Dental Anatomy: Mandibular Second Premolar PDF

2023\2024 Dental Anatomy Dr.Faten S.M MANDIBULAR SECOND PREMOLAR\ Lec.9 Eruption 11 – 12 years Root completed 13– 14 years This tooth resembles the mandibular first premolar from the buccal aspect only. It has a single root which is large...

2023\2024 Dental Anatomy Dr.Faten S.M MANDIBULAR SECOND PREMOLAR\ Lec.9 Eruption 11 – 12 years Root completed 13– 14 years This tooth resembles the mandibular first premolar from the buccal aspect only. It has a single root which is larger and longer than that of mandibular first premolar. This tooth coming in two type , the three-cusp type, in which there are one buccal and two lingual cusps, its most often seen, and it appears more angular from the occlusal aspect. The second is the two-cusp type, in which there are one buccal and one lingual cusps, it appears more rounded from the occlusal aspect. Buccal Aspect: The buccal aspect of permanent mandibular second premolar is same as that of permanent mandibular first premolar but there are some differences as flow: 1- The buccal cusp is shorter than in permanent mandibular first premolar 2- The contact areas are broader and appear to be higher because of the short buccal cusp. 3- The mesio-buccal and disto-buccal cusp ridges (cusp slopes) are less steep, more rounded. 4- The crown is shorter overall and is wider in the cervical third than the mandibular first premolar. 5- The buccul ridge is not well developed. 7- The cervical line is less curved than it does on mandibular first premolars. 8- the root is broader mesiodistally than lower four. 9- the root apex is more blunt. 1 2023\2024 Dental Anatomy Dr.Faten S.M Lingual Aspect: 1- The lingual cusp or cusps are well developed and longer than that of lower four so that less of the occlusal surface can be seen from this aspect. 2- In the three- cusp type there are two lingual cusp, the mesiolingual one which are the larger and the longer one of the both and the distolingual one and there is a shorter groove extended occlusolingually between them called lingual groove. The two cusps are not as long as the buccal cusp and are less pointed. 3- In the two-cusp type there is one lingual cusp which is smaller than the buccal cusp with no developmental groove. 4- The lingual portion of the root is smoothly convex for most of its length. 2 2023\2024 Dental Anatomy Dr.Faten S.M Mesial Aspect: Lower mandibular second premolar differs from the mandibular First premolar from this aspect as follows:- 1- The crown and root are wider buccolingually. 2- The buccal cusp is shorter than lower four. 3- The lingual cusp is more developed. 4- The root is longer. 5- The root apex is more blunt. Distal Aspect:- This aspect is similar to the mesial aspect except that most of the occlusal surface can be seen from this aspect since the distal marginal ridge is at lower level than the mesial marginal ridge. The disto-lingual cusp is usually smaller and shorter than the mesio-lingual cusp (Three-cusp type), so both lingual cusps are seen from this aspect. 3 2023\2024 Dental Anatomy Dr.Faten S.M Occlusal Aspect: a - Three-cusp type:- 1-the occlusal out line is square in shape. 2-the three cusps are well developed, the buccal cusp is the larger then followed by the mesiolingual cusp and the distolingual cusp which is the smallest. Each cusp has well formed triangular ridge, the three triangular ridges converge toward a central fossa, which has central pit 3- There are three developmental grooves radiate from the central pit and form a Y on the occlusal surface and separate the triangular ridges: the mesial, distal and lingual developmental grooves. 4-The long mesial groove extends in a mesio-buccal direction and ends in the mesial triangular fossa just distal to the mesial marginal ridge. 5-The short distal groove extends in a disto-buccal direction and ends in the distal triangular fossa. 6- The lingual groove extends lingually between the two lingual cusps to the lingual surface for a short distance. b-Two-cusp type:- 1- it is rounded in shape lingual to the buccal cusp ridges 2- the mesiolingual and the distolingual line angles are rounded, 3- there is no central pit, it has the central developmental groove which is end in the center of the mesial and the distal fossa. 4 2023\2024 Dental Anatomy Dr.Faten S.M 4-The mesial and distal fossae are roughly circular depressions having supplemental grooves radiating from the central groove and it ends at the marginal ridges. Pulp cavity of permenant mandibular second premolar A. Buccolingual Section 1-The mandibular second premolar has a larger crown and root than the first premolar. The dimensions of the pulp cavities are increased, but the extremely wide dimensions are confined to the crown and the upper portion of the root canal. 2- the pulp horns in the second premolar tend to be more prominent and the lingual pulp horn is present more often. 3- The pulp chambers are usually gently taper into the pulp canal 4- The apical foramen may appear to exit at the apex B. Mesiodistal Section 1-The mandibular second premolar is very similar to the mandibular first premolar, except that the overall dimensions of the second premolar are slightly larger 2-The pulp horns are prominent, and the pulp chamber and root canal gently taper toward the apex. 3-The apical foramen appears to exit at the tip of the root in the majority of cases. 5 2023\2024 Dental Anatomy Dr.Faten S.M C. Cervical Cross Section The outline form of the root is rectangular oval or triangular. A=Buccolingual section, B=Mesiodistal section C=Cervical cross section Anomalous mandibular premolars - The mandibular first premolar exhibited three distinct, separate roots. –Mandibular second premolar exhibited a C-shaped root canal system. -Macrodontia of mandibular second premolar, - Dens evaginatus ( is defined as an outgrowth on the crown of a tooth). Clinically, it appears as a small tubercle on the occlusal surface of a tooth. It may contain pulp if tubercle is large. Proximal view of a normal mandibular right second premolar (left) and a macrodontia mandibular right second premolar Dens evaginatus mand. Sec.premolar C-shape root 6