fluoride and mineralised tissues - developmental aspects

Question 1

sources of fluoride

Answer 1

• Dentifrices
  
  • Toothpastes
• Fluoride supplements
  
  • Tablets daily
    
    • systemic
• Fluoridated water supplies
• Restorative materials
  
  • E.g. glass ionomers
  • Leak out slowly
  • Remineralise enamel and dentine
• Food and drink
  
  • E.g fish (homogenised) and tea
• Industrial pollution
  
  • High level of fluoride in water - gets into food chain

Question 2

what are the beneficial effects of fluoride?

what is important in producing these beneficial effects?

Answer 2

• Reduction in dental caries (1ppm)
  
  • Increase mineral resistance to acid of enamel
  • Reduction in bacteria
• Treatment of osteoporosis
  
  • Single acute dose
  • Serum levels of 10-8M
    
    • Very low level
  • Stimulus of osteoblasts increasing trabecular bone mass.

To have fluoride producing beneficial effects - the level must be kept very low

Question 3

at what level may fluorosis occur?

Answer 3

Excess prolonged exposure to fluoride (2ppm and above)

Question 4

describe dental fluorosis and the effect on enamel

Answer 4

• Hypercalcification at sites where mineralisation has already begun followed by hypomineralisation at other sites where mineralisation cannot proceed.
  
  • Hypomineralisation leaves teeth more porous, susceptible to dietary staining and pitting.
  • Fluoride causes reduction in protein secretion and synthesis - leads to hypomineralisation
  • Areas of the tooth where there is loss of the proteins - fluoride is incorporated into the crystals forming fluorapatite
• Reduced thickness of enamel
• White spots

Question 5

describe dental fluorosis and the effect on odontoblasts

Answer 5

• No effect on post mitotic odontoblast
• Increase proliferation of preodontoblasts
• Increased production of dentine of inferior quality
• Reduction in mineral deposition

Question 6

describe dental fluorosis and the effect of high doses and chronic exposure to fluoride on dentine

Answer 6

Single high dose in dentine

• Zones of hypomineralisation followed by zones of hypermineralisation, with both zones persisting in the fully formed tissue
• Consequence of incremental deposition of dentine.

Chronic exposure to high [F]

• Leads to hypomineralisation.
• Reduced thickness of dentine.

Question 7

describe dental fluorosis and the effects on proteoglycans and phosphyoryns in dentine

Answer 7

proteoglycans

• Reduction in sulphation levels
• Reduction in GAG chain length
  
  • Cant bind at high enough levels to channel to the gap zones
  • Less effective at regulating mineralisation in collagen fibres
• Change in the ratio of DS:CS

phosphoryns

• Reduction in the phosphorylation
  
  • It doesn’t bind as much calcium and phosphate
  • Leads to hypomineralisation
    
    • as - less is delivered to gap zones

Question 8

what is skeletal fluorosis?

Answer 8

• Increased density of trabecular bone - hypercalcification.
• Calcification of ligaments leading to stiffness of joints.
• As bone is constantly remodelling fluoride can exert its influence on both growing and fully formed bone.
  
  • Differs from teeth as fluoride only has an effect on teeth during development
  • Fluoride can affect bone at any stage of life

Question 9

what is the effect of fluoride on cellular activity

Answer 9

• Increases proliferation of preosteoblast cells which then mature into osteoblasts.
• Stimulate alkaline phosphatase activity.
  
  • Removes inhibitors of mineral deposition
• Possible reduction in MMP activity?
  
  • Unproven
  • May affect remodelling process
• Activation of calcium channels (shown in bone and odontoblasts).
• Decreases acid phosphatase activity – reduced osteoclast activity
  
  • Indicates that fluoride is being toxic and inhibits osteoclast activity