Mandibular Molars PDF

+ MANDIBULAR PERMANENT MOLARS Dr. Aaron S. Anyetei-Anum + CONTENTS Introduction Mandibular First Molar Buccal, Lingual, Mesial, Distal and Occlusal Aspects Roots and Pulp Mandibular Second Molar Buccal, Lingual, Mesial, Distal and Occlusal Aspects...

+ MANDIBULAR PERMANENT MOLARS Dr. Aaron S. Anyetei-Anum + CONTENTS Introduction Mandibular First Molar Buccal, Lingual, Mesial, Distal and Occlusal Aspects Roots and Pulp Mandibular Second Molar Buccal, Lingual, Mesial, Distal and Occlusal Aspects Roots and Pulp Mandibular Third Molar Buccal, Lingual, Mesial, Distal and Occlusal Aspects Roots and Pulp + INTRODUCTION Thepermanent mandibular molars are the largest teeth in the mandibular arch They function as chewing or grinding tools There are three molars per dental quadrant Theyshow a progressive decrease in size, the more posterior the tooth is situated The crowns are shorter cervico-occlusally than that of the mandibular anterior teeth + Introduction The mandibular molars differ from the maxillary molars in the following respects: 1. Mandibular molars have two roots 2. They are derived from five cusps 3. Their crowns are oblong, being wider mesio-distally 4. Their fissure pattern is generally cross- shaped + Introduction 5. The lingual cusps are of more equal size 6.The tips of the buccal cusps are shifted lingually, showing more buccal view occlusally + MANDIBULAR PERMANENT FIRST MOLAR + Introduction Evidence of Calcification : Birth Enamel Completed :3 years Eruption : 6 years Root Completed : 9 – 10 years Usually the first permanent teeth to erupt + BUCCAL ASPECT Three cusps are seen from this view; Mesio-buccal, Disto-buccal and Distal cusps The distal cusp is the smallest. Mesiobuccal cusp is the widest of the buccal cusps There is a fissure separating the mesio-buccal and disto-buccal cusps (Mesio-buccal Developmental groove) The mesiobuccal groove arises from the central fossa on the occlusal surface and terminates in a buccal pit, halfway the occluso-gingival height + Buccal View + Buccal View + Buccal Aspect Themesiobuccal and distobuccal cusps are approximately equal in length The distal cusp is much more conical in shape and smaller than the other two cusps Thedistal cusp is separated from the distobuccal cusp by the Distobuccal Developmental groove Thebuccal surface appears markedly convex, especially at the cervical third Theconvexity is associated with the characteristic lingual inclination of the buccal cusps + Buccal Aspect Both the mesial and distal crown profiles converge towards the cervical third + LINGUAL ASPECT There are two lingual cusps ; mesiolingual and distolingual cusps Althoughthe lingual cusps are nearly equal in size, the mesiolingual cusp appears slightly larger The fissure between the two lingual cusps ( Lingual Developmental Groove) arises form the central pit on the occlusal surface, but does not extend a significant way down the lingual surface + Lingual View + Lingual Aspect Thelingual surface is convex in its occlusal and middle thirds but is flat or concave cervically Part of the occlusal and proximal sides may be seen from the lingual view, due to the lingual occlusal slope and taper Thetooth is wider on the buccal than on the lingual side + Lingual Aspect The mesial and distal profiles of the lingual aspect are both convex The crest of contour (contact area) is somewhat higher on the mesial than on the distal side due to the distal slope of the tooth Both contact areas are in the middle third of the tooth The bifurcation of the two roots begins with the Bifurcation groove on the root trunk, located directly in line with the lingual developmental groove + Lingual Devpt’l Groove and Root Bifurcation + Lingual Aspect Thelingual cervical surface is rather flat in comparison with the convex buccal cervical surface The cervical line is straight mesiodistally + MESIAL ASPECT Fromthis view, two cusps can be seen; Mesiolingual and Mesiobuccal TheMesiolingual cusp is the higher and more conical of the two The Mesial Marginal Ridge (MMR) joining the mesiobuccal and mesiolingual cusps is V-shaped The MMR is notched at its midpoint Themesial surface is flat or concave cervically and convex in its middle and occlusal thirds + Mesial View + Mesial Aspect Onlyone root, the mesial root can be seen from this view A Mesial Marginal Groove traverses the MMR There is a slight buccal bulge in the cervical third of the tooth known as the Buccocervical Ridge Thelingual height of contour is at the center of the middle third of the tooth + Mesial View + Mesial Aspect The cervical line tends to curve occlusally about 1mm in the center of the mesial surface. It is located higher on the lingual side than on the buccal side by almost 1mm + DISTAL ASPECT The Distal Marginal Ridge (DMR) joining the distal and distolingual cusps also appears V- shaped The distolingual cusp is the largest of the three distal cusps viewed from the distal surface The cervical third of the distal surface is relatively flat Thedistal surface is more convex than the mesial surface due to the distal cusp + Distal View + Distal Aspect The Distobuccal Groove separates the distobuccal and distal cusps TheDistal Marginal Ridge (DMR) is not as wide as the MMR The DMR is bisected by the Distal Marginal Groove (DMG) TheDMG is located lingual to the center of the tooth + Distal Aspect The crown tapers and converges distally, so that a greater amount of the occlusal table is seen from the distal view Thedistal contact area is located on the distal cusp and is centered over the distal root + OCCLUSAL ASPECT Thecrown outline form is somewhat pentagonal Thecrown is broader mesiodistally than buccolingually The occlusal table tapers lingually and distally Thereis a Mesiodistal Occlusal Fissure (MOF) which divides the occlusal surface into lingual and buccal parts The MOF arises from a deep central fossa + Pentagonal Outline + Occlusal View… Distal Convergence + Occlusal Aspect Five functional cusps can be seen The buccal side of the occlusal table has three distinct cusps ; Mesiobuccal, Distobuccal and Distal Cusps Eachcusp is separated by a groove, which joins the Mesiodistal Occlusal Fissure On the lingual side are two cusps; mesiolingual and distolingual Thefissure separating the two lingual cusps joins the MOF in the region of the central fossa + Five functional cusps + Occlusal Aspect Thelingual cusps are higher and more pointed than the buccal cusps Themesiobuccal cusp is wider than either of the lingual cusps, which are about the same size Thetips of the buccal cusps are displaced lingually, are rounded and are lower in height than the lingual cusps Thesmallest cusp is the Distal cusp, which is displaced slightly to the buccal surface + Occlusal Aspect All the developmental grooves converge at the central pit in the central fossa The central fossa is a concave area bordered by ; the distal slope of the mesiobuccal cusp, the mesial and distal slopes of the distobuccal cusp, the mesial slope of the distal cusp, the distal slope of the mesiolingual cusp and the mesial slope of the distolingual cusp + Occlusal View… Central Fossa + Occlusal Aspect Two other fossae are present: the Mesial Triangular Fossa and the Distal Triangular Fossa Thetwo buccal grooves and the lingual groove form a Y-shaped groove pattern + Occlusal View + Occlusal View + Occlusal View + Occlusal Aspect In90% of cases, the mesiolingual cusp is joined to the distobuccal cusp across the floor of the central fossa. This feature and the five-cusped pattern is termed the DRYOPITHECUS Pattern Thisprimitive pattern is characteristic of all the lower molars of the anthropoid apes and their early ancestors, the Dryopithecines. + Occlusal Aspect TheDryopithecus Pattern is sometimes referred to as a Y5 Pattern due to the resulting Y-shaped pattern and the five cusps Inthe 10% of cases where the mesiobuccal and distolingual cusps meet, a more cruciate system of fissure is produced; this is sometimes referred to as a +5 Pattern + ROOTS and PULP MORPHOLOGY Thereare two roots; mesial and distal, both of which arise from a common root stalk or trunk The two roots are markedly flattened mesiodistally The mesial root is usually deeply grooved Both roots curve distally + Pulp Morphology The pulp cavity of the mandibular molars consists of a pulp chamber and three pulp canals generally. The mesial root houses two pulp canals; a mesiobuccal and mesiolingual canal, and the distal root houses one larger pulp canal Thereis a pulp horn under each cusp (i.e. five pulp horns) Occasionally there are four root/ pulp canals. Here, the distal root tends to house two canals; a distobuccal and distolingual canal + Pulp Morphology + Pulp Morphology THREE PULP CANALS FOUR PULP CANALS + Roots + Mandibular 1st Molar + Pulp Morphology  MANDIBULAR + PERMANENT SECOND MOLARS + Mandibular 2nd Molar + INTRODUCTION Evidence of Calcification : 2 – 3 years Enamel Completed : 7 - 8 years Eruption : 11 – 13 years Root Completed : 14 – 15 years + BUCCAL ASPECT The crown appears smaller than that of the mandibular first molar Only two buccal cusps exist, which are equal in their mesiodistal dimensions A fissure extends between the buccal cusps from the occlusal surface and terminates approximately halfway up the buccal surface The buccal surface is highly convex, like the mandibular first molar + LINGUAL ASPECT Fromthis view the buccal profiles and proximal surfaces are not visible The crown has a less lingual convergence than the mandibular first molar due the absence of a distal cusp The crown is noticeable shorter than the mandibular first molar + MESIAL ASPECT Resembles the mesial view of the mandibular first molar The mesial marginal ridge does not converge Theyare not as markedly notched in the midline The contact area is at a lower level compared to the mandibular first molar + Mesial View + DISTAL ASPECT Because there is no distal cusp, the distal aspect resembles the mesial aspect There is no distal cusp The contact area is located at a lower level compared to the mandibular first molar Thecontact area is centered both buccolingually and cervico-occlusally + Distal View + OCCLUSAL VIEW Occlusal outline is more rectangular there is usually no fifth (distal) cusp All four cusps are nearly equal in size + Occlusal View + ROOTS and PULP MORPHOLOGY Theroots are shorter, more convergent and more distally inclined than the mandibular first molar roots Four pulp horns are present under the four cusps Thetooth has three pulp canal within the two roots; mesial root houses two root canals and the distal root has one canal Occasionally, the mesial root may have two root canals, one within each tooth + Manibular 2nd Molar + Pulp Morphology  MANDIBULAR + PERMANENT THIRD MOLAR + INTRODUCTION Has a variable / unpredictable morphology Thesmallest of the mandibular molars but can be as large as the first molar The crown has four or five cusps Inshape, it is normally a rounded rectangle or circular The two mesial cusps are larger than the two distal cusps + Introduction Evidence of Calcification : 8 –10 years Enamel Completed : 12 –16 years Eruption : 17 – 21 years Root Completed : 18 – 25 years The occlusal surface has a very wrinkled appearance, with irregular groove pattern and numerous pits + Occlusal View + Mandibular Third Molars The roots of the third molar are usually shorter than those of the second molars and are inclined acutely to the distal side. Theroots are also very close together and often fused + Comparison + Summary + Summary + Summary + THANK YOU ALL