Ultrastructure of the interface between titanium and surrounding tissue in rat tibiae--a comparison study on titanium-coated and -uncoated plastic implants

Purposes The purposes of this study were to prepare experimental titanium‐coated plastic implants suitable for electron microscopy examination of the titanium‐bone interface and the response of tissue surrounding titanium, and to histologically compare surrounding tissue responses in coated and uncoated implants. Materials and Methods Experimental plastic implants were prepared from a plastic rod coated with a thin film of titanium. Plastic implants without coatings were used as controls. The implants were placed into tibiae of 10‐week‐old male rats. The specimens with implants were harvested 4 weeks after placement and observed under a light microscope, a transmission electron microscope, and a scanning electron microscope. Results In the transmission electron microscopy, the titanium layer of the experimental implant was a uniform layer that was approximately 150‐ to 250‐nm wide. The new bone formation was observed around both titanium‐coated implants and plastic implants. However, there was no direct bone contact with the plastic implant. Discussion The responses of tissue surrounding the experimental implants varied. Under an electron microscope, the following areas were observed: (1) an area with a direct contact between the titanium and bone, (2) an area at the interface where an amorphous layer was observed, (3) an area with progressing calcification in the surrounding tissue where the cells were adjacent to the titanium surface, and (4) an area in which bone resorption and apposition were observed and remodeling was thought to be occurring. Conclusion The experimental titanium was homogenous and was considered to be highly useful in observing the responses of the surrounding tissue to the titanium surface.     

Calcification at the interface between titanium implants and bone: observation with confocal laser scanning microscopy

It has not been previously possible to observe bone formation in undecalcified sections with titanium implants at high magnification because of the difficulty in sectioning bone together with implants. A method for examining the bone-implant interface in undecalcified sections is described in which implants are left in situ and confocal laser scanning microscopy (CLSM) is used to examine both the implant surface and adjacent bone. Pulsing of animals at different times with the fluorescent dyes calcein and alizarin red permitted assessment of temporal patterns of bone formation by CLSM. Reflectivity of the polished implant surface permitted accurate assessment of the position of the implant relative to labeled bone. The analysis showed that bone first formed as thin processes towards and across the implant surface, followed by further bone formation behind these processes. The interface between calcified bone tissue and the implant surface was characterized by a 10-microm space. The CLSM technique enabled detailed observations of new bone formation at the titanium implant interface.     

Quantitative study on the interface between bone tissue and Blade-vent implants using the image processing system

Undecalcified histopathologic sections of two titanium blade-vent implants (which had survived for five years in a dog) were made, and image analyses of the bone-implant interface were determined. One implant was inserted conventionally in the right mandible, and the other was inserted shallower than usual in the left mandible, so that the shoulder was located at the same level as the residual bone ridge. Using an image analysis technique, we observed, on the deeper implant, a 0-56% rate of bony contact around the implant and a 71-84% rate of bone-vent occupancy in the vents. With the shallower implant, a 0-46% rate of bony contact and a 26-60% rate of bone-vent occupancy were observed. When the two implants were compared, the deeper implant showed relatively higher bony contact and bone-vent occupancy than its less-submerged control in the five-year study.     

Differences between the bony interfaces of titanium and hydroxyapatite-alumina plasma-sprayed titanium blade implants

Histopathologic study was done to reveal the difference of bony interface in the mandibular bone between titanium blade implants and titanium implants coated with the mixture of hydroxyapatite-alumina by the plasma-spray technique, using the improved undecalcified histologic technique and the image analyzing system. In 4 adult shepherd dogs, the implantation was performed in the molar region of the mandible 2 months after tooth extraction. The coated implants and the non-coated ones were inserted respectively in the mandibles. They were sacrificed on the 5th, 7th, 14th and 28th day postoperatively. In 5-day implant after insertion, granulation tissues or fibrous connective tissues were observed around both implants in bone tissues. In 7-day implant, osteoid tissues regenerated around the apex of both implants, but attached a little to them. In 14-day implant, osteoid tissues or woven bone regenerated around both implants and attached more to the coated implant (approximately 13.7%) than the non-coated one (approximately 6.0%). In 28-day implant, regenerative woven or lamellar bone attached much more to the coated implant (approximately 63.4%) than the non-coated one (approximately 8.8%). Bony interface increased remarkably in the coated implants, chronologically. The results showed that the plasma-sprayed hydroxyapatite-alumina coating was effective for the initial fixation of endosseous dental implants.     

Bioengineered periodontal tissue formed on titanium dental implants

The ability to use autologous dental progenitor cells (DPCs) to form organized periodontal tissues on titanium implants would be a significant improvement over current implant therapies. Based on prior experimental results, we hypothesized that rat periodontal ligament (PDL)-derived DPCs can be used to bioengineer PDL tissues on titanium implants in a novel, in vivo rat maxillary molar implant model. Analyses of recovered implants revealed organized PDL tissues surrounding titanium implant surfaces in PDL-cell-seeded, and not in unseeded control, implants. Rat PDL DPCs also exhibited differentiative potential characteristic of stem cells. These proof-of-principle findings suggest that PDL DPCs can organize periodontal tissues in the jaw, at the site of previously lost teeth, indicating that this method holds potential as an alternative approach to osseointegrated dental implants. Further refinement of this approach will facilitate the development of clinically relevant methods for autologous PDL regeneration on titanium implants in humans.     

Microscopic observations of the bone/implant interface of surface-treated titanium implants.

Light microscopy, and transmission and scanning electron microscopy were used to evaluate osseointegration of extraoral titanium implant surfaces treated by either autoclaving, exposure to ultraviolet light (UV), or radiofrequency glow discharge (RFGD). Ultraviolet and RFGD-treated implants showed faster healing in the initial 5-week to 3-month period. By 6 months of healing, no structural differences were found at the bone/implant interface among the different treatments. It was concluded that UV or RFGD surface treatment of titanium implants may shorten the time interval between placement and loading.     

Interface between titanium 6,4 alloy implants and bone

This paper presents the results of animal studies on the interface between 6 aluminum, 4 vanadium, titanium alloy and bone. 7 New Zealand white rabbits were anaesthetised and a new design of threaded implant inserted into the tibial metaphysis of each leg. 3 further animals had fine lathe turnings inserted in the same site. The animals were sacrificed 7 weeks later and the implants removed together with the surrounding bone. After suitable processing of the specimens, they were subjected to scanning and transmission electron microscope studies. Compact bone was found in close proximity to the surface of the metal. With higher magnifications, the bone was found to be in intimate contact with the metal. There was no suggestion of the presence of cells or uncalcified collagen fibres between the bone and the implant. At the highest magnification, there was the appearance of a homogenous transition from the bone to the metal, suggesting a biological adhesion.     

Structure of the bone‐titanium interface in retrieved clinical oral implants

7 clinically stable, "osseointegrated", titanium implants, inserted in human jaws for l–16 years, were retrieved for morphological analysis of the bone‐titanium interface, using 3 different preparation techniques. The bone‐titanium interface varied as judged from light microscopy of ground sections. The threads of the implants were well filled 79–95% with dense lamellar bone as quantified with morphometry. A large fraction of the implant surface (56–85%) appeared to be in direct contact with the mineralized bone. In general, the non‐boric areas consisted of pockets with osteocytes, bone marrow tissue and/or vessels. Sections were prepared for light microscopy and transmission electron microscopy using a fracture technique. where the implant was separated from the embedded tissue before sectioning, and an electropolishing technique, where the bulk part of the implant was electrochemically removed. In areas judged as direct mineralized bone‐titanium contact in the light microscope. the interfacial structure varied at the ultrastructural level. In areas along the interface, unmineralized tissue was present either as a narrow 0.5–l μm wide zone containing collagen fibril or as deeper pockets containing osteocytes or vessels. In areas with mineralized bone contact. an amorphous granular layer (100–400 nm wide) with no mineral was observed in the innermost interface bordering the mineralized bone, with an electron‐dense lamina limitans‐like line (approximately 50 nm thick). It is concluded that the bone‐titanium interface of the 7 clinically retrieved titanium oral implants examined in the present study bone was heterogenous. In areas of a direct mineralized bone‐titanium contact at the ultrastructural level. mineralized bone reached close to the implant surface, but was separated by an amorphous layer. 1 being 100–400 nm thick.     

Early tissue reaction at the interface of immediately loaded dental implants

PURPOSE: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osteoblasts at the implant surface under load. A newly designed dental implant indicated for immediate loading was tested in vivo for early stages of osteoblast behavior at the implant surface. MATERIALS AND METHODS: Thirty-two implants were placed in the mandibles of 8 minipigs. Half of the implants (n = 16) were immediately loaded under occlusal contacts, and implants placed in non-occlusal relations served as a control. RESULTS: All implants, except 1 that showed signs of tissue infection, healed uneventfully and were stable throughout the experimental period. Ultrastructural analysis of mandibular specimens revealed an intimate attachment of osteoblasts to the material surface beginning as early as day 1. Application of either occlusal or non-occlusal load did not alter the phenotypic morphology of the attached osteoblasts. Transmission electron microscopy and x-ray diffraction analysis demonstrated a direct contact of bone-like minerals over the whole implant surface with no signs of crestal hard tissue alteration. Electron diffraction analysis showed a slight release of titanium from the implant side. DISCUSSION: These results indicate that immediate loading of specially designed dental implants can be performed without disruption of the titanium/bone interface or disturbance of osteoblast physiology in the early loading phase. CONCLUSION: Immediate loading protocols can be performed without disturbance of normal bone biology.     

Evaluations of bone tissue integration to pure and alloyed titanium implants

Purpose: This study was performed for comparisons of tissue integration to commercially pure (CP) and titanium-6-aluminum-4 vanadium (Ti-6-Al-4V) implants using various existing three-dimensional biomechanical and two-dimensional histomorphometrical techniques, and to monitor the loosening torque during in vivo removal torque (RTQ) test with a novel unit not used before in a pilot study in rabbits.
Materials and Methods: The implants were topographically characterized and inserted in femurs and tibiae of five rabbits (in total 40 implants, 20 per group). After 16 weeks, the implant integration was biomechanically evaluated by: (1) resonance frequency test, and (2) peak RTQ test and the graph from the monitoring curve. Biopsies of the implants in situ were processed to undecalcified cut and ground sections followed by light microscopical quantifications. Shear strength calculations were performed.
Results: Significantly higher mean value of RTQ ( p  = .01) and shear strength tests ( p  = .03) were observed for the CP titanium implants compared to Ti-6-Al-4V implants. The monitoring curve from the RTQ test demonstrated no differences in the shape or form that could provide further information about the differences in the implant-to-bone attachment.
Conclusions: The CP titanium implants showed increased RTQ and shear strength values compared to the Ti-6-Al-4V implants. The new tool of monitoring the RTQ curve could not demonstrate differences between the two materials. The exact influence of the implant materials on the surrounding tissues needs to be further investigated.     

Visualization and initial characterization of the titanium boundary of the bone-implant interface of osseointegrated implants.

A simple procedure has allowed consistent visualization of the titanium boundary of the bone-implant interface of osseointegrated titanium implants at the electron microscope level. This was accomplished by embedding the intact bone-implant specimen block with low-viscosity resin prior to removal of the device in preparation for sectioning. The titanium boundary consisted of either a thin, compact amorphous electron dense layer, a broad layer of dense amorphous granules, or both. This material was removed by decalcification in formic acid (prior to embedding) and did not diffract electrons (ie, was noncrystalline). Scanning-transmission electron microscopy-EDX analysis indicated the presence of titanium, calcium, and phosphorus in the electron dense material. Field emission scanning electron microscopy-EDX dot-mapping analysis confirmed the presence of these elements and mapped them to the same locations at the implant-interface boundary.     

Bone-hydroxyapatite interface in retrieved hydroxyapatite-coated titanium implants: a clinical and histologic report

Two hydroxyapatite-coated implants were retrieved after 12 months of loading because of a fracture of the abutments. The specimens were treated to obtain thin ground sections, and a microprobe chemical analysis was done under a scanning electron microscope equipped with an energy-dispersive x-ray analysis and cathodoluminescence system. Under light microscopy, close contact between the bone and the hydroxyapatite coating was seen, with no gaps at the interface. In some areas of the coating a reduction of the coating thickness could be observed, along with the presence of some detached hydroxyapatite particles embedded in newly formed bone. The chemical analysis of the cathodoluminescent areas at the interface showed a reduced calcium:phosphorus ratio in this region.     

钛材表面烤瓷的瓷金属界面研究

目的：研究瓷与钛材界面形态学特征和元素扩散情况。方法：在钛材面上烧烤低温瓷Ｃｅｒａｔｉｎ,用扫描电镜和金相显微镜观察钛材和瓷界面区域及材料组织结构。用能谱分析仪观测界面区元素扩散情况。用ＰＷ１７００型自动化粉末衍射仪测定钛板作热处理后表面新生的氧化物。结果：显微镜下,在钛材表面该瓷有良好的浸润性和扩散作用,对钛材附着紧密,ＴＣ４面向界面区出现结构变化层。能谱分析发现界面区有钛、铝、硅元素扩散现象。Ｘ线衍射检查揭示ＴＡ２、ＴＣ４表面都有ＴｉＯ２形成。结论：Ｃｅｒｃｔｉｎ和钛材热力学性能匹配,其结合机理包括机械性结合和化学性结合。     

Temporal sequence of hard and soft tissue healing around titanium dental implants

The objective of the present review was to summarize the evidence available on the temporal sequence of hard and soft tissue healing around titanium dental implants in animal models and in humans. A search was undertaken to find animal and human studies reporting on the temporal dynamics of hard and soft tissue integration of titanium dental implants. Moreover, the influence of implant surface roughness and chemistry on the molecular mechanisms associated with osseointegration was also investigated. The findings indicated that the integration of titanium dental implants into hard and soft tissue represents the result of a complex cascade of biological events initiated by the surgical intervention. Implant placement into alveolar bone induces a cascade of healing events starting with clot formation and continuing with the maturation of bone in contact with the implant surface. From a genetic point of view, osseointegration is associated with a decrease in inflammation and an increase in osteogenesis‐, angiogenesis‐ and neurogenesis‐associated gene expression during the early stages of wound healing. The attachment and maturation of the soft tissue complex (i.e. epithelium and connective tissue) to implants becomes established 6–8 weeks following surgery. Based on the findings of the present review it can be concluded that improved understanding of the mechanisms associated with osseointegration will provide leads and targets for strategies aimed at enhancing the clinical performance of titanium dental implants.     

Bone-implant interface structures after nontapping and tapping insertion of screw-type titanium alloy endosseous implants

To compare different surgical insertion procedures, histologic and histometric studies were made on the structure of the interface between jaw bone and implants in two monkeys. Two materials were tested; TiO2 coated and noncoated, screw-type titanium alloy endosseous implants. All implants by tapping insertion were healed with direct bone apposition whereas implants by nontapping insertion revealed some degrees of fibrous connective tissue intervention between bone and implant. No difference was found between TiO2 coated and non-coated materials.