Tooth crazing associated with threaded pins: A three-dimensional model

A model for observing the three-dimensional pattern of cracking associated with placement of self-threading retentive pins was developed. Four sizes of selfthreading pins were placed in extracted posterior tooth samples. The pins were subsequently removed and the samples coated with butyl acetate lacquer except for the pin channel orifice. Samples were immersed in dye solution followed by a demineralization and dehydration process. Samples were placed in methyl salicylate until cleared. Cleared samples were examined for dye penetration into the pin channel and communication with the pulp chamber. Comparisons were made of the patterns created by the four sizes of retentive pins. Results showed that more extensive cracks occurred with the larger size pins and that crack communication with the pulp chamber occurred more frequently with the larger pins.