Porcelain surface treatment by laser for bracket-porcelain bonding

Abstract

Introduction: The purposes of this study were to investigate the effect of laser irradiation on the adhesion of brackets bonded to feldspathic porcelain and to compare it with brackets bonded with conventional techniques.

Methods: One hundred porcelain-fused-to-metal specimens were divided into 10 groups of 10. The treatment groups were sandblasted (SB), sandblasted with silane (SB+S), orthophosphoric acid (OFA), orthophosphoric acid with silane (OFA+S), hydrofluoric acid (HFA), hydrofluoric acid with silane (HFA+S), laser etched (L), laser etched with silane (L+S), glazed (Control 1/C1), and deglazed (Control 2/C2). Five other specimens were irradiated by 2-, 3-, 5-, 10-, and 15-watt superpulse carbon dioxide (CO2) laser for 20 seconds and examined by scanning electron microscopy. Metal brackets were bonded with a self-cure composite material and the specimens were stored in water at 37 degrees C for 24 hours and then thermocycled in water baths between 5 degrees C and 55 degrees C 500 times. Bond strength was determined in megapascals (MPa) by shear test at 1 mm/minute crosshead speed. Bond failure modes were observed under stereomicroscope. For the statistical analysis, 1-way ANOVA and Tamhane post hoc test were used.

Results: Statistical analysis showed significant differences between the groups at the .05 level. The HFA+S group yielded the highest mean strength (15.07 +/- 1.44). This was followed by SB+S (13.81 +/- 2.00), HFA (10.78 +/- 0.62), OFA+S (10.73 +/- 1.12), L+S (8.25 +/- 0.90), L (6.26 +/- 0.58), C2 (2.45 +/- 0.54), OFA (2.36 +/- 0.41), SB (2.04 +/- 0.41), and C1 (1.64 +/- 0.33). The bond failure modes of HFA and silane groups, except L+S, were cohesive in porcelain. Control groups and other test groups showed adhesive failure. Only irradiation by 2 watts for 20 seconds provided a porous surface texture without cracks.

Conclusions: Two-watt/20 second superpulse CO2 laser irradiation might be an alternative conditioning method for pretreating ceramic surfaces. Increased bond strength can be achieved by silanation after CO2 laser irradiation.