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The effect of endodontic access preparation on the failure load of lithium disilicate glass-ceramic restorations. - PubMed - NCBI
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J Prosthet Dent. 2011 Nov;106(5):328-36. doi: 10.1016/S0022-3913(11)60139-X.

The effect of endodontic access preparation on the failure load of lithium disilicate glass-ceramic restorations.

Author information

1
Department of Restorative Dentistry, State University of New York at Buffalo, School of Dental Medicine, Buffalo, NY, USA. dqeblawi@live.com

Abstract

STATEMENT OF PROBLEM:

Endodontic access preparation through lithium disilicate ceramic restorations may damage the restoration and compromise its load-bearing capability.

PURPOSE:

The purpose of this in vitro research was to investigate the effect of simulated endodontic access preparation through lithium disilicate glass-ceramic restorations on their load to failure.

MATERIAL AND METHODS:

Sixty lithium disilicate glass-ceramic (IPS e.max CAD) complete-coverage restorations were milled and crystallized. Five coats of die relief were applied internally in the crown to provide a cement space approximately 60 μm in thickness. Composite resin dies were fabricated by backfilling each crown. The specimens were then stored at 37°C and 100% humidity for 30 days. The crowns with their respective dies were divided into 6 groups: Groups M-C, M-ZR, M-SC, and M-CRF were adhesively bonded with a resin cement (Multilink Implant), and Groups F-C and F-ZR were conventionally cemented with zinc phosphate cement (Fleck's). After storing all groups for 1 week, Groups M-C and F-C served as the intact controls for the 2 cementation techniques, while Groups M-ZR and F-ZR had an access prepared with a 126 μm grit-size diamond rotary instrument. For Groups M-SC and M-CRF, the endodontic access was prepared with 150 μm and 180 μm grit-size diamond rotary instruments, respectively. Access preparations were restored with composite resin. All specimens were stored at 37°C and 100% humidity for 1 week before they were loaded to failure with a universal loading apparatus (crosshead speed=1mm/min). The results were analyzed with a 1-way ANOVA followed by Tukey's HSD test (α=.05).

RESULTS:

The highest failure loads were achieved with Groups M-C (3316 N ±483) and M-ZR (3464 N ±645) Larger grit rotary instruments resulted in lower failure-loads in Groups M-SC (2915 N ±569) and M-CRF (2354 N ±476). Groups F-C (2242 N ±369) and F-ZR(1998 N ±448) had significantly lower failure loads than their adhesively bonded counterparts (P<.05). The use of 126 μm grit size did not significantly alter the failure loads of the restorations in either cementation technique.

CONCLUSIONS:

Adhesively bonded restorations sustained significantly higher loads to failure than those conventionally cemented. The use of a high efficiency, smaller-grit diamond rotary instrument for endodontic access preparation did not alter the load to failure of lithium disilicate restorations, regardless of the cement used. The use of a larger-grit rotary instrument did not improve the cutting efficiency and reduced the failure load of bonded restorations.

PMID:
22024183
DOI:
10.1016/S0022-3913(11)60139-X
[Indexed for MEDLINE]
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