Load-bearing capacity and the recommended thickness of dental monolithic zirconia single crowns.
OBJECTIVE
The aim of this study was to evaluate the load bearing capacity and a reasonable thicknesss of dental monolithic zirconia crowns.


METHODS
Polymethyl methacrylate (PMMA) abutment tooth specimens were made by CAD/CAM technic. Monolithic zirconia crowns (MZC), monolithic lithium disilicate crowns (MLC), layered zirconia crowns (LZC) and metal ceramic crowns(MCC), of which the occlusal thickness was 1.5mm were thereafter fabricated and cemented on the abutment tooth specimens. MCC with occlusal thicknesses of 0.6mm, 0.8mm, 1.00mm, 1.2mm were also made. All specimens underwent load-to-fracture test. Weibull parameters (σ0) and (m) were calculated. Fracture modes were also evaluated.


RESULTS
The mean fracture load was 1863.16±116.81 for MLC, 2284.77±355.60 for MCC, 2308.0±510.94 for LZC, 4109.93±610.18 for MZC (1.5mm), 3068.31±233.88 for MZC (1.2mm), 2429.88±315.03 for MZC (1.0mm), 1814.60±68.21 for MZC (0.8mm) and 1308.38±111.38 for MZC (0.6mm). The fracture load of MZC was significantly higher than MCC, LZC and MLC (P<0.05). The fracture loads for MCC with different thickness were significantly different (P<0.05). Similar trend was observed for the characteristic strength (σ0) and Weibull modulus (m). For MZC and MLC, the fracture mode was catastrophic failure. The predominant fracture mode for LZC was catastrophic fracture. The fracture loads of MZC(1.0mm) and MCC were not statistically different (P>0.05).


CONCLUSIONS
Monolithic zirconia crowns exhibit higher fracture loads than monolithic lithium disilicate crowns, layered zirconia crowns and metal ceramic crowns. The fracture resistance of monolithic zirconia crowns with a thickness of 1.0mm can be equal to metal ceramic crowns. Doubling the monolithic zirconia core from 0.6mm to 1.5mm increases the fracture resistance of this restorative system threefold.
The Medical Centre of Stomatology, the 1st Affiliated Hospital of Jinan University, Guangzhou 510630, China.
Ting
T
Sun
Department of Stomatology, Nanfang Hospital, Southern Medical University, No.1838, North of Guangzhou Street, Guangzhou 510515, Guangdong, China.
Shanyu
S
Zhou
The Medical Centre of Stomatology, the 1st Affiliated Hospital of Jinan University, Guangzhou 510630, China.
Renfa
R
Lai
Department of Stomatology, Nanfang Hospital, Southern Medical University, No.1838, North of Guangzhou Street, Guangzhou 510515, Guangdong, China.
Ruoyu
R
Liu
The Medical Centre of Stomatology, the 1st Affiliated Hospital of Jinan University, Guangzhou 510630, China.
Shuyuan
S
Ma
The Medical Centre of Stomatology, the 1st Affiliated Hospital of Jinan University, Guangzhou 510630, China.
Zhiying
Z
Zhou
Department of Stomatology, Nanfang Hospital, Southern Medical University, No.1838, North of Guangzhou Street, Guangzhou 510515, Guangdong, China. Electronic address: shaolongquan@smu.edu.cn.
Shao
S
Longquan
D002484:Cementation; D002516:Ceramics; D003442:Crowns; D003738:Dental Cements; D017267:Dental Prosthesis Design / Q000379:methods*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D006801:Humans; D008094:Lithium / Q000737:chemistry; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D014070:Tooth / Q000648:ultrastructure; D016474:Weight-Bearing; D015040:Zirconium / Q000737:chemistry*
D003738:Dental Cements; D016876:Metal Ceramic Alloys; D008094:Lithium; D015040:Zirconium; C028541:zirconium oxide
Fracture load; Monolithic; Single crown; Thickness; Zirconia