Abstract: Objective To quantify and compare the volume of tooth preparation(the volume percentage of the tooth tissue prepared to the hard tissue of crown) and bonding area of mandibular first molar. Methods Ten extracted mandibular first molars were collected. The teeth were scanned by Micro CT, then reconstructed into 3D model and copied by 3D printing method into four groups（A、B、C、D）each with ten teeth，and the teeth were prepared with the following designs: ceramic crown（A1-A10），medial-occlusal cavity ceramic inlay（B1-B10）, and MOD ceramic inlay（C1-C10），D（D1-D10）was blank control group. Finally，the reverse engineering software Mimics and Geomagic Studio were applied to analyze the volume of tooth preparation and bonding area. Results Different designs of mandibular first molar were statistically significant in the volume of tooth preparation and the adhesive area. The volume of tooth preparation: ceramic crown (36.21%), medial-occlusal cavity ceramic inlay(5.75%), MOD ceramic inlay(11.93%); the bonding area: ceramic crown (169.96 mm2), medial-occlusal cavity ceramic inlay(40.27 mm2), MOD ceramic inlay(81.94 mm2); the enamel bonding area: medial-occlusal cavity ceramic inlay(26.55 mm2), MOD ceramic inlay(55.13 mm2), the dentin bonding area: medial-occlusal cavity ceramic inlay(12.92 mm2), MOD ceramic inlay(23.97 mm2), the enamel bonding area was more than dentin. Conclusions The volume of tooth preparation and bonding area are related to the type of dentures. The exposure of enamel identified at the margins of the ceramic inlays preparation suggests that enamel adhesions should be used.

Key words: mandibular first molar, all-ceramic crown, ceramic Inlay, volume of tooth preparation, bonding area.