[The relationship between oral microbiota and taste]. / De relatie tussen mondmicrobiota en smaak.

Disruption of the perception of taste can have severe consequences on general health. Although evidence suggests that the oral microbiota plays a role in taste perception, little is known about this possible influence. In this scoping review, the influence of oral microbiota on taste perception was studied. Current scientific literature is heterogeneous in study methods and study populations, which impedes comparison of results. Although the findings of this review provide insufficient evidence to confirm the influence of oral microbiota on taste perception, some results show a relationship between taste perception and specific microorganisms. Several factors play a role in taste perception, including tongue coating, use of medication, advanced age, and decreased salivary flow rate, and when these factors are present, it is important to be alert to possible changes in taste. Large-scale studies, in which the multifactorial etiology of taste perception is addressed, are needed to clarify the role of the oral microbiota on taste perception.

[Periodontitis - infection or inflammation?] / Parodontitis; infectie of ontsteking?

Periodontitis is a complex, multifactorial disease. Multiple factors such as (epi)genetic factors, environmental factors (microbial biofilm), lifestyle (smoking, stress) and general health (diabetes mellitus) contribute to the development of periodontitis. A healthy subgingival microbiome is in balance with its host, is very stable and diverse, and keeps the host healthy. Changes, such as declining oral hygiene, lead to changes in the microbial composition in the subgingival sulcus: anaerobic and protein-degrading microorganisms with pro-inflammatory properties increase in number and disturb the proportions, leading in turn to changes in the subgingival environment and an increase in pro-inflammatory microorganisms. If the first line of the immune system is unable to restore subgingival equilibrium, microorganisms and their products invade the periodontal soft tissues, resulting in activation of osteoclasts and, ultimately, in the destruction of the periodontium and the onset of periodontitis.

A reproducible microcosm biofilm model of subgingival microbial communities.

OBJECTIVE: To develop a reproducible subgingival microcosm biofilm model. MATERIAL AND METHODS: Subgingival plaque samples were collected from four deep pockets (probing pocket depth ≥6 mm) in each of seven patients with periodontitis and from shallow pockets (probing pocket depth ≤3 mm) in two periodontally healthy donors. An active attachment model and a peptone medium (Thompson et. al., Appl Environ Microbiol 2015;81:8307-8314) supplemented with 30% serum was used. Biofilms were harvested at 2 and 4 weeks. DNA of dead cells was blocked for amplification by propidium monoazide treatment. Composition was analyzed using 16S rRNA gene amplicon pyrosequencing. Similarities between the biofilm samples were assessed by non-metric multidimensional scaling using the Bray-Curtis similarity index and similarity percentage analysis. Data from duplicate experiments, different biofilm sources and different biofilm age were compared. RESULTS: The non-metric multidimensional scaling revealed a strong clustering by the inoculum source, the donor and their periodontal status. Statistically significant differences were found between the sources of inoculum (P=.0001) and biofilm age (P=.0016). Furthermore, periodontitis biofilms (P) were distinct in composition from health-derived biofilms (H) by genera: Porphyromonas (P=19%; H=0%), Filifactor (P=10%; H=0%), Anaeroglobus (P=3%; H=0%), Phocaeicola (P=1.5%; H=0%), Parvimonas (P=19%; H=14%), Fusobacterium (P=2%; H=26%), Peptostreptococcus (P=20%; H=30%), Veillonella (P=7%; H=8%) and 57 other genera. Similarity distances (Bray-Curtis) (mean 0.73, SD 0.15) and the Shannon diversity index (mean 2, SD 0.2) revealed no differences between duplicate experiments (P=.121). CONCLUSION: This biofilm model allows reproducible production of complex subgingival microbial communities.

The effect of propidium monoazide treatment on the measured bacterial composition of clinical samples after the use of a mouthwash.

OBJECTIVES: The use of an anti-microbial mouthwash results not only in a reduction of the number of viable cells in dental plaque but potentially also in a shift in the oral microbiome. DNA-based techniques may be appropriate to monitor these shifts, but these techniques amplify DNA from both dead and living cells. Propidium monoazide (PMA) has been used to overcome this problem, by preventing the amplification of DNA from membrane-damaged cells. The aim of this study was to evaluate the use of PMA when measuring compositional shifts in clinical samples after mouthwash use. MATERIALS AND METHODS: On two consecutive days, baseline samples from buccal surfaces, tongue, and saliva were obtained from six volunteers, after which they used a mouthwash (Meridol, GABA, Switzerland) twice daily for 14 days. Subsequently similar samples were obtained on two consecutive days. The microbial composition of the samples, with or without ex vivo PMA treatment, was assessed with 16S rRNA gene amplicon sequencing. RESULTS: Data showed a clear effect of mouthwash usage on the tongue and saliva samples. PMA treatment enhanced the observed differences only for the saliva samples. Mouthwash treatments did not affect the composition of the plaque samples irrespective of the use of PMA. CONCLUSION: The necessity to use a PMA treatment to block the DNA from dead cells in clinical studies aimed at measuring compositional shifts after the use of a mouthwash is limited to salivary samples. CLINICAL RELEVANCE: Measuring shifts in the oral microbiome could be hampered by the presence of DNA from dead cells.

The effects of propidium monoazide treatment on the measured composition of polymicrobial biofilms after treatment with chlorhexidine.

BACKGROUND: The treatment of polymicrobial biofilms with antimicrobial compounds results in not only an overall loss of viability, but also compositional shifts. While DNA-based technologies may be more appropriate for the assessment of bacterial composition than culturing, these techniques amplify DNA from both live and dead cells. Propidium monoazide (PMA) has been used to discriminate between live and dead cells by blocking the DNA from membrane-damaged cells from being amplified. AIM: This study evaluated the use of PMA in a saliva-derived polymicrobial biofilm model subjected to a single chlorhexidine (CHX) treatment. MATERIALS AND METHODS: The effects of PMA on viable cells were tested using both untreated and PMA-treated saliva as an inoculum. Viability was determined by plate counts, metabolic activity was determined by lactic acid production, and biofilm composition was assessed by 16S rRNA gene amplicon sequencing. RESULTS: Exposure to a 0.2% CHX rinse (meridol® perio) reduced the viability and metabolic activity of 48-hour biofilms. The shift in biofilm composition observed after the CHX exposure was enhanced after a post-rinse PMA treatment. PMA treatment had a small effect on the measured composition of water-rinsed biofilms. Treating saliva with PMA reduced bacterial viability and shifted the bacterial composition of saliva and saliva-derived biofilms. CONCLUSION: The removal of DNA from non-viable cells with PMA treatment was shown to elicit an improvement in the detection of shifts in in vitro polymicrobial biofilms after antimicrobial treatment. However, PMA also influenced the ability of cells to grow, indicating that PMA should be used with caution.

Microbial Indicators of Dental Health, Dysbiosis, and Early Childhood Caries.

Dental caries lesions are a clinical manifestation of disease, preceded by microbial dysbiosis, which is poorly characterized and thought to be associated with saccharolytic taxa. Here, we assessed the associations between the oral microbiome of children and various caries risk factors such as demographics and behavioral and clinical data across early childhood and characterized over time the salivary and dental plaque microbiome of children before clinical diagnosis of caries lesions. Children (N = 266) were examined clinically at ~1, 2.5, 4, and 6.5 y of age. The microbiome samples were collected at 1, 2.5, and 4 y. Caries groups consisted of children who remained caries free (International Caries Detection and Assessment System [ICDAS] = 0) at all time points (CFAT) (n = 50); children diagnosed with caries (ICDAS ≥ 1) at 6.5 y (C6.5), 4 y (C4), or 2.5 y of age (C2.5); and children with early caries or advanced caries lesions at specific time points. Microbial community analyses were performed on zero-radius operational taxonomic units (zOTUs) obtained from V4 of 16S ribosomal RNA gene amplicon sequences. The oral microbiome of the children was affected by various factors, including antibiotic use, demographics, and dietary habits of the children and their caregivers. At all time points, various risk factors explained more of the variation in the dental plaque microbiome than in saliva. At 1 y, composition of saliva of the C4 group differed from that of the CFAT group, while at 2.5 y, this difference was observed only in plaque. At 4 y, multiple salivary and plaque zOTUs of genera Prevotella and Leptotrichia were significantly higher in samples of the C6.5 group than those of the CFAT group. In conclusion, up to 3 y prior to clinical caries detection, the oral microbial communities were already in a state of dysbiosis that was dominated by proteolytic taxa. Plaque discriminated dysbiotic oral ecosystems from healthy ones better than saliva.

Evaluation of plant and fungal extracts for their potential antigingivitis and anticaries activity.

The link between diet and health has lead to the promotion of functional foods which can enhance health. In this study, the oral health benefits of a number of food homogenates and high molecular mass and low molecular mass fractions were investigated. A comprehensive range of assays were performed to assess the action of these foods on the development of gingivitis and caries using bacterial species associated with these diseases. Both antigingivitis and anticaries effects were investigated by assays examining the prevention of biofilm formation and coaggregation, disruption of preexisting biofilms, and the foods' antibacterial effects. Assays investigating interactions with gingival epithelial cells and cytokine production were carried out to assess the foods' anti- gingivitis properties. Anti-caries properties such as interactions with hydroxyapatite, disruption of signal transduction, and the inhibition of acid production were investigated. The mushroom and chicory homogenates and low molecular mass fractions show promise as anti-caries and anti-gingivitis agents, and further testing and clinical trials will need to be performed to evaluate their true effectiveness in humans.

Ecology of the microbiome of the infected root canal system: a comparison between apical and coronal root segments.

AIM: To evaluate the microbial ecology of the coronal and apical segments of infected root canal systems using a complete sampling technique and next-generation sequencing. METHODOLOGY: The roots of 23 extracted teeth with apical periodontitis were sectioned in half, horizontally, and cryo-pulverized. Bacterial communities were profiled using tagged 454 pyrosequencing of the 16S rDNA hypervariable V5-V6 region. RESULTS: The sequences were classified into 606 taxa (species or higher taxon), representing 24 bacterial phyla or candidate divisions and one archaeal phylum. Proteobacteria were more abundant in the apical samples (P < 0.05), whilst Actinobacteria were in significantly higher proportions in the coronal samples. The apical samples harboured statistically significantly more taxa than the coronal samples (P = 0.01) and showed a higher microbial diversity. Several taxa belonging to fastidious obligate anaerobes were significantly more abundant in the apical segments of the roots compared with their coronal counterparts. CONCLUSIONS: Endodontic infections are more complex than reported previously. The apical part of the root canal system drives the selection of a more diverse and more anaerobic community than the coronal part. The presence of a distinct ecological niche in the apical region explains the difficulty of eradication of the infection and emphasizes the need for new treatment approaches to be developed.

Next-generation sequencing approaches to understanding the oral microbiome.

Until recently, the focus in dental research has been on studying a small fraction of the oral microbiome-so-called opportunistic pathogens. With the advent of next-generation sequencing (NGS) technologies, researchers now have the tools that allow for profiling of the microbiomes and metagenomes at unprecedented depths. The major advantages of NGS are the high throughput and the fact that specific taxa do not need to be targeted. The relatively low cost and the availability of sequencing facilities have contributed to nearly exponential growth of NGS datasets. The quality and interpretation of the NGS data could be undermined at numerous steps-from sample collection, storage, and DNA extraction to PCR bias, sequencing errors, choice of algorithms for data processing, and statistical analyses. Making sense out of this data deluge is and will be the major challenge. The community analyses based on systems ecology principles will bring us closer to an understanding of the underlying forces that facilitate the stability (or imbalance) of the microbiome. The next logical step will take us beyond the microbiome. The integration of bacterial, viral, fungal "meta-omes" such as the meta-transcriptome, meta-proteome, and meta-metabolome, together with the host as a major co-factor, should be the ultimate goal in unraveling the complexity of the oral interactome.

The numerous microbial species in oral biofilms: how could antibacterial therapy be effective?

Hundreds of bacterial species inhabit the oral cavity. Many of these have never been cultivated and can be assessed only with DNA-based techniques. This new understanding has changed the paradigm of the etiology of oral disease from that associated with 'traditional pathogens' as being primarily responsible for all diseases. Increasingly, associations between oral bacteria and systemic diseases are being reported. The emergence of antibiotic resistance is alarming and calls for in-depth studies of biofilms, bacterial physiology, and a body-wide approach to infectious diseases. We propose that the borderline between commensal bacteria and pathogens is no longer discrete. In a field of science where so many of the established paradigms are being undermined, a thorough analysis of threats and opportunities is required. This article addresses some of the questions that can be raised and serves to identify research opportunities and needs to leverage the prevention of oral diseases through novel antimicrobial strategies.

Oral Microbiome Transmission and Infant Feeding Habits.

Transmission of oral microbiota from mother to infant is a highly relevant and, so far, understudied topic due to lack of mainstream high-throughput methods for the assessment of bacterial diversity at a strain level. In their recent article in mBio, S. Kageyama, M. Furuta, T. Takeshita, J. Ma, et al. (mBio 13:e03452-21, 2021, https://doi.org/10.1128/mbio.03452-21) evaluated oral microbial transmission from mothers to their infants by using full-length analysis of the 16S rRNA gene and demonstrated the applicability of this method for assessment of transmission of oral bacteria at the single-nucleotide-difference level. By analyzing different metadata of the mother-infant pairs, they discovered that the presence of maternal oral bacteria was higher in formula-fed infants compared to infants who were breastfed or received mixed feeding. This interesting finding suggests that breastfeeding may prevent early maturation of infant's oral microbiome. The physiological role of this phenomenon still needs to be elucidated.

The Importance of Nitrate Reduction for Oral Health.

Salivary glands concentrate plasma nitrate into saliva, leading to high nitrate concentrations that can reach the millimolar range after a nitrate-rich vegetable meal. Whereas human cells cannot reduce nitrate to nitrite effectively, certain oral bacteria can. This leads to an increase in systemic nitrite that can improve conditions such as hypertension and diabetes through nitric oxide availability. Apart from systemic benefits, it has been proposed that microbial nitrate reduction can also promote oral health. In this review, we discuss evidence associating dietary nitrate with oral health. Oral bacteria can reduce nitrite to nitric oxide, a free radical with antimicrobial properties capable of inhibiting sensitive species such as anaerobes involved in periodontal diseases. Nitrate has also been shown to increase resilience against salivary acidification in vivo and in vitro, thus preventing caries development. One potential mechanism is proton consumption during denitrification and/or bacterial reduction of nitrite to ammonium. Additionally, lactic acid (organic acid involved in oral acidification) and hydrogen sulfide (volatile compound involved in halitosis) can act as electron donors for these processes. The nitrate-reducing bacteria Rothia and Neisseria are consistently found at higher levels in individuals free of oral disease (vs. individuals with caries, periodontitis, and/or halitosis) and increase when nitrate is consumed in clinical studies. Preliminary in vitro and clinical evidence show that bacteria normally associated with disease, such as Veillonella (caries) and Prevotella (periodontal diseases and halitosis), decrease in the presence of nitrate. We propose nitrate as an ecologic factor stimulating eubiosis (i.e., an increase in health-associated species and functions). Finally, we discuss the preventive and therapeutic potential, as well as safety issues, related to the use of nitrate. In vivo evidence is limited; therefore, robust clinical studies are required to confirm the potential benefits of nitrate reduction on oral health.

Home sampling is a feasible method for oral microbiota analysis for infants and mothers.

OBJECTIVES: Large longitudinal cohort studies in infants are needed to understand oral microbiome maturation in relation to general health. The logistics of such studies are complex and costs involved high. Methods like home sampling by caretakers might be a solution to these issues. This study aimed to evaluate feasibility of home sampling by caretakers and to assess which oral niche provides the most reliable sample. METHODS: In this cross-sectional study 30 mothers and their infants aged 2-15 months participated. Swabs of the tongue, buccal mucosa, saliva, and dental plaque of the mother and the infant were collected by the mother after watching an instruction video. Thereafter, the trained researcher repeated the sample collection. Variations on the sampling protocol were listed. Bacterial DNA was quantified and microbial composition was assessed using 16S rDNA amplicon sequencing. RESULTS: None of the sampled niches appeared to be unfeasible based on interviews and observed variations on protocol. No significant differences in bacterial DNA concentration between operators (mother and researcher) were found. In infant's saliva, Shannon diversity of samples collected by the researcher was significantly higher than those collected by mothers (p = 0.0009) and the bacterial composition was influenced by variations on sampling protocol (p = 0.01). CONCLUSIONS: Home sampling by caretakers is a feasible method for oral sample collection in infants and mothers. Oral samples collected by mothers resemble samples collected by a trained researcher, with the tongue sample being the most similar and saliva the least. CLINICAL SIGNIFICANCE: Home sampling can simplify longitudinal oral microbiota collection.

Maturation of the Oral Microbiome in Caries-Free Toddlers: A Longitudinal Study.

Understanding the development of the oral microbiota in healthy children is of great importance to oral and general health. However, limited data exist on a healthy maturation of the oral microbial ecosystem in children. Moreover, the data are biased by mislabeling "caries-free" populations. Therefore, we aimed to characterize the healthy salivary and dental plaque microbiome in young children. Caries-free (ICDAS [International Caries Detection and Assessment System] score 0) children (n = 119) and their primary caregivers were followed from 1 until 4 y of child age. Salivary and dental plaque samples were collected from the children at 3 time points (T1, ~1 y old; T2, ~2.5 y old; and T3, ~4 y old). Only saliva samples were collected from the caregivers. Bacterial V4 16S ribosomal DNA amplicons were sequenced using Illumina MiSeq. The reads were denoised and mapped to the zero-radius operational taxonomic units (zOTUs). Taxonomy was assigned using HOMD. The microbial profiles of children showed significant differences (P = 0.0001) over time. Various taxa increased, including Fusobacterium, Actinomyces, and Corynebacterium, while others showed significant decreases (e.g., Alloprevotella and Capnocytophaga) in their relative abundances over time. Microbial diversity and child-caregiver similarity increased most between 1 and 2.5 y of age while still not reaching the complexity of the caregivers at 4 y of age. The microbiome at 1 y of age differed the most from those at later time points. A single zOTU (Streptococcus) was present in all samples (n = 925) of the study. A large variation in the proportion of shared zOTUs was observed within an individual child over time (2% to 42% of zOTUs in saliva; 2.5% to 38% in dental plaque). These findings indicate that the oral ecosystem of caries-free toddlers is highly heterogeneous and dynamic with substantial changes in microbial composition over time and only few taxa persisting across the 3 y of the study. The salivary microbiome of 4-y-old children is still distinct from that of their caregivers.

Effects of ozone and sodium hypochlorite on caries-like lesions in dentin.

The hypothesis that ozone promotes remineralization of dentinal lesions was tested in vitro. Artificial caries-like lesions in dentin were treated with ozone gas, with another potent oxidizer (sodium hypochlorite, NaOCl, 10%) or with water. The specimens were then remineralized and subsequently demineralized again. Mineral content was assessed by transverse microradiography. NaOCl-treated samples showed damaged surface and, after being remineralized, demineralized significantly more than water- or ozone-treated groups. No difference was found between ozone and water groups. The exposure to ozone had thus no effect on remineralization and subsequent demineralization of remineralized dentinal lesions.

Second Era of OMICS in Caries Research: Moving Past the Phase of Disillusionment.

Novel approaches using OMICS techniques enable a collective assessment of multiple related biological units, including genes, gene expression, proteins, and metabolites. In the past decade, next-generation sequencing ( NGS) technologies were improved by longer sequence reads and the development of genome databases and user-friendly pipelines for data analysis, all accessible at lower cost. This has generated an outburst of high-throughput data. The application of OMICS has provided more depth to existing hypotheses as well as new insights in the etiology of dental caries. For example, the determination of complete bacterial microbiomes of oral samples rather than selected species, together with oral metatranscriptome and metabolome analyses, supports the viewpoint of dysbiosis of the supragingival biofilms. In addition, metabolome studies have been instrumental in disclosing the contributions of major pathways for central carbon and amino acid metabolisms to biofilm pH homeostasis. New, often noncultured, oral streptococci have been identified, and their phenotypic characterization has revealed candidates for probiotic therapy. Although findings from OMICS research have been greatly informative, problems related to study design, data quality, integration, and reproducibility still need to be addressed. Also, the emergence and continuous updates of these computationally demanding technologies require expertise in advanced bioinformatics for reliable interpretation of data. Despite the obstacles cited above, OMICS research is expected to encourage the discovery of novel caries biomarkers and the development of next-generation diagnostics and therapies for caries control. These observations apply equally to the study of other oral diseases.

Caries Incidence in a Healthy Young Adult Population in Relation to Diet.

In the past, epidemiological studies focused on cavitated stages of caries. The arrival of the International Caries Detection and Assessment System (ICDAS) in 2004 allowed for clinical measurements of the initial stages of enamel caries. However, since the introduction, most studies applying the ICDAS still have studied the diseased population. The objective of this cross-sectional observational study was to describe early enamel caries in a large healthy young adult population and determine the relationship with diet and oral hygiene measures. The study population consisted of 268 healthy participants without frank cavitation. The examinations were done visually and radiographically using ICDAS on all tooth surfaces. In total, 8.6% of the surfaces (occlusal > approximal > smooth) had caries, of which 92.0% were confined to enamel (28.5% ICDAS score 1, 54.0% score 2, 8.6% score 3). Thirteen percent of the occlusal and 63% of the approximal caries were found with radiography. Thus, radiography is quintessential for the diagnosis of approximal enamel lesions. We found a positive correlation between enamel caries (ICDAS 1 to 3) and the consumption of mono- and disaccharides and carbohydrates ( r = 0.226 and r = 0.188, respectively, both P < 0.01), as well as a negative correlation with alcohol consumption ( r = -0.202, P < 0.01). There was also a positive correlation between enamel caries and the energy intake from mono- and disaccharides (sugar kJ, r = 0.206, P < 0.01), which was independent of body mass index. Only 11 participants consumed less than 10% of total energy as sugar kJ, which is the recommended percentage of kJ from free sugar by the World Health Organization. No clear correlation was found with oral hygiene. In conclusion, in this healthy young adult population, caries was found in 97.8% of the subjects, mostly initial enamel caries (ICDAS 1 to 2) in the occlusal surface of molars, and was related with dietary factors.

[Dentin demineralization in situ during frequent exposures to bananas or sucrose]. / Demineralisatie van dentine in situ bij veelvuldige blootstelling aan sacharose of banaan.

The aim of the study was to compare sucrose solution and bananas on demineralizing potential in situ, and to address the question if fluoride toothpaste is equally effective in preventing dentin demineralization at open, smooth surfaces and at plaque stagnation sites (grooves). Four volunteers wore an appliance containing bovine dentin specimens with narrow grooves and a smooth surface for two 1-week in situ periods, with 8 1-minute exposures daily: either by a rinse with 10% sucrose, or by consumption of a piece of banana. Twice daily, the appliance was dipped in toothpaste slurry of a fluoride-free toothpaste at one side and a fluoride toothpaste at the contralateral side. Demineralization was assessed by tranversal microradiography. No difference in dentin demineralization was found after frequent exposure to either sucrose solution or bananas. Fluoride toothpaste effectively protected dentin only at the smooth surfaces. In the grooves, fluoride affected the demineralization pattern; it drove lesions towards the bottom of the groove.

The oral microbiome - an update for oral healthcare professionals.

For millions of years, our resident microbes have coevolved and coexisted with us in a mostly harmonious symbiotic relationship. We are not distinct entities from our microbiome, but together we form a 'superorganism' or holobiont, with the microbiome playing a significant role in our physiology and health. The mouth houses the second most diverse microbial community in the body, harbouring over 700 species of bacteria that colonise the hard surfaces of teeth and the soft tissues of the oral mucosa. Through recent advances in technology, we have started to unravel the complexities of the oral microbiome and gained new insights into its role during both health and disease. Perturbations of the oral microbiome through modern-day lifestyles can have detrimental consequences for our general and oral health. In dysbiosis, the finely-tuned equilibrium of the oral ecosystem is disrupted, allowing disease-promoting bacteria to manifest and cause conditions such as caries, gingivitis and periodontitis. For practitioners and patients alike, promoting a balanced microbiome is therefore important to effectively maintain or restore oral health. This article aims to give an update on our current knowledge of the oral microbiome in health and disease and to discuss implications for modern-day oral healthcare.

Microbial profiles at baseline and not the use of antibiotics determine the clinical outcome of the treatment of chronic periodontitis.

Antibiotics are often used in the treatment of chronic periodontitis, which is a major cause of tooth loss. However, evidence in favour of a microbial indication for the prescription of antibiotics is lacking, which may increase the risk of the possible indiscriminate use of antibiotics, and consequent, microbial resistance. Here, using an open-ended technique, we report the changes in the subgingival microbiome up to one year post-treatment of patients treated with basic periodontal therapy with or without antibiotics. Antibiotics resulted in a greater influence on the microbiome 3 months after therapy, but this difference disappeared at 6 months. Greater microbial diversity, specific taxa and certain microbial co-occurrences at baseline and not the use of antibiotics predicted better clinical treatment outcomes. Our results demonstrate the predictive value of specific subgingival bacterial profiles for the decision to prescribe antibiotics in the treatment of periodontitis, but they also indicate the need for alternative therapies based on ecological approaches.