Periodontitis, a chronic inflammatory disease, is primarily initiated by the organization of specific oral bacteria into biofilms, which subsequently trigger a localized destructive inflammatory response leading to the formation of periodontal pockets [8]. This host response, if left unchecked, can lead to the progressive destruction of the periodontal ligament and alveolar bone, culminating in tooth mobility and eventual tooth loss [9]. While conventional non-surgical therapy, including scaling and root planing, remains the gold standard for removing bacterial biofilms and calculus deposits, the re-colonization of treated sites by periodontopathogens often limits its long-term effectiveness [4]. Consequently, adjunctive therapies, such as systemic antimicrobials and probiotics, have been proposed to enhance the impact of scaling and root planing by further altering the oral microbial ecology towards a state compatible with periodontal health [10]. Probiotics, by introducing beneficial microorganisms, can directly compete with pathogenic bacteria, produce antimicrobial substances, and modulate the host immune response, thereby contributing to dysbiosis reversal and improved clinical outcomes [8][11]. Research indicates that while scaling and root planing are foundational treatments, they are often insufficient alone for completely reducing subgingival microbiota, underscoring the need for supplemental interventions like probiotic administration [7]. The improper use of antibiotics as an adjunctive treatment, however, has led to bacterial resistance and recolonization of periodontal pockets, highlighting the urgent need for novel and effective adjunct therapies like probiotics [12]. Probiotics offer a promising alternative by promoting a balanced oral microbiome and mitigating inflammatory responses without contributing to antibiotic resistance, a significant advantage over conventional antimicrobial agents [2]. This approach supports the hypothesis that specific probiotic strains can significantly impact the clinical progression of periodontitis by influencing the microbial balance within the oral cavity [13]. Specifically, probiotic interventions aim to reduce the burden of key periodontal pathogens such as *Porphyromonasgingivalis*, *Tannerellaforsythia*, and *Treponemadenticola*, which are strongly implicated in disease progression [14][15]. This literature review will explore the mechanisms through which probiotics exert their beneficial effects, including competitive exclusion, immunomodulation, and the production of antimicrobial compounds [9]. A deeper understanding of these mechanisms is crucial for optimizing probiotic formulations and delivery methods to achieve maximal therapeutic efficacy in periodontal therapy. Furthermore, the review will consider how different probiotic strains and their modes of delivery might influence their effectiveness as an adjunct to traditional mechanical debridement [7]. The varying forms of administration, dosage, frequency, and duration of probiotic therapy across studies highlight the necessity for standardized protocols to achieve more predictable clinical outcomes and facilitate comparative analyses [4]. Additionally, the long-term impact of probiotic interventions on the stability and resilience of the oral microbiota following periodontal therapy warrants further investigation to ascertain their sustained clinical benefits [9]. Ultimately, an in-depth analysis of these factors will provide a robust evidence base for integrating probiotics into routine periodontal care. This includes assessing the specific strains of *Lactobacillus* and other bacteria with probiotic characteristics that demonstrate the most significant clinical benefits and their mechanisms of action in mitigating periodontal disease [16].

The oral microbiome, a complex ecological community comprising over 700 bacterial species along with archaea, fungi, and viruses, plays a pivotal role in maintaining oral health or contributing to the pathogenesis of diseases like periodontitis. Within this intricate ecosystem, a dynamic balance between commensal and potentially pathogenic microorganisms is crucial, with dysbiosis—an imbalance in microbial composition—being a key driver of periodontal inflammation [17]. Beneficial bacteria, such as certain Gram-positive aerobic species like *Streptococcussanguinis* and *Lactobacillus*, contribute to a healthier homeostasis within the oral cavity, actively counteracting the proliferation of periodontopathogens and modulating host inflammatory responses [18]. Conversely, an increase in microbial diversity, particularly involving species associated with periodontal disease, can contribute to the shift towards a dysbiotic state [19]. This shift often entails an enrichment of Gram-negative anaerobes and a reduction in beneficial commensals, leading to chronic inflammation and tissue destruction [20]. Specifically, the presence of lactic acid bacteria, including various species of *Lactobacillus*, is linked to the production of antimicrobial agents like lactic acid and bacteriocins, which can suppress the growth of pathogenic bacteria [7]. This underscores the potential of probiotics, particularly strains within the *Lactobacillus* genus, to re-establish a healthy microbial balance and contribute to the prevention and management of periodontal diseases [21]. The application of *Lactobacillus* and *Bifidobacterium* as probiotics has been widely investigated for their role in preventing periodontitis and serving as adjunctive treatments, given their capacity to inhibit periodontal pathogens and their documented safety for human consumption [16].

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, a definition endorsed by the Food and Agricultural Organization/World Health Organization [22]. In the context of oral health, these beneficial microbes, often from genera such as *Lactobacillus* and *Streptococcus*, function through various mechanisms including competitive exclusion of pathogens, production of antimicrobial compounds, and immunomodulation of the host [23]. These mechanisms enable probiotics to not only directly combat pathogenic bacteria but also to fortify the host’s natural defenses against periodontal disease progression [24]. Specifically, probiotics can antagonize the activity of cytotoxic metabolites produced by harmful bacteria and can directly interact with pathogens through coaggregation, thereby inhibiting their growth and biofilm formation [25]. They achieve this by competing for essential nutrients and adhesion sites, effectively displacing undesirable microorganisms from the oral cavity [26]. Moreover, certain probiotic strains, including *Lactobacillusfermentum* and *Lactobacillusgasseri*, produce hydrogen peroxide and bacteriocins, which directly inhibit the growth of key periodontal pathogens such as *Porphyromonasgingivalis* and *Aggregatibacteractinomycetemcomitans* [27]. This antagonistic action disrupts the integrity of pathogenic biofilms and prevents their colonization on oral tissues [27]-[29]. Beyond direct antimicrobial effects, probiotics also modulate the host immune response by influencing cytokine production and activating T-lymphocytes, thereby reducing inflammation and supporting tissue repair in periodontal lesions [30]. This is achieved by specific probiotic strains interacting with immune cells like macrophages, dendritic cells, and T-lymphocytes, leading to a down-regulation of pro-inflammatory cytokines (e.g., IL-1β, TNF-α) and an up-regulation of anti-inflammatory cytokines (e.g., IL-10), thus fostering a more balanced immune response [31]. The conceptualization of probiotics, tracing back to Elie Metchnikoff in the early 20th century, highlights their historical significance in promoting overall health, with their oral application representing a more recent but rapidly expanding field of research [32]. This historical perspective underscores the evolving understanding of microbial interactions and their profound impact on human physiology, extending from gastrointestinal health to the complex dynamics of the oral cavity [33][34]. While the precise molecular mechanisms of probiotic action in the oral cavity are still under investigation, key functions involve competition for attachment sites, production of antimicrobial compounds, and regulation of immune responses against pathogens [35][36]. The local effects within the oral biofilm involve co-aggregation, competitive exclusion, bacteriocin production, and nutrient competition [19]. Furthermore, these beneficial bacteria can attach more strongly to oral tissues than pathogens, leading to bacterial aggregation and co-aggregation, which forms a new “biofilm” that can outcompete detrimental species [37]. This competitive dynamic, coupled with their ability to produce antimicrobial compounds like hydrogen peroxide and organic acids, actively prevents the proliferation and colonization of periodontopathogens [38][9]. For example, *Lactobacillusgasseri* produces significant quantities of lactic acid which acidifies the cytoplasm of pathogens like *Porphyromonasgingivalis* and *Streptococcusmutans*, inhibiting their proliferation [39]. Beyond these local effects, probiotics also contribute to systemic immunomodulation, thereby influencing the host’s overall inflammatory response to oral pathogens [14]. This includes the capacity of certain lactic acid bacteria to interact with immunocompetent cells, such as macrophages and T-cells, thereby altering cytokine production and overall immune function [40]. This immunomodulatory capacity can manifest as a reduction in pro-inflammatory mediators and an upregulation of anti-inflammatory cytokines, contributing to a more balanced immune response in the periodontal tissues [41]. This intricate interplay between probiotic strains and host immunity underscores their potential as a therapeutic strategy for managing periodontal diseases [34]. Moreover, specific strains, such as *Lactobacillusparacasei* and *Lactobacillusrhamnosus*, have demonstrated significant antagonistic capabilities against key oral pathogens like *Streptococcusmutans* and *Porphyromonasgingivalis* [42]. Their mechanisms include not only direct antimicrobial action but also coaggregation with pathogens, forming a protective barrier that impedes pathogen colonization [43]. This competitive exclusion, alongside the production of antimicrobial substances, contributes to a robust defense against periodontopathogens [42]. This intricate interaction is further enhanced by their ability to modulate the oral microbiome, shifting the balance from dysbiotic to eubiotic states [33].

Given the complex etiology of periodontal diseases, which involves a dysbiotic shift in the oral microbiome and a consequent inflammatory host response, probiotics offer a promising adjunctive therapeutic approach by targeting both microbial and immunological aspects [44]. Their ability to restore microbial homeostasis and dampen excessive inflammatory responses provides a compelling rationale for their integration into comprehensive periodontal treatment protocols [45]. Specifically, the positive effects of probiotics on oral health extend to improving gingival health, reducing dental plaque accumulation, and favorably modulating immunological and microbiological factors [27]. The immunomodulatory effects of certain *Lactobacillus* strains, for instance, involve reducing pro-inflammatory cytokines while elevating anti-inflammatory cytokines, which collectively mitigate tissue destruction and foster periodontal healing [28]. This immune modulation is critical, as it directly impacts the progression of chronic periodontitis by inhibiting the secretory activity of Th17 lymphocytes, which are known contributors to excessive cytokine responses leading to periodontal tissue damage [31]. Furthermore, probiotics, predominantly from the *Lactobacillus* and *Bifidobacterium* genera, have demonstrated efficacy in preventing and treating periodontal diseases through their regulatory influence on the periodontal microbiota and the host immune system [46]. These probiotic interventions can interfere with pathogen attachment to mucosal surfaces, produce antibacterial bacteriocins, and reduce pro-inflammatory cytokine production, thereby offering a multifaceted approach to periodontal health management [47].

This literature review therefore aims to comprehensively assess the current scientific evidence regarding the efficacy of probiotic supplementation as an adjunctive therapy in initial periodontal treatment.

A comprehensive search was performed across multiple electronic databases, including PubMed, Web of Science, Scopus, and Cochrane Library, compiling studies conducted on humans, published in English between 2020 and 2025. The search strategy utilized a combination of Medical Subject Headings and free-text terms related to “probiotics”, “gingivitis”, “periodontitis”, “adjunctive therapy”, “oral microbiome”, and “Lactobacillus”. The search was further refined by including terms such as “Bifidobacterium”, “Streptococcus”, and “Saccharomyces” to capture a broad range of relevant probiotic strains investigated for oral health applications. Boolean operators and truncation symbols were applied to optimize the search yield, ensuring broad coverage of the literature [4]. The search strategy also incorporated terms such as “Porphyromonasgingivalis”, “Aggregatibacteractinomycetemcomitans”, and “Fusobacteriumnucleatum” to identify studies focusing on specific pathogenic bacteria commonly associated with periodontal disease, further refining the scope of the review to interventions directly impacting these key microbial players.

The comprehensive search involved MEDLINE (via PubMed), Embase, Scopus, Web of Science, and the Cochrane Central Register of Controlled Trials, utilizing a detailed search strategy combining MeSH terms and free-text keywords for probiotics, periodontal diseases, and adjunctive therapies.

Articles were selected based on their relevance to the review’s aim. Primary research articles, systematic reviews, and meta-analyses investigating the use of probiotics as an adjunct to non-surgical periodontal therapy in human adults with gingivitis or chronic periodontitis were considered. Studies involving animal models, in vitro experiments, or participants with systemic diseases affecting periodontal health were generally excluded. Additionally, case reports and opinion pieces were typically not included to maintain focus on empirical evidence. Articles that did not explicitly detail the probiotic strain, dosage, frequency, or duration of intervention were also generally excluded, prioritizing clinically relevant and reproducible data.

Relevant information was extracted from the selected articles, focusing on study design, participant characteristics, intervention details (probiotic strain, dosage, duration, and delivery method), and key outcome measures. These included clinical parameters such as probing pocket depth, clinical attachment loss, and bleeding on probing, as well as microbiological changes (e.g., alterations in specific periodontal pathogens). The findings were then synthesized thematically, providing a narrative overview of the current understanding of probiotic efficacy, mechanisms of action, and identified limitations in the field.

This section summarizes the key characteristics of the 14 articles included in this literature review, which investigate the application of probiotics in periodontal therapy. These articles encompass randomized controlled trials, systematic reviews, meta-analyses, and a scoping review, providing a comprehensive overview of the field.

The table below outlines the first author and publication year, study type/design, specific probiotic strain (s) or intervention, number of participants (or studies included for reviews), and main findings related to periodontal parameters or oral health for each included work. (Table 1)

Table 1. Characteristics of included studies.

The reviewed articles collectively suggest that probiotics hold promising potential as adjunctive treatments in non-surgical periodontal therapy. While findings exhibit some variability, several consistent themes emerge regarding their efficacy and mechanisms of action in transforming oral health.

3.2.1. Clinical Parameter Improvements

Many studies, particularly randomized controlled trials, report significant improvements in key clinical parameters associated with periodontal disease when probiotics are used as an adjunct to initial periodontal treatment. These improvements include:

ReducedProbingDepth: Several studies indicate that probiotics can lead to a significant reduction in probing depth, especially in moderate pockets, potentially decreasing the need for surgical interventions [1].ReducedBleedingonProbing: A consistent finding across multiple reviews and trials is the significant reduction in bleeding on probing, suggesting an anti-inflammatory effect and improved gingival health [1]. ImprovedClinicalAttachmentLevel: Some studies, particularly those with longer intervention periods, also report improvements in clinical attachment levels [28]ReducedPlaqueIndex: While less consistently reported than BoP or PD, some studies note a reduction in plaque index in probiotic groups [28][48].

3.2.2. Microbiological Modulation

A primary mechanism by which probiotics are thought to exert their benefits is through the modulation of the oral microbiome, aiming to restore homeostasis by reducing pathogenic bacteria and promoting beneficial ones.

ReductionofPathogenicBacteria: Specific probiotic strains, such as Lactobacillusreuteri, have been shown to significantly decrease counts of periodontal pathogens like Aggregatibacteractinomycetemcomitans and Tannerellaforsythia [51][52]. However, the impact on other pathogens like P. gingivalis or P. intermedia can be variable [51].IncreaseinBeneficialBacteria: Probiotic interventions are often associated with an increase in beneficial bacterial strains, contributing to a healthier microbial balance [1].HealthyPeriodontalTissueCandidates: Research has also identified bacteria naturally found in healthy periodontal tissues, such as Streptococcussanguinis, Streptococcusoralis, and Streptococcusmitis, as potential probiotic candidates due to their antimicrobial properties and association with health [16].

3.2.3. Anti-Inflammatory Effects

Probiotics can also exert anti-inflammatory effects, leading to a decrease in inflammatory markers.

DecreasedInflammatoryMarkers: Studies show a reduction in inflammatory cytokines such as IL-1β and TNF-α following probiotic therapy [1].

3.2.4. Specific Strains and Administration Methods

A variety of probiotic strains and delivery methods have been investigated:

LactobacillusSpecies:Lactobacillusreuteri is frequently cited for its positive effects on clinical parameters and microbial composition [2][52]-[54]. Other Lactobacillus strains (e.g., L. rhamnosus, L. plantarum) are also explored [50][53].StreptococcusSpecies:StreptococcussalivariusM18 has demonstrated efficacy in improving clinical parameters and shifting the pathogenic profile [48]. Streptococcusoralis is also noted as a potential candidate [50].DeliveryMethods: Probiotics have been administered through various forms, including lozenges, tablets, capsules, mouthwashes, and even toothpaste [28][48][53]. The duration of intervention typically ranges from a few weeks to several months [28][49][50].

3.2.5. Adjunctive Role and Comparisons

Probiotics primarily serve as an adjunct to non-surgical periodontal therapy, such as scaling and root planing.

ComplementtoNSPT: Several systematic reviews conclude that probiotics provide an additional benefit to manual debridement in chronic periodontitis, enhancing the outcomes of NSPT [5][8].ComparisonwithChlorhexidine: One systematic review and meta-analysis suggested that probiotics could be an effective and safe alternative to chlorhexidine mouthwash, especially regarding their therapeutic effects on periodontal status, although immediate gingival index improvement within 4 weeks may not be significantly different [6].

3.2.6. Limitations and Future Directions

Despite the promising results, the field still faces challenges:

Heterogeneity: Significant heterogeneity exists across studies regarding probiotic strains, dosages, administration routes, and study designs, making direct comparisons difficult [2][5].Long-termEffects: More research is needed on the long-term effects of probiotic interventions [5].StandardizedProtocols: There is a recognized need for more standardized protocols concerning the optimal dose, specific strains, and administration routes to maximize efficacy [5][8][50].MechanismElucidation: Further investigation is required to fully elucidate the antimicrobial effects and modulatory host responses of different probiotics [5].

In summary, the current knowledge suggests that probiotics, particularly certain Lactobacillus and Streptococcus strains, can effectively serve as an adjunct to initial periodontal treatment by improving clinical periodontal parameters, modulating the oral microbiome towards a healthier state, and reducing inflammation. While their integration into standard care is supported by a growing body of evidence, further standardized research is crucial to optimize their application.

The consistent reduction in PPD and BOP, critical indicators of periodontal inflammation and disease activity, is a notable strength of probiotic adjunctive therapy [2][54]. The observed improvements in CAL, particularly in longer-term interventions or specific probiotic regimens [28][52][53], suggest a potential for tissue stabilization and possibly regeneration, which is a significant outcome in periodontitis management. The immunomodulatory capacities of certain probiotic strains, such as S. salivariusM18, in attenuating inflammatory responses, are crucial for controlling the destructive processes in periodontitis [48][55]. also emphasize the growing understanding of immunomodulation as a key therapeutic target in periodontitis, which probiotics can influence [55].

Microbiologically, various probiotics appear to re-establish a more balanced oral microbiota by directly inhibiting pathogens like A. actinomycetemcomitans and T. forsythia [52][51]. or by creating an environment less favorable for their proliferation through mechanisms like reuterin production, competition for adhesion sites, and pH modulation [2][48]. The identification of Streptococcus species from healthy periodontal tissues as potential probiotic candidates further supports the concept of therapeutic microbial modulation [16].

While Lactobacillusreuteri is frequently highlighted as a comprehensive and effective probiotic in several reviews within our initial selection [2] other studies identified in this review offer further comparative insights into strain-specific effects and broader applications. For instance, the efficacy of StreptococcussalivariusM18 was demonstrated by Chen etal. [48], showing significant improvements in clinical parameters and a shift towards a decreased pathogenic profile. Similarly, Yılmaz & Görgin [53] explored the benefits of a combination of Lactobacillusrhamnosus and Bifidobacteriumanimalis. lactis. This highlights that efficacy is not limited to a few well-studied strains but can extend to various species and combinations, as also noted by Angarita-Díaz etal. [16], who identified other Streptococcus species (S. sanguinis,S. oralis,S. mitis) as potential probiotic candidates from healthy periodontal tissues. The observation across our selected studies, including the comprehensive review by Vives-Soler & Küstner, further corroborates that efficacy is highly strain-dependent and influenced by factors such as administration routes, doses, and colonization ability [8].

Beyond the direct focus on probiotics in periodontal therapy, the broader field of oral microbiome research also explores related concepts and broader applications. For instance, among our included studies, Vives-Soler & Küstner found a slight tendency toward better results in the probiotic group for peri-implant mucositis. This suggests a wider range of oral health conditions where probiotics are being investigated, demonstrating their versatile therapeutic potential. Related concepts like synbiotics and postbiotics also represent promising future avenues for periodontal therapy [8].

Several studies included in this review position probiotics as a viable adjunct or even an alternative to traditional antimicrobial agents. For example, Soares etal. [6] found that probiotics could be an effective and safe alternative to chlorhexidine mouthwash for improving periodontal status. Furthermore, an external systematic review by Puzhankara etal. [56]. directly aimed to compare the effectiveness of probiotics versus antibiotics for treating periodontal disease, finding that most studies comparing probiotics with antibiotics for the treatment of periodontal disease revealed probiotics to be a viable alternative to antibiotics. This reinforces the notion within our primary articles, as highlighted by Mendonça etal. and Robo etal., that probiotics can mitigate concerns about antibiotic resistance and side effects associated with conventional antiseptics like chlorhexidine [5][49].

Despite the encouraging results, the existing literature consistently exhibits considerable heterogeneity across numerous reviews, including Mendonça etal. [54][8][50]. This heterogeneity, also highlighted by external reviews such as Baddouri and Hannig, who termed probiotic efficacy as potentially a “reality or illusion” given the mixed results and variability [57], complicates direct comparisons and the formulation of definitive clinical guidelines. Variations exist in:

ProbioticStrainsandCombinations: A wide array of Lactobacillus, Bifidobacterium, and Streptococcus strains are used, often in different combinations [2][49]. The efficacy is highly strain-specific [50].DosageandDuration: Probiotic interventions vary significantly in daily dosage, frequency, and duration of administration [49][51][53]. The observation from Choi & Park that longer interventions (≥6 months) demonstrated more consistent effects when standardized protocols were used further underscores this challenge [28].StudyDesignandPopulation: Variations in patient populations (e.g., specific periodontitis stages, systemic health status) and methodological rigor contribute to. The lack of consistent protocols for probiotic treatment prevents a single “correct protocol” from being established.

The cumulative evidence, both from our selected articles and additional reviews, supports the integration of probiotics as an adjunctive component in periodontal therapy. Their ability to improve clinical parameters, modulate the oral microbiome, and potentially reduce reliance on systemic antibiotics presents a valuable strategy for enhancing patient outcomes and promoting oral health. Personalized approaches, potentially integrating dietary interventions [53], show particular promise. However, clinicians should be aware of the existing heterogeneity and select probiotic interventions based on the best available strain-specific evidence.

To further solidify the role of probiotics in periodontal therapy, future research should prioritize:

StandardizationofProtocols: Conduct large-scale, well-designed randomized controlled trials with standardized probiotic strains, dosages, delivery methods, and treatment durations [50][54].Long-termEfficacy: Investigate the long-term effects of probiotic interventions, as current studies often have short follow-up periods, and some benefits may not be sustained [1]. Studies should measure effects at time points after final administration to determine the persistence of benefits [50].MechanismElucidation: Further explore the specific immunological and microbiological mechanisms through which different probiotic strains exert their effects, using advanced -omics technologies [53]. BiomarkerIdentification: Incorporate reliable biomarkers (e.g., inflammatory cytokines, specific microbial signatures) to objectively assess treatment response [53].PersonalizedMedicine: Explore how patient-specific factors, including genetic predispositions, systemic health, and dietary habits, influence probiotic efficacy to enable more personalized therapeutic strategies [53].PrebioticandPostbioticResearch: Investigate the efficacy of prebiotics alone or in combination with probiotics (synbiotics), and the potential of postbiotics in periodontal therapy. This direction is supported by Doucette etal., whose scoping review examined various prebiotics and probiotics as an adjunctive therapy for periodontal disease, highlighting gaps in current research [50].BroaderApplications: Further research into the role of probiotics in related oral health conditions like peri-implantitis could expand their therapeutic utility. This is suggested by findings within our included studies, such as Vives-Soler & Küstner, who observed a slight tendency toward better results in the probiotic group for peri-implant mucositis [8].