https://doi.org/10.1177/0022034519830686 Journal of Dental Research 2019, Vol. 98(4) 373–385 © International & American Associations for Dental Research 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0022034519830686 journals.sagepub.com/home/jdr JDR Centennial Series Introduction Science and technology frequently appear to recycle concepts, inventions, and discoveries, as described by Steven Poole (2016) in Rethink: The Surprising History of New Ideas: old is the new new. For example, the 1960s description of the amphibiontic relationship between the indigenous oral flora and the human host (Rosebury 1962) has resurfaced under the concept of keystone pathogens, pathobionts, and dysbiosis as triggers of oral diseases (Marsh 1994; Hajishengallis et al. 2012). Advances in biotechnology have facilitated revisiting topics in oral microbiology to unravel key features and mecha- nisms that were not previously appreciated. The diversity of the oral microbiota and the ability of oral microorganisms to form dental plaque on tooth, implants, and oral mucosal surfaces in a sophisticated manner have been characterized (Moore and Moore 1994; Paster et al. 2001; Zaura et al. 2009; Dewhirst et al. 2010; Charalampakis and Belibasakis 2015). Complex interactions among microorgan- isms, the host, and the oral environment were demonstrated, which can translate into the clinical symptoms of white spot lesions or inflamed gingiva/peri-implant mucosa (Marsh 2005; Charalampakis and Belibasakis 2015). The oral microbiome is understood to have a dynamic “biofilm lifestyle” (Marsh 2005). In celebration of the Journal of Dental Research cen- tennial, this review highlights findings that, over a century of technological progress, contributed to the evolutionary improvement of our knowledge of dental biofilms and their roles in oral health and diseases. Oral Microbiology 100 y Ago The 19th century was an active period in medical sciences, and major discoveries included cultivation of microorganisms and identification of etiologic agents of infectious diseases. Koch’s postulates described criteria whereby microorganisms could be related to diseases. During this era, reputed dentists, including Riggs, Harlan, and Miller reinforced the microbial etiology of caries and periodontal diseases and promoted the concept of proper oral hygiene for managing disease. Periodontal disease (pyorrhea alveolaris) was renamed “Riggs’s disease.” Riggs introduced the mechanical debridement of teeth with irrigation of periodontal pockets with antiseptics. Harlan recognized that subgingival microorganisms were mainly anaerobic and pro- posed injection of hydrogen peroxide into periodontal pockets to provide “nascent oxygen to destroy the unclassified micro- organisms there present.” The first oral microbiologist, 830686JDR XX X 10.1177/0022034519830686Journal of Dental ResearchColombo and Tanner research-article 2019 1 Institute of Microbiology, Department of Medical Microbiology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 2 Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA 3 Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA Corresponding Author: A.P.V. Colombo, UFRJ/CCS–Instituto de Microbiologia Paulo de Góes– Bloco I, Lab. I2-03, Av. Carlos Chagas Filho, 373 Cidade Universitária– Rio de Janeiro, RJ, CEP: 21941-902, Brasil. Email: apcolombo@micro.ufrj.br The Role of Bacterial Biofilms in Dental Caries and Periodontal and Peri-implant Diseases: A Historical Perspective A.P.V. Colombo 1 and A.C.R. Tanner 2,3 Abstract Over the last hundred years, groundbreaking research in oral microbiology has provided a broad and deep understanding about the oral microbiome, its interactions with our body, and how the community can affect our health, be protective, or lead to the development of dental diseases. During this exciting journey, hypotheses were proposed, and concepts were established, discarded, and later revisited from updated perspectives. Dental plaque, previously considered a polymicrobial community of unspecific pathogenicity, is recognized as microbial biofilms with healthy, cariogenic, or periodontopathogenic profiles, resulting from specific ecologic determinants and host factors. The “one pathogen, one disease” paradigm of oral infections has been replaced by a holistic concept of a microbial community as the entity of pathogenicity. Cutting-edge technology can now explore large microbial communities related to different clinical conditions, which has led to finding several novel disease-associated species and potential pathobionts and pathobiomes. This vast amount of data generated over time has widened our view of the etiology of caries and periodontal and peri-implant diseases and has promoted updated strategies to treat and prevent the oral diseases. Keywords: microbiota, peri-implantitis, periodontitis, plaque biofilms, gingivitis, tooth decay