Introduction
A pin-retained restoration is a large amalgam (less often composite) restoration held partly by small metal pins set into dentin. Pins are used when so much of the crown is lost – one or more cusps or whole walls – that the remaining tooth cannot give the restoration enough retention and resistance form. They solve a retention problem but put a metal foreign body into dentin, so the choice of pin and its risks matter as much as the indication.
Indications and contraindications
Pins are used only when slots, coves, grooves and bonding cannot give enough retention and resistance form. Large amalgams that replace one or more cusps are called complex amalgam restorations.
Indications
- Extensive loss of tooth structure: one or more cusps or axial walls missing, especially in short clinical crowns.
- Foundation (core build-up) for a crown in a vital tooth with too little dentin left to hold the core.
- Control (interim) restoration while the pulpal or periodontal prognosis is uncertain, or when a crown is not possible or affordable yet.
- Advantages over a crown or onlay: one visit, less tooth removed, low cost.
Contraindications
- Not enough dentin for a safe pinhole: thin walls, small teeth such as mandibular incisors, sites over root concavities and furcations.
- Endodontically treated teeth (relative): their dentin is more brittle, and the pulp chamber or a post gives retention instead.
- Cases where slots, coves, bonding or a cusp-covering cast restoration are enough.
- Anterior teeth under composite: the metal shows through as a grey shadow.