To compare the effects of different types of all-ceramic restorations on the preparation amount and bonding area of mandibular first molars. Methods Ten human mandibular first molars collected from May 2022 to May 2023 in our hospital were selected. Through Micro CT scanning and 3D reconstruction, four groups of samples were copied by 3D printing technology: study group 1 (all-ceramic crown), study group 2 (adjacent teeth all-ceramic inlay), study group 3 (MOD all-ceramic inlay) and control group (blank). These samples were prepared for different types of restorations according to the standard of tooth preparation. Then, the reverse engineering software Mimics and Geomagic Studio were used to measure and analyze the preparation of the restoration (the volume percentage of the grinded tooth tissue to the hard tissue of the crown) and the bonding area. Results The preparation amount in study groups 1, 2 and 3 was greater than that in the control group, and study group 3>study group 2>study group 1 (P <0.05). The bonding area of the study groups 1, 2 and 3 was larger than that of the control group, and the study group 3