The effects of laser etching on shear bond strength at the titanium ceramic interface

The use of titanium has increased for metal ceramic restorations, as well as for use in titanium implants, with developments in CAD/CAM technology. Some surface treatments of titanium have been introduced to enhance the titanium bond strength to low-fusing porcelains; however, a more reliable, easily used dental laboratory method has not been established.

The purpose of this study was to compare the effect of laser etching as a titanium surface treatment with 3 other surface treatments (machining, airborne-particle abrasion, and acid etching), evaluating their ability to enhance the bond strength between a titanium substrate and porcelain.

A total of 64 specimen rods of commercially pure titanium (ASTM grade 2, 20 mm in length and 5.7 mm in diameter) were divided into 4 experimental groups (n=16) to receive different surface treatments: machined with no treatment (MS), airborne-particle abraded with alumina particles (250 microm) (APAS), acid etched with 10% HCl (AES), and laser etched (LES) using a neodymium-doped yttrium aluminum garnet laser (Nd:Y(3)AL(5)O(12), or Nd/YAG). Low-fusing porcelain (Triceram) was applied (4-mm thickness) to the treated titanium surfaces and fired. Shear bond strength testing was performed in a universal testing machine. All of the data were compared using 1-way ANOVA and the post hoc multiple range Tukey test (alpha=.05). Measurement of roughness (Ra value) and SEM analysis were also performed for 1 specimen of each group before and after the shear bond strength test to evaluate the nature of the fracture surface.

Shear bond strength values for the APAS group (22.22 (4.04) MPa) and the LES group (21.22 (3.41) MPa) were significantly greater (P<.05) than for the MS group (13.76 (3.16) MPa) and the AES group (14.98 (3.26) MPa). The SEM image after debonding of MS and AES showed porcelain retained on the surface. However, there was no difference in appearance between the APAS and LES before and after debonding.

Laser etching of titanium surfaces using an Nd/YAG laser was effective in improving bond strength with low-fusing porcelain, as compared to the acid-etching method. However, there was no significant difference between laser etching and airborne-particle-abrasion surface treatment.