So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

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National Health and Nutrition Examination Survey

More than 700 bacterial species or phylotypes, of which over 50% have not been cultivated, have been detected in the oral cavity. Our purposes were (i) to utilize culture-independent molecular techniques to extend our knowledge on the breadth of bacterial diversity in the healthy human oral cavity, including not-yet-cultivated bacteria species, and (ii) to determine the site and subject specificity of bacterial colonization. Nine sites from five clinically healthy subjects were analyzed. Sites included tongue dorsum, lateral sides of tongue, buccal epithelium, hard palate, soft palate, supragingival plaque of tooth surfaces, subgingival plaque, maxillary anterior vestibule, and tonsils. 16S rRNA genes from sample DNA were amplified, cloned, and transformed into Escherichia coli. Sequences of 16S rRNA genes were used to determine species identity or closest relatives. In 2,589 clones, 141 predominant species were detected, of which over 60% have not been cultivated. Thirteen new phylotypes were identified. Species common to all sites belonged to the genera Gemella, Granulicatella, Streptococcus, and Veillonella. While some species were subject specific and detected in most sites, other species were site specific. Most sites possessed 20 to 30 different predominant species, and the number of predominant species from all nine sites per individual ranged from 34 to 72. Species typically associated with periodontitis and caries were not detected. There is a distinctive predominant bacterial flora of the healthy oral cavity that is highly diverse and site and subject specific. It is important to fully define the human microflora of the healthy oral cavity before we can understand the role of bacteria in oral disease.

Defining the Normal Bacterial Flora of the Oral Cavity

This review covers the toxicology of mercury and its compounds. Special attention is paid to those forms of mercury of current public health concern. Human exposure to the vapor of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate. Ethylmercury in the form of a preservative, thimerosal, added to certain vaccines, is the most recent form of mercury that has become a public health concern. The review leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an "element of mystery."

The Toxicology of Mercury and Its Chemical Compounds

Biology, immunology, and cariogenicity of Streptococcus mutans

Background: Accurate information on the prevalence and extent of periodontal diseases in the United States adult population is lacking. This study estimated the prevalence and extent of periodontal disease in the United States using data from the third National Health and Nutrition Examination Survey (NHANES III). Methods: A nationally representative sample was obtained during 1988 to 1994 by a stratified, multi-stage probability sampling design. A subsample of 9,689 dentate persons 30 to 90 years old who received a periodontal examination was used in this study, representing approximately 105.8 million civilian, non-institutionalized Americans in 1988 to 1994. Periodontal attachment loss, probing depth, and furcation involvement were assessed in 2 randomly selected quadrants per person. Attachment loss and probing depth were assessed at 2 sites per tooth, the mesiobuccal and mid-buccal surfaces. The periodontal status of each subject was assessed by criteria based on the extent and severity of probing de...

Destructive periodontal disease in adults 30 years of age and older in the United States, 1988-1994.

PROBLEM/CONDITION: Dental caries is a common chronic disease that causes pain and disability across all age groups. If left untreated, dental caries can lead to pain and infection, tooth loss, and edentulism (total tooth loss). Dental sealants are effective in preventing dental caries in the occlusal (chewing) and other pitted and fissured surfaces of the teeth. Enamel fluorosis is a hypomineralization of enamel related to fluoride exposure during tooth formation (first 6 years for most permanent teeth). Exposure to fluoride throughout life is effective in preventing dental caries. This is the first CDC Surveillance Summary that addresses these conditions and practices. REPORTING PERIOD: 1988-1994 and 1999-2002. SYSTEM DESCRIPTION: The National Health and Nutrition Examination Survey (NHANES) is an ongoing survey of representative samples of the civilian, noninstitutionalized U.S. population aged >/=2 months in NHANES 1988-1994 and all ages during 1999-2002. The dental component gathered information on persons aged >/=2 years. RESULTS: During 1999-2002, among children aged 2-11 years, 41% had dental caries in their primary teeth. Forty-two percent of children and adolescents aged 6-19 years and approximately 90% of adults had dental caries in their permanent teeth. Among children aged 6-19 years, 32% had received dental sealants. Adults aged >/=20 years retained a mean of 24 of 28 natural teeth and 8% were edentulous. Among persons aged 6-39 years, 23% had very mild or greater enamel fluorosis. Disparities were noticed across all age groups, among racial/ethnic groups, persons with lower education and income, and by smoking status. From 1988-1994 to 1999-2002, four trends were observed: 1) no change in the prevalence of dental caries in primary teeth among children aged 2-11 years, 2) a reduction in prevalence of caries in permanent teeth of up to 10 percentage points among persons aged 6-19 years and up to six percentage points among dentate adults aged >/=20 years, 3) an increase of 13 percentage points in dental sealants among persons aged 6-19 years, and 4) a six percentage point reduction in total tooth loss (edentulism) among persons aged >/=60 years. INTERPRETATION: The findings of this report indicate that the dental caries status of permanent teeth has improved since the 1988-1994 survey. Despite the decrease in caries prevalence and severity in the permanent dentition and the increase in the proportion of children and adolescents who benefit from dental sealants, disparities remain. PUBLIC HEALTH ACTION: These data provide information for public health professionals in designing interventions to improve oral health and to reduce disparities in oral health, for researchers in assessing factors associated with disparities and dental caries in primary teeth, and in designing timely surveillance tools to monitor total fluoride exposure.

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Surveillance for dental caries, dental sealants, tooth retention, edentulism, and enamel fluorosis--United States, 1988-1994 and 1999-2002.

Background: The aim of this study was to assess the prevalence and extent of gingival recession, gingival bleeding, and dental calculus in United States adults, using data collected in the third National Health and Nutrition Examination Survey (NHANES III). Methods: The study group consisted of 9,689 persons 30 to 90 years of age obtained by a stratified, multi-stage probability sampling method in 1988 to 1994. The weighted sample is representative of U.S. adults 30 years or older and represents approximately 105.8 million civilian, non-institutionalized Americans. Gingival recession, gingival bleeding, and dental calculus were assessed at the mesio-buccal and mid-buccal surfaces in 2 randomly selected quadrants, one maxillary and one mandibular. Data analysis accounted for the complex sampling design used. Results: We estimate that 23.8 million persons have one or more tooth surfaces with ≥3 mm gingival recession; 53.2 million have gingival bleeding; 97.1 million have calculus; and 58.3 million have subg...

Gingival Recession, Gingival Bleeding, and Dental Calculus in Adults 30 Years of Age and Older in the United States, 1988-1994

This paper reports estimates of the periodontal status of US population derived from data from Phase 1 of the Third National Health and Nutrition Examination Survey conducted by the National Institute of Dental Research from 1988-1991. A total of 7,447 dentate individuals 13 years of age and older, representing approximately 160.3 million civilian non-institutionalized Americans, received a periodontal assessment. Measurements of gingival bleeding, gingival recession level, periodontal pocket depth, and calculus were made by dental examiners. Assessments were made at the mesiobuccal and mid-buccal sites of all fully erupted permanent teeth present in two randomly selected quadrants, one maxillary and one mandibular. All data were weighted and standard errors calculated by special software to adjust for the effect of sample design. Although over 90% of persons 13 years of age or older had experienced some clinical loss of attachment (LA), only 15% exhibited more severe destruction (LA > or = 5 mm). Prevalence of moderate and severe LA and gingival recession increased with age, while prevalence of pockets > or = 4 mm or > or = 6 mm did not. These data suggest that the increasing prevalence of LA with age is more associated with increasing prevalence of recession than with changes in the prevalence of pockets or age. The extent or number of affected sites with advanced conditions for loss of attachment, pocket depth, or recession was not large for any age group. Differences in prevalence of moderate and severe loss of attachment, moderate and deep pockets, and recession were found among gender and race-ethnicity groups. Females exhibited better periodontal health than males, and non-Hispanic whites exhibited better periodontal health than either non-Hispanic blacks or Mexican-Americans.

Albert Kingman

Papers

Destructive periodontal disease in adults 30 years of age and older in the United States, 1988-1994.

Surveillance for dental caries, dental sealants, tooth retention, edentulism, and enamel fluorosis--United States, 1988-1994 and 1999-2002.

Gingival Recession, Gingival Bleeding, and Dental Calculus in Adults 30 Years of Age and Older in the United States, 1988-1994

Periodontal status in the United States, 1988-1991: prevalence, extent, and demographic variation.

Methodological aspects of epidemiological studies of periodontal diseases.