## 3 Results
The same superscript lettership no statistical difference (\(p>0.05\)) between the absolute values of OPV and CPV (a) and their **relative values** (b). * \({}^{8}\)**Legend:** SEM—standard error of the mean, CI—confidence interval, SD—standard deviation, Min and Max—minimum and maximum values. The same superscript lettership no statistical difference (\(p>0.05\)) between the absolute values of OPV and CPV (a) and their **relative values** (b). * \({}^{9}\)**Legend:** SEM—standard error of the mean, CI—confidence interval, SD—standard deviation, Min and Max—minimum and maximum values. The same superscript lettership no statistical difference (\(p>0.05\)) between the absolute values of OPV and CPV (a) and their **relative values** (b). * \({}^{10}\)**Legend:** SEM—standard error of the mean, CI—confidence interval, SD—standard deviation, Min and Max—minimum and maximum values. The same superscript lettership no statistical difference (\(p>0.05\)) between the absolute values of OPV and CPV (a) and their **relative values** (b). * \({}^{11}\)**Legend:** SEM—standard error of the mean, CI—confidence interval, SD—standard deviation, Min and Max—minimum and maximum values. The same superscript lettership no statistical difference (\(p>0.05\)) between the absolute values of OPV and CPV (a) and their **relative values** (b). Figure 1: Distribution of TPV% (OPV% + CPV%) of Harvard MTA in the sample per specimen. Figure 2: Representative micro-CT cross sections showing the root-end filling of Harvard MTA at 2 mm from the apex in three planes: (**a**) coronal (X–Z); (**b**) transversal (X–Y); and (**c**) sagittal (Z–Y) (scale bar = 1 mm). Figure 4: (**a**–**c**) Binary images of material transversal cross sections at the same levels as above (d \(\approx\) 1 mm), displaying the porosity distribution in the VOI (pores black, material white) and highlighting the voids between radicular dentin and Harvard MTA. Figure 5: (**a**,**b**) Interfacial gap observed in one of the specimens’ transversal cross sections. Figure 3: Micro-CT images of the filling material in transversal plane (d \(\approx\) 1 mm) at different levels: (**a**) at 3 mm (approximately) from the resected apex; (**b**) at 2 mm; (**c**) at 1 mm. The following results represent the mean absolute and relative values of the porosity characteristics found with Harvard MTA when applied as root-end filling material:  
* **OPV** (or interfacial gaps and pores volume) was measured at 0.0268 \(\pm\) 0.0087 mm\({}^{3}\), which represented 0.91% as a relative value;
* **CPV** (or internal pores volume): 0.0283 \(\pm\) 0.0114 mm\({}^{3}\) or 0.94% of the mean retrofilling volume;
* **TPV**, or cumulative volume of gaps and voids in the tested cement, was calculated at 0.0569 \(\pm\) 0.0163 mm\({}^{3}\) or 1.85% of the mean retrocavity volume;
* The average **pore size** (as diameter) was 4.383 \(\pm\) 2.061 \(\upmu\)m.  
The pair-wise comparisons between both estimated porosity aspects **showed no significant difference** between the following pairs: _OPV_ vs. _CPV_ (_p_ > 0.05) and _OPV_% vs. _CPV_% (_p_ > 0.05). More specifically, the paired sample t-test findings for both pairs were as follows:  
* **OPV** vs. CPV (**a**): t = \(-\)0.413, df = 9, \(p\) = 0.689;
* **OPV**% vs. CPV% (**b**): t = \(-\)0.263, df = 9, \(p\) = 0.798. Furthermore, the descriptive statistics for the measured parameters revealed low standard deviations and somewhat narrow confidence intervals, indicating that the data are slightly dispersed relative to the mean values. The minimum and maximum values of OPV vs. CPV in volumetric units (mm\({}^{3}\)) and as percentages are also very close: Min in absolute values (mm\({}^{3}\)) were 0.0152 mm\({}^{3}\) vs. 0.0124 mm\({}^{3}\), and 0.54% vs. 0.49% in relative values, respectively; likewise, Max were 0.0448 mm\({}^{3}\) vs. 0.0438 mm\({}^{3}\), respectively; and maximum relative values for both parameters were found to be identical (1.48%).