Objective:To compare the clinic efficacy of two impression methods in producing all-ceramic onlays. Methods:Totally 80 patients after molar root canal therapy were randomly divided into two groups. Patients in one group were treated by intra-oral digital impression to produce onlays while those in the other group were treated by silicone rubber impression to produce onlays. The time and the comfort degree of patients when getting impressions were recorded. A week later

the onlays on teeth were fixed and the adaptation degree and the time of adjusting were recorded. A comparative study was made between the two groups. Results:Less time was required in intra-oral digital impression than silicone rubber impression(P<0.05). Patients felt more comfortable when using intra-oral digital impression than silicone rubber impression(P<0.05). There was not obvious difference in adaptation degree of onlays and adjusting time(P >0.05). Conclusion:Intra-oral digital impression is fast and convenient. It can improve the comfort degree of patients. Intra-oral digital impression is of good precision and up to the clinic standard. It should be applied widely in the restoration of tooth defect.