Issues related to peri-implant disease were discussed. It was observed that the most common lesions that occur, i.e. peri-implant mucositis and peri-implantitis are caused by bacteria. While the lesion of peri-implant mucositis resides in the soft tissues, periimplantitis also affects the supporting bone. Peri-implant mucositis occurs in about 80% of subjects (50% of sites) restored with implants, and peri-implantitis in between 28% and 56% of subjects (12-40% of sites). A number of risk indicators were identified including (i) poor oral hygiene, (ii) a history of periodontitis, (iii) diabetes and (iv) smoking. It was concluded that the treatment of peri-implant disease must include anti-infective measures. With respect to peri-implant mucositis, it appeared that non-surgical mechanical therapy caused the reduction in inflammation (bleeding on probing) but also that the adjunctive use of antimicrobial mouthrinses had a positive effect. It was agreed that the outcome of non-surgical treatment of peri-implantitis was unpredictable. The primary objective of surgical treatment in peri-implantitis is to get access to the implant surface for debridement and decontamination in order to achieve resolution of the inflammatory lesion. There was limited evidence that such treatment with the adjunctive use of systemic antibiotics could resolve a number of periimplantitis lesions. There was no evidence that so-called regenerative procedures had additional beneficial effects on treatment outcome.

The past decade of basic research in periodontology has driven radical changes in our understanding and perceptions of the pathogenic processes that drive periodontal tissue destruction. The core elements of the classical model of disease pathogenesis, developed by Page & Kornman in 1997, remain pertinent today; however, our understanding of the dynamic interactions between the various microbial and host factors has changed significantly. The molecular era has unraveled aspects of genetics, epigenetics, lifestyle and environmental factors that, in combination, influence biofilm composition and the host's inflammatory immune response, creating a heterogenic biological phenotype that we label as 'periodontitis'. In this volume of Periodontology 2000, experts in their respective fields discuss these emerging concepts, such as a health-promoting biofilm being essential for periodontal stability, involving a true symbiosis between resident microbial species and each other and also with the host response to that biofilm. Rather like the gut microbiome, changes in the local environment, which may include inflammatory response mediators or viruses, conspire to drive dysbiosis and create a biofilm that supports pathogenic species capable of propagating disease. The host response is now recognized as the major contributor to periodontal tissue damage in what becomes a dysfunctional, poorly targeted and nonresolving inflammation that only serves to nourish and sustain the dysbiosis. The role of epithelial cells in signaling to the immune system is becoming clearer, as is the role of dendritic cells as transporters of periodontal pathogens to distant sites within the body, namely metastatic infection. The involvement of nontraditional immune cells, such as natural killer cells, is being recognized, and the simple balance between T-helper 1- and T-helper 2-type T-cell populations has become less clear with the emergence of T-regulatory cells, T-helper 17 cells and follicular helper cells. The dominance of the neutrophil has emerged, not only as a potential destructor when poorly regulated but as an equally unpredictable effector cell for specific B-cell immunity. The latter has emerged, in part, from the realization that neutrophils live for 5.4 days in the circulation, rather than for 24 h, and are also schizophrenic in nature, being powerful synthesizers of proinflammatory cytokines but also responding to prostaglandin signals to trigger a switch to a pro-resolving phenotype that appears capable of regenerating the structure and function of healthy tissue. Key to these outcomes are the molecular signaling pathways that dominate at any one time, but even these are influenced by microRNAs capable of 'silencing' certain inflammatory genes. This volume of Periodontology 2000 tries to draw these complex new learnings into a contemporary model of disease pathogenesis, in which inflammation and dysbiosis impact upon whether the outcome is driven toward acute resolution and stability, chronic resolution and repair, or failed resolu...

Cellular Phenotype and Apoptosis: The function of epithelial tissues is the protection of the organism from chemical, microbial, and physical challenges which is indispensable for viability. To fulfill this task, oral epithelial cells follow a strongly regulated scheme of differentiation that results in the formation of structural proteins that manage the integrity of epithelial tissues and operate as a barrier. Oral epithelial cells are connected by various transmembrane proteins with specialized structures and functions. Keratin filaments adhere to the plasma membrane by desmosomes building a three-dimensional matrix. Cell-Cell Contacts and Bacterial Influence: It is known that pathogenic oral bacteria are able to affect the expression and configuration of cell-cell junctions. Human keratinocytes up-regulate immune-modulatory receptors upon stimulation with bacterial components. Periodontal pathogens including P. gingivalis are able to inhibit oral epithelial innate immune responses through various mechanisms and to escape from host immune reaction, which supports the persistence of periodontitis and furthermore is able to affect the epithelial barrier function by altering expression and distribution of cell-cell interactions including tight junctions (TJs) and adherens junctions (AJs). In the pathogenesis of periodontitis a highly organized biofilm community shifts from symbiosis to dysbiosis which results in destructive local inflammatory reactions. Cellular Receptors: Cell-surface located toll like receptors (TLRs) and cytoplasmatic nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) belong to the pattern recognition receptors (PRRs). PRRs recognize microbial parts that represent pathogen-associated molecular patterns (PAMPs). A multimeric complex of proteins known as inflammasome, which is a subset of NLRs, assembles after activation and proceeds to pro-inflammatory cytokine release. Cytokine Production and Release: Cytokines and bacterial products may lead to host cell mediated tissue destruction. Keratinocytes are able to produce diverse pro-inflammatory cytokines and chemokines, including interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor (TNF)-α. Infection by pathogenic bacteria such as Porphyromonas gingivalis ( P. gingivalis ) and Aggregatibacter actinomycetemcomitans ( A. actinomycetemcomitans ) can induce a differentiated production of these cytokines. Immuno-modulation, Bacterial Infection, and Cancer Cells: There is a known association between bacterial infection and cancer. Bacterial components are able to up-regulate immune-modulatory receptors on cancer cells. Interactions of bacteria with tumor cells could support malignant transformation an environment with deficient immune regulation. The aim of this review is...

AimWe investigated the long‐term impact of adjunctive systemic antibiotics on periodontal disease progression. Periodontal therapy is frequently supplemented by systemic antibiotics, although its impact on the course of disease is still unclear.Material & MethodsThis prospective, randomized, double‐blind, placebo‐controlled multi‐centre trial comprising patients suffering from moderate to severe periodontitis evaluated the impact of rational adjunctive use of systemic amoxicillin 500 mg plus metronidazole 400 mg (3x/day, 7 days) on attachment loss. The primary outcome was the percentage of sites showing further attachment loss (PSAL) ≥1.3 mm after the 27.5 months observation period. Standardized therapy comprised mechanical debridement in conjunction with antibiotics or placebo administration, and maintenance therapy at 3 months intervals.ResultsFrom 506 participating patients, 406 were included in the intention to treat analysis. Median PSAL observed in placebo group was 7.8% compared to 5.3% in antibiotics group (Q25 4.7%/Q75 14.1%; Q25 3.1%/Q75 9.9%; p < 0.001 respectively).ConclusionsBoth treatments were effective in preventing disease progression. Compared to placebo, the prescription of empiric adjunctive systemic antibiotics showed a small absolute, although statistically significant, additional reduction in further attachment loss. Therapists should consider the patient's overall risk for periodontal disease when deciding for or against adjunctive antibiotics prescription.