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This publication can be found online at http://jods.mitpress.mit.edu/pub/the-future-of-periodontology.
The Future of Periodontology
P. Mark Bartold, BDS, BScDent (Hons), PhD, DDSc, FRACDS (Perio); Australia

Part 1 – Genetics, Epigenetics, and Risk Assessment

Risk assessment has been one of the most important components of periodontal diagnosis and treatment planning. Much progress has been made, and this topic will remain a very important aspect of periodontal research and ultimately practice in the years to come. Recognition that periodontitis is a multifactorial disease involving a complex interplay between host, environment, and microbes is central to our current understanding.
While it is very clearthat periodontitis cannot, and will not, develop in the absence of bacteria, it is becoming increasingly obvious that there are some patients who, despite the presence of considerable plaque deposits, do not develop periodontitis. It is also evident that there are individuals who have very minor visible deposits of plaque but still develop advanced, destructive periodontitis. These observations have led to a major paradigm shift in periodontology in which it is acknowledged that plaque is not sufficient for periodontitis to develop.
Indeed it became evident that in addition to dental plaque, other risk factors such as environmental and genetic factors, host response, and connective and bone tissue metabolism are critical determinants of the clinical manifestation of periodontitis (see figure). knowledge has spurred interest in the development of new, more informed management approaches for our patients. In addition to improved oral hygiene,this understanding dictates that patients must be evaluated for other risk factors which would contribute to the development of periodontitis, and these must be controlled in order for treatment to be successful. Indeed, it is now recognized that dental plaque (and its constitutive elements) accounts for less than half of the risk for developing periodontitis. Thus, the majority of the risk must be considered when diagnosing and treating the periodontal diseases.
In the future, the identification of individual risk, which can be thought of as personalized medicine/personalized dentistry, will become an integral part of periodontal practice. Advances are expected to be in the fields of genomics (and other “omic” technologies) and epigenetics. With the completion of the human genome project, new opportunities arise for investigating and utilizing. This genomewide screening of populationsto determine the genetic contributions to periodontitisin its various forms. in the field of genetics, of cellular and physiological phenotypic trait variations that are caused, not by changes in the DNA sequence, but rather by external or environmental factors thats witch genes on and off and affect how cells respond. to impact our understanding of periodontitis and how environment and genes interact to result in disease. Clearly this has great potential.

Part 2 – Host Pathogen Relationships

In line with the above recognition of the role of the host response in the development of periodontitis, new technologies will emerge incorporating the concepts of host modulation therapies and adjuncts. Not only will these therapies be aimed at controlling the host inflammatory response, but the potential to also modify the microbial infection through such approaches is an attractive thesis. WhenMarsh, et.al.proposed the “ecological plaque hypothesis,” it was largely ignored because it was discordant with the thinking about periodontal microbiology at the time, in that it was considered that specific bacteria
were solely responsible for development of periodontitis. His concept that it was indeed the host modification of the periodontal lesion, which under inflammatory conditions selected for so-called pathogenic species, was an important shift in our thinking. This concept has significant ramifications for host modulation therapy based on controlling inflammation, rather than focusing solely on elimination of infection as a treatment modality.
Notwithstanding the above, the microbiota cannot be totally discounted. Evolving concepts incorporating the human microbiome and our understanding of how microbial communities interact will form the basis of our new understanding of the periodontal microbiota and its role in the development and progression of periodontitis. Recently oral microbiologists have embraced the concept of bacterial dysbiosis as being a key driving force in the development of periodontitis. In this model, microbial imbalance leads to the emergence of pathogenic processes associated with periodontitis. While this concept is a reworking of the role of the host in modulating microbial periodontal infection described above, it is an attractive hypothesis in keeping with current understanding of other disturbances and illnesses of the gastrointestinal tract.

Part 3 – Periodontal Regeneration

Regeneration of damaged periodontal tissues as a result of periodontitis has been considered the ultimate goal of periodontal treatment. Over the past four decades many procedures have been proposed, mostly associated with root surface conditioning and implantation of bone substitutes into periodontal defects, as a means of obtaining periodontal regeneration. Unfortunately, due to a poor understanding of the requirements for periodontal regeneration, namely the importance of encouraging the growth of cementum, periodontal ligament, and bone, these early concepts were naïve. It is now recognized that regenerative treatment of periodontal defects with a biological agent or a surgical procedure requires that each functional stage of regeneration be grounded in biology. With such concepts in mind, the seminal studies of Karring, Nyman, and coworkers from Gothenburg led to the development of guided tissue regeneration (GTR) as a treatment modality. Although this was a significant advance, it became evident that while periodontal regeneration was biologically possible, it was clinically very difficult to achieve on a reliable basis due to a range of patient and technical variables. More recently, we have seen the development of biological agents and preparations which, when applied onto root surfaces, can result in significant regeneration of damaged periodontal tissues. The use of such agents offers a simpler approach to periodontal regeneration, with equivalent, and sometimes superior, results compared to GTR procedures. However, as has been noted for GTR, the clinical outcomes using biological agents can be variable and further work is needed to improve their clinical utility. Most recently, the use of mesenchymal stem cells has been explored for the purposes of achieving periodontal regeneration.
Periodontal ligament stem cells were first isolated and characterized in 2004, and since then the study of dental stem cells has expanded regarding their potential use for periodontal regeneration. Along similar lines to stem cell therapy, gene therapy for periodontal regeneration has been proposed, although this technology carries much greater technical and ethical issues. In order for these therapies to be successful, suitable delivery devices need to be developed in the context of tissue engineering. Tissue engineering is defined as the science of reconstructing or mimicking natural processes through the use of synthetic polymer scaffolds, with the expectation of tissue regeneration. The development of biocompatible scaffolds will be crucial in the next phases of this technology, and possible approaches include biodegradable materials, smart materials, and 3D printing.
While the future looks promising, there is a considerable amount of work to be done before periodontal regeneration is a reliable and predictable clinical approach.
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