Objective:To investigate the application of cast porcelain onlays in the restoration of short-crown molar defects.Methods:A total of 72 patients with short-crown molar defects admitted from 2023.01 to 2025.01 were randomly divided into two groups(n=36 each).The control group received zirconia all-ceramic crown restoration,while the observation group received cast porcelain onlay restoration.The excellent and good rates of restoration integrity,marginal fit,and proximal contact points,as well as masticatory function and restoration detachment rate,were compared between the two groups.Results:The excellent and good rates of restoration integrity,marginal fit,and proximal contact points were higher in the observation group than in the control group,but without statistical significance(P>0.05).After treatment,masticatory efficiency and bite force increased in both groups(P<0.05).The restoration detachment rate was 2.78% in the observation group, lower than 16.67% in the control group(P<0.05). Conclusion: For patients with short-crown molar defects,cast porcelain onlay restoration can better restore masticatory function while ensuring restoration integrity,marginal fit,and proximal contact quality,and is associated with a lower risk of restoration detachment.