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Objectives: This study was designed to evaluate the effect of natural cross linkers (Propolis and Hesperidin) on shear bond strength (SBS) to dentin after storage in different media. Materials and Methods: Ninety extracted molars were used and divided into three main groups according to dentin surface treatment (n=30) where, A1: treated with Propolis, A2: treated with Hesperidin and A3: receive no treatment to serve as a control group. Each group was further subdivided into 3 subgroups (n=10) according to the storage media either stored in Acids (B1) or stored in Artificial saliva (B2) or stored in distilled Water (B3). The shear bond strength (SBS) was determined using a universal testing machine. Results: The dentin specimens treated with Propolis showed significantly highest SBS. Conclusion: Both Propolis and Hesperidin cross linking agents are considered beneficial in improving bonding to dentin, though Propolis was much more effective. Storage media has deteriorating effect on resin-dentin shear bond strength.

Purpose: To evaluate the effect of Actilux-activated whitening toothpaste and Marine salts powder on color change and microhardness of bovine enamel. Methods: Thirty intact bovine incisors were used in this study to produce enamel specimens. The specimens were randomly distributed into three groups (n= 10) according to the tested whitening agents as follows: Group I: BW; BlanX LED White Shock (Actiluxactivated), Group II: MS; Marine salts whitening powder and Group III: CR; Crest regular fluoridated toothpaste. The specimens were stained using black tea solution for 5 days. Each specimen was brushed twice daily for 8 then 15 days. The color was assessed according to CIE (Lab) color system using a VITA Easyshade spectrophotometer. The microhardness was assessed using Digital Display Vickers Microhardness Tester at baseline, after staining, after 8 days, and 15 days brushing. Data were tabulated and statistically analyzed. Results: After 8 days brushing, BW showed the highest mean (ΔE) while MS and CR both showed lower mean (ΔE). BW and MS showed the highest mean (ΔE) after 15 days brushing with no statistically significant difference between them. After 15 days; BW showed the highest mean microhardness followed by MS while CR showed the lowest mean microhardness. Conclusion: Both Actiluxactivated toothpaste combined with LED device and Marine salts powder were effective in tooth whitening as well as increasing enamel microhardness. The whitening efficacy and microhardness is time dependent.

Objective: This research was conducted to investigate the effect of chemical challenge on the compressive strength (CS) and surface roughness (Ra) of a ceramic reinforced glass ionomer in comparison to a nanofilled resin composite.Methods: A total of 60 disc specimens (6mm height x 4mm diameter) were prepared for the compressive strength testing and another 60 disc specimens (5mm diameter x 2mm thickness) for the surface roughness testing. Specimens were divided into 2 groups (n=30) according to the material used; ceramic reinforced glass ionomer (Amalgomer CR, Advanced Health Care Ltd, Tonbridge, Kent, UK) and nanofilled resin composite (Filtek TM Z350 XT, 3M ESPE, St.Paul, MN,USA). Each group was divided into 3 subgroups (n=10) according to the storage media; distilled water (control), 0.02N citric acid and 50% ethanol. Specimens were stored for 7 days at 37ºC. After storage period, they were subjected to compressive loading using a universal testing machine and surface roughness testing using white light interferometer. Data were tabulated and statistically analyzed using Two-way ANOVA followed by Bonferroni's post-hoc test.Results: Amalgomer CR recorded a significantly lower CS and higher Ra than nanofilled resin composite under different storage media. Citric acid revealed the lowest CS of Amalgomer CR followed by ethanol in comparison to distilled water with significant difference between them. For nanofilled resin composite, both citric acid and ethanol significantly decreased CS. Ethanol showed the highest Ra values for both restorative materials. Conclusions:The performance of Amalgomer CR under different storage media was inferior to nanofilled resin composite regarding compressive strength and surface roughness. Citric acid severely affected compressive strength of Amalgomer CR. Nanofilled resin composite was able to preserve its surface roughness within the clinically acceptable threshold after chemical challenge in contrary to Amalgomer CR.