Dentistry Revision

What is an atom?

The smallest unit of matter made of protons, neutrons, and electrons

What is atomic number?

The number of protons in the nucleus

What is mass number?

The total number of protons and neutrons

Where are electrons located?

In shells (orbitals) around the nucleus

Why are valence electrons important?

They determine chemical bonding and reactivity

What is an ionic bond?

Transfer of electrons between a metal and a non-metal

Give an example of ionic bonding in dentistry

Calcium phosphate in tooth enamel

What is a covalent bond?

Sharing of electrons between atoms

Where are covalent bonds found in dentistry?

Polymers and composite materials

What is metallic bonding?

Positive metal ions in a sea of delocalised electrons

Why are metals ductile?

Metallic bonding allows atoms to slide past each other

Name the four main classes of dental materials

Metals, ceramics, polymers, composites

What is a biomaterial?

A material that safely interacts with biological tissues

What is an alloy?

A mixture of two or more elements, at least one being a metal

What is interstitial alloying?

Small atoms fit into spaces between metal atoms

What is substitutional alloying?

Atoms of similar size replace metal atoms in the lattice

Give examples of dental alloys

Gold alloys, cobalt-chromium, nickel-chromium, stainless steel

Which metal has the best biocompatibility?

Titanium

What is plastic deformation?

Permanent change in shape when stress is applied

What is a dislocation?

A defect in the crystal lattice that allows slip

Why does repeated bending cause metal fracture?

Fatigue due to dislocation movement

What is a thermoplastic polymer?

A polymer that softens when heated and hardens when cooled

What are linear polymer chains?

Straight chains that are more flexible

What are branched polymer chains?

Chains with side branches that are more rigid

What type of bond holds polymers together?

Covalent bonds

What type of bonding is found in ceramics?

Ionic and covalent bonding

Ceramics are strong in which type of stress?

Compression

Why are ceramics brittle?

Limited dislocation movement

What does biocompatibility mean?

Ability of a material to function without causing adverse biological reactions

Give examples of biocompatibility problems

Toxicity, allergic reactions, corrosion products

What does SOP stand for?

Standard Operating Procedure

What does SAP stand for?

Safe Assessment or Safe Operating Procedure

Why is safe handling of dental materials important?

To protect patients and clinicians

What happens when a metal cools?

Atoms arrange into a crystalline structure forming grains

Stainless steel corrosion resistance is due to what?

Formation of a protective chromium oxide layer

What is an elastomeric material?

A rubber-like material that stretches and returns to shape