## 4 Discussion
Furthermore, both Biorepair Plus Parodontgel and Biorepair Peribioma PRO contain ococpheryl acetate (vitamin E), an antioxidant agent whose positive role in periodontitis has been suggested but little studied until now. In particular, experiments conducted in rats suggest that vitamin E supplements prevent oxidative stress related to periodontitis; however, the potential for the treatment of human periodontal disease still remains uncertain because decreases in alveolar bone loss have not always been observed [23]. The most interesting results obtained in the present report are certainly the ones related to Biorepair Peribioma PRO toothpaste, which was the most effective in reducing FMBS. In addition to that, this product significantly reduced BoP index with no intergroup differences with respect to Biorepair Plus Parodontgel, except at the 6-month evaluation. In fact, in the current study, Biorepair Peribioma PRO was the only product causing not only an immediate positive effect between T\({}_{0}\) and T\({}_{1}\) but also a further delayed benefit assessed after a 6-month follow-up. No other intragroup differences between T\({}_{1}\) and T\({}_{3}\) were assessed for the other pastes tested. Biorepair Peribioma PRO was the only paraprobiotics-based toothpaste tested in this study, specifically containing heat-inactivated bacteria (tyndallization) of the genus _Lactobacillus_ and _Bifidobacterium_. Among the 'biotic' compounds, one of the most important categories is represented by probiotics. These are defined by the Food and Agriculture Organnization (FAO) and the World Health Organization (WHO) as 'live microorganisms which when administered in adequate amounts confer a health benefit on the host' [24]. Several mechanisms have been proposed to explain the beneficial effect of probiotics, including the exclusion of pathogenic bacteria and the competition with pathogenic bacteria for nutrients and epithelial cell adhesion, the production of antimicrobial substances against these harmful microorganisms, the enhancement of the mucosal barrier function, and the reestablishment of the physiological immunomodulatory function of the host [25]. According to a recent study by our group, probiotics are a significant support to SRP in the treatment of periodontitis, with a positive variation on periodontal clinical parameters and a reduction in specific periodontal bacteria; additionally, it has been suggested that probiotics not only reduce microbic counts but, above all, exert an immunomodulatory action, thus switching from a pro-inflammatory towards an anti-inflammatory response [3]. Despite the definition of probiotics requiring that microorganisms must be alive in order to guarantee benefits to the hosts' health, recent studies have shown that inactivated probiotic microorganisms (paraprobiotics) can provide these benefits too. For example, this 'biotic' category is likely to modulate the immune system and to secrete metabolites by the dead cells with an additional benefit [26]. The actions that paraprobiotics probably exert perfectly fit with the consideration of periodontitis as a process of tissues' impairment following the action of inflammatory and immune cells. On the basis of this consideration, it might be supposed that the modulatory function of paraprobiotics on specific periodontal cells justifies the additional benefit found in this study for the group assigned to the use of Biorepair Peribioma PRO. Additionally, as conventional antimicrobial agents might be effective in a short time frame, the different mechanism of action of paraprobiotics might guarantee a prolonged action, thus justifying the further change assessed in this study at the end of the follow-up for Biorepair Peribioma PRO. In fact, whereas the other toothpastes tend to show a more evident effect after a short-term period because of the shock-treatment exerted by the curative ingredients contained, conversely paraprobiotics are likely to be more effective in the long term.