The Accuracy Of Occlusal Contacts Of All-ceramic Single Crown Designed By Virtual Articulator From CAD/CAM System:The Preliminary Evaluation

Objective:Comparing the static and dynamic occlusion of single all ceramic crown designed by the mechanical and virtual articulator,initially evaluate the accuracy of virtual articulator and the feasibility of clinical application of CAD/CAM virtual articulator.Methods:The molars of the 9 subjects were selected as study object.After facebow transferring and obtaining occlusal records,The three-dimensional digital model of the full arch dentition was scanned using 3shape intraoral scanner before tooth preparation.After preparation of a full crown for the lower molar,impressions of the complete jaws were taken with addition-curing silicone,poured out with type IV gypsum,then mounted on a mechanical Artex-CR articulator,digitalized with ceramill CAD/CAM system.2 zirconia crowns were designed with Ceramill mind system by traditional CAD/CAM mothod and using virtual articulator respectively,and scanned by intraoral scanner to obtain digital models of full arch dentition after temporarily fixed.Use Geomagic qualify reverse engineering software to compare the two paired groups of scanned data after restorations generated in different modes with the original natural tooth data for 3D comparison.Occlusion evaluation including occlusal contact area,contact number,disocclusal time,and the percentage peak of protrusive and lateral occlusal force was compared and analyzed.Results:1.The number of occlusal contacts of subjects' tooth showed no significant difference among preoperation group,virtual group and mechanical group(p>0.05),but in rhe rest dentition and full dentition the number of occlusal contacts of mechanical group is significantly less than that in preoperation group(rest dentition p=0.020,p<0.05;full dentition p=0.020,p<0.05)at maximum intercuspal position,while there is no significant difference between Preoperation group and virtual group as well as virtual group and mechanical group(p>0.05).2.The areas of occlusal contacts showed no significant difference between preoperation group and virtual group(p>0.05),but mechanical group showed significantly less than that in preoperation group(p=0.014,p<0.05)at maximum intercuspal position.the overlapped contact areas between preoperation group and virtual group were significantly more than that between preoperation group and mechanical group(p=0.036,p<0.05).3.The protrusive and lateral(working side and non-working side)disocclusal time of virtual group was less than that of mechanical group,but there is no significant difference between the two groups(p>0.05).4.The central,protrusive and lateral(working side and non-working side)occlusal force percentage peak of virtual group was less than that of mechanical group,but there is no significant difference between the two groups(p>0.05).Conclusion1.The intercuspal occlusion recovery of virtual group is more similar to preoperation group than that of mechanical group.2.The central,protrusisve and lateral(working side and non-working side)occlusion showed no significant difference between virtual group and mechanical group,but it can be inffered that virtual articulator is not inferior to mechanical articulator for the occlusal surface design of posterior all ceramic single crown.