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Title Lithium Disilicate Porcelain Is Weaker Than Zirconia When Comparing Fracture Toughness Of Dental Crowns
Clinical Question In a 40 year old patient, how does lithium disilicate porcelain compare to zirconia in fracture toughness of dental crowns?
Clinical Bottom Line When comparing fracture toughness of dental crowns, zirconia is stronger than lithium disilicate crowns. In all studies, zirconia exhibited a higher fracture load and flexural strength than lithium disilicate.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 11484570Tinschert/2001Three-unit FPDsIn vitro study
Key resultsFPDs of DC-Zirkon exhibited the highest fracture load (>2000N) while IPS Impress and In-Ceram Alumina showed the lowest failure load (<1000N). IPS Impress 2 and In Ceram Zirconia had intermediate failure loads, Mean value differences were “statistically significant.”
#2) 16001730Vult von Steyern/2005Two Clinical studies with forty FPDs. Three in-vitro studies with three-unit FPDs.Case Series
Key resultsClinical alumina study success rate was 90% after 5 years. 65% survival rate 6 years later. Second clinical study had 100% success rates of 2 and 3 year follow ups. Three in-vitro studies included: 1) higher (P < 0.001) mean flexural strength for specimens exposed to saliva after glazing as opposed to those exposed before. FPDs on shoulder preparations had higher stress resistance than those on chamfer finish lines (P=0.051). 2) total fractures less frequent in zirconia than alumina group (P<0.001). 3) FPDs loaded on implants resisted higher fracture loads (mean = 604 N, SD=184 N) than on abutment teeth (mean= 378 N, SD=152 N, P = 0.003).
#3) 22462639Lin/2012Five ceramic core materials.Comparative lab study
Key resultsBoth veneered ZirCAD groups, 0.8C-0.7VL and 0.8C-0.7VP, had greater flexural strength than monolithic Empress and e.max groups. These results were valid regardless of core thickness and fabrication techniques. ZirCAD group had the highest Weibull modulus. Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair). However, Empress Esthetic/CAD groups had lower flexural strength than e.max CAD/Press (p < 0.0001). With all core materials, Monolithic core specimens presented with higher Weibull modulus.
Evidence Search "Aluminum silicates/chemistry"[Mesh] AND "Zirconium/Chemistry"[Mesh]
Comments on
The Evidence
In Tinschert's in vitro study, groups were similar at start. Groups were not treated the same with no follow up mentioned. No recall bias or competing interest noted. FPDs were controlled at different points to ensure standardized dimensions. Mode of failure and load recorded. In Vult von Steyern’s study, the study design was a case series. Groups were similar at start with a >80% completion rate. There was adequate follow up with groups treated the same. No signs of recall bias or competing interests. Lin’s study is an observational study with no meta analysis or systematic review. Groups were similar at start and were treated the same. No adequate follow up and no recall bias or competing interests noted.
Applicability The applicability of these studies will benefit patients in a clinical setting when deciding on core material to use for their crown. The results benefit patients in regards to material decision. There is no real harm for patients as a result of these studies.
Specialty/Discipline (Prosthodontics)
Keywords Zirconia core, lithium disilicate, dental crowns, fracture toughness, In-Ceram, IPS Impress
ID# 2417
Date of submission: 04/01/2013spacer
E-mail salasma@livemail.uthscsa.edu
Author Michael Salas
Co-author(s) e-mail
Faculty mentor/Co-author Niraj Patel, DDS
Faculty mentor/Co-author e-mail patelnk@livemail.uthscsa.edu
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