Biocompatibility of 4-META/MMA-TBB resin used as a dental luting agent.

STATEMENT OF PROBLEM: The bonding and biological properties of currently used luting/cementing materials need to be improved. 4-Acryloyloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butylborane (4-META/MMA-TBB) resin is primarily used for splinting mobile teeth or treating fractured teeth. It undergoes moisture-resistant polymerization and bonds strongly to dentin and metals. PURPOSE: The purpose of this in vitro study was to compare the biological and biochemical properties META/MMA-TBB resin with those of conventional polymethyl methacrylate (PMMA)-MMA resin and other currently used luting materials in order to determine whether it may be a viable dental luting agent. MATERIAL AND METHODS: The degree of polymerization of 4-META/MMA-TBB resin, PMMA-MMA autopolymerizing resin, 10-methacryloyloxydecyl dihydrogen phosphate-dimethacrylate (MDP-DMA) adhesive resin, and a glass ionomer cement was measured by Fourier-transformed infrared spectroscopy. Free radical production during setting was evaluated by electron spin resonance (ESR) spectroscopy. Rat dental pulp cells cultured on these materials were examined for cell viability, attachment, proliferation, and functional phenotype. RESULTS: The degree of polymerization of 4-META/MMA-TBB resin was 82% thirty minutes after preparation, compared to 66% for PMMA-MMA autopolymerizing resin. ESR spectroscopy revealed free radical production from 4-META/MMA-TBB resin and glass ionomer cement was equivalent 24 hours after preparation, with no spike in radical generation observed. In contrast, free radical production from PMMA-MMA and MDP-DMA adhesive resins was rapid and sustained and 10 to 20 times greater than that from 4-META/MMA-TBB. The percentage of viable dental pulp cells 24 hours after seeding was considerably higher on MDP-DMA and 4-META/MMA-TBB resin than on glass ionomer cement. Cell number, proliferation, and alkaline phosphatase activity were highest on 4-META/MMA-TBB resin and lowest on the glass ionomer cement. CONCLUSIONS: 4-META/MMA-TBB resin is at least as biocompatible, and perhaps even more biocompatible, than other current luting materials, with fast, favorable, and nontoxic polymerization properties. Further in vivo and human studies of 4-META/MMA-TBB resin as a dental luting agent are warranted.

Early-stage osseointegration capability of a submicrofeatured titanium surface created by microroughening and anodic oxidation.

OBJECTIVE: The role of nanoscale/submicron morphological features in the process of osseointegration is largely unknown. This study reports the creation of a unique submicrofeatured titanium surface by a combination of anodic oxidation and sandblasting and determines how the addition of this submicrofeature to a microroughened surface affects the early-stage process of osseointegration. MATERIALS AND METHODS: Nonmicroroughened implants were prepared by machining Ti-6Al-4V alloy in a cylindrical form (1 mm diameter and 2 mm long). Microroughened implants were prepared by sandblasting machined implants, while submicrofeatured implants were created by anodic oxidation of the sandblasted implants. Implants were placed into rat femurs and subjected to biomechanical, interfacial, and histological analyses at 1 and 2 weeks post-implantation (n = 6). RESULTS: The submicrotopography was characterized by 50-300 nm nodules and pits in addition to other submicron-level irregularities formed entirely within the sandblast-created microstructures. The biomechanical strength of osseointegration increased continuously from week 1 to 2 for the submicrofeatured implants but not for the microroughened implants. A significant increase in bone-implant contact and bone volume, as well as a reduction in soft tissue intervention, were commonly found for the microroughened surface and the submicrofeatured surface compared with the nonmicroroughened surface. However, there were no differences in these parameters between the microroughened surface and the submicrofeatured surface. An extensive area of bone tissue at the submicrofeatured implant interface was retained intact after biomechanical shear testing, while the microroughened implant-tissue interface showed a gap along the entire axis of the implant, leading to clear separation of the tissue during the shear procedure. CONCLUSIONS: This study demonstrates that a submicrofeatured titanium surface created by a combination of sandblasting and anodic oxidation enhances the strength of early-stage osseointegration, primarily because of the increased resistance of peri-implant bone tissue against external force rather than modulation of bone morphogenesis.

Anatomy and lignin distribution in reaction phloem fibres of several Japanese hardwoods.

BACKGROUND AND AIMS: Although tension wood formation and the structure of gelatinous fibres (G-fibres) have been widely investigated, studies of the influence of the reaction phenomenon on phloem fibres have been few and incomplete in comparison with those of xylem wood fibres. This study was undertaken to clarify the influence of stem inclination on phloem fibres using several Japanese hardwood species that produce different G-fibre types in tension wood. METHODS: Eight hardwood species were inclined at 30-45° at the beginning of April. Specimens were collected in July and December. The cell-wall structure and lignin distribution of phloem fibres on both the tension and opposite sides were compared by light microscopy, ultraviolet microscopy, confocal laser scanning microscopy after staining with acriflavine, and transmission electron microscopy after staining with potassium permanganate. KEY RESULTS: Three types of changes were found in tension-side phloem fibres: (1) increases in the proportion of the syringyl unit in lignin in the S(1) and S(2) layers and compound middle lamella (Cercidiphyllum japonicum), (2) formation of unlignified gelatinous layers (Melia azedarach and Acer rufinerve) and (3) increases in the number of layers (n) in the multi-layered structure of S(1) + S(2) + n (G + L) (Mallotus japonicus). Other species showed no obvious change in cell-wall structure or lignin distribution. CONCLUSIONS: Phloem fibres of the tree species examined in our study showed three types of changes in lignin distribution and cell-wall structure. The reaction phenomenon may vary with tree species and may not be closely related to G-fibre type in tension wood.

Bone Generation Profiling Around Photofunctionalized Titanium Mesh.

PURPOSE: The aim of this study was to evaluate whether photofunctionalization of titanium mesh enhances its osteoconductive capability. MATERIALS AND METHODS: The titanium mesh (0.2 mm thickness) used in this study was made of commercially pure grade-2 titanium and had hexagonal apertures (2 mm width). Photofunctionalization was performed by treating titanium mesh with UV light for 12 minutes using a photo device immediately before use. Untreated or photofunctionalized titanium mesh was placed into rat femurs, and bone generation around titanium mesh was profiled using three-dimensional (3D) microcomputed tomography (micro-CT). A set of in vitro experiments was conducted using bone marrow-derived osteoblasts. RESULTS: Photofunctionalized titanium mesh surfaces were characterized by the regenerated hydrophilicity and significantly reduced surface carbon. Bone generation profiling at week 3 of healing showed that the hexagonal apertures in photofunctionalized mesh were 95% filled, but they were only 57% filled in untreated mesh, particularly with the center zone remaining as a gap. Bone profiling in slices parallel to the titanium surface showed that photofunctionalized titanium mesh achieved 90% bone occupancy 0 to 400 µm from the surface, compared with only 35% for untreated mesh. Bone occupancy remained as high as 55% 800 to 1,200 µm from photofunctionalized titanium mesh surfaces, compared with less than 20% for untreated mesh. In vitro, photofunctionalized titanium mesh expedited and enhanced attachment and spread of osteoblasts, and increased ALP activity and the rate of mineralization. CONCLUSION: This study may provide novel and advanced metrics describing the osteoconductive property of photofunctionalized titanium mesh. Specifically, photofunctionalization not only increased the breadth, but also the 3D range, of osteoconductivity of titanium mesh, enabling space-filling and far-reaching osteoconductivity. Further translational and clinical studies are warranted to establish photofunctionalized titanium mesh as a novel clinical tool for better bone regeneration and augmentation.

Effect of UV Photofunctionalization on Biologic and Anchoring Capability of Orthodontic Miniscrews.

PURPOSE: Treatment of titanium with UV light immediately before use, or photofunctionalization, is gaining traction as a simple method to improve the biologic capability and clinical performance of dental implants. The objective of this study was to examine the effect of photofunctionalization on the biologic capability and mechanical anchorage of orthodontic miniscrews. MATERIALS AND METHODS: Untreated and photofunctionalized Ti-6Al-4V orthodontic miniscrews were placed into rat femurs. Photofunctionalization was performed by treating miniscrews with UV light for 12 minutes using a photo device immediately before placement. After 3 weeks of healing, miniscrews were pushed laterally to measure the resistance against the tipping force. The miniscrews were also evaluated for morphology and chemistry of tissue formed around them using scanning electron microscopy and energy dispersive spectroscopy. Rat bone marrow-derived osteoblasts were cultured on Ti-6Al-4V disks with and without photofunctionalization. The number of osteoblasts attached to the disks and the behaviors, alkaline phosphatase activity, and mineralization capability of osteoblasts were evaluated. RESULTS: Photofunctionalization converted both disk and screw surfaces from hydrophobic to superhydrophilic. In vivo biomechanical testing showed that the displacement of untreated screws was 1.5 to 1.7 times greater than that of photofunctionalized screws when subjected to lateral tipping force. Robust bone formation was observed around photofunctionalized miniscrews with strong elemental peaks of calcium and phosphorus, whereas the tissue around untreated miniscrews appeared thin and showed no clear peak of calcium. The attachment, initial spreading, adhesion, and expression of functional phenotypes of osteoblasts were significantly increased on photofunctionalized Ti-6Al-4V disks. CONCLUSION: These in vivo and in vitro results comprehensively and consistently demonstrate that photofunctionalization increases the bioactivity of Ti-6Al-4V and improves the anchoring capability of orthodontic miniscrews.