maxillary second premolar  l tooth crown & root morphology revision for dental students

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Morphology of tooth crown and root of Maxillary Second Premolar

Buccal Aspect of tooth crown and root

• Maxillary first and second premolars appear similar in all aspects with few exceptions. Maxillary second premolars appear smaller or almost equal in overall dimensions (cervico-occlusally and mesio-distally) than the maxillary first premolars.
• Outlines of the crown surfaces between contact areas and cervical line are both smooth convex curves eventually giving an oval appearance.
• Buccal cusp tip will be more rounded and short than the buccal cusp tip of the maxillary first premolar. It is usually placed mesial to the mesiodistal long axis creating a short mesial cuspal ridge than the distal cuspal ridge.
• Both proximal contact areas are at a level occlusally high at the junction of occlusal and middle third of the crown (same level).
• Buccal cusp ridge, mesial and distal developmental depressions are less conspicuous on the maxillary second premolar.
• Cervical outline of the crown is smoothly convex.
• Maxillary second premolar has a single root. This converges evenly toward a relatively blunt apex which may be centered or slightly distal to the mesiodistal axis of the tooth.

Palatal Aspect of tooth crown and root

• Palatal outline is the inverse image of the buccal outline.
• Palatal surface appears more convex and narrower mesiodistally than buccal aspect. It is positioned more mesially making the mesial slope appear smaller than distal slope.
• Palatal cusp appears slightly longer and sharper than the buccal cusp. Palatal cusp tip will be in line with the tip of the buccal cusp.
• Cuspal ridges of the palatal cusp will be placed more occlusally as those of the buccal cusp and will present the same angle of slant from the tip of the cusp. Cervical outline and proximal contours appear more rounded and oval in shape.
• Narrow palatal root shows a blunt apex and distal tilt to the long axis of the tooth.

Mesial Aspect of tooth crown and root

• Trapezoid outline with the shorter parallel side at the occlusal and the longer parallel side at the cervix.
• Buccal cusp tip is more pointed than the palatal cusp tip and both cusps mark almost the same height. Cusp tips are located wide apart creating a greater buccopalatal dimensions on the occlusal aspect of the tooth.
• Triangular ridges of buccal and palatal cusps are less deep than the maxillary first premolar. Associated mesial marginal ridge is not demarcated by any developmental grooves.
• Mesial marginal ridge is more occlusally placed than distal marginal ridge.
• Buccal crest of curvature appears convex and placed buccal to crest of buccal cervical ridge on the cervical third of the tooth while palatal crest of curvature appears at the middle of middle third of the crown. Mesial contact area is about 1.0 mm cervical to the crest of the mesial marginal ridge and buccal to the buccopalatal axis of the tooth.
• There may be several supplemental grooves extending buccally and palatally along the central groove giving the occlusal table a “wrinkled” appearance.
• Cervical line curves occlusally more on the mesial aspect of the tooth.
• Single root shows a blunt apex which appears buccal to bucco palatal long axis of the tooth. Shallow longitudinal depression is evident limited only on the mesial surface of the root.

Distal Aspect of tooth crown and root

• Distal outline will be the inverse of the mesial outline.
• Distal contact area is located at the center of the tooth buccopalatally.
• Cervical line curves less occlusally.
• Single root with similar morphology as mesial aspect of the tooth. However, deep developmental depression on the distal aspect of the root marks its variation.

Occlusal Aspect of tooth crown 

• Overall, the crown outline of the occlusal aspect of maxillary second premolars appears more oval, less angular and smaller in dimensions.
• Buccal and palatal ridges are less conspicuous and more rounded on viewing from occlusal aspect of maxillary second premolars. Buccal and palatal cusp tips are slightly mesial to the long axis of the tooth. Both cusp tips are at the same height although, placed away from each other.
• Triangular ridges are approximately the same length and the point at which they meet will be located slightly palatal to the buccopalatal axis of the crown. Rarely will there be a true transverse ridge since the two triangular ridges will be separated by a central groove.
• Mesial and distal cuspal ridges of the buccal cusp are relatively straight and meet at an obtuse angle while both cuspal ridges of the palatal cusp present a continuous elliptical arc.
• Mesial and distal marginal ridges appear more rounded and converge palatally to give a rectangular occlusal form.
• Relatively short central groove runs between mesial and distal irregular triangular fossae when compared to the maxillary first premolar.
• Mesial contact area is located at the junction of buccal and middle third while the distal contact area is located on the middle third placed more palatally to the long axis of the tooth.
• There may be several supplemental grooves extending buccally and palatally (mesiobuccal supplementary groove, mesiopalatal supplemental groove, distobuccal supplementary groove and distopalatal supplemental groove) along the central groove giving the occlusal table a “wrinkled” appearance