## Materials and Methods
### Synchrotron Radiation-Based Phase-Contrast Microtomography  
The microtomography experiment was performed at the SYRMEP beamline of the ELETTRA Synchrotron Facility (Basovizza, Italy); the following parameters were set: 1800 projections, each with 0.2 s exposure time, over a total range of 180\({}^{\circ}\); peak energy at \(\sim\)17 keV; sample-detector distance at 100 mm, achieving a pixel size of the projections of 890 nm. The high-resolution acquisition exploited the propagation-based phase-contrast setting, made possible by the coherence characteristics of the synchrotron beam. The refractive index n = 1 - \(\delta\) + i\(\beta\) was reconstructed, where the phase shift term \(\delta\) is related to the electron density of the tissues inside the sample, and \(\beta\) is proportional to the absorption index. The Paganin method [22] was used to retrieve the different phases (collagen, vessels, etc.), assuming a constant \(\delta/\beta\) ratio of 100.  
The next phase of image processing was the data elaboration: it was performed with the Dragonfly software (Pers. 2022.1; Object Research Systems, Montreal, QC, Canada) [23] and in particular with the deep learning tool, able to apply artificial intelligence to the segmentation process. Moreover, the open-source Fiji software [24] was used to perform a threshold image segmentation and the following extraction of quantitative morphometric parameters. In particular, the morphometric evaluation of the collagen bundles was calculated with the Bone plugin [25] of the Fiji software. It was performed by exploiting the structural indices usually measured in bone samples: collagen specific volume (expressed as a percentage), the degree of anisotropy and the connectivity density (expressed as pixel\({}^{-3}\)). The percentage volume is the amount of collagen tissue per unit of volume considered; the degree of anisotropy gives information on the directionality of the collagen bundles. The more anisotropic an object is, the more the parameter will tend from zero to  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Name** &
\begin{tabular}{c} **Time before** \\ **Retrieval** \\ \end{tabular} & **Immediately Loaded** & **Region** \\ \hline _Ctr1\_st\_wt_ & 6 weeks & YES & - \\ \hline _Ctr2\_lt\_no-wt_ & 10 years & NO & - \\ \hline _P1\_st\_no-wt_ & 6 weeks & NO & - \\ \hline _P12\_st\_no-wt\_r_ & 8 weeks & NO & right \\ \hline _P12\_st\_no-wt\_l_ & 8 weeks & NO & left \\ \hline \hline \end{tabular}
\end{table}
Table 1: Description of the investigated samples. _Ctr1_st_wt_: immediately loaded and retrieved after 6 weeks (_st:_ short time; _wt:_ immediately loaded). This specimen had already been studied [9; 12]. _Ctr2_lt_no-wt_: the abutment was inserted subgingivally, healed without loading for 6 months and then placed on the surface with the healing screw; the final prosthesis was made after another 3 months, with a total of 9 months before applying the masticatory load (_lt:_ long time; _no-wt:_ not immediately loaded). _P1\_st_no-wt:_ patient test 1—not loaded and retrieved after 6 weeks. _P12\_st_no-wt_l:_ patient test 2—not loaded and retrieved after 8 weeks. Right side of the jaw (_r_); _P12\_st_no-wt_l:_ patient test 2—not loaded and retrieved after 8 weeks. Left side of the jaw (_l_).  
one; the connectivity density quantifies how much collagen fibers are connected to each other, presenting an index of interlacing per unit of volume.