## 4 Discussion  
This 6 month histological and histomorphometric prospective cohort study evaluated the quality and quantity of bone after a ridge preservation procedure using a hardening biphasic calcium phosphate (\(\beta\)-TCP/HA) and a bioresorbable matrix barrier. The histological analysis of the biopsies showed newly formed trabecular bone, a moderately well-vascularized inflamed connective tissue, and residual graft particles after six months after graft procedure. This indicated an appropriate healing, with particles embedded into newly formed bone, showing slight signs of resorption and high biocompatibility of the material without significant inflammatory response. Moreover, other authors in histological studies on humans did not find evidence of inflammatory infiltrate, necrosis, foreign body reaction, or other signs of adverse reaction in case of use of the B-TCP/HA for the treatment of bone defects [23]. The histological human results obtained in the present study were in agreement with the histological observations described in the study conducted by [PERSON] et al. [21]. Indeed, after 5 months of healing, the authors reported that the Beta-TCP/HA granules were still present, and they were in contact with active osteoblasts forming osteoid matrix and newly formed bone; this could demonstrate \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Patient** & **\%NB** & **\%ST** & **\%P** \\ \hline
1 & 43.4 & 35.1 & 21.5 \\
2 & 41.8 & 34.5 & 23.8 \\
3 & 35.9 & 55.4 & 8.7 \\
4 & 31.0 & 51.2 & 16.8 \\
5 & 16.2 & 55.5 & 28.3 \\
6 & 20.3 & 47.4 & 32.4 \\
7 & 23.3 & 56.3 & 20.3 \\
8 & 23.5 & 41.5 & 35.0 \\
9 & 32.1 & 39.4 & 28.4 \\
10 & 22.7 & 72.9 & 5.4 \\ \hline
**MEAN** & **29.0** & **48.9** & **22.0** \\
**SD** & **9.3** & **11.9** & **9.7** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Histomorphometric outcomes: percentages of newly formed bone (NB), percentages of soft tissue (ST), percentages of biomaterial graft particles (P). Mean value (Mean) and standard deviation (SD) at six-month follow-up were reported. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Outcomes** & \(\Delta\)**T0-T1** & **\%T0-T1** \\ \hline
**AHB 1** & \(-0.5\pm 1.0\) * & 7.4\% * \\
**AVB 2** & \(-0.9\pm 1.3\) * & 14.8\% * \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Dimensional tissue changes at T0 (ridge preservation procedure) and T1 (six months follow-up). Mean value and standard deviation were expressed in millimeter. Percentage (%) of bone loss between initial and re-entry values was reported. an osteogenicic property. Similarly, in the present histological study, the presence of mineralized bone and rims of osteoblasts in contact with the residual particles were observed, therefore, showing that bone formation activity was still in progress. Surface topography can be a crucial role in the osteeconductive properties of the biomaterials, as it was demonstrated in in vitro studies where the topography and chemistry properties of a substrate had a very important effect on the stem cell characterization or differentiation [24; 25; 26]. Moreover, in a histological study on rabbits, three hydroxyapatite-based biomaterials with different physical and topographical characteristics showed different quantities of new bone formation when the biomaterials were implanted in bone regenerated sites [27]. A long-term histological study, performed on experimental animals, has shown that \(\beta\)-TCP biomaterial was osteeconductive until degradation, acting as a scaffold to support newly formed bone [18]. Calcium phosphates, such as \(\beta\)-TCP or hydroxyapatite (HA) or a mixture of both, have demonstrated in previous studies to be a highly performing bone substitute with all the characteristics of an ideal biomaterial: good biocompatibility and osteoconduction proprieties, easy to shape and to manipulate, safe, and bioresorbable [19].