Maxillary First Premolar: Dental Morphology Made Easy

The maxillary first premolar is the first posterior tooth in the maxillary dental arch. There are four premolars in the maxillary dental arch two in each quadrant. The term premolar is used for these teeth because these teeth are anterior to the permanent molars. The maxillary first premolar has two cusps one buccal and one palatal cusp. The number of roots is two one buccal and one palatal root. The other premolars maxillary and mandibular usually have a single root. The first premolar because of its morphology and position in the dental arch assist canine in the tearing function and molars in the grinding function. The first premolar has succeeded the deciduous maxillary first molar tooth.

Development and Eruption of Maxillary First Premolar

Following is a summary of the chronology of development and eruption of the maxillary first premolar.

• Beginning of calcification of first premolar: 1 ½ year
• Crown completion of first premolar: 5 – 6 years
• Eruption of the maxillary first premolar: 10 -11 years
• Root completion of the first premolar: 12 – 13 years

Buccal Aspect

• The maxillary first premolar resembles canine from the buccal aspect.
• The curvature of the cervical line or cementoenamel junction is less as compared to the teeth that are present anterior to the maxillary first premolar.
• Two cuspal slopes are associated with the buccal cusp those are the mesial cuspal slope and the distal cuspal slope. The mesial cuspal slope of the maxillary first premolar is longer as compared to the distal cuspal slope.
• The buccal cusp is longer and pointed and the only visible cusp from the buccal aspect.
• There are two developmental depressions on the buccal aspect. Mesiobuccal and distobuccal developmental depressions. In between these developmental depressions, a ridge called buccal ridge is present.
• The buccal root is long and cone shape and bears some resemblance with the canine root. The length of the buccal root is less than the root length of the maxillary canine. The buccal root in the apical one-third portion slightly curves in a distal direction.
• The mesial outline of the crown is slightly concave while the distal outline is straight.

Lingual Aspect

• The crown is narrow mesiodistally as compared to the buccal aspect.
• Due to this reduced mesiodistal dimension of the crown on the lingual aspect part of the mesial and distal aspects of the crown is visible from the lingual aspect.
• The lingual cusp is shorter in height as compared to the buccal cusp. Therefore, the buccal cusp along with the cuspal slopes is visible from the lingual aspect.
•  The lingual root is also cone shape, smooth, and convex with no developmental depressions.
• The crown is smooth and spheroidal from the lingual aspect and the lingual cusp tip is pointed.

Mesial Aspect

• The buccal and lingual cusp tips are within the confines of the root trunk.
• The curvature of the cervical line is towards the crown but this curvature is less as compared to the curvature of the cervical line present on the mesial aspects of anterior teeth.
• The mesial marginal ridge of the maxillary first premolar has a developmental groove. This developmental groove serves as an identification of the mesial surface of the tooth. 
• A developmental depression is present on the mesial surface of the crown below the contact area and extends onto the root surface.
• The developmental depression on the mesial marginal ridge and the concavity present on the mesial surface of the tooth helps in the identification of the maxillary first premolar even when the tooth has a single root.

Distal Aspect

• The distal aspect of the crown of the maxillary first premolar is smooth with no developmental groove or depression.
• The curvature of the cervical line on the distal aspect of the crown is less as compared to the mesial aspect of the crown.
• The distal marginal ridge is smooth with no developmental depression.
• The maxillary first premolar has the largest root trunk.

Occlusal Aspect

• The occlusal surface of the maxillary first premolar is hexagonal.
• The crown is wide mesiodistally on the buccal aspect as compared to the lingual aspect where the mesiodistal dimensions are less.
• Overall the buccolingual dimension is more as compared to the mesiodistal dimension of the crown.
•  The central developmental groove divides the crown into buccal and lingual halves.
• There are some accessory or supplementary grooves that join the central developmental groove such as mesiobuccal developmental groove, distobuccal developmental groove, mesiolingual, and distolingual developmental grooves.
• Two triangular depressions are present adjacent to the mesial and the distal marginal ridges. These triangular depressions are named the mesial and the distal triangular fossa.  
• A ridge descent from the cusp tip towards the center of the occlusal surface and this ridge is named the buccal triangular ridge.
• Similar to the buccal triangular ridge a liner elevation arises from the lingual cusp tip and terminates in the center of the occlusal surface and this ridge is named the lingual triangular ridge. The lingual triangular ridge is less prominent as compared to the buccal triangular ridge.
• The buccal and the lingual triangular ridges form the transverse ridge.

Maxillary First Premolar Dental Morphology Video Lecture

Demonstration of Maxillary First Premolar Morphology on tooth models