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The new model of periodontal disease

Nov. 5, 2015
Polymicrobial Synergy and Dysbiosis (PSD) is the word salad that the new model of periodontal disease is called as revealed by research. Dr. Richard Nagelberg breaks down each component so that we can consume this salad in understandable bites. He explains how bacteria, such as Porphyromonas gingivalis, fit into the model of periodontal disease development and progression.
Polymicrobial Synergy and Dysbiosis (PSD) is the word salad that the new model of periodontal disease is called as revealed by research. Let’s consume this salad.

Polymicrobial is self-explanatory; i.e., a community of different microbes. Synergy is a term used in many different settings. In business, it can be defined as the increased effectiveness that results when two or more people or businesses work together. The definition in the context of PSD is actually very similar. Synergy in this case refers to the coordinated action of oral bacteria promoting inflammation and bacterial survival. The term further explains that the coordinated action of the community of microbes is exponentially greater than it would be if the individual microbial species were working separately, and not in a good way. It’s all about the increased virulence of the synergistic oral bacteria, and how damage is ramped up when they work together.

Dysbiosis is an imbalance in the abundance or influence of a microbial community. A dysbiotic state promotes inflammation and periodontal disease. A homeostatic (nondysbiotic) balance of bacteria promotes healthy gums.

In this current model of periodontal disease, bacteria such as Porphyromonas gingivalis are called periopathogens. In the new model of periodontal disease development and progression, P. gingivalis is called a keystone pathogen. This is not just a matter of verbiage, as you will see.

It should be borne in mind that the current model of periodontal disease also involves a polymicrobial dysbiotic bacterial community. The current model indicates that a predominance of perio pathogens is required for disease development, which is a dysbiotic state. There are, however, fundamental and critically important differences in the current and new, emerging understanding of periodontal disease. The differences are critically important in a variety of ways. The next blog post will further explain what’s going on with these clever, microbial rascals.


Richard H. Nagelberg, DDS, has practiced general dentistry in suburban Philadelphia for more than 30 years. He is a speaker, advisory board member, consultant, and key opinion leader for several dental companies and organizations. He lectures on a variety of topics centered on understanding the impact dental professionals have beyond the oral cavity. Contact Dr. Nagelberg at [email protected].