Photodynamic therapy involves interactions between a light source and a photosensitizer in an aerobic environment. This results in the generation of free oxygen radicals that damage target cells such as bacterial cells . Photodynamic therapy has also been reported to kill pathogenic microbes associated with the etiology of periodontal and peri-implant disease caused Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Prevotella intermedia, and Porphyromonas gingivalis (P. gingivalis) . MD with adjunct photodynamic therapy is more effective in reducing peri-implant PPD than MD alone at 3 months following treatment (Fig. 2). However, the long-term outcomes of MD either with or without photodynamic therapy are comparable .
The adjunct use of diode laser did not yield any additional positive influence on the peri-implant healing as compared to MD alone at 3 months or 6 months following treatment [14, 45]. Two included RCTs described the effect of Er:YAG laser (ERL) as an adjunct in the treatment of peri-implant diseases. Studies have indicated that non-surgical periodontal treatment with an ERL significantly improves the clinical outcomes, based on PPD reduction and gain of CAL [46, 47]. The sites treated with ERL demonstrated an alteration in the mean CAL value from 5.8 ± 1 mm at baseline to 5.1 ± 1.1 mm after 6 months. Frank et al.  found that ERL reduces BOP significantly at 6 months after the treatment. Thus, further studies are needed to compare the effectiveness of ERL modality to that of other adjunctive therapies.
A total of two included RCTs evaluated the effect of air abrasive as an adjunct in the treatment of peri-implant diseases [10, 11]. Both found that adjunctive air abrasive treatment seemed to have a limited beneficial effect as compared to MD alone. Air abrasive devices have been shown to be a feasible treatment option in periodontal care because of the potential to effectively erase biofilms . Nonetheless, professional MD can also effectively remove the biofilms from the instrument-accessible sites; thus, the adjunctive effect of air abrasive may be limited.
Chlorhexidine is a commonly used topical drug. As shown in Fig. 3, compared to MD alone, MD with chlorhexidine has a limited beneficial effect at 3 months post-treatment. An included article reported the adjunctive effect of chloramine and found that it could not improve the clinical outcomes of peri‐implant diseases . The effects of probiotic Lactobacillus reuteri in combination with MD were evaluated in implants with peri-implantitis, and no clinical differences between probiotic and placebo treatments were observed over time [35, 36] (Fig. 4). Conversely, minocycline microspheres as an adjunct to MD treatment of incipient peri-implantitis lesions demonstrated improvements in PPD and BI and the improvements were sustained over 6 months [28, 29]. The state, concentrations, and the method of delivery of topical drugs may affect the effectiveness of the drugs. Dental water jet rinse mixed with chlorhexidine gel might supplement the response to non-surgical treatment for peri-implantitis lesions by reducing the PPD . Some studies demonstrated that repeated application of chlorhexidine chips might resolve the marginal peri-implant inflammation in terms of BOP better than that by chlorhexidine gel, and the PPD was also reduced 0.65 ± 0.40 mm [30, 38]. The efficacy of a single dose is limited, but the repeated application of local drugs can prolong the effectiveness. However, the frequent use of antibiotics causes bacterial resistance in the subgingival biofilm . Currently, there is no consensus on the method of delivery of topical drugs for the treatment of peri-implant diseases, thereby necessitating additional studies.
The standardized mean difference of clinical outcomes (BOP, PPD) between the MD group with systemic antibiotics treatment and MD alone was not significantly different from 0 (P = 0.47) (Fig. 5). Hitherto, no evidence is available promoting the use of systemic antibiotics in the treatment of peri-implantitis [33, 34].
Tapia et al.  found that modifying the contour of the prostheses after MD significantly improved the clinical outcomes of peri‐implant mucositis. This conclusion was correlated to the inclusion criteria of the study, which required the included patients to have at least one implant-supported restoration with an inappropriate prosthesis design or contour that made oral hygiene and access to the implant in the neck difficult. The implant-supported prosthesis design is critical to promote accessibility to oral hygiene around the implants , suggesting a method for the treatment of peri-implantitis.
Enamel matrix derivatives have been employed successfully in the management of periodontal diseases, especially bone loss associated with periodontitis . Kashefimehr et al.  studied the effects of enamel matrix derivative on the non-surgical management of peri-implant mucositis and found that MD in conjunction with enamel matrix derivative, air abrasive, and 0.12% chlorhexidine mouthwash significantly improved BOP and PPD at 3 months after the treatment. In the group with enamel matrix derivative, PPD reduced from 5.40 ± 1.79 mm to 4.66 ± 1.95 mm. However, additional studies are required to prove the efficacy of enamel matrix derivative in long-terms.
After comparing different adjunctive therapies, we found that the use of ERL or repeated minocycline microspheres as an adjunct to MD treatment for peri-implantitis is better than chlorhexidine gel [12, 28]. The adjunct use of photodynamic therapy was as effective as one unit-dosage of minocycline microspheres or diode laser after 6 months of follow-up [15, 21, 22]. The efficacy of probiotics as an adjunct to the MD treatment was better than that of systemic antibiotics in reducing PPD and mBI (modified bleeding index). Nonetheless, further studies are needed to compare the effectiveness of different adjunctive therapies.