فهرست مطالب

Dental Biomaterials - Volume:3 Issue: 4, 2016
  • Volume:3 Issue: 4, 2016
  • تاریخ انتشار: 1395/09/12
  • تعداد عناوین: 6
|
  • Sayed, Mostafa Mousavinasab, Mohammad Atai, Negar Salehi, Arman Salehi Page 299
    Statement of Problem: The degree of conversion depends on the material composition, light source properties, distance from light source, light intensity, curing time, and other factors such as shade and translucency.
    Objectives
    In the present study, we evaluated the effects of different light- curing modes and shades of methacrylate and silorane-based resin composites on the degree of conversion of resin composites (DC).
    Materials And Methods
    The methacrylate-based (Filtek Z250, 3M, ESPE) and low-shrinkage silorane-based (Filtek P90, 3M, ESPE) resin composites were used in three groups as follows: group 1-Filtek Z250 (shade A3), group 2-Filtek Z250 (shade B2), and group 3-Filtek P90 (shade A3). We used a light-emitting diode (LED) curing unit for photopolymerization. 10 samples were prepared in each group to evaluate the degree of conversion; 5 samples were cured using soft-start curing mode, and the other 5 were cured using standard curing mode. The DC of the resin composites was measured using Fourier Transform Infrared Spectroscopy (FTIR). The data were analyzed using Kruskal Wallis and one- way ANOVA statistical tests.
    Results
    The degree of conversion of silorane-based resin composite was 70 - 75.8% and that of methacrylate-based resin composites was 60.2 - 68.2% (p = 0.009). The degree of conversion of the composite with brighter colour (B2) was statistically more than the darker composite (A3). Higher degree of conversion was achieved applying the standard curing mode.
    Conclusions
    The results of the study showed that the colour and type of the resin composite and also the curing mode influence the degree of conversion of resin composites.
    Keywords: Degree of Conversion, Methacrylate, Based Resin Composites, Silorane, Based Resin Composites, Soft, Start Curing
  • Maryam Bakhtiar, Naser Azadi, Ali Golkari Page 306
    Statement of Problem: Pit and fissure sealant therapy has been approved as an effective measure in the prevention of occlusal dental caries. Resin based ma- terials are the most common materials used worldwide. A variety of resin based fissure sealants are produced and used. Most of them have been presented with ideal results in research environment. However, their effectiveness in the real life, especially in a mass application program such as Iran’s oral health reform plan is not clear.
    Objectives
    To evaluate the longevity of different fissure sealant applied in Iran’s oral health reform plan in Fars Province (south of Iran) after one year.
    Materials And Methods
    Seven counties were selected. One hundred 6- to 8-year-old school children who had undergone fissure sealant therapy in spring 2015 were randomly selected from each county. Their first molars were exam- ined to evaluate the status of the fissure sealants which were applied one year ago. Data on the type/brand of fissure sealant materials, type and experience of clinicians who applied them, existence of a chair-side assistant, and whether the children were caries-free at the time of fissure sealant application were collected from the existing reports.
    Results
    Data of 1974 teeth from 598 children were used for the final analysis. The effects of type/brand of the material was significant on the final results and remained significant (p
    Conclusions
    Many factors affect the success rate of a fissure sealant therapy program. The type/brand of the material remained significantly related to the success rate of the fissure sealant even after adjustments for other influencing factors. In this study, ClinproTM Sealant (3M/ESPE, USA) showed better longevity after one year of application.
    Keywords: Pit, Fissure Sealants, Preventive Dentistry, Molar
  • Maryam Sharifi, Somayeh Khoramian Tusi Page 315
    Statement of Problem: The bond strength between restorative material and tooth structure is so important for conduction of durable restoration. Considering the recent attention to low shrinkage composite resins, evaluation of micro tensile bond strength of these materials would be valuable.
    Objectives
    To compare the microtensile bond strength of silorane composite resin (Filtek P90) with the conventional methacrylate composite (Filtek Z250) with and without applying acid etch before application of bonding system.
    Materials And Methods
    In this experimental study, 24 intact primary canines were used. After the dentin was exposed, the teeth were randomly divided into four groups as follows: the first group (silorane bond system composite Filtek P90); the second group (etch silorane bond system composite Filtek P90); the third group (Single bond composite Filtek Z250); and the fourth group (etch Single bond composite Filtek Z250). The teeth were cut on the longitudinal axis and the interface between the composite and dentin were grinded buccolingually and mesiodistally. The samples were subjected to a microtensile force until breakage. The obtained values were recorded in MPa; data were analyzed using One-way ANOVA and Tamhane’s T2 statistical tests.
    Results
    The average microtensile bond strength in all groups had a statistically significant difference with each other (all p
    Conclusions
    As the second group (etch silorane bond system composite Filtek P90) exhibited higher microtensile bond strength, it may prove that using composite Filtek P90 is preferable to be used in primary dentin in comparison with composite Filtek Z250, and using etch silorane bond system is more advantageous than single bond system.
    Keywords: Microtensile Bond Strength, Silorane Adhesive System, Methacrylate Composite, Self, etch Primer
  • Samira Hajimaghsoodi, Hengameh Zandi, Mohsen Bahrami, Roqayeh Hakimian Page 322
    Statement of Problem: It is necessary to use irrigation solutions during cleaning and shaping of root canals to efficiently reduce the number of micro organisms. Sodium hypochlorite is used as an effective antibacterial endodontic irrigants. However, the extract of pennyroyal plant has also shown anti-bacterial characteristics comparable with antibacterial drugs.
    Objectives
    To compare the anti-bacterial effect of spearmint extract on Entero- coccus faecalis bacteria with that of sodium hypochlorite 5.25%.
    Materials And Methods
    In this experimental study, Muller Hinton medium, including 5% sheep blood was prepared. The two solutions used including sodium hypochlorite 5.25% and spearmint extracts were put adjacent to Enterococcus faecalis bacteria after preparing. Two groups, each containing 10 samples, with the total of 20 samples were used. The disks, including each solution were placed 2 cm apart on a plate containing Muller Hinton medium and the bacteria. The plate was subsequently incubated at 37°C for 48 hours. After incubation, the mean diameter of the halo around each disk, which represents the lack of bacterial growth, was measured and compared using a ruler. Penicillin disk was used for positive control and a sterile blank disk containing physiologic serum was utilized as the negative control. This process was repeated 10 times for each solution. Data were analyzed in SPSS 17 statistical software using t-test.
    Results
    The results showed that the mean diameter of halo in the spearmint extract group was zero and in the sodium hypochlorite group it was 23.7 ± 1.49 mm. There was a significant difference between the mean diameter of the lack of growth halo of the spearmint extract and that of hypochlorite sodium 5.25% on Enterococcus faecalis bacteria (p ≤ 0.001).
    Conclusions
    Considering the limitations of an experimental study, it seems that spearmint extract does not have any anti-bacterial effect against Enterococcus faecalis bacteria, in contrast to hypochlorite sodium 5.25%.
    Keywords: Hypochlorite Sodium, Spearmint Extract, Root Canal Irrigation, Enterococcus faecalis
  • Marzieh Monfared, Mohammad Ebrahim Bahrololoom Page 327
    Statement of Problem: Dental resin composites are becoming prevalent in restorative dentistry and have almost replaced amalgam nowadays. Consequently, their mechanical properties and durability are critical.
    Objectives
    The aim of this study was to produce Pyrex glass nano-particles by wet milling process and use them as reinforcement in dental resins for anterior restorations and then examination of fractographic properties of these composites.
    Materials And Methods
    The glass nano-particles were achieved via wet milling. The surface of the particles was modified with 3-(Trimethoxysilyl) propyl methacrylate (γ-MPTMS) silane in order to improve their surface. Fourier transform infra-red (FTIR) analysis showed that the silane groups provided double bonds to the surface of the particles and prevented agglomeration. Then, the composite resins were made with different weight percentages of Pyrex glass. The mechanical properties of samples flexural test were evaluated. The required energy for fracture of the specimens was achieved via this test. The fracture surfaces of the samples were analyzed using a scanning electron micro- scope (SEM) in order to explain the mechanisms of fracture.
    Results
    The results and analysis showed that increasing the glass nano-particles mass fraction had a great effect on mechanical properties of the composites due to the mechanisms of crack propagation and crack deflection as well as preventing void formation. The effective energy dissipation mechanisms such as crack pinning and deflection, was observed in SEM micrographs.
    Conclusions
    Void formation in the low filler content composite is one of the mechanisms to decrease the energy required for fracture of these composites and eventually weaken them.
    Keywords: Dental Composite, Glass Nanoparticles, Mechanical Properties, Fractography, Biomaterials
  • Sahar Mousavi, Shima Narimani, Somayeh Hekmatfar, Karim Jafari Page 335
    Statement of Problem: Acrylic teeth of dentures are prone to discoloration due to frequent exposure to different colouring solutions in the oral environment. Thus, in order to maintain their aesthetic appearance, they must possess high colour stability while exposed to colorant solutions.
    Objectives
    To compare the colour stability of three different brands of acrylic teeth following immersion in coffee, tea and cola.
    Materials And Methods
    This in vitro experimental study was conducted on 90 acrylic teeth in three groups (n = 30) of Ivoclar (Italy), PolyDent (Slovenia) and Apple (Iran). The teeth were immersed in coffee, cola and tea for one, three and six weeks (the teeth were not in contact with each other). Colour parameters were assessed before and after immersion using a spectrophotometer, and overall change in colour parameters was calculated. The overall colour change (ΔE) of the three groups at different time points was analyzed using one-way ANOVA. Pairwise comparisons were performed using Tukey’s test.
    Results
    Coffee caused the greatest colour change in Apple acrylic teeth after six weeks (mean ΔE of 4.6 for coffee and 3.4 for tea and cola). Tea caused an almost equal colour change in the three groups. The greatest colour change in the Ivoclar teeth occurred in cola after six weeks (mean ΔE of 3.3, 3.4 and 2.8 for cola, tea and coffee, respectively). The greatest ΔE occurred at six weeks and was the highest in Apple, followed by PolyDent and then Ivoclar teeth in coffee (mean ΔE of 4.6, 3.4 and 3.3, respectively p
    Conclusions
    Despite the significant colour change in the three groups, ΔE in Ivoclar group was within the clinically acceptable range of ≤ 3.3. A slight colour change was expected regarding the Apple and PolyDent acrylic teeth clinically.
    Keywords: Colour Stability, Acrylic Teeth, Spectrophotometer, Colouring Solutions