IADR Abstract Archives
Porosity in Conventional and High Viscosity Glass Ionomer Cements
Objectives: Recently, high-viscosity (HV) GICs have been advocated for ART restorations due to its improved mechanical properties. However, it is known that GIC properties may be influenced by the porosity of the material and these could influence longevity of restorations. The aim of the present study was to compare the porosity and pore size distribution of set HV (Ketac™ Molar, 3M ESPE and Vitro Molar, DFL) and conventional (Riva self-cure, SDI and Maxxion R, FGM) GICs obtained with a non-destructive micro-CT technique.
Methods: Sample size calculation was performed with a 1% significance level and 95% power, adding 20% to cover for possible sample loss, resulting in a final sample size of 10 specimens per group (N=40). Specimens were prepared according to ISO 9917-1 standards for water-based cements and after 24h of mixing they were scanned in a micro-CT (Skyscan 1173, Bruker) and reconstructed with standardized parameters. The volumes were digitally cropped into a 150-pixel radius cylinder and a 3D median filter (1-pixel kernel) was applied to reduce noise. After, all image stacks were histogram normalized. A binary threshold for pores was fixed at gray value 40. Total porosity, as well as the distribution of pore sizes was obtained for each specimen. Normality of data was checked with Shapiro-Wilk test and Kruskal-Wallis, followed by Student’s proof was used to detect differences in porosity among the groups.
Results: Ketac™ Molar showed statistically significant lower porosity (0.15%) than Vitro Molar (0.57%), Maxxion R (0.62%) and Riva self-cure (0.42%). Regarding pore size distribution, HV GICs showed higher percentage of large pores (8.8x10-3mm3; p<0.05) than conventional GICs while these and Ketac™ Molar showed higher numbers of small pores (Table 1, p<0.05). Figure shows 3D rendering images of representative specimens.
Conclusions: Ketac™ Molar showed the lowest total porosity, reinforcing its indication as a HV GIC of choice for ART restorations.
Methods: Sample size calculation was performed with a 1% significance level and 95% power, adding 20% to cover for possible sample loss, resulting in a final sample size of 10 specimens per group (N=40). Specimens were prepared according to ISO 9917-1 standards for water-based cements and after 24h of mixing they were scanned in a micro-CT (Skyscan 1173, Bruker) and reconstructed with standardized parameters. The volumes were digitally cropped into a 150-pixel radius cylinder and a 3D median filter (1-pixel kernel) was applied to reduce noise. After, all image stacks were histogram normalized. A binary threshold for pores was fixed at gray value 40. Total porosity, as well as the distribution of pore sizes was obtained for each specimen. Normality of data was checked with Shapiro-Wilk test and Kruskal-Wallis, followed by Student’s proof was used to detect differences in porosity among the groups.
Results: Ketac™ Molar showed statistically significant lower porosity (0.15%) than Vitro Molar (0.57%), Maxxion R (0.62%) and Riva self-cure (0.42%). Regarding pore size distribution, HV GICs showed higher percentage of large pores (8.8x10-3mm3; p<0.05) than conventional GICs while these and Ketac™ Molar showed higher numbers of small pores (Table 1, p<0.05). Figure shows 3D rendering images of representative specimens.
Conclusions: Ketac™ Molar showed the lowest total porosity, reinforcing its indication as a HV GIC of choice for ART restorations.
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