Comparative Study Of Two Different Measures On Improved Retention Of Full Crowns On Short Teeth Abutments

Objective: To observe the retentive strength of full metal crowns on short teeth abutment with axial grooves and boxesMethod: 30 extracted human molars were uniformly prepared (14° taper, 3 mm axial length). Those 30 short teeth abutments were randomly divided into three groups which has 10. Then prepared the short teeth abutments in Group 1 with axial grooves; in group 2 with boxes; Group 3 was control group. Wax patterns of full crowns were fabricated, invested and cast in a Ni-Cr cast alloy. The cast crowns were cemented on abutments with zpc respectively. Retentive strength was determined by measuring the tensile force required to remove the full crown from the abutment at crosshead speed of 1 .0mm/min on a universal testing machine.Result: The retentive strength of crowns cemented on abutments in Group 1, Group 2, and Group 3 were 310.57 ± 33.08N, 334.28 ± 29.48N and 248.98 ± 32.42 N. T-test analysis displayed significant statistical difference between Group 1 and Group 3, and between Group 2 and Group 3. And there was no significant statistical difference between Group 1 and Group 2.Conclusion: For full crowns of short teeth abutments, the grooves or the boxes could be improve retentive strength of full crowns.