Microleakage Beneath Orthodontic Metal Brackets Bonded After Thermocycling with Two Different Adhesive Systems of Different Temperatures: an in-vitro Study

Introduction: The possibility of using traditional composite restoratives has beenraised to bond orthodontic brackets. The higher viscosity observed with restorativecomposites compromised their ability to adhere to the bracket base. Pre-heating therestorative composites puts the monomers into a state of thermal agitation that increasesmolecular motion which enhances flowability. The first null hypothesis was thatmicroleakage underneath brackets using bulk fill composite was comparable to that ofconventional orthodontic adhesives. Additionally, a second null hypothesis was set up,that preheating bulk fill composite before polymerization decreased the polymerizationshrinkage hence the microleakage scores. Materials and methods: A sample of 56upper first premolars was collected and divided across 4 groups; I: Transbond XT atroom temperature; II: Transbond XT preheated to 60ºC; III: X-tra fil at room temp; andIV: X-tra fil preheated to 60ºC. After thermocycling, roots were coated with wax whilecrowns with nail varnish then submerged into a solution of 2% methylene blue. Afterroots were cut off, the remaining crowns in every group were divided into 2 subgroups,those of one subgroup were longitudinally split into mesial and distal halves, while thoseof the other subgroup were transversely split into gingival and occlusal halves. Depth ofdye penetration at the adhesive-enamel interface was measured under stereomicroscopeat x45 magnification. Results: photopolymerization of x-tra fil after preheating hasexhibited lesser microleakage when compared to Transbond XT, however the resultsrendered statistically insignificant. Conclusion: The X-tra fil proved to be a reliableadhesive for orthodontic brackets.