Premolars Flashcards
Premolars func
o Work with the molars in mastication and maintaining the vertical dimension of the face
o Erupt in positions previously occupied by deciduous molars, thus they are known as succedaneous
teeth
Maxillary First premolar
▪ Very brittle due to the presence of the mesial marginal groove, the mesial concavity, and two spindly roots
• It is protected/supported by the canine
Facial View max 1
- Widest premolar
- Buccal cusp tip is slightly distal of the root axis line
- Buccal cusp has a longer mesial cusp ridge than distal cusp ridge
- It’s the most pointed cusp in the dentition
Lingual View max 1
- Crown and root is narrower on the lingual side
- The lingual cusp is shorter and bends mesially
- The lingual root is shorter than the Buccal root
Proximal View max 1
- Prominent mesial concavity cervical to the contact area
- Buccal cusp is longer than the lingual
- Mesial marginal groove is always present
- Has 2 roots 61% of the time
- Because of the mesial marginal groove, mesial concavity, and two spindly roots – it is very brittle - protected by the canine
Occlusal View max 1
- Lingual cusp offset mesially
- Long central developmental groove runs mesiodistally, crosses the transverse ridge and ends in pits in the triangular fossae
- There are few supplementary grooves
Facial View max 2
The Buccal cusp is not as long or as pointed
• The cusp tip is offset mesially (max 1st offset distally)
o Mesial cusp ridge shorter than the distal cusp ridge
Lingual View max 2
- Lingual cusp is longer than the lingual cusp of the first max PM
- Lingual and Buccal cusps are nearly equal in size
- Lingual cusp offset mesially
Proximal View max 2
- One root
- NO mesial concavity
- NO mesial marginal groove
- Distal root depression deeper than mesial root depression
- Cusps are nearly equal in size
Occlusal View max 2
- Central groove is shorter and more irregular than the first max PM
- No mesial marginal groove
- Lingual cusp offset mesially, but not as much
Mandibular premolars special characteristics
▪ The first man PM is smaller than the second (opposite of maxillary PMs)
▪ First PM resembles, and functions with the canine
▪ Second resembles, and functions with the molars
▪ The two mandibular PMs are less alike than the two max PMs
▪ Crowns are tilted lingually– greatest lingual inclination in the mandibular arch
▪ Buccal cusp larger than the lingual
▪ First PM develops from 4 lobes
▪ Second PM develops from 5 lobes in most instances
Buccal View man 1
• Cusp tip pointed and slightly mesial to the midline of the tooth
• Mesial contact area is more cervical than the distal contact area
o Only tooth in permanent dentition that has this feature
Lingual View Man 1
• Miniscule lingual cusp
• Entire occlusal surface, and most of the mesial and distal surfaces can be seen from this view
• Mesiolingual developmental groove and prominent transverse ridge
o Hallmark trait
Mesial View man 1
- Rhomboidal outline (as are all mandibular posterior teeth)
- Tip of Buccal cusp is nearly centered over the root
- Tip of the lingual cusp is in line with the lingual border of the root
- Crest of curvature on lingual and buccal surfaces are in or near the middle third
- Mesiolingual groove is seen
- Short root but it often has a deep developmental groove
Distal View man 1
- No developmental groove
* Distal marginal ridge is more occlusal than the mesial so you can’t see as much of the occlusal surface
Occlusal View Man 1
- Outline is diamond shaped
- Middle labial lobe makes up the bulk of the tooth
- Distal portion is described as being a larger arc than the mesial side, with a broader contact
- Sharp lingual convergence
Mandibular Second Premolar characteristic
▪ Larger than the first premolar and has a longer root
▪ Has two common forms
• three cusp type (more common)
• Two cusp type
Buccal View man 2
• Buccal cusp is shorter (more blunt) than the first premolar
Lingual View man 2
- Usually a ML and DL cusp present
- ML is larger and there is a lingual groove separating the cusps
- Lingual groove is centered over the root
- Very little convergence
Mesial View Man 2
- Not similar to mandib first PM
- Marginal ridge at right angle to the long axis of the tooth
- No mesiolingual developmental groove
Distal View man 2
- Two cusps are visable
- Crown is tipped distally so more of the occlusal surface is visible from the distal view than from the mesial view (characteristic of ALL posterior teeth)
Occlusal View man 2
• 3 cusp type – square outline
o B > ML > DL in size
o Cusps separated by deep developmental grooves that form a “y” on the occlusal surface (mesial, distal, and lingual developmental grooves)
• 2 cusp type – round with some lingual convergence
o 1 lingual cusp
o Central developmental groove is often crescent shaped
