lecture 8 maxillary premolars.pdf

Lecture(8) Maxillary premolar Premolars are so named because they are placed between the anterior teeth and the molars (pre = before) * Premolars assist canines & molars in tearing and chewing food * Have two cusps (bicuspid) & two...

Lecture(8) Maxillary premolar Premolars are so named because they are placed between the anterior teeth and the molars (pre = before) * Premolars assist canines & molars in tearing and chewing food * Have two cusps (bicuspid) & two roots (buccal & lingual) * Eruption : at 10-11 years Buccal Aspect 1- Crown : Pentagonal shaped 2- Crown closely resembles to maxillary canine and second premolar 3- Mesial margin joins the Mesio-occlusal slope to create an obtuse Mesio-occlusal angle 4- Contour of the mesial outline is concave from the contact area to the cervical line 5- The mesial slope of the buccal cusp is longer than distal slope, which is the opposite of canine 6- Disto-occlusal angle is a little less prominent and the cervical concavity is not as deep 7- Occlusal margin of this tooth is, similar to the incisal margin of the maxillary canine 8- Buccal ridge 9- Mesio-buccal & disto-buccal developmental depressions on each side of buccal ridge Lingual Aspect 1- The crown tapers towards the lingual aspect 2- The lingual cusp is shorter than the buccal cusp 3- The lingual cusp is smooth from the cervical portion to the area near the cusp tip 4- The cusp tip is pointed with mesial and distal slope meeting at an angle of about 90 degrees 5- Small portion of the buccal cusp can be seen from this aspect Smoothly convex in all directions 6- There is no clearly defined lingual ridge 7- Mesial and distal outlines are normally somewhat convex & shorter than the same outlines of the buccal surface 8- Lingual cusp tip is not as sharply pointed as the buccal cusp tip 9- The Mesio-occlusal slope is shorter than the disto-occlusal slope Mesial Aspect 1- From the mesial and distal aspect both the buccal and lingual cusps are visible 2- A well developed mesial marginal ridge and a mesial marginal developmental groove is present 3- In the middle of the mesial surface is the mesial developmental depression which continues beyond the cervical line 4- Mesial concavity 5- Shape of the mesial surface is trapezoidal 6- Buccal outline is generally convex, with the height of contour in the cervical third 7- Lingually the outline takes the form of an even arc, with the height of contour in the middle third 8- Occlusal margin is irregularly concave and the majority of it is made up of the mesial marginal ridge. 9- A prominent mesial marginal groove is usually present indenting the occlusal margin almost two-thirds of the way from the buccal to the lingual outline. Distal Aspect 1- There is no developmental depression or groove on this aspect, instead it is convex at almost all points 2- The curvature of the cervical is less on this aspect 3- The contact area is near the junction of occlusal and middle third 4- distal is remarkably similar to the mesial surface, although it is slightly shorter occlusal-cervically. 5- Lingual margin is almost symmetrical & is quite convex, especially in middle third, where height of contour is located 6- Occlusally, distal is similar to mesial aspect, except that marginal ridge is located at a more cervical level 7- There is normally no marginal groove Occlusal Aspect Within cusp ridges and marginal ridges the following are present TBC & TLC : Tip of Buccal & Lingual cusp BTR & LTR : Buccal & Lingual Triangular ridge DBDG: disto-buccal developmental groove DTF & MTF : Mesial & Distal triangular fossa CG : Central groove 1-outline of crown can be described as hexagonal or six-sided and it is wider bucco-lingually than Mesio-distally 2- prominent buccal ridge is primary contributor to generally convex buccal outline 3- lingual margin is evenly convex, almost in a semicircle 4- Proximal margins are relatively straight & they converge toward lingual Root Most Maxillary first premolars have 2 roots, but one and three roots can also be seen Two roots : buccal and lingual Buccal portion of the root resembles canine The root when viewed from the proximal side shows a big trunk and bifurcation area from where the buccal and lingual root separate A developmental depression is seen on the mesial aspect of the trunk  Maxillary second premolar: It is similar to the first premolar but more rounded and has single longer root , it erupt at 10- 11 year. Buccal aspect: On the buccal aspect there is buccal cusp which is smaller and less pointed and the mesial slop of buccal cusp is shorter than distal slop. Lingual aspect: Similar to the first premolar except the lingual cusp is longer Mesial aspect : 1. We can see two cusps which are shorter and almost the same level. 2. No developmental depression found.  3. No developmental groove in mesial marginal ridge. Distal aspect: 1.It is more rounded out line oval shape. 2.Centeral developmental groove are short and irregular and there are multiple supplemental groove. Occlusal aspect: Similar to occlusal aspect of maxillary first premolar except : 1.The two cusp at the same level. 2.Smaller occlusal table and rounded. 3.Shorter central developmental groove.