Permanent mandibular first premolar

PERMANENT MANDIBULAR FIRST

PREMOLAR

Four in numberPost. To mand.

CaninesDev. From 4 lobesSharp buccal cusp

part that only occludes with maxillary teeth

Always Smaller of the 2

premolars

Buccal cusp is long and sharp and is the occluding cusp

Buccolingual measurement is similar to that of canine

Occlusal surface slopes sharply lingually in a cervical direction

Mesiobuccal cusp ridge is shorter than distobuccal cusp ridge

CHARACTERISTICS THAT RESEMBLE THOSE OF THE MANDIBULAR CANINE

Outline of crown and root from the buccal aspect resemble the second premolar

Contact areas mesially and distally are near the same levelCurvatures of the cervical line mesially and distally are

similarTooth has more than one cusp

CHARACTERISTICS THAT RESEMBLE THOSE OF THE SECOND MANDIBULAR

PREMOLAR

Nearly symmetrical bilaterallyWith pointed buccal cuspMesial cusp ridge is shorter than the distal cusp ridgeContact areas are broad from this aspect. Almost at the same

levelCrown is roughly trapezoidalTip of buccal cusp is pointedMesial outline straight or slightly concaveDistal outline of the crown is slightly concaveMore convex than max. first premolar

BUCCAL ASPECT

Crown tapers toward lingualLingual cusp always smallMost of the mesial and distal surface of both maybe seen

from the lingual aspectPointed lingual cusp tip ,align with the buccal triangular ridge

of the occlusal surfaceMesial and distal occlusal fossae are on each side of the

triangular ridgeRoot is narrower on the lingual side Characteristic- mesiolingual developmental grrove act as

demarcation line between mesiobuccal lobe and lingual lobe and extends into the mesial fossa of the occlusal surface

LINGUAL ASPECT

Crown outline is rhomboidalTip is nearly centered over the rootBuccal cusp centered over the rootAccentuated convexity and location of the crest of contour

are cha. Of all post. Teeth on the buccal surfaceSmooth except for the mesiolingual grooveRoot outline tapered from the cervix ending in a rel. pointed

apex in line with the tip of the buccal cusp.the lingual outline may be straight the buccal outline more curved

MESIAL ASPECT

Distal marginal ridge is higher above cervix no lingual slope of the mesial marginal ridge

No devt. Groove on the distal marginal ridgeDistal contact area is broader than mesial contact areaCurvature of cervical line is maybe the same as that found

mesiallySurface of root exhibits more convexity than was found

mesially .shallow devt. Depression is centered on the root but rarely it contain a deep devt. groove.

DISTAL ASPECT

Exhibit more variations in form occlusally than max. premolars

Outline form- diamond shapeSome has circular form similar to some mand. sec. premolars

OCCLUSAL ASPECT

Middle buccal lobe makes up the major bulk of the tooth crown

Buccal ridge is prominentMesiobuccal and distobuccal line angles are prominent

eventhough roundedMarginal ridges are well dev.Lingual cusp is smallOcclusal surface –heavy buccal triangular ridge and a small

lingual triangular ridgeOcclusal surface- mesial and distal fossae

CHARACTERISTICS COMMON TO ALL MANDIBULAR FIRST PREMOLARS

Most common type of mandibular first premolars shows a mesiolingual devt. Depression and groove

These constrict the mesial surface of the crown and create a smaller mesial contact area

The distal portion of the crown is described by a larger arc that creates a broader proximal surface than the canine