Effects of sandblasting and electrical discharge machining on porcelain adherence to cast and machined commercially pure titanium

Abstract

The aim of this study was to determine the effect of sandblasting and electrical discharge machining (EDM) on cast and machined titanium surfaces and titanium-porcelain adhesion. Twenty machined titanium specimens were prepared by manufacturer (groups 1 and 2). Thirty specimens were prepared with autopolymerizing acrylic resin. Twenty of these specimens (groups 3 and 4) were cast with commercially pure titanium and the alpha-case layer was removed. For control group (group 5), 10 specimens were cast by using NiCr alloy. Groups 2 and 4 were subjected to EDM while groups 1, 3, and 5 were subjected to sandblasting. Surface examinations were made by using a scanning electron microscope (SEM). A low-fusing porcelain was fused on the titanium surfaces, whereas NiCr specimens were covered using a conventional porcelain. Titanium-porcelain adhesion was characterized by a 3-point bending test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Metal-porcelain interfaces were characterized by SEM. The bond strength of control group was higher than that of the titanium-porcelain system. There was no significant difference between cast and machined titanium groups (p > 0.05). There was no significant difference between EDM and sandblasting processes (p > 0.05). The use of EDM as surface treatment did not improve titanium-porcelain adhesion compared with sandblasting.

Shear bond strengths of veneering porcelain to cast, machined and laser-sintered titanium

“…In this study, the mean bond strength of cast titanium ranged between 25 and 28 MPa, which was in agreement with several published studies 9,23,24) . Inan 28.3 MPa 13) .…”

“…To minimize CTE difference between titanium and porcelain, special low-fusing veneer porcelains have been developed by manufacturers 27) . However, a low firing temperature resulted in sub-optimally sintered ceramics, which then resulted in a weaker bonding with titanium 9) .…”

“…However, there are several technical problems associated with titanium investment castings, such as shrinkage and porosity formation 8) . This is because titanium has an extremely low density (4.5 g/cm 3 ), which reduces its mold-filling ability (castability) and consequently results in incomplete margins 9) . Besides, ingredients of the investment compound react with molten titanium at high temperatures during casting.…”

“…On the other hand, a low firing temperature resulted in suboptimally sintered ceramics, which then also resulted in weaker bonding with the titanium substrate 9) .…”

Improvement in Ti-porcelain bonding by SiO2 modification of titanium surface through cast method

“…Oxidation of Ti leads to a thick, loosened oxide layer [4][5][6] . Various surface treatments have been used to avoid the oxidation and to improve Ti-porcelain bonding strength, such as sandblasting 7,8) , chemical agent bath 9,10) , and the application of intermediate coating [11][12][13][14][15] . Sandblasting is ordinarily used for preparing metal substrates with surface irregularities.…”