Fluoride and the Tooth surface

Fluoride and Tooth Surface

• Fluoride, a naturally occurring element, is important in oral health.
• Hydroxyapatite makes up 96% of tooth enamel.
• Hydroxyapatite is a calcium phosphate compound.
• The critical pH for hydroxyapatite is 5.5.
• Below this pH, demineralization occurs.
• Fluoride's interactions with tooth enamel involve multiple stages and mechanisms: pre-eruptive (systemic fluoride), matrix secretion, maturation, and post-eruption (topical fluoride).
• Fluoride is absorbed into enamel, making it more resistant to demineralization.
• Fluoride helps form fluoroapatite, which is more stable and resistant to acid attacks than hydroxyapatite.
• Fluoride reduces caries incidence as it makes teeth more resistant to further demineralisation.
• It is topical fluoride's role in remineralisation that is critical in maintaining a healthy tooth structure.
• Professional and self-applied fluoride are noted as essential in caries prevention.

GDC Learning Outcomes

• Students should describe the properties of relevant medications and therapeutic agents and discuss their application to patient management.
• Students should provide comprehensive and accurate preventative education to patients, encouraging self-care and motivation.
• All patient care should follow a preventative approach for long-term oral health consideration
• Students should advise on and apply relevant preventative materials and treatment options.
• Health promotion, relating to the community and individuals in a changing environment, needs to be discussed and evaluated.

Pre-Reading

• The aetiology of dental caries involves the interaction of susceptible tooth surface, plaque bacteria, and fermentable carbohydrates over time.
• Histology of enamel and dentine lectures are essential for understanding the topic.

Intended Learning Outcomes

• Students will list key milestones in fluoride history and its use in caries prevention.
• Students will outline and describe stages in fluoride deposition.
• Students will describe fluoride modes of action.
• Students will explain how fluorosis occurs.
• Students will identify and assess fluorosis severity.

Refreshers Session

• Normal enamel is primarily composed of hydroxyapatite.

• Hydroxyapatite comprises 96% of enamel.

• Enamel has a lattice structure, primarily made up of phosphate and calcium ions.

• Hydroxyapatite structure is indicated with Ca10 (PO4)6 (OH)2.

• Demineralisation occurs when pH drops below 5.5 for hydroxyapatite, causing tooth surface breakdown into component ions (Ca2+, PO43-, OH-).

• Frequent acid attacks increase demineralisation risk; infrequent attacks reduce it.

Fluorine

• Fluorine, a halogen, has atomic number 9 and is highly reactive with metals.
• Naturally found in water, rocks, soil, and tea.

Fluoride History

• Several key milestones in fluoride history, including research, experiments, and the development of water fluoridation for public health.
• Identification of Colorado stain led to its investigation.
• Water sampling showed higher fluoride content linked to mottling, suggesting fluoride's possible protective role.
• Studies linking fluoride to reduced caries rates, including "shoe leather" studies and the 21-city studies.
• Various campaigns, including by the Royal College of Physicians, were instrumental.
• Different reports, such as the York and Knox reports, evaluated the evidence and links between fluoride and cancer/bone fractures.
• Cochrane review (2015) analysed current evidence on fluoride's effect on dental caries.

Colorado Stain-1916

• Dr Frederik McKay identified a staining on some teeth.
• He sought further investigation from GV Black, whom published a paper on the findings.

Water Sampling -1931

• After McKay's findings, Churchill identified higher fluoride content connected to enamel mottling.

Identification Fluoride may reduce caries – 1932

• McKay proposed the same substance causing enamel mottling could also reduce caries.

Shoe Leather Studies-1930-1940

• Dr H Trendley-Dean studied links between fluoride, mottling and caries reduction following research from McKay.

Knox Report -1985

• Reviewed papers on fluoride and cancer, concluding no strong link existed.

York Report-2000

• Reviewed various studies involving water fluoridation,finding no link to bone fractures or other health problems.

Modern Day

• Controversy exists regarding the use of artificial water fluoridation
• About 10% of the UK population currently has fluoride in their water supply.
• Patients questions about the continued use of fluoridation continue

How does Fluoride prevent caries

• Fluoride is absorbed into the tooth surface which makes it more resistant to demineralization.
• This occurs in stages, including pre-eruption, matrix secretion, maturation, and post-eruption.
• Fluoride incorporation, reduced surface wettability, and antibacterial effects are different ways it prevents root caries.

Fluorosis

• Fluoride ingestion can result in enamel defects.
• In excess, it can lead to enamel mottling or discoloration (fluorosis).
• The precise effects depend on the dose, ingestion duration, and patient age at exposure.
• Fluorosis can be graded, ranging from slightly visible changes to severe discolouration and pitting on teeth.

Mechanism of fluorosis

• Excessive fluoride can impede enamel maturation, creating more porous enamel
• Fluoride can cause discolouration/staining due to the hypomineralisation of the tooth enamel.
• There are more causes of enamel defects besides fluorosis, such as genetics, trauma, disease, and drug interactions, so these must be taken into consideration.

What are the aetiological agents

• Dietary fluoride supplements are a cause of oral fluoride intake.
• Drinking water, especially fluoridated water, contributes to fluoride ingestion.
• Toothpastes, particularly those containing fluoride, have contributed to fluoride intake
• Topical applications can also be a cause of oral fluoride exposure

Is it fluorosis

• Several criteria distinguish fluorosis from other enamel defects.

Indices for recording fluorosis

• The Dean Index and Thylstrup and Fejerskov indices are used to evaluate the extent of fluorosis.
• These grades range from 0 (no fluorosis) to 9 (significant fluorosis with enamel loss) and assess translucency.

Summary

• Stages of fluoride deposition: Calcification stage(systemic), post-eruption (topical).
• Fluoride actions: Action on hydroxyapatite, action on enamel surfaces, action on bacterial enzymes, action on tooth morphology.

Where does the fluoride come from?

• Topical fluoride applications provide a reservoir of fluoride in saliva.
• Fluoride binds to calcium in saliva to form CaF2.
• When acid attacks and pH drops, fluoride is released to help remineralisation

Ways to ensure a regular supply of low-level fluoride

• Different topical fluoride sources (toothpastes, mouth rinses, fluoride varnishes, restorative materials, and fluoride tablets) with corresponding fluoride levels and prescription requirements.
• Water fluoridation can also contribute but is less topical.

How does fluoride work in real life?

• The incorporation of fluoride into tooth enamel.
• The change in pH levels affecting the formation of hydroxyapatite and fluorapatite.

Does Fluoride have any other mechanisms of action?

• Fluoride can potentially have antibacterial effects and reduce bacteria adhesion to enamel surfaces

Action on enamel surface

• Fluoride can decrease enamel surface energy, affecting wettability and inhibiting bacterial adhesion, reducing plaque formation

Action on tooth morphology

• The shape and structure of teeth can potentially be altered by fluoride exposure, sometimes improving cleansability.

Root Caries Recap

• Gum recession exposes dentine and cementum, surfaces that are less mineralised to decay faster than enamel.
• Xerostomia, limited saliva, and radiotherapy can increase root caries susceptibility.

How does Fluoride prevent root caries

• Fluoride can incorporate into surface during remineralization.
• Fluoride can reduce surface wettability and potentially have antibacterial effects to prevent root decay.

What does the research say

• Professionally-applied fluoride (silver diamine fluoride, fluoride varnish), as well as self-applied fluoride (mouth rinses), can prevent root caries.