The Experimental Study On The Leakage Of Adhesive Interface With Different Treatments

Objective:The purpose of this study was to evaluate the effects of the pulsed Nd:YAG laser and phosphoric acid on the microleakage and nanoleakage beneath the restoration.Method35 freshly extracted young human premolars were used for this study.A box cavity preparation was performed at 1 mm above the Cemento-Enamel Junction(CEJ)on opposite sides of each tooth(buccal and lingual).The teeth were divided into 7 groups of experimental and control in a random manner:P0,P1,P2,P3,L1,L2,and L3.Groups P1, P2,P3 were etched by 35%phosphoric acid for 15sec/30sec and 45sec. Groups L1,L2,L3 were exposed to 0.75W/1.0W and 1.25W power with a pulsed Nd:YAG laser energy:15Hz for 20sec.Groups P0 was used as negative control group,and its adhesive interface was performed without treatment.Cavities were washed and dried prior to the application of a light cured adhisive(singlebond).Composite resin(P60)restorations were placed into all prepared cavities in an incremental manner.After this,the apical foramen of each tooth was covered with self-curing rising followed by apex.Two layers of nail varnish were applied to all surfaces of the teeth leaving 1 mm away from the cavity margins.All the teeth were immersed in 1wt%RhodamineB/50%alcohol solution for 24 hours at 37℃.And then after washing by distilled water for 10sec,All samples were subjected to storage in 20℃distilled water for another 24 hours. Subsequently,each specimen was sliced longitudinally with a slow speed diamond disk with water coolant,producing approximately 2-mm wide samples then polished the samples.After that,all the samples were evaluated under the Laser Scanning Confocal Microscope(LSCM)for the extent of dye penetration.ResultsAll teeth from Group P0(not treated with Nd:YAG laser or phosphoric acid)showed much more RhodamineB penetration than the teeth treated with Nd:YAG laser or phosphoric acid.Results indicated that the level of microleakage of GroupL1,laser-treated cavities for 0.75W laser power,was significantly less than any other groups(P＜0.05).Group L1(treated with Nd:YAG for 0.75W)and Group L2(treated by Nd:YAG 1.0W)showed the least nanoleakage extent,followed by Group P2(treated with phosphoric acid for 30sec).But the difference between the 3 groups was no significant.In Group P3(treated with phosphoric acid for 45 sec)the nanoleakage extent shows significantly longer than any other groups.Conclusion:1,Both of the phosphoric acid and the Nd:YAG laser could reduce microleakage and nanoleakage beneath the restoration.2,The optimum parameter of pulse Nd:YAG laser is 0.75W,15Hz for conditioning dentin surface,which effects is much better than that of phosphoric acid.3,The pulse Nd:YAG laser that has capacity to seal the dentin tube efficiently is appropriate to treat hypersensitive teeth and decreace the leakage.