ORAL Anatomy Lecture Finals PDF

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ORAL ANATOMY LECTURE COLLEGE OF DENTISTRY

PERMANENT MANDIBULAR MOLARS GENERAL DESCRIPTION

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Largest mandibular teeth because of their bulk and anchorage in the jaw Crown outline exhibit similarities from all aspects Shorter cervico-occlusally than teeth anterior to them Crown is wider mesiodistally than buccolingually Usually, the sum of the MD measurement of mandibular molars is equal or greater than combined MD measurement of all teeth anterior to first molar and up to the median line Resemble each other in functional form Perform the major work of the lower jaw in the mastication of food Has two roots (mesial and distal) 2nd and 3rd molars may show fusion of foots Has 5 well-developed cusps (two buccal, two lingual and one distal) Two well developed roots (mesial and distal) which are very broad buccolingually and widely separated at the apices The formation of roots and their positions in the mandible serve to brace the crown efficiently against the lines of force that may be brought to bear against it

MANDIBULAR FIRST MOLAR MANDIBULAR FIRST MOLAR

CROWN LENGTH

7.5mm

MESIODISTAL DIAMETER

11.0mm

BUCCOLINGUAL DIAMETER

10.5

ROOT LENGTH

14.0

ERUPTION AGE

6-7 years

ROOT COMPLETED

9-10 years

BUCCAL ASPECT

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UNI

30, 19

FDI

46, 36

PALMER

6, 6

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OCCLUSAL OUTLINE FOM

Quadrilateral, hexagonal or pentagonal

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# OF LOBES

5

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# OF ROOTS

2

# OF PULP HORNS

5

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Trapezoidal outline All 5 cusps are in view MBC-widest MD-cusp is flat DBC- almost as wide as MBC, with cusp ridge of somewhat greater curvature Distal Cusp- small and pointed, very round occlusally and sharper than the two buccal cusps Buccal cusps are typically flattened in mandibular molars while cusp ridges show less curvature Lingual cusps may be seen because they are higher than the buccal cusps Two Developmental Grooves: ➔ MBDG- acts as a line of demarcation between MB & DB lobes ➔ DBDG- acts as a line of demarcation between DB and Distal lobes CL is regular in outline, dipping toward root bifurcation Mesial outline of the crown in concave at cervical third up to irs junction with broad contact area Distal outline of the crown is straight above the CL to its junction with distal contact area Buccal Surface of the crown is smooth with developmental grooves between the cusps Developmental depression is noticeable at the ends of the grooves Roots are well formed and in constant development Mesial root is curved mesially from CL to the middle third then it curves distally to a tapered apex

1 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

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Distal outline of this root is concave from the bifurcation of the root trunk to the apex Distal root is less curved than the mesial root and may show curvature in mesial or distal direction Both roots are wider mesiodistally at the buccal area than they are lingually Developmental depressions are present on mesial and distal sides of both roots Point of bifurcation of the two roots is approximately 3 mm below the CL Deep developmental depression is evident buccally on the root trunk L-beam principle increases the anchorage of each root

LINGUAL ASPECT ● Three cusp are seen: ➔ MLC- is widest mesiodistally with tip of the cusp higher than DLC ➔ DLC- almost as wide as MLC ➔ Distal Cusp- is at a lower level than MLC ● LDG acts as a line of demarcation between the two lingual cusps (some mandibular first molars show no LDG, but show lingual depression on the cusp ridge) ● Root bifurcation starts at approximately 4mm below CL ● Bifurcation of root trunk is located almost in line with the LDG of the crown MESIAL ASPECT ● Rhomboidal crown outline ● Two cusps and one root are only seen ● BL measurement of the crown is greater in the mesial portion than distal portion ● BL measurement of the root is greater than the BL measurement of the distal root ● Entire crown has a lingual tilt in relation to the long axis (maxillary posterior teeth have the center of the occlusal surfaces between the cusps in line with the root axes) ● Buccal outline of the crown is convex immediately above CL ● BCR is clearly outlined before occlusal wearing has shortened the buccal cusps ● Lingual outline is straight in a lingual direction

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Mesial marginal ridge is confluent with the mesial marginal ridges of MB and ML cusps Mesial surface of the mesial root is convex at the buccal and lingual borders The root form appears to be two narrow roots fused together with thin hard tissue in between

DISTAL ASPECT ● More of the tooth is seen from the distal aspect because the crown is shorter distally then mesially ● Buccal surface shows more convergence distally than the lingual surface ● Distal root is narrower buccolingually than mesial root ● CL extends straight across buccolingually ● Apical third of the root is more rounded and it tapers to a sharper apex than on the mesial root ● Lingual border of the mesial root can be seen from the distal aspect OCCLUSAL ASPECT ● Occlusal outline: quadrilateral, hexagonal and pentagonal ● Crown measurement is greater MD than BL ● BL measurement of the crown is greater on the mesial than the distal side ● Five cusps from biggest to smallest: 1. MBC 2. MLC 3. DLC 4. DBC 5. Distal Cusp (functioning) ● One major fossa- central fossa ● Two minor fossae 1. Mesial Triangular Fossa- smaller than central fossa immediately distal to MMR 2. Distal Triangular Fossa- less distinct than mesial fossa immediately mesial to DMR ● Developmental grooves of the occlusal surface: ➔ CDG ➔ MBDG ➔ DBDG ➔ LG ➔ Supplemental Grooves 2 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

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Central Pit- junction of all developmental grooves Mesial Pit- union of buccal and lingual supplemental groove

MANDIBULAR SECOND MOLAR MANDIBULAR SECOND MOLAR UNI

31, 18

FDI

47, 37

PALMER

7, 7

OCCLUSAL OUTLINE FOM

Quadrilateral rectangular

# OF LOBES

4

# OF ROOTS

close together

# OF PULP HORNS

4

CROWN LENGTH

7.0mm

MESIODISTAL DIAMETER

10.5 mm

BUCCOLINGUAL DIAMETER

10.0 mm

ROOT LENGTH

13.0

ERUPTION AGE

11-13 years

ROOT COMPLETED

14-15 years

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Supplements first molar in function Has four well-developed cusps Some second molars are equal or greater in size than first molar No distal cusp DBC is larger than the DBC of first molar Roots are not as well formed as first molar

BUCCAL ASPECT ● Shorter cervico-occlusally and narrower mesiodistally than first molar ● Only one buccal developmental groove ● MBC and DBC are about equal in MD measurements ● CL points sharply toward root bifurcation

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Roots are shorter than first molar, usually closer together, may be fused for all or part of the length

LINGUAL ASPECT Differences between the first and second mandibular molars, to be noted on the lingual aspect: 1. The crown and root of mandibular second molar slightly converge lingually, but to a slight degree; little of mesial or distal surfaces may therefore be seen from this aspect. 2. The mesiodistal calibration at the cervix lingually is always greater accordingly than that of the first molar. 3. The curvatures mesially and distally on the crown that describe the contact areas are more noticeable from the lingual aspect. MESIAL ASPECT ● Buccal cervical ridge is less pronounced in most instances ● Occlusal surface may be more constricted BL ● Mesial root is somewhat pointed apically DISTAL ASPECT ● No distal cusp ● No distobuccal groove ● Contact area is placed equidistant from CL and marginal ridge OCCLUSAL ASPECT ● Occlusal outline: quadrilateral or rectangular ● No distal cusp ● No DBDG ● The BDG and the LDG meet the CDG at right angles of the central pit on the occlusal aspect, these grooves form a cross dividing the occlusal portion of the crown intro four nearly equal parts ● Cusps slopes are not smooth because they are not roughened by many supplemental grooves ● Anthropological studies developed by Gregory and Hellman ● 5-Y refers to molar with five cusps arranged so that when viewed from the lingual edge of the tooth, the fissure pattern resembles Y. 3 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

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4-Y refers to molar with 4 cusps Anthropology- study of humankind

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If the third molar is absent from one side of the mandible or maxilla, it will most like be absent from the other side

MANDIBULAR THIRD MOLAR MANDIBULAR SECOND MOLAR UNI

32, 17

FDI

48, 38

PALMER

8, 8

CA

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Mesial- middle Distal- middle third

OCCLUSAL OUTLINE FOM

Quadrilateral and ovoid

# OF LOBES

4

# OF ROOTS

most short, fused, inclined

# OF PULP HORNS

4

CROWN LENGTH

7.0mm

MESIODISTAL DIAMETER

10.0 mm

BUCCOLINGUAL DIAMETER

9.5 mm

ROOT LENGTH

11.0 mm

ERUPTION AGE

17-21 years

ROOT COMPLETED

18-25 years

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Supplements second molar in function Seldom well-developed Irregular development of the crown Undersized roots Occasionally the development is similar to second molar May exhibit 5 or more cusps Possible to find dwarfed mandibular third molar If crown is larger than normal, the roots are short and poorly developed (opposite of maxillary third molar, most of the anomalies are undersized) Usually impacted (lack of space accommodation is the chief cause)

BUCCAL ASPECT ● Shorter roots and poor in development ● Roots may be fused or bifurcated LINGUAL ASPECT ● If mandibular third molar is well-developed, it corresponds closely to mandibular second molar except the size of the root MESIAL ASPECT ● Mesial aspect resembles that of the second molar ● Mesial root shorter than second molar and tapering more from cervix to apex ● Apex of mesial root is more pointed compared to second molar DISTAL ASPECT ● Similar anatomical appearance like second molar except for size ● Third molar with oversized crown has a more spheroidal outline above the CL OCCLUSAL ASPECT ● If third molar is well-developed it is quite similar to second molar ● Has a tendency to exhibit a rounded occlusal outline

4 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

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PERMANENT MAXILLARY MOLARS

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GENERAL DESCRIPTION

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Largest and strongest maxillary teeth by virtue of both bulk and their anchorage in the jaws ● Crowns are shorter than premolars but bigger in dimensions in all aspects ● Roots are longer than premolars Functions: ● Major role in mastication of food (chewing and grinding to pulverize) ● Most important in maintaining the vertical dimension of face (preventing closing of the bite, a protruding chin, and a prematurely aged appearance) ● Maintaining the continuity within the dental arches thus keeping other teeth in proper alignment ● At least minor role in aesthetics. ➔ Keeping the cheeks normally full or supported ➔ Keeping the cheeks proper distance from the nose

MAXILLARY FIRST MOLAR

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MAXILLARY FIRST MOLAR UNI

3, 14

FDI

16, 26

PALMER

6, 6

CA

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Mesial- middle Distal- middle 3rd

OCCLUSAL OUTLINE FOM

Square to rhomboid

# OF LOBES

5

CROWN LENGTH ● Mesiodistal ● Buccolingual

7.5mm 10.0 mm 11.0 mm

ROOT LENGTH ● Buccal ● Lingual

12.0 mm 13.0 mm

ERUPTION AGE

6 years

ROOT COMPLETED

9-10 years

Largest tooth in the maxillary arch Usually appears in the oral cavity when the child is 6 years old Erupts posterior to second deciduous tooth therefore not succedaneous because it has no predecessor Because the development of the bone of the face is downward and forward sufficient space has been created, normally at the age of 6, for the accommodation of this tooth. May also be considered cornerstones of the dental arches (normal location is at the center of the fully developed adult jaw anteroposteriorly) Crown is wider buccolingually than mesiodistally Generous occlusal dimension because crown is broad both mesiodistally and buccolingually Rarely deviates from normal development 4 well-developed functioning cusps: ➔ MBC ➔ DBC ➔ MLC (largest cusp) ➔ DLC 1 supplemental cusp: ➔ cusp or tubercle of Carabelli ➔ Located lingual to the mesiolingual cusp ➔ Can grade down to series of groove, depressions or pits 3 well separated and well developed roots: ➔ MB- long, broad, buccolingually, greatest resistance to torsion ➔ DB- smallest, smoothly rounded ➔ L- longest, tapered and smoothly rounded

BUCCAL ASPECT

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Crown outline is trapezoidal with the longest uneven side toward the occlusal Four cusp are visible: 1. MBC- broader than DBC and its mesial slope meets its distal slope at an obtuse angle. 2. DBC- sharper than MBC and its mesial slope meets its distal slope at approximately right angle 5 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

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3. BDG- divides the buccal cusps (groove terminates at a point approximately half the distance from its origin occlusally to the CL) Distal crown outline is convex and spheroidal Distal contact area is middle of middle third Often from this aspect, a flattened area or a concave area is seen on the distal surface immediately above the DBC 3 roots are visible: ➔ Axes of the roots are inclined distally ➔ MBR curves distally starting at the middle 3rd ➔ DBR is more straight; tendency to curve mesially at its middle third ➔ LR longest ➔ Point of bifurcation of two buccal roots: 4mm above CL Apex of MBR is on a line with tip of MBC Molar roots originate as single root on the base of the crown called root trunk Roots are twice as long as the crown

LINGUAL ASPECT ● Crown outline is trapezoidal ● Distal outline of the crown becoming confluent with the curvature of the round distolingual cusp that creates a semicircular outline ● Lingual developmental groove is also confluent with the outline of DLC and terminates at the middle third of the root ● Lingual cusp are only visible from the lingual aspect ● MLC is the longest and largest cusp; an obtuse angle describes the junction of mesial and distal ● DLC is spheroidal; difficult to describe the angulation of mesial and distal slopes ● LDG terminates at the middle 3rd of the root; curves sharply to the distal ● Fifth cusp appears attached to mesiolingual of MLC: ➔ outlined occlusally by irregular groove ➔ If the cusp is well-developed, it appears sharper and less obtuse than MLC

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➔ The cusp ridge of fifth cusp is approximately 2mm cervical to MLC ridge Three roots are visible: 1. Lingual root- conical with bluntly rounded apex 2. Mesiobuccal root outline and part of the apex may be seen 3. Distal outline of distobuccal root is seen above its middle third

MESIAL ASPECT ● Increased BL dimension as well as cervical curvatures of the crown and distance between cusp tips in buccolingual direction ● Buccal outline makes a short arc within cervical third of crown outline become slightly convex toward MBC ● Lingual outline curves outward and lingually ● Fifth cusp is well-developed ● MMR irregular, confluent with mesiobuccal and mesiolingual cusp ridge ● CL is irregular curving occlusally ● CA approximately at the junction of middle and occlusal thirds of the crown; shallow concavity above the mesial surface ● MBR is broad and flattened; the width of this root near the crown from the buccal surface to the point of bifurcation on the root trunk is approx. ⅔ measurement buccolingually ● Level of root bifurcation is a little closer to the CL than is found between the roots buccally ● If fifth cusp is underdeveloped, the lingual outline continues from crest of curvature as smoothly curved arc to the tip of mesiolingual cusp ● MMR is confluent with mesiobuccal and mesiolingual cusp ● Mesiobuccal root is broad and flattened ● Mesiobuccal root hides the distobuccal root ● Lingual root (banana-shaped) is longer than mesial root ● The point of bifurcation between the two roots is about 3 mm closer to the CL

6 I DMD

ORAL ANATOMY LECTURE

COLLEGE OF DENTISTRY

DISTAL ASPECT ● Most of the buccal surface of the crown may be seen from this aspect ● CL is almost straight ● DMR dips sharply in cervical direction, exposing the triangular ridges ● Distal surface is convex, smoothly rounded ● DBR is narrower at its base than the MBR and LR ● No concavity between bifurcation of the roots and CL OCCLUSAL ASPECT ● Crown is wider mesially than distally and wider lingually than bucally ● Cusps (Largest to Smallest): ➔ MLC ➔ MBC ➔ DLC ➔ DBC ➔ 5th Cusp ● Occlusal table or occlusal surface ● Maxillary molar primary cusp triangle ● Oblique ridge ● Occlusal outline: rhomboidal ● Crown is wider on mesial aspect than distal; wider on lingual aspect than buccal ● DLC becomes progressively smaller on 2nd and 3rd molars often disappearing as major cusp ● Maxillary molar primary cusp triangle is the arrangement of 3 major cusp ● Maxillary molar primary cusp triangle is the arrangement of three major cusp ● The characteristic triangular figure of the cusp outlines, MMR and oblique ridge is a representative of all maxillary molars ● Maxillary first molar is within the confines of cusp ridges and marginal ridges so the morphological feature of its occlusal surface is called occlusal table ● Two major fossae: 1. Central fossa- roughly triangular and mesial to the oblique ridge 2. Distal fossa- roughly linear and distal to oblique ridge

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Two minor fossae 1. Mesial triangular fossa- immediately distal to MMR 2. Distal triangular fossa- immediately mesial to DMR Mesial marginal ridge and distal marginal ridge are irregular ridges confluent with the mesial and distal cusp ridges Central fossa- concave area bound by the distal slope of MBC, mesial slope of DBC, mesial slope of DLC, distal slope of MLC, crest of triangular ridges of the MBC, MLC and the crest of the oblique ridge Central developmental pit- located in the center of the occlusal surface that is circumscribed by cusp ridges and marginal ridges Central developmental groove- originates from the central pit that progresses in the mesial direction at an obtuse angle to the buccal groove Buccal developmental groove- radiates from the pit that progresses between the buccal surfaces of the crown Fifth cusp groove- any part of the developmental groove that outlines the fifth cusp Central pit- is located in the approximate center of the occlusal surface

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