| PurposeThe purpose of this in vitro study was to evaluate the influence of different chamfers,manufacturing methods and burs on the marginal adaptation of Lithium disilicate crowns with less tooth preparation,and to provide references for clinical tooth preparation and the manufactured pattern.Material and methods40 maxillary premolars were collected and randomly divided into 6 groups,carbide burs for 135° chamfer(C135),carbide burs for deep chamfer(CDC),diamond burs for 135° chamfer and finishing(DP135),diamond burs for deep chamfer and finishing(DPDC),diamond burs for 135° chamfer without finishing(DN135),diamond burs for deep chamfer without finishing(DNDC),5 for each group except for C135,CDC,they are 10 in each group.DP135 and DN135 together as group D135,DPDC and DNDC together as group DDC.Group C135,DP135 and DN135 are prepared for 135°chamfer by carbide and diamond burs,Group CDC,DPDC and DNDC are prepared for deep chamfer by carbide and diamond burs separately,finishing DP 135 and DPDC with Fine-grained burs,the width of chamfer finish line is about 0.8mm.Three fabricated methods(CAD/CAM,3D printing combined with lost-wax hot pressing technique,lost-wax hot pressing technique)were used in each group to fabricate IPS e.max crowns.The marginal discrepancy were assessed in stereomicroscope(x50)by Silicone replica technique.Selecting 5 CAD/CAM crowns in each groups(C135,CDC)randomly.Bonding of 6 groups(DN135,DNDC,DP135,DPDC,C135,CDC)of CAD/CAM crowns with double curing resin adhesive(Variolink N,Ivoclar Vivadent).Fatigue loading(2HZ,50N,300000 times)and thermal cycling(10000 times,55?30s,5?30s)were proceed in turn,after dyeing 48h with 2%methylene blue,they were sectioned by low speed cutting machine,The depth of dye penetration were measured in stereomicroscope(x20).SPSS22.0 was used to analyze the data of each group.P<0.05 was statistically significant.Multifactor analysis of variance was used to deal with data,and multiple comparisons are compared with LSD.Results1.Marginal gap of all ceramic crownsThe marginal gap of all ceramic crowns fabricated by three manufacturing methods are less than 120?m,The maximum value appears in the group CDC(CAD/CAM,102.82?m),The minimum value appears in group C135(Press,39.47?m).2.Influence of different finish lines,manufacturing methods and burs on the marginal adaptation of all ceramic crownsInfluence of different finish lines(P=0.598)and burs(P=0.938)have no significant difference on marginal adaptation in all ceramic crowns.Influence of different manufacturing methods(P=0.002<0.05)has significant difference on marginal adaptation in all ceramic crowns.The LSD test shows that there is a statistical difference between each other(P<0.05),of which CAD/CAM is 73.95±11.38?m,3D printing combined with lost-wax hot pressing technique is 67.29±9.38?m,lost-wax hot pressing technique is 58.48±11.47?m.3.Influence of different finish lines and burs on microleakage of CAD/CAM all ceramic crownsInfluence of different finish lines(P=0.069)have no significant difference on marginal microleakage in all ceramic crowns.Influence of different burs(P=0.000<0.05)have significant difference on marginal microleakage in all ceramic crowns.The LSD test shows that the microleakage depth of diamond burs(0.548±0.19mm)is significant greater than fine-grained diamond bur(0.276±0.09mm)and carbide burs(0.197±0.05mm).Conclusion1.The marginal gap of all ceramic crowns fabricated by three manufacturing methods is less than 120 ? m,which is clinically acceptable.2.Different prepared burs on tooth preparation have no influence on the marginal adaptation of CAD/CAM crowns,CAD/CAM milling machine can meet less tooth preparation with the width of finish line is 0.8mm.3.The marginal adaptation of 3D printing combined with lost-wax hot pressing technique fabricated crowns is better than CAD/CAM fabricated crowns.4.With same resin binder,the microleakage depth of diamond burs is greater than fine-grained diamond bur and carbide burs. |
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