OBJECTIVES: Comparisons of material hardness may be affected by the indentation size effect (ISE), which is characterized by increasing hardness values at decreasing loads. This study aimed to assess the influence of load, dwell time and measurement method on ISE in dental resin-based composites with different filler content. METHODS: Knoop (HK) and Vickers (HV) microindentation hardness of Filtek Ultimate Universal Restorative (FU) and Filtek Supreme Flowable Restorative (FF) was measured under different loads (0.098-2.96 N, i.e. 10-300 gf) and dwell times (5-30 s). Their effects on HK and HV were evaluated using repeated measures ANOVA, which was also used to compare the measurement methods. Coefficients of Meyer's equation, proportional specimen resistance (PSR) model and a modified PSR model were calculated using regression analyses. RESULTS: ISE was more pronounced for the highly-filled FU than for the less-filled FF, and HK was more susceptible to ISE than HV. The effect of dwell time was similar for both materials and measurement methods; hardness values decreased with dwell time, significantly between 5 s and 30 s. SIGNIFICANCE: The possible presence of ISE should be considered when determining measurement conditions for the microindentation hardness of dental resin-based composites. HV was found to be less sensitive to ISE and provided stable hardness values at lower loads than HK. Due to the high variability of composites, any hardness measurement should be preceded by mapping the effect of load to ensure that load-independent hardness is measured. If hardness values continue to decrease in the whole range of increasing loads, load-independent hardness can be calculated using the PSR model.

• Klíčová slova
• Dwell time, Load, Microhardness, Microindentation, PSR model, Resin composite,
• MeSH
• složené pryskyřice * chemie   MeSH
• testování materiálů * MeSH
• testy tvrdosti MeSH
• tvrdost * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• složené pryskyřice * MeSH

This study investigated the effect of peroxide bleaching gel on the durability of the adhesive bond between composite material, enamel, and dentin created with the etch-and-rinse adhesive Gluma Comfort Bond (GLU) and with the self-etch adhesives Clearfil SE Bond (CLE), Adper Prompt (ADP), and iBond (IBO). The adhesives were applied to flattened enamel and dentin of extracted human molars and built up with a microhybrid composite (Charisma). After 25 eight-hour cycles of bleaching with a 20% carbamide peroxide bleaching gel (Opalescence PF 20), the shear bond strength was measured and compared with one-day and two-month control specimens stored in water. The data were analyzed using nonparametric Mann-Whitney and Kruskal-Wallis statistics (p<0.05). Detailed fractographic analysis was performed using scanning electron microscopy. The bleaching gel significantly decreased the bond strength on both enamel and dentin for the simplified single-step self-etch adhesives ADP and IBO and markedly affected a fracture pattern of ADP specimens at the periphery of their bonded area. The results of our study indicate that the durability of adhesive restorations can be detrimentally influenced by carbamide peroxide bleaching and that different adhesives show varying sensitivity levels to the bleaching gel.

• MeSH
• bělení zubů metody   MeSH
• bisfenol A-glycidyl methakrylát chemie   MeSH
• časové faktory MeSH
• dentin ultrastruktura   MeSH
• dentinová adheziva chemie   MeSH
• karbamidperoxid MeSH
• látky na bělení zubů chemie   MeSH
• leptání zubů kyselinou metody   MeSH
• lidé MeSH
• mechanický stres MeSH
• mikroskopie elektronová rastrovací MeSH
• močovina analogy a deriváty   chemie   MeSH
• organofosfáty chemie   MeSH
• peroxidy chemie   MeSH
• pevnost ve smyku MeSH
• povrchové vlastnosti MeSH
• pryskyřičné cementy chemie   MeSH
• složené pryskyřice chemie   MeSH
• testování materiálů MeSH
• vazba zubní * MeSH
• voda chemie   MeSH
• zubní materiály chemie   MeSH
• zubní sklovina ultrastruktura   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• randomizované kontrolované studie MeSH
• srovnávací studie MeSH
• Názvy látek
• Adper Prompt Self-Etch MeSH Prohlížeč
• bisfenol A-glycidyl methakrylát MeSH
• Charisma composite resin MeSH Prohlížeč
• Clearfil SE Bond MeSH Prohlížeč
• dentinová adheziva MeSH
• Gluma Comfort Bond MeSH Prohlížeč
• iBond MeSH Prohlížeč
• karbamidperoxid MeSH
• látky na bělení zubů MeSH
• močovina MeSH
• organofosfáty MeSH
• peroxidy MeSH
• pryskyřičné cementy MeSH
• složené pryskyřice MeSH
• voda MeSH
• zubní materiály MeSH