# Peri-Implant Tissue Behaviour Next to Different Titanium Surfaces: 16-Year Post-Trial Follow-Up
## 4 Discussion
This outcome can be explained by a good compliance with home oral care recommendations, and also by local factors such as the presence of a sufficient keratinized mucosa [42; 43; 44], although the presence of keratinized mucosa was not specifically investigated in the present research. PI was considered satisfactory, even in those prostheses provided with resin composite used as aesthetic veneering material, which is known to be more plaque retentive than ceramic [45]. No statistically significant differences in bone resorption were found between implants rehabilitated with ceramic vs. composite resin veneering material as well. Despite the initial higher plaque accumulation around FOSS implants, the type of implant surface did not affect soft tissues health. In fact, BOP was absent at the majority of the implant sites and mean PD was within normal limits, with the greatest mean global PD value being 3.14 mm at the 5-year follow-up appointment, without statistically significant differences between the two implant types. These outcomes are consistent with the histological outcomes reported in the previously published study [26]. As described in a previous paper [2], in Group 2, mini-invasive samples of soft tissue surrounding implants were taken in order to evaluate microRNA (miRNA) expression at the implant sites by microarray analysis. Ninety-six miRNAs were found to be differently expressed next to FOSS and OSS implants indicating that peri-implant tissue reacts differently to the insertion of different implant types. In addition, peri-implant soft tissue inflammation appeared to be more related to miRNA expression than to plaque accumulation or to implant surface (machined vs. DAE). In particular, specific miRNA expression profiles were found that seemed to protect implant sites from inflammation (BOP) and bone resorption, irrespective of plaque accumulation, suggesting that individual host characteristics play a pivotal role in the behavior of peri-implant tissues. Many studies [46; 47; 48] suggested that rough surfaces promote osseointegration compared with smooth surfaces, thanks to their better osteogenic potential. Clinical studies showed that rough surfaces, when compared to turned/machined surfaces, could provide greater BIC and increased removal torque values [47]. This could be translated in shorter healing times from implant insertion to restoration. According to [PERSON] [49; 50] the implant surface design plays an important role in peri-implant endoscopes healing. In particular, microtopographically complex surfaces could potentiate the activation of platelets, which will produce cytokines and growth factors modulating osseointegration. These surfaces would also promote osteoporonduction by both increasing the available surface area for fibrin attachment and increasing the retention of the transient fibrin-based structural matrix of the blood clot through which osteogenic cells must migrate to reach the implant surface after implant insertion. It must be underlined that [PERSON] manuscripts focused on implants with dual acid-etched (DAE) surfaces compared with traditional machined surfaces such as in the study herein reported. In addition, another study supported that titanium surface topography and chemistry have a significant effect on platelet activation and chemokine release [51]. The implant surface also plays a role in the modulation of gene expression encoding for osteogenic activities on the osteoblasts [7]. However, it is still not clear which combination of different surface treatments induce a specific biological response and provide the best clinical behaviour [52]. Some authors found that implant with rough surfaces had greater success rates [53], while, in contrast, in a recent systematic review [PERSON] et al. [54] have reported significantly higher bone loss next to moderately rough and rough compared to minimally rough (i.e., machined or DAE) surfaces.