Abstract

Aim:  The aim of this study was to investigate the influence of three different thicknesses of In-Ceram core on the load at fracture of all-ceramic crowns.

Methods and Materials:   Thirty standardized crown-shaped nickel-chromium alloy dies were fabricated using a milling machine. Twenty dies were prepared with a 1 mm shoulder for Groups A and B. The only difference in the ten dies used for Group C was a smaller 0.5 mm lingual shoulder. The thicknesses of In-Ceram were 0.5 mm, 1.5 mm, and 0.75 mm for Groups A, B, and C. All all-ceramic crowns were fabricated in accordance with the manufacturer’s instructions. After cementation of the crowns, their fracture resistance was tested with a universal testing machine. The load was directed to a point located 3 mm from the lingual aspect of the incisal edge at 30 degrees to the long axis of each specimen until catastrophic failure occurred.

Results:  The mean loads at fracture for Groups A, B, and C were 1117±388 N, 2083±385 N, and 1439±368 N, respectively. No statistically significant difference in load at fracture between Groups A and C was found (p>0.05). However, the differences were statistically significant between Groups A and B (p<0.001) and Groups B and C (p<0.001).

Conclusion:  Under the guidelines of this study, increasing the thickness of the In-Ceram core increased the fracture resistance of the all-ceramic crowns.

Clinical Significance:  The sufficient thickness of the In-Ceram core of all-ceramic crowns is an important factor in fracture resistance. Therefore, dental practitioners should be careful in patient selection; if the horizontal overlap of a tooth to be restored is too limited, then all-ceramic crowns may not be a feasible option.

Keywords:  All-Ceram, In-Ceram, porcelain, fracture load, crown fracture

Citation:  Gokce S, Celik-Bagci E, Turkyilmaz I. A Comparative in vitro Study of the Load at Fracture of All-ceramic Crowns with Various Thicknesses of In-Ceram Core. J Contemp Dent Pract 2008 May; (9)4:017-025.