| Objective:Microleakage、shear bond strength and compressive strength of three kinds of commonly used light-cured resin sealants were compared to provide reference for clinical selection of sealants with high quality.Material and methods:Experiment 1: Comparison of microleakage and marginal suitability of three pit and fissure sealantsThirty freshly-extracted maxillary first premolars because of orthodontic reason were collected from 12 to 14 years old adolescents which were healthy and caries-free and met the requirements of this experiment.The premolars were randomly divided into groups A,B and C(n=10).Pits and fissures of the crowns were sealed with SDI Conseal f(group A),UltraSeal XT(group B)and 3M Clinpro(group C)sealants respectively.The unqualified teeth were re-sealed.After sealing,all specimens were immersed in a constant temperature water bath at 37℃ for 24 hours.And then,all the samples were immersed in cold water at 5(±2)℃and hot water at 55(±2)℃ alternately for 5000 cycles.The immersion time for each temperature was 30 seconds and the transfer time was 5 seconds.All specimens were removed out of water and blowed dry for later use after the immersion cycle.In each group,8 specimens were sealed apically with plastic and two layers of nail polish were evenly coated 1mm away from the edge of the sealant.After drying,the samples were immersed in 2% methylene blue solution for dyeing.The samples were taken out after 24 hours,and the excess dyes were thoroughly washed with running water.The nail polish was then scraped off and dried.Specimens were mounted on a hard tissue cutting machine and sliced along the buccal-lingual direction at three places: corresponding points of the central sulcus near-midpoint gap,far-midpoint gap and the midpoint of the near-midpoint gap connection.Six sections were obtained for each group(a total of 48 sections for each group of 8 specimens).The microleakage and dye penetration depth of each group were observed and compared under stereomicroscope.The data were analyzed with SPSS17.0 statistical software.The other two specimens of each group were cut at the midline in the buccal-lingual direction.The infiltration depth of sealant and the condition of the interface were observed by SEM and photographs were taken selectively.Experiment 2: Comparison of shear strengths of three pit and fissure sealantsFifteen freshly-extracted maxillary first premolars because of orthodontic reason were collected from 12 to 14 years old adolescents which were healthy and caries-free and met the requirements of this experiment.The premolars were cut into 30 enamel blocks with flat mesial and distal surfaces,which were randomly divided into three groups(n=10)and bonded with three sealants at the flat mesial and distal surface.All the specimens were immersed in water at 37℃ for 24 hours.After soaking,5000 cycles of cold and hot cycle were carried out.The shear strength was measured and analyzed.Experiment 3: Comparison of compressive strength of three pit and fissure sealantsThirty cylinders(4 mm in diameter and 4 mm in height)of three kinds of sealants were manufactured by using polytetrafluoroethylene(PTFE)mould,and all the specimens were immersed in water at 37℃ for 24 hours.After soaking,5000 cycles of cold and hot cycle were carried out.The compressive strength was measured and analyzed.Results:1.The SEM photographs showed that UltraSeal XT bonded with enamel completely and penetrated into the bottom of pit and fissure.SDI Conseal F and 3M Clinpro sealants closely bonded to enamel,but there were bubbles or cracks in the sealants at the bottom of pit and fissure.2.The shear bond strength of group C was the highest(6.57±0.18 MPa)and group A was the second(6.56±0.28 MPa)and group B was the lowest(4.58±0.13 MPa).The shear bond strengths of group A and C were higher than group B(P < 0.05)whereas there was no significant difference between group A and C(P> 0.05).3.The compressive strength of group B was the highest(281.60 ±17.40 MPa),followed by group A(223.12 ± 42.28 MPa)and group C(218.13 ± 57.83 MPa).The compressive strength of Group B was higher than group A and C(P< 0.05)whereas there was no significant difference between group A and C(P> 0.05).Conclusion:1.Under the limitions of of this experiment,3M Clinpro and UltraSeal XT sealants had better marginal adaptation with enamel.2.SDI Conseal F and 3M Clinpro sealants had higher shear bond strengths,which can resist functional masticatory force and achieve satisfactory clinical bonding effect.3.UltraSeal XT sealant had the highest compressive strength and good wear resistance in long term clinical application,which can withstand occlusal force and prolong service life of sealant. |
PDF Full Text Request