Fixed Partial Dentures and Pontic Design

Question 1

Which component of the Fixed Partial Denture will fit onto the abutments?

Answer 1

the retainers

Question 2

Which component of the Fixed Partial Denture will fit over the edentulous area?

Answer 2

the pontic

Question 3

How does the pontic attach to the retainers?

Answer 3

through the “connectors”

Question 4

What are two major contraindications to an FPD?

Answer 4

1. Excessive edentulous span

2. Weak abutment teeth

Question 5

Ante’s Law states that the peri-cemental area of the abutment teeth must be _______ the peri-cemental area of the pontic.

Answer 5

greater than or equal to

Question 6

What is the effect of length (edentulous area) on deflection of the FPD?

Answer 6

Deflection = length cubed
2x length = 8x deflection
3x length = 27x deflection

Question 7

What is the effect of “connector thickness/height” on deflection of the FPD?

Answer 7

Increased connector thickness/height results in decreased deflection. D= (1/H)^3
example: 1/2 thickness = 8x deflection

Question 8

What is the danger of having three pontics between two abutments?

Answer 8

with heavy occlusal loads the metal will flex and the porcelain will chip

Question 9

What are three considerations for abutment selection?

Answer 9

1. Clinical crown-to-root ratio
2. Root form
3. Tooth angulation

Question 10

What is the MINIMUM amount of bone (crown-to-root ratio) that is acceptable as an abutment?

Answer 10

1:1

Question 11

What is the IDEAL crown-to-root ratio (amount of bone) that is acceptable as an abutment?

Answer 11

2:3

Question 12

True or False: If the clinical crown-to-root ratio is greater than one, the FPD will fail.

Answer 12

True, minimum required bone is a ratio of 1:1

Question 13

When selecting abutments, what is the importance of “root surface area?”

Answer 13

Root surface area = periodontal support

*Certain teeth have a better cross-sectional configuration for support of the partial

Question 14

Which teeth have a root surface area (cross-sectional configuration) that is NOT well suited for use as abutments?

Answer 14

Lateral incisors (uniform and ovoid shape)

Question 15

The root design for abutment teeth will influence stability of the partial. Which is stronger: curved or straight roots?

Answer 15

Curved

Question 16

The root design for abutment teeth will influence stability of the partial. Which is stronger: convergent or divergent roots?

Answer 16

Divergent

Question 17

Why are “curved” and “divergent” roots preferred over “straight” and “convergent” roots for abutment teeth?

Answer 17

Curved/Divergent provides greater root surface area

Root Surface Area = Periodontal Support

Question 18

What happens if the connector size is sacrificed for esthetics?

Answer 18

The connector will break

Question 19

What are the boundaries within which esthetics may be considered more than strength?

Answer 19

Anterior…or where ever the client thinks it is important

Question 20

Why must you check the tooth preparations from all different angles?

Answer 20

Because there may be an undercut within one prep, between the two preps, or both

Question 21

What are three options for preparing abutment teeth that have different long axes?

Answer 21

1. Reposition teeth prior to FPD: orthodontics
2. Use intracoronal attachments
3. Conservative removal of offending proximal contacts

Question 22

What are precision attachments? Common type?

Answer 22

-Fixed attachments that provide retention and/or support in the case that abutments are not parallel; therefore, there is a contraindication for FPD
Key-Way attachments: “female and male parts” that connect together

Question 23

If removal of proximal contact is necessary when preparing abutment teeth (due to different long axes), what must be considered for the proximal teeth?

Answer 23

PULP HORNS: careful, patient’s age?

Question 24

What are the three general considerations when evaluating the edentulous area for a pontic?

Answer 24

1. Mesio-distal width
2. Occlusocervical distance
3. Bucco-lingual diameter of remaining alveolar ridge

Question 25

_____ _____ _____ has most likely occurred in the edentulous area if a tooth were extracted several years prior.

Answer 25

Buccal Plate Resorption

Question 26

Why would buccal plate resorption cause an issue for the FPD?

Answer 26

The ridge thickness B-L would most likely be uneven and would cause the pontic to lean toward the recessed area.

Question 27

If vast amounts of resorption occurred, an edentulous ridge can be prepared for the FPD by use of a ______.

Answer 27

Graft

Question 28

If cervical lines are uneven (ex. one tooth appears pushed in), how can the arch be restored to a more even contour?

Answer 28

Orthodontics (erupt that tooth)

Question 29

Why would you use orthodontics prior to extracting a tooth?

Answer 29

Ortho can be utilized in order to erupt teeth and pull BONE down prior to extractions. This will prevent serious resorption of the edentulous area.

Question 30

What are the six common pontic forms?

Answer 30

1. Ridge Lap (saddle) 2. Modified Ridge Lap 3. Hygienic (sanitary) 4. Modified hygienic 5. Bullet 6. Ovate

Question 31

What is a "ridge lap" pontic used for? Why is it not recommended?

Answer 31

* Eshthetics* - emulates the contours and emergence profile of the missing tooth * Difficult to clean* - mucosal surface follows the contours of the gingiva - formation of ulcers

Question 32

What is a hygienic pontic used for? What is its disadvantage? Advantage?

Answer 32

Use: Mandibular posterior teeth Disadvantage: No indication for maxillary teeth (shelf) Advantage: Easy plaque control

Question 33

The distance between the pontic mucosal surface and gingiva should be _____ mm.

Answer 33

1-2 (definitely not less than 1 mm, 1.5 mm is ideal)

Question 34

What would happen if the hygienic pontic was not 1-2 mm from the gingiva?

Answer 34

It would be too difficult to clean under, the mucosa would become severely inflamed.

Question 35

What is the difference between a "modified hygienic" and "hygienic" pontic?

Answer 35

Modified = wider connectors = stronger, less esthetic

Question 36

What is a "modified ridge lap" pontic design?

Answer 36

MOST COMMON design - Hygienic from the lingual - Saddle from the buccal

Question 37

What are the benefits of the modified ridge lap design?

Answer 37

Esthetic | Cleansible

Question 38

True or False: The modified ridge-lap design should have a tight T-shaped tissue contact on the lingual.

Answer 38

FALSE. the T-shaped contact should be on the buccal (the side with the saddle, not the hygienic) and contact should be very minimal.

Question 39

Where is a "bullet" pontic design used?

Answer 39

Mandibular molars with knife-edge alveolar ridges | -if the ridge is wide...use a hygienic or food will get impacted

Question 40

Of the two mandibular molar pontic designs, which one is in contact with the mucosa?

Answer 40

"Bullet" Pontics (knife edge ridges)

Question 41

An ______ pontic will most likely be used if it is placed at the time of extraction. It provides good emergence profile but is hard to clean underneath.

Answer 41

Ovate

Question 42

When using an ovate pontic, what must be done extremely well?

Answer 42

the pontic MUST be highly POLISHED...risk for tissue damage or ulceration due to extension into the open socket

Question 43

The ovate pontic eliminates the potential for _______ ______ in the cervical portion of an anterior pontic.

Answer 43

Unsupported Porcelain

Question 44

Which two pontic designs have no contact or slight mucosal contact?

Answer 44

``` Hygienic (none) Modified Hygienic (slight) ```

Question 45

If using a cantilever pontic (one connector), where should the pontic be in regards to the abutment?

Answer 45

MESIAL | distal cantilever causes unfavorable load on abutment

Question 46

What is the best indication for a cantilever pontic? Why?

Answer 46

Missing lateral incisors | -the canine can be used as an abutment, leaving the central incisor un-prepared

Question 47

(Biological Consideration) ______-_______ contact between the pontic and underlying tissues is indicated to prevent ulceration and inflammation of soft tissue.

Answer 47

Pressure-free

Question 48

In the _____ region, a pontic should contact the gingival tissue.

Answer 48

anterior (appearance of emergence from soft tissue)

Question 49

(Biological Consideration) | To enhance hygiene, what must the patient be instructed to do?

Answer 49

Perform efficient plaque control and prevention

Question 50

What is a "pier abutment"?

Answer 50

Two edentulous ridges are separated by a tooth that can be prepped and made into an abutment (pier). Therefore, there are three abutment teeth and two ridges. 1110____0____0111

Question 51

What is the alternative to having a pier abutment? Why would this be chosen instead?

Answer 51

1. Non-rigid connector (connects two separate pieces) -if common POW is too difficult to create 2. Cantilever one of the pontics -prevents preparation of three teeth 11111___0___0111

Question 52

The pontic design should be of ______ form for #20 and of _________ form for #4.

Answer 52

Hygienic #20 (mandibular) | Modified Ridge Lap #4 (maxillary)