Objective:To study the influences of sucrose,citric acid and sodium bicarbonate on the adhesion of 3 kinds of adhesives.Methods:60 extracted tooth and 60 zirconia blocks (3 mm × 3 mm × 3 mm) were randomly divided into 3 groups (n =20),namely PULPDENT group,3M ESPE RelyxTM Veneer group and RelyxTM Luting group.Then,the samples of each group fell into 4 subgroups(n=5),namely subgroup A for artificial saliva,subgroup B for 10％ sucrose,subgroup C for 0.2％ citric acid,and subgroup D for 0.03 ％ sodium bicarbonate.After completing the adhesion of the specimens with corresponding adhesives,the specimens of subgroups A,B,C and D were submerged into artificial saliva(the control),sucrose,citric acid and sodium bicarbonate solutions for 2 times/day and 5 min/time,respectively.For the rest of time,all the specimens were submerged in artificial saliva.3 months later,shear bond strength of the specimens was tested,the fracture surface was observed under SEM,20 × microscope,and the fracture model was observed by stereoscopic microscope.SPSS 17.0 software was adopted for statistical analysis of the data.Results:The bond strength of PULPDENT,3M ESPE RelyxTM Veneer groups were higher than that of RelyxTM Luting group(P ＜ 0.05);the bond strength of subgroups B,C and D was lower than that of subgroup A(P ＜0.05);and the difference between the remaining groups was not statistically significant(P ＞0.05).SEM observation displayed that in group RelyxTM Luting,subgroups B,C and D showed increased crack depth,width and length when compared with subgroup A;there was no obvious difference between the remaining groups and the control group;in groups PULPENT,3M ESPE RelyxTM Veneer and RelyxTM Luting,all samples in their subgroups showed interface failure.Conclusion:Compared with PULPDENT and 3M ESPE RelyxTM Veneer adhesive,RelyxTM Luting is more susceptible to the influence of sucrose,citric acid and sodium bicarbonate,so it is not suitable for bonding zirconia blocks.

OBJECTIVETo evaluate the influence of different polishing methods on marginal microleakage of zirconium dioxide full crown.

METHODSThirty extracted premolars were selected and randomly divided into three groups, A, B and C, with 10 in each group. Group A was prepared with MANI TF-13 bur completely without the treatment of shoulder. The shoulder of group B was polished with MANI TR13-EF bur after the preparation using MANI TF-13. The shoulder of group C was polished with the dental pneumatic ultrasonic hand-piece of KaVo SONICflex after the preparation using MANI TF-13 bur. Five specimens after preparation were selected in each group. Fifteen CAD/CAM zirconium dioxide full crowns have been made. The crowns were bonded using PULPDENT resin cement, and the root canals were sealed using nail polish, and apical foramen were closed using flow resin. The test-pieces have been immersed in a 3% solution of methylene blue for 24 h. The condition of shoulder marginal microleakage was observed using light stereomicroscopy and evaluated in classification index. The remaining specimens in each group were used for roughness test and scanning electron microscope(SEM) experiment. The marginal microleakage situations of specimens in three groups was analyzed by SPSS 17.0. The enamel surface of different polishing methods was observed using SEM.

RESULTSThe specimens in group C demonstrated the least marginal microleakage, and those in group B showed an intermediate level of marginal microleakage, and those in group A characterized the most serious marginal microleakage (total, χ2=44.610, P<0.01; among the different groups, P<0.05). The roughness experiment showed that specimens in group C achieve the smoothest results ([0.27±0.03] μm). Preparation shoulder polished using the dental pneumatic ultrasonic hand-piece demonstrated the best result under the SEM among the three groups.

CONCLUSIONSThe anti-microleakage effectiveness of dental pneumatic ultrasonic hand-piece in shoulder refinement is better than ordinary shoulder treatment.

Bicuspid ; Computer-Aided Design ; Crowns ; Dental Enamel ; Dental Instruments ; Dental Leakage ; diagnosis ; prevention & control ; Dental Polishing ; methods ; Dental Prosthesis Design ; methods ; Humans ; Pit and Fissure Sealants ; Random Allocation ; Resin Cements ; Ultrasonics ; Zirconium