28 - Anatomical + Physiological features of permanent teeth

Question 1

Permanent teeth

Answer 1

There are 32 permanent teeth

Each jaw has:

• 4 incisors: 2 central + 2 lateral
• 2 canines
• 4 premolars
• 6 molars

Question 2

Surfaces of teeth

Answer 2

Buccal - facing cheek/lip

Lingual - facing tongue

Mesial - between teeth towards midline

Distal - between teeth away from midline

Chewing - occlusal for molars + premolars, incisal for incisors + canines

Question 3

Permanent maxillary incisors

Answer 3

• When tooth is Newley erupted ⇢ incisal edges have 3 rounded features called Mammelons ⇢ disappear with time as enamel wears away by friction
• Lingual aspect has a lingual fossa
• Prominent cingulum at gingival
• Mesial + distal aspect present a triangular outline
• Cervical line at border between root + tooth
• Cingulum near cervical line
• Lingual fossa ⇢ large concavity
• 1 canal w/1 apex
• 3 pulp horns
• Root is usually straight ⇢ common curvature towards apex distally + lingually

Question 4

Permanent mandibular incisors

Answer 4

• Crown shape elongated + almost rectangular
• Incisal edge has mammelons after eruption ⇢ disappear from abrasion
• No cingulum

Question 5

Permanent canines

Answer 5

Cornerstone of dentition ⇢ starting angle of the tooth row

Function is to tear food

Most stable teeth

Incisal area forms a cutting tip

Lingual surface = concave ⇢ has medial + distal grooves around cingulum

Darker colour compared to incisors + premolars

Question 6

1st permanent maxillary premolar

Answer 6

2 cusps ⇢ vestibular/buccal + palatal/lingual

Between cusps is an occlusal groove ⇢ extends medially + distally

• Groove separated w/ mesial + distal marginal ridge
• 2 roots + 2 canals ⇢ vestibular/buccal + palatal/lingual

Question 7

2nd maxillary premolar

Answer 7

Similar shape to 1sr

often has 1 root

Question 8

Mandibular premolars

Answer 8

• 1st mandibular premolar differs from all premolars
• missing a lingual cusp
• A strong vestibular cusp is present
• 1 root + 1 canal

Question 9

1st mandibular molar

Answer 9

Largest tooth of lower jaw w/widest occlusal surface

5 cusps ⇢ 3 vestibular + 2 lingual

• Largest cusp ⇢ Medio-buccal
• Intermediate cusp is second
• Distal vestibular cusp is smallest
• Occlusal has a central occlusal groove
• Have deep fissures ⇢ diverse relief w/ very thin enamel often at level of DEJ ⇢ high risk of food retention + plaque formation
• Here is where earliest development of carious lesions begin
• From central groove comes out grooves of neighbouring cusps that run buccally
• In the middle of vestibular surface grooves finish w/pits
• Lateral grooves divide occlusal surface of 5 separate cusps
• Medial surface is slightly concave
• Posterior surface almost straight

2 roots + 3 root canals - Medial 2 channels, distal 1 channel

Question 10

2nd mandibular molar

Answer 10

Repeats form of 1st mandibular molar but smaller

4 cusps ⇢ 2 vestibular, 2 lingual

Between cusps are vestibular/buccal + lingual grooves

Many variations in roots

Question 11

1st maxillary molar

Answer 11

Square shape w/4 cusps

Carabelli’s cusp is 5th cusp ⇢ ⅓ below occlusal surface

Vestibular groove between tubercles, ends w/pits

3 roots ⇢ 2 vestibular, medially + distally + curving towards each other + 1 lingual

• Roots are spread apart + have 1 channel each

Oblique ridge on occlusal surface ⇢ connects mesial-lingual ridge w/ distal buccal ridge

Cusps are higher + sharper w/deeper fissures

Question 12

2nnd maxillary molar

Answer 12

• 12 year tooth
• Shape of occlusal surface + roots is similar to 1st maxillary molar
• smaller size
• lack of Karabelli’s cusp
• undulating occlusal relief
• more grooves + pits