Abstract
Background The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems – press-on metal (PoM) ceramic versus a conventional veneering system – subjected to static compressive loading. Material and Methods Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Results Fracture resistance values showed statistically significant differences (Student’s t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Conclusions Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope.
Highlights
Metal ceramic crowns are a treatment that has been – and still is – in common use for prosthetic restorations supported by natural teeth or dental implants [1,2]
Metallic core restorations are usually processed with a conventional veneering system but an alternative option is the use of the press-on metal ceramic technique – PoM
The null hypothesis was that the pressed ceramic-to-metal (PoM) system would provide greater fracture resistance than the conventional metal ceramic system
Summary
Metal ceramic crowns are a treatment that has been – and still is – in common use for prosthetic restorations supported by natural teeth or dental implants [1,2]. The metal coping is fabricated using the same technique but the ceramic veneer is made using a wax-up and a hot press furnace. The aim of this study was to assess the mechanical failure behavior of two types of porcelain-veneered crowns with metal core (IPS In-Line conventional feldespathic versus IPS In-Line press-on metal [PoM] [Ivoclar Vivadent, AG, Schaan, Liechtenstein]), when subjected to static compressive loading to the point of fracture, and to analyze fracture characteristics by scanning electron microscopy (SEM).
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