Ch: 11 SHILINGBURG

Preparation for partial coverage crowns

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)

Tooth structure is spared Much of margin is accessible to dentist and

patientReducing the possibility of periodontal

irritationEasily seated in cementation (hydraulic

cylinder)Seating is more easily verifiedElectric pulp test

Advantages

Less retentionMetal displayDexterity of operation

Disadvantages

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

Retention Less than full crown

Adequate for single crown

Adequate for Short-span FPD

Features like Groove

Commonly used partial coverageIf designed skillfully can be very esthetic:

Conversational esthetics (moderate & reasonable demands)

Maxillary posterior 3/4

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

Anterior 3/4

One of the disadvantages of conventional

FPDs is tooth structure destruction even in

partial coverage.

Inlay retainers

Acrylic resin pontics

Resin bonded FPD

Resin_bonded FPD

Rochette bridge: (Mechanical Retention)

Funnel shape perforation1. 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

Maryland bridge: (Micromechanical Retention)Electrochemical pit corroding tech.Technique sensitiveOveretching: electropolished surface

Chemical etching Air abrasion combined with silane

Virginia bridge (lost salt tech.):

Incorporating salt crystals into the retainer

patterns, leave cubic voids

0.5 – 1 mm crystal-free margin

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

Resin cements:

Advantages:

1. Reduced cost

2. No anesthetic needed

3. Supragingival margins

4. Minimal tooth preparation

Disadvantages:

1. Irreversible

2. Longevity

3. No alignment correction

Indication:

1. Caries free abutment teeth

2. Mandibular incisor replacement

3. Maxillary incisor replacement

4. Periodontal splints

5. Single posterior tooth replacement

Contraindications:

1. Extensive caries

2. Nickel sensitivity: tin plated noble alloy can

be used

3. Deep vertical overbite

Axial reduction and guide plans

Slight extensions to facial surface (180 degree)

Finish line

Occlusal clearance

Vertical stops:

Countersink on incisors

Cingulum rest on canine

Occ. rest on posteriors

Tooth preparation:

0.5 mm, only on max. anterior teeth

• 1.5-2 mm from incisal edge• Just incisal to the occ. contact0.5 clearance

Flat notches or countersink

1 mm supragingival

Cingulum groove

Proximal groove

RubberdamThe casting:Air abrasion of retainers: 2-3 s per cm2, 60-

100 psiCasting is washed:

Running water : 1 minUltrasonic unit: 2 min

Tin plating(if noble metal): 5-10 s, 0.5 umCasting is rinsed: 2 minBlown dry

Delivery

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

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