The occlusal surface of the first maxillary premolar contains several grooves. The most central groove located in the middle of the occlusal surface is the central groove.

The central groove at both its ends contains two pits - the mesial and distal pits. These pits appear as sharp-pointed apexes of the distal fossa and mesial fossa that can also be found on either end of the central groove.

The buccal triangular ridge and lingual triangular ridge separate two triangular-shaped fossae located on either end of the central groove - the mesial triangular fossa and distal triangular fossa.

The mesial marginal ridge is crossed by the mesial marginal groove, which extends approximately 1 - 2 mm into the mesial surface from the occlusal surface.

When viewing the first maxillary premolar from the mesial or distal surfaces, two V-shaped grooves can be seen on either side of the occlusal surface. They are formed by either the distobuccal and distolingual grooves or mesiobuccal and mesiolingual grooves.

All these mentioned grooves go towards the cusps from both pits:

Mesiobuccal groove - goes from the mesial pit towards the buccal cusp;
Mesiolingual groove - passes from the mesial pit towards the lingual cusp;
Distobuccal groove - extends from the distal pit towards the buccal cusp;
Distolingual groove - goes from the distal pit towards the lingual cusp.

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First maxillary premolar (part 3)