The purpose of this article is to describe a newly developed 3D computer-aided design (CAD) system for the diagnostic set-up of casts in orthodontic diagnosis and treatment planning, and its preliminary clinical applications. The system comprises a measuring unit which obtains 3D information from the dental model using laser scanning, and a personal computer to generate the 3D graphics. When measuring the 3D shape of the model, to minimize blind sectors, the model is scanned from two different directions with the slit-ray laser beam by rotating the mounting angle of the model on the measuring device. For computed simulation of tooth movement, the representative planes, defined by the anatomical reference points, are formed for each individual tooth and are arranged along a guideline descriptive of the individual arch form. Subsequently, the 3D shape is imparted to each of the teeth arranged on the representative plane to form an arrangement of the 3D profile. When necessary, orthognathic surgery can be simulated by moving the mandibular dental arch three-dimensionally to establish the optimum occlusal relationship. Compared with hand-made set-up models, the computed diagnostic cast has advantages such as high-speed processing and quantitative evaluation on the amount of 3D movement of the individual tooth relative to the craniofacial plane. Trial clinical applications demonstrated that the use of this system facilitated the otherwise complicated and time-consuming mock surgery for treatment planning in orthognathic surgery.
Objective The development of biomaterials for secondary bone grafting to the alveolar cleft, recombinant human morphogenetic protein-2 (rhBMP-2) may have great potential to promote osseous regeneration. The purpose of this study was to investigate the osteoinductive activity of low-dose rhBMP-2 (10 μg/100 μL) and the biological response of newly generated bone to orthodontic stimulation, compared with previous results using high-dose rhBMP-2 (40 μg/100 μL). Method After extraction of the maxillary first premolars, bone defects were surgically created in eight adult beagle dogs using a 5-mm-diameter trepan bar. The rhBMP-2 with a PLGA/gelatin sponge complex (PGS) made of gelatin and polylactic acid polyglycolic acid copolymer was immediately implanted. The osteoinductive activity of rhBMP-2 and tooth movement into the newly generated bone was evaluated based on histological and morphometric examination. Results Dramatic histological and morphometric differences were found in the time course of bone remodeling between low- and high-dose rhBMP-2. The onset of bone remodeling occurred significantly earlier in low-dose rhBMP-2. During experimental tooth movement, in contrast to high-dose rhBMP-2, with which root resorption occurred, only partial cementum resorption occurred on the pressure side with low-dose rhBMP-2. Conclusion These results indicated that the proper dosage of rhBMP-2 should be determined for successful clinical application.
Objective The purpose of this preliminary study was to examine experimental tooth movement into newly generated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2). Method After extraction of the maxillary first premolars, bone defects were surgically created in eight adult beagle dogs using a 5-mm-diameter trepan bar. According to which material was grafted into the bone defects, animals were divided into the following four groups: (1) the rhBMP-2 group in which rhBMP-2 with a poly [D,L-(lactide-co-glycolide)]/gelatin sponge complex was implanted; (2) the spongiosa group in which spongiosa from the tibia was grafted; (3) the nongrafted group in which no material was embedded; and (4) the control group in which only tooth extraction was performed. The osteoinductive activity of rhBMP-2 and tooth movement into the newly generated bone were examined by histological and morphometric comparisons of each group. Results Considerable new bone formation was observed at the grafted site both in the rhBMP-2 and in the spongiosa groups. The area of generated bone in the rhBMP-2 group was significantly greater than that in the spongiosa group. Newly generated bone, in both the rhBMP-2 and spongisosa groups, showed a similar histological response to orthodontic force as in normal alveolar bone in the control group. However, root resorption occurred on the pressure side in the rhBMP-2 group. Conclusion These results indicated that rhBMP-2 might constitute an alternative material to autogeneous bone grafting for alveolar cleft defects. Further studies regarding tooth movement into generated bone induced by rhBMP-2 are suggested.
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