QUIZ # 1 BETCHESSSSS Flashcards Preview

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Flashcards in QUIZ # 1 BETCHESSSSS Deck (84):
1

What is a preparation?

the final shape of the tooth produced by instrumentation to receive a restoration

2

What is a complete veneer crown preparation?

extracoronal prep involving the entire clinical crown

3

What is a Complete Veneer Crown (CVC)?

a cast-gold extracoronal restoration with the clinical crown

4

What is the path of withdrawal (POW)?

the imaginary line along which a casting is moved when it is separated from it's single crowns. The POW should be nearly coincident with the tooth's long axis, which can be formed by opposing axial surfaces in the third of the tooth.
-the specific direction in which a prosthesis is placed on the abutment tooth or removed from it.

5

What is an axial wall?

part of a crown prep prepared in the long axis of the tooth - can be designated as buccal, lingual, mesial or distal.

6

What is the convergence angle and what is the recommended range?

the angle or taper formed by diametrically opposing axial walls
-the recommended range is 2-10 deg
-the ideal range is 6 deg

7

what is a chamfer?

is a type of finish line. the cervical junction of the prepared axial wall and the unprepared portion of the structure. Where the gingival aspect meets the external axial surface of the prepped tooth an an obtuse angle. The chamfer extend around the most cervical portion of the tooth prep.

8

What is the functional cusp bevel?

a wide bevel is placed on the functional cusps (the buccal inclines of the mandibular buccal cusps and the lingual inclines of the maxillary lingual cusps).

9

What is the functional cusp bevel ensure?

the thickness of the tooth structures removed when preparing this bevel ensures that correct contours of the final restoration can be re-established while proving correct convergence and adequate thickness of the restorative materials.

10

What are line angles?

the lines formed by the junction of any two tooth surfaces. These should be rounded in complete crown preps.

11

What are the 3 types of line angles?

1) axial wall line angle
2) occlusoaxial line angle
3) cavo-surface line angle

12

What is an axial wall line angle?

the junction between any two axial walls

13

What is an occlusoaxial line angle?

the junction between the occlusal surface and an axial wall

14

What is a cavo-surface line angle?

the junction of prepared (cut) to unprepared (uncut) tooth structure. This is an external line angle

15

What are depth orientation grooves?

grooves placed on the surface of the tooth to provide a reference to determine when sufficient tooth structure has been reduced.

16

What is an undercut?

-any irregularity in the wall of a prepared tooth that prevents the seating or removal of a casting
- a crown prep is undercut if a wax pattern can't be withdrawn from its die without distortion. This can be caused by:
* a depression in the axial wall maybe caused by a carious lesion - this can be corrected with a base material
* diametrically opposed axial walls that don't converge occlusally caused by improper angulation of the cutting instrument - can be corrected by further tooth reduction

17

What are the principles of tooth preparation?

1) biologic considerations: which affect the health of the oral tissues

18

What are the principles of tooth preparation?

1) biologic considerations: which affect the health of the oral tissues
2) mechanical considerations: which affect the integrity and durability of the restoration
3) esthetic considerations: which affect the appearance of the patient

19

What are the biological considerations of tooth preparation?

-prevention of damage of soft tissues, pulp, and adjacent teeth during tooth preparation
-considerations affecting future dental health like axial reduction, margins, occlusal consideration, and preventing tooth structures
-conservation of tooth structure

20

What are the mechanical considerations of tooth preparation?

1) providing resistance form:
- magnitude and direction of the dislodging forces
- geometry of the tooth prep - walls have a certain angulation
- physical properties for the luting agent - what kind of materials to use
2) providing retention form:
- magnitude of the dislodging forces
- geometry of the tooth prep
- roughness of the fitting surface of the restoration
- materials being cemented
- film thickness of the luting agent
3) preventing deformation of the restoration
- alloy selection
- adequate tooth reduction
- margin design

21

What are the types of crowns?

- CVC : complete veneer crowns
- MCC : metal ceramic crowns
- ACC : all ceramic crowns
- Zirconia crowns: only used on posterior teeth

22

What are some indications of doing a crown?

1) extensive coronal destruction
2) short clinical crowns
3) endodontically treated teeth
4) maximum retention and resistance are needed
5) correction of axial contours / occlusal plane

23

What are some contraindications of doing a crown (what are some reasons why you wouldn't do a crown prep)?

1) wherever an intact buccal or lingual wall exists
2) if less than maximum retention are resistance are needed
3) if objectives can be met with a more conservative restoration

24

What are some advantages of a crown?

-b/c all axial surfaces of the tooth are included in the prep, the complete cast crown has greater retention than a more conservative restoration - larger surface/friction = more retention
- has high strength.
-has greater resistance form than a partial coverage restoration on the same tooth
- a complete cast crows allows the operator to modify axial tooth contour as well as occlusal modifications

25

What are some disadvantages of a crown?

-removal of tooth structure is extensive and can have adverse effects on the pulp and periodontium because of the proximity of the margin to the gingiva, it is not uncommon to see inflammation of gingival tissues
-after cementation, it is no longer feasible to perform electric vitality testing of an abutment tooth b/c of the conduction of the metal
-patients may object to the display of metal associated with complete cast crowns

26

What is the finish line?

it's the terminal portion of the prepared tooth (tooth margin) - where prepared tooth meets the unprepared tooth

27

What are advantages of a chamfer?

distinct margin, adequate bulk, easier to control

28

What are disadvantages of a chamfer?

cared needed to avoid unsupported lip of enamel

29

What are some indications of a chamfer?

cast metal restorations, lingual margin of metal-ceramic crowns = zirconia crowns

30

What is an axial inclination or long axis?

the alignment of the long axis of a tooth to a selected plane, often the horizontal plane

31

How is the long axis determined?

is determined clinically by bisecting the angle formed by opposing axial surfaces in the gingival third of the tooth.

32

What is a taper?

it's defined as the convergence of two opposing external walls of a tooth prep as viewed in a given plane. The extension of those planes form an angles described as the convergence angle. They should converge occlusal at angle 5.5 deg.
- more the taper, the lesser the retention

33

What are the sequences of the steps for a CVC:

-occlusal guide grooves
-occlusal reduction
-axial guide grooves
-axial reduction (buccal and lingual)
-axial reduction (inter proximal)
-finishing and evaluation

34

What kinds of burs do you use for crown preps?

diamond burs: 747.6 M, 242.6 M
carbide burs: 169 L

35

What is the recommended dimension for a central groove for CVC?

1.0 mm

36

What is the recommended dimension for functional cusps for CVC?

1.5 mm

37

where is the functional cusp on the mandible?

on the buccal

38

where is the functional cusp on the maxillary?

on the lingual

39

What is the recommended dimension for non-functional cusps for CVC?

1.0 mm

40

What is the recommended dimension for the chamfer width for CVC?

0.5mm

41

What is the occlusal clearance?

the distance between the occlusal surface of the prepared tooth and the occlusal surface of the opposing tooth. This clearance is evaluated during excursive jaw movements as well as in intercuspal position.

42

What is retention form?

the characteristics of the tooth prep which tends to resist the removal of a restoration along its path of withdrawal

43

What is resistance form?

the characteristics of a tooth prep which tends to prevent dislodgment of a seated restoration by forces directed in an apical or oblique direction. Resistance form prevents dislodgment of the restoration by occlusal forces.

44

What are occlusal guide grooves?

- use 242.6M diamond bur in high speed handpiece
-depth orientation grooves are placed 0.2 mm shallower than the intended tooth reduction to allow for smoothing

45

dimensions of the 242.6M diamond bur

distal portion of bur measure - 0.8 mm
proximal portion of bur - 1.2-1.3 mm

46

dimensions of the 747.2M diamond bur

distal portion of bur measures - .6 mmm
proximal portion of bur measures - 1-1.1 mm

47

Where to place the occlusal guide grooves?

- placed at height of each triangular ridge and in the buccal and lingual grooves as well as fossa grooves
-accurate placement
-1.3 mm deep on the buccal (functional cusp)
- 0.8 mm deep on the lingual (non-functional cusp)

48

How to do occlusal reduction?

-use the 242.6M diamond to remove the tooth structure remains between the groovers
-the tooth is reduced in places which correspond to the anatomical features of the unprepared tooth
-is a two step reduction

49

How to do the functional cusp bevel?

- a wide bevel is placed on the functional cusp
- the depth grooves are 0.8 mm via a 242.6M diamond bur and are placed 45 deg to the long axis of the tooth
- this ensures that correct contours of the final restoration can be re-established while providing adequate thickness of restorative materials

50

How to evaluate the occlusal and axial reductions?

put the silicone putty mold on and use the perio probe to measure.
-also look for undercuts
-inclination of axial walls
-chamfer width and smoothness

51

What is axial reduction?

-it's where you the mark the gingival extension of the prep with a pencil
- clinically: supragingival
- in the typodont, the reduction will be 0.5 mm above the plastic gingiva on buccal and lingual
-use tapered burs like the 242.6M, 747 diamond and 169L carbide burs for this - when moved parallel to the long axis of the tooth will create a tapered surface converging 3-4 deg from the cervical toward the occlusal
* the tips of 242.6M and 243.6M diamonds are hemispherical to produce a chamfer as the bur cuts into the tooth structure

52

How to place the axial guide grooves and axial reduction?

-place 3 shallow grooves in the buccal axial wall and 3 in the lingual axial wall wit ha 242.6M diamond bur
* one groove in the center and one at each medial and distal line angle
-grooves determine the path of withdrawal of the restoration and should be in the long axis of the tooth
-the shank of the diamond must be held parallel to the proposes path of withdrawal
-evaluation of axial guide grooves
- for axial reduction, use a 242.6M diamond to remove the remaining tooth structure between the grooves.
-the top of diamond bur create the chamfer
* slightly short of the pencil mark to allow for finishing
-extend the buccal and lingual reduction into the interproximal area
-don't damage adjacent tooth
-prepare the interproximal area from occlusal until only a narrow island of tooth structure remains
* used 169 L carbide of 747.6 M diamond for this

53

What is the marginal integrity of the restoration?

-the junction of the tooth and restoration at the gingival margin as a potential site of failure due to cement dissolution or roughness.
- the prep should be designed to enable a smooth, strong, well adapted casting.

54

How can inadequate marginal integrity occur?

- the chamfer is too narrow to provide sufficient bulk of restorative material w/o contouring (ideal recommended 0.5mm)
-the cavo-surface ling angle can't easily be determined during lab procedures
-the chamfer is rough or uneven
-the prep is undercut causing distortion of the wax pattern

55

How can excess reduction occur during a crown prep?

-if the tooth is prepped with excessive convergence angle (recommended range is 2-10 deg)
-the prep doesn't follow the anatomical features of the tooth
-the path of withdrawal diverges from the long axis of the tooth
-an excessively wide margin (ideal width is 0.5mm)
-excessively gingival extension of the prep (ideally no further cervically than retention form and existing restorations or defects dictate)

56

What are some causes of inadequate retention and resistance?

-excessive convergence angle (Greater than 10 deg)
-inadequate height and surface area of the axial walls
-insufficient surface area to resist tipping of the restoration

57

How do you finish crown preps?

-the chamfer and axial walls are finished with 242.6M
-the prep should be smooth( a surface with light striation created by the diamond bur)
-a polished surface is unacceptable
-round all sharp line angles

58

What are the recommended dimensions and acceptable ranges of crown preps?

- functional cusp: 1.5 mm (1.3 mm- 1.7 mm)
-central groove: 1.0 mm (0.8 - 1.2 mm)
-non-functional cusp: 1 mm (0.8 - 1.2 mm)
-path of withdrawal: +- 5 deg
- convergence: 6 deg
-chamfer width: 0.5 mm (0.4 - 0.7 mm)
-interproximal chamfer placement: 0.5 mm inter proximal clearance
-linguo-occlusal line angle reduction: 0.8mm(0.6-1.0 mm)
-margin placement: 0.5 mm above plastic gingiva or 1.0 mm coronal to CEJ
-functional cusp bevel: 0.6 mm - 0.8 mm

59

What are the steps of a crown prep?

1) occlusal guide grooves
2) occlusal reduction
3) functional cusp bevel
4) axial guide grooves
5) axial reduction
6) finishing and evaluation

60

What should the final crown prep provide?

-maximum conservation of tooth structure
-ideal resistance form
-ideal retention form
-structural durability

61

Why are retention and resistance interrelated and inseparable qualities?

-occlusogingival length: factor of retention and resistance!
* greater the surface area of the prep, the greater its retention and resistance
* surface area can be increased by adding boxes and grooves
- the shorter the wall the more important is the convergence angle, shorter preps need as little taper as possible to increase resistance and retention
-long, parallel axial walls and grooves = good retention and resistance
-short, overtapered prep = restoration easy to remove, less retention and resistance

62

What is structural durability?

- the restoration must have sufficient bulk to resist distortion and allow for wear during service.
- an unnecessarily thick casting is indicative of excessive tooth prep

63

What features provide retention and resistance on a full veneer crown?

axial reduction and retentive groove, length, and taper

64

What features provide structural durability on a full veneer crown?

functional cusp bevel, occlusal reduction and adequate length

65

How to place occlusal guide grooves on tooth # 30?

- keep bur at 0.8 mm by following the anatomical contours of the occlusal surface
- depth grooves should be 0.2 mm shallower than intended tooth reduction to allow for finishing and smoothing
-place depth grooves at height of each triangular ridge and in buccal and lingual
-should be 1.3 mm on buccal (functional) cusp and 0.8 mm on lingual cusps.
- don't place any grooves on distal cusp - leave it alone
-the mesiolingual groove could run at a little angulation
-the grooves placed at the triangular ridges and at the medial and distal fossa grooves should be parallel with each other - even if they don't run with the actual grooves
-also place depth grooves for the functional cusp bevel

66

How to do occlusal reduction on # 30?

- use 242.6 M to remove tooth structure remaining between the depth grooves.
-tooth should be reduced in planes that correspond to the anatomical feature of the unprepared tooth
-occlusal surface should be reduced In two steps
- make sure there isn't a ridge at the central groove
-functional cusp bevel should be approximately 45 deg to the POW of the tooth
* approximately 2 to 3 mm wide (not less than 1.4 than axial wall length)

67

How to place the axial guiding grooves on # 30?

- place 3 grooves in buccal and lingual axial walls (one in center and one at each medial and distal line angle)
-these grooves determine the POW of restoration which should be in the long axis of the tooth
-mand molars generally have a lingual inclination
-when placing grooves, shank of diamond must be held parallel to POW
- use cervical 1/3 of crown to determine the long axis and POW
- the POW for a full veneer crown on posterior teeth in normal alignment parallels the long axis of the tooth
* if the tooth is tipped, the correct POW should be perpendicular to occlusal seating of the crown

68

How to do axial reduction of # 30?

-mark gingival extent of prep
-chamfer should be placed as far supragingivally as possible but axial walls need to have sufficient length for resistance and retention
-on the typodont, the buccal and lingual cavosurface line angle 0. 5mm occlusal to the plastic gingiva
-allowance (keep 0.25 mm above the actual chamfer - so ~0.75 mm from the gingiva) will have to be made for finishing
-interproximally, prep must extend cervically to contact area to provide 0.5 mm clearance with adjacent tooth - so will give sufficient space for impression material
- w/ 242.6 remove remaining islands of tooth structure between axial grooves
-hemispherical tip of diamond bur creates the chamfer
- the chamfer should be slightly narrower than its eventual width of 0.5mm (allowance for finishing)
-interproximal areas can be removed with 747.6M

69

How to evaluate crown preps?

-check inclination of axial walls
-convergence should be same as diamond
-check for undercuts
-center of occlusal surface of the prep is viewed with 1 eye from 12'' away
-binocular vision should be avoid ( use only one eye to evaluate)
-evaluate chamfer for width and smoothness
* a consistent width of 0.5mm combined with POW in tooth's long axis will give adequate axial reduction, but maybe a non-functional cusp bevel maybe required

70

how to finish crown preps?

-chamfer and axial walls are finished with 242.6M
-ripples or corrugations in axial walls should be smoothed
-use minimum air pressure to rotate bur at minimum speed
-don't create chamfer of irregular width
-make sure there is an obtuse cavosurface angle (no sharp lip of enamel)
-prep should exhibit an over-smoothness, a surface with light striations
- polished surface is unacceptable
-cavosurface angle should be slightly greater than 90 deg.
-if lingual surface of tooth has pronounce contour, non-functional cusp should be beveled to allow adequate bulk of metal at the linguo-occlusal line angle.
-round all line angle because wetting is improved - but not excessively or resistance form will be lost

71

What are the principles of parallelism?

-occlusal reductions must not be even
-axial walls must be long
-parallel axial walls will allow crowns to fit
-convergent axial walls will be the easiest to place the crown
divergent axial walls are undercut and the crown WILL NOT fit
- you want a slight convergent taper of the walls
* opposing walls should have 3 deg taper
* total convergence angle should be 6 deg
* don't want to go past 12:01

72

How to place occlusal guide grooves for # 29?

- place depth grooves at height of buccal and mesiolingual triangular ridges and in the medial and distal fossa grooves of the buccal and mesiolingual fossa groove and lingual groove
-grooves should be placed 0.8 mm deep except over the functional (buccal) cusps

73

How to do occlusal reduction for # 29?

-remove islands between grooves
-cusps and slopes should slope at the same angle on the peeped tooth as the original unprepared occlusal surface
- the functional (buccal) cusp is beveled at approximately 45 deg.

74

How to place axial guide grooves for # 29?

- place 3 shallow grooves in buccal and lingual axial walls (one mid-buccal/lingual, one mesio-buccal/lingual line angle and one distobuccolingual line angle)
-mand premolars generally incline to lingual

75

How to do axial reduction and evaluation for #29?

-buccal and lingual margin should be 0.5mm occlusal to gingival and 0.5 mm clearance with adjacent tooth
- for interproximal removal - can use the extra thing 855-012 diamond to remove it
- for evaluation: if non-functional cusp bevel is needed , there should be a minimum of 0.6mm reduction at the linguo-occlusal line angle
***** #29/20 crown prep are the same

76

How to place occlusal guide grooves for #3?

-place depth grooves at height of each triangular ridges and in mesiobuccal and distobuccal fossa grooves and mesiolingual and distal oblique groove,
- these should be 0.8mm deep except over the functional (lingual) cusp - which will be 1.3 mm.
-also place the functional cusp bevel

77

How to do occlusal reduction for # 3?

-remove islands
-make sure the relative location of cusp tips, triangular ridges and central grooves are unaltered.
-the functional cusp bevel should be approximately 45 deg to long axis of tooth

78

How to place axial guide grooves for #3?

- place 3 shallow guiding grooves in buccal and lingual axial walls (one mid-buccal/lingual, one mesio-buccal/lingual line angle, and one distortion-buccal/lingual line angel).
-max molars generally incline to buccal

79

how to do axial reduction and finishing for #3?

-buccal and lingual margin should be .5mm occlusal to gingiva and 0.5 clearance from adjacent tooth
- can use the extra thin L-242.6M diamond to remove the inter proximal area
-the contour of the buccal surface of max posterior teeth has 2 planes - the buccal first plane from gingival crest to about the junction of the middle and occlusal third of the tooth and the buccal second place from this junction to the occlusal edge.
-the buccal first plane establishes the path of withdrawal of the crown and provides space for the restoration metal.
-the buccal second plane is reduced to provide sufficient space for restoration metal and restore the tooth to it's original contour.
-hold the bur parallel to the occlusal 2/3 of the buccal surface of tooth #2. keeping this angulation, carry the handpiece and bur to tooth #3 and reduce the buccal tooth structure to create the buccal second plane reduction.
-the buccal second plane should be parallel to the original tooth surface and is generally the occlusal 1/3 - 1/2 of the buccal axial wall of the prep.
* it isn't carried inter proximally which would over converge the occlusal 1/3 of the medial and distal proximal axial walls.
* the buccal second plane reduction should be 1.0 mm
- the second plane is use on max molars and premolars
-evaluate need for a non-functional cusp bevel and second plane of buccal reduction - there should be a minimum of 0.6 mm reduction at the bucco-occlusal line angle.

80

How to place occlusal guiding grooves for #13?

*** mostly same as #3
-place grooves at height of each triangular ridge, and in medial and distal fossa grooves. should be 1.3 mm deep
-also place depth grooves for functional cusp bevel

81

How to do occlusal reduction for #13?

-remove islands
-functional cusp bevel should be 45 deg to long axis of the tooth

82

How to place axial guide grooves for #13?

-place 3 guide grooves (0.8mm) in buccal axial wall and 3 in lingual axial walls (one mid-buccal/lingual, one mesio-buccal/lingual line angle and one distortion-buccal/lingual line angle)

83

How to do axial reduction for #13?

- clearance is 0.5 mm to adjacent tooth
-when creating the chamfer - it should be slightly narrower than its final 1 mm width and slightly occlusal to the pencil line for later refinement.
- use extra thing L-242.6 M to remove inter proximal
** has the same second plane reduction like #3
- hold the bur parallel to the occlusal 2/3 of the buccal surface of tooth #12. keeping this angulation, carry the handpiece and bur to tooth #13 and reduce the buccal tooth structure to create the buccal second plane reduction.
-the buccal second plane should be parallel to the original tooth surface and is generally the occlusal 1/3 - 1/2 of the buccal axial wall of the prep.
* it isn't carried inter proximally which would over converge the occlusal 1/3 of the medial and distal proximal axial walls.
- the second plane is use on max molars and premolars
-evaluate need for a non-functional cusp bevel and second plane of buccal reduction - there should be a minimum of 1.0 mm reduction at the bucco-occlusal line angle.

84

What are the measurements for #13

functional cusp: ideal
reduction central: 1.5 mm
non-functional cusp reduction: 1.5 mm
POW: +- 5 deg of long axis
convergence (w/ angle): 6 deg. (5-10 deg)
chamfer width: 1 mm
inter proximal chamfer placement: 0.5 mm
linguo-occlusal line angle: 1.3 mm
buccal second plane reduction (parallel to the original tooth surface): 1.3-1.5 mm