Answer:
d. Fluoride becomes incorporated into the crystalline structure of teeth, making them less susceptible to decay
Explanation:
Dental caries results when cariogenic (caries-causing) bacteria metabolize carbohydrates or sugars present in the mouth for their energy needs, producing organic acids as byproducts, thus lowering the pH of the plaque biofilm.
The hydroxyapatite of tooth enamel is composed mainly of phosphate ions (PO₄³⁻) and calcium ions (Ca⁺). Under normal conditions, there is a stable equilibrium between the calcium and phosphate ions in saliva and the crystalline hydroxyapatite. At low pH (acidic conditions), there is a shift in equilibrium resulting in the dissolution of hydroxyapatite from tooth enamel, a process known as demineralization. A reverse process called remineralization (the process of incorporation of minerals in tooth enamel) occurs when the saliva, acting as a buffer elevates pH. When equilibrium is shifted to favor continued demineralization, dental caries results.
However, when fluoride is present in saliva, fluorapatite, rather than hydroxyapatite, forms during the remineralization process as fluoride ions replace hydroxyl groups in the formation of the apatite crystal lattice.
Fluorapatite is less soluble than hydroxyapatite making it more resistant to demineralization, even under conditions of low pH. Thus, fluoride acts as an effective anticaries agent.
Answer:
The smell of freshly baked cookies -> olfactory receptors
A person whispering -> auditory receptors
A rainbow outside a window -> cones
Stinky garbage -> olfactory receptors
Night vision -> rods
A loud bang -> auditory receptors
Shapes in a room after the lights are turned off -> rods
<span>A planulae is not one of the three major structures of coral reefs as it is one of the stages in the life cycle of a jellyfish known as the free swimming larvae stage.
Coral reef structures are made up of fringing reefs that grow directly from the shore,
atoll reefs that grow upward usually in a lagoon, and barrier reefs are separated from the land and shore by open water.</span>
