## 4 Discussion
### Probiotics in Periodontology
#### 4.2.2 Probiotics in Periodontitis
Most clinical and microbiological parameters (as evidenced by a delay of recolonization up to 6 months) were significantly improved during the study period and the probiotic groups had fewer patients at high risk of disease progression and more patients at low risk. In one study the probiotic was found until day 90 in 11 patients and was no longer found on day 180, indicating temporary colonization [31]. Residual periodontal pockets are associated with an increased risk of periodontal disease progression and therefore require additional treatment. The effect of probiotic combination _L. reuteri_ ATCC PTA 5289 and DSM 17938 as an adjunct to the SRP treatment of residual pockets was evaluated in patients with chronic periodontitis previously treated [57]. The use of _L. reuteri_ after re-instrumentation did not affect colonization by periodontalopathogens. While no significant clinical improvement was observed after 12-week consumption of probiotics and after 12 weeks of discontinuation, at 24 weeks after discontinuation PD was significantly reduced in moderate and deep pockets, and more pockets were sealed in the probiotic group. Taken together, these studies suggest that probiotic _L. reuteri_ may serve as an effective complement to mechanical therapy in the treatment of chronic and relapsing periodontitis. In a study by [PERSON] et al. [45], use of _L. salivarius_ NK02 in mouthwash for 28 days significantly improved clinical parameter (reduced PD, GI, and BOP) in patients with chronic periodontitis. In addition, _Aggregatibacter actomyosin_ counts in saliva and gingival circular fluid were significantly reduced in the test group which also presented more commensal bacteria than the placebo group. _Bifidobacterium animalis subsp. lactis_ HN019 was evaluated for 30 days in patients with chronic periodontitis [58]. The probiotic colonized the subgingival flora for 60 days. There was a significant reduction of IL-1\(\beta\) at the end of 30-90 days, and IL-8 at the end of 30 days as compared to the control group. Likewise, there was a higher reduction of periodontitis (_P. gingivalis_, _T. denticola_, _F. nucleatum sub_ spp. _vincenti_) in the test group up to 90 days. Clinical parameters improved significantly in the test group as determined by CAL and PD (in moderate and deep pockets at 90 days), and the risk of disease progression was also lower in the test group relative to the control group. In a study by [PERSON] et al. [59], the use of probiotics combinations for 6 months as an adjunct to SRP in patients with periodontitis improved clinical parameters in both probiotics groups (group 2: toothpaste with _Bifidobacterium_ and _Lactobacillus_ and group 3: toothpaste + chewing-gum with _L. reuteri_, _L. salivarius_, and _L. plantarum_), except for adherent gingiva and RG. Hence, BOP, PI, number of bleeding sites, pathological site, and sulcus bleeding index improved significantly at month 3 in both groups (also at month 6 in group 3). PD and CAL also improved significantly at month 3 in both groups. There was a significant reduction of orange complex pathogens _P. intermedia_ and _F. nucleatum_ between 3 and 6 months in both probiotics groups. Overall, group 3 presented better and more durable effects than group 2 suggesting a synergistic effect between the probiotic strains present in toothpaste and chewing-gum.