[Quantitative evaluation of fabricating complete denture by computer numerical control in manufacturing dentition and baseplate separately plus adhesive molding].

OBJECTIVE: To quantitatively evaluate the assembly precision of fabricating complete denture by computer numerical control (CNC) in manufacturing dentition and baseplate separately plus adhesive molding.

METHODS: The 3D surface data of a standard edentulous maxilla plaster cast model and the temporary base-plate were obtained using an Activity 880 3D scanner. The data (data1) of a complete denture were designed using a set of computer aided design (CAD) software developed by the research group of this study. The pins without undercut were designed as 3D shape of the joining area of the dentition and the baseplate by using the software of Imageware 13.2 and Geomagic Studio 2013. Zero in the top and 0.05 mm in the rest surfaces of the retention pins were set for adhesive clearance. Zenotec T1 (5-axis milling machine) was employed to manufacture polymethyl methacrylate (PMMA) dentition and baseplate. Double sides posterior and one anterior "union teeth" were got. The teeth were inserted into the retention pins in the baseplate and cemented with self-curing resin (Huge Dental Material Co., Ltd). The denture was scanned with the 3D scanner to obtain dataset Data4. Data2 and Data3 registration was set in Data4, Data2 and Data3 were united to gain Data 5. The adhesive clearance on the top of the retentional pins was measured, which was originally designed into 0 mm, and the assembly precision of dentition and baseplate obtained.

RESULTS: The average clearance measurements between the dentition and the baseplate: left molar teeth (0.44±0.04) mm, max 0.52 mm, min 0.29 mm; right molar teeth (0.52±0.07) mm, max 0.64 mm, min 0.28 mm; anterior teeth (0.60±0.10) mm, max 0.81 mm, min 0.40 mm; total average clearance (0.52±0.10) mm.

CONCLUSION: The adhesive clearance can be controlled to the level of 0.5 mm when the joining part of the artificial teeth and the base was designed into the shape of retentional pins and the artificial dentition divided into 3 parts. We succeeded in using the CAD/ computer aided manufacturing (CAM) technology to fabricate the complete denture. Although the assembly precision of the dentition and the baseplate is not perfect, the results have proved that the technical routes are workable.