Dental Anatomy Module REVIEW for Test 2

1. Dental Anatomy ModuleREVIEWforTest #2

2. 40 Questions >Permanent Maxillary Premolars = 3 questions >Permanent Mandibular Premolars = 8 questions >Permanent Maxillary First Molars = 10 questions >Permanent Maxillary Second Molars = 5 questions >Permanent Maxillary Third Molars = 2 questions >Permanent Mandibular First Molars = 7 questions >Permanent Mandibular Second Molars = 1 question >Permanent Mandibular Third Molars = 1 question >Pulp & Root Morphology = 3 questions

3. Background Information for Taking Dental Anatomy Examinations

4. Note: Know the lingual cusp positioning on the Permanent Maxillary First Premolar.

5. Note: Know the general crown forms on the Permanent Maxillary Second Premolar.

6. Note: Know the marginal ridge anatomical differences on the Permanent Maxillary First Premolar.

7. Note: Make certain that you know the differences between the facial, lingual and mesial surfaces for both mandibular premolars.

8. Note: Know the differences between the mandibular premolars regarding their occlusal views.

9. Note: Know all of the anatomical features present on the mandibular first premolar from a facial view

10. Note: Know all of the anatomical features for the mandibular first premolar from a mesial view

11. Note: Know all of the anatomical features for the mandibular second premolar from a lingual view 3-cusp variety has 2 lingual cusps with a lingual groove between them Lingual groove is distally positioned Mesiolingual cusp tip is 1.5 mm shorter than facial cusp tip Distolingual cusp tip is 2.0 mm shorter than facial cusp tip Mesiolingual cusp is wider than the distolingual cusp Spheroidal lingual surface contour Crown has almost the same mesiodistal width on the lingual surface, as it does on the facial surface Convex root surface Root apex has distal orientation

12. Note: Know all of the anatomical features for the mandibular second premolar from an occlusal view Facially located contact areas are also wide faciolingually Rounded facial outline with little evidence of 3 lobes Nearly square occlusal outline with little lingual convergence seen Lingual mesiodistal measurement may be slightly wider than facial mesiodistal measurement. Only mandibular tooth that has this. Straight lingual outline with indentation at lingual groove 3 distinct cusps in decreasing size: Facial, Mesiolingual, Distolingual Facial cusp is slightly mesial and facially positioned Lingual cusp tips are close to lingual outline of occlusal table Mesiolingual cusp is wider than distolingual cusp Right angle connections between the cuspal ridges and marginal ridges 3-cusp variety does not have a transverse ridge Central groove has a mesial and distal component and is lingually positioned Outline of developmental grooves is a “Y” shaped pattern Central pit in center of occlusal table

13. Note: Know the root structure and furcation area profile on the facial aspect of a permanent maxillary first molar The cervical line curves apically and comes to a definite point near the center, in alignment with the furcation between the mesiofacial and distofacial roots. Mesiofacial root extends mesially for two-thirds of its length, then curves slightly to the distal. Distofacial root is straighter and shorter than the mesiofacial root. The root trunk averages 4 mm in length. There is a broad concave area between the roots extending from the cervical line into the furcation area. The depression does not cross the cervical line. The lingual root is evident and is the longest of the three roots by about 1.0 mm.

14. Note: Know the occlusal cusp design and lingual cusp positions on the lingual aspect of a permanent maxillary first molar Mesiolingual and distolingual cusp tips are considered blunt and not pointed, especially in comparison to the facial cusps. Mesiolingual cusp is very wide mesiodistally and occupies about three-fifths of the total mesiodistal measurement of the crown. Its cuspal ridges meet at a wide obtuse angle at the cusp tip. Its mesial cuspal ridge meets the relatively straight mesial outline of the crown at a 90? right angle. Distolingual cusp is well developed. It takes up the remaining two-fifths of the total mesiodistal width of the crown. Its tip is so rounded that it is sometimes described as spheroidal. The occlusal outline of this cusp joins the distal outline of the crown in an arc that is almost that of a semicircle. Carabelli’s cusp is located on the lingual aspect of the mesiolingual cusp. Its cuspal ridges are parallel to, and about 2.0 mm cervical to the occlusal outline of the mesiolingual cusp. As with all cusps, this cusp is considered to have four cuspal ridges, albeit at times they may be difficult to define.

15. Note: Know the facial and lingual contour outlines and the occlusal cusp positions on the mesial aspect of a permanent maxillary first molar Crown outline is trapezoidal with the shorter parallel side at the occlusal and the longer parallel side at the cervix. Greatest curvature of the facial outline is within the cervical third of the crown. Greatest curvature of the lingual outline is near the middle third of the crown. Since the ML cusp is taller than the DL cusp and the MF cusp is taller than the DF cusp and the mesial marginal ridge is higher than the distal marginal ridge, little if any of the occlusal anatomy is visible from this view. The lingual outline of the crown will reflect the position of the fifth (Carabelli’s) cusp by showing a slight indentation about 2.0 mm cervical to the mesiolingual cusp tip.

16. Note: Know the mesiofacial and lingual root profiles and root surface depressions on the mesial aspect of a permanent maxillary first molar The mesiofacial root presents a relatively wide but shallow depression for almost its entire length. This root depression extends occlusally across the root trunk area and cervical line onto the cervical one-third of the crown. The facial outline of the mesiofacial root often extends facially in its middle one-third a little beyond the greatest projection of the crown and then curves lingually to a relatively blunt apex that is more or less in line with the tip of the mesiofacial cusp. The lingual outline is relatively straight to the area of trifurcation. The lingual (palatal) root is the longest of the three roots. It is said to be banana shaped. From the mesial view the facial outline of this root is concave while the lingual outline is convex. The lingual outline of this root in its middle and even its apical third may extend lingually beyond the greatest lingual projection of the crown.

17. Note: Know the occlusal cusp sizes and positions, the contact area locations, and the overall crown size features on the occlusal aspect of a permanent maxillary first molar Somewhat rhomboidal crown outline. Crown wider mesially than distally (distal convergence) and wider lingually than facially (unique feature of this tooth). Four well developed cusps. One minor fifth cusp (Carabelli’s) on the lingual of and augmenting the mesiolingual cusp. Cusp size: very large mesiolingual cusp followed in size by mesiofacial, distolingual, distofacial and fifth (Carabelli’s) in that order. The maxillary first molar has a well developed distolingual cusp. Mesial contact area is facial to the faciolingual bisector. Distal contact area is centered faciolingually.

18. Note: Know the full extent and depth of the oblique ridge and the cuspal ridge positions on the occlusal aspect of a permanent maxillary first molar The oblique ridge (characteristic of all maxillary molars) extends from the tip of the mesiolingual cusp diagonally across the tooth to the tip of the distofacial cusp. The oblique ridge is produced by the meeting of (1) the triangular ridge of the distofacial cusp and (2) the distal cuspal ridge of the mesiolingual cusp. The low point of the ridge (where the two ridges meet) is at the same level as the mesial and distal marginal ridges. The distal cuspal ridge of the mesiolingual cusp takes a wide swing toward the distal before turning facial and meeting the distofacial cusp. Each cusp has cuspal ridges that extend laterally (mesially and distally) from the tip of the cusp.

19. Note: Know the occlusal cusp heights and root positions and angulations on the facial aspect of a permanent maxillary second molar compared to the permanent maxillary first molar The permanent maxillary second molar from the facial view is similar to the first molar with the following exceptions: The difference in cusp height of the two facial cusps is greater. The distofacial cusp of this tooth is always shorter than the mesiofacial cusp. The maxillary second molar is positioned in the arch such that the facial cusp tips maintain the convex arc of the Curve of Spee. The facial groove is shorter. The lateral depression described for the first molar is not present or is very shallow on the second. The root trunk is longer than that of the 1st molar. The overall root lengths (as measured from the cervical line to the apices of the root tips) may be as long or even longer than the roots of the maxillary 1st molar. The actual roots (as measured from the bifurcation to the root tip apices) are shorter and less divergent. In fact, in a few instances they will be very close together or even fused. They are much more likely to curve distally.

20. Note: Know the occlusal groove pattern and outline form on the occlusal aspect of a permanent maxillary second molar Crown outline from this view will usually be that of a rhomboid. The mesiolingual line angle and distofacial line angles are obtuse. The distolingual line angle and mesiofacial line angles are acute. This rhomboidal form presents four well developed functional cusps on its occlusal surface. The central groove extends mesially from the central pit in the central fossa to the mesial pit in the mesial triangular fossa. The distal oblique groove extends from the distal pit in the distal triangular fossa in a lingual direction parallel to the oblique ridge. It continues onto the lingual surface as the lingual groove. The mesial contact area is located facial to the faciolingual bisector. The distal contact area is centered faciolingually.

21. Note: Know the anatomical differences that occur between the maxillary first and second molars on their respective occlusal aspects The maxillary 2nd molar has similar occlusal anatomy to the maxillary 1st molar with the following exceptions: Rarely has fifth or Carabelli’s Cusp. The distolingual cusp is smaller. In some specimens, it is quite small giving this tooth a “heart shaped” appearance which is more characteristic of a third molar crown. The primary cusp triangle characteristic of all maxillary molars is identifiable since it does not include the distolingual cusp. This “heart” type is still considered to have four cusps although at least one textbook considers this tooth to have only three functional cusps. When the distolingual cusp is small in size, the oblique ridge and the distal marginal ridge often become difficult to distinguish as separate landmarks. In some specimens, the triangular ridge of the distofacial cusp and the distal cuspal ridge of the mesiolingual cusp do not exactly meet and the transverse groove of the oblique ridge is quite deep. When compared to the first molar, the maxillary second molar usually has more secondary grooves.

22. Note: Know the anatomical differences that occur between the maxillary second and third molars on their respective lingual aspects The maxillary third molar from the lingual view is also similar to that view of a permanent maxillary second molar with some exceptions: The mesiolingual cusp tip is more centered mesiodistally. The mesiolingual cusp dominates the mesiodistal width of the crown. Often the distolingual cusp is so short, narrow and rounded that the lingual groove is evident as a mere fold in the enamel and the cusp seems to have little height at all. Difference in root curvature and divergence as described previously.

23. Distal marginal ridge is slightly lower than the mesial marginal ridge More of the occlusal surface can be viewed from the distal, as opposed to the mesial view Long portion of the triangular ridge of the facial cusp is evident from this view Mesiolingual cusp can be see over the height of the distolingual cusp Lingual height of contour is in the occlusal 1/3 Cervical line is almost flat across All three cusp tips can be seen from the distal view Note: Know the distal surface of the permanent mandibular second premolar.

24. Y-type 3 cusps/5 lobes Developmental depressions 3 pits U-type 2 cusps/4 lobes 2 pits H-type 2 cusps/4 lobes 2 pits Note: Know the differences between the Y, U, and H type mandibular second premolars.

25. Note: Know which features are present on the facial surface of the crown and root of the permanent maxillary first molar.

26. Note: Know the occlusal groove structure on the occlusal surface of the permanent maxillary first molar.

27. Note: Know which of the three roots on the permanent maxillary first molar is the largest in overall surface area.

28. Note: Know the differences and similarities between the permanent maxillary first and second molars.

29. The permanent maxillary second molar is similar in outline and anatomical morphology to the maxillary first molar with the following exceptions: The mesiolingual cusp is more nearly centered. The distolingual cusp is shorter and much less developed. Very rarely is there a fifth (Carabelli’s) cusp. The root depression does not extend onto the crown. Roots curve to the distal so that the lingual (palatal) root apex is in line with the distolingual cusp tip. Note: Know the anatomical features present on the lingual surface of a permanent maxillary second molar.

30. Crown outline from this view will usually be that of a rhomboid. The mesiolingual line angle and distofacial line angles are obtuse. The distolingual line angle and mesiofacial line angles are acute. This rhomboidal form presents four well developed functional cusps on its occlusal surface. The central groove extends mesially from the central pit in the central fossa to the mesial pit in the mesial triangular fossa. The distal oblique groove extends from the distal pit in the distal triangular fossa in a lingual direction parallel to the oblique ridge. It continues onto the lingual surface as the lingual groove. The mesial contact area is located facial to the faciolingual bisector. The distal contact area is centered faciolingually. Note: Know several of the features on the occlusal surface of a permanent maxillary second molar.

31. Generally, this tooth has the greatest variation in morphology of any tooth in the permanent dentition. From the occlusal view, the crown outline is described as heart shaped. The occlusal anatomy is similar to that of other maxillary molars. This is particularly true of the Primary Cusp Triangle (Trigon) area. The distolingual cusp and distal marginal ridge will be dissimilar in the following ways: The distolingual cusp will be shorter and narrower (mesiodistally). The distal outline will be more rounded. It is often difficult to distinguish definite, separate cuspal and triangular ridges on the distolingual cusp. Often, the distolingual cusp is seen as only a minor elevation or “Talon”. Often, the distal marginal ridge is hardly discernible. Likewise, definite lingual, distal oblique and distolingual grooves are hard to distinguish. Often, this whole area of the crown becomes a single convex roll of enamel from the crest of the oblique ridge onto the distal surface. Note: Know the reason behind why the occlusal surface shape of the permanent maxillary third molar is heart-shaped.

32. Outline of the facial surface is trapezoidal with the longer parallel side at occlusal. All cusps are visible since the lingual cusps are taller than facial cusps As previously noted, the lingual cusps are more pointed while facial cusps (even before wear) are more rounded. The mesiofacial cusp is the widest of the three facial cusps. Its cuspal ridges meet at an angle that is almost flat. The distofacial cusp is almost as wide as the mesiofacial cusp but its cuspal ridges meet more at an angle, yet the cusp tip is still considered rounded. The distal cusp makes up a very small part of the total mesiodistal width of the facial surface because most of the cusp is lingual to the distofacial line angle placing it on the distal aspect of the tooth. The distal cusp is also very rounded occlusally but more pointed than either the mesiofacial or distofacial cusp. There are two facial grooves seen from the facial view. The mesiofacial groove separates the mesiofacial and the distofacial cusps. The distofacial groove separates the distofacial and distal cusps. Note: Know the facial aspect of the permanent mandibular first molar.

33. From a lingual view the two taller more pointed lingual cusps will be seen. Since this tooth converges toward the lingual, a part of the outline of the distal cusp will be visible as well. The mesiolingual cusp will usually be somewhat taller and a little wider than the distolingual cusp. The lingual developmental groove extends a short distance onto this surface separating the two cusps but rarely if ever is deep enough to require restoration (i.e., not fissured). The lingual surface of each cusp (lobe) is generally spheroidal in the occlusal half. The cervical half of the entire lingual surface is relatively smooth and flat. It should be noted that the anatomical crown length is the same when measured facially or lingually although the lingual cusps are taller. The cervical line is positioned occlusally approx. 1.0 mm more so on the lingual surface than on the facial surface. Therefore, the root trunk measurement will also be 1 mm longer (average 4.0 mm) from cervical line to bifurcation on the lingual aspect of the tooth. It can also be said that when measured on the lingual, the total root length is greater because the roots are measured from the cervical line to the apex. The surface of the root trunk is comparatively flatter than on the facial aspect. The developmental depression is deep at the bifurcation; however it quickly becomes progressively more shallow and fades out entirely before it reaches the cervical line. Note: Know the aspects listed below for the lingual surface of the permanent mandibular first molar.

34. The cervical line curves occlusally about 1.0 mm near the center of its mesial segment. Only the mesial root is visible since it is wider faciolingually than the distal root and is usually a little longer. The mesial root apex is located directly below the mesiofacial cusp slightly facial to the faciolingual long axis bisector of the crown. This also contributes to a shorter, straighter facial root outline compared to a longer more slanted lingual outline. The mesial root presents a rather wide developmental root depression extending the full length of the root. A similar depression will be found on the distal side of this same root as well. From both mesial and distal aspects, this root is convex at its facial and lingual borders with this broad concavity in between. Note: Know the features below regarding the mesial view of the permanent mandibular first molar.

35. The distal cusp is located far enough around the distofacial line angle of the tooth to be considered partly on the distal surface. It is also obvious from the occlusal view that the facial surface converges to the lingual as it nears the distofacial line angle. Therefore, from a distal view, the outline of the distal cusp will be seen superimposed on the distofacial cusp. Also, part of the facial surface of the crown will be visible. The distal contact area is comprised exclusively from the distal cusp only. Both the mesial and distal roots will be visible from this view. The distal root is narrower and shorter and the apex is more pointed than the mesial root; therefore, the outline of the mesial root will be evident beyond the outline of the distal root along at least one border. Note: Know the composition of the distal contact area on the permanent mandibular first molar.

36. Occlusal crown outline said to be hexagonal (Wheeler) or pentagonal (Krause) Faciolingual measurement is greatest in mesial half of crown (because of the cervical ridge). Tooth converges toward lingual. The facial half of the crown is much wider than lingual half. Mesial contact area is located slightly facial to the faciolingual bisector and about 1.0 mm cervical to mesial marginal ridge. Note: Know the geometric features from the occlusal view of a permanent mandibular first molar.

37. In order of greatest size development, the cusps are listed: 1) mesiofacial; 2 and 3) (similar in development) mesiolingual and distolingual; 4) distofacial and 5) distal (or fifth) cusp. In order of cusp height: 1) mesiolingual; 2) distolingual (both presenting rather pointed cusps); 3) mesiofacial, 4) distofacial, and 5) distal all presenting rather rounded cusps. Note: Know the cusp sizes and cusp heights on the occlusal surface of the permanent mandibular first molar.

38. Note: Know which features are present on the occlusal surface of a permanent mandibular first molar and which are not present.

39. This tooth varies greatly in morphology and is second only to the maxillary third molar in this respect. Most mandibular third molars crowns conform to the characteristics of a mandibular second molar in the number and arrangement of the four cusps (Type I). They also present a “4+” groove pattern. Other mandibular third molars (Type II) will have five cusps and a groove pattern similar to a mandibular first molar. Both types will usually have a more rounded and narrower distal outline than either a mandibular first or second molar. The occlusal anatomy often presents many supplemental grooves radiating from the basic developmental grooves. Mesial contact area: Center of the middle 1/3 Note: Know the features regarding the Type I and Type II versions of the permanent mandibular third molars.

40. Note: Know the percentages regarding occurrence on the permanent mandibular canine root(s) and canals.

41. Note: Know the percentage frequency of occurrence on the root and canal structure of a permanent maxillary second premolar.

42. Number of canals* Mesiofacial Root Two or more canals 59.2% One canal 40.8% Distofacial Root One canal 98.3% Two or more canals 1.7% Palatal (Lingual) Root One canal 99% Two or more canals 1% Number of roots* Three roots 95.9% Two roots 3.9% Incidence of Fused Roots* Fusion of any 2 or 3 roots 5.2% Note: Know the percentage frequency of occurrence on the root and canal structure of a permanent maxillary first molar.

43. Compendium Review

44. The End