Retainers in Fixed Partial Dentures

Retainer: The part of Fixed Partial Denture which unites the abutment to the remainder of restoration.

Major retainers are those retainers which cover the entire occluding surface of the tooth. Eg. Full veneer crowns, partial veneer crowns. Minor retainers are small metallic extensions which are cemented on the tooth. Eg. Inlays, Onlays.

Types of Retainers

# Based on tooth coverage

1. Full veneer crowns
2. Partial veneer crowns
3. Conservative retainers

# Based on material being used

1. All metallic retainers
2. Metal ceramic retainers
3. All ceramic retainers
4. All acrylic retainers

# Based on Tooth coverage

1. Full Veneer Crowns: 

• They cover all five surfaces of abutment.
• They are fabricated like cap and are indicated for extensively damaged teeth.
• They are most retentive and ideal retainers.

2. Partial veneer crowns:

• They are preferred over full veneer crown because they require less tooth reduction.
• They are less retentive as compared to full veneer crowns.
• Pins can be fabricated to fit pin holes created on tooth for additional retention.

3. Conservative retainers

• They require minimal tooth reduction.
• They do not accept heavy occlusal load and are primarily indicated for anterior teeth.
• They have small metallic extension, which are designed to be luted directly onto lingual surface of abutment teeth using a resin cement.

# Based on Materials Being used

1. All metal retainers

• They are either partial or full veneer crowns.
• They require minimal tooth reduction.
• They are strong even on thing section.

2. Metal ceramic retainers

• They require more tooth reduction.
• They can be fabricated over entire full veneer crown or as facing over the labial/buccal surface of full veneer crown or over a partial veneer crown.

3. All Ceramic retainers

• They may be fabricated as partial veneer or full veneer crown.
• They require maximum tooth reduction because porcelain requires sufficient bilk for adequate strength.

4. All Acrylic retainers

• They are used for long term temporary fixed partial dentures.

Criteria for selecting Type of Retainers

*** Alignment of abutment teeth and retention: 

• If abutment teeth are aligned parallel to one another, a full veneer crown can be given. In such case, a fixed - fixed bridge is designed, because parallel alignment helps to provide single path of insertion.
• If abutment teeth are not aligned parallel to one another, common path of insertion is not possible. A fixed-fixed bridge is not designed. A pin retained crown can be given.

*** Appearance
It is best to retain the facial/buccal surface of natural teeth as they provide best esthetics.

*** Condition of abutment teeth
Partial veneer crowns are preferred for non carious abutments or abutments with large restoration but intact facial/buccal surface
Endodontically treated teeth may have to be restored with core post before designing retainer.

*** Cost
Metal ceramic crowns can be economically best replacement for both anterior teeth.

*** Preservation of tooth structure

Buccal/Facial face should be conserved.
Partial veneer crowns are more conservative than full crowns.
All ceramic crowns are least conservative.