Effect of Two Connector Designs on the Fracture Resistance of All-Ceramic Core Materials for Fixed Dental Prostheses: An In-Vitro Study

Abstract

Background: The aim of this study was to test the difference in fracture resistance of 3 ceramic core

materials used for simulated 3-unit all-ceramic FPDs with 2 fabrication techniques (lost-wax/heat-pressing

and CAD/CAM methods) and 2 connector designs (round and sharp).

Material and method: The present in vitro study was conducted in the Department of Prosthodontics and

Crown & Bridge, Subharti Dental College & Hospital, Meerut, Uttar Pradesh. For the purpose of this study,

3 all ceramic core materials were selected viz. Yittrium-tetragonal zirconia polycrystals, Milled Lithium

disilicate glass ceramic and Lost-wax/heat-pressed lithium disilicate glass ceramic. A total of 10 rectangular

bars of dimensions 30 mm (L) x 5 mm (W) x 5 mm (H) from each material were manufactured. Of these

10 bars, 5 bars were fabricated with sharp notch connector and 5 bars were fabricated with round notch

connector. The dimensions of all specimens were measured and verified individually by an electronic caliper

with an accuracy of 0.05 mm. The radius of each connector was measured with a measuring tool.

Results: The failure load was more in Press-R in comparison to Press-S and the difference was found to be

statistically significant. The FS was more in CAD-R in comparison to CAD-S and the difference was found

to be statistically significant.

Conclusion: The round connector design in yittrium stabilized zirconia and heat pressed lithium disilicate

both may be considered to be the all-ceramic core material of choice for FDP’s as they have highest failure

load and flexural strength.