# Peri-Implantitis Causal Therapy with and Without Doxycycline: Retrospective Cohort Clinical Study
## 4. Discussion  
The results of this retrospective study showed a significant improvement in peri-implant parameters in the group treated with non-surgical causal therapy combined with topical doxycycline compared to the group treated with non-surgical causal therapy alone. The improvement seen in TG in terms of reduction of PPD, BoP, PI, and suppuration confirms the efficacy of using local doxycycline as an adjunctive treatment for the management of peri-implantitis. Similar results were reported by [PERSON] et al., who evaluated, using a mouse model, the efficacy of applying doxycycline to implant surfaces to modulate the progression of peri-implantitis. The study used an experimental model in which implants treated with doxycycline were compared to untreated implants. The results showed a significant reduction in peri-implant bone loss (2.3 \(\pm\) 0.4 mm in controls vs. 0.9 \(\pm\) 0.2 mm in treated) and a decrease in the inflammatory infiltrate in the treated sites compared to the control group, supporting the efficacy of the antibiotic in improving local inflammatory parameters [28]. [PERSON] et al. conducted an in vitro study to evaluate the antimicrobial efficacy of a controlled release system containing metronidazoleade and doxycycline. The results showed a significant reduction in bacterial growth of Aggregatibacter Actinomycetemcomitans and Porphyromonas Gingivalis, two key pathogens in peri-implantitis, confirming the efficacy of sustained-release antibiotics [29]. Figure 7. Change in suppuration from baseline to follow-up for CG and TG. A systematic review by [PERSON] et al. analysed data from clinical and randomised controlled trials to evaluate the efficacy of local antibiotics in peri-implantitis management. The review included 15 studies with a total of 742 patients and reported an average PPD reduction of 1.5 mm and BoP improvement of 30% in patients treated with local antibiotics compared to mechanical decontamination alone, suggesting a significant clinical benefit of additional antibiotic therapy [30]. The randomized controlled trial by [PERSON] et al. evaluated the efficacy of doxycycline extended release in the treatment of peri-implantitis in a sample of 50 patients followed for 6 months. The doxycycline-treated group showed an average reduction in PPD of 2.1 mm compared to a reduction of 0.9 mm in the control group, with a significant improvement also in BoP (\(-\)35% in the treated group) [31]. [PERSON] et al. conducted a randomized split-mouth clinical trial of 30 patients evaluating the prophylactic application of doxycycline at the implant-abutment interface. After a 12-month follow-up, BoP was reduced by 40% in treated sites compared to control sites, suggesting a positive effect of the antibiotic in preventing peri-implant inflammation [32]. The issue of antibiotic resistance is a critical factor in the management of peri-implantitis. A systematic review conducted by [PERSON] et al. examined the phenomenon of resistance in patients with peri-implant infections, showing that 35% of Porphymonas Gingivalis strains isolated from infected sites had resistance to commonly used antibiotics, including doxycycline and metronidazolezole, emphasising the need for prudent use of these therapeutic agents [33]. Also, [PERSON], in a literature review, suggested a selective approach to the use of local antibiotics to minimise the risk of resistance and recommended their use only in cases of advanced peri-implantitis with documented presence of specific pathogens [34]. Smoking has been widely recognized as a risk factor for peri-implantitis, as well as for treatment effectiveness. [PERSON] et al. conducted a meta-analysis of 18 clinical studies with a total of 3215 patients and reported that smokers had a peri-implantitis incidence of 22.1%, significantly higher than non-smokers (12.3%). Similarly, [PERSON] et al. showed that the risk of peri-implantitis in smokers is 2.5 times higher than in non-smokers, confirming the negative influence of smoking on implant prognosis [35,36].