Dental Anatomy Lec 2 Morphology of Anterior & Premolar PDF

Niagra Falls  Surface Anatomy of Permanent Teeth I, for incisor C, for canine I P, for premolar C P M I M, for molar M P  Anterior teeth They are divided into: Incisors And Can...

Niagra Falls  Surface Anatomy of Permanent Teeth I, for incisor C, for canine I P, for premolar C P M I M, for molar M P  Anterior teeth They are divided into: Incisors And Canines  Incisors There are four maxillary incisors and four mandibular incisors. Two central incisors contact with each other in the midline (mesially) and with the lateral incisors distally. Two lateral incisors contact with the central incisor mesially and with the canine distally. -Description of the crown - Chronology and function. -Aspects→ crown shape, surface, outlines, contact points, elevations and depressions -Description of the root: - Right and Left -Variation -.  Chronology Enamel organ appearance 5 m.i.u Beginning of calcification 3-4 m Crown completion 4-5 y Eruption 7-8 y Root completion 10-11 y - Central incisors are the largest and the widest of all the incisors. - - Abnormal space between the two central incisors is called midline diastema - Function : cutting and incision All teeth have 5 aspects 1 Facial Lingual Mesial Distal Incisal  Geometric outline of the crown Facial and lingual aspects have trapezoid , square or rectangular outline. Smallest uneven side cervically. Surface anatomy of the crown and root. Labial aspect Elevations: The labial surface is smooth and convex with maximum convexity at the cervical third (cervical ridge) Mamelons in newly erupted incisors Depressions: Shallow developmental grooves could be seen separating mamelons. Mesial, distal, cervical and incisal outlines of the crown Cervical outline (convex root wise) Mesial outline Distal outline (convex) (more convex) Sharp mesioincisal Rounded angle distoincisal angle Incisal (straight and may have mamelons) The contact areas present.in the incisal third. Mesially, near the mesioincisal angle. distally, near the junction of incisal and middle thirds. the contact areas mesially and distally are near to each other but still distal contact area present more cervically.  Contact Points:  Lingual aspect Elevations: Marginal ridges (mesial and distal) MMR longer than DMR cingulum Cingulum (cervically) towards the distal Incisal ridge Depressions: Lingual fossa Incisal ridge Marginal ridges - the lingual surface of all teeth is smaller in size than the labial due to the lingual convergence. It is not smooth as labial This convergence of the teeth is to accommodate the larger arch size facially than lingually  Proximal aspects Proximal (mesial and distal) aspects have triangular outline The crowns have smooth convex proximal surfaces. Base cervically. Apex incisally  Outlines Labial outline: convex with maximum convixity at the cervical third which represent ……. Lingual outline: convex incisally which represent……. Concave at the middle which represent… Convex cervically which represent……… Cervical outline: Curves incisally. the incisal ridge is in line with root apex but of 1 &2 inclined lingually. Why?  Distal aspect: is similar to the mesial aspect with few differences: - Cervical line is less convex - Smaller - Shorter due to roundation of the disto-incisal angle. - Distal surface is more convex incisocervically. - Thicker due to presence of disto-lingual slope on its labial surface.  Incisal aspect Outline and surface anatomy Upper central incisors: The outline is triangular in shape. The base is placed labially and apex lingually. The mesiodistal dimension (width) is greater than the labiolingual dimention (thickness). The crown is tapered lingually. The elevations and depressions in the crown lingually and labially appeared in this aspect.  Description of the root Single conical tapering and the apex of 1 is blunt. The mesial and distal outline of the root tapered to a pointed apex The apex directed distally except the 1 it’s centralized on the long axis so extraction could be done by rotation movement The root surface is smooth and convex  Root cross section is triangular with rounded angles, the base of triangle towards the labial and apex toward the lingual. the root is also converging lingually. Mesial arm a slightly longer than distal and the mesial surface may have shallow depression. Variation:. Variations include a short crown long crown. This tooth is rarely absent. The Hutchinson incisor shovel shaped incisor trait. Maxillary Lateral Incisor It is supplement the central incisor in the function so it resembles the central in all aspects but it is smaller and rounded  Differences between maxillary central and lateral incisors Central incisor Lateral incisor 1 Size greater Lesser 2 Mesio- incisal Sharp (90°) Round angle 3 Disto-incisal angle Round More rounded 4 Lingual fossa Smooth and shallow Small and deep 5 Lingual pit Absent May be present 6 Incisal ridge Straight Less straight 7 Incisal view Triangle with wide Round or oval with mesio-distal dimension equal mesiodistal and Labiolingual 8 Cingulum Tilted distally In center  You have to note that 2 has two rounded angles but the distal angle is more. D M  Lingual pit could be found in the 2 and should notice that all elevations are well developed than 1 Root appears longer  - Marginal ridges are prominent and terminate prominent cingulum. Cingulum is centered mesio-distally. Contact Points: mesial contact at the junction of the incisal third and the middle third. distal contact at the center of the middle third  Variation: peg-shaped. It is absent either singly or bilaterally in 1-2% of individuals The lingual pit Differences between maxillary and mandibular incisors Maxillary incisors Mandibular incisors 1 Crown Wider mesiodistally Wider faciolingually 2 Root (cross Triangular Oval section) 3 Marginal ridges Well developed Less developed 4 Cingulum Well developed Less developed 5 Lingual fossa Deep Shallow 6 Incisal edge (I. At one line with long Lingual to root axis edge) axis of the root 7 Attrition Incisal edge slope Incisal edge slope lingually labially 8 Incisal view Triangle Diamond 1 Labial Lingual Mesial Distal Incisal  The convexity of labial and lingual outlines are well developed in the upper teeth than lower teeth. Why? All elevations are more developed In upper teeth than in lower teeth. So the fossae appear shallower in the lower teeth The curvature of cervical lines in all teeth distally is less than mesially. The height of curvature decreased also from upper teeth to lower teeth  1 has two sharp angles and straight out lines mesially and distally. The smallest tooth.Smaller than the lateral. The crown having fan shape. symmetrical tooth The incisal edge is straight Sharp mesial and distal incisal angles  Variation: This tooth is consistent in development is rarely absent. Lower central incisors: The outline is diamond in shape. The labiolingual dimension Is greater than the mesiodistal dimension. 2 Labial Lingual Mesial Distal Incisal  2 Mandibular central Mandibular lateral 1 Overall size Smaller Larger 2 Crown Symmetrical Less symmetrical 3 Contact areas At the same level Distal C.A is more cervical 4 Marginal ridges Are at the same length Shorter distal M.R 5 Cingulum In center More distally 6 Incisal edge Straight and centered Inclined and twisted over the crown distally Lower lateral incisors: The outline is diamond in shape. The labiolingual dimension Is greater than the mesiodistal dimension. The incisal ridge of 2 tilted distally that allows the tooth to follow the dental arch curvature.  Outlines of the root Upper incisors: The outlines tapered from the cervical line to a blunt rounded apex Lower incisors: The outline are nearly straight from the cervical line to the middle third then tapered to a pointed apex Roots They have convex smooth surfaces except lower incisors have longitudinal developmental depression which is deeper distally than mesially.  Pulp cavity. Pulp cavity is formed of: Pulp chamber that is present in the crown. Its outline follows the outline of the crown. In young teeth, it has pulp horns related to each mamelon Root canal that present in the root and follow its outline. The number of root canals in incisors is only one. The root canal ends in an apical foramen  Accessory or lateral canals can be formed connecting the pulp to the periodontal ligament The pulp usually corresponds in morphology to the external shape of the tooth The pulp cavities become narrower with age Knowledge of the pulp anatomy is essential for the successful endodontic procedure. Maxillary incisors Mandibular incisors Identify the tooth, the aspects and tell FOUR differences between the lateral and central incisor. Answer A- Upper P. central incisor. B- Upper P.lateral incisor Lingual aspect 1- Size. 2- The elevations and depressions 3- The incisal angles. A B 4- The root. Identify the tooth, the aspect and the anatomical landmark. 2, lingual aspect, long mesial A marginal ridge, short distal marginal ridge. 1, mesial aspect, contact area, cervical line. A is for 2, incisal aspect, B distally tilted cingulum. B is for 1 , incisal aspect, lingual fossa. Can you tell *which tooth *which aspect *which surface anatomical landmark 1 , labial aspest, cervical ridge. 2, lingual aspect, lingual pit. 2 , labial aspect, cervical ridge. 2, lingual aspect, cingulum, M&D marginal ridges  To accomplish great things, we must not only act, but also dream; not only plan but also believe. (Anatole France)  Canine Function (mastication (tearing), esthetic). They are with a single cusp (cuspid) the longest tooth in the dental arch Number of lobes (four lobes 3 labially and 1 lingually). Corner stones of the dental arch. Canine eminence, which is considered important for normal facial appearance and expression. Darker and more yellow in the color than the incisor teeth. The maxillary deciduous canines are usually the last tooth to go.  Chronology Enamel organ appearance 6-8 m.i.u Beginning of calcification 4-5 m Crown completion 6-7y Eruption 9-10 L 11-12 U y Root completion 12-14 L14-15 U y Upper canine has 5 aspects: Labial Lingual Mesial Distal Incisal Lower canine has 5 aspects: Distal Labial Lingual Mesial Incisal  Geometric outline of the crown Facial and lingual aspects have trapezoid outline. Smallest uneven side cervically.  Facial and Lingual Outlines of 3 It’s Trapezoid and formed of Mesial outline:, convex till the contact area (at the junction of I 1/3 and M 1/3) then continues as concave till the cusp tip. Distal outline: concave till the contact area (at the middle third) then continues as convex till the cusp tip. Cervical outline: convex root wise.  Labial aspect Elevations: It’s convex with maximum convixity at the cervical ridge. There is prominent ridge runs from the tip of the cusp toward the cervical margin (Labial ridge). The middle lobe is well developed giving the cusp Depressions: Shallow longitudinal depressions lie mesial and distal to the labial ridge. The root shows convex smooth surface The mesial slope is shorter than the distal slope. The cusp tip pointed and on line with the long axis but slightly mesially deviated.  Facial and Lingual Outlines of 3 Mesial outline is straight. Mesial outline is convex. Both contact areas are more Contact areas are more incisally so the crown cervically. appeared longer and thinner than 3 Cusp tip is less pointed Cusp tip is more pointed 105º  Lingual aspect Elevations: Marginal ridges, cingulum, Prominent lingual ridge that extend from the cusp tip till the cingulum in 3 while in 3 it’s restricted to the incisal third. Depressions: Lingual fossa that is divided into two fossae in 3 but still one in 3. Note: The elevations of lower canine are not well cingulum developed as the upper The lingual surface is smaller in size than the labial surface due to the lingual convergence which accommodate ……….  Proximal aspects have triangular outline Apex of the triangle incisally. Note: the cusp tip of 3 centralized on the long The base axis or inclined labially. cervically. while the 3 cusp tip Apex of the centralized or inclined triangle lingually. incisally.  Proximal aspects Labial outline is convex with the crest of curvature at the cervical third represent…… Lingual outline is convex cervically represent... In the middle it’s straight due to presence of ridge …….. In the incisal third it’s convex again represent…… Cervical outline: curved incisally however, this curvature is less on the distal than the mesial. Notes: Lingual outline in the middle of 3 is concave rather than straight due to short lingual ridge.  Surface anatomy of the crown The crown surface is convex and smooth, except area cervical to the contact area shows flattening (mesial surface) or concavity (distal surface).  Incisal aspect. Outline and surface anatomy The thickness is greater than the width. The labial surface appeared convex and even more than the incisors The cingulum forms a short arc. The elevations and depressions in the labial and lingual surfaces appeared in this aspect Tip of the cusp is displaced labially and mesial  Outlines of the root the root is long, conical and slender ends in a bluntly pointed apex. The apical third may show mesial or more commonly distal curvature The mesial and distal The mesial and distal outline of the root tapered outline of the root to a pointed distally tapered to a sharply curved apex pointed distally curved apex  Outlines of the root Upper canine: The outlines tapered from the cervical line to a blunt pointed apex. It’s apical third may curved labially. Lower canine: The outline are nearly straight from the cervical line to the middle third then tapered to a more pointed apex The root surface is broad with longitudinal depression. The depression is shallower mesially than distally of same tooth and is shallower in upper canine than lower canine. the depression in lower canine may be so deep causing bifurcation in the root. The bifurcation may be apically or extend up to cervical third.  Variation: maxillary canine a cusp-like tubercle on the cingulum. Lingual pits the root is usually long or unusually short. Mandibular canine the root is bifurcated near its tip. The double root deep depressions in the root. Differences between maxillary and mandibular canine Maxillary canine Mandibular canine 1 Crown size Shorter, wider and thicker Longer, narrower and thinner 2 Dimension Labiolingual ˃ mesiodistal Greater labiolingual ˃ mesiodistal 3 Contact areas More cervically More incisally 4 Labial ridge Well developed Less developed 5 M, D outlines Bulge beyond the root Mesial outline is straight 6 Lingual surface Has well developed elevations Has less developed elevations 7 Lingual fossa Shallow More shallow 8 Cusp tip Located labial to root axis Centered or lingual to root axis 9 Cusp tip size Long and pointed Short and flatter 10 Cusp ridges Thick Thinner 10 Attrition At the mesial slope At the distal slope 11 Root Long Shorter by 1mm 12 Lingual aspect Converge More converge of root  Pulp cavity. Pulp cavity is formed of: Pulp chamber that present in the crown. Its outline follows the outline of the crown. In young teeth, it has pulp horns related to the cusp Root canal that present in the root and follow its outline. The number of root canals in canines is only one. Sometimes 3 has two root canals labially and lingually. The canals open in one apical foramen or separate foramina. Canines  Enumerate the names of the following elevations and depressions? Lingual ridge Cingulum. Distal marginal Mesial marginal ridge ridge. D.L.F M.L.F D.I.Ridge M.I.Ridge Discovery consists of seeing what every body has seen and thinking what nobody has thought. (Albert Szent- Gyorgyi)  Premolars There are four maxillary and four mandibular premolars. 4 & 4 contact 3 & 3 mesially and 5 & 5 distally 5 & 5 contact 4 &4 mesially and 6 &6 distally.  Bicuspids Premolars develop from 4 lobes. Mandibular 2 nd premolars develop from 5 lobes three buccal and two lingual  Maxillary first premolar It has 5 aspects: Buccal Lingual Mesial Distal occlusal  Chronology Enamel organ appearance 7 m.i.u Beginning of calcification 1.5-2y Crown completion 5-6y Eruption 10-11 y Root completion 12-13 y  Geometric outline of the crown Facial and lingual aspects have trapezoid or pentagonal out tine. The smallest uneven side cervically.  Mesial and distal Outlines Mesial and distal outlines are nearly concave Mesial and distal cusp slopes are also slightly concave D M Contact areas: Mesially at the M third while Distally it’s occlusally positioned which is an exception from other permanent posterior teeth. B cusp Cervical line: is convex root wise. pointed and long  Surface anatomy of the crown Elevations: The surface convex with maximum convexity at C 1/3 The middle lobe is prominent buccally forming BUCCAL ridge. Depressions: Shallow depressions were present mesial and distal to the B ridge Buccal cusp is pointed M slope longer than the D slope. Two slopes meet at right angle  Lingual outline and surface anatomy of the crown M and D outlines are convex The L cusp is shorter by 1 mm the B cusp The D slope of L cusp is longer M D than M slope. Two slopes meet at round angle Cervical line: is convex root wise. The surface is convex with maximum convexity at the M1/3. it is smooth and spheroidal and narrower than buccal.  Geometric outline of the proximal aspect Distal aspect Mesial aspect Trapezoid in shape Buccal cusp tip is located below the middle of the buccal root. Lingual cusp tip is in line with the lingual border of lingual root. Smallest uneven sides occlusaly Buccal and lingual outlines of proximal aspect Distal aspect Mesial aspect Buccal outline is convex with maximum convexity at junction of M and C 1/3 represent ……. Lingual outline is convex with maximum convexity at M1/3 Cervical line curves occlusally and decreased distally Distal aspect Mesial aspect Occlusal outline: B cusp is longer than L cusp by 1mm. Wide occlusal table. B cusp tip is below the center of B root. L cusp tip is on line with L border of lingual root MMR present at the junction of O 1/3 and M 1/3, while DMR more occlusal  Proximal surface anatomy Mesial aspect Distal aspect Contact area: At the middle third (OC dimension) Occlusally positioned and slightly buccal to midline (BL and more buccally. dimension) Mesial developmental groove is crossing MMR and located Smooth and convex lingual to the contact area. surface except for a Mesial Developmental depression in the small flat area crown and continue with that on the root cervical to contact (canine fossa). area.  Geometric outline of the occlusal aspect It’s hexagonal 2 equal buccal sides (MB, DB) D M M side shorter than D side. ML side shorter than DL side. Thickness is greater than width The crown is wider buccally than lingually. Why?  Surface anatomy of occlusal aspect: Elevations: B triangular ridge. L triangular ridge. M & D marginal ridges Depressions: Central developmental groove M and D triangular fossae. Two or four supplemental M developmental groove. grooves Mesial and distal developmental pit  Buccal surface anatomy of the root About 80% of upper premolars have two roots The M and D outline of the roots tapered to a pointed apex that curved distally.. The surface of the root is convex and smooth  lingual surface anatomy of the root The M and D outline of the roots tapered to a pointed apex that curved distally. If two roots, the lingual root appears shorter and narrower than the buccal root. The surface of the root is convex and smooth Mesial aspect Distal aspect In case of two roots (61- 80%). Root trunk about half the Root trunk is longer as root length. bifurcation is near apical 1/3 Surface is smooth and convex Surface is smooth and except deep developmental convex except shallow DD depression below bifurcation. on the root trunk  In case of one root. The B and L outlines tapered to a blunt apex on the center of the crown. The surface is smooth and convex except shallow depression in the center that is deeper mesially than distally.  Right and Left: The mesial developmental depression mesially displaced lingual cusp tip the mesial marginal ridge Variation: two roots; single root is found in about 20% of teeth. Three rooted premolars  Maxillary second premolar It has 5 aspects: Buccal Lingual Mesial Distal occlusal  Geometric outline of the crown Facial and lingual aspects have trapezoid out line. The smallest uneven side cervically.  Facial Outlines and surface anatomy of the crown 4 5 D M D M B cusp is long B cusp is short Longer M slope than D Shorter M slope than D Contact mesial A in the M1/3 Contact mesial A in O1/3 while while distally more occlusal. distally more cervically. Cervical line curved root wise. Cervical line less curved.  4 5 D M D M Prominent B ridge Less prominent B ridge Narrow cervical portion. Wider cervical portion. Short root. Longer root.  Lingual outline and surface anatomy of the crown 4 5 The L cusp is shorter The L and B cusps by 1 mm than the B are nearly of same cusp. height. 61% has 2 roots with Rare to has 2 roots L root is shorter than In case of two roots the B root and its apex is L root is shorter and its pointed. apex more blunt.  Mesial aspect 4 5 B cusp is longer than L The cusps are nearly at cusp by 1mm the same level. The occlusal table is The occlusal table is wide. narrow. The crown surface is smooth Mesial DG and canine and convex while root has fossa. shallow developmental depression.  Mesial aspect 4 5 MMR at the junction of MMR positioned more M1/3 &O1/3 occlusal. Contact area: At the middle third (OC At the occlusal third (OC dimension) and slightly dimension) and slightly buccal to midline (BL buccal to midline (BL dimension) dimension)  Distal aspect 4 5 DMR more occlusal than MMR DMR more cervical than MMR CA occlusally positioned and CA cervically positioned and more buccally than MCA. more buccally than MCA. Smooth and convex surface Smooth and convex surface. except for a small flat area cervical to contact area.  Distal aspect 4 5 Root trunk is long as One root and if 2 the the bifurcation is near bifurcation will be apical 1/3 more apically. Surface is smooth and Surface is smooth and convex except shallower convex except deeper DD on the root trunk than DD in the middle of the mesially. root than mesially.  Occlusal aspect 4 5 D M D M It’s hexagonal It’s oval B & L triangular ridges. B & L triangular ridges. M & D marginal ridges Thicker M & D MRs  4 5 Long Central DG Shorter Central DG. M developmental groove Not present. M and D fossae. M and D fossae. 2 or 4 supplemental grooves More supplemental grooves Differences between maxillary 1 st and 2 nd premolar Aspect Upper 1st premolar Upper 2nd premolar 1 Buccal Buccal ridge Prominent Less prominent 2 Buccal cusp Large and sharp Smaller and blunt 3 Mesial slope Longer than distal slope Shorter than the distal 4 Crown Tapers at cervix Broad at cervix 5 Lingual Lingual cusp Less than buccal by 1mm Two cusps are equal 6 Proximal Cusp tips Are closer together Spread apart 7 Mesial M. groove Present Absent and depression 8 Occlusal Outline Hexagonal and asymmetrical Oval, round and symmetrical 9 Lingual tapering Great Little 10 Central groove Long Short 11 M. M. groove Exit Absent 12 Supplemental Gs. Few More 13 Roots Number of roots 2 (1 buccal and 1 lingual) Single  Pulp cavity. MD section Root canals: BL section 2 root canals (B&L) but rare 3 canals L canal is larger &more accessible Narrow Wider Pulp chamber:  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 developmental groove  My greatest strength as consultant is to be ignorant and ask a few questions. (Peter Druker)  Mandibular first premolar It has 5 aspects: Buccal Lingual Mesial Distal occlusal Differences between maxillary and mandibular premolars Maxillary premolars Mandubular premolars 1 Size 1st ˃2nd 2nd ˃1st 2 Cusps Two cusps approximately 2 or 3 with smaller lingual with equal size Cusp 3 Proximal - Trapezoid -Rhomboid - Both cusps located over - lingual cusp extend past aspect the Root trunk. the lingual border of the root. 4 Dimension buccolingual dimension ˃ Buccolingual = mesiodistal mesiodistal 5 Roots May be two roots Single  Geometric outline of the crown Facial and lingual aspects have trapezoid out line. The smallest uneven side cervically.  Facial Outlines Crown Shape: short, symmetrical, pentagonal or trapezoid. B cusp pointed Mesial and distal outlines are concave and long Mesial and distal cusp slopes D M are also slightly concave Contact areas: Mesially at the junction of O and M thirds while Distally it’s cervically positioned. Cervical line: is convex root wise.  Surface anatomy of the crown Elevations: The surface convex with maximum convexity at C 1/3 The middle lobe is prominent buccally forming BUCCAL ridge. Depressions: Shallow depressions were present mesial and distal to the B ridge Sharp buccal cusp tip. Mesial slope is shorter than distal cusp ridge  Lingual outline and surface anatomy of the crown The crown tapers lingually M and D outlines are convex The L cusp is short and small reaching 2/3 the crown length and has a pointed tip. Cervical line: is convex root wise. M D Elevations: The lingual surface is convex with maximum convixty at M 1/3 Depessions: ML developmental groove at the ML line angle.  Geometric outline of the proximal aspect Distal aspect Mesial aspect Rhomboid in shape With narrow occlusal table Lingual inclination well prominent  Outlines of proximal aspect Distal aspect Mesial aspect Buccal outline is convex with maximum convexity at C 1/3 represent ……. Lingual outline is convex with maximum convexity at M1/3 Cervical line curves occlusally and decreased distally  Outlines of proximal aspect Distal aspect Mesial aspect Occlusal outline: the two cusps are not in same level (what’s the relation in between?) The B cusp centered over the root. This is due to the prominent lingual inclination. The L cusp tip in line with lingual border of the root.  Outlines of proximal aspect Distal aspect Mesial aspect DMR in 4 is straight MMR inclined (45º) and at right angle to from B to L surface \\ the axis of the tooth. to B cusp ridge. DMR is occlusal than MMR (unique characteristic of this tooth).  Proximal surface anatomy Distal aspect Mesial aspect M & D surfaces are smooth and convex except area cervical to contact area it’s concave. Contact area nearly at same level it’s broder, cervically ML developmental groove and lingually present at the junction of L positioned. and M surfaces. Geometric outline of the occlusal aspect It’s diamond or round D M Lingual convergence is sharp. Mesial outline is slightly curved. Distal outline is more convex.  Surface anatomy of occlusal aspect: Elevations: B triangular ridge. L triangular ridge. M & D marginal ridges Transverse ridge  Depressions: Central developmental groove M and D triangular or circular fossae with pits, 'snake eyes' when they are restored Mesiolingual developmental groove The distal developmental groove if present is crescent shaped  Outline and surface anatomy of the root single root. grooved and/or bifurcated roots Buccally “tapered to a pointed apex that curved distally. The surface of the root is convex and smooth Lingually: narrower and convex  Outline and surface anatomy of the root Distal aspect Mesial aspect B & L outlines are nearly straight cervically then taper to apically to a blunt apex The surface is more The surface is smooth convex and flat with deep developmental groove The root may divided apically B & L  Mandibular second premolar It has 5 aspects: Buccal Lingual Mesial Distal occlusal Mandibular 2ndpremolar resembles mandibular st 1 premolar although it is bigger in size. The tooth assumes two common forms. They are: The two cusp type 43%. is more rounded and having buccal cusp and lingual cusp Three cusp type. 54 % is more angular and has one buccal cusp and two lingual cusps  Geometric outline of the crown Facial and lingual aspects have somewhat trapezoid or square shape due to wide cervical third than 4.  Facial Outlines and surface anatomy 4 5 B cusp B cusp pointed and long short and less pointed Well prominent B ridge Less prominent B ridge Pointed apex Blunt apex  Lingual outline and surface anatomy 4 5 Two cusp type The L cusp is short and small L cusp is shorter and reaching 2/3 the crown length smaller than B cusp but and has a pointed tip. larger than of 4 The lingual surface is convex The surface convex with with maximum convixty at M 1/3 maximum convexity at ML developmental groove at O1/3. the ML line angle. No MLDG  Three cusp type: 5 ML cusp is longer and larger than M D DL cusp. They both shorter than B cusp and less pointed. The surface convex with maximum convixty at O1/3. The L developmental groove between the 2 cusps  Proximal outlines 4 5 Rhomboid in shape with Rhomboid in shape with narrow occlusal table. narrow occlusal table. Lingual inclination well Lingual inclination less prominent prominent  4 5 Maximum convexity at M1/3 Maximum convexity at O1/3 The L cusp is short and small L cusp is shorter and reaching 2/3 the crown length smaller than B cusp but larger than of 4 The B cusp centered over the B cusp tip on line with junction root. of B & M 1/3 of the root. The mesial MR is oplique The mesial and distal while distally is straight marginal ridges are straight Mesial aspect Distal aspect Three cusp type: ML cusp is longer and DL cusp is shorter and larger than DL cusp. smaller than ML cusp. Both lingual cusps are shorter than the buccal cusp and less pointed Surface anatomy is simillar to that of 4 Geometric outline of the occlusal aspect Two cusp type: 4 5 It’s diamond-shaped. The outline is oval Lingual convergence is sharp. Slight lingual convergence Three cusp type: The outline is square  Surface anatomy of occlusal aspect: 4 5 Elevations: B triangular ridge. L triangular ridge. Transverse ridge M & D marginal ridges  4 Depressions: 5 Central developmental groove Central developmental groove H or U shapped. M and D triangular fossae. M and D triangular fossae. Mesiolingual developmental groove  Three cusp type: Elevations: B triangular ridge. L triangular ridges (ML &DL). M & D marginal ridges Depressions: Central developmental groove Y shape M and D triangular fossae.  roots: single root that is larger than st that of the 1 premolar. Variation: There may be one or two lingual cusps. This tooth is sometimes missing; only the third molars and upper lateral incisors are missing more frequently than this tooth.  Differences between 1st and 2nd mandibular premolar st Lower 1 premolar nd Lower 2 premolar Crown Longer and more tapered to cervix Shorter and less tapered B. cusp Pointed Less pointed C. Areas At the same level Same level but, more occlusally M. slope Shorter than distal slope Both slopes are equal B. cusp tip Mesial to the center of the crown At the center B. ridge prominent Less prominent Width More converge Less converge L. cusp 1 very short, non functioning cusp 1 or 2 long, functioning cusps Crown Tilted severely to lingual Less tilted B. cusp tip At one line with root center Slightly buccal to the root apex M. lingual Present Absent, may has D.lingual D. groove A. groove M. ridges Tilted lingually Horizontal Outline Diamond, more converge lingually Round or square, less converge T. ridge Present between B and L cusps Found in 2 cusp type Central pit Absent Present S. grooves Few Numerous Pulp cavity.  I have never met a man who was not my superior in some particular. Ralph Waldo Emerson THANK YOU