The effect of light intensity and curing time of light emitting diode on shear bond strength using different types of bracket's materials


Background: This study was intended to evaluate the effect of two LED devices which has different light intensity andcuring time on the shear bond strength (SBS) using stainless steel and two other esthetic brackets.Materials and method: Sixty first premolar teeth were selected. Three types of orthodontic brackets were used in thisstudy: stainless-steel brackets, the other two types are esthetic ceramic brackets. Two high intensity LED units wereused, the first one was of a lower intensity (HANGZHOU SIFANG, China), the output power 1200 mW/cm2, the secondsource had the higher intensity (FlashMax P3, Denmark) which has power intensity of 4000 mW/cm2. The teeth weredivided into two groups (Aand B) of 30 teeth each. Group A was used for testing HANGZHOU SIFANG device instandard cure time (20s) , while the group B was used for testing Flash Max P3 device in fast curing mode(6s). A andB groups were further subdivided according to bracket type into three subgroups of 10 teeth each. SBS of allsubgroups were tested by using an Instron universal testing machine, ARI was assessed at (20X) magnification.Results: The clinically acceptable SBS were excelled in both the standard and fast curing mode groups for all brackettypes, significant differences were found only when comparing the Pure with the other two types of brackets in thesame group. Comparing each bracket type between group A and group B reveals a significant difference only atstainless-steel type brackets.Conclusions: the new high intensity curing devise gave comparable SBS to the LED units previously available withshorter time.