1. Hx, Theory + Definitions Flashcards
What is a fact?
an objective and verifiable observation, in contrast with a hypothesis or theory, which is intended to explain or interpret facts.
What is a hypothesis?
an idea that hasn’t been proven yet. If enough evidence accumulates to support a hypothesis, it moves to the next step — known as a theory
What is a theory?
a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.” Theories are formed from hypotheses that have been subjected repeatedly to tests of evidence which attempt to disprove or falsify them
What are the theories of caries?
Exogenous theories
• Worm Theory
• Chemical (acid) Theory
• Parasitic (septic) Theory
Endogenous Theories
• Humoral Theory
• Vital Theory
Other Theories
• The Acidogenic Theory
• The Proteolytic Theory
• Proteolysis Chelation Theory
• Sucrose Chelation Theory
Current concept of caries aetiology = Demineralisation and remineralisation
What is Worm theory?
- In 1674, Velschius described the winding of a worm on a small stick to gently remove it from the person’s body
- In 1870, Fedechenko published the first scientific report of a 12-cm Guinea worm nematode, which he removed from a person’s body, naming it Drancunculus medinensis
- The Caduceus serpent staff of Asclepius was adopted by the American Medical Association as their symbol in 1912, and could in fact represent the removal of a guinea worm with a stick by the ancients
- Ancient Sumerian text, ~5000BC
- worm that drunk blood of the teeth and fed on the roots of the jaws
What is Humoral Theory?
- Ancient Greece
- a persons physical and mental constitution was determined by the relative proportions of the four elemental fluids of the body which correspond to the four humors,
- Hippocrates, ‘the father of medicine’, favoured the concept of humoral pathology also referred to the accumulated debris around teeth and to their corroding action.
- He also stated that stagnation of juices in the teeth was the cause of toothache.
What is Chemical Theory?
- 17th and 18th centuries: the concept that teeth are destroyed by acids formed in the oral cavity
- Parmly (1819) proposed that an unidentified chemical agent was responsible for dental caries
- According to this theory, teeth are destroyed by the acids formed in the oral cavity by the putrefaction of protein which produced ammonia and was subsequently oxidized to nitric acid
- Robertson (1895) proposed that dental decay was caused by acids formed by fermentation of food particles around teeth
- fermentation was at this time considered to be a strictly non-vital process
- the possibility that microorganisms were involved was yet recognised
What is parasitic theory?
- Antoni van Leeuwenhoek (1632-1723) – micro-organisms were associated with carious process
- Erdl (1843) - Filamentous parasites in the surface membrane of teeth
- Ficinus (1847) - observed filamentous micro-organisms in carious cavities and called them “Denticolae”
- Dubos (1954) – microorganisms can have toxic and destructive effects on tissue
What is proteolytic theory?
- Introduced by Gottlieb (1947), Frisbie & Nuckolls (1947) and Pincus (1950)
- Caries-like lesions initiated by proteolytic activity at a slightly alkaline pH, and considered that the process involved depolymerisation and liquefaction of the organic matrix of enamel
- Microorganisms invade the organic pathways (lamellae) of enamel and initiate caries by proteolytic action. Subsequently the organic salts are dissolved by acidogenic bacteria
- The protein component of tooth is described first, prior to the loss of tooth minerals.
What is acidogenic theory?
- Willoughby D. Miller 1889
- 1890 Published: “ The microorganisms of the human mouth”
- Caries caused by acids produced by microorganisms of the mouth
- Dental decay is a chemo-parasitic process consisting of two stages:
- i) Decalcification (preliminary step)
- ii) Dissolution (subsequent step)
- Showed that the degradation of carbohydrate containing food resulted in acid formation and tooth tissue destruction
- Demonstrated this process invitro, with isolated oral bacteria and extracted teeth
Miller’s conclusions:
- dental caries caused by multiple species of oral bacteria
- no specific bacteria was implicated—”nonspecific”
- “traditional non-specific plaque hypothesis”
- proper prevention is therefore needed to remove or minimise multiple bacterial species
Limitations:
- Unable to explain site-specificity (esp.smooth surface)
- Does not determine specific bacterial aetiology
- Does not explain why some populations are caries free
- Cannot explain arrested caries
What is specific plaque hypothesis?
- Walter J. Loesche 1976
- In the 1970s, culture-based techniques and microscopy allowed discrimination of specific bacterial species
- It was noticed that the antibiotic kanamycin was particularly effective against cariogenic species such as oral streptococci and reduced caries formation
- removing cariogenic bacteria from the oral cavity using antibiotics could prevent caries
Limitations:
- use of kanamycin resulted in an overall reduction of caries, at some surfaces the caries rate increased
- cariogenic bacteria were not eliminated after treatment
What is Ecological Plaque Hypothesis?
- Marsh, 1994
- Ecological Plaque Hypothesis”: disease is the result of an imbalance in the total microflora due to ecological stress, resulting in an enrichment of some “oral pathogens” or disease-related micro-organisms
- extended the NSPH by Theilade to relate the changes in microbial composition to changes in ecological factors such as the presence of nutrients and essential cofactors, pH and redox potential
- for example, frequent exposure to a low pH, for instance as the result of sugar fermentation, leads to a relative increase of acid-tolerant species.
What is the updated specific plaque hypothesis?
- Theilade 1986
- specific-pathogens” from the SPH were indigenous bacteria and sometimes common bacteria in health
- at this time most researchers seemed to agree that gingivitis was a non-specific inflammatory reaction to a complex indigenous microbiota
- some bacteria could be more virulent than others
What is the Keyes Triad?
Bacteria, Tooth, Diet
What is the tetrad?
Bacteria, Tooth, Diet, TIME
Describe the caries balance
What is infected vs affected dentine?
