This review highlights the morphology, neuroplasticity and regeneration of the periodontal Ruffini endings, essential mechanoreceptors in the periodontal ligament. The periodontal Ruffini endings are characterized by expanded axon terminals filled with a number of mitochondria and by the presence of terminal or lamellar Schwann cells. Many experimental studies have revealed that periodontal Ruffini endings have high potential for neuroplasticity, confirmed by intense immunoreactivity for several markers such as low affinity neurtropin receptor (p75-NGFR) and growth associated protein-43 (GAP-43) even in mature periodontal ligament. The periodontal Ruffini endings could regenerate by 14 days after injury of inferior alveolar nerve, faster than the Ruffini endings in other tissues. Previous immunocytochemical studies have shown expression of immunoreactivity for trkB, a high affinity neurotrophic factor receptor, in the periodontal Ruffini endings, suggesting brain derived neurotrophic factor (BDNF) is a candidate for neurotrophins involved in the regeneration of the periodontal Ruffini endings. Our recent immunocytochemical and quantitative analyses on BDNF-deficient mice have revealed the involvement of BDNF in the regeneration of the periodontal Ruffini endings. Further investigations are needed for clarifying the involvement of other neurotrophins and their molecular mechanism of the regeneration processes of the periodontal Ruffini endings.
The concept of minimal intervention dentistry has evolved as a consequence of our increased understanding of the caries process and the development of adhesive restorative materials. Recently, new concepts of treatments for dentin caries by use of adhesive resins and glass-ionomer cements have been proposed. However, new hard tissue, indicated as the result of applying calcium hydroxide or adhesive resins and/or sterilized by the mixed drugs, formed with a tunnel defect frequency present, running from the medicament interface to the pulp. These reports suggest the urgent necessity for us to the establishment of the biological dentin regeneration therapy like the Modified Sealed Restoration (MSR). In this review, we reported at first about “Resin adhesion to caries-infected dentin”, and then “Dentin regeneration therapy with growth factor (CTGF)” and “In vivo dentin regeneration by adhesive resin containing EVA+C” and finally “Future approaches to establish the dentin regeneration therapy”.
It was reported that the cationic ions are related to the adhesion behavior of integrin. Especially divalent cations such as Mg2+ ions play some role in cell adhesion. Thus, magnesium seems to be an important factor in controlling bone metabolism. Recently, scaffold biomaterials have been focused in the tissue engineering field. FGMgCO3Ap-collagen composite was made by mixing the functionally graded CO3apatite containing Mg with collagen. Modification of gradational Mg2+ ions on the apatite crystals promoted cell adhesion. Furthermore, as a scaffold material, the FGMgCO3Ap-collagen composite suggested contributing to bone formation. Mg2+ ions may contribute to the bone metabolism of osteoclast and osteoblast action with the integrins at their cell surfaces.
In the present study, we aimed to deposit thin calcium phosphate film onto titanium substrate using magnetron sputtering method. The hydroxyapatite target and tricalcium phosphate target were prepared by cold isostatic pressing method. When hydroxyapatite target was used, the crack was formed on the target material during the sputtering. The film thickness was increased according to the increase of the coating time. Heating the titanium substrate around 250°C produced tighter bonding between coated film and titanium, and also increased film thickness compared with no-heating of the titanium. After a 5-hr coating process, the thickness of the deposited film was approximately 0.10 μm when titanium substrate was heated. EPMA and FT-IR-RAS measurement reveled that the main component of coated film was calcium phosphate material. In conclusions, thin calcium phosphate film was deposited onto titanium using magnetron sputtering method.
We added two synthetic pyrimidine compounds to periodontal dressing materials and examined the increase in the area ratio of the tubule-like structure in vitro, in order to evaluate the effects on angiogenesis. Also, we examined the change in cell viability by adding these compounds. Both tests have shown that the level at which the formation of the tubule-like structure is facilitated is about 0.1 mM for both additives, and that at this level there were almost no effects on cell viability. Although the applicability of test periodontal dressing materials cannot be determined based solely on the results of this in vitro study, the application of these compounds to dentistry appears promising.
The purpose of this investigation was to examine the effects of medium type (α-MEM or DMEM); serum amount (5, 10 or 15%); and dexamethasone (Dex) induction (Dex (−) or Dex (+)) on the proliferation and alkaline phosphatase (ALP) activity of twice-passaged SD rat's bone marrow stromal cells. (1) After 6 days culture (before confluence), cell number and total protein concentration were measured. It was found that the serum amount played the dominant role in increasing the proliferation. (2) After 24 days culture (long after confluence), total protein concentration and ALP activity were measured. It was found that α-MEM was superior to DMEM in producing larger total protein concentrations. Incrementing the serum amount tended to the increase in total protein concentrations. Dex induction (Dex(+)) decreased values of ALP activity / total protein concentration, reflecting the advance of the osteogenic differentiation stage. The use of Dex (+) α-MEM medium was preferred to produce greater protein production with higher osteogenic differentiation level
The immobilization behavior of fibronectin onto plasma-surface modified titanium was evaluated by using the quartz crystal microbalance-dissipation (QCM-D) technique. The plasma-surface modifications included a thin-film coating of hexamethyldisiloxane (HMDSO) and an O2-plasma treatment on titanium. The contact angle of HMDSO-coatings against double-distilled water was 100 degrees, and dramatically decreased after the O2-plasma treatment with less than 5 degrees. XPS analysis indicated the introduction of an O2-functional group onto the HMDSO surface by the O2-plasma treatment. The QCM-D technique enabled evaluation the adsorption behavior of fibronectin. The largest amount of fibronectin adsorbed was on both as-coated HMDSO (hydrophobic surfaces) and O2-plasma treated at 10-min (hydrophilic surfaces) surfaces compared to O2-plasma treated (24-h) surfaces. These results indicated that two adsorption mechanisms of the fibronectin to substrates were considered, including hydrophobic interaction and ionic bond via OH group and/or O2-functional group concomitant with hydrophilic surfaces.
The use of dog teeth in vivo provides a useful screening model between in vitro tests and human clinical trials. In this experiment, the effects of post-insertion time on the structure and strength of resin-dentin bonds were evaluated. The purpose of this experiment was to determine the resin-dentin bond strengths in dog teeth in vitro vs. in vivo (immediate, 3 weeks and 3 months after restoration ), and to investigate the resin-dentin interfaces with scanning electron microscopy ( SEM ). Box-form Class V cavities were prepared into labial middle coronal dentin in 4 anesthetized beagle dogs. The teeth were bonded with Fluoro Bond ( FB, Shofu ) or Clearfil Liner Bond 2 ( LB, Kuraray ) and restored with Clearfil AP-X resin composite ( Kuraray ). The teeth were surgically removed immediately, 3 weeks or 3 months after restoration, serially sliced and trimmed to a surface area of 1mm2 for microtensile bond strength test (MTBS). For the in vitro study, extracted dog teeth were used. In vitro and in vivo immediate bond strengths of both adhesive systems were 33.7 to 36.3 MPa, which were not significantly different. In vivo bond strengths of both adhesive systems at 3 weeks and 3 months were significantly lower than those measured immediately in vitro or in vivo. SEM showed the formation of hybrid layers with both adhesive systems when tested immediately in vitro or in vivo, but after 3 month in vivo, hybrid layers could not clearly seen. The fall in bond strengths noted with time may have been due to occlusal stress, and the influence of oral or dentinal fluids on the morphology of the hybrid layers and resin tags.
OBJECTIVE: Using human amniotic membrane (AM), we developed a novel, cultured, mucosal epithelia and periodontal ligament (PDL)_cells sheet biomaterials from human oral epithelia and PDL cells for oral reconstruction. MATERIALS AND METHODS: Oral mucosal epithelia and PDL cells were cultivated on human AM carrier. Cultured human oral epithelia and PDL like cells were examined histomorphologically. RESULTS: After 2-3 weeks in culture, oral mucosal epithelial cells developed five to seven layers of stratified and well-differentiated cells. After 10 days in culture, PDL like cells showed a monolayered structure on AM. CONCLUSIONS: Oral mucosal epithelia and PDL like cells cultivation using AM enable sheet formation. These findings lead us to conclude that this novel oral epithelial sheet material will be a useful biomaterial for oral reconstruction in humans.
Tissue engineering therapy in dentistry now utilizes bio-absorbable scaffolds. By scanning electron microscopy (SEM), we observed structures of three commercial scaffold sponges made of collagen, poly-lactide and calcium phosphate for 3-dimensional (3D) cell culture and one commercial porous bio-absorbable tri-calcium phosphate block for bone-defect filling. It became clear that four samples had pores which ranged widely from approximately 100 to 650 μm and the pores were interconnected both in parallel and perpendicular directions.
Optimal bone filling materials that act as a scaffold for the repair of bone defects should possess, histocompatibility, and afford conduction of new bone formation without toxicity or allergic factors. In addition, the materials should ultimatedly be resolved and replaced by new bone. In this study, to develop new bone filling materials that promote bone formation and bone growth, we implanted coral in bone defects and observed the newly-formed bone by confocal laser scanning microscopy (CLSM). In 3 adult male beagles, bone defects were made in the right and left femora and tibiae under general anesthesia. These defects were either filled with coral blocks or left without any filling material. After 4 weeks, calcein was administered. One week later, the animals were euthanized under general anesthesia, and the femora and tibiae were removed and fixed in formalin. The specimens were divided into two portions: one is for CLSM observation and the other for histopathological observation. The formation of bone and bone marrow was seen in holes without filling, but only slight bone growth, i.e., increase in bone mass was seen. In the holes with coral filling materials, they were resorbed by giant cells. Furthermore, new bone and bone growth were noted, while lymphocyte infiltration was slight in all holes. Since resorption of the coral inserted into the bone defect was observed, we concluded that coral could be useful for bone regeneration.
Dentin phosphophoryn (DPP) is an acidic non-collagenous protein in dentin. In vitro, DPP induces apatite formation when immobilized to insoluble substrates such as type I collagen fibrils and agarose beads. In the present study, DPP purified from fresh bovine dentin was evaluated as a co-factor for recombinant human bone morphogenetic protein-2 (rhBMP-2) in rhBMP-2-induced bone formation in rats. Five micrograms of Escherichia coli-derived rhBMP-2 variant was adsorbed to composite of 50 mg of hydroxyapatite (HAP) with or without 1 mg of DPP. Next, rhBMP-2/HAP/DPP composite or rhBMP-2/HAP composite was implanted subcutaneously in 4-week-old Wistar rats. Rats were sacrificed at 2 and 3 weeks after implantation. Throughout the experimental period, rhBMP-2/HAP/DPP composite induced more bone formation than rhBMP-2/HAP composite. In the histomorphological analysis, bone induced by rhBMP-2/HAP/DPP composite accounted for 69 ± 17% (n=6) of the total composite while accounting for 45 ± 13% (n=6) of the rhBMP-2/HAP composite at 3 week postimplantation. These results indicate that the bone-inducing activity of rhBMP-2 is enhanced by DPP as a co-factor of rhBMP-2 in vivo.
Decorin, a small dermatan sulfate proteoglycan, binds to collagen, and is known to related to fibrillogenesis. To elucidate the fluctuation of decorin mRNA during the process of inflammation, we examined its expression in cultured human gingival fibroblasts stimulated by interluekin(IL)-1β. Matrix metalloproteinases (MMP)-3, type I collagen and IL-6 mRNA expression were also determined. The effects of IL-1β on the expression of decorin and type I collagen mRNA were similar to each other. Their mRNA expression levels compared with controls were increased with culture time up to 24 h, followed by a decrease to 48 h. Although the mRNA levels of MMP-3 and IL-6 were trace in controls, they increased markedly by stimulation of IL-1β. These results indicate that gingival fibroblasts stimulated by IL-1β actively express IL-6 mRNA as an early event of inflammation, followed by decorin, type I collagen and MMP-3, which are associated with collagen fibrils, in events coexisting with destruction and repair.