Effect of light-tip distance on the shear bond strengths of resin-modified glass ionomer cured with high-intensity halogen, light-emitting diode, and plasma arc lights.
BACKGROUND
The purpose of this study was to assess the effect of light-tip distance on the shear bond strength and the failure site of brackets cured with 3 light-curing units (high-intensity halogen, light-emitting diode, and plasma arc).


METHODS
One hundred thirty-five bovine mandibular permanent incisors were randomly allocated to 9 groups of 15 specimens each. Stainless steel brackets (Victory Series, Unitek/3M, Monrovia, Calif) were bonded with a resin-modified glass-ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium) to the teeth, and each curing light was tested at 3 distances from the bracket: 0, 3, and 6 mm. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength.


RESULTS
When the 3 light-curing units were compared at a light-tip distance of 0mm, they showed no significantly different shear bond strengths. At a light-tip distance of 3 mm, no significant differences were found between the halogen and plasma arc lights, but both lights showed significantly higher shear bond strengths than the light-emitting diode light. At a light-tip distance of 6 mm, no significant differences were found between the halogen and light-emitting diode lights, but both showed significantly lower bond strengths than the plasma arc light. When the effect of the light-tip distance on each light-curing unit was evaluated, the halogen and light-emitting diode lights showed no significant differences among the 3 distances. However, the plasma arc light produced significantly higher shear bond strengths at a greater light-tip distance. No significant differences were found among the adhesive remnant index scores of the various groups, except with the LED light at a distance of 3 mm.


CONCLUSIONS
In hard-to-reach areas, the plasma arc curing light is suggested for optimal curing efficiency.
Sfondrini
Maria Francesca
MF
Department of Orthodontics, University of Pavia, Pavia, Italy.
Cacciafesta
Vittorio
V
Scribante
Andrea
A
Boehme
Andreas
A
Jost-Brinkmann
Paul-Georg
PG
D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects*; D000538:Aluminum Silicates / Q000737:chemistry / Q000528:radiation effects*; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D016009:Chi-Square Distribution; D001840:Dental Bonding / Q000379:methods*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry / Q000528:radiation effects*; D006219:Halogens; D008027:Light; D008422:Materials Testing; D016910:Orthodontic Brackets; D044367:Phase Transition; D011897:Random Allocation; D012666:Semiconductors; D033081:Shear Strength; D013674:Technology, Dental / Q000295:instrumentation*; D014978:Xenon
D000180:Acrylic Resins; D000538:Aluminum Silicates; C095451:Fuji Ortho LC; D005899:Glass Ionomer Cements; D006219:Halogens; D014978:Xenon