Study On The Influence Of Different Surface Treatments On Adhesion And Marginal Microleakage Of CAD/CAM Ceramics

Objectives:In this study,the effects of HF acid etching,Er:YAG laser,Nd:YAG laser and sand blasting on the surface morphology,bonding properties,fracture mode and microleakage of three CAD/CAM ceramics（Celtra Duo,LAVA Ultimate and CEREC Blocs）were compared,so as to provide some reference basis for clinical application.Methods:A total of 180 complete caries free isolated molars were collected,105 in the bonding group（n=7）and 75 in the microleakage group（n=5）.Three kinds of CAD/CAM ceramics（Celtra Duo,LAVA Ultimate and CEREC Blocs）were cut into 2×2×5 mm specimens.Each kind of ceramic was randomly divided into 5 groups（n=15）according to different surface treatments,and the following treatments were carried out respectively:Group C（no treatment）;HF group（4.5% HF acid etching）;NY group（Nd:YAG laser irradiation）;EY group（Er:YAG laser irradiation）;GB group（sand blasting）.The surface morphology of the treated ceramics was observed.The porcelain block was bonded to the dentin with resin adhesive（Variolink N）and the SBS and fracture mode of the bonding group were measured.In the microleakage group,the adhesive specimen was soaked in methylene blue solution for 24 hours after 5000 cycles（5 ℃-55 ℃）,and the microleakage depth was observed under the stereomicroscope.The data of SBS and microleakage were statistically analyzed by SPSS software（p<0.05）.Results:1.SEM results showed that the three groups of ceramics showed different micro morphologies after four different surface treatments.Compared with the control group,the treated ceramic surface became rough obviously,while the ceramic surface of the control group was relatively smooth and flat.2.The SBS of the treatment group were higher than the control group of the same kind of ceramics after different surface treatments（p<0.05）.For Celtra Duo group,EY group（16.73 MPa）>NY group（16.22MPa）>HF group（15.07 MPa）,（p>0.05）.For LAVA Ultimate group,GB group（17.48 MPa）>EY group（16.82 MPa）>NY group（14.48 MPa）,（p>0.05）.For CEREC Blocs group,EY group（17.64 MPa）>GB group（17.32 MPa）>NY group（16.93 MPa）,（p>0.05）.3.The fracture mode results show that the control group were adhesive failure,while the treatment group was mainly mixed failure.4.The microleakage of the treated specimens was much smaller than that of the untreated specimens,and the results were statistically significant（p<0.05）,but the microleakage of each group was no significant difference was found after the same treatment（p>0.05）.Conclusions:This study confirmed that surface treatment can improve the bonding strength of prosthesis,reduce the depth of microleakage and prolong the service life.Different surface treatments will produce different treatment effects due to the types of ceramic.This experiment selected the best surface treatment method for different kinds of CAD/CAM ceramics,which provided a reference basis for clinical application.