## 4 Discussion  
The present systematic review aimed to evaluate the biological effects of residual Al particles on dental implant surfaces compared to implants without such residues, and/or to different blasting materials, in animal models. The studies published so far on this topic encompass a range of experimental in vitro and in vivo, clinical, and review papers, providing a comprehensive overview of the current understanding of this issue. The studies indicate that residual Al particles on dental implant surfaces do not significantly impair osseointegration or biocompatibility. For instance, [PERSON] et al. [15] found no statistically significant differences in osseointegration between implants with and without residual Al particles in an experimental rabbit model. Similarly, [PERSON] et al. [26] observed no adverse effects from Al ions on implant surfaces in both in vitro and in vivo studies. Interestingly, some studies suggest potential benefits associated with residual Al particles. [PERSON] et al., 2022 [20] reported that implants with residual Al particles demonstrated accelerated bone growth and reduced bacterial adhesion compared to cleaned implants. This finding aligns with the hypothesis that the physicochemical properties imparted by residual Al particles may enhance specific biological responses. The cleanliness of dental implant surfaces is a critical factor for successful osseointegration. The reviewed literature highlights the importance of controlling surface contamination during the manufacturing process. For instance, [PERSON] et al., 2010 [24] showed that removing residual Al particles resulted in increased bone-implant contact, although it also reduced shear resistance. Bone-implant contact (BIC) is defined as the percentage of implant surface that is in contact with newly formed bone. The BIC estimates the ability of a surface to induce bone formation around implants, and it is measured histologically and is related to implant surface roughness [27]. The association between surface roughness and osseointegration is well known [4]. A rough implant surface may be considered as a series of pits (peaks) and valleys, with different density (number per area), height, and sharpness [27]. Some biomechanical studies in the past observed that there is a range of pit size (normally in the micrometer range) and density that is related to high shear strength [28]. Within this range, when increasing the pit density, the shear strength increases, while below or above this range, a decrease in mechanical retention is observed. The presence of alumina may further increase the surface roughness, which can contribute to improving mechanical implant-bone interlocking. Several studies also found a correlation between BIC and the mechanical stability of implants [29; 30]. These findings suggest that while surface cleanliness is desirable, residual Al particles may not necessarily be detrimental to implant osseointegration and could potentially offer some benefits. The use of alternative blasting materials, such as titanium dioxide (TiO\({}_{2}\)), has been explored to avoid potential issues associated with Al particles. [PERSON] et al., 2018 [22] compared the effects of Al\({}_{2}\)O\({}_{3}\) and TiO\({}_{2}\) microparticles and found no significant differences in osseointegration between the two materials. This suggests that TiO\({}_{2}\) could be a viable alternative to Al for implant surface modification, potentially eliminating concerns related to residual Al. Other studies found that blasting the implant surface with Al\({}_{2}\)O\({}_{3}\) produces better surface features (free energy, roughness, microhardness, residual stresses, and fatigue), as well as faster osseointegration and greater bone-to-implant contact, compared to surfaces blasted with TiO\({}_{2}\)[19; 20]. From a clinical perspective, the SLA surface on dental implants does not appear to pose a significant risk to osseointegration or patient health.