A comparison of the shear bond strength of metal orthodontic brackets that have been treated with various light-emitting diode intensities and curing times: In-vitro research
Authors: Patil Gananjay , Kumar Santosh , Dogra Namrata , Nindra Jasmine , Kadam Satwashila , Yadav Krishna 
Published: November 2023

The study aims to test the effects of LED light at three different power settings (500mW/cm2, 1000mW/cm2& 1500m W/cm2) and three different exposure times (5sec, 10sec & 20sec) adhesive composites for use with stainless steel orthodontic brackets, and their shear bond strengths. Current In-vitro work used 120 teeth, mostly premolars, separated into 10 equal groups of 12. After the crowns of the teeth were exposed by mounting them vertically into self-heal acrylics, the buccal-enamel exterior was prepared for bonding (PEA) 0.022”x 0.028” stainless steel premolar bracket using a thin layer of light cure adhesive primer and paste (Transbond-XT-3M Unitek Monrovia, Calif). Brackets in Group 1 comprising the Control group treated by usual halogen light source for forty sec, in remaining 9 groups (Experimental group) three commercially available LED curing light units i.e., Woodpecker, Guilin, Guangxi, China; Stealth Soft Equinox, Denmark, Holland; Radii plus, SDI, Australia, having three different light intensity 500mW/cm2, 1000mW/cm2, 1500mW/cm2 respectively were used to bond the brackets at three contact time (5/10/20 sec). The universal testing equipment was used to determine the shear bond strength of each specimen. The uppermost average SBS was found in the group cured with LED of intensity 1500 mW/cm2 for 20 sec (20.08 + 4.82 MPa) which was statistically significant compared the to control group (12.72 + 2.42 MPa). The lowest mean SBS values were obtained for groups cured with LED of intensity 500 mW/cm2 even at different curing times of 5, 10 and 20 sec i.e., 5.46 + 1.99 MPa, 8.77 + 2.38 Mpa and 11.24 + 2.59 MPa, respectively. Increasing the intensity of the LED light curing unit provides a clinically acceptable SBS even after reducing the curing times, thereby reducing the chairside time for bonding of orthodontic brackets.The study aims to test the effects of LED light at three different power settings (500mW/cm2, 1000mW/cm2& 1500m W/cm2) and three different exposure times (5sec, 10sec & 20sec) adhesive composites for use with stainless steel orthodontic brackets, and their shear bond strengths. Current In-vitro work used 120 teeth, mostly premolars, separated into 10 equal groups of 12. After the crowns of the teeth were exposed by mounting them vertically into self-heal acrylics, the buccal-enamel exterior was prepared for bonding (PEA) 0.022”x 0.028” stainless steel premolar bracket using a thin layer of light cure adhesive primer and paste (Transbond-XT-3M Unitek Monrovia, Calif). Brackets in Group 1 comprising the Control group treated by usual halogen light source for forty sec, in remaining 9 groups (Experimental group) three commercially available LED curing light units i.e., Woodpecker, Guilin, Guangxi, China; Stealth Soft Equinox, Denmark, Holland; Radii plus, SDI, Australia, having three different light intensity 500mW/cm2, 1000mW/cm2, 1500mW/cm2 respectively were used to bond the brackets at three contact time (5/10/20 sec). The universal testing equipment was used to determine the shear bond strength of each specimen. The uppermost average SBS was found in the group cured with LED of intensity 1500 mW/cm2 for 20 sec (20.08 + 4.82 MPa) which was statistically significant compared the to control group (12.72 + 2.42 MPa). The lowest mean SBS values were obtained for groups cured with LED of intensity 500 mW/cm2 even at different curing times of 5, 10 and 20 sec i.e., 5.46 + 1.99 MPa, 8.77 + 2.38 Mpa and 11.24 + 2.59 MPa, respectively. Increasing the intensity of the LED light curing unit provides a clinically acceptable SBS even after reducing the curing times, thereby reducing the chairside time for bonding of orthodontic brackets.