Examination of the effect of aging process on marginal fit and fractute strength of temporary crowns prepared from different materials.

Aim: The aim of this study is to investigate the effect of the aging process on the marginal fit and fracture resistance of temporary crowns prepared using different materials. Materials and method: The steel die to represent the maxillary first premolar used in this study was produced on a CNC turning machine to include an anatomical occlusal surface. A total of 160 epoxy resin dies were obtained by taking impressions with conventional impression methods on the metal die. Epoxy resin dies were randomly divided into four groups. Temporary crowns were prepared for each group from poly acrylic resin (Vita CADTemp®), bis-acryl composite resin (Protemp 4), poly methyl methacrylate (PMMA; Imident) and poly ethyl methacrylate (PEMA; Dentalon Plus) restorative materials. Half of the specimens (n = 20) in each group (n = 40) were randomly separated and the aging process was applied 5000 times in the device. Marginal gap measurements on epoxy resin dies were made using a stereomicroscope. The fracture strength test of the specimens was performed by using the Instron Universal Test Device. Jamovi 2.2.5 statistical program was used for statistical analysis. Results: When compared to temporary crowns prepared from all other materials, poly acrylic resin (Vita CADTemp ®) temporary crowns observed significantly lower marginal gap values (59,05 µm) regardless of the aging process, and a significantly higher fracture resistance (478,44 N) in the presence of aging process (p < .05 for each). While the highest marginal gap value was detected in PMMA (Imident) (120.36 µm) temporary crowns with aging process, the lowest marginal gap value was observed in poly acrylic resin (Vita CADTemp®) (59.05 µm) crowns without non-aging process. The marginal fit and fracture resistance of all temporary crowns were negatively affected by the aging process. Conclusion: Our findings revealed the superiority of poly acrylic resin (Vita CADTemp®) crowns to the temporary crowns prepared from all other materials in terms of the significantly lower marginal gap in the absence of aging process, and the significantly higher fracture resistance in the presence of aging process. Marginal fit and fracture resistance values for all materials were found to be within clinically acceptable limits.

The fungal metabolite chaetocin is a sensitizer for pro-apoptotic therapies in glioblastoma.

Glioblastoma Multiforme (GBM) is the most common and aggressive primary brain tumor. Despite recent developments in surgery, chemo- and radio-therapy, a currently poor prognosis of GBM patients highlights an urgent need for novel treatment strategies. TRAIL (TNF Related Apoptosis Inducing Ligand) is a potent anti-cancer agent that can induce apoptosis selectively in cancer cells. GBM cells frequently develop resistance to TRAIL which renders clinical application of TRAIL therapeutics inefficient. In this study, we undertook a chemical screening approach using a library of epigenetic modifier drugs to identify compounds that could augment TRAIL response. We identified the fungal metabolite chaetocin, an inhibitor of histone methyl transferase SUV39H1, as a novel TRAIL sensitizer. Combining low subtoxic doses of chaetocin and TRAIL resulted in very potent and rapid apoptosis of GBM cells. Chaetocin also effectively sensitized GBM cells to further pro-apoptotic agents, such as FasL and BH3 mimetics. Chaetocin mediated apoptosis sensitization was achieved through ROS generation and consequent DNA damage induction that involved P53 activity. Chaetocin induced transcriptomic changes showed induction of antioxidant defense mechanisms and DNA damage response pathways. Heme Oxygenase 1 (HMOX1) was among the top upregulated genes, whose induction was ROS-dependent and HMOX1 depletion enhanced chaetocin mediated TRAIL sensitization. Finally, chaetocin and TRAIL combination treatment revealed efficacy in vivo. Taken together, our results provide a novel role for chaetocin as an apoptosis priming agent and its combination with pro-apoptotic therapies might offer new therapeutic approaches for GBMs.

Pre-eruptive coronal resorption and congenitally missing teeth in a patient with amelogenesis imperfecta: a case report.

This clinical report describes a male with autosomal recessive generalized hypoplastic amelogenesis imperfecta. This case is unusual in coronal resorptions prior to tooth eruption. This finding has been reported in some cases of autosomal recessive, autosomal dominant and X linked amelogenesis imperfecta (AI). In reported cases, the defects were usually small and occurred in a maximum of 2 teeth per person. In our case, pre-eruptive coronal resorptions affected three second molar teeth from both jaws. On the other hand; congenitally missing teeth and malocclusion were present in this case. Recall evaluations at 3 month intervals occurred for a period of 2 years and then prosthodontic management began.

Evaluation of the wear resistance of new nanocomposite resin restorative materials.

STATEMENT OF PROBLEM: The use of composite resins for the restoration of posterior teeth is popular because of the improved performance and appearance of these materials. Wear resistance continues to be of particular importance when restoring large occlusal areas in posterior teeth. PURPOSE: The purpose of this study was to evaluate the relative wear characteristics of 2 recently introduced nanofiller-based composite resins (Filtek Supreme, Premise) and compare them to the more traditional microhybrid (Point 4) and microfill (Heliomolar RO) materials that have been used for many years. MATERIAL AND METHODS: Six specimens (2 mm thick and 15 mm in diameter) of each material were subjected to 3-body wear tests using the Oregon Health Sciences University Oral Wear Simulator to produce abrasive wear and attrition for all specimens using human enamel as the opposing cusp. Profilometric tracings of the worn surfaces were used to determine the relative abrasive wear, attrition wear, and roughness (Ra) of the composite resin substrate. The mean diameter of the antagonist enamel wear facets was determined under a measuring microscope. Qualitative SEM analysis was also used to assess the surface appearance of the resulting enamel and composite resin wear facets. The data were analyzed by 1-way ANOVA and Tukey's multiple range post hoc test (alpha=.05). RESULTS: The results indicated that the composite resin type did not significantly affect the amount of measured attrition (P=.15) but did significantly affect abrasive wear (P=.02). The conventional microfill composite resin (Heliomolar RO) exhibited significantly less abrasive wear than the nanohybrid material (Premise). There was no significant difference in the average size of the opposing enamel wear facet generated by the different composite resin materials. Heliomolar RO resulted in a significantly rougher surface within the wear track than either nanohybrid composite resin (Premise) or microhybrid composite resin (Point 4) but was not significantly different than nanofilled composite resin (Filtek Supreme). CONCLUSIONS: The incorporation of nanofillers in 2 of the composite resin materials tested did not significantly improve their wear resistance or the amount of opposing cusp wear when compared to the traditional materials tested.

Microleakage of four core materials under complete cast crowns.

This study evaluated the microleakage patterns of complete cast-metal crowns cemented onto teeth that were rebuilt with pin-retained cores made from cast metal, composite resin, acrylic resin and amalgam by using four different cements. One hundred extracted human teeth were used to compare the microleakage of composite resin core, metal core, acrylic resin core and amalgam core, and regular crown preparations under a complete cast metal crown cemented with different cements as determined by 2% methylene blue dye solution. Specimens were compared with and without aging after cementation in a thermal bath by cycling some of them between 4 degrees C and 50 degrees C in a 2% methylene blue bath and others in a similar bath held at 37 degrees C. The extent of marginal microleakage was evaluated with a stereomicroscope and scored. It was determined through variance analysis that the type of core used in the substructure, the cement used for cementing and the thermocycling process were all important in microleakage. No significant differences in the degree of microleakage were found under crowns cemented onto teeth rebuilt with the four core materials when cemented with the same luting cement.

Effect of different surfaces and surface applications on bonding strength of porcelain repair material.

This study was done to analyze the effect of different surfaces and different surface applications on the bonding strength of porcelain repair material and to compare these factors with one another. Three different substructures of 10 mm diameter and 4 mm thickness were used for the repair surface: metal, metal on porcelain and porcelain. The surfaces of half of the samples were roughened with an air abrasion tool; the surfaces of the other half were treated with a diamond bur. The specimens were ultrasonically cleaned in distilled water. A silane coupling agent and a bonding agent were applied to the surfaces of all the samples. Resin composite was applied to each specimen. All specimens were stored in distilled water for 24 hours before being thermocycled. After thermocycling, specimens were stored in distilled water for an additional seven days before being subjected to a shear load. The highest bonding strength was observed in the samples with a metal substructure, the surfaces of which were prepared with an air abrasion tool; the lowest bonding strength was observed in the samples with a metal substructure, the surfaces of which were prepared with a diamond bur. When different substructures were examined in terms of bonding strength, the highest bonding strength was statistically observed in metal-on-porcelain substructures, and the lowest bonding strength was observed in the porcelain substructure. When they were examined in terms of surface processes, the highest bonding strength was statistically observed in the samples whose surfaces were prepared with an air abrasion tool, and the lowest bonding strength was observed in the samples whose surfaces were prepared with a diamond bur.