OPERATIVE Dental Caries Flashcards
which cells produce reparative dentin?
odontoblasts; they seal off dead tracts
___ is the process of occlusion of the dentinal tubules by peritubular dentin
sclerosis
dental caries is a multifactorial, transmissible infectious oral disease caused primarily by the complex interaction of ___ with ___on the tooth surface over time
cariogenic oral flora (biofilm) with fermentable dietary carbohydrates
T or F:
not all people with teeth and biofilm who consume carbohydrates have caries over time
true
at the tooth level, caries activity is characterized by ___
localized demineralization and loss of tooth structure
how does cariogenic bacteria cause dental caries?
- they metabolize refined CHOs and produce acid by-products, which can lower the pH if present for long enough
- low pH drives calcium and phosphate from the tooth to the biofilm, resulting in a net loss of minerals by the tooth (demineralization)
what is considered the critical pH level for enamel and dentin (below which demineralization occurs)?
enamel is 5.5, dentin is 6.5
what is the specific plaque hypothesis?
- not all of the 300 species of bacteria in the oral cavity can cause caries
- bacteria that generate plaque biofilm resulting in caries are considered to be cariogenic organisms
- all plaque biofilm is not cariogenic
is strep mutans gram positive or negative? motile or nonmotile? is it cariogenic?
cariogenic nonmotile gram positive
which bacterium is believed to be the primary causative agent of initial caries?
strep mutans
strep mutans adheres to ___. it’s ___ enzyme causes the formation of an extracellular polysaccharide, which allows it to stick to tooth surfaces. it converts sucrose to ___ and ___, which extrude from the bacterium and stick to the tooth. it produces and tolerates acid, and ultimately metabolizes sucrose to an end product of ___.
- enamel
- glucosyltransferase
- fructans and glucans
- lactic acid
strep mutans thrives in a ___-rich environment
sucrose
strep mutans ultimately converts sucrose for what two purposes?
tooth adherence and acid production
strep mutans produces ___, which kill off competing organisms
bacteriocins
in the formation of enamel caries, ion transfer continuously occurs at the ___ interface. initial decalcification occurs at the ___. how long might it take before enough decalcification occurs to cause surface integrity loss (cavity)?
- biofilm-enamel
- subsurface
- 1-2 years
in the formation of dentinal caries, once enamel cavitation has occurred, the underlying dentin has already been affected by the progression of the destruction. at this point, what organism becomes the primary agent for further destruction of the dentin?
lactobacillus
if sugars are the key to success of cariogenic bacteria (a major pathologic factor), then ___ is a major block barring those same bacteria (a major protective factor)
saliva
approximately how much saliva is formed each day?
1.5L
what are the protective mechanisms of saliva?
bacterial clearance, buffering action, antimicrobial actions, remineralization
how does saliva aid in bacterial clearance?
-glycoproteins (large CHO protein molecules) in saliva cause some bacteria to agglutinate and then be removed by swallowing the saliva
describe saliva’s buffering action
saliva contains urea and other buffers that help to dilute any plaque acids
what are the 4 proteins/enzymes/antibodies in saliva that discourage or even kill bacterial growth?
- lysozyme
- lactoferrin
- lactoperoxidase
- type A secretory immunoglobulins
what is the role of lysozyme in saliva?
destroys cell walls and causes membrane permeability of bacteria
what is the role of lactoferrin in saliva?
- actively binds iron, which is important for bacterial enzyme production and function
- it may also destroy strep mutans
what is the role of lactoperoxidase in saliva?
it inactivates some bacterial enzymes
what is the role of type A secretory immunoglobulins in saliva?
they are antibodies secreted by saliva that fight against strep mutans attacks
what components of saliva aid in remineralization?
- calcium, phosphate, potassium, and varying concentrations of fluoride ions
- some salivary proteins, such as statherin, cystatins, histatins, and proline-rich proteins
what are 4 problems with reduced salivary flow?
- prolonged pH depression (decreased buffering)
- decreased antibacterial effects
- decrease in ions available for remineralization
- decreased elimination of microorganisms
what are the 4 objectives of dental caries diagnosis?
- identify caries lesions that need surgical treatment
- identify caries lesions that need nonsurgical treatment
- identify patients who are at high risk for caries and need special preventive treatment
- emphasis must shift from detection only of cavitations to the detection of high caries risk and predictions of caries progression
what are the factors that identify a high caries risk patient?
- high strep mutans count
- any two of the following: two ore more active caries lesions, large numbers of restorations, poor dietary habits, low salivary flow, poor oral hygiene, suboptimal fluoride exposure, or unusual tooth morphology
what factors put a patient at high risk of developing a new cavitated lesion?
- high strep mutans count
- any two of the following: two or more active carious lesions, numerous restorations, poor dietary habits, low salivary flow
when should bacteriologic testing for strep mutans be done on a patient?
- pt has one or more medical health history risk factors
- pt has undergone antimicrobial therapy
- pt presents with new incipient lesions
- pt is undergoing orthodontic care
- pt’s treatment plan calls for extensive restorative dental work
what are the objectives of prevention of carious lesions?
- improve biofilm conditions to favor remineralization and hinder demineralization
- realize that the repair of a caries lesion does not cure the disease caries
intense application of ___ on a short term basis helps in the prevention of dental caries
antimicrobials
what are the beneficial effects of fluoride?
- bactericidal
- provides fluoride ion for remineralization forming fluoroapatite, which is more resistant to acid attack that hydroxyapatite enamel
what are the 5 types and sources of fluoride?
community fluoridated water systems, rinses, gels, varnishes, and toothpastes
saliva can aid in the prevention of dental caries. what are some ways salivary flow can be increased?
- alter saliva-reducing medications if possible
- use saliva stimulants
- sugar-free gums and lozenges
- saliva substitutes
- encourage diet high in protein and vegetables
- use pilocarpine hydrochloride or cevimeline hydrochloride if needed
describe sucrose modifications that can aid in the prevention of dental caries
must decrease frequency - more important that decreasing quantity
a single exposure to sucrose for a caries-active mouth can result in pH being reduced below ___ for a sustained period because of the rapid metabolism by ___
below pH of 5.5, strep mutans
is there strong evidence for xylitol as a caries preventative agent?
it is controversial
___ is a natural sugar from birch trees (five carbon sugar)
xylitol
how does xylitol aid in the prevention of dental caries?
- keeps sucrose molecule from binding with strep mutans
- strep mutans cannot ferment xylitol
how does oral hygiene aid in the prevention of dental caries?
disrupts plaque biofilm formation
how to sealants aid in the prevention of dental caries?
remove habitats for strep mutans
what are the 8 ways dental caries can be prevented?
antimicrobial, fluoride, saliva, sucrose, xylitol, oral hygiene, sealants, and restorations
T or F:
when cavitated lesions are present, antimicrobial agents should be used before lesions are restored
- false, they should be restored first
- if antimicrobials are used first, they disrupt the normal flora and allow the virulent organisms in the protected (cavitated) areas to flourish on now-unprotected tooth surfaces
restorations remove large nidi of infectious organisms, but more importantly, they remove ___
habitats for more bacterial adherence
if many cavitated lesions are present, ___ are required. these may eventually be replaced with ___
- caries-control restorations (w/glass ionomer)
- permanent restorations (with composite, amalgam, or indirect materials)
T or F:
restorations alone do not cure the disease caries
true
where should sealants be applied?
to at-risk molars and premolars
what are the options for intense, short term use of agents in prevention of carious lesions?
- chlorhexidine (evidence for chlorhexidine as a caries preventive agent is controversial)
- fluoride varnishes
what are the options for continuous, long term use of agents in prevention of carious lesions?
- xylitol products
- calcium phosphate products (CPP-ACP paste or rinse)
what is the protocol for fluoride rinses as an aid in prevention of dental caries?
- begin after chlorhexidine is finished
- use at different times that for brushing twice a day
- increase remineralization
what should be done at the recall appointment (3 months after chlorhexidine or fluoride varnish application) for high caries risk patients?
- identify strep mutans counts
- clinical exam (check sealants and caries control if used, 3-month recalls)
caries is a bacterial ___
infection
