Describe the structure and function of teeth, including tooth decay.

a) (i)
Type of tooth: $\boxed{\text{Molar / Premolar}}$
Function: $\boxed{\text{Grinding / Crushing food}}$

a) (ii)

• 1 Blood capillaries: Labelled in the pulp cavity (the innermost part of the tooth, containing nerves and blood vessels).
• 2 Dentine: Labelled as the layer beneath the enamel and surrounding the pulp cavity.

graph TD
    A[Figure 3.0] --> B(Tooth decay)
    A --> C(F)
    A --> D(Sensory nerve)
    A --> E(gum)

    subgraph Tooth Structure
        C -- Enamel --> F_label[F]
        F_label -- Dentine --> Dentine_label[2]
        Dentine_label -- Pulp Cavity --> Blood_capillaries_label[1]
        Blood_capillaries_label -- Sensory nerve --> D_label[Sensory nerve]
    end

    style F_label fill:#fff,stroke:#333,stroke-width:2px
    style Dentine_label fill:#fff,stroke:#333,stroke-width:2px
    style Blood_capillaries_label fill:#fff,stroke:#333,stroke-width:2px

(Please note: I cannot directly edit the image. The labels for "1 Blood capillaries" should point to the pulp cavity, and "2 Dentine" should point to the layer beneath the enamel and surrounding the pulp cavity.)

b) (i)
Part F is the enamel.
Element or Ion 1: $\boxed{\text{Calcium}}$
Element or Ion 2: $\boxed{\text{Phosphate / Fluoride}}$

b) (ii)
Tooth decay is brought about when bacteria in the mouth metabolize sugars from food, producing acids. These acids then dissolve the enamel and dentine, leading to the formation of cavities.

b) (iii)
One way in which tooth decay can be prevented is by $\boxed{\text{brushing teeth regularly (at least twice a day) with fluoride toothpaste}}$.