There is growing interest in, and appreciation of, the importance of epidemiological science in furthering our understanding of periodontal diseases. There is also interest in applying modern epidemiological methods to identify periodontal disease risk factors, prognostic factors and the long-term outcomes of care, as well as periodontal-systemic associations. This volume combines critical reviews of selected areas of contemporary interest with targeted methodologically focused articles, in order to provide a valuable reference text to guide readers in their own critical assessment of new scientific findings, as well as to assist investigators in the design and analysis of their own original research in periodontal epidemiology. The 11 review articles that comprise this volume were selected with this goal in mind. They aim to inform readers on the methodological rigor that needs to be applied, both in the design of epidemiological studies and interpretation of their results, and the limitations to the inferences that may be drawn from epidemiological studies. Despite its various limitations, the field of periodontal epidemiology is expected to continue to grow in importance and relevance. There remains a need for well-designed, carefully analyzed and correctly interpreted observational studies, including longitudinal cohort studies and case-control studies, in order to adequately understand both the causes of periodontal disease and the associations between periodontal disease and systemic disease in populations.
Our understanding of the global epidemiology of periodontal disease has changed considerably over the past 50 years. This change has been influenced not only by our evolving knowledge of the natural history and distribution of the disease, but also by changing measurement methodologies. Although great strides have been made in describing the underlying contributions of microorganisms and plaque ecology, as well as the inflammatory and host responses, there is still much that is not known regarding risk susceptibility and prevention effectiveness. The focus of global periodontal epidemiology during the last half century has been on identifying populations who have periodontal disease and situations where disparities in disease prevalence exist between groups. Unlike dental public health activities directed toward dental caries, less effort has been made in periodontal epidemiology with regard to surveying or monitoring groups who may be at greater risk for moderate or severe disease and evaluating public health initiatives directed at mitigating risk or reducing such periodontal disease prevalence. Additionally, there is limited information regarding current national estimates of periodontal disease in most countries. Although numerous periodontal studies have been performed globally, very few are epidemiological studies using nationally representative samples. The aim of this critical review is to discuss the historical context of global periodontal disease epidemiology, highlight key activities and findings over the past decade in global periodontal epidemiology, and comment on how changes in the practice of epidemiology may affect global periodontology over the coming decade.
Causal theory and the etiology of periodontal diseases.
Periodontol 2000. 2012 Feb;58(1):26-36
Authors: Heaton B, Dietrich T
Abstract
Causal theory and causal models have proven to be helpful in understanding the multi-factorial causation of many diseases, including periodontitis. The design and application of causal models is essential to the appropriate design, conduct and analysis of studies on periodontal disease causation. This review discusses the principles of causation and causal theory, both in general and as they pertain to studies of the etiology of periodontitis. Specifically, we present an overview of models of causation, including the potential outcomes model, the sufficient component cause model, and directed acyclic graphical models. More thorough explanations and accompanying illustrations are provided for the sufficient component cause model and the directed acyclic graphical model. Topics related to the study of periodontitis, as illustrated by such models, include the principles of confounding and effect measure modification (interaction). Existing models of periodontitis etiology are critically reviewed in this context.
In this systematic review, we explore and summarize the peer-reviewed literature on putative genetic risk factors for susceptibility to aggressive and chronic periodontitis. A comprehensive literature search on the PubMed database was performed using the keywords ‘periodontitis’ or ‘periodontal disease’ in combination with the words ‘genes’, ‘mutation’, ‘SNP’ or ‘polymorphism’. The studies selected were written in English, had a case-control design, and reported genotype distribution. Only studies with at least 100 individuals in either the case or control group were included. Research on genetic polymorphisms has only had limited success in identifying significant and reproducible genetic factors for susceptibility to aggressive periodontitis and chronic periodontitis. Taking together the data published on gene polymorphisms in aggressive and chronic periodontitis, we conclude that there are differences among the various studies for the rare allele carriage rates. Nevertheless, there is some evidence that polymorphisms in the IL1B, IL1RN, FcγRIIIb, VDR and TLR4 genes may be associated with aggressive periodontitis susceptibility, and polymorphisms in the IL1B, IL1RN, IL6, IL10, VDR, CD14, TLR4 and MMP1 genes may be associated with chronic periodontitis susceptibility as a single genetic factor in certain populations. Future studies should apply stricter disease classifications, use larger study cohorts, adjust for relevant risk factors in aggressive and chronic periodontiti,s and include analysis of multiple genes and polymorphisms. Establishing consortia and performing collaborative studies may help to conquer the limitations of small sample size and limited statistical power.
Socioeconomic position indicators and periodontitis: examining the evidence.
Periodontol 2000. 2012 Feb;58(1):69-83
Authors: Borrell LN, Crawford ND
Abstract
Socioeconomic factors, such as education and income, are associated with disparities in the prevalence and severity of periodontal disease, and this has been recognized since the 1960s. Epidemiological reports have consistently shown that periodontal disease is inversely related to education and income after controlling for age and gender, and that differences in education and income explain most if not all of the observed disparities in periodontal disease between blacks and whites. Although race/ethnicity has been the main focus of studies on differences in periodontal diseases in the USA, periodontal disease disparities according to socioeconomic position (SEP) indicators (i.e. education, income, poverty-income ratio) remain pervasive in the USA. SEP indicators, as used in the epidemiological literature, involve use of socioeconomic measures as a proxy measure for an individual’s place, position and power in society. Thus, understanding disparities according to SEP indicators in periodontal health status may provide insight into why racial/ethnic disparities in periodontal health status persist. Here we review recent prevalence estimates of periodontitis according to SEP indicators, and critically assess the importance of SEP factors in periodontal epidemiolgy. The majority of the data available for review come from the USA. However, data from other countries are included where available. Specifically, we identify the advantages and disadvantages of the most commonly used SEP indicators in studying periodontal disease, summarize existing evidence on the association between SEP indicators and periodontitis, discuss the analytical issues associated with SEP indicators, and suggest future and alternative research directions for examining the association between SEP indicators and periodontitis.
Active and passive smoking: assessment issues in periodontal research.
Periodontol 2000. 2012 Feb;58(1):84-92
Authors: Walter C, Kaye EK, Dietrich T
Abstract
Tobacco use, particularly active cigarette smoking, is a strong modifiable risk factor for periodontitis. Our primary aim is to provide a systematic review of the impact of environmental tobacco smoke on periodontal diseases. Nine publications were identified by electronic literature search up to September 2010. Epidemiological data for a US population sample and a cohort of Japanese men suggest that environmental tobacco smoke exposure may be associated with increase periodontitis prevalence and increased risk of periodontitis progression. Secondly, several methodological issues related to cigarette smoking in clinical and epidemiological research studies are discussed. Tobacco use history is a multi-dimensional phenomenon, with characteristics such as intensity, duration and time since cessation. Understanding these complexities of smoking history and accurate measurement of the exposure, using biomarkers and/or self-reported data as appropriate, are of central importance in clinical and epidemiological studies on the effects of active and passive smoking. The most appropriate approach to assess smoking exposure will vary according to the purpose and design of a particular study.
Nutrition, dietary guidelines and optimal periodontal health.
Periodontol 2000. 2012 Feb;58(1):93-111
Authors: Kaye EK
Abstract
Dietary nutrients may serve as antioxidants, co-enzymes in energy production and metabolic processes, and components of tissue structures that keep the body’s systems functioning properly and maintain good overall health, including oral health. Nutrients that are thought to be especially important for maintaining the periodontium have been the focus of epidemiological studies for many years. However, such research has not consistently found significant associations between periodontal disease incidence or prevalence and the intake levels of these and other nutrients. To date, there is insufficient evidence that current dietary intake recommendations and guidelines need to be changed in order to promote optimal periodontal health. It is important to consider the range of nutrient intakes or biomarkers in any given study population and how they relate to recommended levels when evaluating the evidence. This information is often lacking in studies of nutritional associations in periodontal research. A number of methodological issues may arise in terms of study design, data collection and analysis of dietary data, and these may affect the interpretation of epidemiological study results and the ability to draw inferences and reach conclusions about appropriate dietary recommendations. These issues are critically reviewed.
The validity of epidemiological and clinical observations is paramount, not only for scientific advancement but also in evidence-based practice. Concern regarding validity with respect to the design and conduct of analytic epidemiological studies is often under-appreciated, partly as a consequence of our focus on randomized experimental designs as the highest standard of ‘proof’ in clinical science. We review the design, conduct and interpretation of rigorous analytic epidemiological study designs, with specific reference to periodontology. We give special emphasis to intrinsic validity and the use of focused aims to re-frame the perspective on the strength of evidence in reviews of the literature. Specifically, we draw on the periodontal research literature to provide an overview of the appropriate design and conduct of cohort studies, including randomized designs, case-control and cross-sectional studies. The concepts of selection bias, information bias and confounding are explored for each study design, both in general terms and with respect to a critical review of the literature on the epidemiology of periodontal diseases.
Regression models in periodontal epidemiology: purpose, approach and interpretation.
Periodontol 2000. 2012 Feb;58(1):121-33
Authors: Jimenez M, Dietrich T
Abstract
Statistical models, including those using regression analyses, are ubiquitous in periodontal research. However, many investigators may not have a thorough understanding of the concepts underlying the complex statistical models used in much of the current literature. This review aims to demystify biostatical regression models and familiarize the reader with the regression models most commonly encountered in the periodontal literature. Complex models can be intuitively understood in terms of stratified analyses. Therefore, we discuss the use of stratified analyses and emphasize their natural connection to regression models using examples from the periodontal research literature. We critically review various types of regression models, as well as the fundamental assumptions unique to each. An introduction to the fundamentals of model building describes the basics of variable selection procedures and variable management, including discussions regarding the assumptions inherent in common practices. Lastly, modeling approaches to assess confounding and effect modification are discussed by use of examples from the periodontal epidemiological literature.
Development of prognostic indicators using classification and regression trees for survival.
Periodontol 2000. 2012 Feb;58(1):134-42
Authors: Nunn ME, Fan J, Su X, Levine RA, Lee HJ, McGuire MK
Abstract
Development of an accurate prognosis is an integral component of treatment planning in the practice of periodontics. Prior work has evaluated the validity of using various clinical measured parameters for assigning periodontal prognosis as well as for predicting tooth survival and change in clinical conditions over time. We critically review the use of multivariate classification and regression trees (CART) for survival in developing evidence-based periodontal prognostic indicators. We focus attention on two distinct methods for multivariate CART for survival: the marginal goodness-of-fit approach and the multivariate exponential approach. A number of common clinical measures have been found to be significantly associated with tooth loss from periodontal disease, including furcation involvement, probing depth, mobility, crown/root ratio and oral hygiene. However, the inter-relationships among these measures, as well as the relevance of other clinical measures to tooth loss from periodontal disease (such as bruxism, family history of periodontal disease and overall bone loss), remain less clear. Although the inferences that can be drawn from any single study are necessarily limited, application of new approaches in epidemiological analyses to periodontal prognosis, such as CART for survival, should yield important insights into our understanding and treatment of periodontal diseases.
PMID: 22133372 [PubMed - in process]
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