permanent maxillary first molar .pdf

Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Permanent maxillary molars the largest and strongest maxillary teeth. They have three roots: two buccal and one lingual...

Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Permanent maxillary molars the largest and strongest maxillary teeth. They have three roots: two buccal and one lingual (palatal). They are not successor teeth as they erupt behind the deciduous molars. Their main function is grinding the food and supporting the muscles of mastication and vertical dimension. Maxillary First Molar It is the largest tooth in the maxillary arch. Principal Identifying Features 1. Rhomboidal occlusal outline. 2. The presence of a fifth cusp named (the cusp of Carabelli)-a non-functional cusp- on the lingual surface of the mesio-lingual cusp. 3. The presence of an oblique ridge extending from the mesiolingual cusp to the disto-buccal cusp. 4. The presence of three well-separated and well-developed roots: two buccal and one lingual The lingual root is the longest. 5- eruption time at 6yrs and first evidence of calcification at birth 1 Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Buccal Aspect The crown is roughly trapezoidal and the cervical line shows very little convexity, which is directed toward the root. The mesial outline of the crown is straight until reaches the contact area, which is located at the junction between the occlusal and middle thirdsthen be convex to the tip of the cusp. The distal outline of the crown is convex, with the contact area located at the center of the middle third. The mesio-buccal cusp is broader than the disto-buccal cusp, and its mesial and distal slopes meet at an obtuse angle, while the mesial and distal slopes of the disto- buccal cusp meet at a right angle (which is sharper).from buccal aspect can be see 4 cusp ( 2 buccal cusp and 2 lingual cusps parts from them ) The buccal developmental groove divides the two buccal cusps in equal distance and it terminates apically. The three roots are visible and inclined distally, with the lingual root is the longest. 2 Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Lingual Aspect 1. Semicircular distal outline from cervical to the occlusal tip of the cusp while mesial outline the same as in buccal aspect that discus before that 2. The lingual cusps only can be seen. 3. the mesio-lingual cusp is the largest cusp and accounts for 3/5 of the mesio- distal width of the crown with obtuse angle , while the disto-lingual cusp accounts for 2/5 of the mesio-distal dimension and no angle can be seen at the tip because its small spheroidal smooth cusp. 4. The lingual developmental groove starts approximately at the center mesio- distally and curves sharply distally, then continues on the occlusal surface. 5. The fifth cusp (the cusp of Carrabelli) is 1.5 mm cervical to the mesio-lingual cusp tip, and an irregular developmental groove separates this cusp from the mesio-lingual cusp. 6. There are three roots visible, with the lingual root making most of the aspect. 3 Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Mesial Aspect 1. The buccal outline has a crest of curvature at junction of the cervical third and middle, the buccal out line convex outline to crest of curvature then become slightly concave to the junction of middle and occlusal third beyond this point again become convex in shape to the tip of the cusp. 2. The lingual outline has a crest of curvature within the middle third, and it shows a convex pattern until it reaches the tip of the cusp. 3. The mesial marginal ridge is located at a level 1/5 the height of the crown. 4. The cervical line curves occlusally about 1 mm. 5. The mesial contact area is buccal to the bucco-lingual center of the crown at the junction of occlusal and middle third. 6. The lingual and mesio-buccal roots can be seen. The lingual root with banana shape and out of crown border from this aspect 4 Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 Distal Aspect The general outline is similar to that of the mesial aspect except in the following ; 1- the bucco-lingual measurement is more mesially than distally. 2. The distal marginal ridge is located more cervically, so we can see part of the occlusal surface. 3. The curvature of the cervical line is straight zero. 4. All the three roots are visible, and the distobuccal root is the smallest one. 5- distal bifurcation 5mm in length while mesial aspect 3mm in dimension Occlusal Aspect 1. The occlusal outline is rhomboidal with greater bucco-lingual measurement mesially than distally, and greater mesio-distal measurement lingually than buccally. 2. Four well-developed cusps can be seen: the mesio-lingual cusp is the largest , then the mesio-buccal, then the distolingual, then the disto-buccal, then the cusp of Carabelli (secondary cusp ). 3. The mesio-buccal and disto-lingual line angles are acute, and the mesio-lingual and disto-buccal line angles are obtuse. 4. There is an oblique ridge formed by the union of the triangular ridge of the disto-buccal cusp and the distal ridge of the mesiolingual cusp, crossing the occlusal surface obliquely. 5. There are four fossae: (A) Major fossae: (i) mesial Central fossa: roughly triangular in shape, located mesial to the oblique ridge. (ii)linear Distal fossa: located distal to the oblique ridge. (B) Minor fossae: (i) Mesial triangular fossa: located distal to the mesial marginal ridge. (ii) Distal triangular fossa: located mesial to the distal marginal ridge. 6. There are six developmental grooves: (A) Central developmental groove: from the central pit to the mesial triangular fossa. 5 Almaaqal University Dental Anatomy Dr. Bahaa Altememi College of dentistry lec. 11 (B) Buccal developmental groove: from the central pit to the buccal surface between the mesio-buccal and disto-buccal cusps. (C) Distal oblique groove: from the distal triangular fossa going obliquely. (D) Lingual developmental groove: this groove joins with the distal oblique groove going between the mesio-lingual and disto-lingual cusps in a cervical direction. (E) Transverse groove of the oblique ridge: this groove crosses the oblique ridge. (F) Fifth cusp groove: this groove passes between the fifth cusp and the mesio- lingual cusp. 7. There are three pits: (A) Central pit: it is located at the deepest part of the central fossa, at the junction between the central groove and the buccal developmental groove. (B) Mesial pit: it is located at the deepest part of the mesial triangular fossa. (C) Distal pit: it is located where the distal fossa and distal triangular fossa join. 6