Specimens In Control Group Research Articles

Microleakage of Single-Cone Gutta-Percha Obturation Technique in Combination with Different Types of Sealers.

Introduction:Various materials and methods have been recommended for successful root canal obturation. The aim of this experimental in vitro study was to compare the sealing ability of three root canal sealers AH-26, glass ionomer cement (GIC) and zinc oxide eugenol (ZOE) in single gutta-percha obturating system. Methods and Materials:Seventy extracted single-rooted human teeth were decoronated. The teeth were randomly divided into 3 experimental groups (n=20) and 2 positive and negative control groups. After root canal preparation, canals were obturated with single-cone method using either AH-26, GIC and ZOE. The leakage was evaluated using the dye penetration method. The samples were sectioned to evaluate the linear leakage using a stereomicroscope. The data were analyzed using the One-way ANOVA test. Results: All the specimens in the positive control group showed evidence of leakage. In the experimental groups, the lowest leakage scores were observed in the AH-26 group (P<0.05). However, there were no statistically significant differences between GIC and ZOE samples (P=0.676). Conclusion:AH-26 showed a superior seal and less microleakage compared to the two other materials in single gutta-percha obturating system.

Comparison of the Effect of Dentin Bonding, Dentin Sealing Agents on the Microleakage of Provisional Crowns Fabricated with Direct and Indirect Technique-An Invitro Study.

Postoperative sensitivity after temporization is a common complaint in Fixed Partial Denture patients. It is caused by weak and ill fitting temporary restorations which results in microleakage. This can be controlled by providing good temporary restorations and by coating the exposed dentinal tubules of the prepared tooth with dentin bonding agent or dental varnish. The purpose of the study was to determine the effect of dentin-bonding, dentin sealing agents on the microleakage of temporary crowns made by tooth colored auto polymerizing resin fabricated with direct and indirect technique. Thirty premolar and molar human teeth were collected which were extracted recently was used for the study. The teeth were marked and divided into 3 groups each containing 10 nos. They were individually mounted with self-cure acrylic resin. It was then mounted on a milling machine and crown preparations done. Temporary crowns were fabricated by direct and indirect method with two types of materials. In group A (Control group), the temporary crowns fabricated with both direct and indirect method were cemented directly with temporary luting cement. In group B dentine-bonding agent (solobond M) was applied once to the prepared surface of each tooth specimen before the cementation of temporary crowns where as in case of group C a single layer of dental varnish is applied prior to crown cementation. The entire specimens were immersed in 1% methylene blue and allowed to undergo thermal treatment. It was then sectioned in a hard tissue microtome. Each section was evaluated for dye penetration into the dentin tubules by comparing it with a visual scale. SPSS Version 13 software was used for non-parametric data analysis by a qualified statistician. P-values less than 0.05 (p-value<0.05) were considered to be statistically significant. Group B (Dentin Bonding Agent) specimens cemented with crowns fabricated in direct technique showed the least amount of microleakage when compared with group A and group C. Group C (Dental Varnish) specimen showed comparatively more amount of microleakage than that of group B. Group A (control group) specimens showed the maximum amount of microleakage. The application of a single layer of Dental varnish appears to be of no significant benefit when compared to crowns cemented with the application of Dentin bonding agent on the tooth surface. The application of a single layer of Dentin bonding agent (Solobond M) and temporary crowns fabricated with direct technique may be of some benefit for crown preparations as an interim measure prior to the luting of final crown.

Effect of intra-orifice barriers on the fracture resistance of endodontically treated teeth - an ex-vivo study.

The purpose of this study was to evaluate and compare the fracture resistance of roots obturated with guttapercha using bonded amalgam, GC Light cure GIC (resin modified glass ionomer cement) and Tetric N Flow (flowable hybrid composite) as different intra orifice barriers. Eighty freshly extracted mandibular premolars with straight roots were reduced to 14 mm from the coronal aspect. All canals were enlarged to size 30 and specimens were obturated with gutta percha cones, except for control group specimens the coronal 3 mm of root fillings of all other group specimens were removed with the aid of heated plugger. All samples were randomly divided into 4 groups of 20 specimens each. They were control, Fuji GC LC GIC, Tetric N Flow and Bonded Amalgam. After the placement of the intra orifice barrier materials, specimens stored at 37(o)C and 100% humidity for one week to allow the materials to set completely. After one week, all the groups were subjected to fracture resistance testing by using Universal testing machine. Data was analysed for significance by ANOVA (Analysis of variance) and further pair wise comparison was performed by Benferroni test. Level of significance was taken as 0.05. Tetric N Flow group showed better fracture resistance as compared to all other groups and Control group is least among the groups. Fracture resistance of Tetric N Flow compared with bonded amalgam was statistically significant. Tetric N Flow and Fuji GC LC GIC can be used as intra-orifice barriers with good fracture resistance in endodontically treated teeth.

English

The aim of this study was to study the effect of reinforcement of acrylic resin denture base polymer with chopped glass fibers and silver filler on the linear dimensional changes, and water sorption. The dimensional changes were measured immediately after processing, after 1, 2, 3, 7 and 14 days of water storage. Water sorption was measured after 7-days of water storage. The results revealed that both types of reinforcement affect the dimensional accuracy and water sorption of the test specimens when compared to the control unreinforced specimens. The greatest dimensional accuracy was found with the glass fibers reinforced test specimens. The lowest amount of water sorption was found with the silver-filled test specimens. It was concluded that both the tested reinforcing materials decreased the linear dimensional changes and water sorption as compared to the control group specimens.

Morphological alterations of periodontal pocket epithelium following Nd:YAG laser irradiation.

The purpose of this in vivo study was to examine morphologic alterations in the periodontal pocket epithelium with presence or absence of clinical inflammation following the use of the Neodymium: Yttrium-Aluminum-Garnet (Nd:YAG) laser irradiation. Subgingival Nd:YAG laser irradiation has been proposed as an alternative technique for treatment of chronic periodontitis. Several published studies have reported the clinical outcomes of such treatment. Twenty patients, diagnosed with moderate chronic periodontitis, were selected for the study. A total of 32 sites was identified and divided into a control (n=18) and laser-treated test groups (n=14). Probing depth (PD) and bleeding on probing (BOP) were recorded for all sites. Test sites were irradiated with an Nd:YAG laser using parameters of 2 W, 200 mJ pulse energy, and 10 pps delivered through a 320 μm diameter tip. Total laser treatment time ranged from 1 to 2 min. Following treatment, all specimens were harvested via biopsy and processed for scanning electron microscopy (SEM) and histologic examination. Control group specimens, depending upon initial PD, exhibited either a relatively smooth and intact epithelium with little desquamation (PD≤3 mm), or increasing degrees of epithelial desquamation and leukocytic infiltration at a PD of ≥4 mm. In the laser-treated test group, the specimens with PD≤3 mm that were BOP negative (-) exhibited a thin layer of epithelium that was disrupted. In the specimens with initial PD of ≥4 mm, complete removal of the epithelium whose extent and degree were increasing, was observed in the inflamed portion, while epithelium remained in the uninflamed portion. The SEM and histologic findings demonstrated the feasibility of ablating pocket epithelium with an Nd:YAG laser irradiation using parameters of 2 W of power (200 mJ, 10 pps). Furthermore, the presence or absence of clinical inflammation appeared to have an impact on the degree of laser-mediated epithelial ablation.

Effect of dentin proteoglycans on the bonding properties of dentin

To investigate the potential effect of proteoglycan (PG) and glycosaminoglycan (GAG) on the bonding of etch and rinse adhesive to dentin, in order to improve the bonding effect of dentin. Forty-two extracted molars were used to obtain standard dentin bonding surface, and the specimens were etched for 15 s with 37% phosphoric acid and divided into three groups using a table of random numbers. Then the three groups undergone different incubating procedures as follow: specimens in chondroitinase ABC (C-ABC) group were incubated with C-ABC at 37 °C for 48 h in vibrator. Specimens in trypsin (TRY) group were incubated with trypsin, and specimens in the control group were incubated with deionized water for 48 h in the oscillators. Then specimens in each group were randomly assigned into two subgroups, A (Adper(TM) Single Bond 2) and B (Prime & Bond NT) (n = 7). The microtensile bond strength (µTBS), fracture mode and bonding interface morphology of the specimens were evaluated via microtensile testing, stereo microscope and field emission scanning electron microscopy (FE-SEM) respectively after specimens being incubated in 37 °C water for 24 h. The immediate µTBS of C-ABC group bonding with adhesive A and B [(32.9±2.5) and (26.8±2.2) MPa] were significantly lower than that of the control group [(40.7±3.3) and (34.6±3.7) MPa] (P < 0.05). While the immediate µTBS of TRY group [(49.0 ± 3.6) and (44.5 ± 3.0) MPa] were significantly higher than that of the control group(P < 0.05). Dentin PG participates in the dentin bonding process. Removal of PG increased the immediate µTBS of dentin and total etching adhesives, while removal of GAG decreased the immediate µTBS.

Abstract 548: CEP 3/CEP 17 in the genetic diagnosis and its prognostic relevance of Kazakh esophageal cancer patients

Abstract To investigate the clinical application value of centromere of chromosome 3 and 17 (CEP 3, CEP 17) DNA probes in Kazakh esophageal squamous cell carcinoma (ESCC) patients’ molecular pathological diagnosis and prognosis. Forty patients with ESCC who received radical surgical treatment and 10 cases of normal specimen in control group were enrolled in this study. Touch preparations of fresh cancer and normal tissue were made and fluorescence in situ hybridization (FISH) technique were used to count the copy numbers of CEP 3 and CEP 17, abnormalities were analyzed comparing with routine pathological diagnosis. FISH analysis revealed that abnormal copy numbers of CEP 3, CEP 17 (aneuplody) were observed in 40 cases. CEP 3 and CEP 17 polyploidy rates were 42%, 40.5% in well-differentiated, 62.9%, 46.8% in moderately differentiated, and 76.95%, 63.5% in poorly differentiated ESCC respectively. These were significantly different between poorly differentiated, moderately differentiated and well-differentiated groups (p&amp;lt;0.05, p&amp;lt;0.05), and the polyploidy rates were also significantly higher in the group with lymph node metastasis comparing to the group without lymph node metas-tasis (CEP 3, p=0.0001; CEP 17, p=0.012). The CEP 3, 17 variations were shown to be correlated with the level of differentiation and lymph node metastasis in ESCC. Therefore, there DNA probes may be the predictive biological marker in the prognosis of patients with ESCC. In addition, being an objective and qualitative method, the technology of FISH can detect CEP 3, 17 variations in the genetic diagnosis of Kazakh ESCC. Note: This abstract was not presented at the meeting. Citation Format: Edris Awut. CEP 3/CEP 17 in the genetic diagnosis and its prognostic relevance of Kazakh esophageal cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 548. doi:10.1158/1538-7445.AM2014-548

Factors affecting the mechanical behavior of Y-TZP

AimThe aim was to evaluate the influence of sandblasting with various propulsion pressures on the phase transformation, flexural strength and Weibull modulus of a yttria stabilized tetragonal zirconia polycrystalline ceramic (Y-TPZ). In addition, the susceptibility of cyclic loading and low-temperature degradation under two different conditions (chemical and thermal aging) was investigated. Materials and methodsThe specimens [105bar-shaped specimens (19.3×14.5×1.3mm3)] were equally divided into seven groups (n=15) according to the test protocols. The specimens in control group received no surface treatment (Group A). Groups B1, B2 and B3 were airborne-particle abraded with 110μm Al2O3 particles at 200kPa, 400kPa and 600kPa (2bar, 4bar and 6bar) pressure, respectively. Group C was submitted to mechanical cyclic loading under 200N 20,000 times sinusoidal loading/unloading at a frequency of 10Hz between 10% and 100% load in distilled water at 37°C. Group D was submitted to thermal degradation in an autoclave at 134°C under additional 200kPa pressure for 5h. Group E was immersed in 4% acetic acid at 80±5°C for 168h as chemical degradation testing. Following each treatment protocols, the three-point flexure test was used to calculate the flexural strength. Additionally, X-ray diffraction analysis was used to estimate the relative amount of monoclinic phase. The reliability of strength was assessed through the Weibull distribution. Statistical analysis was conducted with one-way ANOVA and Tukey׳s pairwise multiple comparisons. The treated and fractured surfaces were observed with SEM. ResultsStatistical analysis revealed that there were significant differences among the flexural strength results of all tested groups (F=4.510, p<0.05). Group B2 demonstrated the highest strength values, whereas Group E showed the lowest (625.86±123.57; 466.56±91.50, respectively). Weibull moduli of all tested groups were statistically significant and ranging from 4.3 to 8.3. A greater amount of monoclinic phase was determined in the specimens of D, E and B3 groups (25.43%, 20.89% and 19.71%, respectively). However, lower amount was observed in groups A, B1 and B2 (10.02%, 13.35% and 15.19%, respectively). ConclusionsThe present study suggested that flexural strength of zirconia was significantly decreased by chemical degradation. In addition, surface conditioning, cyclic fatigue and thermal, chemical degradation conditions significantly changed the structural reliability of the material's strength.

Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): b-histological alterations in testes.

The present study investigates the effects of different doses (0, 40, 60, 100 μg/L) of 4-nonylphenol (NP) on testis histology and sperms motility of mature Oreochromis niloticus. A tendency for a dose-dependent reduction in the gonado-somatic index (GSI) in the NP-exposed groups was observed. Histological examination revealed that high doses of NP (60 and 100 μg/L) cause hyperplasia of interlobular connective tissue components coincide with decrease in the size of seminiferous lobules and amount of lumen spermatozoa in comparison with the control and low-dose (40 μg/L)-exposed groups. In addition, within the seminiferous lobules, rupture of spermatogenic cysts, vacuolation and necrosis of primary spermatocytes due to damage of sertoli cells were clearly observed and lead to decrease in advanced spermatogenic cells. The highest dose caused significant decrease in the GSI associated with appearance of testis-ova (intersex) state. The percentage of abnormal sperms increased with increasing the dose of NP reaching to 96 % for those subjected to 100 μg NP/L, while it was only 11 % for the control group specimens. The study indicates that NP has estrogenic potency induced marked alteration in the sexual development including inhibition in testicular growth and deformation in the sperms.

Study of celluar toxicity and antibacterial property of nano-silver coating modified denture base

To investigate celluar toxicity and antibacterial property of nano-silver coating modified denture base and to provide a theortical basis for clinical application. The samples were divided into coating group and denture base group. Samples in coating groups were treated with silver ion sputtering and were further divided into the 10, 20, 40, 60, 80, 100 s subgroups according to their sputtering time. Surface microstructure of samples in coating groups and denture base group were observed by scanning electron microscopy (SEM), and composition of material surface were determined with energy dispersive spectrum (EDS) analysis. Methyl thiazolyl terazolium (MTT) method was used to analysis L929 cells proliferation rate and cell toxicity grade while the coating groups (n = 6) and group test specimens (n = 6), negative control (polyethylene, PE) (n = 6) and positive control group (PVC-org.Sn) (n = 6) were co-cultured with L929 cells. The antibacterial properties of coating groups were investigated by using the bacterial membrane adhering method with Streptococcus mutans and Candida albicans. SEM observation showed that the surface of control group specimens were smooth, whereas dense and uniform distributed nano silver particles were visible on the surface of coating group specimens. The silver particles were round, and the diameter size was 10 nm. MTT assay showed that after being co-cultured with specimens in control group, L929 cell had higher proliferation rate than 100% at 24, 48, 72 h, and cytotoxicity were graded 0. The membrane adhering method results showed that all of bacterial colonies were found in control group, but without anything at the coating groups. Deposition of nano silver on the denture base surface by ion sputtering method is a viable method. There's no cytotoxicity of series Ag-coating material. Nano-silver modified denture base material benefits L929 cell surface proliferation and has antibacterial action.

Quantification of the amount of light passing through zirconia: The effect of material shade, thickness, and curing conditions

ObjectiveThis study aimed to evaluate the amount of light (360–540nm) passing through shaded zirconia with respect to material thickness, exposure distance, and different curing modes. MethodsThe specimens were divided into groups according to thickness as follows: 0.5, 1, 1.5, 2, 2.5, and 3mm. Thirty-five zirconia and seven glass-ceramic (control group) specimens were fabricated for each group (N=252). Zirconia was divided into five subgroups (n=7) and stained to the following shades: CL1, CL2, CL3, and CL4. One zirconia group remained unstained (CL0). Irradiance passing through the different specimens was measured using a violet-blue LED curing unit in three curing modes (Xtra-power, high-power, and standard-power mode) with a fibre-optic USB4000 spectrometer. Irradiance was measured at varying exposure distances, ranging from direct contact of the curing unit with the surface to a distance of 7mm from the surface, increasing in 1mm steps. Data were analyzed using a multivariate analysis and linear mixed models (p<0.05). ResultsThe control group, the glass-ceramics, transmitted the highest irradiance values, followed by CL0 (unshaded zirconia), CL1 (∼A1/B1), CL2 (∼A3/A3.5/A4/B3/B4), and CL3 (∼A3.5/B3/B4/C3/D3), respectively. The highest transmitted irradiance was measured at a specimen thickness of 0.5mm for all materials, decreasing exponentially with increased ceramic thickness. Within one type of ceramic, one thickness, and one polymerization mode, a decrease in transmitted irradiance with increased exposure distance could be observed only at a distance of 3mm and above. ConclusionsUnshaded zirconia was significantly less translucent compared with the glass-ceramic, but the translucency decreased slower with material thickness. The Beer–Lambert law describes well the decrease of transmitted irradiance with an increase of the specimens’ thickness for all materials. Except for dark ceramics, this would allow for calculating the transmitted irradiance through any material thickness and any initial irradiance. Clinical significanceThe amount of light passing through ceramics is an important aspect for an adhesive cementation, since many dual-cured luting materials reveal a high sensitivity to additional occurrence of blue light. For restorations thicker than 1.5 mm in light-shaded zirconia and 0.5 mm in darker-shaded zirconia the use of less-light-sensitive dual-cured cements are recommended.

Diagnostic and prognostic impact of peritumoral stromal remodeling in patients with surgically treated invasive penile squamous cell cancer

Stromal remodeling (SR), characterized by focal loss of CD34(+) fibrocytes paralleled by a gain of α-smooth muscle actin (α-SMA)-positive myofibroblasts, has been reported in several cancer types. However, the role of SR in invasive penile squamous cell cancer (PSC) has not been investigated so far. We compared 90 surgically treated PSCs (study group) and 55 control specimens (33 foreskins and 22 differentiated penile intraepithelial neoplasias) for the presence of stromal CD34(+) fibrocytes and α-SMA-positive myofibroblasts scored by independent raters. Multivariate proportional hazards regression analysis was used to assess the impact of staining profiles on cancer-specific mortality of the 90 PSCs (median follow-up, 32 months; interquartile range, 6-64). The incidence of SR differed significantly between study and control group specimens (51.1% versus 9.1%; P < .001). Five years postsurgically, 24% and 46% of the study patients without and with SR had succumbed to their PSC (P = .010). After adjusting for the age at the time of surgery, type of surgery, tumor size, Broders' grade, pT stage, and nodal status, study patients with SR showed 3.76-fold increased cancer-specific mortality (95% confidence interval, 1.3-10.5; P = .012). Our findings suggest that SR might have prognostic as well as some limited differential diagnostic value in terms of delineating invasive PSC from preinvasive lesions. However, our preliminary data clearly need to be validated by larger advanced studies in the future.

Investigation of the Presence of Mycobacterium tuberculosis in the Lymph Node Aspirates of the Suspected Tularemia Lymphadenitis Cases

Recently reports of cervical tuberculous lymphadenitis and oropharyngeal tularemia which are the most common infectious causes of granulomatous lymphadenitis, have been significantly increased in Turkey. The differentiation of cervical tuberculous lymphadenitis and oropharyngeal tularemia is usually confusing on the basis of clinical and histopathological findings. Thus, in tularemia endemic areas, the patients are more commonly evaluated in terms of tularemia lymphadenitis leaving tuberculosis out. The aim of this study was to investigate the presence of Mycobacterium tuberculosis in cervical lymph node aspirates, obtained from tularemia suspected cases. A total of 105 oropharyngeal tularemia-suspected cases which were found negative for Francisella tularensis by bacteriological (culture), molecular (PCR) and serological (microagglutination) methods, were included in the study. The samples had been previously studied at National Tularemia Reference Laboratory, Turkish Public Health Institution, between 2009-2011. The study samples were evaluated in terms of M.tuberculosis by culture and real-time PCR (rtPCR) methods in the National Tuberculosis Reference Laboratory. Both Lowenstein-Jensen (LJ) medium and liquid-based MGIT (BD, USA) automated culture system were used for mycobacterial culture. Samples that yielded mycobacterial growth were identified as M.tuberculosis by immunochromotographic test (BD, USA). The lymph node aspirates of 65 patients who were F.tularensis PCR negative but antibody positive, were used as the control group. As a result, M.tuberculosis was found to be positive in 9 (8.6%) of 105 tularemia-negative lymph node aspirates, sent to our laboratory from different geographic regions for the investigation of tularemia. Six of the M.tuberculosis positive cases were male and the age range of the patients was 26-85 years. The presence of M.tuberculosis was detected only by culture in two samples, only by rtPCR in five samples and both by culture and rtPCR in two samples. M.tuberculosis was not identified in the control group specimens. Three of the samples which revealed tuberculosis, were from the tularemia endemic areas. In conclusion, the data of this preliminary study indicated that tuberculous lymphadenitis should be kept in mind in suspected tularemia cases and those patients should also be investigated simultaneously for the presence of tuberculous lymphadenitis.

Assessment of thicknesses and color properties of opaque porcelain layers applied by different dental technicians

The aim of the present study was to evaluate the effect of individual manipulative variations on the thickness and color values of opaque porcelain layers applied by different dental technicians. A total of 11 dental technicians applied opaque porcelain onto prepared metal specimens (n=10). The thicknesses of these opaque porcelain layers were measured with an ultrasonic device, and color values were evaluated using a spectrophotometer. Obtained values were compared with those of the control group specimens (n=10), which were fabricated by a prosthodontist. Opaque porcelain thickness values of metal specimens applied by 10 dental technicians were significantly different than those of the control group. Color values of opaque porcelain layer applied by nine dental technicians were significantly different than those of the control group. It was concluded that the opaque porcelain layer thickness and color values may be affected by individual manipulative variations by the different dental operators according to results of present study.

Primary Cilia Metaplasia in Renal Transplant Biopsies with Acute Tubular Injury

Primary cilia are hair-like organelles singly distributed along the apical surface of proximal and distal nephron tubules as mechanosensors. The goal of this study was to use electron microscopy to systemically evaluate cilia changes in acute tubular injury (ATI) from both transplant and native renal biopsies. Three groups of cases were included: control group 1—native biopsies without major changes in renal tubules; study group 2—native biopsies with prominent ATI; and study group 3—renal transplant biopsies with prominent ATI (delayed renal function group). Extensive search for ciliary structures along renal tubules was conducted in each case, focused on proximal tubular areas with injured (diminished) apical microvilli. Singly located cilia were found in 3/19 specimens in control group 1, 4/18 in group 2 (native ATI), and 6/24 in group 3 (transplant ATI). Importantly, there were clusters of cilia in proximal tubules with markedly diminished apical microvilli in 3/24 biopsies from 2 patients in group 3, but none from groups 1 and 2. The clusters of cilia ranged from 6 to 15 individual cilia along the apical surface with diminished apical microvilli. Under high magnifications, the cilia demonstrated 9 pairs of peripheral microtubules without a central pair of microtubules, consistent with primary cilia (9 + 0) rather than motile cilia (9 + 2). In summary, the authors found clusters of cilia in proximal tubules with remarkable apical microvillar injury in 3 renal transplant biopsies with ATI, implying a reactive, or repairing, process following tubular injury, thus they name this finding “cilia metaplasia".

Evaluation of Effectiveness of Microwave Irradiation for Disinfection of Silicone Elastomeric Impression Material

Use of domestic microwave oven has been suggested as a method of disinfecting a number of dental materials used in dental practice. This study was done to analyse the effect of microwave irradiation on vinyl polysiloxane putty impression material (3M ESPE, Express™ STD) contaminated with test organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans. 180 square shaped specimens of addition silicon putty material were prepared and divided into 3 groups for three test organisms. The 3 groups were subdivided into 4 subgroups (n=15) for different exposure parameters (control group 5, 6 and 7min exposure at 650W. The specimens were contaminated using standard inoculums of test organism and then were irradiated using domestic microwaves. Broth cultures of the control and test group specimens were plated on selective media culture plates. Colonies formed were counted. Data analyses included Kruskal-Walli's ANOVA and Mann-Whitney's tests. Nil values shows complete elimination of C. albicans and P. aeruginosa after 5, 6 and 7min exposure. Staphylococcus aureus showed colonies with the mean value of 7.6×10(3)±2.3×10(3), 4.6×10(3)±2.6×10(3) after 5 and 6min respectively and nil values after 7min exposure. 5min exposure caused complete elimination of C. albicans and P. aeruginosa strains, while 7min exposure eliminated S. aureus completely.

The effect of home-bleaching application on the color and translucency of five resin composites

ObjectivesThe aim of this study was to investigate the effect of home bleaching agents on the color and translucency of resin composites. MethodsThirty disc shaped specimens (1mm thick) were fabricated from each resin composite (Reflexions, Grandio, Gradia Direct, Clearfil Majesty Esthetic, Ceram-X Mono) and divided into 3 subgroups as carbamide peroxide (CP, Opalescence 10% PF), hydrogen peroxide (HP, 10% Opalescence Treswhite Supreme) and control group (n=10). Baseline CIE L*a*b* color coordinates were measured with spectrophotometer and translucency parameters (TP) were calculated. CP and HP groups were treated with bleaching agents according to manufacturers’ instructions and control group was stored in distilled water (DW) for 14 days. Color and translucency measurements were repeated and color differences were calculated, ΔE values>3.3 were considered as clinically unacceptable. ResultsClinically unacceptable color change was detected for all resin composites exposed to bleaching agents and there was significant color difference between the control group and bleached specimens (P<0.05). However no significant color difference was found between CP and HP groups. Intragroup comparison revealed that Ceram-X Mono showed the highest color change but there was no significant difference among the other tested materials for both CP and HP groups. Intergroup comparison of TP values of CP, HP and control groups at the end of 14th day revealed that there was no statistical significant translucency difference among the groups. ConclusionsApplication of CP and HP resulted in clinically unacceptable color change for all resin composites. Translucencies of the resin composites were not affected by bleaching procedure. Clinical significanceThe results of this in vitro study suggest that patients should be informed regarding a potential color change of existing resin composite restorations with the use of home bleaching agents.

Effect of MTA and Portland Cement on Fracture Resistance of Dentin.

Background and aims. It is important to evaluate the effects of endodontic materials on tooth structures to avoid endodontic treatment failure. The aim of the present study was to investigate the effect of mineral trioxide aggregates (MTA) and Portland cement (PC) on fracture resistance of dentin. Materials and methods. Thirty-six freshly extracted human single-rooted premolar teeth were selected. The crowns were removed and the roots were randomly divided into two experimental groups and one control group. The root samples were longitudinally divided into two halves and a dentin bar (2×2×10 mm) was cut from each root section for short-term (2weeks) and long-term (12 weeks) evaluations. The root sections in the experimental groups were exposed to MTA or PC, while keeping the control group specimens in physiologic saline. The fracture resistance of each specimen was measured using an Instron testing machine. The results were statistically analyzed using ANOVA, a post hoc Tukey test and paired t-test at 5% significance level. Results. The fracture resistance of MTA-treated specimens significantly increased between 2 and 12 weeks (P<0.05). After 12 weeks, MTA-treated specimens had the highest fracture resistance. In the PC group, the fracture resistance of specimens did not change significantly over time (P>0.05). Conclusion. The results showed that MTA increased the fracture resistance of root dentin, while PC had no significant effect on dentin fracture resistance.

Study on decellularized laryngeal scaffold in dogs

To explore the survivorship and character of decellularized laryngeal scaffold in pectoralis major muscle flap in canine. Eighteen donor larynx in experimental group were decellularized by perfusing sodium dodecyl sulphate. Three of them were used to detect the character of histology. The other fifteen ones were embedded in right pectoralis major muscle flap of acceptor canine. Donor larynx in control group were not perfused. Other experimental procedure was the same as experimental group. The specimens were harvested at two weeks, one month and two months after operation, respectively. Macroscopic view, histological examination and trypan blue staining were performed in the experimental group and control group. The size of the specimens decreased remarkably into disappearance in control group, there was statistical significance between the experimental group and the control group (which used least significant difference t test P < 0.05). There was only little neutrophils and lymphocytes infiltrating around the laryngeal scaffold at 2 weeks in the experimental group. One month after operation, loose connective tissue begin to form around the laryngeal scaffold. After two months of transplantation, the connective tissue became thicker and the number of blood vessels increased than before. There was a large number of lymphocytes and neutrophil infiltration around the laryngeal specimens in the control group at 2nd week. The perichondrium in the control group was damaged at one month post operation. The cartilage cells could not be detected two months after surgery. The survival rate of cartilage cell between experimental group (86.8% ± 3.2%) and the control group (88.6% ± 3.1%) did not show statistical significance before implantation (χ(2) = 0.19, P > 0.05). The survival rate of cartilage cell decreased insignificantly in experimental group while the survival rate declined obviously in the control group at two weeks and one month after operation, the difference had statistical significance (χ(2) were respectively 5.52 and 20.55, P were respectively < 0.05 and < 0.01), the survival rate of cartilage cell in experimental group was (65.8% ± 2.6%) at two months after operation, while the cartilage cell all disappeared in control group. Perfused decellularation technique can construct a low immunogenicity laryngeal cartilage scaffold which can survive in the chest muscle package and establish a good blood supplement. The decellularized laryngeal scaffold could be used as a biological scaffold for whole laryngeal reconstruction.

An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers

Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.