Journal of Research in Dental Sciences
Year:2018 | Volume:15 | Issue:1 (55) |Papers Count:8

Background & Aim: Dental composites are of a crucial importance in restorative dentistry; however, these materials present poor mechanical properties such as low resistance against fracture and high wear rate. As a result, further studies on mechanical properties of dental composites, such as research presented this paper, is essential. The reported research was aimed to evaluate the effect of particulate filler content and size on fracture toughness of experimental dental composites.Materials & Methods: The study was done experimentally and laboratory. Initially, amorphous silica nanoparticles (ASN) with the mean particle sizes of 12 nm (ASN12) and 40 nm (ASN40) were selected. Then, silica nanoparticles were modified using silane coupling agentγ-MPS. The surface modification was also examined by FTIR and TGA tests. For this purpose, composites with different weight percentages of the filler were prepared in ten groups. Composites containing nanoparticles were evaluated in term of fracture toughness.Moreover, the distribution of the filler particles within the polymer matrix was studied using SEM and TEM respectively. The collected data were analyzed and compared by ANOVA and Tukey’s HSD tests at a significance level higher than 0.05.Results: The results of the tests indicated an increase in fracture toughness due to increased filler content. This increase has an optimum, and then the fracture toughness decreases. The results also showed that fracture toughness in composites containing 12 nm nanoparticles is better than fracture toughness in composites containing 40 nm nanoparticles. (p-0.03) Conclusions: The results showed an increase in the fracture toughness with increasing the filler content up to an optimum loading. The filler size seemed to affect fracture toughness of the composites and smaller filler sizes tend to render the material tougher.

Background and Aim: Infection control is important in dentistry. Due to importance of time efficacy and gap of information related to effect of time on disinfectant powerfulness, the aim of this study is evaluation of the effect of time on fungicidal & fungi static properties of Surfanios solution on Candida Albicans.Materials and Methods: in this experimental study, 7 Groups included positive control group (suspension without antiseptic solution) & negative control group (disinfectant without suspension) & five experimental groups were prepared..1 cc of Surfanios antiseptic solution was diluted 0.5% in the test tube and 1 cc was placed on the Candida albicans suspension. Samples were divided into 5 groups: 1, 5, 10, 15, and 20 minutes, passing through the contents of the tube (G1: 1 min, G2: 5 minutes, G3: 10 minutes, G4: 15 minutes, G5: 20 minutes) The intra-Sabooro medium was cultured linearly. This work was repeated for 7 consecutive days. The data were analyzed with Fisher’s test and Kruskal Wallis.Results: The results showed that with 1 minute exposure to disinfectants, the number of colonies decreased from 1.2×108 in the first day to 1.2×102 (p<0.00) .Conclusions: Surfanios solution is effective on the reduction and elimination of Candida albicans. Time affects the properties of this material. So that after 1 minute Showed of fungistatic properties and after 5 minutes showed fungicidal.

Background & Aim: Despite several advantages associated with prefabricated translucent glass-fiber posts, the coronal portion of these posts must be cut to allow their use in various clinical situations. The aim of this study was to investigate the effect of fiber post cutting on the bond strength of translucent and opaque fiber posts in different root sections.Materials and methods: In this study 60 sound mandibular premolar teeth were randomly devided in to 6 groups (n=10). Teeth were decoronated and endodontically treated. Post spaces were prepared.In 30 roots (groups 1, 2, 3) translucent posts while in another 30 roots (groups 4, 5, 6) opaque posts were cemented using self-adhesive resin cement. The posts were cut prior to cementation (groups 1, 4), immediately after luting (groups 2, 5) or after building up the core (groups 3, 6). Using low speed saw, 1mm-thickness coronal, middle and apical sections were obtained from each sample. Then they were subjected to push-out test. Data were collected and statistically analyzed using three-way ANOVA and Tukey post hoc test (a=0.05).Results: The push-out bond strength when fiberpost cutting was done befor cementation was significantly higher than bond strength for post cutting immediately after cementation (p=0.004). Also the mean bond strength of translucent posts was higher than opaque posts (p=0.025). But root section did not show any effect on bond strength (p=0.621).Conclusion: Post translucency increased the push-out bond strength of dual-polymerized self adhesive resin luting agents, however the bond strength was reduced when cutting was done “immediately after cementation” of posts.

Background and aim: CBCT is the method for evaluation of cross-sectional scans from jaws prior to implant placement and also it can be used for evaluation of bone density. The purpose of this study was to assess bone density values obtained by CBCT and to determine the correlation between bone density and primary stability of implants.Material and Methods: 24 patient participated in this study. Before implant placement CBCT was obtained from each patient. The bone densities of implant recipient sites were determined by CBCT with Planmeca Romexis software.Then implant placement were performed and primary stability of them were measured by Osstell ISQ. In order to assess the correlation between primary stability and CBCT gray values a linear regression analysis was used.Results: Regarding to the present study results, linear correlation is notable between implants stability and CBCT gray values resulted from CBCT. The correlation coefficient between CBCT gray values and stability was r=0.751 which was significant. (p<0.001) Conclusion: The bone quality evaluated by CBCT had a very strong correlation with primary stability of the implants. Therefore, the pre-operative evaluation of CBCT gray scales can allow clinicians to predict implant stability before placement.

Background & Aim: The popularity of dairy drinks such as Yoghurt and kefir in world and especially in Iran has led to their daily consumption. Since the type of consumable foods could effect on erosion, this research was done to compare the effect of Kefir, Yoghurt and Soy milk on permanent enamel microhardness.Materials & Methods: In this in-vitro study 30 extracted permanent teeth with no erosion and caries was chosen. Enamel blocks were made and then divided into three groups of ten. Then Vickers microhardness of each group measured before soaking the samples in the drinks. After samples soaking in its proper drinks (Kefir, Yoghurt and Soy milk) the microhardness of each group measured again.Analysis of variance used for comparing the microhardness of each group and after analysis of variance, tukey HSD was used and significant level was considered as 0.05.Results: Evaluation was made on 30 samples on 3 groups of 10 members. Difference of microhardness was -4.98±8.31 for soy milk and -19.35±13.38 for yoghurt drink and -33.54±19.54 for kefir. (p<0.001) Conclusions: Based of the findings of this study, the maximum decrease of microhardness was related to kefir and the minimum was related to soy milk.

Background & Aim: Prevalence of musculoskeletal pain among dentists due to incorrect long-term physical conditions is more than public community. Ergonomics and stress are among the causes of these pain. Due to lack of any report in Zanjan city this study aimed to determine prevalence of musculoskeletal pain among zanjan dentists, ergonomic factors, job related stress and other related factors.Methods and Materials: This descriptive study, was done on 131 dentists of Zanjan. A questionnaire was designed based on standard Nordic and Job Stress Dimension questionnaire with the aid of a psychologist and physiotherapist. The questionnaire was distributed among dentists. From 131 dentists, 11 were excluded because they didn’t meet the criteria. Prevalence of musculoskeletal pain, affected area, stress and other factor was statistically analyzed with the aid of chi-square test.Results: Among 120 dentists who met the criteria, 60.8 % was men and 30.2% was women with mean age of 37.1. Prevalence of the pain in at least one site was 67.5%with most prevalent site was shoulder 30.8%, lumbar region 24.2% and neck 20.8 %. Reported stress was moderate in 90.7% cases and 9.3 percent of dentists reported mild stress. There is no significant relationship between age, sex, work period, work hours during week, stress, arm position, application of mirror and prevalence of pain. (p<0.2). Concusion: It seems that the prevalence of musculoskeletal pain among zanjan dentists is high. This pain didn’t have any relation with individual characteristics and dentist condition.

Background & Aim: Complex and sometimes unknown factors affect the quality and quantity of learning students and their academic achievement. One of the factors that due to the severity of their impact on academic achievement were considered by most experts is motivation which sometimes is studied as an independent agent. Therefore, because of importance of the issue, this paper try to assess first to third year students motivation in dental school, Islamic Azad University of Tehran and its relationship with the relevant factors in the year 1395.Materials & Methods: This descriptive study was used to measure academic motivation from the academic motivation scale, which is a standardized, and self-assessment scale and measures three dimensions of exterior, internal, and impersonal motivation. After the presentation, the questionnaires were distributed among the students. According to the rank obtained in the range (196-28), the students motivation divided in the three groups, (high motivation=130 and more), moderate (65-130) and low motivation (<65) and then relevant factors were determined by Regression analysis.Results: The study population was 217 of which 31.3% were males and 68.7% females. The age of the students was 21.1±3.6 years.64.5% had high motivation. There was a significant relationship between gender and education motivation level (P<0.001) and students with good economics, 2.7 times higher than those with moderate economics also had higher educational motivation (p=0.96).Conclusion: It seems that the degree of motivation in dentistry students is relatively high, which has a positive relationship with gender and economic conditions.