Effect of die relief on the seating, fit and retention of cast gold crowns cemented on human teeth.

ABSTRACT

Die relief, by means of a paint-on die spacing material, is the most common method of achieving sufficient space between metal castings and tooth surfaces for cement to flow during seating. Several studies have determined the influence of cementing variables on crowns made for metal and plastic test dies. This study assessed the influence of die relief upon the seating and retention of cast gold crowns constructed for natural human teeth. Standard full crown preparations were made for 10 matched pairs of extracted human third molars, one each of which had been relieved with die spacer of approximately 40 microns thickness. Crowns were made by the indirect technique and were cemented with zinc phosphate cement in a static/dynamic jig. Seating behaviour and vertical discrepancies were measured electronically. Tensile bond strengths were determined in a universal testing machine. Results showed that die relief reduced vertical seating discrepancy associated with cementation by up to 79 microns. Differences between paired relieved and unrelieved samples were significant (p < 0.05). There were no statistically significant differences in tensile bond between paired relieved and unrelieved crowns.