1. Chapter 12
Tooth Morphology

2. Anterior Permanent Dentition
Lesson 12.1
Anterior Permanent Dentition
Pronounce, define, and spell the Key Terms.
Discuss the anterior permanent dentition, including:
Identify the location of each anterior permanent tooth.
Use the correct terminology when discussing features of the anterior permanent dentition.
Describe the general and specific features of each tooth in the anterior permanent dentition.
Discuss clinical considerations of each tooth in the anterior permanent dentition.

3. Introduction
There is a certain amount of variation among individual teeth, and every tooth may not meet all criteria for identification
By understanding the characteristics of each tooth, you will be able to differentiate among teeth, as well as between the left teeth and the right teeth in any particular group
What does morphology mean? (Morphology means the shape of teeth.)

4. Clinical Uses for Tooth Morphology
Mounting dental radiographs
Assisting in charting a mouth with missing teeth and teeth that have “drifted”
Selecting temporary crowns or orthodontic bands from a box with a variety of shapes
Forming matrix bands before application
Although morphology provides useful guidelines for the shape and positioning of teeth, there is always a certain amount of individual variation.
Understanding the general characteristics of teeth permits identification and differentiation of an individual’s teeth.

5. Stainless Steel Crowns
A thorough understanding of tooth morphology is useful in selecting the appropriate appliances.
Stainless steel crowns are available in a variety of sizes for each tooth.

6. Anterior Permanent Dentition
There are 12 anterior teeth in the permanent dentition, six in each dental arch
The permanent anterior teeth include the central incisors, lateral incisors, and canines
The central incisors are closest to the midline, the lateral incisors are the second teeth from the midline, and the canines are the third teeth from the midline
All anterior teeth are succedaneous, replacing primary teeth of the same type
Permanent anterior teeth tend to be the first to erupt and replace primary teeth.

7. Attractive Teeth Are Important
People can be extremely self-conscious about the appearance of their front teeth and may take better care of a nice smile than they would of one they are not proud of.
The size, shape, color, and position of the anterior teeth may affect a person’s appearance and self-esteem.

8. Characteristics of Permanent Anterior Teeth
All anterior teeth have a cingulum, a rounded, raised area on the cervical third of the lingual surface
The cingulum corresponds to the lingual developmental lobe
The lingual surface on anterior teeth has rounded, raised borders on the mesial and distal surfaces called marginal ridges
Some anterior teeth have a fossa, which is a wide, shallow depression on the lingual surfaces
Do these lingual surfaces make a difference when the anterior teeth are being brushed? (Yes, it is important to reach all surfaces of the teeth when brushing.)

9. Newly Erupted Permanent Maxillary Incisor
What feature do all anterior teeth have? (They all have a cingulum on the lingual surface.)
Note the thin crown on the incisor, which is an adaptation for tearing food.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

10. Permanent Incisors
There are eight permanent incisors­­: four maxillary and four mandibular
The maxillary group comprises two central incisors and two lateral incisors, as does the mandibular group
These teeth complement each other in form and function
The central incisors erupt about a year or so before the lateral incisors do
The mandibular incisors are smaller than the maxillary incisors. This means that the mandibular canine is normally mesial to the maxillary canine.

11. Maxillary Central Incisors
The maxillary central incisors (#8 and #9) have unique anatomic features
They are larger in all dimensions, especially mesiodistally, than a permanent mandibular central incisor
The labial surfaces are more rounded from the incisal aspect, with the tooth tapering toward the lingual
The root is short compared with the roots of other permanent maxillary teeth
All lingual surface features, including the marginal ridges, lingual fossa, and cingulum, are more prominent on the maxillary central incisor than on the mandibular central incisor
What is the meaning of “mesiodistally”? (It means the width of the tooth.)
The maxillary central incisors are the most prominent teeth in the mouth.

12. Views of a Permanent Maxillary Right Central Incisor
The incisors present a triangular outline.
Note the virtually straight incisal edge and curve in the cervical line.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

13. Maxillary Central Incisors (Cont.)
The incisal edges of these teeth are formed at the labioincisal line angle and do not exist until an edge has been created by wear
The incisal edge is also known as the incisal surface or incisal plane
When newly erupted, the central and lateral incisors have three mamelons, or rounded enamel extensions on the incisal ridge, or edge
The mamelons usually undergo attrition shortly after eruption
What is meant by attrition? (Mechanical wear of teeth during use)
Some incisors may present with a distinctive shovel-shaped appearance on the lingual aspect.

14. Mamelons
Mamelons are the rounded portions of the incisal edge of the lower central incisors.

15. Maxillary Lateral Incisors
The maxillary lateral incisors (#7 and #10) are smaller than the central incisors in all dimensions except root length
They usually erupt after the maxillary central incisors
The crown of a maxillary lateral incisor has a single root that is relatively smooth and straight but may curve slightly to the distal
Recognizing this feature is helpful in the mounting of radiographs
When a lingual pit is present, caries is more likely.

16. Maxillary Lateral Incisors (Cont.)
The lateral incisors vary in form more than any other tooth in the mouth, except the third molars, and are often congenitally missing
Because of the variations in form, the permanent maxillary lateral incisors present challenges during preventive, restorative, and orthodontic procedures
Unattractive open contacts (spaces between teeth), called diastema, often occur in this area because of the variations in tooth size and position in the arch
Treatment for diastemas can include orthodontic treatment, crowns, or veneers.

17. Views of a Permanent Maxillary Right Lateral Incisor
Note the narrow, cone-shaped appearance of the incisor.
These teeth are among the most likely to be missing congenitally or due to heredity.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

18. Pegged Maxillary Lateral Incisor
What are pegged laterals? (Maxillary lateral incisors with a pointed or tapered shape)
Note the conical shape. The maxillary third molars differ from the other teeth considerably in terms of size, contour, and relative position.
From Ibsen OC, Phelan JA: Oral pathology for the dental hygienist, ed 6, St Louis, 2014, Saunders.

19. Mandibular Incisors
The permanent mandibular incisors are the smallest teeth of the permanent dentition and the most symmetric
The central and lateral incisors of the mandibular arch resemble each other
Generally the lateral incisor is larger than the central incisor, in contrast to the teeth in the maxillary arch
Supragingival tooth deposits, such as plaque, calculus, and stain, tend to collect in the lingual concavity of the mandibular incisors
In general the mandibular central incisor is the smallest tooth in the human mouth.
Supernumerary teeth often form among the upper incisors.

20. Mandibular Central Incisors
The mandibular central incisors (#24 and #25) are the smallest and simplest teeth and are bilaterally symmetric
Each has a small centered cingulum, subtle lingual fossa, and equally subtle marginal ridges
The crown of a mandibular central incisor is narrower on the lingual surface than on the labial surface
The developmental horizontal lines on anterior teeth, or imbrication lines, and developmental depressions are usually not present or are very faint
The mandibular central incisors present with a strong degree of bilateral symmetry.

21. Views of a Permanent Mandibular Right Central Incisor
Note the symmetrical nature of the tooth.
The lingual surface is concave, with a slight fossa and cingulum.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

22. Mandibular Lateral Incisors
The mandibular lateral incisors (#23 and #26) are slightly larger than the mandibular central incisors but otherwise similar to them
The lateral teeth usually erupt after the mandibular central incisors
The lateral incisors have a small, distally placed cingulum
The greater height of the cementoenamel junction (CEJ) curvature on the mesial surface than on the distal surface helps distinguish the right mandibular lateral incisor from the left incisor
There is less symmetry in these teeth than in the mandibular central incisors.
The mandibular lateral incisors have slightly larger roots than do the central incisors.

23. Views of a Permanent Mandibular Right Lateral Incisor
Note the “twist” in the incisal edge.
The distal surface tends to have a more pronounced curve than do the central incisors.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

24. Permanent Canines
The permanent canines are the four anterior teeth located at the corner of each quadrant for each dental arch
Their name is derived from the Latin word for dog (canis) because these teeth resemble dogs’ teeth
Patients often complain of the normal slightly deeper yellow color of their canines compared with their incisor teeth
“Cuspid” is an older term that has been used in place of canine.
A cusp is a major elevation on a chewing surface.

25. Permanent Canines (Cont.)
The permanent canines are the longest teeth in the dentition
The root is usually the length of the crown
This large root is externally manifested by the bony vertical ridge called the canine eminence
Patients commonly call the canines their “eye teeth”
The canines are considered the cornerstones of the dentition.

26. Views of Permanent Mandibular and Maxillary Canines
Canines are the only teeth with one cusp.
Note the single root and canine eminence.
A, Labial view.
B, Lingual view
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

27. Maxillary Canines
The maxillary canines (#6 and #11) usually erupt after the mandibular canines, after the maxillary incisors, and possibly after the maxillary premolars
The cusp tip is sharper on a maxillary canine
The mesial cusp slope is usually shorter than the distal cusp slope in both the maxillary and the mandibular canines when they first erupt
The length of these cusp slopes and the cusp tip can change with attrition
The maxillary canine is narrower than the central incisor.

28. Mandibular Canines
The mandibular canines (#22 and #27) usually erupt before the maxillary canines and after most of the incisors have erupted
A mandibular canine closely resembles a maxillary canine
Although the entire tooth is usually as long, a mandibular canine is narrower labiolingually and mesiodistally than a maxillary canine
The lingual surface of the crown of the mandibular canines is smoother than that of the maxillary canines and has a less developed cingulum and two marginal ridges
Lower permanent canines on occasion have a bifurcation near the apex, resulting in two short roots.

29. Views of a Permanent Mandibular Right Canine
Note the lack of symmetry common to all canines.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

30. Clinical Considerations with Canines
The maxillary canines may erupt labially or lingually in relation to the surrounding teeth
The maxillary canines may also fail to erupt fully and may remain impacted
This occurs because the permanent maxillary canines erupt after the maxillary incisors and possibly after the premolars and their arch spaces have closed
What makes the canine teeth self-cleaning? (Their location and shape)
The canines are important in establishing a natural facial contour.

31. Posterior Permanent Dentition
Lesson 12.2
Posterior Permanent Dentition
Discuss the posterior permanent dentition, including:
Identify the location of each posterior permanent tooth.
Use the correct terminology when discussing features of the posterior permanent dentition.
Describe the general and specific features of each tooth in the posterior permanent dentition.
Discuss clinical considerations of each tooth in the posterior permanent dentition.

32. Posterior Permanent Dentition
The permanent posterior teeth include the premolars and molars
The crown of each posterior tooth has an occlusal surface, bordered distally and mesially by marginal ridges
The occlusal surfaces have two or more cusps
Imagine each cusp as a mountain with sloping areas, or cusp ridges, extending from the top of the mountain; between the ridges are sloping areas called inclined cuspal planes
The posterior dentition is important in grinding and chewing food and in maintaining the shape of the face.

33. Occlusal Surface on a Permanent Posterior Tooth
Pictured: Occlusal surface on a permanent posterior tooth and its features.
The premolars are also known as bicuspids because of their two large prominences.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

34. Posterior Permanent Dentition (Cont.)
Each shallow, wide depression on the occlusal table is a fossa
One type of fossa on posterior teeth, the central fossa, is located where the cusp ridges converge in a central point, where the grooves meet
Another type of fossa is the triangular fossa
Sometimes located in the deepest portions of the fossa are occlusal developmental pits
Each pit is a sharp pinpoint depression where two or more grooves meet
How do occlusal pits relate to the fossa on the tooth? (The marginal ridges border the occlusal surface and create an inner occlusal table. Each shallow, wide depression on the occlusal table is a fossa.)
How might dental sealants help the situation of having grooves, pits, and so on? (Dental sealants can prevent particles and bacteria from lodging in grooves and pits, therefore helping to prevent the formation of dental caries.)

35. Features of the Occlusal Table
Pictured: Other features of the occlusal table on a permanent posterior tooth, including the central groove.
What are developmental grooves? (The grooves are sharp, deep, V-shaped linear depressions.)
Note the occlusal pit formed by the junction of grooves.
Pits are more common in teeth with three cusps.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

36. Clinical Considerations with Posterior Teeth
The occlusal surfaces on permanent posterior teeth have pit and groove patterns that make them susceptible to caries (decay)
This occurs because of increased plaque retention and the thinness of the enamel forming the walls of the pits and grooves
The pits and grooves need to be carefully checked for decay with an explorer and mirror and possibly a chemical caries indicator
Posterior teeth with deep pit and groove patterns should have dental sealants placed shortly after erupting.
Would the morphology and position of the posterior teeth make identification of caries more difficult? Why? (Yes. Morphology and position affect the ability to view the teeth.)

37. Permanent Premolars
There are eight premolars in the permanent dentition, two in each quadrant
They are located posterior to the canines and immediately anterior to the molars
There are two types of premolars:
First
Second
Premolars are always anterior to molars.

38. Maxillary First Premolars
A maxillary first premolar (#5 and #12) is larger than a maxillary second premolar
Each maxillary first premolar has two cusps (buccal and lingual) and two roots (facial and lingual)
Both maxillary premolars erupt earlier than the mandibular premolars
The buccal cusp is the larger of the two cusps.
The lower second premolar may, at times, present with two lingual cusps.

39. Maxillary First Premolars (Cont.)
The maxillary first premolar has a bifurcated root (two roots, one buccal and one lingual)
Some first premolars have roots that are joined, or fused
The roots are shorter in length and resemble the roots of the molars
In contrast to the roots, the crowns of the first premolars may closely resemble those of the canines.
Most upper premolars have two roots; fewer than one fifth present with a single root.

40. Clinical Considerations with Premolars
The maxillary and mandibular premolars work with the molars in the chewing of food
The first premolars help the canines in shearing or cutting bits of food
The premolars also support the corners of the mouth and cheeks
When people lose all of their molars, they usually can still chew if they have their premolars.
Unfortunately, the fact that a person is missing one or more maxillary premolars is very noticeable when he or she smiles.

41. Views of a Permanent Maxillary First Premolar
Note the larger buccal cusps and the well-defined occlusal groove.
The concave depression near the root line is known as the canine fossa. Why might this term be misleading? (This might lead one to believe it is located on a canine tooth, rather than a premolar.)
Why is the buccal cusp large and sharp? (To assist the canine with tearing)
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

42. Maxillary Second Premolars
Each maxillary second premolar (#4 and #13) has two cusps (buccal and lingual) and one root
The buccal cusp is shorter, less pointed, and more rounded than the first.

43. Differences Between Second and First Maxillary Premolars
The cusps are closer in length on the second premolar
The lingual cusp is slightly shorter, but not as short as the cusp on the maxillary first premolar
The mesiobuccal cusp slope is shorter than the distobuccal cusp slope on the second premolar
The cusps of the secondary premolar are not as sharp as those of the maxillary first premolar
The second premolar has only one root and one root canal
The second premolar has a slight depression on the mesial root
The second premolar is wider buccolingually than mesiodistally
In most facets, second premolars are similar to but less defined than first premolars.
Many features tend to be more rounded in second premolars.

44. Mandibular First Premolars
Each mandibular first premolar (#21 and #28) has a long and well-formed buccal cusp and a small, nonfunctioning lingual cusp
The lingual cusp may be no larger than the cingulum on some maxillary canines
The mandibular first premolars are smaller and shorter than the mandibular second premolars
The lingual cusp of this tooth is the smallest of any tooth.

45. Views of a Permanent Mandibular Right First Premolar
Note the bilateral symmetry.
Note the large buccal cusp and the diamond shape of the occlusal outline.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

46. Mandibular Second Premolars
The permanent mandibular second premolars (#20 and #29) erupt distal to the mandibular first premolars
They are the succedaneous replacements for the primary mandibular second molars
There are two forms of the mandibular second premolar:
Three-cusp type, or tricuspidate form
Two-cusp type, or bicuspidate form
Mandibular second premolars tend to be larger than the mandibular first premolars, but the buccal cusp in these teeth is less pronounced.
This tooth is one of those most frequently missing as a result of heredity or congenital factors.

47. Views of a Permanent Mandibular Second Premolar
This tooth is one of those most frequently missing as a result of heredity or congenital factors.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

48. Occlusal Views of a Permanent Mandibular Second
A, U-type.
B, H-type.
C, Y-type.
Note the single deep groove in the two-cusp teeth compared with the distinctive Y pattern of the three-cusp tooth.
From Zeisz RD, Nuckolls J: Dental anatomy, St Louis, 1949, Mosby.

49. Permanent Molars
There are 12 molars, three in each quadrant, in the permanent dentition
The molar crowns have four or five short, blunt cusps, and each molar has two or three roots that help support the larger crown
In most individuals, lower molars have two lingual cusps, whereas upper permanent molars present with two buccal cusps.
Lower molars generally have two roots, whereas upper molars generally have three roots.

50. Permanent Molars (Cont.)
The name molar comes from the Latin word for “grinding”
There are three types of molars: first, second, and third
The first and second molars are also called the 6-year and 12-year molars because of the approximate ages at which they erupt
The permanent molars are the largest teeth in the dentition.
Molar teeth are not preceded by primary teeth.

51. Maxillary Molars
Usually the first permanent teeth to erupt into the maxillary arch
Each maxillary molar usually has four major cusps, with two on the buccal portion of the occlusal table and two on the lingual
Each maxillary molar has three well-separated and well-developed roots
A tooth with three roots is said to be trifurcated, which means “divided into thirds”
The distal of the maxillary first molar and mandibular central incisors are prone to periodontitis. The parotid gland exits near this tooth as well, so there is often supragingival calculus on the distobuccal surface.

52. Clinical Considerations with Maxillary Molars
The roots of the maxillary molars may penetrate the maxillary sinus as a result of accidental trauma or during an extraction
The permanent maxillary third molars may fail to erupt and may remain impacted within the alveolar bone
If the maxillary first molar is lost, the second molar can tip and drift into the open space, causing difficulty in chewing and furthering periodontal disease
The roots of the maxillary molars are close to the sinuses, causing some patients to confuse the pain caused by a sinus infection with pain related to their maxillary teeth, and vice versa.
Diagnostic tests can rule out involvement of the maxillary teeth when a patient has what may be a sinus problem.
Impacted third molars can irritate the surrounding tissue, leading to pain and swelling.

53. Maxillary First Molars
The maxillary first molars (#3 and #14) are the first permanent teeth to erupt into the maxillary arch
They erupt distal to the primary maxillary second molars and are therefore nonsuccedaneous (do not replace the primary teeth)
The maxillary first molar is the largest tooth in the maxillary arch and also has the largest crown in the permanent dentition
This molar is composed of five developmental lobes, two buccal and three lingual
The fifth cusp is called the cusp of Carabelli
The cusp of Carabelli is much less pronounced than the other cusps and is of little practical use.
Because of the typical age at the eruption of these teeth, children and parents may need to be told that the maxillary and mandibular first molars are permanent dentition.

54. First Molars A, Maxillary first molar. B, Mandibular first molar.
Note the three roots on the maxillary molar, compared with two on the mandibular.
Note that mandibular molars tend to be wider than maxillary ones, with larger cusps.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

55. Views of a Permanent Maxillary Right First Molar
Note that the size of the roots parallels the buccal and two lingual cusps.
Note that the size of the roots tends to parallel the size of the cusps.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

56. Maxillary Second Molars
The crown of the maxillary second molar is somewhat shorter than that of the first molar, and it usually has four cusps
No fifth cusp is present
There are three roots
The roots of the secondary molars are smaller than those of the first molars
The lingual root is still the largest and longest
The buccal groove is located farther distally on the buccal surface of the second maxillary molar than on the first maxillary molar.
The mesiobuccal cusp of the second maxillary molar is longer and has a more blunt cusp tip than the distobuccal cusp.
Differences in cusp size are more noticeable on the maxillary second molars than on the first.
The roots of the second molars are close together and sometimes fuse.

57. Views of a Permanent Maxillary Right Second Molar
The distolingual cusp varies in size from fairly prominent to very small.
Note the proximity of the three roots.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

58. Maxillary Third Molars
The maxillary third molars (#1 and #16) differ considerably in size and contour
The crown of the maxillary third molar is smaller and the roots are usually shorter
The roots of the maxillary third molar tend to fuse, and the result is a single tapered root
People sometimes refer to the maxillary third molars as the “wisdom” teeth because they erupt last
Maxillary third molars show more variation in morphology than do other teeth.
These teeth are the most likely to be missing as a result of heredity or congenital causes.

59. Buccal Views of Maxillary Right Molars
A, First molar.
B, Second molar.
C, Third molar.
Notice how the roots tend to be closer together when the molars are farther distally. Third molar roots are often fused.
Note the pattern of increasing proximity of the roots from first to third molar.
Note how cusp size and root length diminish in parallel.
Modified from Brand RW, Isselhard DE: Anatomy of orofacial structures, ed 7, St Louis, 2003, Mosby.

60. Views of Permanent Maxillary Right Third Molars
Note the closely proximate or fused roots and the less pronounced cusps compared with those of the first and second molars.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

61. Mandibular Molars
The mandibular molars erupt 6 months to 1 year before the corresponding permanent maxillary molars
The crowns of the mandibular molars have four or five major cusps, with two lingual cusps always of about the same width
All mandibular molars are wider mesiodistally than buccolingually, similar to anterior teeth
The lingual cusps tend to be longer and sharper than the buccal cusps.

62. Mandibular Molars (Cont.)
Each mandibular molar has two well-developed roots, one mesial and one distal
A tooth with two roots is referred to as bifurcated, which means “divided into two”
A bifurcation is the area at which the two roots divide
The mesial root is wider than the distal one.
The two roots are generally the same length.

63. Clinical Considerations with Mandibular Molars
The lingual inclination of the crowns of the mandibular molars can make it difficult to position the oral evacuator
The lingual inclination of the molar teeth can also pose problems in oral hygiene for patients, who may miss the lingual gingiva with the toothbrush
What advice would you give a patient having difficulty carrying out oral hygiene of the mandibular molars? (Answer will vary.)

64. Mandibular First Molars
The permanent mandibular first molars (#19 and #30) erupt between 6 and 7 years of age
These teeth are commonly the first permanent teeth to erupt in the oral cavity
The two roots, mesial and distal, of a mandibular first molar are larger and more divergent than those of a second molar
When this molar has three roots, the mesial root has both buccal and lingual branches.

65. Views of a Permanent Mandibular Right First Molar
Note that the buccal cusps are the largest (and widest) of the cusps.
In general, the distal cusp is poorly developed. In some cases, the molar may have four cusps.
Rare cases present with a sixth cusp.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

66. Mandibular Second Molars
The mandibular second molars (#18 and #31) erupt between 11 and 12 years of age
These teeth erupt distal to the permanent first molars and therefore are nonsuccedaneous
The crown of the mandibular second molar is slightly smaller than that of the first molar in all directions
The crown has four well-developed cusps
Roots on the second molars tend to be shorter than those on the first molars.
A fifth cusp is seen in rare cases.

67. Views of a Permanent Mandibular Right Second Molar
Note the prominent buccal cusps and bifurcated roots.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

68. Mandibular Third Molars
The mandibular third molars (#17 and #32) are similar to the maxillary third molars in that they vary greatly in shape
There is no typical mandibular third molar
This molar is usually smaller in all dimensions than the second molar
The third molar consists of four developmental lobes
A mandibular third molar has two roots that are fused, irregularly curved, and shorter than those of a mandibular second molar
The crown of the mandibular third molar tends to be more rounded than that of a first or second molar.
Four or five cusps may be present.

69. Views of the Permanent Mandibular Right Third Molar
Note the rounded shape of the cusps and the nearly fused appearance of the roots.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

70. Buccal Views of Permanent Mandibular Right Molars
A, First molar.
B, Second molar.
C, Third molar.
Note that the roots are closer together and become shorter from the first molar to the third molar. Third molar roots are often fused.
Note the diminishing prominence of the cusps and increasingly rounded appearance of the crowns.
Modified from Brand RW, Isselhard DE: Anatomy of orofacial structures, ed 7, St Louis, 2003, Mosby.

71. Lesson 12.3 Primary Dentition
Discuss the primary dentition, including:
Compare and contrast the features of the primary and permanent dentitions.
Describe the general and specific features of the primary dentition.
Discuss clinical considerations of the primary dentition.

72. Primary Dentition There are 20 primary teeth:
10 in the maxillary arch
10 in the mandibular arch
Includes incisors, canines, and molars
Numbered in the Universal Tooth Numbering System with the capital letters A through T
Smaller overall and have whiter enamel than the permanent teeth do
The crown of any primary tooth is short in relation to its total length
The crowns are narrower at the cementoenamel junction (CEJ)
The primary teeth are commonly known as “primary,” “baby,” or “milk” teeth.
The primary dentition is also known clinically as the deciduous dentition.

73. Primary Dentition (Cont.)
The pulp chambers and pulp horns in primary teeth are relatively large compared with those of the permanent teeth
There is a thick layer of dentin between the pulp chambers and the enamel, especially in the primary mandibular second molar
The enamel layer is relatively thin
In addition to normal tooth function, the key role of the primary dentition is to maintain proper spacing for the eruption of the permanent dentition.
It is for this reason, more than others, that proper care of the primary dentition is so important.

74. Clinical Considerations with Primary Teeth
Often parents do not understand the importance of the primary teeth
Primary teeth hold the eruption space for the permanent teeth
Because the enamel and dentin are thinner in primary teeth, decay can travel quickly through the enamel to the pulp, possibly causing loss of the tooth
Early dental health education and dental care are essential in keeping the primary dentition
In the primary dentition it is particularly important to retain the second molars.
If these teeth are lost, the first permanent molars are likely to drift out of position.

75. Primary Incisors
The crowns and roots of deciduous incisors are smaller than those of their permanent successors
The roots are twice as long as the crowns and taper toward the apex
If a primary incisor is lost prematurely, a space maintainer is not fabricated. However, if a primary molar is lost, a space maintainer may be fabricated to prevent space loss and ensure adequate room for the adult premolars.

76. Primary Maxillary Central Incisors
The crown of the primary maxillary central incisor (E and F) is wider mesiodistally than incisocervically
It is the only tooth of either dentition with this crown dimension
The primary maxillary incisors have no mamelons
The cingulum and marginal ridges are more prominent than they are on the permanent successor, and the lingual fossa is deeper
The incisors are the first teeth to erupt, beginning 6½ months to about 8 months after birth.
The primary incisor teeth are functional for 5 to 6 years.

77. Views of a Primary Maxillary Right Central Incisor
Note the narrow root and short crown length relative to the root length.
Note the relatively large cingulum.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

78. Primary Maxillary Lateral Incisors
The crown of the primary maxillary lateral incisor (D and G) is similar to that of the central incisor but much smaller in all dimensions
The incisal angles on the lateral incisor are also more rounded than on the central incisor
The lateral root is longer in proportion to its crown, and its apex is sharper
How does the maxillary lateral incisor differ from a central incisor? (The maxillary lateral incisor is more rounded than a central incisor and is longer than it is wide.)

79. Views of a Primary Maxillary Lateral Incisor
Note the similarity of the primary maxillary lateral incisor, except for size, with the central incisor.
Note the sharp apex and long root.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

80. Primary Mandibular Central Incisors
The crown of the primary mandibular incisor (O and P) resembles the primary mandibular lateral incisor more than it does its permanent central successor
The mandibular central incisor is extremely symmetric
It is also not as constricted at the CEJ as the primary maxillary incisor
The lingual surface of the mandibular central incisors appears smooth and tapers toward the prominent cingulum
The crown of the mandibular central incisor is slightly bigger than that of the permanent lateral incisor.

81. Views of a Primary Mandibular Central Incisor
The root is slender and rather long.
How would you compare the morphology of this tooth with the permanent lateral incisor? What are the similarities? (Answers will vary, but may include the observation that the permanent lateral incisor has a more ridged edge.)
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

82. Primary Mandibular Lateral Incisors
The crown of the primary lateral incisor (Q and N) is similar in form to that of the central incisor in the same arch but is wider and longer
The incisal edge of the mandibular lateral incisor slopes distally, and the distoincisal angle is more rounded
The root may have a distal curvature in its apical third and usually has a distal longitudinal groove.

83. Views of a Primary Mandibular Lateral Incisor
Note that the cingulum is more noticeable and the fossa is deeper than in the central incisor.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

84. Primary Canines
There are four primary canine teeth, two in each dental arch
Differ from the outline of their permanent successors in the following ways:
Maxillary canines
The crown of the primary maxillary canine (C and H) has relatively longer and sharper cusp than that of its permanent successor on eruption
The mesial and distal outlines of the primary maxillary canine are rounder
The canines erupt between 16 and 20 months after birth.
The primary canines are sometimes removed to allow other teeth to align properly.

85. Views of a Primary Maxillary Canine
Note that the primary canines may appear to be wider than they are long. This is an optical illusion.
This tooth has a well-developed cingulum and tends to have noticeable ridges on the mesial slope.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

86. Primary Mandibular Canines
The primary mandibular canine (M and R) resembles the primary maxillary canine, but this tooth is much smaller labiolingually
The distal cusp slope is much longer than the mesial cusp slope
The lingual surface of the primary mandibular canine is marked by a shallow lingual fossa
The primary mandibular canine (M and R) resembles the primary maxillary canine, although some dimensions are different
This tooth is much smaller labiolingually
Canines and incisors are considered to be anterior teeth, while premolars and molars are posterior teeth.

87. Views of a Primary Mandibular Canine
Note the thin root and the less obvious cingulum compared with those of the maxillary canine.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

88. Primary Molars
The primary dentition consists of a total of eight primary molars
Each quadrant includes a first primary molar and a second primary molar
Each molar crown is wider than it is tall
The permanent premolars replace the primary molars when they are exfoliated
Primary teeth are smaller than their permanent successors and have relatively larger pulp chambers. It is important that caries be treated promptly in order to prevent exposure of the pulp.

89. Primary Maxillary First Molars
The crown of the primary maxillary first molar (B and I) does not resemble any other crown of either dentition
The height of contour on the buccal surface is at the cervical third of the tooth; on the lingual side, it is at the middle third
The primary maxillary molars have three roots, which are thinner and have greater flare than do those of the permanent maxillary first molar
The lingual root is the longest and most divergent
The crown of the first maxillary molar is the smallest found in the primary molars.

90. Views of a Primary Maxillary First Molar
The first molars erupt between 12 and 16 months after birth.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

91. Primary Maxillary Second Molars
The primary maxillary second molar (A and J) is larger than the primary maxillary first molar
Closely resembles the permanent maxillary first molar but is smaller in all dimensions
The second molar usually has a cusp of Carabelli, the minor fifth cusp
How many pronounced cusps will a primary maxillary second molar have? (Four)

92. Views of a Primary Maxillary Second Molar
The first permanent first maxillary molar may resemble the primary second molar.
Primary maxillary molars have three roots, whereas mandibular molars have two.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

93. Primary Mandibular First Molars
The crown of the primary mandibular first molar (L and S) is unlike any other tooth of either dentition
The height of contour on the buccal surface is at the cervical third of the tooth; on the lingual side, it is at the middle third
Has four cusps; the mesial cusps are larger
Has two roots, which are positioned similarly to those of other primary and permanent mandibular molars
The mesial cusps are the highest and largest on any tooth.

94. Views of a Primary Mandibular First Molar
What makes this tooth’s morphology so unique? (The tooth has a prominent buccal cervical ridge, also on the mesial half of the buccal surface, similar to other primary molars. The height of contour on the buccal surface is seen at the cervical one third of the tooth; on the lingual side, it is noted at the middle one third.)
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

95. Mandibular Second Molars
The primary mandibular second molar (K and T) is larger than the primary mandibular first molar
Most closely resembles in form the permanent mandibular first molar
The three buccal cusps are nearly equal in size, however, and the primary mandibular second molar has an oval occlusal shape.

96. Views of a Primary Mandibular Second Molar
As a practicing dental assistant, you will be surprised at how often your knowledge of tooth morphology and the other dental sciences will directly relate to patient care and your understanding of dental treatment plans.
From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.

97. Questions?