All maxillary samples of the sheep were covered with Parafilm and scanned using Skyscan 1176 microtomography scanner (Bruker, Kontich, Belgium). MicroCT scanning was performed at a resolution of 18 µm with the following parameters: 90 kV, 278 µA, 0.5-mm aluminum filter, and 360-degree rotation range. All acquired images were reconstructed by using NRecon software (version 1.6.10.4; Bruker) with a Gaussian smoothing of 3, beam hardening correction of 40%, and ring artefact reduction of 12. DataViewer (version 1.5.2.4 64-bit; Bruker) was used to reorient the direction of the reconstructed images to the sagittal plane. Subsequently, all images were imported into CTAn software (version 1.15.4.0+; Bruker) for bone microstructural analysis.
The furcation areas enclosed by the buccal and lingual roots of premolars were defined as the region of interest (ROI) (Figure 1A ). After selection of the ROIs, the automatic (Otsu method) threshold was applied for all images during the analysis. The bone microstructure parameters are presented in Table 1 . Since the left and right sides were pooled together, the total number of samples was 36 and every group contained 6 samples taken after 4 and 12 weeks of retention.
The furcation areas enclosed by the buccal and lingual roots of premolars were defined as the region of interest (ROI) (