Experimental Study On The Influence Of Restoration Materials And Thicknesses On The Fracture Resistance Of Occlusal Veneers Made From Chair-side CAD/CAM Ceramic Blocs

Objective:This study was to evaluate the influence of four restoration materials and two thicknesses on the fracture resistance of occlusal veneers made from chair-side CAD/CAM ceramic blocs.It provided theoretical basis for the clinical application of new porcelain materials and the design and manufacture of minimally invasive restoration.Methods:Forty recently extracted intact and single-rooted human maxillary premolars for orthodontic reason were collected,simulating the severe abrasion tooth preparation of occlusal surface defect.The specimens randomly divided into 8 groups?n=5?,respectively using IPS e.max CAD?Group A?,Vita Suprinity?Group B?,Vita Enamic?Group C?and 3M Lava Ultimate?Group D?materials to manufacture occlusal veneers of 0.3mm thickness?Group A₁/B₁/C₁/D₁?and 0.6mm thickness?Group A₂/B₂/C₂/D₂?.After cementing with Variolink N resin adhesive,static loading test was performed on each specimen until cracked using an electronic universal experimental machine.Fracture strength loading values were recorded and fracture patterns were observed.The data were statistically analyzed using IBM SPSS Statistics 21 software package.Results:1.The fracture load values of each group of specimens were,A₁:592.132±171.750N,A₂:906.514±110.225N,B₂:997.194±237.795N,C₁:733.794±200.316N,C₂:726.522±131.157N,D₁:1045.854±244.751N,D₂:1131.786±214.549N?2.Restoration materials and thicknesses had effect on the fracture strength of occlusal veneers,and there were interactions between the two factors?P=0.000?.Group D₂ had the largest flexural load value.In the same material groups with different thicknesses,the flexural load value of Group A₂ was larger than Group A₁?P=0.009?,while there was no statistical difference between samples of different thicknesses of Group C and Group D.Among the samples of different materials with a thickness of 0.3mm,Group D₁ was the largest?P=0.005,P=0.035?,while there was no statistical difference between Group A₁ and Group C₁.Among the samples of different materials with a thickness of 0.6mm,Group B₂ was larger than Group C₂?P=0.032?,Group D₂was larger than Group C₂?P=0.003?,while there was no statistical difference between the samples of other materials?P>0.05?.3.Compared with Group A and Group B,the fracture mode grade of Group C and Group D specimens seemed lower?P=0.030?,and more limited to the restoration itself.Conclusion:1.Restoration materials and thicknesses have influence on the fracture resistance of occlusal veneers.2.Thickness of 0.3 mm occlusal veneers of IPS e.max CAD?Vita Enamic?3M Lava Ultimate materials can meet the needs of the flexural strength in vitro.3.Compared with enhanced glass ceramic IPS e.max CAD and Vita Suprinity materials,porcelain-resin composite ceramic Vita Enamic and 3M Lava Ultimate materials are more suitable for minimally invasive ultra-thin occlusal veneers,and the Lava Ultimate material has excellent fracture resistance.4.It is feasible to use IPS e.max CAD?Vita Suprinity?Vita Enamic and3M Lava Ultimate materials for manufacturing occlusal veneers to restore the severe abrasion tooth.