Paleogenomic insights into the red complex bacteria Tannerella forsythia in Pre-Hispanic and Colonial individuals from Mexico

The 'red complex' is an aggregate of three oral bacteria (Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola) responsible for severe clinical manifestation of periodontal disease. Here, we report the first direct evidence of ancient T.forsythia DNA in dentin and dental calculus samples from archaeological skeletal remains that span from the Pre-Hispanic to the Colonial period in Mexico. We recovered twelve partial ancient T. forsythia genomes and observed a distinct phylogenetic placement of samples, suggesting that the strains present in Pre-Hispanic individuals likely arrived with the first human migrations to the Americas and that new strains were introduced with the arrival of European and African populations in the sixteenth century. We also identified instances of the differential presence of genes between periods in the T. forsythia ancient genomes, with certain genes present in Pre-Hispanic individuals and absent in Colonial individuals, and vice versa. This study highlights the potential for studying ancient T. forsythia genomes to unveil past social interactions through analysis of disease transmission. Our results illustrate the long-standing relationship between this oral pathogen and its human host, while also unveiling key evidence to understand its evolutionary history in Pre-Hispanic and Colonial Mexico. This article is part of the theme issue 'Insights into health and disease from ancient biomolecules'.

Oral health status in historic population: Macroscopic and metagenomic evidence

Recent developments in High-Throughput DNA sequencing (HTS) technologies and ancient DNA (aDNA) research have opened access to the characterization of the microbial communities within past populations. Most studies have, however, relied on the analysis of dental calculus as one particular material type particularly prone to the molecular preservation of ancient microbial biofilms and potential of entire teeth for microbial characterization, both of healthy communities and pathogens in ancient individuals, remains overlooked. In this study, we used shotgun sequencing to characterize the bacterial composition from historical subjects showing macroscopic evidence of oral pathologies. We first carried out a macroscopic analysis aimed at identifying carious or periodontal diseases in subjects belonging to a French rural population of the 18th century AD. We next examined radiographically six subjects showing specific, characteristic dental pathologies and applied HTS shotgun sequencing to characterize the microbial communities present in and on the dental material. The presence of Streptococcus mutans and also Rothia dentocariosa, Actinomyces viscosus, Porphyromonas gingivalis, Tannerella forsythia, Pseudoramibacter alactolyticus, Olsenella uli and Parvimonas micra was confirmed through the presence of typical signatures of post-mortem DNA damage at an average depth-of-coverage ranging from 0.5 to 7X, with a minimum of 35% (from 35 to 93%) of the positions in the genome covered at least once. Each sampled tooth showed a specific bacterial signature associated with carious or periodontal pathologies. This work demonstrates that from a healthy independent tooth, without visible macroscopic pathology, we can identify a signature of specific pathogens and deduce the oral health status of an individual.

From alveolar diffuse atrophy to aggressive periodontitis: a brief history

Technologic advances in mechanics, electronics, physics, chemistry, and computer science have contributed to advances in dental medicine. Periodontology is not only a clinical science but is also directly related to the basic sciences. Research is conducted in laboratories rather than in clinics now. During the last century, aggressive periodontitis has received attention from numerous researchers because of its multifactorial features. This paper explores the long scientific journey of aggressive periodontitis, beginning with its first definition as alveolar diffuse atrophy. Perhaps in the future, "alveolar diffuse atrophy" will be referred to by another name or term. However, this journey will never end.

Coca chewing in prehistoric coastal Peru: dental evidence

In this study, we describe the dental health of four prehistoric human populations from the southern coast of Peru, an area in which independent archaeological evidence suggests that the practice of coca-leaf chewing was relatively common. A repeated pattern of cervical-root caries accompanying root exposure was found on the buccal surfaces of the posterior dentition, coinciding with the typical placement of coca quids during mastication. To further examine the association between caries patterning and coca chewing, caries site characteristics of molar teeth were utilized as indicators for estimating the likelihood of coca chewing for adults within each of the study samples. Likelihood estimates were then compared with results of a test for coca use derived from hair samples from the same individuals. The hair and dental studies exhibited an 85.7% agreement. Thus, we have demonstrated the validity of a hard-tissue technique for identifying the presence of habitual coca-leaf chewing in ancient human remains, which is useful in archaeological contexts where hair is not preserved. These data can be used to explore the distribution of coca chewing in prehistoric times. Simultaneously, we document the dental health associated with this traditional Andean cultural practice.

Understanding the pathogenesis of periodontitis: a century of discovery

The twentieth century was an especially notable time for research advances into the understanding of the aetiology and the pathogenesis of periodontitis. Beginning in 1900, using dark-field preparations, investigators began to implicate certain microorganisms, such as amoebae, as causing periodontitis. Today, using modern molecular techniques, we believe we have identified the primary causative agents of adult periodontitis. In 1900, histological sections of periodontal tissues at autopsy provided clues as to how periodontal pockets probably formed. Today there is a wealth of cellular and molecular data that suggest the actual pathways that the susceptible host uses to initiate periodontal tissue destruction. We now also appreciate that periodontitis may be a significant risk factor for systemic disease. A very exceptional 'century of discovery' into the nature of periodontal diseases should now lead to a new era of better diagnosis, prevention and treatment for this ubiquitous disease.

Milestones in periodontal research and the remaining critical issues

A significant recent development in periodontal research has been the convergence of basic and clinical research resulting in a logarithmic increase in the rate of progress. Scientific consensus has been reached in many areas. In most populations, moderate to severe periodontitis affects a relatively small segment of adults who are at high risk. The microbial etiology is accepted and the identity of the major pathogenic bacterial species is known. The mechanisms through which resistant individuals successfully fend off the microbial challenge are known, and the immuno-inflammatory pathways activated by bacteria that underlie destruction of the alveolar bone and the connective tissues of the periodontium are reasonably well understood. The evidence shows that these pathways are held in common by all forms of periodontitis. Therapeutic modulation of these pathways is now possible, and new treatments based on such modulation are now becoming available. Although bacteria are essential for disease to occur, they are insufficient; a susceptible host is also necessary. Host susceptibility, disease progression and response to treatment are determined predominantly by heredity and environmental and acquired risk factors. Some of these can be changed while others are immutable. Concepts and procedures for treatment are generally scientifically based and appropriately applied. Preventive measures are largely successful and widely practiced in industrialized countries. Clearly, control of these ancient chronic diseases is now within our reach. In spite of the tremendous progress, many unresolved issues remain. The purpose of this paper is to summarize some of the major accomplishments of periodontal research, and identify and discuss some of the more important critical issues that still need to be addressed.

Calculus deposits and bone loss on the teeth of Romano-British and eighteenth-century Londoners

The relation between dental calculus and periodontal disease is not clear but it is generally recognized that calculus is a significant pathogenetic factor. Skeletal material has previously been used to study some aspects of chronic adult periodontitis but few studies have quantified the extent of calculus in ancient populations and its relation to changes in alveolar bone height. This study records the presence and extent of calculus and its relation to alveolar bone loss in a Romano-British and eighteenth-century London population. There were significant differences in calculus deposition in the two populations but this appeared to have little effect on changes in alveolar bone contour. It is suggested that the amount of calculus may be related to diet but that changes in alveolar bone height seem to be independently controlled.

Factors affecting the lifespan of the human dentition in Britain prior to the seventeenth century

OBJECTIVE

To confirm that compensatory eruption (supereruption) of teeth past a stable periodontium occurs in response to severe occlusal attrition.

DESIGN

Regression analysis study from radiographs and direct measurements.

SETTING

Archaeological material at the University of Aberdeen.

SUBJECTS

47 individuals > 21 years old and dating from Late Mediaeval times (1300-1600 AD).

MAIN OUTCOME MEASURES

Occlusal attrition was recorded on the first permanent mandibular molars. Measurements on radiographs of the teeth from the fixed point of the inferior dental canal were taken to the occlusal surface, the alveolar crest and the tooth apex. Regression analysis was undertaken between these variables and related to attrition (age).

RESULTS

Continuous eruption of the permanent human dentition past a stable periodontium does occur in response to tooth height lost by wear, despite the fact that supereruption may lead to the eventual self destruction of the dentition. This mechanism was primarily responsible for the early loss (at 40-45 years of age) of dentitions in Mediaeval times.

CONCLUSIONS

Stability of occlusal height appears to be an important function of the dentition and if triggered by severe wear will lead to increasing root exposure and eventual exfoliation of the teeth. It is important not to confuse bone loss due to periodontitis with root exposure due to supereruption of the teeth.

Dental effects of diet and coca-leaf chewing on two prehistoric cultures of northern Chile

Two ancient cultures of northern Chile, the Chinchorro (9000-3500 BP) and the Maitas Chiribaya (850-700 BP) were examined for dental pathology in search of possible correlations between dental health, diet, and the cultural practice of coca-leaf chewing. The Chinchorro occupied the river mouth of the Azapa valley, subsisting almost exclusively on a maritime economy. The Maitas Chiribaya, descendants of migrant highlanders, had a rather well-developed agricultural subsistence base. The Chinchorro demonstrated extreme attrition rates and a correspondingly high frequency of periapical abscesses. They were essentially caries-free and enjoyed a moderate antemortem tooth loss frequency. The Maitas Chiribaya suffered light attrition; a high caries frequency, especially at the cementoenamel junction of crown and root, and a remarkably high antemortem tooth loss frequency. The cultural practice of coca-leaf chewing is implicated in the excessive posterior edentulism of the Maitas Chiribaya.

Periodontal defects of pulpal origin: evidence in early man

False assumptions have led to the widespread opinion that periodontitis of gingival origin is a ubiquitous disease and a common cause of tooth loss among ancient populations. Evaluation of dry skulls reveals that horizontal loss of crestal alveolar bone was unusual and of minor severity. Localized vertical bone defects of pulpal etiology were common and severe, often resulting in tooth mortality. The present paper identifies a number of factors that have contributed to the development of some important misconceptions about the nature of periodontal disease, its incidence, and its etiology.

Paleopathology in Australopithecus africanus: a suggested case of a 3-million-year-old prepubertal periodontitis

The fossil remains of a juvenile Australopithecus africanus specimen from Sterkfontein Member 4 temporally confined on faunal grounds to 2.5-3.0 million years before the present (Myr B.P.) show pathological alterations of the periodontal alveolar process consistent with a case of prepubertal periodontitis. This diagnosis is based on macroscopic features of alveolar bone loss distribution, pattern of periodontal bone destruction, migration of the affected deciduous molars, and on stereomicroscopic and scanning electron microscopic evidence of alveolar bone destruction. Differential diagnoses and pathological exclusions are discussed in terms of localized patterns of periodontal bone destruction and presumptive survival rate. The reported case appears to be the first detailed description of a recognized disease in early hominid evolution.