Adhesion of porcelain to titanium and a titanium alloy.

OBJECTIVES: The objectives of the study were to determine the adhesion at the titanium-porcelain interface using a fracture mechanics approach, and to investigate the bonding mechanism using SEM and X-ray microanalysis. METHODS: Specimens of four titanium-porcelain bonding systems were prepared in a rectangular shape for a four-point bending test on a universal testing machine. The pre-cracked specimen was subjected to a limited number of load and partial unload cycles, and the strain energy release rate or interfacial toughness (G(c) value) was calculated for each system. The interface was investigated in an SEM, which also enabled quantitative X-ray microanalysis, and comparison with a simulation of an atomically sharp interface to ascertain whether diffusion bonding occurred. RESULTS: The Titanium/Titankeramik with GoldBonder bonding system showed the highest G(c) value (48.9+/-12.4 J/m(2)) among the groups whilst Titanium/Duceratin showed the lowest (12.9+/-3.6 J/m(2)). The former was significantly higher than that of nickel-chromium/porcelain (40.3+/-4.8 J/m(2)) from the previous study [Int J Prosthod 12 (1999) 547], which is a clinically accepted bonding system. The G(c) values of Titanium/Titankeramik and Titanium alloy/Titankeramik were 16.7+/-2.4 and 27.8+/-5.3 J/m(2), respectively. The X-ray microanalysis suggested that diffusion of some elements has occurred at the interface. CONCLUSIONS: The strain energy release rate (G(c)-value) of titanium/Titankeramik with GoldBonder was highest among the four systems. X-ray microanalysis gave some evidence of diffusion of some elements, particularly of the porcelain into the metal, which may assist the bonding during the firing.

Determination of elastic properties of metal alloys and dental porcelains.

This study aimed to determine Young's modulus, shear modulus and Poisson's ratio of some metal alloys and dental porcelains used in fixed prosthodontics using the technique of impulse excitation of vibration. It also aimed to compare Young's modulus values of these materials with those obtained using the other two methods: the four-point flexural test and the indentation test using the ultra micro-indentation system (UMIS). Five types of metal alloys and four types of dental porcelains were tested. The samples were prepared to a rectangular shape of approximately 8 x 30 x 1.5 mm. Frequency of vibration in a sample was read when a singular elastic strike was made with an impulse tool. The elastic constants were calculated from the frequency of vibration, dimension and mass of each sample. Young's modulus values resulting from the impulse excitation of vibration are not significantly different (P<0.05) from those obtained using the flexural test and the UMIS test in most metal alloys but are different in titanium, titanium alloy and most of the dental porcelains. The technique of impulse excitation of vibration has proven to be an accurate method and is simple to operate. The elastic properties of these alloys and porcelains are essential for determining the other mechanical properties (fracture toughness) and are relevant in clinical application.

Characterisation of tribochemically assisted bonding of composite resin to porcelain and metal.

OBJECTIVE: The fracture of bonded ceramic to metal restorations remains a problem in clinical dental practice. The use of resin based composites to repair such fractures is generally unsatisfactory. Tribochemical technology creates a surface layer of small silica particles fused to the surface substrate. Such a layer potentially improves adhesion of resin to both alloy and porcelain. Adhesion between two substrates is traditionally studied using shear or tensile bond strength tests. However, the highest stress at bond failure may not represent the real bonding characteristics correctly. An alternative method is to describe the bonding characteristics by determining the strain energy release rate for a given interface. This study compares the bonding characteristics of a resin to gold/porcelain interface using a tribochemical coating process with those of a control group using simple gritblasting. METHODS: Pre-cracked specimens were subjected to load-unload cycles using a simple four point bending test and the resultant strain energy release rates were calculated. RESULTS: Tribochemically pretreating the porcelain resulted in a significant increase in the resultant strain energy release rate from 42.72+/-3.65J/m(2) for the controls to 61.35+/-6.26J/m(2). Likewise there was a significant improvement in the strain energy release rate for the gold/composite interface from 27.31+/-3.00J/m(2) to 42.13+/-4.83J/m(2). CONCLUSIONS: Tribochemical technology offers significant potential advantages for clinical dental practice.

New approach for evaluating metal-porcelain interfacial bonding.

PURPOSE: The purpose of this study was to evaluate the bonding characteristics of porcelain-fused-to-metal (PFM) systems by determining the strain energy release rate associated with interface fracture of porcelain and metals. MATERIALS AND METHODS: Porcelain-veneered metal plates cast from commercially pure titanium and 3 metal alloys (gold, palladium, and nickel-chromium alloys) were made to dimensions of 25 mm x 8 mm x 2.5 mm with comparable thicknesses of porcelain and metal. The porcelain side of the specimens was notched to the interface with a thin diamond saw, and a small precrack was initiated at the metal-porcelain interface. The samples were subjected to a limited number (typically less than 4) of load-unload cycles under 4-point bending at a crosshead speed of 0.1 mm/min. The loading and unloading force displacements associated with stable crack extension were recorded. The strain energy release rate was calculated. The interfacial area was also examined under scanning electron microscope (SEM) after the test. RESULTS: The mean strain energy release rates were 72.7 +/- 10.0 J/m2, 58.5 +/- 13.5 J/m2, 39.4 +/- 4.3 J/m2, and 16.6 +/- 2.5 J/m2 for the samples of gold, palladium, nickel-chromium alloys, and titanium, respectively. The SEM photographs showed that the crack occurred in the porcelain layer close to the interface. CONCLUSION: The bonding characteristics of PFM systems were determined with 3 types of metal alloys and commercially pure titanium by a fracture mechanics approach. The gold alloy and titanium are considered to obtain the greatest and least adhesion, respectively. The test system has proven to be a simple and reliable approach to determine the bonding in biomaterial systems.

Properties of acrylic resins incorporating 4META for bonding to cobalt-chromium alloys.

Polymer substitution into proprietary 4-methacryloxyethyltrimellitate anhydride (4META) resins creates tooth coloured veneers for cobalt-chromium overlay dentures. The elastic moduli and shear-bond strengths of proprietary resins (matched) and resins polymerised from 4META monomers and substituted polymers (unmatched) were determined. Bond strengths were similar for matched and unmatched heat curing resins (mean 14.1 (SD 1.6 MPa)) but differed for matched (6.9 (SD 1.3) MPa) and unmatched self-curing resins (5.7 (SD 0.9) MPa). Preparation of the alloy surface immediately before packing with resin dough provided significantly higher bond strengths. Structural examination in a scanning electron microscope suggested that bonds developed by unmatched resins may provide less satisfactory clinical performance.