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post and core Flashcards

1
Q

In compromised coronal portion

A

Orthodontic crown extrusion is better that Surgical crown lengthening

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2
Q

Central incisors with round cross section prepared with

A

twist drill or reamer to provide parallel walls or minimal taper

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3
Q

canals with elliptical cross-sections must be prepared with

A

Restricted amount of taper 6-8 for adequate retention and minimal undercuts

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4
Q

optimum ratio of the post to the crown

A

3/2

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5
Q

post length …. final crown

A

1.5

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6
Q

in short roots minimum root filling is left?

A

3-5 mm

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7
Q

Talk about Bonded non metallic posts..

A

They tend to distribute functional stresses over wide inter radicular surfaces which leads to less possibility of root fracture.

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8
Q

Greatest stress concentration found at

A

the shoulder inter-proximally and at the apex, Dentin should be conserved at those areas

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9
Q

Cast metal transmits forces applied to…

A

Fulcrum areas and the tip of the apical tip of the post

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10
Q

Rotation is prevented by

A
  1. the vertical coronal wall
  2. small groove in the bulkiest area
  3. pin or pins
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11
Q

Six Key Features of Successful design for Preparation to receive A Post and Core

A

1} Adequate apical seal (3-5m gutta percha)
2} Adequate post length
3} Minimum Canal enlargement
4} Positive horizontal stop
5} Rotational resistance
6} Ferrule (> 1.5 mm vertical tooth structure)

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12
Q

Fabrication of a post and core steps

A
  1. canal preparation
  2. Resin pattern fabrication
  3. Finishing and cementation of the dowel core
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13
Q

How to remove Gutta-percha?

A
  1. Warmed endodontic plugger
  2. Rotary as peso or Gates
  3. Rotary with chemical agent
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14
Q

How to avoid small concavities in the post wall space?

A

By using cylindrically shaped peso-reamers

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15
Q

extreme taper or non circular canals we use

A

custom made posts

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16
Q

What is the most common cause of endodontic failure?

A

Coronal microleakage

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17
Q

What reduces microleakage?

A

reliable interim prosthesis

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18
Q

Venting

A

مجرىgroove بطول post بتسمح بهروب excess cement

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19
Q

Dis of cast metal posts

A

1- inferior aesthetics because they do not allow light transmission
2- The risks that metal posts might corrode, causing gingival and tooth discoloration.
3-Trigger allergic reactions
4-Offer less retention
5-Might lead to serious types of root fracture
6-low resilience and do not match the elastic modulus of the tooth structure

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20
Q

☻ The advantages of GFPS are

A

1- Retrievable after failure

2- Less likely to cause vertical root fractures than stainless steel posts.

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21
Q

Clinical failures of the restored endodontically treated tooth

A

1- Loss of retention of the extra coronal restoration, the core build-up and /or the post.
2- Fracture of the superstructure, the core/post and the remaining tooth structure.
3- Perforation in the root.
4- Microleakage of the cemented posts.

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22
Q

• Changes in endodontically treated teeth 1) Loss of tooth structure;

A

-The strength of the tooth is decreased
-The tooth is liable fracture under normal functional forces
-The (MOD) preparation reduces stiffness of the tooth by 60%.
-Endodontic access destroys the structural integrity provided by the coronal dentin of and allows greater flexing of the tooth under function.
The fracture resistance of the endodontically treated tooth decreases with a decrease in residual dentin and the strength of tاe restored tooth is directly related to the remaining bulk of dentin

23
Q

2) Altered physical characteristics;

A

a- Changes in the cross-linking of collagen. b- Loss of moisture which results in dehydration of dentin. Dehydration of tooth brittleness

24
Q

The dentin of human pulp less teeth has less ….. than that of normal teeth.

A

crushing strength

25
Q

There is …… less moisture in the calcified tissues of pulp less teeth than in the calcified tissues of vital teeth.

A

5 - 9 %

26
Q

The effect of dehydration on the dentinal tubules bas been associated with

A

increased weakness and brittleness in pulp less teeth.

27
Q

The need for a full coverage restoration after endodontic therapy is largely determined by

A

1-Tooth type,
2-Amount of tooth structure loss,
and 3- The amount of occlusal stress on the tooth.

28
Q

has all four axial walls remaining and only the access preparation involves removal of tooth structure.

A

Class I

29
Q

has onc cavity wall removed, which can consist of a mesio-occlusal or a disto-occlusal cavity.

A

Class II

30
Q

a MOD cavity and two remaining cavity walls are present.

A

In Class III,

31
Q

has only one cavity wall remaining (either the buccal or lingual wall).

A

Class IV

32
Q

no cavity wall remains. This classification is useful in determining the need for a post.

A

Class V,

33
Q

•Before restoration, existing endodontically treated teeth need to be assessed carefully for the following’:

A 
1-Good apical seal 
2-No sensitivity to pressure 
3-No exudate 
4-No fistula 
5-No apical sensitivity 
6-No active inflammation
34
Q

Endodontically treated anterior teeth do not always need complete coverage by placement of a complete crown, except when

A

plastic restorative materials have limited prognosis (e-g, if the tooth has large proximal composite restorations and unsupported tooth structure).

35
Q

•Anterior teeth that are farther removed from the fulcrum axis.

A
  1. Anterior teeth intact with small access, no need for post and in some cases a simple restoration is sufficient.
  2. In case of anterior teeth with small proximal restorations can be restored with lingual resin restorations.
    3- In anterior teeth, full coverage may only be necessary when there is significant loss of tooth structure for esthetic reasons.
    4- Anterior teeth with large access wide coronal flaring, a cast post and core or prefabricated esthetic post is required.
36
Q

•Disadvantages to the Routine Use of a Cemented Post

A

1- Placing the post requires an additional operative procedure.
2- Preparing a tooth to accommodate the post entails removal of additional tooth structure.
3- It may be difficult to restore the tooth later, when a complete crown is needed, because the cemented post may have failed to provide adequate retention for the core material.
4-The post can complicate or prevent future endodontic re- treatment that may be necessary

37
Q

endodontically treated posterior tooth should receive

A

cuspal coverage.(onlay)

38
Q

use of a post in the root canals for retention is not necessary”.”When

A

more than 3 to 4 mm of coronal tooth structure with reasonable wall thickness remains,

39
Q

Minimally destructed teeth

A

Intracoronal composite

resin restoration

40
Q

Moderately destructed teeth

A

Overlay (preparation design will depend on the clinical situation)

41
Q

Severely destructed teeth

A
  1. Fiber post-core-crown

2. Endocrown

42
Q

Modifying factors:

A
  1. Parafunctional habits
  2. Lateral occlusal forces
  3. Less than 2 pronimal contacts
43
Q

1- According to The Material:

A

1- All Metallic
2- Combination of Metal and Non-Metal: This type could be either: - Metallic post crown with non-metallic veneer. - The post constructed from metal and the core from non-metal
3- All Non-metallic: recently introduced, such as zirconium oxide ceramic posts, and carbon fiber glass fiber posts.

44
Q

The majority of the prefabricated posts are designed to be

A

matched with a special drills or endodontic files for root canal preparation before post insertion.

45
Q
  • Classification of prefabricated posts.
A 
A-Tapered, smooth-sided posts. 
B- Tapered, serrated posts. 
C- Tapered, threaded posts. 
D- Parallel, smooth-sided posts. 
E- Parallel, serrated posts. 
F- Parallel, threaded posts.
46
Q

2- According to Post design.

A

A. Passive/ Smooth’Tapered Posts (A) Less preparation. Less stress. But less retention.
B. Passive/Smooth Parallel Posts (D) More preparation Provide the most equitable distribution of masticatory forces.
C. Active Posts/Threaded post (C, F) severe apical stress levels

47
Q

The thickness of the remaining dentin is the prime variable in

A

fracture resistance of the root.

48
Q

Enlargement seldom needs to exceed with

A

one or two additional file sizes beyond the largest size used for endodontic treatment coronally.

49
Q

Ferrule

A

♠ 360° collar of crown surrounding the parallel wall of dentin extending to the margin of the preparation.
- It is the extention of the final restoration (crown) margin onto sound tooth structure
♠ A ferrule helps binding the remaining tooth structure together, which prevent root fracture during function.

50
Q

♠ The length of the prepared root canal should be ….. of the root length but never be less than the length of the occluso-gingival height of the ……

A 
2/3
tooth crown (1:1 ratio)
51
Q

Post diameter should not be greater than

A

one-third of the root at the cementum–enamel junction.

52
Q

the cast metal post transmits about ….. of all forces that are applied to it to the fulcrum areas and the apical tip of the post.

A

88%

53
Q

The keyway should be cut to the depth of

A

the diameter of the bur (approximately 0.6 mm) and up the canal to the length of the cutting blades of the bur (approximately 4 mm).

Fixed (4 decks)

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