The Effects Of Different Clinical Procedures On Bond Strength Of Resin-modified Glass Ionomer Cement

ObjectiveThe purpose of the study was to assess the effect of different clinical procedures on the bond strength of resin-modified glass ionomer cement(RMGIC),and to provide a reference for future clinical orthodontic bracket bonding.Materials and Methods90 extracted human premolars were randomly divided into 6 groups(n=15): Group A,B,C,D,E and F.The first experiment evaluated the effect of tooth surface treatment on bond strength.Group A,B and C were etched by phosphoric acid then rinsed thoroughly.Group A was dried with compressed air for 10 s.Group B was dried with compressed air for 10 s,followed by wetted with moist cotton balls.Group C was dried with dry cotton balls.AO metal brackets were bonded to the clinical crown center of teeth using GC Fuji orthodontic adhesive.Teeth were embedded in 24-well plates to prepare test sample,and the maximum load in Newtons required to debond each bracket was tested and then converted into shear bond strength(SBS).The adhesive remnant index(ARI)was recorded to evaluate the amount of adhesive left on the enamel surface.The SBS was analyzed by one-way ANOVA test and the ARI was analyzed by Kruskal-Wallis test using SPSS version 17.The second experiment evaluated the effect of bracket moving timing on bond strength.The results obtained from the first experiment was applied to D,E,F group to achieve the same surface treatment.The Group D was boned with no bracket displacement.The Group E was boned with 2mm linear displacement and then compacted.The Group F was compacted first,and after 2mm movement,the Group F was compacted again.The test samples fabrication,test procedure and statistics analysis were same as the first experiment.Results1.The SBS of Group A was(10.6±1.78)MPa,of Group A was(9.89±1.98)MPa,of Group A was(12.15±1.59)MPa.One-way ANOVA analysis showed that there were statistically significant differences in SBS among Group A,Group B and Group C(F=6.256,p<0.05).2.LSD-t test was used to compare each two groups in the first experiment.No significant difference was detected between Group A and Group B(p>0.05).There was significant difference between Group A and Group C,Group B and Group C(p<0.05).3.There was no significant difference in ARI scores among Group A,B and C(p>0.05).4.The SBS of Group D was(12.20±1.82)MPa,Group E was(11.11±2.33)MPa,and Group F was(9.32±1.74)MPa.One-way ANOVA analysis showed that there were significant differences in SBS among Group D,Group E and Group F(F=8.08,p=0.001).5.LSD-t test was used to compare each two groups in the second experiment.No significant difference was detected between Group D and Group E(p>0.05).There was statistically significant difference between Group D and Group F,and between Group E and Group F(p<0.05).6.There was no significant difference in ARI scores among group D,E and F(p>0.05).Conclusion1.The bond strength of RMGIC can achieve the clinical requirement.2.The bond property of RMGIC is beneficial to protect enamel from damage when bond failure occurs.3.RMGIC has the best bond strength under the condition of slight wetting,and excessive drying will affect its bond strength.4.The bracket movement at an improper timing may affect the bond strength of RMGIC.