Journal of Dental School
Volume:31 Issue: 4, 2014

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

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. 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. 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 in significant (P=0.193) while the difference between different composites was statistically significant in this regard (P<0.001). Exposure of Denfil, PermaFlo and Tetric N-Flow flowable composites to APF gel for 4min had no effect on their microhardness.

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. 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. No significant difference was found between the two sensors in detection of VRFs [P (complete)=0.592, P (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). CCD and PSP had equal efficacy for detection of VRFs in endodontically treated teeth.

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