| Objective: This experiment is intended to explore the effects of different etching methods on marginal of pit and fissure sealant.Methods:1 pit and fissure sealant technique was applied to classify the 48 maxillary premolars which were recently extracted by orthodontical extraction randomly, 8 premolars for each group. Among which, Group 1: 35%Gluma phosphoric acid +3M pit and fissure sealant; Group 2: 35%Gluma phosphoric acid +3M flowable nanocomposite resin; Group 3: S3 BONDTM 7th- generation self-etching bonding +3M pit and fissure sealant; Group 4: S3 BONDTM 7thgeneration self-etching bonding +3M nanocomposite resin; Group 5: 15%Hcl gel+3M pit and fissure sealant; Group 6: 15%Hcl gel+3M flowable nanocomposite resin. The specimens of the 6 groups were treated for fissure sealing. 2 The specimens of the 6 groups received heat recycling treatment, and placed in 37℃ thermostatic waterbath for 24 h. Then these specimens were soaked for 500 cycles at 5℃ and 55℃ waterbath, 30 s duration for each temperature. 3 6 specimens randomly selected from each group shall be stained with methylene blue, and the microleakages of them were then observed with stereomi- croscope. 4 The remaining 2 specimens of each group were observed for their marginal tightness with scanning electron microscope(SEM).Results:1 Details of microleakages. 1.1 Micro-leakages of specimens in each group using pit and fissure sealant : Group 1 was lower than Group 3, Group 5 was lower than Group 3, bothpresenting significant difference(P<0.05);Group 5 was lower than Group 1, showing no statistically significant difference(P>0.05). 1.2 Micro-leakages of specimens in each group using 3M flowable nanocomposite resin : Group 6 was lower than Group 2, Group 2 was lower than Group 4, both presenting significant difference(P<0.05). 1.3 After etching by 35%Gluma phosphoric acid, the micro-leakage in Group 1 and 2 was similar, showing no statistically significant difference(P>0.05); After etching by S3 BONDTM 7th- generation self-etching bonding, Group 3 was lower than Group 4, presenting significant difference(P<0.05);After etching by 15%Hcl gel, Group 6 was lower than Group 5, presenting significant difference(P<0.05). 1.4 Cross-comparison between the specimens using different etching methods and different sealing materials was performed, and the micro-leakage in each group was as follows: Group 1 was lower than Group 4, Group 6 was lower than Group 1, Group 2 was lower than Group 3, Group 5 was lower than Group 2, Group 6 was lower than Group 3,Group 5 was lower than Group 4, presenting statistically significant difference(P<0.05). 2 Observation results of SEM 2.1 Observation of overall specimen under low power(magnification x40): The pit and fissure sealant showed a few of micro-cavities, but was completely permeated to the bottom of fissure, some cracks appeared on its joint surface with enamel. Observation results under high power(magnification x1000): The micro-fissure width of joint surface between pit and fissure sealant and enamel was about 6.25~15μm. 2.2 Observation of overall specimen under low power(magnification x100): the flowable resins of Group 2 was unevenly, but was completely permeated to the bottom of fissure, no cracks appeared on its joint surface with enamel, and a crack was found in a place near the bottom; the pit and fissure sealant had a complete bonding with the enamel. Observation results under high power(magnification x1000): TheObservation results under high power(magnification x1000): Themicro-fissure width of joint surface between flowable resin and enamel in Group 2 was about 3.15~20.25μm. 2.3 Observation of overall specimen under low power(magnification x40): The pit and fissure sealant in Group 3 was completely permeated to the bottom, a cracks appeared on its joint surface with enamel.Observation and measurement results under high power(magnification x1000): The micro-fissure width of joint surface between pit and fissure sealant and enamel in Group 3 was about 2.1~20.25μm. 2.4 Observation of overall specimen under low power(magnification x40): The flowable resin was even, complete with no cavitation in Group 4; it was completely permeated to the bottom, and there existed a continuous crack on its joint surface with enamel.Observation and measurement results under high power(magnification x1000): The micro-fissure width of joint surface between flowable resin and enamel in Group 4 was about 12.5~75μm. 2.5 Observation of overall specimen under low power(magnification x100): The pit and fissure sealant in Group 5 was even, complete and with no cavitation; it was completely permeated to the bottom, and a small amount of tiny cracks were found on its joint surface with enamel.Observation and measurement results under high power(magnification x1000): The micro-fissure width of joint surface between pit and fissure sealant and enamel in Group 5 was about 2.1~4.5μm. 2.6 Observation of overall specimen under low power(magnification x40): The flowable resin was even, complete in Group 6; there appeared no cracks on its joint surface with enamel. And the pit and fissure sealant had a full bonding with the enamel.Observation and measurement results under high power(magnification x1000): The micro-fissure width of joint surface between flowable resin and enamel in Group 6 was about 0.25~4.5μm.Conclusions:1 After pre-treatment by 15%Hcl gel, 3M flowable nanocomposite resinshowed minimum marginal microleakage.2 After pre-treatment by SBOND7th- generation self-etching bonding, 3M flowable nanocomposite resin showed the most significant marginal microleakage. |
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