9/4: Principles of Tooth Preparations

Question 1

1. What are the 7 principles of tooth design and restoration design?

Answer 1

a. Preservation of tooth structure
b. Retention form resistance form
c. Added preparation features
d. Marginal integrity
e. Structural durability of the restoration
f. Preservation of the periodontium

Question 2

2. What biologic factors are in consideration with a crown prep?

Answer 2

a. Dental pulp
b. Gingival tissues
c. Adjacent teeth

Question 3

3. This is known as “vital core”

Answer 3

a. Leaving a minimum of 1 mm of dentin surrounding pulp

Question 4

4. What problems can you have with pulpal integrity?

Answer 4

a. Decreases thickness of dentin
b. Heat transfer during preparation

Question 5

5. When preparing a tooth for a crown in a conservative manner, the operator allows for a

Answer 5

a. Morphological reduction

Question 6

6. This is preservation of the basic primary tooth anatomy within the preparation

Answer 6

a. Morphological reduction

Question 7

7. As we create our crown preparation, we need to form the tooth utilizing geometric form criteria we call”

Answer 7

a. Retention
b. Resistance

Question 8

8. Making grooves on the prep were designed for what?

Answer 8

a. Resistance and retention

Question 9

9. The functional cusp bevel is made for

Answer 9

a. Structural durability

Question 10

10. The planar occlusal reduction is made for

Answer 10

a. Structural durability

Question 11

11. The axial reduction was designed for what?

Answer 11

a. Resistance and retention

Question 12

12. This is prevention of removal along the path of insertion

Answer 12

a. Retention

Question 13

13. How is retention created?

Answer 13

a. 2 opposing vertical surfaces with converging surfaces
b. Cements offering frictional resistance
c. Mechanical factors such as dental cements

Question 14

14. This is the prevention of restoration being dislodged by apical or oblique forces

Answer 14

a. Resistance

Question 15

15. Resistance is typically through what forces?

Answer 15

a. Occlusal forces

Question 16

16. Can resistance be through lateral forces that are not along the POI?

Answer 16

Yes

Question 17

17. What is the greatest determining factor in a crown’s dislodgement?

Answer 17

a. Resistance

Question 18

18. Resistance is built into a preparation by forming walls to block anticipated movement due to

Answer 18

a. Leverage
b. Rotation

Question 19

19. What factors can affect the resistance form of a tooth preparation?

Answer 19

a. Total occlusal convergence
b. Preparation wall length
c. Tooth width after preparation
d. Geometric form
e. Surface area of tooth preparation

Question 20

20. These limit the paths of insertion, grooves, boxes vertical planes, pins

Answer 20

a. Geometric forms

Question 21

21. This is defined as the angle of convergence of taper between 2 opposing walls of a tooth preparation

Answer 21

a. Total occlusal convergence

Question 22

22. This is defined as the angle of convergence of taper of one wall of a preparation in relationship to the long axis of the preparation

Answer 22

a. Inclination

Question 23

23. What is the ideal TOC?

Answer 23

a. 6 degrees

Question 24

24. How much convergence do you want on both sides of the prep?

Answer 24

a. 3 degrees = 6 total

Question 25

25. Can you see a crown with no taper?

Answer 25

a. No, some taper is required

Question 26

26. As occlusal crown convergence increases, what happens to retention?

Answer 26

a. Decreases

Question 27

27. What is the maximum crown retention in terms of TOC?

Answer 27

a. 5 degrees

Question 28

28. You get approximately 1⁄5 the retention when the TOC is

Answer 28

a. 20 degrees

Question 29

29. Is convergence directly or inversely proportional to retention?

Answer 29

a. Inversely

Question 30

30. The average TOC of a prepared tooth ends up in what range?

Answer 30

a. 10-20 TOC

Question 31

31. Molar preps tend to have _____ TOC than premolar or anterior teeth

Answer 31

a. More TOC

Question 32

32. Mandibular preps tend to have _____ TOC than maxillary preps

Answer 32

a. Greater

Question 33

33. Posterior preps are generally

Answer 33

a. Shorter with higher occlusal forces

Question 34

34. Posterior preps require more

Answer 34

a. Angled TOC than anterior teeth

Question 35

35. The greater the height of the tooth prep wall, the _____ the retention

Answer 35

a. Greater

Question 36

36. Increased height =

Answer 36

a. Increased area of cementation = increased retention

Question 37

37. For every 1 mm increase in wall height, the retention and resistance form

Answer 37

a. Increases up to 10%

Question 38

38. The wall height should be greater than the

Answer 38

a. Tipping arc of displacement

Question 39

39. The shorter the preparation, the _____ the taper MUST be

Answer 39

a. Less

Question 40

40. The taller the preparation, the ______ the taper MAY be

Answer 40

a. Greater

Question 41

41. Can a narrow tooth with a smaller diameter preparation have greater resistance than a wider, larger diameter tooth when they have the same wall height?

Answer 41

a. Yes bc the tipping arc

Question 42

42. The height/wall ratio should be greater than

Answer 42

a. 0.4 for all teeth

Question 43

43. What is the ideal wall height for molars?

Answer 43

a. 4mm

Question 44

44. What is the ideal wall height for incisors and premolars?

Answer 44

a. 3mm

Question 45

45. How is resistance form assessed?

Answer 45

a. Measure TOC b. Measure wall height c. Measure tooth width ratio

Question 46

46. If the prep does not have the resistance that you want, what modifications can you make?

Answer 46

a. Decrease TOC b. Addition of grooves c. Increase wall height

Question 47

47. Are there times where leaving a crown preparation less than ideal will actually increase the retention and resistance form?

Answer 47

Yes

Question 48

48. What can you do if your TOC is not ideal or your wall height is less than ideal?

Answer 48

a. Geometric forms can be added i. Box ii. Groove iii. Pin hole

Question 49

49. What are the types of geometric forms?

Answer 49

a. Box b. Groove c. Pin hole

Question 50

50. What is most common to use for secondary retention?

Answer 50

a. Grooves

Question 51

51. What is the point of 2nd retention?

Answer 51

a. Increase surface area b. Establish parallelism c. Limits path of draw to one d. Shorten the arc of rotation and increase resistance

Question 52

52. Secondary retentive feature should be ideally cut no deeper than

Answer 52

a. 1.5mm axially and 2mm occlusally

Question 53

53. Groove or box forms must have a definite wall _____ to the direction of the displacing force

Answer 53

a. Perpendicular

Question 54

54. Retention is ______ with increased surface area

Answer 54

a. Increased

Question 55

55. Is surface area as important as TOC or height/width?

Answer 55

No

Question 56

56. The crown should fit as closely as possible to minimize cement width. How big is this?

Answer 56

a. 25 microns

Question 57

57. The size of your finish line determines what?

Answer 57

a. Bulk of material at the margin b. Fit of the restoration

Question 58

58. What are the types of finish lines?

Answer 58

Question 59

59. What are preparation features that contribute to structural durability?

Answer 59

a. occlusal/incisal reduction b. Functional cusp bevel c. Axial reduction

Question 60

60. If you don't have enough axial wall reduction, it will be

Answer 60

a. Difficult to finish and loss of strength

Question 61

61. If you have too much axial reduction, it will cause

Answer 61

a. Plaque trap and periodontal inflammation

Question 62

62. Where should you place margin? (this is how he will ask on exam)

Answer 62

a. Supra-gingivally