OE L24 Fluoride and Development

Question 1

Name 7 types of delivery of fluoride.

Answer 1

• Topical fluoride varnish
• Dentrifices
• Fluoridated water supplies
• Fluroide supplements
• Restorative materials e.g. glass ionomers, which leach fluoride
• Food and drink e.g. homogenised fish
• Industrial pollution, fluoride in atmosphere and food chain

Question 2

Describe the systemic uptake and secretion of fluoride.

Answer 2

• Absorbed as hydrogen fluoride in the intestines and distributed in plasma
• 80% processed and excreted by kidneys
• Fluoride from plasma absorbed into mineral component of dentine, enamel and bone

Question 3

How much fluoride is in water supplies?

Answer 3

In areas with fluoridated water, the levels are 1ppm.

Question 4

What are the benefits of fluoridated water?

Answer 4

• Increased mineral resistance to acid

- Reduction in bacteria

Question 5

How can acute doses of fluoride treat osteoporosis?

Answer 5

Stimulates osteoblast activity and increases trabecular bone mass.

Question 6

What is the cause of fluorosis?

Answer 6

Prolonged exposure to fluoride 2ppm and above. E.g. children ingesting toothpaste

Question 7

How does duration of high level fluoride exposure affect outcome?

Answer 7

Short duration = acute, toxic effects

Long duration = chronic exposure

Question 8

How can fluoridated water cause teeth fracture?

Answer 8

Mineral will become more brittle, therefore lends itself to fracture.

Question 9

How does fluoride affect enamel during early stages of amelogenesis?

Answer 9

Exposure during development before mineralisation has begun:

• Hypomineralisation
• Creates white mottled patches
• Teeth more porous and susceptible to staining and pitting
• Enamel is reduced in thickness
• Teeth suscpetible to erosion

Question 10

Does fluoride affect ameloblast proliferation?

Answer 10

No.

Question 11

Does fluoride affect proteins secreted by ameloblasts?

Answer 11

Yes.

• Can cause a reduction in proteins secreted during the secretory phase
• Very few/no enamel rods form

If this occurs chronically, the mineral front moves along and there will be very little/no HAP deposition.

Question 12

Does fluoride affect the proteolytic processing of enamel proteins?

Answer 12

Yes.

• Fluoride inhibits activity of proteases responsible for removal of enamel proteins
• Means no axial migration or growth of enamel rods prior to matruation stage

Question 13

What are the effects of fluoride on pre-formed mineral?

Answer 13

• Once development is complete, fluoride can subsitute hydroxyl ion in HAP creating fluorapatite
• Crystal structure preferrable, more organised and tight formation - makes mineral more acid resistant

Beneficial event will only occur if fluoride is incorporated at end stages of amelogenesis- not earlier on.

Question 14

Dental fluorosis can also affect dentine, what 2 types of events can cause this?

Answer 14

• Single high dose

- Chronic exposure

Question 15

How does a single high dose of fluoride during development affect dentine?

Answer 15

• Creates zones of hypomineralisation followed by zones of hypermineralisation
• Zone pattern persists in the fully formed tissue

Question 16

How does chronic exposure to fluoride during development affect dentine?

Answer 16

• Leads to hypomineralisation alone
• Reduced dentine thickness
• No effect on post mitotic odontoblasts
• Increases proliferation of preodontoblasts

Question 17

How does fluoride cause hypomineralisation of dentine?

Answer 17

• Fluroide increases proliferation of odontoblasts, increases production of proteins which inhibit mineralisation
• Reduces sulphation levels of glycosaminoglycans
• MMPs reduced (MMPs remove inhibitors of mineraliation in dentine in health)

Question 18

How do high fluoride levels affect phosphoryns?

Answer 18

Phosphoryns = dentine phosphoprotiens

Fluoride:

• Reduces phosphorylation
• Means phosphoryns cannot bind as much calcium and deposit at gap zone
• Reduced mineral deposition = hypomineralisation

Question 19

What is skeletal fluorosis?

Answer 19

As bone is constantly being remodelled, fluoride is able to exert an influence.

• Fluroide causes hypercalcification of trabecular (cancellous bone).
• Fluoride can also cause calcification of ligaments leading to stiff joints.

Question 20

What is the cellular mechanism behind skeletal fluorosis?

Answer 20

• Fluoride increases preosteoblast proliferation into osteoblasts
• Stimulates alkaline phosphatase acitivty, reduces MMP activity therefore leading to bone formation
• Activates calcium channels = hypermineralisation
• Can cause brittle bones
• Reduced osteoclast activity due to decreased acid phosphatase activity

Overall imbalance between bone formation and resorption.