Restoring a tooth which has extensively lost its crown is difficult. So use of pin restorations could be considered in such a case. In case a single tooth or a supporting abutment tooth, or both the abutments of a three unit or four unit bridge have to be given pin retention to support the cores of full coverage crowns, a rule of thumb of  'one pin per missing cusp' should be followed. It should be noted that pins reduce the compressive and tensile strength of amalgam. The three basic types of pin are- 1. Self threading pin or self shearing pin, 2. Friction lock pin, 3. cemented pin. Retention is more when self threading pins are used and it is least with the cemented pins. The pin site should be kept 1mm away from amelo-dentinal junction and clear of bi or trifurcation areas. If the pin perforates into pulp then placing CaOH in the pin hole and the vitality of the pulp could be monitored or else Root Canal Treatment (RCT) of the tooth be considered (The apical foramina is usually sited 0.5-0.7 mm away from the anatomical and radiographic apex. The apical constriction usually occurs 0.5-0.7mm short of the foramina. These distances increase with age due to deposition of secondary cementum. Root-filling to the constriction provides a natural stop to instrumentation, thus the working length should be established 1-2mm from the radiographic apex. Most canals are flattened mesio-distally, but become more rounded in the apical one third). After this follows the, use of post in the canal and core build-up to increase retention of the restoration. Occlusion should be checked while placing a pin and if needed bent inwards with a groove cut chisel. If pin perforates into PDL, then check its accessibility in gingival crevice to further smoothen off it, or extend cavity margin to include defect and care fully re-site pin, any which ways could be difficult.