Maxillary Molars Lecture 8 PDF

MAXILLARY MOLARS LECTURE 8 YASAR MANSOUR AMSU  Introduction  Molar teeth are NOT preceded by primary teeth, accessional. In contrast, permanent incisors, canines, and premolars are succedaneous (successional teeth).  Molars are chewing teeth, they mainly cru...

MAXILLARY MOLARS LECTURE 8 YASAR MANSOUR AMSU  Introduction  Molar teeth are NOT preceded by primary teeth, accessional. In contrast, permanent incisors, canines, and premolars are succedaneous (successional teeth).  Molars are chewing teeth, they mainly crush and grind the food and they perform the major portion of the work in the mastication and comminution of food  The preservation of VERTICAL DIMENSION of the jaws also contribute to the overall FACIAL DIMENSIONs and thus the overall facial aesthetics.  They have the largest occlusal surfaces of any of the teeth and have from three to five major cusps.  upper permanent molars always have two buccal cusps  upper molars have three roots. Maxillary permanent molars  3 roots: MB, DB & 1 P. Palatal is largest  Crown: BL > MD dimension  3 major cusps  ML, MB & DB  Arranged in a tricuspate-triangular pattern  Lesser-sized DL cusp & sometimes missing  Oblique ridge: ML to DB cusp  B cusps are of unequal size  ML cusp is larger than DL  DL cusp reduces in size when going posteriorly. may be missing in 3rd molar  1st molar is the largest & shows the least morphological variation  Cusp of Carabelli  Roots become more D inclined and much closer when going posteriorly  MAXILLARY FIRST MOLAR Buccal Aspect  The mesial outline of the crown is a straight path downward and mesially, curving occlusally as it reaches the crest of contour of the mesial surface, which is the contact area.  This crest is approximately two thirds the distance from the cervical line to the tip of the mesiobuccal cusp.  The distal outline of the crown is convex; the distal surface is spheroidal. The crest of curvature on the distal side of the crown is located at a level approximately half the distance from the cervical line to the tip of cusp. The distal contact area is in the middle of the middle third Buccal Aspect  All three of the roots may be seen from the buccal aspect.  The mesiobuccal root curves distally, starting at the middle third. The distal root is straighter, curvature mesially at its middle third.  The point of bifurcation of the two buccal roots is located approximately 4 mm above the cervical line.  Deep developmental groove buccally on the root trunk which starts at the bifurcation and progresses downward, becoming shallower until it terminates in a shallow depression at the cervical line The mesio-buccal and disto-buccal cusps dominate the facial outline. MB & DB cusps are of almost equal height. Mesio-buccal is wider than disto-buccal Buccal developmental groove separates MB and DB cusps and terminates halfway the crown height in the BUCCAL PIT. D M Mesio-lingual cusp is the largest it can be seen from this aspect Disto-lingual cusp is also visible All three roots are visible. The bifurcation between the MB and DB roots starts at the end of the root trunk on the junction between Cervical & middle thirds. Mesio-Buccal root has a curvature and might have two canals. D M Lingual aspect Two cusps of unequal size. The cusps are separated by the lingual developmental groove which is continuous with the distolingual (or distal oblique) groove. The larger mesiolingual cusp often displays the Carabelli trait. It is a variable feature. It appears most often as a cusp of variable size, but is occasionally expressed merely as a pit. ML cusp Makes 3/5s of MD width of the crown Prominent & blunt DL cusp Rounded, shorter & narrower L groove Separates L cusps Terminates midway of L surface Only 2 lingual cusps are seen Buccal Cusps not seen Disto-lingual groove separates the 2 cups CUSP of CARABELLI is seen Roots The 3 roots are visible Proximal outline of B roots L root Tapered with blunt apex Shallow vertical depression from CL to 2/3s L root apex is in line with crown midline Mesial aspect Mesio-palatal cusp, mesial marginal ridge, and mesiobuccal cusp are seen. When present, Cusp of Carabelli is seen in this view. Maximum BP dimension at the middle of cervical cervical third. MP is higher than MB cusp B cervical 1/3 is strongly convex B outline continues in a straight line Palatal outline is uniformly convex. Palatal HOC is at the midpoint CL is slightly convex occlusally MESIAL ASPECT: Trapezoidal outline: with maximum bucco-palatal dimension is at the cervix of the crown Buccal Maximum curvature: middle of cervical 3rd then outline continues straight Palatal maximum curvature: middle of middle 3rd Palatal root is narrow & Banana-shaped it curves palatally then buccally at the apex Mesial contact area placed more to the buccal Mesial marginal ridge side is marked by several tubercles & supplementary grooves Cervical line is slightly curved towards the Occlusal (1 mm) Deep developmental groove on the root surface on B P mesio-buccal root Roots MB & P roots MB root is broad BL P root is narrow & Banana-shaped, curves L then B at the apex Both MB & P roots project beyond crown profile  Distal aspect  the two distal cusps are clearly seen.  the distal marginal ridge is somewhat shorter than the mesial one.  DB cusp is more prominent than DP  Only small portions of M cusps are visible  Distal MR is shorter and less prominent than M  Distal MR rarely has tubercles  B & P profiles are similar to those of M aspect  CL is nearly straight Distal Aspect Cervical line is straight Disto buccal root is shortest No Cusp of Carbelli or groove present Occlusal aspect The tooth outline is somewhat rhomboidal with four distinct cusps. The cusp order according to size is: mesiolingual, mesiobuccal, distobuccal, and distolingual. A frequent feature of maxillary molars is the Cusp of Carabelli located on the mesio paltal cusp. MB & DL angles are acute ML & DB angles are obtuse 1/3 of B surface & ½ of L are visible B outline: D part is more L than M part  Occlusal table 2 distinct components Trigon  MB, ML & DB cusps  Tricuspate triangle Talon  DL cusp & D MR  Located DL to the tricuspate triangle  Well-developed in 1st molar & undergoes reduction in size in 2nd & 3rd molars  Occlusal Aspect: Mesial and distal B triangular fossae. M triangular fossa M pit MESIAL MARGINAL RIDGE MB & ML is longer & more supplementary D prominent than the grooves DISTAL MARGINAL RIDGE M D triangular fossa (minor fossa) Distal pit Oblique ridge DB & DL supplementary grooves P  Occlusal View: B Two distinct components: Two Major Fossae: TRIGON Central fossa - Bears MB, ML & DB cusps Central pit - Tricuspate triangle Buccal groove TALON D Distal groove - Bears DL cusp & D MR Central groove - Located DL to the tricuspate M Distal fossa triangle D pit - Well-developed in 1st molar DL groove or distal & undergoes reduction in size oblique which in 2nd & 3rd molars continues as the L groove P Maxillary second molars Similar to maxillary first molar generally but differ in the followings: The disto-buccal cusp is not as well developed as in maxillary first molar. The disto palatal cusp is smaller. The cusp of Carabelli is absent from this tooth. The roots are of the same length as 1st molar and sometimes longer The roots are slightly less divergent The crown is shorter cervico-occlusally with amolst the same width bucco- palatally when compared to maxillary first molar  Buccal aspect  The crown is shorter occluso-cervically and narrower mesiodistally when compared to the first molar.  The distobuccal cusp is smaller than the mesiobuccal cusp.  The roots are more parallel; the apex of the D mesial root is on line with the with the buccal M developmental groove.  Mesial and distal roots tend to be about the same length.  Less prominent DB cusp & narrower MD  Distally inclined B roots Buccal View: The two buccal Similar to the first molar roots are nearly parallel and they are more straight compared to 1st molar. D M Buccal View: Both Mesial and Distal contact points tend to be centred bucco- palatally below the marginal ridges. → Molars become shorter  Lingual (Palatal) aspect  DP cusp is smaller in width and height  Palatal root is narrower MD & slightly D inclined D  No cusp of Carabelli  Mesial aspect  The crown is shorter than the first molar  The palatal & MB roots have less divergence.  The roots tend to remain within the crown profile.  Less numerous MR tubercles  MESIAL ASPECT: roots tend to remain within the crown profile. Buccal Maximum curvature: middle of cervical 3rd B Palatal maximum curvature: middle of P middle 3rd Distal aspect Smaller D cusps A greater portion of the occlusal aspect is visible  Occlusal aspect  The distolingual cusp is smaller on the second than on the first molar. When it is much reduced in size, the crown outline is described as 'heart-shaped.’  Cusp of Carabelli is usually absent.  The order of cusp size, largest to smallest, is the same as the first but is more exaggerated: mesiolingual, mesiobuccal, distobuccal, and distolingual. M  MB & DL angles are more acute  ML & DB angles are more obtuse  Talon is more reduced in size  More variable pit/groove pattern  More numerous supplementary groove  Crown is more constricted MD Occlusal View: narrower crown mesiodistally when compared to the first molar The disto-palatal cusp is smaller in the 2nd molar (smaller talon). Difference in the size of cusps is more exaggerated: Largest to smallest: mesiopalatal, mesiobuccal, distobuccal, and distopalatal. Permanent Maxillary Third Molars Maxillary and mandibular third molars show more developmental variation than any of the other permanent teeth. They are the teeth most often congenitally missing. Maxillary third molars Maxillary third molars vary considerably in size shape and position Some third molars resemble the adjacent second molar; others may have many cusps, small 'cusplets', and many grooves. The crown of this tooth is the smallest of the maxillary molars  Buccal aspect  The crown is usually shorter in both axial and mesiodistal dimensions.  Two buccal roots are present, but in most cases they are fused.  The mesiobuccal cusp is larger than the disto buccal cusp.  Crown is smallest in all dimensions  Roots are much short & commonly M fused  Roots shows a pronounced distal inclination  Two buccal roots are present, they Buccal ASPECT: are shorter but in commonly found The crown: fused. - Shorter and smaller in all Roots shows a dimensions. slight distal - The mesio-buccal cusp is inclination. larger than the disto-buccal cusp. D M Buccal ASPECT: Mesial contact point middle of crown is below the marginal ridges. Technically, the mesial surface is the only 'proximal' surface. The distal surface does not contact another tooth.  Lingual aspect  In most third molars, there is just one large lingual cusp (DL cusp is usually missing).  In some cases there is a poorly developed distolingual cusp and a lingual groove.  The lingual root is often fused to the two buccal roots. Mesial aspect The outline of the crown is rounded; Crown profile is irregular Fused roots  Distal aspect  DL cusp is usually absent  More of the occlusal surface is visible compared with 1st & 2nd Occlusal ASPECT: The outline of the occlusal surface can be described as triangular or 'heart-shaped.' Difference in the size of cusps is even more exaggerated: Largest to smallest: mesiopalatal, mesiobuccal and distobuccal distopalatal is of minimal size. Oblique ridge is barely visible Pit/groove pattern is variable Numerous supplementary grooves THANK YOU