Abstract

This study includes a comparative evaluation and a general conclusion about the best advisable crown length, taper and cement for maximal retention. One hundred and twenty extracted human maxillary premolar teeth with sound surfaces were selected using dial vernier calliper. Selected teeth were randomly divided into two different CO length groups (5 mm and 7 mm). Each group was randomly divided into 4 sub groups according different degree of taper of the axial wall (0o , 3o , 6o , 9o ). The crown preparations with different tapers were achieved by graduated customized device. Preparations were verified and crowns were cast with Co–Cr alloy; metal copings were luted with GIC, RMGIC and self adhesive resin cement. Retention was measured (MPa) by separating the metal crowns from the teeth under tension on a universal testing machine, data was recorded and statistically analyzed. Increasing the crown height from 5mm to 7mm, significantly increased the tensile bond strength of cast copings among all degrees of taper. Tensile bond strength in 0o taper was significantly higher than 3 o , 6o and 9o taper. Resin cement showed significantly higher retentive strength than GIC and RMGIC

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