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Objective: To study the ability of patients with semantic dementia to understand actions, in order to examine the contribution of semantic memory to action comprehension. Methods: The ability to comprehend symbolic and instrumental actions was assessed in 6 patients with semantic dementia and 10 healthy controls. The patients were also given the imitation test of meaningful and meaningless actions. Results: In all patients with semantic dementia, comprehension of both symbolic and instrumental actions was defective. The comprehension of symbolic actions was more impaired than that of instrumental actions. Their ability to imitate other’s actions was well preserved. Conclusion: This study showed that comprehension of action was impaired in semantic dementia, suggesting that semantic memory has an important role in comprehension of human action.

Ideally, artificial bones should be dimensionally compatible with deformities, and be biodegradable and osteoconductive; however, there are no artificial bones developed to date that satisfy these requirements. We fabricated novel custom-made artificial bones from alpha-tricalcium phosphate powder using an inkjet printer and implanted them in ten patients with maxillofacial deformities. The artificial bones had dimensional compatibility in all the patients. The operation time was reduced due to minimal need for size adjustment and fixing manipulation. The postsurgical computed tomography analysis detected partial union between the artificial bones and host bone tissues. There were no serious adverse reactions. These findings provide support for further clinical studies of the inkjet-printed custom-made artificial bones.

Rapid prototyping (RP) is a molding technique that builds a three-dimensional (3D) model from computer-aided design (CAD) data. We fabricated new tailor-made bone implants (TIs) from alpha-tricalcium phosphate powder using an RP ink-jet printer based on computed tomography (CT) data, and evaluated their safety and efficacy. CT data of the skulls of seven beagle dogs were obtained and converted to CAD data, and bone defects were virtually made in the skull bilaterally. TIs were designed to fit the defects and were fabricated using the 3D ink-jet printer with six horizontal cylindrical holes running through the implants, designed for possible facilitation of vascular invasion and bone regeneration. As a control, hydroxyapatite implants (HIs) were cut manually from porous hydroxyapatite blocks. Then, craniectomy was performed to create real skull defects, and TIs and HIs were implanted. After implantation, CT was performed regularly, and the animals were euthanized at 24 weeks. No major side effects were observed. CT analysis showed narrowing of the cylindrical holes; bony bridging between the implants and the temporal bone was observed only for TIs. Histological analysis revealed substantial new bone formation inside the cylindrical holes in the TIs, while mainly connective tissues invaded the porous structures in HIs. Bone marrow was observed only in TIs. Osteoclasts were seen to resorb regenerated bone from inside the cylindrical holes and to invade and probably resorb the TIs. These data suggest that TIs are a safe and effective bone substitute, possessing osteoconductivity comparable with that of HIs.