Effect of Tannic Acid and Quercetin Antioxidants on Bond Strength of Resin Cement to Dentin after Internal Bleaching.

PURPOSE: To evaluate the influence of tannic acid and quercetin on the immediate microshear bond strength (µSBS) of two resin cements to dentin after internal bleaching. MATERIALS AND METHODS: The access cavity in eighty extracted maxillary incisors was internally bleached except the control groups. The labial surfaces were ground to expose a flat dentin surface. The specimens were randomly divided into eight groups (n=10) as follows: 1) Control/Dou; Doulink without bleaching, 2) Bl/Dou; Bleaching+Doulink, 3) Bl+Ta/ Dou; Bleaching+Tannic acid+Doulink, 4) Bl+Qu/Dou;Bleaching+Quercetin+Doulink, 5) Control/ PSA; Panavia SA without bleaching, 6) Bl/PSA;Bleaching+Panavia SA, 7) Bl+Ta/ PSA; Bleaching+Tannic acid+Panavia SA, 8) Bl+Qu+PSA; Bleaching+Quercetin+Panavia SA. After 24 hours, the µSBS of the specimens was tested and the obtained data were analyzed with two-way ANOVA and Tamhane test (p⟨0.05). RESULTS: The µSBS of Doulink groups were higher than the PSA groups (p⟨0.001). The µSBS of Bl+Ta/Dou and Bl+Qu/ Dou groups did not differ from Bl/Dou (p⟩0.05). The µSBS of Bl+Ta/PSA group was statistically significantly higher than the Bl/PSA group (p⟨0.001). There was no significant difference between µSBS of Bl+Qu/PSA and Bl/PSA groups (p=0.39). CONCLUSIONS: TA partially reversed the negative influence of internal bleaching on the µSBS of Panavia SA while quercetin did not increase the bond strength of both resin cements.

Effect of reducing acid-etching duration time on compressive strength and bonding of a universal adhesive to calcium silicate cements.

AIM: To assess the effect of acid-etching duration time on the compressive strength, microstructure and shear bond strength of All-Bond Universal adhesive to MTA-Angelus (AMTA), and Biodentine (BD). METHODOLOGY: Forty-eight cylindrical specimens (4 mm in diameter, 6 mm in height) of AMTA in four groups and 48 specimens of BD in four groups (n = 12) were prepared and stored for 72 h. The control groups were unetched whilst the three experimental groups were acid-etched for 5, 10 and 15 s, respectively, followed by compressive strength testing. The effect of the various acid-etching times on surface micromorphology was evaluated under a scanning electron microscope. Similar groups were bonded using All-Bond Universal and Aelite Flo and shear bond strength was tested. Data were analysed using two-way ANOVA and Tukey tests. RESULTS: 10-s and 15-s acid-etching reduced the compressive strength of AMTA and BD (P < 0.001), while 5-s etching did not (P ≤ 0.86). In all the groups, BD had greater compressive strength compared to AMTA. Contrary to BD, the three etched AMTA groups had significantly higher shear bond strength compared to the control group (P < 0.001), with no significant differences between them. The etched groups of AMTA had shear bond strengths comparable to all the BD groups. Scanning electron microscope observations indicated variable surface morphologies such as remnant crystals and cracking/eroding in all our groups of AMTA; though these differences were less prominent for BD. CONCLUSIONS: Shortening the acid-etching time to 5 s resulted in a beneficial effect in terms of resin bonding for AMTA while preventing the detrimental effect of 10-s and 15-s etching on the compressive strength of AMTA and BD. However, the three etching times had no effect on resin-BD bond.

Analytic height correlation function of rough surfaces derived from light scattering.

We derive an analytic expression for the height correlation function of a homogeneous, isotropic rough surface based on the inverse wave scattering method of Kirchhoff theory. The expression directly relates the height correlation function to diffuse scattered intensity along a linear path at fixed polar angle. We test the solution by measuring the angular distribution of light scattered from rough silicon surfaces and comparing extracted height correlation functions to those derived from atomic force microscopy (AFM). The results agree closely with AFM over a wider range of roughness parameters than previous formulations of the inverse scattering problem, while relying less on large-angle scatter data. Our expression thus provides an accurate analytical equation for the height correlation function of a wide range of surfaces based on measurements using a simple, fast experimental procedure.

Effect of Carbodiimide on Bonding Durability of Adhesive-cemented Fiber Posts in Root Canals.

This study was undertaken to investigate whether using a protein cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), improves bonding stability of fiber posts to root dentin using three resin cements. Sixty human maxillary central incisor roots were randomly divided into six groups after endodontic treatment, according to the cements used with and without EDC pretreatment. In the etch-and-rinse group, 0.3 M EDC aqueous solution was applied on acid-etched root dentin prior to Excite DSC/Variolink II for post cementation. In the self-etch and self-adhesive groups, EDC was used on EDTA-conditioned root space prior to application of ED Primer II/Panavia F2.0 and Clearfil SA, respectively. After microslicing the root dentin, a push-out bond strength (BS) test was performed immediately or after one-year of water storage for each group. Data were analyzed using three-way analysis of variance and Tukey tests (α=0.05). A significant effect of cement type, time, EDC, and Time × Cement and Time × EDC interactions were observed (p≤0.001). EDC pretreatment did not affect immediate bonding of the three cements (p>0.05). Aging significantly reduced the BS in all the groups (p≤0.001), but EDC groups exhibited a higher BS compared with the respective control groups (p<0.001). Despite the significant effect of aging on decreasing the BS of fiber post to radicular dentin, EDC could diminish this effect for the three tested cements.

Direct esthetic rehabilitation of teeth with severe fluorosis: a case report.

This article describes an esthetic rehabilitation of a case of severe fluorosis associated with tooth mobility and gingival recession. Direct composite technique was applied to improve the color, shape and alignment of the teeth using direct composite veneering and replacement of the missing tooth by fiber-reinforced composite bridge. One year follow up have displayed acceptable outcomes and esthetic appearance.

Microleakage of nanofilled resin-modified glass-ionomer/silorane- or methacrylate-based composite sandwich Class II restoration: effect of simultaneous bonding.

OBJECTIVES: Microleakage of composite restorations at the cervical margin placed apically to the cementoenamel junction (CEJ) is still a concern. This study evaluated the effect of simultaneous bonding application on cervical sealing of nano-ionomer/silorane- or methacrylate-based composite open sandwich Class II restorations in the modified technique compared with that of conventional bonding. METHODS AND MATERIALS: In 60 sound maxillary premolars, two standardized Class II cavities were prepared with cervical margins 1 mm below the CEJ. The teeth were randomly divided into six groups of 10 teeth each. In the first three groups (groups 1-3), Clearfil SE Bond and Clearfil APX (Kuraray) were used for restoration in the total bonding technique (group 1), conventional open sandwich technique associated with a nano-ionomer (Ketac N100, 3M ESPE) (group 2), and modified open sandwich technique with simultaneous bonding application for both nano-ionomer and composite (group 3). In the second three groups (groups 4-6), Silorane Adhesive and Filtek Silorane composite (3M ESPE) were used in the same manner as in the first three groups, respectively. RESULTS: The simultaneous bonding application in the modified sandwich restorations (with SE Bond or Silorane Adhesive) resulted in a significant reduction of the cervical microleakage compared with that of the conventional bonding (p<0.05). However, microleakage of the modified technique was similar to that of the total bonding (with SE Bond or Silorane Adhesive) (p>0.05), both showing good marginal seal.

Effect of a Combined Bleaching Regimen on the Microhardness of a Sealed Methacrylate-based and a Silorane-based Composite.

STATEMENT OF PROBLEM: The use of tooth bleaching agents has been very popular treatment in dentistry. The bleaching agents have an inherent potential to impair surface properties of existing composite resin restorations. PURPOSE: This study evaluated the effect of a combined bleaching regimen on the surface microhardness of a Silorane-based and a sealed methacrylate-based composite. MATERIALS AND METHOD: Forty-five specimens of methacrylate-based composite (Ice) and 18 specimens of Silorane composite (Filtek Silorane, 3M ESPE; USA) were prepared and randomly divided into 5 (1-5) and 2 (6-7) groups (n=9), respectively. After 8-week aging, groups 1 and 6 were remained with no treatment. In groups 2, 4 and 5, the specimens were covered by a surface sealant and light cured. In groups 3, 4, 5 and 7, the specimens were bleached with hydrogen peroxide 40% and then carbamide peroxide 20% for seven days. In group 5, after bleaching, the sealant was removed by polishing. Surface microhardness was measured and the data were analyzed using one-way ANOVA and Tukey tests (α=0.05). RESULTS: The microhardness values of groups 2 to 4 were significantly lower than that of group1 (p <0.05). There was no significant difference among groups 1, 5, 6 and 7 (p> 0.05). CONCLUSION: The combined bleaching regimen used in this study had a substantial negative effect on methacrylate and sealed methacrylate composites but not on Silorane composite. Polishing following the bleaching on the sealed composite yielded a hardness value similar to that of unsealed methacrylate composite (control).

Fracture resistance of cuspal coverage of endodontically treated maxillary premolars with combined composite-amalgam compared to other techniques.

This in vitro study investigated the fracture resistance of teeth restored with combined composite-amalgam for cuspal coverage compared to direct coverage with composite (with or without an amalgam base) and composite onlay. Seventy-two intact maxillary premolars were randomly divided into six groups (n=12). The two control groups were G1, intact teeth (negative control), and G2, mesio-occlusodistal preparation only (positive control). Each of the four experimental groups used a different type of restoration for the prepared teeth: G3, direct composite cusp coverage; G4, composite onlay; G5, direct composite coverage with an amalgam base; and G6, combined composite-amalgam cuspal coverage. After thermocycling, fracture strength was tested. The data were analyzed with analysis of variance and the least significant differences post hoc tests (α=0.05). Mean fracture resistance in the six groups (in N) were G1, 1101 ±1 86; G2, 228 ± 38; G2, 699 ± 161; G4, 953 ± 185; G5, 859 ± 146; and G6, 772 ± 154. There were significant differences between G1 and all the other groups except for G4 and between G2 and all the other groups. Fracture strength in G3 also differed significantly compared to G4 and G5. The difference between G4 and G6 was statistically significant (p<0.05), but the difference between G3 and G6 was not (p>0.05).

Isolation of acanthamoeba spp. From drinking waters in several hospitals of iran.

BACKGROUND: Acanthamoeba is an opportunistic amphizoic protozoan found in different water sources including swimming pool as well as in sewage. The aim of this study was to investigate the prevalence of Acanthamoeba in tap-water samples in Iran. METHOD: In this descriptive cross-sectional study, 94 samples of cold and warm tap-water were collected from different wards of hospitals in 13 cities of Iran in 2007-2008. Free residual chlorine, pH, and temperature of samples were measured. After filtration through multipore nylon membrane, samples were cultured on non-nutrient agar. Then we investigated existence of Acanthamoeba by reverse contrast phase microscope. RESULTS: Acanthamoeba was found in 45 samples (48%). Thirty-four and 11 positive samples were collected from cold and warm tap water, respectively. The samples belonged to the category of 20-30°C temperature with 0-2 ppm free residual chlorine and pH 6-7.4 showed the most coincidence to the positive cases. The greatest proportion of positive samples was obtained from Mashhad hospitals, while all samples collected from Arak and Semnan hospitals were negative. CONCLUSION: considering the results of this study and the pathogenic role of this protozoan on patients with immunodeficiency, as well as capability of this microorganism in carrying other pathogens such as Legionella, further studies are needed. What is more important, potable water in hospitals should follow the procedure of treatment and sanitation, in order to prevent the relevant nosocomial infections.

DNMT3A and DNMT3B mediate autocrine hGH repression of plakoglobin gene transcription and consequent phenotypic conversion of mammary carcinoma cells.

Directed by microarray analyses, we report that autocrine human growth hormone (hGH) increased the mRNA and protein expression of DNA methyltransferase 1 (DNMT1), DNMT3A and DNMT3B in mammary carcinoma cells. Autocrine hGH stimulation of DNMT3A and DNMT3B expression was mediated by JAK2 and Src kinases, and treatment of mammary carcinoma cells with the DNMT inhibitor, 5'-aza-2'-deoxycytidine (AZA), abrogated autocrine hGH-stimulated cellular proliferation, apoptosis and anchorage-independent growth. AZA reversed the epitheliomesenchymal transition of mammary carcinoma cells induced by autocrine hGH, to an epithelioid morphology and abrogated cell migration stimulated by autocrine hGH. Autocrine hGH-stimulated hypermethylation of the first exon of the PLAKOGLOBIN gene and AZA abrogated the ability of autocrine hGH to repress plakoglobin gene transcription. Small interfering RNA (siRNA)-mediated depletion of the individual DNMT molecules did not release autocrine hGH repression of PLAKOGLOBIN promoter activity nor did individual DNMT depletion affect autocrine hGH-stimulated migration. However, concomitant siRNA-mediated depletion of both DNMT3A and DNMT3B abrogated hypermethylation of the PLAKOGLOBIN gene stimulated by autocrine hGH and subsequent repression of plakoglobin gene transcription and increased cell migration. Thus, the autocrine hGH-stimulated increases in DNMT3A and DNMT3B expression mediate repression of plakoglobin gene transcription by direct hypermethylation of its promoter and consequent phenotypic conversion of mammary carcinoma cells. Autocrine hGH, therefore, utilizes DNA methylation as a mechanism to exert its oncogenic effects in mammary carcinoma cells.

Artifacts from dental casting alloys in magnetic resonance imaging.

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm(2)) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts.