permanent mandibular first premolar
TRANSCRIPT
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