Dimitrios Dionysopoulos

In Vitro Inhibition of Enamel Demineralisation by Fluoride-releasing Restorative Materials and Dental Adhesives.

PURPOSE To determine the ability of 5 contemporary fluoride-releasing restoratives and 3 fluoride-releasing adhesives to inhibit enamel demineralisation surrounding restorations, and the associations between inhibition and the levels of fluoride released from these materials. MATERIALS AND METHODS Five fluoride-releasing restoratives (Fuji IX GP, Ketac N100, Dyract Extra, Beautifil II and Wave) and 3 fluoride-releasing adhesives (Stae, Prime & Bond NT and Fluoro Bond II) were investigated. Eight disks of each material were prepared. Fluoride release was measured daily using a fluoride-ion-selective electrode for 15 days. Twenty-four cavities for each group were restored with a restorative and an adhesive. Specimens were subjected to thermal stress and stored for 30 days in saline solution. After a 15-day pH-cycling regimen, two 150-μm-thick sections were derived from each specimen. Enamel lesion depth was measured at 0, 100, and 200 μm from each restorations margin via polarised light microscopy. RESULTS Of the restoratives investigated, Fuji IX GP released the most fluoride. The fluoride-releasing restoratives tested exhibited shallower enamel lesions than did the control group at all distances tested (p < 0.05). Fuji IX GP yielded significantly lower enamel lesion depth than did the other experimental materials. The depths of enamel lesions did not differ significantly when comparing restoratives applied with a fluoride-releasing adhesive with those applied with a non-fluoride-releasing adhesive. CONCLUSION The fluoride-releasing materials tested reduced enamel demineralisation but to different extents, depending on their levels of fluoride release. Fluoride-releasing adhesives did not influence enamel lesion formation.

Effect of radiant heat and ultrasound on fluoride release and surface hardness of glass ionomer cements

Purpose The purpose of this investigation was to evaluate the influence of radiant heat and ultrasound on fluoride release and surface hardness of 3 glass ionomer cements (GICs). Methods There were 3 experimental groups for each GIC; in group 1, the specimens were left to set without any treatment; in group 2, the specimens were irradiated for 2 minutes using a LED unit; and in group 3, ultrasound was applied using a scaler for 55 seconds on the specimen surface. Fluoride release measurements were performed daily for 7 days and at days 14 and 28. Surface hardness of the tested GICs was determined using Vickers method. The measurements were performed 24 hours and 7 days after mixing. Statistical analysis of the data was made using 1-way ANOVA and Tukeys and Bonferroni post hoc tests (α = 0.05). Results Radiant heat during setting reduced the fluoride release and increased the surface hardness of GICs (p<0.05). Ultrasonic treatment also reduced the fluoride release and increased the surface hardness (p<0.05) of GICs but in lower extent. Among the GICs there were differences in fluoride release and surface hardness properties depending on their composition (p<0.05). Conclusions Radiant heat and ultrasonic treatments may be useful methods for GIC restorations in order to achieve faster adequate initial mechanical properties.

The influence of a novel in-office tooth whitening procedure using an Er,Cr:YSGG laser on enamel surface morphology.

The purpose of this in vitro study was to evaluate the influence of a novel in‐office tooth whitening procedure using Er,Cr:YSGG laser radiation on bovine enamel.

Effect of temperature, curing time, and filler composition on surface microhardness of composite resins

Aim: The aim of this study was to evaluate the microhardness of two composite resins when subjected to three different temperatures and three different light-curing times. Materials and Methods: Two composites were used; Filtek Z250 and Grandio. Three different temperatures (23, 37, and 55oC) were used, utilizing a composite warmer. The heated samples were immediately injected into cylindrical molds (6 mm × 2 mm) and the top surface of the specimens was polymerized for 10, 20, and 40 sec, using a Quartz-Tungsten-Halogen light-curing unit (QTH LCU). Vickers microhardness measurements were performed from both the top and bottom surface of the specimens, following dry storage for 24 hours in the dark. Statistical analysis were performed using one-way analysis of variance (ANOVA) and Tukey post-hoc test at a level of significance of a = 0.05. Results: The results indicated that there was an increase in microhardness as the temperature of the composite was increased for either the top or the bottom surface (P < 0.05). Furthermore, there was a general increase in microhardness for both composites as curing time increased (P < 0.05). The type of composites did not influence the surface microhardness (P > 0.05). Conclusions: Temperature of composites affects their surface microhardness. Also, light-curing time influence microhardness values of the composites tested.

Association of VEGF-A Splice Variant mRNA Expression With Outcome in Bevacizumab-Treated Patients With Metastatic Breast Cancer

BACKGROUND The prognostic utility of vascular endothelial growth factor A (VEGF-A) splice variants in patients with advanced breast cancer treated with bevacizumab has not been studied. PATIENTS AND METHODS A total of 111 patients with metastatic breast cancer treated with weekly docetaxel or ixabepilone without bevacizumab (cohort A) and 100 treated with weekly paclitaxel and bevacizumab (cohort B) were studied. Formalin-fixed tumors were macrodissected for reverse transcription quantitative polymerase chain reaction relative quantification of VEGF-A165, -189, and -206 isoforms spliced at exon 8 proximal splice site (VEGF-Axxxa) and at exon 8 distal splice site (VEGF-Axxxb). RESULTS For high VEGF-Axxxa, the hazard ratios (HRs) for progression were 1.08 (P = .71) in non-bevacizumab-treated patients (cohort A) and 0.66 (P = .22) in bevacizumab-treated patients (cohort B), and the HRs for death were 1.45 (P = .13) and 0.50 (P = .049), respectively. The interaction of VEGF-Axxxa with bevacizumab administration was significant (P = .011) for overall survival (OS). High tissue VEGF-Axxxb was not prognostic in cohort A but was predictive for bevacizumab benefit in cohort B (HR for progression, 0.57 [P = .04]; HR for death, 0.51 [P = .02]). Exploratory analyses done only in cohort B suggested that abundance of VEGFR1 messenger RNA (mRNA) in peripheral blood and low VEGFR2 mRNA in tissue correlated with poor outcome. In multivariate analysis, high tissue mRNA of angiogenic VEGF-Axxxa in the presence of bevacizumab therapy predicted for favorable progression-free survival (HR for progression, 0.39; P = .0227) and OS (HR for death, 0.32; P = .0140). CONCLUSION Tissue mRNA expression of angiogenic VEGF-Axxxa isoforms was retrospectively associated with adverse prognosis in the absence of bevacizumab and with favorable outcome when bevacizumab was administered in patients with advanced breast cancer.

Effect of Three Clinical Curing Treatments on Fluoride Release and Surface Hardness of Glass-Ionomer Cements

The purpose of this study was to investigate the effect of radiant heat, ultrasonic treatment, and 42.7 wt% CaCl₂ solution on fluoride release and surface hardness in three conventional glass-ionomer cements (GICs). The fluoride release patterns of each GIC were evaluated during a 28-day period using a fluoride ion-selective electrode. The surface hardness of the tested GICs was evaluated 24 hours after preparation of the specimens using Vickers hardness test. Statistical analysis of the data was made using analysis of variance and Bonferroni post hoc test (α = .05). Radiant heat, ultrasonic, and CaCl₂ solution treatments reduced fluoride release and increased the surface hardness of the tested GICs (P < .05). Among the tested GICs, differences in fluoride release and surface hardness were observed (P < .05). The clinical treatments investigated may be effective methods for improving the setting reaction of GICs and may achieve sufficient initial mechanical properties earlier. Although a reduction in fluoride release occurs after the treatments, anticariogenic properties of the GICs may not be significantly affected.

Effect of digluconate chlorhexidine on bond strength between dental adhesive systems and dentin: A systematic review.

Aim: This study aimed to systematically review the literature for the effect of digluconate chlorhexidine (CHX) on bond strength between dental adhesive systems and dentin of composite restorations. Materials and Methods: The electronic databases that were searched to identify manuscripts for inclusion were Medline via PubMed and Google search engine. The search strategies were computer search of the database and review of reference lists of the related articles. Search words/terms were as follows: (digluconate chlorhexidineFNx01) AND (dentinFNx01 OR adhesive systemFNx01 OR bond strengthFNx01). Results: Bond strength reduction after CHX treatments varied among the studies, ranging 0-84.9%. In most of the studies, pretreatment CHX exhibited lower bond strength reduction than the control experimental groups. Researchers who previously investigated the effect of CHX on the bond strength of dental adhesive systems on dentin have reported contrary results, which may be attributed to different experimental methods, different designs of the experiments, and different materials investigated. Conclusions: Further investigations, in particular clinical studies, would be necessary to clarify the effect of CHX on the longevity of dentin bonds.

The Effect of Composition, Temperature and Post-Irradiation Curing of Bulk Fill Resin Composites on Polymerization Efficiency

Objectives: To evaluate the polymerization efficiency of bulk fill resin-based composites (RBCs) and how their composition, temperature and post-irradiation polymerization influence the results. Methods and Materials: Eight bulk fill RBCs were investigated. Five specimens for each material were prepared for Vickers hardness measurements. The measurements were performed in three depths from the top of the surface of the specimens (0, 2 or 4 mm) immediately and 24 h after polymerization and for the highly viscous bulk fill RBCs after preheating at 54oC. Statistical analysis was performed using one-way ANOVA and Tukey post hoc tests ata=0.05. Results: As the depth increases microhardness values reduce. The Vickers hardness measurements 24 h after photo-polymerization revealed higher values compared to those obtained immediately after photo-polymerization(p<0.05). There was an increase in microhardness of the RBC materials when preheated at 54oC in comparison with the room temperature specimens (p<0.05). Conclusions: Polymerization efficiency of bulk fill RBCs is affected by their composition and increases with temperature and post-irradiation polymerization.

Effect of preheating and shade on surface microhardness of silorane-based composites.

AIM The aim of the present study was to evaluate the effect of preheating and shade on the surface microhardness of silorane-based composites. METHODS Three shades of two different types of composites were evaluated: a silorane-based composite and a methacrylate-based composite. The composites were tested at 23°C, and after preheating at 55°C. Five specimens were prepared for each experimental group. The top surface of the specimens was irradiated for 20 s using an LED unit. Vickers microhardness test was used to evaluate both top and bottom surfaces of the specimens, followed by 24-h storage in the dark. Statistical analysis was performed using one-way anova and Tukeys post-hoc test at a level of significance of α = 0.05. RESULTS There was a significant rise in microhardness as the temperature increased from 23 to 55°C for both the top and bottom surfaces of the tested composites (P < 0.05). The C2 shade of both composites exhibited the lowest microhardness (P < 0.05), while the A2 and A3 shades did not show significant differences compared to each other (P > 0.05) Filtek Silorane presented significantly lower microhardness than Filtek Z250 (P < 0.05), regardless of the temperature, shade, or depth of measurement. CONCLUSIONS Preheating, shade, and composition of the tested composite resins affected their surface microhardness.

Effect of Acidulated Phosphate Fluoride Gel on the Surface of Dental Nanocomposite Restorative Materials

The aim of this in vitro study was to investigate the changes in surface roughness of different nanocomposite restoratives and enamel after application of 1.23% acidulated phosphate fluoride (APF) gel. Twelve specimens were prepared for each composite material and human enamel. The APF gel was applied to the surface of the six specimens of each experimental group for 60 sec every 24 h for 4 days. The other six specimens did not receive APF treatment (control). The surface roughness was measured using a VSI microscope. One-way ANOVA and Tukey’s test were used to compare surface roughness between materials for each experimental group at a level of significance of a=0.05. There were no statistically significant differences in Ra values among the composites which did not receive APF treatment (p>0.05). After APF treatment the lowest surface roughness exhibited enamel (0.18±0.04 Ra) and the highest Dyract Extra (0.62±0.07 Ra) followed by Tetric EvoCeram (0.59±0.06 Ra) and Beautifil II (0.51±0.06 Ra). Filtek Z350 XT presented the lowest Ra values (0.23±0.03). All the experimental groups exhibited higher Ra values after APF treatment (p<0.05), except for Filtek Z350 XT (p>0.05). Application of APF gel on the specimen surfaces influenced the surface roughness of enamel and the tested dental composite restoratives depending on their composition.