Journal of Dental School, Shahid Beheshti University of Medical Sciences

Objective: Being able to cause disease in human, herpes simplex viruses (HSVs) clinically demonstrate themselves as intra-oral, extra-oral or recurrent lesions. The existing acyclovir has the selective anti-herpetic drug to control HSV infections. Due to emerged resistance to this drug and limitations of using it in especial situations, there is a need for alternative treatments such as available mouthwashes. This study aimed to compare two mouthwashes (Irsha and Chlorhexidine) with Acyclovir on HSV-1 in vitro.

Methods: In this experimental research, we used MTT (Thiazolyl Blue Tetrazolium Bromide) colorimetric test to determine the cytotoxicity level of three solutions consecutively, antiseptic and nonalcoholic Irsha mouth wash (blue-colored), chlorhexidine 0.2% mouthwash, and acyclovir and absorbed wavelengths were recorded by Eliza Reader. After infecting the cells with different dilutions of HSV-1 in different concentrations of Irsha and chlorhexidine mouthwashes, we analyzed their antiherpetic effects on Vero cells. By using suitable statistical tests in version 15 of SPSS the results  were then analyzed.

Results: The results showed that in the concentrations of 0.38% for Irsha and 0.003% for chlorhexidine these mouthwashes kill 50% of Vero cells (CC50). After determining CC50, we  detected the antiviral effects of Irsha and chlorhexidine mouthwashes and acyclovir solutions. We observed a significant difference between 0.5% concentration of Irsha mouthwash and other concentrations of it.   The least logarithm of virus titration was observed in 0.002% concentration of

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chlorhexidine  mouthwash.  Both  tested  acyclovir  concentrations  (1250  µgr  Mililiter   and   2500

µg/mL         Mililiter

µgr

/                 ) had a similar effect on decreasing virus titre

Conclusion: According to our results, anti-herpetic effect of Irsha is less than chlorhexidine and anti-herpetic effect of Acyclovir and Chlorhexidine is stronger than Irsha.

Objective: Etching of enamel and dentin is an important step in restoration of teeth with composite resin ensuring the retention of restoration and decreasing microleakage. This in vitro study sought to compare the effects of Kimiya and Etch-Rite acid etchants on the microleakage of composite restorations.

Methods: This experimental study was conducted on 30 sound human molar teeth. Class V cavities were prepared on the buccal surface of teeth and the teeth were randomly divided into 2 groups of

15. Iranian acid etchant (Kimiya, Iran) was used in group 1 and Etch-Rite (Pulpdent, Watertown, MA, USA) in group 2. The teeth were restored with Valux Plus (3M, ESPE, St. Paul, MN, USA) composite resin and polished by disc. The canal apices were sealed with sticky wax and the entire tooth surface was coated with 2 layers of nail varnish except for 1 mm around the restoration margins. Specimens were immersed in 2% Fuchsin (Fuchsin Dye, Merck, Germany) for 24h and then buccolingually sectioned. Specimens were evaluated under a stereomicroscope (SF-100B, Lomo, Russia) at 40X magnification and the degree of microleakage was determined using a 0-4 scale. The degree of microleakage was statistically analyzed using Mann Whitney U test.

Results: No significant difference was found between the two groups of Kimiya and Etch-Ritein the degree of microleakage at the occlusal wall (p=0.1). The degree of microleakage at the gingival wall was not significantly different between the two groups either (p=0.68).

Conclusion: Based on the results, Kimiya Iranian acid etchant has an efficacy equal to that of Etch- rite.

Objective: Adequate knowledge about restorative materials particularly flowable composite resins with favorable physical properties like optimal microhardness and resistance to environmental factors is a big concern for many dentists. Flowable composites have several applications for fissure sealant therapy and preventive resin restorations (PRR); which are common treatments in pediatric dentistry.  Acidulated Phosphor Fluoride (APF) topical gels can cause surface degradation and  weight loss in composite resins and decrease their wear resistance. This study aimed to assess the effect of APF gel on the microhardness of flowable composites.

Methods: This experimental in vitro study was conducted on 60 specimens measuring 2mm in thickness and 6mm in diameter fabricated of Tetric N-Flow (Ivoclar-Vivadent), PermaFlo  (Ultradent) and Denfil (Vericom) flowable composites (n=20 for each group). Specimens were stored in artificial saliva at room temperature for one week. The 20 specimens in each group were randomly divided into 2 subgroups of test and control (n=10). Microhardness was measured using Vickers microhardness tester. In the control groups, 3 indentations were made on each disc on the periphery of a circle with at least 1mm distance from one another and from the specimen margin.  The mean microhardness value was then calculated. The mean of all measurements was calculated  as well. Test specimens were subjected to (Sultan) 1.23% APF gel for 4min and then rinsed and air- dried. Their microhardness was measured again as described above. Two-way ANOVA was used to compare the effect of APF gel and type of composite on the microhardness of different flowable composites.

Results: Based on the results, the microhardness of Denfil, PermaFlo and Tetric N-Flow was 16.5 (1.32), 37.36 (2.13) and 20.39 (0.52) before and 16.46 (2.20), 35.04 (2.43) and 19.13 (2.20) after the

application of APF gel, respectively. The difference between the before and after values for each composite was significant (p=0.193) while the difference between different composites was statistically significant in this regard (p<0.001).

Conclusion: Exposure of Denfil, PermaFlo and Tetric N-Flow flowable composites to APF gel for 4min had no effect on their microhardness.

Objective: Vertical root fracture (VRF) is among the most common causes of endodontic treatment failures. This study aims to compare charge-coupled devices (CCD) and photostimulable phosphor plates (PSP) for detection of vertical root fractures in endodontically treated teeth.

Methods: In this diagnostic in vitro study, 40 maxillary anterior teeth were selected and after preparation and root canal filling, their crowns were cut 2mm above the cementoenamel junction (CEJ). The teeth were embedded in a piece of dried bone and radiographed using CCD and PSP with equal geometry at zero and 15° horizontal angles. VRFs were then induced and the fractured fragments were reattached. The teeth were radiographed again. Three observers evaluated the radiographs for detection of fracture line. Data were analyzed using the Proportion test and Wilcoxon’s Signed Ranks test.

Results: No significant difference was found between the two sensors in detection of VRFs [p-value (complete)= 0.592, p-value (absolute)= 1]. The sensitivity of the two sensors for detection of buccolingual and mesiodistal fractures was not significantly different [p-value BL (absolute)= 0.109, p-value BL (complete) 0.180] [p-value MD (complete)=0.593, p-value MD (absolute)= 0.102]. The sensitivity of both sensors for detection of buccolingual fracture was higher than for mesiodistal fractures (p<0.001).

Objective: Nanosilver has numerous applications in medicine due to its potent antibacterial activity. However, data regarding the bio-safety of its effective concentrations is scarce. This study aims to assess the toxicity of silver nanoparticles on human gingival epithelial cells under in-vitro  conditions.

Methods: This in vitro study evaluated the toxic effects of filtered and unfiltered nanosilver solution on human gingival epithelial cells obtained from the Pasteur Institute of Iran using the methylthiazol tetrazolium bromide (MTT) assay (mitochondrial function)and membrane leakage of lactate dehydrogenase (LDH) at 24, 48 and 72h time points. The concentrations of silver nanoparticle solution used were 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20 and 50µg/ml.

Results: The MTT assay showed that nanosilver solution at high concentrations (20 and 50µg/ml) significantly decreased the viability of cells at all time points. The lower non-fatal concentrations at 24 and 48h were capable of causing cell death or significantly inhibit cell growth at 72h. The LDH assay demonstrated that death of epithelial cells only occurs at high concentrations of nanosilver (20 and 50µg) and no significant toxicity was seen at lower concentrations.

Conclusion: Based on the results, silver nanoparticles have toxic effects on human gingival epithelial cells and this effect is time and dose-dependent.

Objective: Corrosion resistance is among the most important properties of metal alloys used in the oral cavity. Consumption of acidic foods reduces the salivary pH and intensifies the corrosion of brackets and orthodontic wires. This study aimed to compare electro galvanic corrosion of different orthodontic brackets and wires and determine the amount of ions released into acidic artificial saliva. Methods: In this in vitro experimental study, 24 mandibular incisor brackets of 4 different manufacturers (Dentaurum, American Orthodontics, Shinye and ORJ) with stainless steel (SS) or nickel-titanium (Ni-Ti) round wires 0.016 were immersed in acidic artificial saliva for 28 days and their potential difference with the reference electrode was recorded. The amount of released ions was measured in the solution using atomic absorption method. Data were analyzed using two-way ANOVA and repeated measures ANOVA.

Results: The mean amount of ions released was not significantly different between groups (p>0.05). The potential difference of Shinye brackets coupled to SS wire was significantly lower than that of other combinations and was negative throughout the study. The potential difference of Dentaurum bracket-NiTi wire, ORJ bracket-NiTi wire, Shinye bracket-SS wire and ORJ bracket-SS wire combinations at the end of experiment was negative as well.

Conclusion: The galvanic corrosion of Shinye bracket coupled to SS wire in acidic artificial saliva was greater than that of other bracket-wire combinations. The specimens were not significantly different in terms of the released ions.

Objective: Although the most useful method to reduce mechanical dental plaque is brushing and flossing, but due to the lack of adequate effectiveness achieved by these methods, the use of other methods such as replacing sweeteners, including Xylitol and Sorbitol with sucrose in products such as chewing gums have come into the focus of attention. This research was done aimed at examine the effect of gum types containing Xylitol, Calcium and Xylitol or Sorbitol on dental plaque pH changes.

Methods: The study was performed as a randomized, single-blind, cross-over clinical trial on 10 female students with an age range of 20 to 30 years old studying in dental school, Azad University. Plaque pH changes were measured using PH Meter device after taking four types of chewing gums containing Xylitol, Sorbitol, Xylitol+ Calcium, Turpentine and 10% sucrose solution as control in  the follow-up periods. To compare pH at any time between different materials, the Cried-mann test was used. For group pair comparison, Wilcoxon-signed rank test and Bone-Serroni-Adjusment test were used.

Results: Xylitol had the highest average plaque pH during the period time that pH increase at minute 7 was the maximum, and turpentine had the lowest pH at all moments, which reached to  its maximum at minute 2 and showed little change in plaque pH increase up to minute 60. The difference between all four types of materials was significant (p<0.001).

Conclusion: The use of chewing gum after drinking sugar syrup caused a significant plaque pH increase within 7 minutes up to the initial normal level that the effect of Xylitol chewing gum was significantly higher than the rest.

Objective: Amorphous calcium phosphate (ACP) is a reactive solution capable of releasing calcium and phosphate ions, conversion to apatite and remineralization of mineral tooth structure. This study reviews ACP structure, its properties and its applications in dentistry.

Methods: In this review study, keywords including “amorphous calcium phosphate”, “mineralization”, “hydroxyapatite”, “casein phosphopeptide”, “tissue engineering” and “dentistry” were searched in articles published during 1953-2013 in PubMed, Science Direct, Google Scholar, Embase and Medline databases. A total of 134 articles were evaluated.

Results: ACP had high adhesion, adjustable dissociation rate, bone induction and excellent biocompatibility without cell toxicity. ACP alone or in combination with casein phosphopeptide (CPP) is incorporated into toothpastes, chewing gums, mouth rinses, tooth bleaching gels and food products to enhance remineralization and prevent demineralization. Also, it is used as filler in many dental materials namely glass ionomers, composite resins and bonding agents. Implant surface coating with ACP by radio frequency magnetron sputtering improves osseointegration especially at the final stages of healing.

Conclusion: ACP is suitable for tissue regeneration and healing and is a potential remineralizing agent in dentistry.