[Accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional printing].

Objective: To compare the accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional (3D) printing fabricating, in order to provide some references for clinical practice. Methods: A maxillary edentulous jaw model made was used to duplicated 10 working casts. The casts were numbered and scanned. The wax pattern was designed by digital ways and conventional methods and then the denture bases were fabricated by injection molding, milling, and 3D printing. The tissue surface of experimental denture base was obtained using a dental laboratory scanner. The deviation between the tissue surface of the fabricated denture bases and the working model was evaluated. A digital force gauge was used to measure the traction force. Results: The milling group [(0.076±0.026) mm] was more accurate than the 3D printing group [(0.117±0.041) mm] (P<0.05) and the injection group [(0.120± 0.025) mm] (P<0.05). The accuracy of 3D printing group and that of injection group were not statistically significant (P>0.05). The milling group [(9.55±2.44) N] demonstrated greater retentive force than 3D printing group [(5.19±0.06) N] and injection molding group [(1.52±0.52) N] (P<0.05). Conclusions: The denture base fabricated by milling was more accurate and showed the greatest retentive force than the other groups. And 3D printing group showed better retentive force than the injection molding group. Both digital manufacturing methods can meet the requirements of clinical application.

The repair of critical-size defects with porous hydroxyapatite/polyamide nanocomposite: an experimental study in rabbit mandibles.

This study was conducted to evaluate the healing of critical-size surgical defects after implantation of porous nano-hydroxyapatite/polyamide composite (nHA/PA) blocks based on a bilateral mandible model using adult New Zealand white rabbits. 15 rabbits were divided randomly into three groups according to the observation period: 4, 12 and 24 weeks. The defects on one side were implanted with nHA/PA blocks and the contralateral defects were kept empty as blank controls. A combination of macroscopic, radiographic, histological and histomorphometric studies were performed up to 24 weeks postoperatively and compared with normal healing. Large amounts of callus and active osteoblasts were found in the pore structure after 4 weeks of implantation, and the defects were completely occupied by neo-bone with density comparable with that of host bone at 24 weeks. Significant difference was found between nHA/PA groups and blank controls regarding X-ray opacity over the whole period and bone parameters at 4 weeks postoperation (P<0.05). The porous nHA/PA composite promotes bone formation over the extension of the defect, particularly in the early stage. Porous nHA/PA offers interesting potential for maxillofacial reconstructive procedures in load-free areas.