Permanent Molars (maxillary).pdf

PERMENENT MAXILLARY MOLARS DR/ ASMAA AHMED FOAD  PERMENENT MAXILLARY MOLARS MAXILLARY FIRST MOLAE ❑ The crown of this tooth is wider buccolingually than mesiodistally. ❑ The maxillary first molar is normally the largest tooth in the maxillary arch. It...

PERMENENT MAXILLARY MOLARS DR/ ASMAA AHMED FOAD  PERMENENT MAXILLARY MOLARS MAXILLARY FIRST MOLAE ❑ The crown of this tooth is wider buccolingually than mesiodistally. ❑ The maxillary first molar is normally the largest tooth in the maxillary arch. It has four well-developed functioning cusps and one supplemental cusp. ❑ Four large cusps of most physiological significance are the mesiobuccal, the distobuccal, the mesiolingual, and the distolingual. A supplemental cusp is called the cusp or tubercle of Carabelli. ❑ This supplemental cusp is found lingual to the mesiolingual cusp. ❑ The fifth cusp used to identify the maxillary first molar. ❑ Chronology: Eruption 6-7 y ❑ Root completion: 9-10 y Buccal Aspect ❑ Geometric out line: Trapezoid with the shortest of the uneven side cervically and longest of the uneven side occlusally. ❑ four cusps can be seen from this aspect, the mesiobuccal, distobuccal, mesiolingual, and distolingual. ❑ The mesiobuccal cusp is broader than the distobuccal cusp, and its mesial slope meets its distal slope at an obtuse angle. ❑ The mesial slope of the distobuccal cusp meets its distal slope at approximately a right angle. The distobuccal cusp is therefore sharper than the mesiobuccal cusp. ❑ Buccal developmental groove divides the two buccal cusps equally. ❑ The cervical line is convex with the convexity toward the roots. ❑ The mesial outline : straight downward and mesially, untill it reaches the crest of contour at contact area. Mesial contact area :located 2/3 from the cervical line in occlusal direction. ❑ The distal outline of the crown: is convex until it reach distal contact area; Distal contact area (The crest of curvature) on the distal side at: half the distance from cervical line to tip of cusp. the distal surface is spheroidal. ❑ All three of the roots may be seen from the buccal aspect. The axes of the roots are inclined distally. the lingual root is the longest, and the two buccal roots are approximately equal in length. ❑ The roots are not straight, although the buccal roots show an inclination to curvature halfway between the point of bifurcation and the apices. ❑ The mesiobuccal root curves distally, starting at the middle third. 1  PERMENENT MAXILLARY MOLARS ❑ Distobuccal root curved mesially at it apical third. ❑ The point of bifurcation of the two buccal roots is located approximately 4 mm above the cervical line. ❑ A deep developmental groove buccally on the root trunk of the maxillary first molar, which starts at the bifurcation and progresses downward, becoming shallower until it terminates in a shallow depression at the cervical line. ❑ molar roots originate as a single root on the base of the crown. They then are divided into three roots Lingual Aspect ❑ The lingual cusps are the only ones to be seen from the lingual aspect. ❑ The mesiolingual cusp is much larger. Its mesiodistal width is about three fifths of the mesiodistal crown diameter, with the distolingual cusp making up the remaining two fifths. The angle formed by the mesial outline of the crown and the mesial slope of the mesiolingual cusp is almost 90 degrees. ❑ The distolingual cusp :spheroidal and smooth. ❑ The lingual developmental groove starts approximately in the center of the lingual surface mesiodistally, and continues on to the occlusal surface. ❑ The fifth cusp (Cusp of Carabelli) appears attached to the mesiolingual surface of the mesiolingual cusp. It is outlined occlusally by an irregular developmental groove called fifth cusp developmental groove. ❑ All three of the roots are visible from the lingual aspect, with the large lingual root making up most of the roots. ❑ The lingual root is conical, terminating in a blunt rounded apex. ❑ All of the mesial outline of the mesiobuccal root and part of its apex may be seen from this angle. ❑ The distal outline of the distobuccal root is seen above its middle third, including all of its apical outline. 2  PERMENENT MAXILLARY MOLARS Mesial Aspect ❑ the only cusps seen from this aspect: are the mesiobuccal, the mesiolingual, and the fifth cusps. ❑ Buccal outline: Starting from cervical line makes a short arc buccally to its crest of curvature (maximum convexity) at the cervical third of the crown. The outline progresses downward and inward to circumscribe the mesiobuccal cusp, ending at the tip of the cusp. ❑ The lingual outline of the crown curves outward and lingually approximately to the same extent as on the buccal side. The the crest of curvature (maximum convexity) at middle third of the crown. ❑ If the fifth cusp is well developed, the lingual outline dips inward to demarcate it. If it is undeveloped, the lingual outline continues from the crest of curvature as a smoothly curved arc to the tip of the mesiolingual cusp. ❑ The mesiobuccal root and palatal root can be seen from this aspect. ❑ The mesiolingual cusp is on a line with the long axis of the lingual root. ❑ The mesial marginal ridge, irregular which is continuous with the mesiobuccal and mesiolingual cusp ridges. ❑ The cervical line of the crown is irregular, curving occlusally. ❑ The mesial contact area approximately at the junction of the middle and occlusal thirds of the crown buccally located. ❑ The mesiobuccal root is broad and flattened on its mesial surface; The width of this root is approximately two thirds buccolingually. ❑ The buccal outline of the mesiobuccal root extends upward and outward from the crown, ending at the blunt apex. ❑ The lingual outline of the mesiobuccal root is straight from the bluntly rounded apex down to the bifurcation with the lingual root. ❑ The lingual root is longer than the mesial root but is ❑ narrower from this aspect. It is banana-shaped, convex from its lingual outline and concave from buccal outline. At its apex is rounded, the root appears more pointed than the mesiobuccal root. 3  PERMENENT MAXILLARY MOLARS ❑ The level of the bifurcation is a little closer to the cervical line than is found between the roots buccally. ❑ A smooth depression continuous with the bifurcation extends occlusally and lingually almost to the cervical line. Distal Aspect ❑ The outline of the distal aspect is similar to that of the mesial aspect. Certain variations must be noted when the tooth is viewed from the distal aspect. ❑ Because of the distobuccal convergency of most of the buccal surface of the crown may be seen from the distal aspect. This is because the buccolingual measurement of the crown mesially is greater than the same measurement distally. ❑ The distal marginal ridge dips sharply in a cervical direction, exposing the distal portion of the occlusal surface of the crown. ❑ The cervical line is almost straight across from buccal to lingual. ❑ The distal surface of the crown is generally convex ❑ The distobuccal root is narrower at its base than either of the others. An outline of this root start as concave path, then turns outward in a buccal direction to make convex arc from the concavity to the rounded apex. This line lies within the borders of the outline of the mesiobuccal root. ❑ The lingual outline of the root from the apex to the bifurcation is slightly concave. ❑ The bifurcation located 5mm from cervical line. 4  PERMENENT MAXILLARY MOLARS Occlusal Aspect ❑ occlusal aspect, the maxillary first molar is somewhat rhomboidal. crown is wider mesially than distally and wider lingually than buccally. ❑ The four major cusps are well developed, with the small minor, or fifth, cusp appearing on the lingual surface of the mesiolingual cusp near the mesiolingual line angle of the crown. ❑ The fifth cusp may be attreted, or all the cusp form may be absent. At this site, however, developmental groove demarkating it always present in the enamel. ❑ The mesiolingual cusp is the largest cusp; it is followed in size by the mesiobuccal, distolingual, distobuccal, and fifth cusps. ❑ rhomboidal figure as follows: acute angles, mesiobuccal and distolingual; and obtuse angles, mesiolingual and distobuccal. ❑ Developmentally, only three major cusps can be considered as primary, the mesiolingual cusp and the two buccal cusps. The distolingual cusp is common to all of the maxillary molars; any other additional one, such as the cusp of Carabelli on first molars, are called secondary cusps.. ❑ The distolingual cusp becomes progressively smaller on second and third maxillary molars, often disappearing as a major cusp. ❑ the triangular arrangement of the three important molar cusps is called the maxillary molar primary cusp triangle. ❑ There are two major fossae and two minor fossae. The major fossae are the central fossa, which is roughly triangular and mesial to the oblique ridge, and the distal fossa, which is linear and distal to the oblique ridge. ❑ The central fossa of the occlusal surface is a concave area. it contains central developmental pit. ❑ From this pit the buccal developmental groove radiates buccally, continuing on to the buccal surface of the crown between the buccal cusps. ❑ Starting again at the central pit, the central developmental groove is seen to progress in a mesial direction. The central groove usually terminates at the apex of the mesial triangular fossa. Here it is joined by short, supplemental grooves that radiate from its terminus into the triangular fossa. 5  PERMENENT MAXILLARY MOLARS ❑ These supplemental grooves often appear as branches of the central groove. ❑ Occasionally one or more supplemental grooves cross the mesial marginal ridge of the crown. ❑ The two minor fossae are the mesial triangular fossa, immediately distal to the mesial marginal ridge, and the distal triangular fossa, immediately mesial to the distal marginal ridge ❑ mesial triangular fossa is triangular in shape, with its base at the mesial marginal ridge and its apex at the point where the supplemental grooves join the central groove. ❑ The distal fossa of the maxillary first molar is linear in form and is located immediately distal to the oblique ridge. ❑ An irregular developmental groove traverses its deepest portion. This developmental groove is called the distal oblique groove. It connects with the lingual developmental groove at the junction of the cusp ridges of the mesiolingual and distolingual cusps. ❑ The oblique ridge is a ridge that crosses the occlusal surface obliquely. The union of the triangular ridge of the distobuccal cusp and the distal ridge of the mesiolingual cusp forms it. This ridge is reduced in height in the center of the occlusal surface. Sometimes it is crossed by a developmental groove. Called transverse groove of the oblique ridge ❑ The mesial marginal ridge and the distal marginal ridge are irregular ridges continuous with the mesial and distal cusp ridges of the mesial and distal major cusps. ❑ The distal outline of the distal marginal ridge of the crown shows a slight concavity. 6  PERMENENT MAXILLARY MOLARS Pulp Cavity ❑ Proximal Aspect ❑ The mesiobuccal root is often very wide buccolingually and usually possesses an accessory canal commonly called MB2, which usually is the smallest of all the canals in this tooth. ❑ The pulp horns are usually prominent. ❑ The palatal root usually has the largest canal. ❑ Buccal aspect ❑ The pulp horns are very distinct from this view, with the mesiobuccal pulp horn usually appearing a little larger than the distobuccal pulp horn. ❑ The pulp chamber is square ❑ The root canals appear much small. The canals taper slightly as they approach the apical foramen. 7  PERMENENT MAXILLARY MOLARS ❑ Cervical Cross Section ❑ The cervical outline form of the maxillary first ❑ molar is rhomboidal with rounded corners. 8  PERMENENT MAXILLARY MOLARS MAXILLARY SECOND MOLAR Buccal Aspect From the buccal aspect the crown is a little shorter cervico occlusally and narrower mesiodistally than is the maxillary first molar. The distobuccal cusp is smaller and allows part of the distal marginal ridge and part of the distolingual cusp to be seen. The buccal roots are about the same length. These roots are more nearly parallel and inclined distally more than those of the maxillary first molar, so that the end of the distobuccal root is slightly distal to the distal extremity of the crown. The apex of the mesiobuccal root is on a line with the buccal groove of the crown instead of the tip of the mesiobuccal cusp, as was found on the first molar Lingual Aspect Ways in which the second molar differs from the first molar:  1. The distolingual cusp of the crown is smaller.  2. No fifth cusp is evident.  3.The apex of the lingual root is in line with the distolingual cusp tip instead of the lingual groove as was found on the first molar. 9  PERMENENT MAXILLARY MOLARS Mesial Aspect The buccolingual dimension of the second molar is about the same as that of the first molar, but the crown length is less. The roots are within the confines of the buccolingual crown outline. Distal Aspect ❑ Because the distobuccal cusp is smaller in the maxillary second molar than in the first molar, more of the mesiobuccal cusp may be seen from this angle. ❑ The mesiolingual cusp cannot be seen. The apex of the lingual root is in line with the distolingual cusp. Occlusal Surface ❑ The rhomboidal type of second maxillary molar is most common, although in comparison with the first molar, the acute angles of the rhomboid are less and the obtuse angles greater. ❑ The buccolingual diameter of the crown is about equal to upper 6, but the mesiodistal diameter is approximately 1 mm less. ❑ The mesiobuccal and mesiolingual cusps are just as large and well developed as in the first molar, but the distobuccal and distolingual cusps are smaller and less well developed. ❑ more distobuccal convergence distally is seen than in the maxillary first molar. ❑ more supplemental grooves and pits on the occlusal surface of a maxillary second molar than are usually found on that of a maxillary first molar. 10  PERMENENT MAXILLARY MOLARS MAXILLARY THIRD MOLAR ❑ often appears as a developmental anomaly. It can vary considerably in size, contour, and relative position to the ❑ The crown is smaller, and the roots are shorter as a rule, with the inclination toward fusion with the resultant anchorage of one tapered root. ❑ The predominating third molar design, when the occlusal surface is viewed, is that of a heart-shaped type of second molar. The distolingual cusp is very small and poorly developed in most cases, and it may be absent entirely. ❑ All third molars, mandibular and maxillary, show more variation in development than any of the other teeth in the mouth. Occasionally they appear as anomalies bearing little or no resemblance to neighbouring teeth. Buccal Aspect From the buccal aspect, the crown of the third molar is shorter cervico-occlusally and narrower mesiodistally than that of the second molar. The roots are usually fused, functioning as one large root, and they are shorter cervicoapically. The fused roots end in a taper at the apex. The roots have a distinct slant to the distal, giving the apices of the fused root a more distal relation to the center of the crown. Lingual Aspect only one large lingual cusp is present, and therefore no lingual groove is evident However, in many cases, a third molar with the same essential features has a poorly developed distolingual cusp with a developmental groove lingually. 11  PERMENENT MAXILLARY MOLARS Mesial Aspect ❑ the main feature is the taper to the fused roots and a bifurcation, usually in the region of the apical third. ❑ The root portion is considerably shorter in relation to the crown length. ❑ Both the crown and the root portions tend to be poorl developed, with irregular outlines. Distal Aspect ❑ From the distal aspect, most of the buccal surface of the crown is in view ❑ More of the occlusal surface may be seen than can be seen on the second molar from this aspect because of the more acute angulation of thE occlusal surface in relation to the long axis of the root. ❑ The measurement from the cervical line to the marginal ridge is short. Occlusal Aspect ❑ The occlusal aspect of a typical maxillary third molar presents a heart-shaped outline ❑ The lingual cusp is large and well developed, and little or no distolingual cusp is evident, which gives a semicircular ❑ outline to the tooth from one contact area to the other. ❑ Three functioning cusps are seen on this type of tooth: two buccal and one lingual. ❑ The occlusal aspect of this tooth usually presents many supplemental grooves. ❑ The third molar may show four distinct cusps. This type may have a strong oblique ridge, a central fossa and a distal fossa, with a lingual developmental groove similar to that of the rhomboidal type of second molar. In most instances, the crown converges more lingually from the buccal areas than in the second molar, losing its rhomboidal outline. 12  PERMENENT MAXILLARY MOLARS QUESTIONS: ❑ Which three grooves radiate out from the central fossa in a maxillary first molar? central, transverse groove of oblique ridge, and buccal. ❑ Which cusp on a maxillary first molar has two ridges: one that forms part of a transverse ridge and the other that forms part of an oblique ridge? Mesiolingual ❑ Which cusp is the largest and longest on a maxillary second molar? Mesiolingual ❑ Which cusp is most likely to be absent on a maxillary second molar? Distolingual ❑ Of the four fossae on a maxillary first molar, which is the largest? Central circular fossa ❑ Which grooves are likely to radiate out of the mesial triangular fossa on the maxillary first molar ? mesiobuccal and mesiolingual fossa groove, mesial marginal ridge groove, and central ❑ Which molars have the greatest morphological variance of all teeth? third molars ❑ Which molars includes the "cusp of Carabelli"? maxillary 1st molar. ❑ Which molars present the most supplementary grooves? rd 3 molar ❑ Other than the Cusp of Carabelli, which cusp is likely to be absent on the maxillary second or third molars? Distolingual ❑ Which two cusps have triangular ridges that make up or join to form the oblique ridge on the maxillary molar? mesiolingual and distobuccal ❑ The molar that exhibits 3 roots and is trifurcated ? maxillary molars ❑ What are the three major developmental grooves connected to the central groove in a maxillary 1st molar? transverse, central fossa buccal, and distal oblique ❑ When comparing maxillary 1st molars to maxillary 2nd molars, all of the following distinguishes one from the other EXCEPT: *On maxillary 1st molars all the roots spread out more than on maxillary 2nd molars *The cusp of carabelli is present on the maxillary 1st molars and not on the 13  PERMENENT MAXILLARY MOLARS maxillary 2nd molars *The distolingual cusp is wider than the mesiolingual cusp on the maxillary 2nd molar *The lingual groove is deeper and more cavity prone on the maxillary 1st molar ❑ Which molar can present with a rhomboidal or a heart-shaped occlusal table? maxillary 2nd molar ❑ Bibliography ❑ Alexandersen V: Mandibular third molar: the root complex. II. Morphogenetic considerations, Tandlægebladet 66:53, 1985. ❑ Ash MM: Wheeler’s atlas of tooth form, ed 5, Philadelphia, 1984, Saunders. ❑ Black GV: Descriptive anatomy of the human teeth, ed 4, Philadelphia, 1897, S.S. White Dental Manufacturing. ❑ Carabelli G: Anatomie des Mundes, Vienna, 1842, Braumuller and Seidel. ❑ Carbonell VM: The tubercle of Carabelli in the Kish dentition, Mesopotamia, 3000 bc, J Dent Res 39:124, 1960. ❑ Carlsen O: Dental morphology, Copenhagen, 1987, Munksgaard. ❑ Diamond M: Dental anatomy, New York, 1929, Macmillan. ❑ Hopewell-Smith A: An introduction to dental anatomy and physiology, Philadelphia, 1913, Lea and Febiger. ❑ Kraus BS: Carabelli’s anomaly of the maxillary molar teeth, Am J Hum Genet 3:348, 1951. ❑ Kraus BS, Jordan RE, Abrams L: Dental anatomy and occlusion, Baltimore, 1969, Williams & Wilkins. ❑ Tomes CS: A manual of dental anatomy, London, 1894, Churchill. ❑ Woelfel JB, Scheid RC: Dental anatomy: its relevance to dentistry, Baltimore, 1997, Williams & Wilkins. 14