crown

Question 1

Discomfort may be caused by:

Answer 1

1. Malocclusion or premature contact. (one of the main causes because the patient will feel pain on chewing)
2. An over-size or poorly positioned masticating area,with retention of food by pontics or retainers.
3. Torque produced from the seating of the bridge or from occlusion. (part of the bridge comes in premature contact with the opposing and part is out of occlusion)
4. Excessive pressure on the tissue. (closure of the embrasure)
5. Plus or minus contact area. (plus contact exerts pressure on the neighboring tooth, and minus contact causes food impaction)
6. Over protected or under protected gingival & ridge tissue.
7. Sensitive cervical area.
8. Thermal shock. (due to preparation without cooling for few seconds and intake of very hot drinks after preparation)
9. Certain intangible sources, usually relatively unimportant & easily rectified if diagnosed.

Question 2

A bridge become loose because of:

Answer 2

1. Deformation of the metal casting on the abutment.(long span bridge especially with weak metal)
2. Torque.
3. Technique of cementation.
4. Solubility of cement.
5. Caries.
6. Mobility of one or more abutment.
7. Lack of full occlusal coverage.
8. Insufficient retention in the abutment preparation.
9. Poor initial fit of the casting.

Question 3

Sensitivity of cervical margin causes

Answer 3

1. Overextended margin of temporary bridge.
2. During tissue retraction, if gingiva is too much retracted, giving rise to gingival recession and sensitivity.
3. The use of caustic materials during tissue retraction

Question 4

Causes of recurrence of caries:

Answer 4

1. Overextension of margins. (because if the crown is overextended under the finish line and gingival it will form an undercut and causes retention of food and recurrent caries)
2. Short casting.(open margin with exposed dentine which is more liable to caries than enamel.
3. Open margins.
4. Wear. (due to malfunction, bruxism or griding teeth with no function, also usage of soft material in crown is a factor)
5. A retainer becoming loose.
6. Pontic form that fills the embrasure.(it turns from a self-cleansing area to area of food impaction)
7. Poor oral hygiene.
8. Use of wrong type of retainer which will promote caries susceptibility.
9. Because temporary protection of the abutment uncovered the neck of the tooth by a prolonged or permanent displacement of the gingiva.

Question 5

• Open and underextended margins in restoration should be

Answer 5

remake.

Question 6

• Poor pontic form occurs in 3 cases

Answer 6

pontic encroach on the gingiva, pontic closes the embrasure or over-contoured pontic.

Question 7

Causes of pontic failure:

Answer 7

1. Faulty occlusion, in lateral excursions, which was not corrected when the bridge was placed.
2. An acrylic facing will wear and discolor quite rapidly.
3. Improper pontic ridge relation: if the pontic is of saddle type (convex, concave ridge relationship), food accumulation and inflammation of the gingiva as well as gingival recession occur.
4. Improper pontic contour: pontic pressing on the ridge if a cement particle entrapped between it and the ridge.
5. This may lead to bone resorption. So, instruct the patient to use dental floss.

Question 8

Loss of the supporting alveolar process may result from overloading due to:

Answer 8

1. Length of the span. (increasing the span length will cause more overload on the abutment teeth)
2. Size of the occlusal table. (with increasing the occlusal table, more trauma to abutment teeth will occur)
3. Embrasure form.
4. Contour of the retainers.
5. Too few abutment teeth.
6. Ab overextension of the cervical margin of the preparation which interferes with or traumatizes the peripheral attachment of the periodontal membrane.
7. In district band impression technique can also stimulate recession of the alveolar process.
   - Too much pressure exerted in taking the impression forcing the band beyond the attachment of the periodontal ligament & either cutting or tearing it.
   - The same things will happen if the band is not contoured to the proximal curvature of the gingival line.

Question 9

Causes of pulp degeneration:

Answer 9

1. Too rapid preparation of the Improper cooling during preparation.
2. Uncovered teeth exposed to saliva & irritation between visits.
3. Undiscovered Caries under a retainer even by a radiograph. (Marginal examination with a mirror & explorer is essential).

Question 10

Causes of bridge framework fracture:

Answer 10

1. Faulty solder joint or weak connectors.
2. Incorrect casting technique.
3. Overload on the metal due to the length of the span.

Question 11

Causes of veneer fracture:

Answer 11

1. If a shelf of porcelain left exposed to opposing surface or cusps & subjected to either leverage or spot contact.
2. Over rapid heating or cooling during glazing.

Question 12

Causes of loss of veneer:

Answer 12

1. Too little retention.
2. Badly designed metal protection.
3. Deformation of the protecting metal.
4. Malocclusion
5. Improper curing or fusing technique.

Question 13

Lack of metal protection of deformation of metal requires:

Answer 13

1. Equilibration.
2. Reduction of the forces from occlusion.
3. Change in the form of the occluding area.
4. Increased number of pin holes providing retention

Question 14

Failure to Seat

Answer 14

1. The abutment preparation may not be parallel.

2. Incorrect soldering or the relationship of the retainers may be altered during soldering.

Question 15

Loss of Function

Answer 15

• Loss of a tooth in the opposing arch without replacement

Question 16

Esthetic Failures

Answer 16

• It occurs at the time of cementation or subsequently.
• At the time of cementation:
  1. Color mismatch.
  2. Poor tooth contour.
  3. Poor marginal placement.
  4. Poor pontic-ridge relation.
  5. Porcelain fracture during cementation.

Question 17

Loss of Tissue Tone or Form

Answer 17

1. Pontic design.
2. Position & size of the joints.
3. Embrasure form.
4. Over contouring or under contouring of the retainers.
5. Maintenance of oral hygiene by the patient

Question 18

initial lesion

Answer 18

2-4 days

localized in sulcus (PMNLs are predominant )

Question 19

early lesion

Answer 19

4-7 days
more collagen fiber loss, increase stimulation of inflammatory and lymphoid cells (lymphocytes are predominant and retentions ridges)

Question 20

established

Answer 20

7-21 days.
more collagen fiber loss, increase stimulation of inflammatory and lymphoid cells + START OF ATTACHMENT LOSS

junctional epithelium begin to form pocket epithelium

Question 21

Predominant cell in established lesion

Answer 21

plasma cell

Question 22

Predominant cell in initial lesion

Answer 22

PMNLs

Question 23

Predominant cell in early lesion

Answer 23

lymphocytes

Question 24

regarding fit and adaptation of the crown margin, marginal gap should be …. for cementation

Answer 24

50 - 120 microns

Question 25

point contact causes

Answer 25

wedging of food | gingival inflammation

Question 26

deficient contact

Answer 26

wedging of food gingival inflammation recession and pocket formation bone loss which may lead to tooth loss

Question 27

tight contact

Answer 27

increase in forces on the tooth which will lead to adaptation either by crowding and change in tooth position of bone remodeling and resorption

Question 28

function on embrasures

Answer 28

1. protect the gingiva from food impaction 2. deflect the food 3. provide a spillway during mastication 4. allow proper oral hygiene measures

Question 29

over contouring buccal or lingual

Answer 29

accumulation of food in cervical third which cause gingival inflammation caries and periodontal problems

Question 30

undercontouring buccal or lingual

Answer 30

trauma to the gingiva which may lead to recesion and bone resorption

Question 31

canine guided occlusal scheme is necessary in

Answer 31

missing upper 1st premolar