Upper Permanent Premolars PDF

Upper permanent premolars Omyma Meabed  The maxillary premolars are four in nomber: two in the right maxilla and two in the left maxilla. They are posterior to the canines and immediately anterior to the molars in the permanent dentition The maxillary premolar crowns...

Upper permanent premolars Omyma Meabed  The maxillary premolars are four in nomber: two in the right maxilla and two in the left maxilla. They are posterior to the canines and immediately anterior to the molars in the permanent dentition The maxillary premolar crowns are shorter than those of the maxillary canines, and the roots are also shorter. The root lengths The maxillary equalfour: premolars number those two inof thethe molars. right maxilla and two in the left maxilla. They are posterior to the canines and immediately anterior to the molars. The premolars are so named because The crowns are theya little are longer anterior thanin those to the molars of the the permanent molars. dentition Because of the cusp development buccally and lingually, the marginal ridges are in a more horizontal plane and are considered part of the occlusal surface of the crown rather than part of the lingual surface, as in the case of incisors and canines. When premolars have two roots, one is placed buccally and one lingually  Maxillary First Premolar ❖ The maxillary first premolar has two cusps, a buccal and a lingual. Maxillary First Premolar ❖ The crown is shorter than that of the canine, The root is shorter. ❖ The mesial slope of the cusp is longer than the distal slope. D M  Buccal Aspect ❖Geometric outline: roughly trapezoidal ❖Out line form: o The mesial outline of the crown is slightly concave from the cervical line to the mesial contact area. The contact area: immediately occlusal to the middle point of crown The mesial slope of the buccal cusp is rather straight the distal slope is shorter and more curved. the tip of the buccal cusp distal to a line bisecting the buccal surface of the crown. o The distal outline of the crown below the cervical line is straighter than that of the mesial, although it may be somewhat concave also. The distal contact area is more occlusal ❖Cervical line curvature: convex toword root but, it exhibits D M little curvature  ❖ LANDMARKS ELEVATIONS: Buccal ridge: due to strong development of the middle buccal lobe Cervical ridge Cusp ridges Depressions: mesial and distal buccal developmental depressions ❖ Root form : The root tapers to pointed apex and curved distally In case of two roots, the buccal root hide the lingual root. Lingual aspect The mesial and distal outlines of the lingual portion of the crown are convex The crown tapers toward the lingual because the lingual cusp is narrower mesiodistally than the buccal cusp. The lingual cusp is smooth and spheroidal. The cusp tip is pointed, with mesial and distal slopes meeting at an angle of about 90 degrees. Because the lingual cusp is not as long as the buccal cusp, the tips of both cusps, with their mesial and distal slopes, may be seen from the lingual aspect. Root form: The lingual root is shorter and narrower than the buccal root. Mesial Aspect Geometric outline :roughly trapezoidal the longest of the uneven sides is toward the cervical portion and the shortest is toward the occlusal portion Out line form: buccal outline: convex with maximum convexity is located at the cervical third. the buccal cusp is directly below the center of the buccal root (when two roots are present). The lingual outline of the crown may be described as a smoothly curved line. The crest of this curvature is at the center of the middle third. The tip of the lingual cusp is on a line, in most cases, with the lingual border of the lingual root. The lingual cusp is always shorter than the buccal cusp, the average difference being about 1 mm. the mesial marginal ridge at about the level of the junction of the middle and occlusal thirds. LANDMARKS: mesial marginal developmental groove, canine fossa, developmental depression on the mesial surface of the root The root trunk is long on this tooth, making up about half of the root length. B L  Distal Aspect  The curvature of the cervical line is less on the distal than on the mesial surface, often showing a line straight across from buccal to lingual. The root trunk is flattened on the distal surface above the cervical line with no outstanding developmental signs. The bifurcation of the roots is abrupt near the apical third, with no developmental groove leading to it such as that found mesially. ▪ Narrower occlusal table Distal marginal ridge with out developmental groove Distal is smooth surface. ❖Occlusal Aspect ▪ Geometric out line: Hexagonal The six sides are made up of the mesiobuccal, mesiolingual, distolingual and distobuccal. This hexagonal figure, however, is not equilateral. The two buccal sides are nearly equal, the mesial side is shorter than the distal side, and the mesiolingual side is shorter than the distolingual side Thickness is greater than width Crown converge lingually Surface anatomy of occlusal aspect: Elevations: Triangular ridges of buccal & lingual cusps that extend from cusp tips to central developmental grooves M & D marginal ridges Buccal ridge Depressions: Long central developmental groove M and D triangular fossae with mesial and distal pits in the depth of these fossae Mesial marginal developmental groove that arises from mesial pit and crosses MMR Pulp cavities of premolars Mesiodistal section : the occlusal roof of the pulp chamber is curved beneath the cusp similar to the curvature of the occlusal surface. Buccolingual section : the pulp chamber often has the general outline of the tooth surface, sometimes including a constriction near to the cervix The pulp horns on the roof are visible beneath each cusp, and their relative lengths are similar to the relative heights of the cusps. Thus, the buccal horns are longer than the lingual horns Buccolingually larger than mesiodistally. Maxillary first premolars have two pulp horns, two roots (one buccal and one lingual) and two canals (one in each root) Even maxillary first premolars with a single root almost always have two canals. The average incidence of two canals, one in the buccal root and one in the lingual root, is 90%, although there is a small incidence of three roots Cervical cross section: kidney shape Maxillary second premolar OMYMA MEABED Buccal aspect  Buccal Aspect From the buccal aspect, it may be noticed that the buccal cusp of the second premolar is not as long as that of the first premolar and it appears less pointed  themesial slope of the buccal cusp ridge is usually shorter than the distal slope. The opposite is true of the first premolar.  The buccal ridge of the crown may not be as prominent as that of the first premolar D M Lingual aspect From the lingual aspect, little variation may be seen except that the lingual cusp is nearly equal to buccal cusp.  Mesial Aspect The cusps of the second premolar are shorter, with the buccal and lingual cusps more nearly the same length. Greater distance between Distal Aspect cusp tips widens the occlusal The distal root surface buccolingually. depression is deeper No developmental depression is evident on the than the mesial mesial surface of the crown depression on the as on the first premolar maxillary second A shallow developmental groove appears on the single premolar. tapered root. No deep developmental groove crossing the mesial marginal ridge is evident Occlusal Aspect From the occlusal aspect, some differences are to be noted between the two premolars. On the second premolar, the outline of the crown is more rounded or oval. The central developmental groove is shorter and more irregular there is a tendency toward multiple supplementary grooves radiating from the central groove. These supplementary Pulp cavities of upper second premolar Most maxillary second premolar have only one root and canal. Two roots are possible, although 2 canals within a single root may also be found. It has 2 pulp horns. When there is 2 root canals, they may have: 1.two separated foramina. 2. one apical foramen, join at the apical third. one apical foramen, join at the apex. ❑ The cervical cross section is usually oval.