2. Its use is based on the premise that an intact surface of
tooth structure should not be covered by a crown if it is not
essential to the retention, strength or esthetic of
restoration.
Appearance of enamel
Gingival health (supragingival margins)
Pulpal problem (2.5 times)
3. Tooth structure is spared
Much of margin is accessible to dentist and patient
Reducing the possibility of periodontal irritation
Easily seated in cementation (hydraulic cylinder)
Seating is more easily verified
Electric pulp test
5. Not as retentive as full crown
Just used for single restoration or retainers for short-
span FPDs.
Preparation feature used to compensate lost retention
& resistance.
Commonly used feature is groove
6. Retention
Less than full crown
Adequate for single crown
Adequate for Short-span FPD
Features like Groove
7.
8. Commonly used partial coverage
If designed skillfully can be very esthetic:
Conversational esthetics (moderate & reasonable
demands)
9.
10.
11.
12.
13.
14. Esthetic demands and ease of preparation have led to
near-total demise of anterior ¾ crown.
1. Short span
2. Caries
Path of insertion: incisal ½ to 2/3
15.
16.
17.
18. One of the disadvantages of conventional FPDs is
tooth structure destruction even in partial coverage.
Inlay retainers
Acrylic resin pontics
Resin bonded FPD
19. Rochette bridge: (Mechanical Retention)
Funnel shape perforation
1. Weakening of the metal retainer by the perforations.
2. Exposure to wear of the resin at the perforations.
3. Limited adhesion of the metal provided by the perforations
20. Maryland bridge: (Micromechanical Retention)
Electrochemical pit corroding tech.
Technique sensitive
Overetching: electropolished surface
Chemical etching
Air abrasion combined with silane
21. Virginia bridge (lost salt tech.):
Incorporating salt crystals into the retainer patterns,
leave cubic voids
0.5 – 1 mm crystal-free margin
22. Unfilled resin (Rochette)
Unfilled/filled composite resin
Chemically active (adhesive) resin: 4-MTE , MDP
Rely on adhesion to metal (not microretention)
Etching was no longer necessary
Air abrasion with small particle for cleaning
Tin plating for noble metal
30. Rubberdam
The casting:
Air abrasion of retainers: 2-3 s per cm2, 60-100 psi
Casting is washed:
Running water : 1 min
Ultrasonic unit: 2 min
Tin plating(if noble metal): 5-10 s, 0.5 um
Casting is rinsed: 2 min
Blown dry
31. The teeth:
Pumice and rubber prophy cup
Pumice is washed
40_50 % phosphoric acid : 60 s
Rinse and dry
40_50 % phosphoric acid is reapplied: 15 s
Rinse and dry: 20s
Mylar strip is placed
32. ED primer is mixed and applied on the preparation: 60s
Pastes are mixed and applied on the retainers (not on the abutments)
Oxyguard II on the margins: 3 min