ACES: A new framework for the application of the 2018 periodontal status classification scheme to epidemiological survey data.

AIM: To propose a framework for consistently applying the 2018 periodontal status classification scheme to epidemiological surveys (Application of the 2018 periodontal status Classification to Epidemiological Survey data, ACES). PROPOSED FRAMEWORK: We specified data requirements and workflows for either completed or planned epidemiological surveys, utilizing commonly collected measures of periodontal status (clinical attachment levels [CAL], probing depths, bleeding on probing), as well as additional necessary variables for the implementation of the 2018 periodontal status classification (tooth loss due to periodontitis and complexity factors). Following detailed instructions and flowcharts, survey participants are classified as having periodontal health, gingivitis or periodontitis. Rates of edentulism must also be reported. In cases of periodontitis, instructions on how to compute the stage and extent are provided. Assessment of grade can be derived from CAL measurements (or from radiographic alveolar bone loss data) in relation to root length and the participant's age. CONCLUSIONS: ACES is a framework to be used in epidemiological studies of periodontal status that (i) have been completed, and in which stage and grade according to the 2018 classification are inferred retroactively, or (ii) are being planned. Consistent use of the proposed comprehensive approach will facilitate the comparability of periodontitis prevalence estimates across studies.

Diagnostic reproducibility of the 2018 Classification of Gingival Recession Defects and Gingival Phenotype: A multicenter inter- and intra-examiner agreement study.

BACKGROUND: The aim of this study was to investigate the inter- and intra-examiner agreement among international experts on the diagnosis of gingival recession defects using the 2018 Classification of Gingival Recession Defects and Gingival Phenotype as proposed in the 2017 World Workshop. METHODS: Standardized intraoral photographs from 28 gingival recession defects were evaluated twice by 16 expert periodontists. Recession type (RT), recession depth (RD), keratinized tissue width (KTW), gingival thickness (GT), detectability of the cemento-enamel junction (CEJ), and presence of root steps (RS) were recorded and used for the analysis. Intra- and inter-examiner agreements were calculated for individual variables and for the overall classification. Intraclass correlation coefficient with 95% CI was used for RD and KTW; Kappa with 95% CI was used for GT, CEJ, and RS; quadratic weighted Kappa with 95% CI was used for RT. RESULTS: Overall intra- and inter-examiner agreements were highest for KTW (0.95 and 0.90), lowest for GT (0.75 and 0.41), with the other variables in between (RD: 0.93 and 0.68, RS: 0.87 and 0.65, RT: 0.79 and 0.64, CEJ: 0.75 and 0.57). Overall intra- and inter-examiner agreements for the matrix were 62% and 28%, respectively. Significant effects existed between one variable's measurement and other variables' agreements. CONCLUSIONS: The 2018 Classification of Gingival Recession Defects and Gingival Phenotype is clinically reproducible within the examiners, and when the variables forming the matrix are analyzed individually. The between-examiner agreement for the complete matrix showed lower reproducibility. The agreement was highest for KTW and RD, and least for GT.

Agreement among international periodontal experts using the 2017 World Workshop classification of periodontitis.

BACKGROUND: A new periodontitis classification was recently introduced involving multidimensional staging and grading. The aim of the study was to assess if individuals well-trained in periodontics consistently used the new classification for patients with severe periodontitis. The secondary goal was to identify "gray zones" related to classifications. METHODS: Participants (raters) individually classified 10 pre-selected severe periodontitis cases using the 2017 World Workshop classification. An internet case-based study was conducted after inviting members from American Academy of Periodontology and European Federation of Periodontology. Gold-standard diagnoses were determined by five experts who developed the new periodontitis classification. Inter-reliability agreement among raters was assessed using Fleiss Kappa index with the jackknife method for linearly weighted kappa calculations. McNemar test was used to determine symmetry between raters and gold-standard panel. RESULTS: A total of 103 raters participated and classified nine clinical cases. Fleiss Kappa values showed moderate inter-examiner consistency among raters for stage (K value: 0.49; 95% CI, 0.19 to 0.79), grade (K value: 0.50; 95% CI, 0.30 to 0.70) and extent (K value: 0.51; 95% CI, 0.23 to 0.77). When analyzed as composite (stage, grade, extent) a moderate inter-reliability was present among raters, k = 0.479 (K value: 0.47; 95% CI, 0.442 to 0.515). Agreement between raters and gold-standard panel was staging 76.6%; grading 82%; and extent 84.8%. In six of nine cases 77% to 99% of raters consistently agreed with gold-standard panel, and the other three cases had gray zone factors that reduced rater consistency. CONCLUSIONS: Clinicians trained in the 2017 World Workshop periodontitis classification demonstrated moderate concordance in classifying nine severe periodontitis cases, and in six of nine cases raters consistently agreed with the gold-standard panel.

Machine learning-assisted immune profiling stratifies peri-implantitis patients with unique microbial colonization and clinical outcomes.

Rationale: The endemic of peri-implantitis affects over 25% of dental implants. Current treatment depends on empirical patient and site-based stratifications and lacks a consistent risk grading system. Methods: We investigated a unique cohort of peri-implantitis patients undergoing regenerative therapy with comprehensive clinical, immune, and microbial profiling. We utilized a robust outlier-resistant machine learning algorithm for immune deconvolution. Results: Unsupervised clustering identified risk groups with distinct immune profiles, microbial colonization dynamics, and regenerative outcomes. Low-risk patients exhibited elevated M1/M2-like macrophage ratios and lower B-cell infiltration. The low-risk immune profile was characterized by enhanced complement signaling and higher levels of Th1 and Th17 cytokines. Fusobacterium nucleatum and Prevotella intermedia were significantly enriched in high-risk individuals. Although surgery reduced microbial burden at the peri-implant interface in all groups, only low-risk individuals exhibited suppression of keystone pathogen re-colonization. Conclusion: Peri-implant immune microenvironment shapes microbial composition and the course of regeneration. Immune signatures show untapped potential in improving the risk-grading for peri-implantitis.

Diagnosis of Stage III Periodontitis and Ambiguities of the "Gray Zones" in Between Stage III and Stage IV.

INTRODUCTION: How to best classify the Stage III and IV periodontitis cases that share common features of the most severe clinical attachment loss and the most severe radiographic bone loss? CASE PRESENTATION: Two patients presented features of generalized periodontitis, with severe probing depth and clinical attachment loss that would meet inclusion in both Stage III and IV. The cases retained all teeth but were further complicated by teeth drifting and secondary occlusal trauma. Appropriate disease classification required clinical judgement and led to the final classification of Stage III, Grade C for both cases. CONCLUSION: Patient-based clinical judgement, aiming for long-term preservation of natural dentition, drives the final assignment of staging when the case falls in the "gray zone" that focuses on major differences in Stage III and IV periodontitis.

Using business intelligence and data visualization to understand the characteristics of failed appointments in dental school clinics.

PURPOSE/OBJECTIVES: Broken appointments are an important cause of waste in health care. Patients who fail to attend incur costs to providers, deny trainees learning opportunities, and impact their own health as well as that of other patients who are waiting for care. METHODS: A total of 410,000 appointment records over 3 years were extracted from our electronic health record. We conducted exploratory data analysis and assessed correlations between appointment no-shows and other attributes of the appointment and the patient. The University of Michigan Medical School's Committee on Human Research reviewed the study and deemed that no Institutional Review Board oversight was necessary for this quality improvement project that was, retrospectively, turned into a study with previously de-identified data. RESULTS: The patient's previous attendance record is the single most significant correlation with attendance. We found that patients who said they are "scared" of dental visits were 62% as likely to attend as someone reporting "no problem." Patients over 65 years of age have better attendance rates. There was a positive association between receiving email/text confirmation and attendance. A total of 94.9% of those emailed a reminder and 92.2% of those who were texted attended their appointment. CONCLUSION(S): We were able to identify relationships of several variables to failed and attended appointments that we were previously unknown to us. This knowledge enabled us to implement interventions to support better attendance at Dental Clinics at the University of Michigan, improving patient health, student training, and efficient use of resources.

Staging and Grading Discussion of Borderline Cases in Gray Zones.

INTRODUCTION: Staging and grading for chronic periodontal disease, as described in 2018, is designed to focus on key distinctions with the recognition that there is a subset of individuals who are on a different clinical trajectory of disease. The staging and grading framework aids the clinician in generating a periodontal diagnosis, however, some cases fall into gray zones in which the simple diagnostic parameters make it challenging to categorize the patient. These cases do not present with clear clinical findings and medical and dental histories that fit within the simple guidelines defined in the staging and grading tables and subsequent algorithms. CASE PRESENTATION: Two cases are presented and demonstrate typical clinical scenarios that fall into gray zones when it comes to differentiating whether the patient will respond predictably to standard principles of care. Case 1 presents a scenario in which the patient's early history suggests the potential for disease progression and increases the likelihood that the patient may develop a need for complex rehabilitation due to periodontal breakdown. Clinical judgment was used to evaluate whether the patient remained at elevated risk and the potential implications for disease progression. Case 1 was diagnosed with generalized Stage III, Grade B. The initial presentation of Case 2 had a higher severity and complexity and therefore was diagnosed with generalized Stage IV, Grade C. The need for complex rehabilitation in Case 2, however, was not primarily due to periodontitis. CONCLUSION: Decision guidelines and algorithms help in establishing a standardized diagnosis, however cases that fall into gray zones require clinical judgment to establish the most appropriate diagnosis to guide a treatment plan that is personalized based on current knowledge.

Challenges and Decision Making for the Classification of Two Complex Periodontal Cases.

FOCUSED CLINICAL QUESTION: What are the fundamental debates and questions related to the newly developed two-vector system for classification of periodontal diseases that have emerged as to how to accurately assign, stage, and grade periodontitis cases? The aim of the present manuscript is to demonstrate the essential thought processes that are needed in utilizing the new periodontitis classification system to diagnose two gray zone cases. SUMMARY: Clinical case 1 includes an 83-year-old male diagnosed with periodontitis and classified as Stage III Generalized Grade B periodontitis, while clinical case 2, a 73-year-old male was classified as presenting Stage IV Generalized Grade B periodontitis. Although clinical and radiographic evaluations revealed similarities between the cases, the thought process that includes clinical judgment is described to guide a more accurate diagnosis following the guidelines of the new classification system. CONCLUSION: The two cases demonstrated here offer an opportunity for clinicians to recognize the essential role of sound clinical judgment in certain cases when applying the new periodontal disease classification system and also clarify questions emerging from implementing this classification system.

Future of preventing and managing common chronic inflammatory diseases.

Chronic inflammation has emerged as a key factor that contributes to some common chronic diseases and reduces lifespan. Studies have identified multiple types of chronic inflammation ranging from autoimmune disease, which attacks specific tissues, to autoinflammatory diseases, which cause low-grade systemic inflammation and contribute to several common chronic diseases. This article highlights new perspectives on the role of chronic inflammation in cardiovascular disease (CVD). Such information is being leveraged to develop new treatment strategies for CVD and may inform how periodontal disease influences CVD.

Guest Editorial: Clarifications on the use of the new classification of periodontitis.

This editorial provides clarifications on the application of the Stage and Grade classification of periodontitis. In particular it describes: (1) how to apply the extent criterion to the defined Stage of the disease; and (2) how to calculate tooth loss because of periodontitis in Stage III and IV cases presenting with evidently hopeless (irrational to treat) teeth with a clinical definition of such teeth.

Clinical application of the new classification of periodontal diseases: Ground rules, clarifications and "gray zones".

BACKGROUND: Successful dissemination of the new classification of periodontitis is facilitated by emphasis on the basic ground rules, clarification of ambiguities, and identification of "gray zones" where thoughtful application of the guidelines by an informed, experienced clinician is paramount to arrive at a correct Stage and Grade. METHODS: Highlighted ground rules are (1) Stage is a patient-based, not a tooth-based concept, therefore, a single Stage is assigned per patient; (2) Stage can shift upward over time, if the periodontal status deteriorates, but the initially assigned Stage is retained even after improvement post-therapy; (3) the complexity factors that determine Stage must be evaluated collectively, not in isolation, to arrive at a clinically meaningful assessment; (4) a single Grade is assigned to a patient based on a deliberate evaluation of the "biological fabric" of the case, in terms of history of/risk for further progression, interplay of risk factors, and the two-way effects of periodontitis or its treatment on general health; (v) shift of Grade over time is possible towards either direction, after thorough, collective, evaluation of changes in the above parameters. Exemplified gray zones include a radiographically intact patient with minimal attachment loss in older age; presence of "frank" periodontitis affecting a single tooth; and assessment of factors that do/do not lead to increased complexity of therapy. CONCLUSION: Differentiating between Stage I/II versus Stage III/IV periodontitis is relatively uncomplicated; further distinction between Stages and correct assignment of Grade requires nuanced, thorough interpretation of a broad array of findings by a knowledgeable clinician.

Using periodontal staging and grading system as a prognostic factor for future tooth loss: A long-term retrospective study.

BACKGROUND: A new classification of periodontal diseases aimed to identify periodontal disease based on a multidimensional staging and grading system has been recently proposed. However, up to date, its prognostic predictive capability has not been investigated. The aim of this study was to assess if parameters included in the new classification were predictive of tooth loss after a long-term follow-up (>10 years) in patients with periodontitis. METHODS: Patients presented with periodontitis at the University of Michigan between January 1966 and January 2004 were screened and categorized according to the new classification of periodontitis. Number/Reasons of teeth loss in patients who underwent at least one session/year of maintenance during the entire follow-up period were extracted and used to analyze the prognostic capabilities of variables (staging, grading, and Extent) included in the new classification. RESULTS: A total number of 292 patients with a mean follow-up of 289.7 ± 79.6 months were included. 31 (10.6%) patients were classified as Stage 1, 85 (29.1%) as Stage 2, 146 (50%) as Stage 3, and 30 (10.3%) as Stage 4. For grading, 34 (11.7%) were classified as Grade A, 193 (66.1%) as Grade B, and 65 (22.2%) as Grade C. Results of multilevel Cox regression analyses revealed a statistically significant association between stage (HR:3.73 between Stage 4 and Stage 1) and grade (HR: 4.83 between Grade C and Grade A) at baseline and periodontal related tooth loss, whereas no differences were detected for the extent of periodontitis. CONCLUSION: This study provides the initial evidence regarding the predictive ability of the new classification of periodontitis. Patients in either Stage 4 or Grade C showed a significantly higher periodontal-related tooth loss.

Biologically guided implant therapy: A diagnostic and therapeutic strategy of conservation and preservation based on periodontal staging and grading.

Biologically guided implant therapy is based on the new periodontitis classification system recently released by the American Academy of Periodontology and the European Federation of Periodontology that uses staging and grading for the diagnosis of periodontitis. This paper proposes that periodontitis staging and grading should be used in dental implant therapy as a means to ensure maximum conservation of teeth and maximum preservation of alveolar bone. These biologic principles should guide the treatment planning process and supersede a mechanically based, restoratively driven rationale that should be secondary to the biologic principles of conservation and preservation but part of the collaborative treatment planning process. And treatment alternatives throughout the patient's lifetime should be provided for in case of prosthesis loss due to peri-implantitis. The use of grading will help with recognition of systemic aspects that can have a negative impact.

Contemporary approaches for identifying individual risk for periodontitis.

Key breakthroughs in our understanding of the etiology and principles of predictable treatment of patients with chronic periodontitis first emerged in the late 1960s and carried on into the mid-1980s. Unfortunately, some generalizations of the evidence led many to believe that periodontitis was a predictable result of exposure to bacterial plaque accumulations over time. For a brief period, the initial plaque concept was translated by some to implicate specific bacterial infections, with both concepts (plaque exposure and specific infection) being false assumptions that led to clinical outcomes which were frustrating to both the clinician and the patient. The primary misconceptions were that every individual was equally susceptible to periodontitis, that disease severity was a simple function of magnitude of bacterial exposure over time, and that all patients would respond predictably if treated based on the key principles of bacterial reduction and regular maintenance care. We now know that although bacteria are an essential initiating factor, the clinical severity of periodontitis is a complex multifactorial host response to the microbial challenge. The complexity comes from the permutations of different factors that may interact to alter a single individual's host response to challenge, inflammation resolution and repair, and overall outcome to therapy. Fortunately, although there are many permutations that may influence host response and repair, the pathophysiology of chronic periodontitis is generally limited to mild periodontitis with isolated moderate disease in most individuals. However, approximately 20%-25% of individuals will develop generalized severe periodontitis and probably require more intensive bacterial reduction and different approaches to host modulation of the inflammatory outcomes. This latter group may also have serious systemic implications of their periodontitis. The time appears to be appropriate to use what we know and currently understand to change our approach to clinical care. Our goal would be to increase our likelihood of identifying those patients who have a more biologically disruptive response combined with a more impactful microbial dysbiosis. Current evidence, albeit limited, indicates that for those individuals we should prevent and treat more intensively. This paper discusses what we know and how we might use that information to start individualizing risk and treat some of our patients in a more targeted manner. In my opinion, we are further along than many realize, but we have a great lack of prospective clinical evidence that must be accumulated while we continue to unravel the contributions of specific mechanisms.

A new classification scheme for periodontal and peri-implant diseases and conditions - Introduction and key changes from the 1999 classification.

A classification scheme for periodontal and peri-implant diseases and conditions is necessary for clinicians to properly diagnose and treat patients as well as for scientists to investigate etiology, pathogenesis, natural history, and treatment of the diseases and conditions. This paper summarizes the proceedings of the World Workshop on the Classification of Periodontal and Peri-implant Diseases and Conditions. The workshop was co-sponsored by the American Academy of Periodontology (AAP) and the European Federation of Periodontology (EFP) and included expert participants from all over the world. Planning for the conference, which was held in Chicago on November 9 to 11, 2017, began in early 2015. An organizing committee from the AAP and EFP commissioned 19 review papers and four consensus reports covering relevant areas in periodontology and implant dentistry. The authors were charged with updating the 1999 classification of periodontal diseases and conditions and developing a similar scheme for peri-implant diseases and conditions. Reviewers and workgroups were also asked to establish pertinent case definitions and to provide diagnostic criteria to aid clinicians in the use of the new classification. All findings and recommendations of the workshop were agreed to by consensus. This introductory paper presents an overview for the new classification of periodontal and peri-implant diseases and conditions, along with a condensed scheme for each of four workgroup sections, but readers are directed to the pertinent consensus reports and review papers for a thorough discussion of the rationale, criteria, and interpretation of the proposed classification. Changes to the 1999 classification are highlighted and discussed. Although the intent of the workshop was to base classification on the strongest available scientific evidence, lower level evidence and expert opinion were inevitably used whenever sufficient research data were unavailable. The scope of this workshop was to align and update the classification scheme to the current understanding of periodontal and peri-implant diseases and conditions. This introductory overview presents the schematic tables for the new classification of periodontal and peri-implant diseases and conditions and briefly highlights changes made to the 1999 classification. It cannot present the wealth of information included in the reviews, case definition papers, and consensus reports that has guided the development of the new classification, and reference to the consensus and case definition papers is necessary to provide a thorough understanding of its use for either case management or scientific investigation. Therefore, it is strongly recommended that the reader use this overview as an introduction to these subjects. Accessing this publication online will allow the reader to use the links in this overview and the tables to view the source papers (Table ).

Periodontitis: Consensus report of workgroup 2 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

A new periodontitis classification scheme has been adopted, in which forms of the disease previously recognized as "chronic" or "aggressive" are now grouped under a single category ("periodontitis") and are further characterized based on a multi-dimensional staging and grading system. Staging is largely dependent upon the severity of disease at presentation as well as on the complexity of disease management, while grading provides supplemental information about biological features of the disease including a history-based analysis of the rate of periodontitis progression; assessment of the risk for further progression; analysis of possible poor outcomes of treatment; and assessment of the risk that the disease or its treatment may negatively affect the general health of the patient. Necrotizing periodontal diseases, whose characteristic clinical phenotype includes typical features (papilla necrosis, bleeding, and pain) and are associated with host immune response impairments, remain a distinct periodontitis category. Endodontic-periodontal lesions, defined by a pathological communication between the pulpal and periodontal tissues at a given tooth, occur in either an acute or a chronic form, and are classified according to signs and symptoms that have direct impact on their prognosis and treatment. Periodontal abscesses are defined as acute lesions characterized by localized accumulation of pus within the gingival wall of the periodontal pocket/sulcus, rapid tissue destruction and are associated with risk for systemic dissemination.

Staging and grading of periodontitis: Framework and proposal of a new classification and case definition.

BACKGROUND: Authors were assigned the task to develop case definitions for periodontitis in the context of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions. The aim of this manuscript is to review evidence and rationale for a revision of the current classification, to provide a framework for case definition that fully implicates state-of-the-art knowledge and can be adapted as new evidence emerges, and to suggest a case definition system that can be implemented in clinical practice, research and epidemiologic surveillance. METHODS: Evidence gathered in four commissioned reviews was analyzed and interpreted with special emphasis to changes with regards to the understanding available prior to the 1999 classification. Authors analyzed case definition systems employed for a variety of chronic diseases and identified key criteria for a classification/case definition of periodontitis. RESULTS: The manuscript discusses the merits of a periodontitis case definition system based on Staging and Grading and proposes a case definition framework. Stage I to IV of periodontitis is defined based on severity (primarily periodontal breakdown with reference to root length and periodontitis-associated tooth loss), complexity of management (pocket depth, infrabony defects, furcation involvement, tooth hypermobility, masticatory dysfunction) and additionally described as extent (localized or generalized). Grade of periodontitis is estimated with direct or indirect evidence of progression rate in three categories: slow, moderate and rapid progression (Grade A-C). Risk factor analysis is used as grade modifier. CONCLUSIONS: The paper describes a simple matrix based on stage and grade to appropriately define periodontitis in an individual patient. The proposed case definition extends beyond description based on severity to include characterization of biological features of the disease and represents a first step towards adoption of precision medicine concepts to the management of periodontitis. It also provides the necessary framework for introduction of biomarkers in diagnosis and prognosis.

A new classification scheme for periodontal and peri-implant diseases and conditions - Introduction and key changes from the 1999 classification.

A classification scheme for periodontal and peri-implant diseases and conditions is necessary for clinicians to properly diagnose and treat patients as well as for scientists to investigate etiology, pathogenesis, natural history, and treatment of the diseases and conditions. This paper summarizes the proceedings of the World Workshop on the Classification of Periodontal and Peri-implant Diseases and Conditions. The workshop was co-sponsored by the American Academy of Periodontology (AAP) and the European Federation of Periodontology (EFP) and included expert participants from all over the world. Planning for the conference, which was held in Chicago on November 9 to 11, 2017, began in early 2015. An organizing committee from the AAP and EFP commissioned 19 review papers and four consensus reports covering relevant areas in periodontology and implant dentistry. The authors were charged with updating the 1999 classification of periodontal diseases and conditions and developing a similar scheme for peri-implant diseases and conditions. Reviewers and workgroups were also asked to establish pertinent case definitions and to provide diagnostic criteria to aid clinicians in the use of the new classification. All findings and recommendations of the workshop were agreed to by consensus. This introductory paper presents an overview for the new classification of periodontal and peri-implant diseases and conditions, along with a condensed scheme for each of four workgroup sections, but readers are directed to the pertinent consensus reports and review papers for a thorough discussion of the rationale, criteria, and interpretation of the proposed classification. Changes to the 1999 classification are highlighted and discussed. Although the intent of the workshop was to base classification on the strongest available scientific evidence, lower level evidence and expert opinion were inevitably used whenever sufficient research data were unavailable. The scope of this workshop was to align and update the classification scheme to the current understanding of periodontal and peri-implant diseases and conditions. This introductory overview presents the schematic tables for the new classification of periodontal and peri-implant diseases and conditions and briefly highlights changes made to the 1999 classification. It cannot present the wealth of information included in the reviews, case definition papers, and consensus reports that has guided the development of the new classification, and reference to the consensus and case definition papers is necessary to provide a thorough understanding of its use for either case management or scientific investigation. Therefore, it is strongly recommended that the reader use this overview as an introduction to these subjects. Accessing this publication online will allow the reader to use the links in this overview and the tables to view the source papers (Table 1).

Periodontitis: Consensus report of workgroup 2 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

A new periodontitis classification scheme has been adopted, in which forms of the disease previously recognized as "chronic" or "aggressive" are now grouped under a single category ("periodontitis") and are further characterized based on a multi-dimensional staging and grading system. Staging is largely dependent upon the severity of disease at presentation as well as on the complexity of disease management, while grading provides supplemental information about biological features of the disease including a history-based analysis of the rate of periodontitis progression; assessment of the risk for further progression; analysis of possible poor outcomes of treatment; and assessment of the risk that the disease or its treatment may negatively affect the general health of the patient. Necrotizing periodontal diseases, whose characteristic clinical phenotype includes typical features (papilla necrosis, bleeding, and pain) and are associated with host immune response impairments, remain a distinct periodontitis category. Endodontic-periodontal lesions, defined by a pathological communication between the pulpal and periodontal tissues at a given tooth, occur in either an acute or a chronic form, and are classified according to signs and symptoms that have direct impact on their prognosis and treatment. Periodontal abscesses are defined as acute lesions characterized by localized accumulation of pus within the gingival wall of the periodontal pocket/sulcus, rapid tissue destruction and are associated with risk for systemic dissemination.