Contour analysis of an implant--soft tissue interface.

BACKGROUND AND OBJECTIVE: Studies of peri-implant soft tissue on in vivo models are commonly based on histological sections prepared using undecalcified or 'fracture' techniques. These techniques require the cutting or removal of implant during the specimen preparation process. The aim of this study is to explore a new impression technique that does not require any cutting or removal of implant for contour analysis of soft tissue around four types of titanium (Ti) surface roughness using an in vitro three-dimensional oral mucosal model (3D OMM). METHODS: The 3D OMM was constructed by co-culturing a keratinocyte cell line TR146 and human oral fibroblasts on to an acellular dermis scaffold. On the fourth day, a Ti disk was placed into the model. Four types of Ti surface topographies, i.e. polished, machined, sandblasted and anodized were tested. After 10 d of culture, the specimens were processed based on undecalcified (ground sectioning), electropolishing and impression techniques for contour analysis of the implant-soft tissue interface. RESULTS: Under light microscopic examination of the ground and electropolishing sections, it was found that the cell line-based oral mucosa formed a peri-implant-like epithelium attachment on to all four types of Ti surfaces. In contour analysis, the most common contour observed between the cell line-based oral mucosa and Ti surface was at an angle ranging between 45° and 90°. CONCLUSION: The in vitro cell line-based 3D OMM formed a peri-implant-like epithelium at the implant-soft tissue interface. The contour of the implant-soft tissue interface for the four types of Ti surface was not significantly different.

Long-term biocompatibility and osseointegration of electron beam melted, free-form-fabricated solid and porous titanium alloy: experimental studies in sheep.

The purpose of the present study was to evaluate the long-term osseointegration and biocompatibility of electron beam melted (EBM) free-form-fabricated (FFF titanium grade 5 (Ti6Al4V) implants. Porous and solid machined cylindrical and disk-shaped implants were prepared by EBM and implanted bilaterally in the femur and subcutaneously in the dorsum of the sheep. After 26 weeks, the implants and surrounding tissue were retrieved. The tissue response was examined qualitatively and quantitatively using histology and light microscopic (LM) morphometry. Selected bone implants specimens were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-computed tomography (mCT). The results showed that both porous and solid implants were osseointegrated and high bone-implant contact was observed throughout the porous implant. In the soft tissue, the porous implants showed thinner fibrous encapsulation while no signs of intolerance were observed for either implant type. Taken together, the present experimental results show that FFF Ti6Al4V with and without porous structures demonstrate excellent long-term soft tissue biocompatibility and a high degree of osseointegration. The present findings extend earlier, short-term experimental observations in bone and suggest that EBM, FFF Ti6Al4V implants possess valuable properties in bone and soft tissue applications.

Late follow-up of a randomized trial of routine duplex imaging before varicose vein surgery.

BACKGROUND: Routine preoperative duplex examination led to an improvement in results 2 years after surgery for primary varicose veins. The aim of the present study was to evaluate the impact of preoperative duplex imaging after 7 years, in relation to other risk factors for varicose vein recurrence. METHODS: Patients with primary varicose veins were randomized to operation with (group 1), or without (group 2) preoperative duplex imaging. The same patients were invited to attend follow-up with interview, clinical examination and duplex imaging. Quality of life (QoL) was measured with the Short Form 36 questionnaire. RESULTS: Some 293 patients (343 legs) were included initially; after 7 years 227 were interviewed, or their records reviewed: 114 in group 1 and 113 in group 2. One hundred and ninety-four legs (95 in group 1 and 99 in group 2) were examined clinically and with duplex imaging. Incompetence was seen at the saphenofemoral junction and/or saphenopopliteal junction in 14 per cent of legs in group 1 and 46 per cent in group 2 (P < 0.001). QoL was similar in both groups. After a mean follow-up of 7 years (and including patients who underwent surgery after the review), 15 legs in group 1 needed reoperation and 38 in group 2 (P = 0.001). CONCLUSION: Routine preoperative duplex imaging improved the results of surgery for primary varicose veins for at least 7 years.

Calcium aluminate coated and uncoated free form fabricated CoCr implants: a comparative study in rabbit.

The purpose of this study was to compare the integration in bone of uncoated free form fabricated cobalt chromium (CoCr) implants to the same implant with a calcium aluminate coating. The implants of cylindrical design with a pyramidal surface structure were press-fit into the limbs of New Zealand white rabbits. After 6 weeks, the rabbits were sacrificed, and samples were retrieved and embedded. Ground sections were subjected to histological analysis and histomorphometry. The section counter part was used for preparing an electron transparent transmission electron microscopy sample by focused ion beam milling. Calcium aluminate dip coating provided a significantly greater degree of bone contact than that of the native CoCr. The gibbsite hydrate formed in the hardening reaction of the calcium aluminate was found to be the exclusive crystalline phase material in direct contact with bone.

Effect of molecular mobility of polymeric implants on soft tissue reactions: an in vivo study in rats.

Although numerous different polymers are used as implants or otherwise studied for many other biotechnical applications, there is a lack of basic models that correlate polymer characteristics with foreign body reactions. This study aims at developing one such model by systematically studying surface molecular mobility of polymeric implants in soft tissues in vivo. Changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs), provides an interesting opportunity to study the surface molecular mobility with minimal changes of the hydrophobicity of the surface. Thus, in this study three different PAMAs, with increasingly surface mobility; poly (isobutyl methacrylate) (PIBMA), poly(butyl methacrylate) (PBMA), and poly(lauryl methacralate) (PLMA) along with pure titanium (Ti) substrates were implanted in the dorsum of Sprague-Dawley rats. Inflammatory cell recruitment, cell adhesion, and cytokine release were studied after 1, 3, and 28 days of implantation. Total number of inflammatory cells in the exudate was measured but no correlation between surface mobility and cell recruitment where found. However, the number of surface associated cells where significantly lower on the surfaces with high molecular mobility (PLMA and PBMA). The histological evaluation performed after 28 days revealed thicker fibrous capsule and a higher number of blood vessels on the low molecular mobility surface (PIBMA). After 28 days the cell activity was higher on the high molecular mobility surfaces (PLMA and PBMA) compared with PIBMA, based on the cytokine release. None of the surfaces induced any significant cell-death. On the basis of the results of this study we conclude that there is a significant difference in biological response to surfaces with different in molecular mobility. This might affect the wound healing process and the biocompatibility of biomaterials.

A novel tool for high-resolution transmission electron microscopy of intact interfaces between bone and metallic implants.

A key feature in the understanding of the mechanisms of integration versus rejection of implanted materials is a deepened understanding of the elemental and molecular compositions of the interface zone between the surface of the synthetic man-made material and the biological components of tissue. Intact interfaces between metallic implants and tissues have not been able to image and analyse on the ultrastructural level with the common transmission electron microscopy (TEM) sample preparation techniques. By using focused ion beam microscopy for site-specific preparation of TEM samples, intact interfaces between metal implants and calcified tissue were imaged for the first time. The interface's elemental and crystallographic compositions were determined using energy dispersive X-ray mapping and electron diffraction. The developed technique fulfills a long-sought-for demand to correlate the surface properties of implanted metal prostheses with the fine structure and composition of preserved interfaces with tissues.

Bone response to surface modified titanium implants - studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses.

The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.

Method for ultrastructural studies of the intact tissue-metal interface.

Samples were prepared for ultrastructural studies of the intact interface between metallic implants and tissue by transmission electron microscopy. The method is based on plastic embedding of implant and tissue and subsequent removal of the bulk metal by electrochemical dissolution (electropolishing), to facilitate preparation of ultrathin sections for transmission electron microscopy. Surface sensitive spectroscopy (Auger electron microscopy and X-ray photoemission spectroscopy) and transmission electron microscopy EDX results show that the method produces samples with an intact interface, containing the implant surface oxide and the adjacent tissue. Examples of application of the method on titanium, zirconium and aluminium implants in soft tissue are given.