Maxillary Molars Lecture 9 PDF

MAXILLARY PERMANENT MOLARS Dr. Aaron Anyetei-Anum 2nd November, 2020 CONTENTS General Introduction Maxillary First Molar Buccal Aspect, Palatal Aspect, Mesial Aspect, Distal Aspect Occlusal Aspect Roots Pulp Morphology Contents Maxillary Second Molar Buccal Aspect, Palatal Aspect, Mesial Aspect, Distal Aspect Occlusal Aspect Roots Pulp Morphology Contents Maxillary Third Molar : General overview of… Buccal Aspect, Palatal Aspect, Mesial Aspect, Distal Aspect Occlusal Aspect Roots Pulp Morphology GENERAL INTRODUCTION Maxillary molar teeth are large and present the largest occlusal surfaces They are the strongest teeth in the mouth by virtue of their crown bulk and root anchorage Their primary function is to grind or crush food The first permanent teeth to erupt are usually the first molars and they erupt distal to the deciduous second molars General Introduction The permanent molars do not have deciduous predecessors (accessional or nonsuccedaneous) They have more than one buccal cusp Generally have three roots They are roughly trapezoidal when viewed from the mesial or distal sides Viewed buccally or lingually, they are trapezoidal General Introduction Generally, the first molars are formed from five lobes but some second and third molars may have only four lobes The fifth lobe of the maxillary first molar develops into a supplementary cusp, which is completely afunctional and not usually present on either the second or third molars The first molars are the most highly developed and largest of the molars and are more likely to have minor and supplemmentary cusps, in addition to the three major cusps General Introduction Minor Cusps / Supplementary/Afunctional Cusps A minor cusp has smaller proportions and less development. It is less functional than the major cusps and is not always present on the second and third molars The second molars usually have no supplementary cusps The third molars may not develop minor cusps at all MAXILLARY PERMANENT FIRST MOLAR MAXILLARY FIRST MOLAR Evidence of Calcification : Birth Enamel Completed : 4 years Eruption : 6 – 7 years Root Completed : 9 – 10 years BUCCAL ASPECT There are two buccal cusps visible; mesiobuccal cusp distobuccal cusp The mesiobuccal cusp is wider than the distobuccal cusp, which is usually sharper and longer The buccal surface is convex in its cervical third but relatively flat in its middle and occlusal thirds Buccal View Buccal Aspect A buccal developmental groove (BDG) divides the two buccal cusps. This groove extends from the occlusal table, passes between the buccal cusps, runs parallel to the long axis of the tooth and ends about halfway up the buccal surface. At its terminal end, although not very deep, the BDG forms a buccal pit with two small grooves radiating from it Buccal Aspect The mesiobuccal cusp forms an obtuse angle where its mesial slope meets its distal slope at the cusp tip. The distobuccal cusp has a less obtuse angle at its cups tip The cervical line is irregular and curved, generally toward the occlusal side at the mesial and distal ends Buccal Aspect The mesial outline is straight from the cervical line to the mesial contact area. Below the contact area, the mesial outline becomes convex, curving distally until it reaches the mesiobuccal cusp tip The mesial height of curvature is just cervical to the junction of the middle and occlusal thirds Buccal Aspect Distally, the outline of the crown is convex and the contact area is in the center of the middle third All three roots can be seen. The buccal roots are divergent, with the palatal root in-between them PALATAL ASPECT There are two major cusps: (mesiopalatal cusp and distopalatal cusp) The two palatal cusps are disproportionate in size The mesiopalatal cusp occupies about three-fifths of the mesio- distal width of the palatal surface The distopalatal cusp is the smallest and the shortest of the functional cusps The two palatal cusps are not located directly lingual to the buccal cusps but are slightly distal to them. Palatal Aspect The mesiopalatal cusp is blunt The palatal surface is more or less uniformly rounded in all regions A palatal groove is present between the mesiopalatal and distopalatal cusps The palatal groove arises from the distal pit of the occlusal surface, runs between the palatal cusps and terminates approximately halfway up the palatal surface Palatal Aspect An accessory cusp exists in 60% of cases This is the tubercle of Carabelli. It is the shortest and smallest of all five cusps but it is afunctional A fifth-cusp developmental groove, called the mesiolingual groove, separates the tubercle of Carabelli from the mesiolingual cusp Palatal View Palatal Aspect The mesial outline from the palatal view resembles the mesial outline from the buccal view (Straight cervical third and convex occlusally) The distal outline is more convex because of the roundness of the distopalatal cusp All three roots can be seen. The palatal root is usually longer than the buccal roots, which are at the same length MESIAL ASPECT A clear profile of the tubercle of Carabelli can be seen The buccal crest of curvature is at the cervical third The palatal crest of curvature is at the center of the middle third of the crown The cervical line (CEJ) is slightly convex occlusally Mesial Aspect The bucco-lingual dimension is greater on the mesial side than on the distal side The mesial marginal ridge is more prominent than the distal marginal ridge DISTAL ASPECT The crown has the tendency to taper distally The cervical line is straighter and less curved A slight concavity is evident on the distal surface of the root trunk, from the cervical line to the distobuccal root The distal marginal ridge is shorter than the mesial marginal ridge More of the occlusal surface can be seen The distobuccal root is the narrowest of all OCCLUSAL ASPECT The occlusal view actually shows the first permanent molar as the largest of the maxillary molars in each quadrant There are four major cusps and one accessory cusplet The crown appears rhomboid in outline, with obtuse mesiopalatal and distobuccal line angles The longest diameter of the crown thus runs from the mesibuccal cusp to the distopalatal cusp Occlusal Aspect The crown is wider mesially than distally This molar tooth is the only tooth that is wider lingually than buccally An Oblique ridge is present across the occlusal table in a diagonal fashion The oblique ridge is a transverse ridge and joins the triangular ridges of the mesiopalatal and distobuccal cusps Occlusal Aspect The four major cusps are separated by an irregular H- shaped fissure pattern The occlusal table may be divided into two distinct components by the oblique ridge The two components are : TRIGON and TALON The trigon bears the mesiopalatal, mesiobuccal and distobuccal cusps The talon bears the distopalatal cusp Occlusal Aspect The trigon is characteristically triangular in shape, with the apex at the mesiopalatal cusp The mesial side of the trigon is formed by the mesial marginal ridge The distal side of the trigon is formed by the oblique ridge Two major fossae and two minor fossae are present Occlusal Aspect The major fossae are the: Central fossa(mesial to the oblique ridge) and the Distal fossa (distal to oblique ridge) The minor fossae are the : Mesial Triangular fossa (MTF)and the Distal triangular fossa (DTF). Both minor fossae are located on the inside of their respective marginal ridges Occlusal Aspect The Central Developmental Pit (CDP) lies in the central fossa The Buccal Developmental Groove (BDG) radiates from the CDP buccally between the two buccal cusps The Central Developmental Groove (CDG) lies in a mesial direction from the CDP and terminating at the Mesial Triangular Fossa (MTF) Occlusal Aspect From the Mesial Triangular Fossa (MTF), the Mesiobuccal Triangular Groove (MbTG) and the Mesiopalatal Triangular Groove (MpTG) appear as branches of the Central Developmental Groove (CDG) The Mesial Marginal Groove (MMG), a branch of the CDG, lies between the two triangular grooves (MbTG & MpTG) and may cross the mesial mariginal ridge of the crown Occlusal Aspect The Mesial pit is found in the Mesial Triangular Fossa The Distal pit is found in the Distal Triangular Fossa Sometimes another developmental groove radiates from the Central pit in a distal direction. If it crosses the Oblique ridge, joining the central and distal fossae, it is called the Transverse Groove of the Oblique Ridge (TGOR) or the Distal Oblique Groove or the Distal Part of the Central Developmental Groove (DPCDG) Occlusal Aspect The Distal Triangular fossa runs parallel with and distal to the Oblique ridge This fossa is long and narrow rather than circular The Distal Oblique Groove, as it terminates in the Distal Triangular Fossa gives off : Distobuccal Triangular Groove (DbTG) Distopalatal Triangular Groove (DpTG) and Distal Marginal Groove (DMG) Occlusal View Summary of Maxillary 1st Molar ROOTS of Maxillary First Molar There are three roots; two buccal roots (mesio-buccal and distobuccal) one palatal root, The three roots arise from a common root stalk The palatal root is the longest and strongest and is circular in cross-section The buccal roots are more slender and flattened mesio-distally Roots of Maxillary First Molar The mesiobuccal root is usually larger and wider than the distobuccal root At the root stalk, the palatal root is more commonly related to the distobuccal root than to the mesiobuccal root Roots of Maxillary 1st Molar PULP Morphology The pulp chamber of the maxillary first permanent molar is rhomboidal in shape The pulp chamber is wider bucco-palatally than mesio-distally Four pulp horns arise from the roof of the pulp chamber, one to each of the major cusps The pulp horn to the mesio-buccal cusp is the longest Pulp Chamber PULP Morphology The floor of the pulp chamber generally lies below the pulp cervical margin Three root canals present ( or four, in 60% of cases) The root canal of the mesio-buccal root leaves the pulp chamber in a mesial direction and is often significantly curved The fourth canal, when present, is located in the mesio-buccal root Pulp Canals PULP Morphology Thepalatal root canal is the widest and longest of the canals MAXILLARY PERMANENT SECOND MOLARS MAXILLARY 2ND MOLAR Evidence of Calcification : 3 years Enamel Completed : 7 – 8 years Eruption : 11 – 13 years Root Completed : 14 – 16 years BUCCAL ASPECT…2nd Molar The crown is shorter cervico-incisally and narrower mesiodistally than that of a maxillary first molar The distobuccal cusp is also smaller The buccal roots are about he same length as each other and are closer together The distobuccal root is straighter with no mesial curvature The mesiobuccal root has a greater curvature distally at its apical third Buccal View PALATAL ASPECT… 2nd Molar No cusplet (Tubercle of Carabelli) is seen The distopalatal cusp is smaller than that of the maxillary first molars Palatal View MESIAL ASPECT… 2nd Molar The crown is shorter than that of the first molar The buccolingual dimension is about the same as that of the first molar The roots are convergent DISTAL ASPECT…2nd Molar Smaller distobuccal cusp than the mesiobuccal cusp Summary of Surfaces OCCLUSAL ASPECT… 2nd Molar Occlusal outline is less rhomboidal (and more heart-shaped) than that of the first molar The distopalatal cusp is smaller in relation to the mesiopalatal cusp when comapared with the first molar Smaller mesiodistal diameter compared to the first molar Has more supplemental grooves and pits than the first molar Oblique ridge is less prominent Occlusal View ROOTS of Maxillary Second Molar There are three roots; palatal, mesiobuccal and distobuccal root The roots are more convergent than in the maxillary first molar The roots are commonly fused Summary of Maxillary 2nd Molar PULP Morphology… Maxillary Second Molar The pulp cavity / chamber of the maxillary second molar is similar to that of the maxillary first molar, but smaller with the rhomboidal shape more compressed The root canal orifices (from the pulp chamber) are closer to the pulpal floor, due to the roots being more convergent A second mesiobuccal canal is less common (40%) than the maxillary first molar Pulp… 2nd Molar MAXILLARY PERMANENT THIRD MOLARS MAXILLARY 3rd MOLARS Evidence of Calcification : 7 years Enamel Completed : 12 – 16 years Eruption : 17 – 22 years Root Competed : 18 – 25 years This tooth varies more than any other maxillary tooth in size, shape and relative position to other teeth. It is not well developed like the maxillary 2nd molar or can be congenitally missing MAXILLARY 3rd MOLARS The crown is shorter than that of a maxillary second molar The roots tend to fuse into one fused root The occlusal outline is heart shaped The distopalatal cusp is poorly developed or even absent Third molars have a tendency to become impacted in the alveolar bone, or obstructed by the second molars Occlusal View MAXILLARY 1st , 2nd & 3rd MOLARS The roots become shorter as the molar is more posterior The maxillary first molar has the longest root and the third molar has the shortest roots The roots become less divergent (more convergent or fused) as maxillary molar is more posterior The roots become more varied in size, shape and direction of curvature as the maxillary molar is more posterior In the fused-root form, only one large root with a single root canal may be evident Maxillary 1st, 2nd and 3rd Molars Maxillary 1st, 2nd and 3rd Molars Maxillary 1st, 2nd and 3rd Molars THANK YOU

Maxillary Molars Lecture 9 PDF

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