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Bonding Strength of Orthodontic Brackets on Porcelain Surfaces Etched by Er:YAG Laser.

OBJECTIVE
To evaluate the effect of erbium: yttrium aluminium garnet laser conditioning bond strength of orthodontic brackets on porcelain surfaces.


BACKGROUND
There are few studies that evaluate the effect of Er:YAG laser about orthodontic bonding on porcelain surface. The efficacy of Er:YAG laser in porcelain conditioning is controversial.


MATERIALS AND METHODS
Ninety ceramic specimens were randomly divided into five group, group A: etched with hydrofluoric (HF) acid; group B and C: etched with an energy parameter of 250 mJ, 20 Hz and 300 mJ, 20 Hz by Er:YAG laser instrument; group D and E: etched with an energy parameter of 250 mJ, 20 Hz and 300 mJ, 20 Hz of Er:YAG laser with HF etching. Afterward, two samples selected randomly from each group were evaluated by scanning electron microscopy. Brackets were bonded on the remaining samples, which were stored in distilled water and thermocycled. Each group was measured by shear bond strength (SBS), tensile bond strength (TBS), porcelain fracture index (PFI), and adhesive remnant index (ARI) calculation. Data were statistically analyzed using SPSS software.


RESULTS
The SBS and TBS in group E were the largest. Comparing SBS and TBS of HF group and other Er:YAG laser group, there were statistically significant difference (p < 0.05). PFI was significantly higher in shear force group than the tensile force group. HF group had higher ARI score than the other groups.


CONCLUSIONS
Porcelain surfaces etched by 250 mJ, 20 Hz of Er:YAG laser combined with HF acid can get enough bond strength and have lower porcelain fracture rate for orthodontic bracket bonding.