Henry H. Takei’s research while affiliated with University of California, Los Angeles and other places

Background: Enamel matrix derivative (EMD) is widely used for regeneration therapy in dental clinical situations, but the mechanism of EMD bioactivity remains obscure. To clarify this mechanism, we focused on the formation of connective tissue and blood vessels. The aim of this study was to confirm whether EMD induces the formation of connective tissue and blood vessels by using the diffusion chamber (DC) technique. Materials and methods: Individual DCs containing EMD (DC-EMD) or propylene glycol alginate (PGA) were implanted subcutaneously in rat dorsum. At 4 weeks after the implantation, histological analysis of DCs was performed using azan staining. Results: DC-EMD induced the formation of much larger amounts of connective tissue containing abundant blood vessels than did DC-PGA. Conclusion: The results indicated that EMD can induce the formation of both connective tissue and blood vessels. This bioactivity may contribute to the mechanism whereby EMD induces tissue regeneration.

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Background/aim: Enterococcus faecalis is responsible for most cases of endodontic treatment failure. Despite various conventional disinfection methods, root canals are not completely free of microorganisms. Photodynamic therapy (PDT) is a new antimicrobial strategy that involves the use of a non-toxic photosensitizer (PS) and a light source. The aim of this study was to evaluate the antimicrobial effect of PDT using diode laser and pyoktanin blue (PB) and confirm the nontoxicity of PB as a PS. Materials and methods: Laser irradiation with an output power of 3 W was performed with PB as the PS to a bacterial solution containing E. faecalis. Then, the number of colony-forming units was counted. PB cytotoxicity was also assessed by the MTT assay. Results: E. faecalis counts were reduced after laser irradiation, laser irradiation with PB, or the combination thereof compared to the control, non-irradiation or water. The 50% cytotoxic concentration value for adult human dermal fibroblasts incubated with PB for 1 min was 108 μg/ml. Conclusion: Diode laser irradiation in combination with PB as the PS is efficacious for the elimination of E. faecalis without toxic effects to human dermal fibroblasts. This strategy might be useful for root canal irrigants.

The surface topography of implant fixture is an important factor affecting the osseointegration. We herein demonstrated the effects of surface microtopography of titanium disks on proliferation and differentiation of osteoblast-like cells isolated from rat calvariae. Titanium disks with machine surface (MS), rough surface (R1) and rough surface combined with small cavities (R2) were used in an in vitro culture system. Rough surfaces (R1 and R2 disks) induced stronger osteoblast proliferation and differentiation (BGP and sclerostin mRNA expressions and calcium content) than the smooth surface (MS disk). Furthermore, surface microtopography of R2 disk, which was rough with small cavities, more strongly induced cell proliferation and mineralized bone matrix production than R1 disk. Our results suggest that surface microtopography influences osteoblast proliferation and differentiation. R2 disk, which is rough with small cavities, may be used in implant fixtures to increase osseointegration.

Restoration of lost interdental papilla remains one of the most challenging goals for clinicians. When a single tooth is replaced with an implant, the papilla between the tooth and the implant can often be maintained or predictably reconstructed as long as the periodontal attachment and bone of the adjacent tooth is preserved. However, if the periodontal support is compromised on the neighboring natural tooth, the papilla will often be deficient or missing. This article presents a multidisciplinary treatment approach to regenerate the interdental papilla between an implant and a periodontally compromised tooth using surgical procedures and a customized abutment. Specifically, an abutment with modified subgingival contours is used to enhance support of the surgically reformed papilla.

Abstract The long-term clinical and esthetic success of an implant-supported restoration is determined by stable periimplant soft-tissue morphology that is in harmony with the surrounding tissue architecture of the natural dentition. In this case report, two minimally invasive surgical approaches were used to correct marginal soft tissue morphology around an implant and natural tooth. In a 45-year-old female, a fractured maxillary right central incisor associated with chronic periodontitis was extracted, and an implant fixture was placed. After the second-stage implant surgery, asymmetry was observed between the marginal tissues of the implant and left incisor. First, the clinical crown of the left maxillary central incisor was exposed 1 mm more by a flapless technique of crown lengthening, namely minimally invasive esthetic crown lengthening (MIECL). Next, a semilunar coronally positioned flap (SCPF) was performed to correct the high scalloped soft tissue architecture at the implant. Clinically, the surgeries resulted in satisfactory outcomes, with marginal tissues framing the implant and the left incisor in a harmonious manner. The soft tissue around the implant and the incisor has remained stable during the follow-up period (3 years). MIECL may makes it possible to achieve the desired free gingival margin position of the labial surface without changing the interdental marginal gingiva in a short healing period in esthetic areas. In addition, although the SCPF had been originally designed to cover denuded root surfaces in the natural teeth, this technique may also be applied to correct receded marginal soft tissues in implants.

Orthodontic extrusion of nonrestorable teeth has been used for almost 20 years as an alternative to bone grafting in preparation for implant placement. Although this technique predictably creates bone and soft tissue, and improves the socket diameter and depth, most of the bone apposition occurs in the marginal alveolar and periapical areas of the extruded tooth. To create more labial bone, the standard orthodontic extrusion technique was modified to apply pressure on the hopeless tooth both coronally and palatally, which allowed bone at the site to develop apically and labially. Gingival thickness on the labial aspect was also increased, and the tissue biotype was improved. A clinical treatment is presented that illustrates the use of this technique.