Bridgework 3

Question 1

evaluation of potential abutments

Answer 1

• root configuration
• angulation / rotation of abutment
• periodontal health
• surface area for bonding & quality of enamel
• risk of pulpal damage
• quality of endo tx i.e. re RCT if needed
• remaining tooth structure present
• if core consider remove & rebuild

Question 2

different types of pontic

Answer 2

1. wash through pontic
2. dome pontic (bullet shaped)
3. modified ridge lap pontic
4. ridge lap pontic (full saddle)
5. ovate pontic

Question 3

pontic function (3)

Answer 3

1. restore appearance of missing tooth
2. stabilise occlusion
3. improve masticatory function

Question 4

pontic design (3)

Answer 4

1. cleanability - should always be smooth with highly polished or glazed surface, surface should not harbour join of metal & porcelain (if MCC design used), ensure embrasure space smooth & cleansable
2. appearance - anteriorly should be as tooth like as possible and posteriorly can compromise
3. strength - longer the span the greater the thickness required to withstand occlusal forces

Question 5

surfaces of the pontic

Answer 5

occlusal - should resemble surface of tooth it replaces, narrower if possible to enable cleaning, should have sufficient occlusal contact
approximal surface - connector : strength, embrasure space
buccal & lingual surface
ridge surface (one of the 5 pontic designs)

Question 6

wash through pontic design

Answer 6

makes no contact with soft tissue
functional rather than for appearance
consider in lower molar area
hygienic / sanitary

Question 7

dome shaped pontic

Answer 7

useful in lower incisor, premolar or upper molar areas
acceptable if occlusal 2/3 of buccal surface visible
poor aesthetics if gingival 1/3 of tooth visible

Question 8

modified ridge lap pontic

Answer 8

buccal surface looks as much like tooth as possible
lingual surface cut away
line contact with with buccal of ridge
problems with food packing on lingual surface of ridge

Question 9

ridge lap pontic (full saddle)

Answer 9

greatest contact with soft tissue
if designed carefully can be cleaned
less food packing than modified ridge lap
care taken not to displace soft tissue or cause blanching

Question 10

materials used for conventional bridges

Answer 10

all metal - gold / Ni or CoCr / stainless steel
metal ceramic
all ceramic - zirconia e.g. LAVA & Procera, lithium disilicate e.g. Emax
ceromeric - BelleGlass, Vectris, Targis Vectris

Question 11

all metal crowns

Answer 11

gold / Ni or CoCr / stainless steel
gold especially in lower posterior areas

Question 12

metal ceramic crowns

Answer 12

majority of bridges constructed in these materials in UK atm

Question 13

zirconia

Answer 13

prep on cast can be scanned then milled +/- a feldspathic porcelain on top
LAVA 3M ESPE 3-4 unit fixed bridge (max span) milled zirconium oxide frame with feldspathic porcelain overlying
can withstand occlusal forces, good aesthetics, similar reduction to MCC

Question 14

step 1 of conventional bridge work

Answer 14

mounted study models
consider diagnostic wax up & custom impression tray
request lab to construct vacuum formed stent

Question 15

why request vacuum formed stent at step 1

Answer 15

1. allows checking of reduction during tooth prep
2. allows construction of provisional bridge

Question 16

step 2 of bridge work

Answer 16

select shade
lab made stent / make pre op putty imp for provisional bridge
occlusal / incisal reduction
separation of teeth
aim for parallelism of tapered surface of each prep
prep each mesial then each distal etc

Question 17

parallelism

Answer 17

consider for FF conventional bridge
requires 2 or more teeth to be prepared in a manner to provide a common path of insertion (increased retention); must have no undercuts
paralleling by eye:
- direct vision, 1 eye closed
- large mouth mirror posteriorly
- use of a straight right angle probe like a lab surveyor but in the mouth
paralleling extra orally:
- quick impression
- pour model
- use laboratory surveyor
- useful in long span multiple unit bridges

Question 18

step 3 of bridgework

Answer 18

confirm parallelism
consider retentive features if short clinical crown height or overtapered (slots / grooves)
construct provisional bridge
make impression & occlusal registration
temporarily cement provisional bridge
demonstrate cleaning with floss
write prescription for technician

Question 19

definitive cementation for all metal conventional bridgework & metal ceramic

Answer 19

aquacem - GI luting cement
relyx luting - RMGI luting cement

Question 20

definitive cementation for adhesive / resin bonded bridgework

Answer 20

panavia 21 - anaerobic dual cure resin cement with 10-MDP

Question 21

definitive bridgework for all ceramic

Answer 21

nexus kit - dual cure resin cement

Question 22

why not distal cantilevers

Answer 22

avoid if possible
concern that occlusal forces on pontic will produce leverage forces on abutment tooth causing it to tilt
may consider distal cantilever from premolar abutment if unopposed or if opposed only by a denture