Upper Premolars - Dental Medicine Lecture - PDF

Faculty Of Dental Medicine Oral Biology Department Lecture: (Upper premolars) Ass. Prof (Fatma Adel Saad) Surface Anatomy of Premolars  By Dr. Fatma Adel Saad Associate professor of Oral Biology  Premolars There are four maxillary and f...

Faculty Of Dental Medicine Oral Biology Department Lecture: (Upper premolars) Ass. Prof (Fatma Adel Saad) Surface Anatomy of Premolars  By Dr. Fatma Adel Saad Associate professor of Oral Biology  Premolars There are four maxillary and four mandibular premolars. Relation The upper 1st premolar is in mesial contact with the upper canine and in distal contact with upper 2nd premolar. 5 4 3 3 4 5  Function Mastication (tearing & grinding). Esthetic Speaking Growth of the jaws.  Chronology Chronology Enamel organ appearance. Upper first premolar 7 m.i.u Upper second premolar 8 m.i.u  Beginning Crown Eruption Root of calc. completed (years) completed (years) 4 10-11 1.5-2y 4 10-12 5 10-12 2-2.5y 5 11-12 3 4-5m 11 9 3  Number of lobes (four lobes, 3 buccally and 1 lingually). The middle buccal lobe of the premolars is well developed Occlusally Buccally cusp Buccal ridge. The lingual lobe developed into a cusp  Maxillary first premolar It has 5 aspects: Buccal Lingual Mesial Distal No. of roots 80% →2 roots occlusal 20% → 1 root  Geometric outline (Facial surface) Facial and lingual aspects have: Trapezoidal geometrical outline, the smallest uneven side cervically & the longest occlusally.  Outlines of Facial Surface Mesial outline, distal outlines → Concave (from cervical line to contact areas) Contact areas: MCA at the junction of occlusal & middle 1/3 DCA more occlusally positioned, (exception from other permanent teeth) Cervical line: Convex root wise. D M Occlusal outline: -M slope > D slope (exception from other permanent teeth). -Both slopes are nearly concave. -B cusp pointed & long  Surface anatomy of facial surface Elevations: The surface is convex with maximum convexity at C 1/3 represent cervical ridge Buccal ridge: from cusp tip to cervical ridge (due to overdevelopment of middle buccal lobe ) Depressions: MB & DB shallow depressions are present mesial and distal to the B ridge D M  ROOT M and D outlines of the buccal root taper from cervix to a pointed distally curved apex. The surface of the root is smooth & convex N.B: Maximum convexity = Height of contour= Crest of curvature.  Geometric outline (Lingual surface of the crown) Facial and lingual aspects have: Trapezoidal geometrical outline, the smallest uneven side cervically & the longest occlusally. -Lingual convergence; M & D surfaces converge lingually→ lingual surface is narrower than buccal surface → part of buccal surface is seen.  Lingual Surface outlines & surface anatomy Cervical line: Convex root wise. D M M and D outlines : Convex from cervical line to contact areas. Occlusal Outline: L cusp is smaller & shorter by 1 mm L cusp : D slope > M slope Surface anatomy: The surface is convex with maximum convexity at the M1/3  ROOT -80%, upper 1st premolar shows 2 roots 20%, upper 1st premolar shows 1 root. -If two roots, Buccal & palatal roots; the palatal root appears shorter & narrower than the buccal root. -The M and D outlines of the palatal root taper from cervix to a distally curved blunt apex -The surface of the root is convex and smooth  Geometric outline of the proximal aspects Distal aspect Mesial aspect Trapezoidal in shape Smallest uneven side occlusaly, longest side cervically  Outlines of proximal aspects of the crown Mesial aspect Distal aspect B L L B Buccal outline: convex with maximum convexity at C 1/3 represents cervical ridge. Lingual outline: convex with maximum convexity at M 1/3 Cervical line: M → (concave root wise) D → curvature decreased distally (nearly straight)  Mesial aspect Distal aspect B L L B Occlusal outline: -B cusp is longer than L cusp by 1mm. -Narrow occlusal table. -B cusp tip is on line with the center of B root (apex). -L cusp tip is on line with lingual border of L root MMR more cervical. DMR more occlusal  Surface anatomy of proximal surfaces Mesial aspect Distal aspect B L L B 1- Contact area: MCA: At junction of occlusal & middle 1/3 DCA: is occlusally & slightly buccal to midline. positioned (in occl 1/3) 2- Mesial Marginal developmental groove extends from M triangular fossa, crossing MMR to the mesial surface just lingual to contact area. Distal surface of the crown is smooth & convex except 3- Mesial Developmental depression (Canine fossa): formed by deep developmental for a small flat area cervical depression starts just cervical to M contact area & to contact area. continues up to join the deep developmental depression on the mesial root trunk (between root bifurcation)  Roots of Proximal aspects Mesial aspect Distal aspect Root trunk Undivided portion of the root B L L B In case of two roots (80%). Root trunk is longer as Root trunk is about the half bifurcation is in the apical length of the root. 1/3 M surface of the root trunk is D surface of root trunk is smooth & convex except for smooth & convex except deep DD on the mesial root for shallow DD on the distal trunk (canine fossa). root trunk In case of one root (20%) The B & L outlines taper to a blunt centralized apex. The root surface is smooth & convex except for a depression (deeper mesially than distally).  Occlusal aspect * Geometric outline: hexagonal B DB MB *Dimensions: BL (thickness) is greater than MD ( width). D. M *Lingual convergence: M & D surfaces converge lingually so the crown is narrower lingually than DL ML buccally. L  Surface anatomy of occlusal aspect B Elevations * Buccal cusp is longer than lingual cusp by 1mm D M *Buccal cusp with its triangular ridge & its M slope > D slope. *Lingual cusp with its triangular ridge & its D slope > M slope. L **Distal and mesial marginal ridges. - Depressions B -Central developmental groove. - Distal and mesial triangular fossae (with Distal and mesial pits). D M - The mesial marginal ridge is crossed by mesial developmental groove. L  The pulp cavity of 4 MD section Root canals: BL section D M L B Narrow Pulp chamber: Wide  Pulp cavity. Bucco-lingual section - Has wide pulp chamber with two pulp horns. - In case of one or two roots, there are two B L root canals taper from cervix to the apical foramen but rarely 3 canals. - The palatal root canal is wider and more accessible than the buccal one. Mesio-distal section - The pulp chamber is similar to the upper canine but narrower. D M -The root canal tapers from cervix to the apical foramen  Question Can you tell ; Which tooth, which aspect. 4 , occlusal aspect. Triangular ridge of B cusp. Triangular ridge of L cusp. M &D marginal ridges. Central developmental groove. M triangular fossa. D triangular fossa. Mesial marginal developmental groove. Differences between st 1 &2 nd Upper Premolars  Maxillary second premolar It has 5 aspects: Buccal Lingual Mesial Distal occlusal Relation The upper 2nd premolar is in mesial contact with the upper 1st premolar and in distal contact with the upper 1st molar. 6 4 6 5  Facial Surface 4 5 D M D M Contact area -Mesial: At the junction of Occ & M1/3 Mesial: In occl 1/3. -Distal: In occl 1/3 (More occlusal). Distal: At the junction of Occ & M1/3 (More cervical)  Outlines (Facial surface) 4 5 D M D M Occlusal outline -B cusp is long and pointed -B cusp is short and blunt -Buccal cusp: -Buccal cusp: M slope > D slope D slope > M slope  4 5 D M D M Surface anatomy Prominent B ridge Less prominent B ridge Root Short root. Longer root.  Lingual Surface 4 5 4 5 Occlusal outline L cusp is shorter by 1 mm than L & B cusps are nearly of the B cusp. same height. Roots 80% → 2 roots 15% → 2 roots ( Rare) L root is shorter than B In case of two roots, the L root. root is shorter than B root. Mesial Aspect  Mesial aspect (Outlines) 4 5 Occlusal outline L cusp is shorter than B cusp B & L cusps are nearly at by 1mm the same level. The occlusal table is narrow. The occlusal table is wide. MMR is more cervical MMR is more occlusal  Mesial aspect (Surface anatomy) 4 5 MCA: At the junction of MCA: in the occlusal third → occlusal & middle thirds → slightly buccal to midline. slightly buccal to midline. - Mesial marginal developmental groove. M surface is smooth & convex - Canine fossa.  Mesial aspect (Root) 4 5 80% 2 roots 85% 1 root 20% 1 root Roots 15% 2 roots Root trunk is about the half One root & if 2 roots length of the root (bifurcation in (bifurcation in the apical 1/3 ). the middle of the root). - M surface of the trunk is - D surface of the trunk is smooth & convex except for smooth & convex except for deep developmental depression shallow developmental on root trunk (canine fossa). depression on the root trunk. Distal Aspect  Distal aspect (Outlines) 4 5 Occlusal outline DMR more occlusal than MMR DMR more cervical than MMR  Distal aspect (surface anatomy) 4 5 DCA: DCA: In occl 1/3. At the junction of Occ & M1/3 more occlusal & more buccal more cervical & more buccal than MCA. than MCA.  Distal aspect (Root) 4 5 80% 2 roots 85% 1 root 20% 1 root Roots 15% 2 roots D root trunk is long & the One root & if 2 roots → D bifurcation in apical 1/3 D bifurcation is more apically. D surface of root trunk is D surface of root trunk is smooth & convex except for smooth & convex except shallower DD on D root for deeper DD on D root trunk than mesially. trunk than mesially.  Occlusal aspect 4 D D5 M M Geometric outline It’s hexagonal It’s oval Elevations Thin M& D Thicker M & D marginal ridges marginal ridges  4 5 4 5 D M Depressions Long Central DG. Shorter Central DG. Mesial marginal DG. Not found. M and D fossae. M and D fossae No supplemental grooves. Supplemental grooves could be found.  The pulp cavity of 5 MD section Root canals: BL section L B Narrow Wide Pulp chamber:  Pulp cavity Of 5 MD section Root canals BL section Dentin island Pulp chamber * In case of single root, there is mostly 1 root canal or may show a single broad canal divided into 2 canals in the middle of the root by Dentin island. Then, these canals rejoin again to open with an apical foramen. * If two roots, 2 canals one buccal and one palatal are seen.