Selective Antimicrobial Therapies for Periodontitis: Win the "Battle and the War"

Advances in Hydrogels for Periodontitis Treatment

Periodontitis is a common condition characterized by a bacterial infection and the disruption of the body's immune-inflammatory response, which causes damage to the teeth and supporting tissues and eventually results in tooth loss. Current therapy involves the systemic and local administration of antibiotics. However, the existing treatments cannot exert effective, sustained release and maintain an effective therapeutic concentration of the drug at the lesion site. Hydrogels are used to treat periodontitis due to their low cytotoxicity, exceptional water retention capability, and controlled drug release profile. Hydrogels can imitate the extracellular matrix of periodontal cells while offering suitable sites to load antibiotics. This article reviews the utilization of hydrogels for periodontitis therapy based on the pathogenesis and clinical manifestations of the disease. Additionally, the latest therapeutic strategies for smart hydrogels and the main techniques for hydrogel preparation have been discussed. The information will aid in designing and preparing future hydrogels for periodontitis treatment.

Addressing Antimicrobial Properties in Guided Tissue/Bone Regeneration Membrane: Enhancing Effectiveness in Periodontitis Treatment

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are the two surgical techniques generally used for periodontitis disease treatment. These techniques are based on a barrier membrane to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics, or prosthetic restoration. Numerous studies have highlighted biocompatibility, space-creation, cell-blocking, bioactivity, and proper handling as essential characteristics of a membrane's performance. Given that bacterial infection is the primary cause of periodontitis, we strongly believe that addressing the antimicrobial properties of these membranes is of utmost importance. Indeed, the absence of effective inhibition of periodontal pathogens has been recognized as a primary factor contributing to the failure of GTR/GBR membranes. Therefore, we suggest considering antimicrobial properties as one of the key factors in the design of GTR/GBR membranes. Antibiotics are potent medications frequently administered systemically to combat microbes and mitigate bacterial infections. Nevertheless, the excessive use of antibiotics has resulted in a surge in bacterial resistance. To overcome this challenge, alternative antibacterial substances have been developed. In this review, we explore the utilization of alternative substances with antimicrobial properties for topical application in membranes. The use of antibacterial nanoparticles, phytochemical compounds, and antimicrobial peptides in this context was investigated. By carefully selecting and integrating antimicrobial agents into GTR/GBR membranes, we can significantly enhance their effectiveness in combating periodontitis. These antibacterial substances not only act as barriers against pathogenic bacteria but also promote the process of periodontal healing.

Interleukin-37 ameliorates periodontitis development by inhibiting NLRP3 inflammasome activation and modulating M1/M2 macrophage polarization

OBJECTIVE

Our study was designed to explore the role of IL-37 in M1/M2 macrophage polarization imbalance in the pathogenesis of periodontitis.

BACKGROUND

Periodontitis is a chronic progressive inflammatory disease featured by gingival inflammation and alveolar bone resorption. Recent research has revealed that regulating macrophage polarization is a viable method to ameliorate periodontal inflammation. IL-37 is an anti-inflammatory cytokine, which has been reported to inhibit innate and adaptive immunity.

METHODS

For in vitro experiment, mouse macrophage RAW264.7 cells were pretreated with 0.1 ng/mL recombinant human IL-37. M1 and M2 polarizations of RAW264.7 cells were induced by 100 ng/mL LPS and 20 ng/mL IL-4, respectively. The expression of M1 (iNOS, TNF-α, and IL-6) and M2 (CD206, Arg1, and IL-10) phenotype markers in RAW264.7 cells was detected by RT-qPCR, western blotting, and immunofluorescence staining. For in vivo experiment, experimental periodontitis mouse models were established by sterile silk ligation (5-0) around the bilateral maxillary second molar of mice for 1 week. H&E staining of the maxillary alveolar bone was used to show the resorption of root cementum and dentin. Alveolar bone loss in mouse models was evaluated through micro-CT analysis. The expression of iNOS and CD206 in gingival tissues was assessed by immunohistochemistry staining. NLRP3 inflammasome activation was confirmed by western blotting.

RESULTS

IL-37 pretreatment reduced iNOS, TNF-α, and IL-6 expression in LPS-treated RAW264.7 cells but increased CD206, Arg1, and IL-10 in IL-4-treated RAW264.7 cells. LPS-induced upregulation in NLRP3, GSDMD, cleaved-IL-1β, and cleaved-caspase-1 expression was antagonized by IL-37 treatment. In addition, IL-37 administration ameliorated the resorption of root cementum and dentin in periodontitis mouse models. IL-37 prominently decreased iNOS+ cell population but increased CD206+ cell population in gingival tissues of periodontitis mice. The enhancement in NLRP3, GSDMD, cleaved-IL-1β, and cleaved-caspase-1 expression in the gingival tissues of periodontitis mice was offset by IL-37 administration.

CONCLUSION

IL-37 prevents the progression of periodontitis by suppressing NLRP3 inflammasome activation and mediating M1/M2 macrophage polarization.

Personalized antibiotic selection in periodontal treatment improves clinical and microbiological outputs

Introduction

Periodontitis is a biofilm-mediated disease that is usually treated by non-surgical biofilm elimination with or without antibiotics. Antibiotic treatment in periodontal patients is typically selected empirically or using qPCR or DNA hybridization methods. These approaches are directed towards establishing the levels of different periodontal pathogens in periodontal pockets to infer the antibiotic treatment. However, current methods are costly and do not consider the antibiotic susceptibility of the whole subgingival biofilm.

Methods

In the current manuscript, we have developed a method to culture subgingival samples ex vivo in a fast, label-free impedance-based system where biofilm growth is monitored in real-time under exposure to different antibiotics, producing results in 4 hours. To test its efficacy, we performed a double-blind, randomized clinical trial where patients were treated with an antibiotic either selected by the hybridization method (n=32) or by the one with the best effect in the ex vivo growth system (n=32).

Results

Antibiotic selection was different in over 80% of the cases. Clinical parameters such as periodontal pocket depth, attachment level, and bleeding upon probing improved in both groups. However, dental plaque was significantly reduced only in the group where antibiotics were selected according to the ex vivo growth. In addition, 16S rRNA sequencing showed a larger reduction in periodontal pathogens and a larger increase in health-associated bacteria in the ex vivo growth group.

Discussion

The results of clinical and microbiological parameters, together with the reduced cost and low analysis time, support the use of the impedance system for improved individualized antibiotic selection.

Prospective applications of extracellular vesicle-based therapies in regenerative medicine: implications for the use of dental stem cell-derived extracellular vesicles

In the 21st century, research on extracellular vesicles (EVs) has made remarkable advancements. Recently, researchers have uncovered the exceptional biological features of EVs, highlighting their prospective use as therapeutic targets, biomarkers, innovative drug delivery systems, and standalone therapeutic agents. Currently, mesenchymal stem cells stand out as the most potent source of EVs for clinical applications in tissue engineering and regenerative medicine. Owing to their accessibility and capability of undergoing numerous differentiation inductions, dental stem cell-derived EVs (DSC-EVs) offer distinct advantages in the field of tissue regeneration. Nonetheless, it is essential to note that unmodified EVs are currently unsuitable for use in the majority of clinical therapeutic scenarios. Considering the high feasibility of engineering EVs, it is imperative to modify these EVs to facilitate the swift translation of theoretical knowledge into clinical practice. The review succinctly presents the known biotherapeutic effects of odontogenic EVs and the underlying mechanisms. Subsequently, the current state of functional cargo loading for engineered EVs is critically discussed. For enhancing EV targeting and in vivo circulation time, the review highlights cutting-edge engineering solutions that may help overcome key obstacles in the clinical application of EV therapeutics. By presenting innovative concepts and strategies, this review aims to pave the way for the adaptation of DSC-EVs in regenerative medicine within clinical settings.

The "double-edged" role of progesterone in periodontitis among perimenopausal women undergoing or not undergoing scaling and root planing

Objective

Progesterone (PG) is an important sex steroid hormone commonly administered to protect the endometrium in perimenopausal women. The present study aimed to explore differential responses of periodontitis to PG in perimenopausal women who did or did not undergo scaling and root planing (SRP).

Methods

A total of 129 perimenopausal women with mild-to-moderate periodontitis were enrolled and underwent treatment as follows: SRP (n = 35); SRP + PG (n = 34); PG (n = 31); and no treatment (s) (n = 29). Pocket probing depth (PPD), clinical attachment level (CAL), sulcus bleeding index (SBI), and bleeding on probing (BOP) were measured using periodontal probes. Three inflammatory markers, including C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor-alpha (TNF-α) in gingival crevicular fluid (GCF) were measured using ELISA techniques.

Results

PPD, CAL, SBI, BOP, and levels of inflammatory factors in GCF were all significantly decreased in perimenopausal women with periodontitis after SRP. In patients who did not undergo SRP, 6 months of PG treatment significantly elevated PPD, SBI, BOP, and GCF levels of CRP, IL-6, and TNF-α. In contrast, PG exhibited inhibitory effects on periodontal inflammation in patients who underwent SRP, evidenced by significantly decreased BOP and IL-6, and slightly decreased SBI, CRP, and TNF-α. PG-induced changes dissipated 6 months after withdrawal of PG (at 12 months).

Conclusions

Among perimenopausal women with periodontitis, PG enhanced periodontal inflammation in the absence of SRP but inhibited periodontal inflammation in those who underwent SRP.

An In Vitro Study of Local Oxygen Therapy as Adjunctive Antimicrobial Therapeutic Option for Patients with Periodontitis

Periodontitis is a common global disease caused by bacterial dysbiosis leading to tissue destruction, and it is strongly associated with anaerobic bacterial colonization. Therapeutic strategies such as oxygen therapy have been developed to positively influence the dysbiotic microbiota, and the use of oxygen-releasing substances may offer an added benefit of avoiding systemic effects commonly associated with antibiotics taken orally or hyperbaric oxygen therapy. Therefore, the oxygen release of calcium peroxide (CaO₂) was measured using a dissolved oxygen meter, and CaO₂ solutions were prepared by dissolving autoclaved CaO₂ in sterile filtered and deionized water. The effects of CaO₂ on planktonic bacterial growth and metabolic activity, as well as on biofilms of Streptococcus oralis and Porphyromonas gingivalis, were investigated through experiments conducted under anaerobic conditions. The objective of this study was to investigate the potential of CaO₂ as an antimicrobial agent for the treatment of periodontitis. Results showed that CaO₂ selectively inhibited the growth and viability of P. gingivalis (p < 0.001) but had little effect on S. oralis (p < 0.01), indicating that CaO₂ has the potential to selectively affect both planktonic bacteria and mono-species biofilms of P. gingivalis. The results of this study suggest that CaO₂ could be a promising antimicrobial agent with selective activity for the treatment of periodontitis.

Histological and Histomorphometric Evaluation of Implanted Photodynamic Active Biomaterials for Periodontal Bone Regeneration in an Animal Study

Recently, our group developed two different polymeric biomaterials with photodynamic antimicrobial surface activity for periodontal bone regeneration. The aim of the present study was to analyze the biocompatibility and osseointegration of these materials in vivo. Two biomaterials based on urethane dimethacrylate (BioM1) and tri-armed oligoester-urethane methacrylate (BioM2) that additionally contained ß-tricalcium phosphate and the photosensitizer mTHPC (meso-tetra(hydroxyphenyl)chlorin) were implanted in non-critical size bone defects in the femur (n = 16) and tibia (n = 8) of eight female domestic sheep. Bone specimens were harvested and histomorphometrically analyzed after 12 months. BioM1 degraded to a lower extent which resulted in a mean remnant square size of 17.4 mm², while 12.2 mm² was estimated for BioM2 (p = 0.007). For BioM1, a total percentage of new formed bone by 30.3% was found which was significant higher compared to BioM2 (8.4%, p < 0.001). Furthermore, BioM1 was afflicted by significant lower soft tissue formation (3.3%) as compared to BioM2 (29.5%). Additionally, a bone-to-biomaterial ratio of 81.9% was detected for BioM1, while 8.5% was recorded for BioM2. Implantation of BioM2 caused accumulation of inflammatory cells and led to fibrous encapsulation. BioM1 (photosensitizer-armed urethane dimethacrylate) showed favorable regenerative characteristics and can be recommended for further studies.

Oxygen-Releasing Hyaluronic Acid-Based Dispersion with Controlled Oxygen Delivery for Enhanced Periodontal Tissue Engineering

Periodontitis is a chronic biofilm-associated inflammatory disease of the tooth-supporting tissues that causes tooth loss. It is strongly associated with anaerobic bacterial colonization and represents a substantial global health burden. Due to a local hypoxic environment, tissue regeneration is impaired. Oxygen therapy has shown promising results as a potential treatment of periodontitis, but so far, local oxygen delivery remains a key technical challenge. An oxygen (O₂)-releasing hyaluronic acid (HA)-based dispersion with a controlled oxygen delivery was developed. Cell viability of primary human fibroblasts, osteoblasts, and HUVECs was demonstrated, and biocompatibility was tested using a chorioallantoic membrane assay (CAM assay). Suppression of anaerobic growth of Porphyromonas gingivalis was shown using the broth microdilution assay. In vitro assays showed that the O₂-releasing HA was not cytotoxic towards human primary fibroblasts, osteoblasts, and HUVECs. In vivo, angiogenesis was enhanced in a CAM assay, although not to a statistically significant degree. Growth of P. gingivalis was inhibited by CaO₂ concentrations higher than 256 mg/L. Taken together, the results of this study demonstrate the biocompatibility and selective antimicrobial activity against P. gingivalis for the developed O₂-releasing HA-based dispersion and the potential of O₂-releasing biomaterials for periodontal tissue regeneration.

A Local Desiccant Antimicrobial Agent as an Alternative to Adjunctive Antibiotics in the Treatment of Periodontitis: A Narrative Review

Periodontitis is one of the most common oral polymicrobial infectious diseases induced by the complex interplay between the altered subgingival microbiota and the host’s dysregulated immune-inflammatory response, leading to the initiation of progressive and irreversible destruction of the periodontal tissues and eventually to tooth loss. The main goal of cause-related periodontal therapy is to eliminate the dysbiotic subgingival biofilm in order to arrest local inflammation and further periodontal tissue breakdown. Because, in some cases, subgingival mechanical instrumentation has limited efficiency in achieving those goals, various adjunctive therapies, mainly systemic and locally delivered antimicrobials, have been proposed to augment its effectiveness. However, most adjunctive antimicrobials carry side effects; therefore, their administration should be precociously considered. HybenX® (HY) is a commercial therapeutical agent with decontamination properties, which has been studied for its effects in treating various oral pathological conditions, including periodontitis. This review covers the current evidence regarding the treatment outcomes and limitations of conventional periodontal therapies and provides information based on the available experimental and clinical studies related to the HY mechanism of action and effects following its use associated with subgingival instrumentation and other types of dental treatments.

Introducing Nanozymes: New Horizons in Periodontal and Dental Implant Care

The prevalence of periodontal and peri-implant diseases has been increasing worldwide and has gained a lot of attention. As multifunctional nanomaterials with enzyme-like activity, nanozymes have earned a place in the biomedical field. In periodontics and implantology, nanozymes have contributed greatly to research on maintaining periodontal health and improving implant success rates. To highlight this progress, we review nanozymes for antimicrobial therapy, anti-inflammatory therapy, tissue regeneration promotion, and synergistic effects in periodontal and peri-implant diseases. The future prospects of nanozymes in periodontology and implantology are also discussed along with challenges.

N-Terminal Lysozyme Conjugation to a Cationic Polymer Enhances Antimicrobial Activity and Overcomes Antimicrobial Resistance

Microbial resistance to antibiotics is one of the greatest global healthcare challenges. There is an urgent need to develop effective strategies to overcome antimicrobial resistance. We, herein, report photoinduced in situ growth of a cationic polymer from the N-terminus of lysozyme. The attachment of the cationic polymer improves the proteolytic and thermal stability of lysozyme. Notably, the conjugate can efficiently overcome lysozyme resistance in Gram-positive bacteria and antibiotics-resistance in Gram-negative bacteria, which may be ascribed to the synergistic interactions of lysozyme and the cationic polymer with the bacteria to disrupt their cell membranes. In a rat periodontitis model, the lysozyme-polymer conjugate not only greatly outperforms lysozyme in therapeutic efficacy but also is superior to minocycline hydrochloride, which is the gold standard for periodontitis therapy. These findings may provide an efficient strategy to dramatically enhance the antimicrobial activities of lysozyme and pave a way to overcome antimicrobial resistance.

Advances of exosomes in periodontitis treatment

Periodontitis is an inflammatory disease initiated by dysbiosis of the local microbial community. Periodontitis can result in destruction of tooth-supporting tissue; however, overactivation of the host immune response is the main reason for alveolar bone loss. Periodontal tissue cells, immune cells, and even further activated osteoclasts and neutrophils play pro-inflammatory or anti-inflammatory roles. Traditional therapies for periodontitis are effective in reducing the microbial quantities and improving the clinical symptoms of periodontitis. However, these methods are non-selective, and it is still challenging to achieve an ideal treatment effect in clinics using the currently available treatments and approaches. Exosomes have shown promising potential in various preclinical and clinical studies, including in the diagnosis and treatment of periodontitis. Exos can be secreted by almost all types of cells, containing specific substances of cells: RNA, free fatty acids, proteins, surface receptors and cytokines. Exos act as local and systemic intercellular communication medium, play significant roles in various biological functions, and regulate physiological and pathological processes in numerous diseases. Exos-based periodontitis diagnosis and treatment strategies have been reported to obtain the potential to overcome the drawbacks of traditional therapies. This review focuses on the accumulating evidence from the last 5 years, indicating the therapeutic potential of the Exos in preclinical and clinical studies of periodontitis. Recent advances on Exos-based periodontitis diagnosis and treatment strategies, existing challenges, and prospect are summarized as guidance to improve the effectiveness of Exos on periodontitis in clinics.

Resolvin E1's Antimicrobial Potential Against Aggregatibacter Actinomycetemcomitans

Background

Microorganisms along with host response play a key role in the development of periodontal and peri-implant infections. Advanced periodontal and peri-implant diseases are most likely associated with bacterial plaques that trigger host immune response and eventually lead to the destruction of the attachment apparatus and bone loss around a tooth or a dental implant. A recent systematic review and meta-analysis revealed that Aggregatibacter actinomycetemcomitans had the highest association with peri-implantitis. Resolvin E1 (RvE1) is part of the specialized pro-resolving lipid mediator family biosynthesized from omega-3, polyunsaturated fatty acids (PUFAs), and eicosapentaenoic acid (EPA). Although RvE1 is an established anti-inflammatory agent, it was found that its application as a treatment or as a preventive drug had an indirect effect on the subgingival microbiota of both rats and rabbits with experimental periodontitis.

Aim

The aim of this study is to evaluate the direct antimicrobial effect of RvE1 on Aggregatibacter actinomycetemcomitans bacteria.

Materials and Methods

The study comprised three groups that underwent minimum inhibitory concentration (MIC) against Aggregatibacter actinomycetemcomitans. The first group was tested with the RvE1 working concentration of 5 ug/ml, the second group was tested with ethanol (EtOH), 10% as the working concentration, and the final group was diluted in phosphate-buffered saline (PBS) as the positive control. Optical density (OD600) was used for the comparison of bacterial growth among the tested groups. The experiment was conducted in three biological replicates. Data were analyzed using SPSS, and results were analyzed by using one-way analysis of variance (ANOVA) followed by post-hoc Bonferroni using a minimum level of significance (P-value) of 0.05.

Results

Minimum inhibitory concentration was 1.25 μg/ml and 5% for RvE1 and EtOH, respectively. RvE1's mean optical density (OD600) was 0.156 ± 0.021 and was significantly lower compared with all the other groups (P-value &lt; 0.01). The EtOH group (mean OD600 0.178 ± 0.013) and the PBS group (mean OD600 0.1855 ± 0.022) did not reveal a significant difference (P-value = 0.185).

Conclusion

RvE1 demonstrated significant antimicrobial activity against A. actinomycetemcomitans with an MIC of 1.25 μg/ml. The RvE1 group showed significantly lower bacterial growth compared to the EtOH and PBS groups.

The Effect of Acknowledged and Novel Anti-Rheumatic Therapies on Periodontal Tissues-A Narrative Review

Rheumatoid arthritis (RA) and periodontal disease (PD) are chronic complex inflammatory diseases with several common susceptibility factors, especially genetic and environmental risk factors. Although both disorders involve a perturbation of the immune–inflammatory response at multiple levels, one major difference between the two is the different locations in which they develop. RA is triggered by an exaggerated autoimmune response that targets joints, while periodontal disease occurs as a consequence of the subgingival periodontopathogenic microbiota. Current treatment models in both pathologies involve the stratification of patients to allow therapeutic individualization according to disease stage, complexity, progression, lifestyle, risk factors, and additional systemic diseases. Therapeutic guidelines for RA comprise of five main classes of drugs: non-steroidal anti-inflammatory drugs (NSAIDs), analgesics, glucocorticoids, and disease-modifying anti-rheumatic drugs (DMARDs): biologic and non-biologic. Although various treatment options are available, a definitive treatment remains elusive, therefore research is ongoing in this area. Several alternatives are currently being tested, such as matrix metalloproteinases (MMP) inhibitors, toll-like receptors (TLR) blockers, pro-resolution mediators, anti-hypoxia inducing factors, stem cell therapy, NLRP3 inhibitors and even natural derived compounds. Although the link between PD and rheumatoid arthritis has been investigated by multiple microbiology and immunology studies, the precise influence and causality is still debated in the literature. Furthermore, the immunomodulatory effect of anti-rheumatic drugs on the periodontium is still largely unknown. In this narrative review, we explore the mechanisms of interaction and the potential influence that anti-rheumatoid medication, including novel treatment options, has on periodontal tissues and whether periodontal health status and treatment can improve the prognosis of an RA patient.