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Background This study investigated the effect of preheating of bulk-fill BIS-GMA free and containing resin composite on post-gel shrinkage strain. In a split Teflon mold, sixty resin composite specimens were prepared with dimensions 7 mm length × 4 mm width × 4 mm height. Thirty specimens of each tested restorative materials were prepared, ten specimens for each selected temperature used in the study (room temperature 23 °C, 50 °C and 65 °C). The resin composite was monitored for post-gel shrinkage strain for 3 min after light irradiation using strain gauges. For pairwise comparisons, Duncan’s multiple range test was used to analyze the data after two-way ANOVA. The p ≤ 0.05 significance level was chosen. Results Viscalor thermoviscous bulk-fill composite Bis-GMA containing had the lowest polymerization shrinkage strain values in the three different temperatures. There was a statistically significant difference between groups according to material used at different temperatures. Both tested materials showed the highest shrinkage strain when preheated at 65 °C. Conclusions While the technology of thermoviscous is introduced to deliver the viscosity of a flowable resin composite so reducing the polymerization strain, it actually had adverse effect on it. Preheating of bulk-fill BIS-GMA free resin composite either to 50 °C or 65 °C had no effect on decreasing the polymerization shrinkage strain. Polymerization shrinkage strain of bulk-fill BIS-GMA contains resin composite either without or with preheating far superior to that of BIS-GMA free resin composite.

Aim: This study aimed to compare the fracture resistance of root canal treated (RCT) teeth restored with different types of resin composite restorations.Methods: A total of 40 freshly extracted human intact mature permanent maxillary premolars were selected and randomly assigned into 4 groups (n = 10 each); the EXF group in which teeth were RCT and restored with a fiber-reinforced bulk-fill flowable composite (Ever-X flow) and covered with a nanofilled resin composite (Filtek Z 350), the RBF group in which teeth restored with polyethelene fibers (Ribbond) with a bulk-fill flowable composite (Filtek bulk-fill flow) covered with the same nanofilled composite, the FBF group in which teeth restored with a bulk-fill flowable composite without fiber reinforcement (Filtek bulk-fill flow) also covered with the same nanofilled composite and the control group in which teeth remained intact without any preparation. All teeth were subjected to a thermo-mechanical cycling after which a static fracture test was performed using the universal testing machine to record the load at failure. Results:The significantly higher mean value of fracture resistance was recorded in the control group than other experimental groups (P < .05). The EXF group showed the highest and followed by RBF group, and the lowest mean value was found in FBF group (P < .05). Conclusion:Within the limitation of the present study, either short fiber-reinforced composite and polyethylene fiber-reinforced composite may have superior resistance to fracture and could reinforce RCT teeth compared to nanofilled composite without fiber reinforcement.

Aim: Evaluation of shear bond strength of a new self adhesive resin composite restorative material. Materials and methods:A total of 30 freshly extracted human intact molars were selected. All teeth are mounted in acrylic blocks, The occlusal surfaces of all selected molars were grinded at a level just below the dentino-enamel junction (DEJ). The prepared 30 molar divided into three groups of ten specimens each (n=10). The first group SR1 (Surefil one composite without adhesive application), the second group SR2 (Surefil one composite with adhesive application), and the third group FL (Filtek One Bulk Fill Restorative with adhesive application). Split teflon mold has dimensions of (6 mm width-4 mm height) was used to obtain disks of the tested materials, by placing the mold on the prepared dentin surface and each material applied inside the mold. After cyclic loading fatigue using Robota chewing simulator, shear bond strength of every specimen was measured using Universal testing machine. One-way ANOVA followed by Tukey post hoc test was used to compare between the different groups.Results: There was a statistically significant difference between (SR1) and both of (SR2) and (FL) groups, where ((P < .05). While there was no statistically significant difference between (SR2) and (Fl) groups.Conclusion: (Surefil one) without adhesive application has limited shear bond strength than other tested groups. Adhesive application improved the shear bond strength of (Surefil one) self adhesive composite.

Background Preheating is one of several innovative approaches and improvements developed to increase the durability and clinical behavior of resin composites. Development of preheated composites is to reduce its viscosity in order to improve resin composite adaptation and placement ease. The purpose of this clinical trial was to study the effect of preheating Bis-GMA free and Bis-GMA-containing resin composites at different temperatures on the pulpal floor and restoration temperature. A total of twenty individuals (N = 40) have two carious posterior teeth that need to be restored were randomly assigned to one of two groups based on the type of restorative materials used: (group 1) Bis-GMA-containing resin composite VisCalor bulk (VCB), and (group 2) Bis-GMA-free resin composite Admira Fusion x-tra (AFX). Preheating temperatures of 50 °C and 70 °C were utilized to separate each group into two subgroups. Class I or II cavities were prepared. Thermometer device with two separate K-type temperature probes was used to measure the base line temperature values at the pulpal floor before beginning the restorative procedure (C0), pulpal floor during packing of preheated composite (C1), the top composite surface after packing and before curing (C2), pulpal floor after curing of the preheated composite (C3), and top composite surface after curing (C4). One-way ANOVA and the Kruskal–Wallis test were used to analyze the data. Results The measured temperature of pulpal floor for both preheated VCB or AFX at 50 °C or 70 °C revealed significant increasing from base line measured temperature to during packing as well as after curing with (P-value < 0.001). There was no significant difference for mean composite surface temperature for both preheated materials at 50 °C or 70 °C whether before or after curing. Conclusions Preheating of bulk fill Bis-GMA free and containing resin composite rises both the pulpal floor and the restoration temperature; meanwhile, the rise in temperature was limited. The application of the curing unit caused the greatest temperature rise.