Periodontal Homeostasis: From Vienna to Texas—A Century of Periodontal Research in the Spirit of Bernhard Gottlieb

Bernhard Gottlieb arrived in Dallas, TX, in 1941, after fleeing the Nazis in Vienna and after unsuccessful attempts to settle in Palestine, New York, and then Michigan [1]. In Dallas, the once powerful head of Vienna's dental institute was fairly isolated, surrounded only by a few faithful admirers and without his famous students Balint Orban, Joseph-Peter Weinmann, and Harry Sicher, who by then had found a home in Chicago [2,3]. Alumni of Texas A&M College of Dentistry's predecessor, Baylor College of Dentistry, recognized Gottlieb's significance and bestowed him with a professorship in oral pathology. Gottlieb's new role in Dallas was to provide basic sciences education for dental students after the departure of the medical school faculty to Houston. However, Gottlieb's true legacy was his role in establishing oral biology as a new discipline at the interface between oral pathology and clinical sciences, most notably periodontics.

From 1920 to 1946, Gottlieb published seminal studies on aggressive periodontitis, periodontal regeneration, root cementum, and the barrier role of the periodontal ligament [4]. In 1942, Gottlieb was the first dental scientist to uncover the potential of biomimetics when he suggested that “… if these ideas about the biology of the cementum are correct, it is then our task to find out just how nature provides for continuous cementum deposition, and having done so, to imitate the procedure” [5]. Gottlieb also was keenly interested in bone homeostasis as he believed that the balance between alveolar bone resorption and apposition was important for the stability of the attachment apparatus [6]. Expanding on Gottlieb's original work, Texas A&M College of Dentistry in Dallas, TX, is hosting a conference on periodontal homeostasis from August 7 to 10, 2019, featuring a broad range of topics from periodontal mineral homeostasis, homeostasis of the periodontal immune response, periodontal tissue engineering, and minimally invasive therapy, as well as precision medicine.

The topic of this conference, periodontal homeostasis, is a textbook example for the role of stem cells and progenitors in tissue maintenance, repair, and regeneration: Periodontal stem cells control the nonmineralized state of the periodontal ligament as it is surrounded by the flanking mineralized tissues alveolar bone and cementum [7]. Osteoblast and osteoclast progenitors balance the anabolic and catabolic processes that model and shape the alveolar bone socket and affect tooth root anchorage as a result [8,9]. On an epigenetic level, periodontal homeostasis is regulated by histone methylation, DNA methylation, and microRNAs [10,11]. From a disease perspective, the periodontal host response is an inflammatory response to the disruption of microbial homeostasis in the periodontium [12,13]. Lastly, efforts to regenerate and/or to engineer periodontal tissues must maintain all aspects of periodontal homeostasis to ensure long-term function and tissue integration [14]. This special issue will present state-of-the-art research that investigates the role of stem cells in periodontal homeostasis, as it relates to genes, proteins, epigenetic mechanisms, and materials design. Our volume establishes a new benchmark in our understanding of the many fine-tuning mechanisms that maintain a healthy tooth attachment apparatus and the events that are involved in its dysregulation as a result of periodontal disease.