The Fundamental And Clinical Research On Metal-porcelain Bond Strength And Fit Of Titanium Crowns Fabricated By SLM 3D Printing

Selective laser melting(SLM) is an an important part of Laser rapid forming(LRF)technology. Compared with the traditional casting methods, SLM offers several advantages, it is possible to manufacture up to 100% relative density of dental products with high precision, high degree of automation, the human factor is small, the processing time is short and low processing costs.Currently, there are less study about SLM using for titanium prosthesis, more research is needed to support whether this technology could be applied to clinical practice.Various factors could influence the clinical application including fit and the mismatch of CET between titanium and porcelain. In particular,fit is most important with regard to the satisfactory functioning of FDPs in the oral cavity and to their longevity. And CET is the key factor to determine whether SLM could be used for the titanium-porcelain restorations.In this study,we compared the marginal fit and internal fit of titanium fixed dental prostheses(FDPs) fabricated by the lost wax casting method or SLM to assess theaccuracy of SLM technology.Secondly,evaluating the bond strength between SLM made cp Ti and low-fusing porcelain. So as to provide the theoretical basis for application in the clinical of SLM.Method1. Ti specimens were made by selective laser melting(SLM), or by conventional lost-wax cast technique(LW). The Surface roughness and thermal expansion coefficient(CTE) of SLM Ti was evaluated. The bond strength of Noritake Ti22 porcelain fused to SLM Ti was analyzed with the three-point bending test.2. titanium crowns were fabricated by selective laser melting( SLM), or by conventional lost-wax cast technique( LW) respectively for 10 cases whose teeth need to be restored with fixed denture.The marginal and internal gaps of crowns were recorded by using a replica technique. Each silicon film was cut into 2 parts and the thickness of silicon layer was measured at ×100 magnification using a stereomicroscope,the data of marginal gap( MG) and internal gap( IG) were statistically analysed by ANOVA and SPSS statistical package version 17.0.Results1.The Surface roughness of SLM Ti before polishing(Ra) is 4.48?m,After polishing(Ra) is 1.32?m.The CTE of SLM Ti was 9.52xl0-6/?, The bond strength of SLM Ti fused to Noritake Ti22 porcelain was(35.19± 2.77 MPa),no significant difference between cast Ti(36.73± 1.40MPa)(P>0.05), and above the lowest limit value in the IS09693 standard(25MPa).2.The MG and IG(?m) of titanium crowns in SLM group were 90.6±14.7 and213.7±90.4.1,in LW group 94.7±21.9 and 217.0±97.7.The MG of SLM titanium crowns is smaller than that of LW ones(P<0.05).There was no significant difference in the LW between the two groups(P>0.05).ConclusionThe Surface roughness and the bond strength of SLM Ti fused to Noritake Ti22 porcelain have no significant difference between cast Ti,and above the lowest limit value in the IS0 9693 standard.The marginal fit of the SLM group appeared slightly superiorcompared to that of the conventional LW method and significantly smaller than 120?m clinical generally accepted standard.So the SLM system can satisfy the clinical requirements.