigate the corrosion behavior in saline solution. Corrosion test was conducted for 4 weeks and surface of specimens were monitored each week. The chemical composition results were analyzed by Kruskal-Wallis and Mann-Whitney tests using SPSS17 software.

The passivated specimens exhibited higher corrosion resistance while pitting corrosion was detected in all specimens. Kruskal-Wallis test showed a significant difference between the two groups of passivated and non-passivated samples. The Mann-Whitney test showed that the cobalt, chromium and oxygen ions were significantly different between the two groups (P <.0.05).

The rate of corrosion and formation of pits were significantly reduced by surface passivation.

Considering the widespread use of composite restorations and the provision of nanocomposites on one side and the common use of mouthwashes, there are concerns about the microhardness of composites and their known complications following mouthwashes. So, the present study was aimed to compare the effect of two mouthwash with alcohol and without alcohol on microhardness changes of two types of composite resins.

Experimental design was performed. In total, 32 samples of composite specimens of 3 mm in diameter and 3 mm thick were prepared from nano composites Z350 (3M ESPE, USA) and Z250 (3M ESPE, USA). The primary hardness was measured by the Matsuzawa japan machine (Vickers hardness tester), and then the specimens were randomly divided into two subgroups. (n = 8) were then inserted into 20 ml of alcohol-free and non-alcoholic listerine mouthwash for 24 hours, then removed the specimens and the secondary microhardness was measured by the apparatus.  Microhardness changes in each group were performed by paired Ttest test.

The highest microhardness changes in the Z250 micro-hybrid composite in the mouth of the listerin containing alcohol was 11.4 ± 3.4 and the lowest was related to the Z350 nano-fiber composite in the listerine-free zinc mucous membrane at 0.4 ± 4.2. Mouthwashes containing alcohol significantly reduced microhardness in both composites (P <0.001).

It seems that mouthwash containing alcohol significantly reduces the microhardness of composites. In terms of microstructure, there is no significant difference between the Z350 nanofill composite compared to the Z250 micro hybrid composite when it is placed in the mouthpieces but Z350 nanofill composite showed better functions.

Geographic tongue is a common inflammatory disorder of the tongue whose etiology is unknown. In this study, salivary levels of interferon-gamma were measured in persons with geographic tongue.

In this case-control study, 30 persons with geographic tongue and 30 healthy individuals who had the conditions to enter the study were evaluated among the patients referred to Zahedan Dental Clinic. The control group was matched for age and sex. In both groups, unstimulated saliva was collected by Spitting at 9 am to 11 am. Salivary interferon Gamma samples were measured using Interferon Gamma Diagnostic Kit (HIFN) and ELISA Reader. According to the Kolmogorov-Smirnov test, the data distribution was normal (P = 0.198), data analyzed by statistical software 22 SPSS and using t-test.

The mean age in the group with geographic tongue was 31.3 ±6.2 years and in the control group the mean age was 30.96± 6.46 years. The mean saliva interferon gamma was not significantly different between the persons with geographic tongue (25.73±12.09 pg/ml) and the control (21.52±11.91 pg/ml) group (p=0.18).

Saliva interferon gamma was higher in geographic tongue persons than healthy controls, but this difference was not statistically significant.
Key Words:

Sella turcica is one of the most important orthodontic landmarks in a key point in lateral cephalometric analysis of the patients who need orthodontic treatment. The aim of this research was to investigate the relationship the dimensions of Sella Turcica with the vertical skeletal pattern of the face on cone beam computed tomography images in an Iranian population.

In this descriptive analytical research, the samples were evaluated in a total of all available CBCTs of the patients referred to Tabriz Dentistry Faculty. In selected CBCT (in sagittal sections), the length and height of Sella Turcica was measured. By evaluating the angle between the two lines Go-Me and S-N as the well as the S-Go/N-Me ratio, the short, long or normal facial skeleton was examined. The data obtained from CBCT were entered in the related software and the images were reviewed by two oral and maxillofacial radiologists and the agreement between two observer results was measured by Kappa coefficient. data were analyzed using Kruskal-Wallis statistical test and p<0.05 was considered.

For three types of vertical face growth (normal, long and short) the length and height of Sella Turcica were similar. For all types of vertical facial growth, the height and length of Sella Turcica were similar in men and women and had no significant relationship with age.

Based on the results of current study, it seems there are no relationship between dimensions of Sella Turcica and vertical skeletal growth pattern.

This study was aimed to compare the instrumentation time and the amount of debris extruded apically  during root canal preparation using hand files ,Mtwo rotary system and endodontic handpiece  in primary molar teeth.

Method & Material : 

In this experimental study, sixty roots of  primary molars of human teeth were assigned to three groups (for each group, n=20). The canals were then instrumented with the following instrument systems : Mtwo rotary , endolift and hand files. Debries during instrumentation was collected into pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70°C for 5days. The weight of the dry extruded debris was established by pre-instrumentation and post instrumentation weight of the Eppendorf tubes for each group. Instrumentation time was also recorded. The data of debry extrusion and instrumentation time were respectively analyzed using one – way analysis of variance (ANOVA) and Kruskal-Wallis tests.

Hand files were associated with more apically extruded debris than the Mtwo rotary and endodontic handpiece (P<0.05 ).Intergroup comparison of the instrumentation time didn’t show a statistically  difference  between the three groups (P>0.05)          

It seems, Mtwo rotary and endodontic hand piece, produced less debries v.s to hand instrumentation of primary molar canals. All instruments were associated with apical extrusion of debris and in terms of the instrumentation time, no method was faster than any other ones.
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Coronaviruses generally cause mild to moderate respiratory and gastrointestinal infections in humans and animals, but the new coronavirus has created one of the biggest problems for human health on Earth. Prior to December 2019, Corona virus viruses have seriously attacked human populations twice in the form of MERS and SARS diseases. Coronavirus has now caused millions of people to become infected with the new mutation, which is so much more severe than before that many health-related approaches have been affected. One of the most important approaches is the health needs of oral health and the health of dentists.

In order to extract of data, the researcher overviewed issues from PubMed، Medline, Scopus, Nature and Google Scholar from 2005-2020.and 61 articles were chosen, the maximum were published in 2020 parallel with virus world contamination.

One of the important findings in new article is know the manner of virus and hygienic protocols against virus contamination. The virus cross-contamination, screening the patients and disinfection in dental clinics and mineral supplement usage for increasing the immunity of persons and attention to health protocols are summarized and categorized from studies as well.

Studies have shown that new effective drugs and vaccines against new introduced viral diseases must be produced by scientist. More important, more rigid rules must be performed for traffic in crowded places. Dentists must pay more attention to personal and environmental health and hygienic protocols