Comparison of bacterial adherence to polylactides, silicone, and titanium

CONCLUSIONS: Less bacterial adherence occurred on uncoated polylactide and silicone than on uncoated titanium surfaces. Albumin coating was an effective method to inhibit bacterial adherence to all these surfaces. As regards bacterial adherence, polylactides are at least as safe implant materials as silicone and titanium. OBJECTIVES: We compared adherence of Staphylococcus aureus and Pseudomonas aeruginosa to four implant materials and studied the inhibitory effect of albumin on adherence. The aims were to discover any differences between materials and to study the effectiveness of albumin coating. MATERIALS AND METHODS: Eight plates of polylactide A and B, silicone, and titanium were exposed to S. aureus and P. aeruginosa. Four of these plates were uncoated and four were coated with albumin. A total of 64 plates were included in the study. The bacteria were stained with acridine orange, and 10 photomicrographs of each plate allowed quantification of the surface area covered with bacteria. RESULTS: The most adherence occurred on titanium without coating. Albumin coating of the surface significantly reduced bacterial adherence to each material. Differences between materials with albumin coating were relatively small. Of the bacteria, P. aeruginosa had the greater capacity to adhere to a surface.     

Albumin-coated tympanostomy tubes: prospective, double-blind clinical study

OBJECTIVES: Coating an implant with albumin prevents adhesion of proteins, bacteria, and platelets and thus may lead to its improved and prolonged function. Previously, we have demonstrated the inhibition of binding of fibronectin, one of the most adhesive glycoproteins, on human serum albumin (HSA)-coated tympanostomy tubes and the durability of this binding inhibition in a 8-month trial. We have also demonstrated that the HSA coating inhibits the binding of Staphylococcus aureus and Pseudomonas aeruginosa to titanium plates. This prospective study evaluated the effect of albumin coating on tympanostomy tube sequelae and on the outcome of tympanostomized patients. STUDY DESIGN: Double-blind, prospective, randomized clinical trial. METHODS: Two otolaryngological centers in southern Finland enrolled 179 pediatric patients. Number of tube occlusions and otorrhea and tube ventilation time in the ears with HSA-coated titanium tympanostomy tubes were compared with the contralateral ear with its uncoated, otherwise identical titanium tube during a 9-month follow-up period. RESULTS: In HSA-coated tubes, average ventilation time was slightly longer and the number of early tube occlusions significantly less (P < .05). Moreover, in patients with perioperative bleeding, the coating prolonged average ventilation time of tympanostomy tubes significantly (P < .05). CONCLUSIONS: HSA coating reduces early tube occlusions by preventing adherence of blood and secretion.     

Durability of the binding inhibition of albumin coating on tympanostomy tubes

OBJECTIVE: Occlusion and prolonged otorrhea are typical problems associated with the use of middle-ear ventilation tubes. Albumin coating of ventilation tubes has been introduced to prevent tube occlusions by granulation tissue, blood clot, or pus. In this study, the durability of the binding inhibition (BI) of fibronectin was examined on the tube surface in albumin-coated tubes in different environments during an 8-month trial. METHODS: Human serum albumin (HSA) was used to coat silicone tympanostomy tubes. Fibronectin, a typical adhesive protein in serum and exudates, was used as a model representative of exudates of the ear. The durability of BI of this glue protein on the tube surface was tested in different time periods with radiolabelled fibronectin. Scanning electron microscopy (SEM) was performed on the tubes. RESULTS: The BI of fibronectin, achieved with the albumin coating, was still strong after 8 months of storage at +4 degrees C. A slight decline in BI was noted between the first and third months of storage at +37 degrees C. A significant difference between HSA-coated and uncoated tympanostomy tubes was noted in SEM. The uncoated surface generally appeared to be rougher than that of HSA-coated tubes when either titanium or silicone tubes were tested. CONCLUSIONS: Albumin coating markedly inhibits the binding of fibronectin on tube surfaces in vitro. A clear BI achieved by albumin coating on tube surfaces was shown to persist throughout an 8-month trial, although some reduction of the BI was seen over time. The result emphasizes the role of albumin coating in preventing the adherence of foreign material on tympanostomy tubes. No advantage was achieved by using a cross-linking chemical in the albumin coating.     

Role of albumin coating of tympanostomy tubes: long-term clinical evaluation

OBJECTIVE: Our previous work has shown that albumin coating of tympanostomy tubes prevented adhesion of proteins or bacteria on the tube surface in vitro and in a 9-month prospective follow-up study. This study was continued until all tubes were extruded. STUDY DESIGN: A prospective, clinical trial. METHODS: The randomized, double-blind clinical trial had 149 patients. The randomization was revealed after the follow-up period of 9 months. The number of tube sequelae in ears with human serum albumin (HSA)-coated titanium tympanostomy tubes was compared with the contralateral ears with uncoated, otherwise identical titanium tubes. The follow-up continued until all tubes were extruded, followed by evaluation of each tympanostomized patient. RESULTS: No significant difference between the two tube types emerged after the 9-month follow-up. Among the patients younger than 2 years, one of the three typical bacteria causing acute otitis media (AOM), Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis, was found in 45% of all bacterial cultures taken during AOM. However, among patients older than 2, one of these bacteria appeared in 17% of all the bacterial cultures and in 8% of cultures taken during the summer. CONCLUSIONS: After the first 9 follow-up months, no difference was found in the sequelae related to uncoated and HSA-coated tubes. The typical bacteria causing AOM were found less frequently among patients older than 2 years. A profile of tympanostomy patients in Finland will be given.     

New method for coating tympanostomy tubes to prevent tube occlusions

OBJECTIVE: tympanostomy tube insertion is currently the most common surgical procedure requiring general anesthesia performed on children. Occlusion of the tube and prolonged otorrhea through the tube are typical problems associated with the use of middle-ear ventilation tubes. In this study, a new method for coating ventilation tubes is introduced that prevents occlusion of the tube lumen by granulation tissue, blood clot or pus. METHODS: human serum albumin (HSA) was used to coat standard tympanostomy tubes of different materials. Fibronectin, a typical protein in serum and exudates and one of the most adhesive glycoproteins, was used as a model representative of exudates of the ear. RESULTS: when compared with the binding on uncoated tubes, the binding of fibronectin on HSA-coated tubes was inhibited from 59 to 85%, depending on the tube material used. CONCLUSIONS: HSA-coating markedly reduced the binding of fibronectin on tube surfaces in vitro. The study shows the potential role of HSA-coating in preventing the adherence of foreign material to tympanostomy tubes and reducing tube occlusions.     

The resistance of maxillofacial reconstruction plates to biofilm formation in vitro

OBJECTIVES/HYPOTHESIS: Bacterial biofilms, bacteria surrounded by a protective glycocalyx, have been demonstrated on bioimplants placed within and outside of the head and neck region. The presence of the biofilm often makes decontamination of an infected implant impossible, requiring removal of the implant. Infections attributable to biofilm formation within the facial skeleton after reconstruction with implants may result in delayed union, fibrous union, malunion, nonunion, and malocclusion. These complications often require removal of the implant and secondary surgery. Although the incidence of infections necessitating implant removal is relatively low, the increased numbers of implants being placed make this a growing problem. Previous work in the authors laboratory has demonstrated a resistance to biofilm formation on different types of pressure-equalizing tubes. The hypothesis evaluated in the study is that such resistance to biofilm formation is due to the inability of bacteria to adhere to the tubes because of the material's smoothness or surface charge. STUDY DESIGN: A controlled observational study. METHODS: Scanning electron microscopy was used to evaluate the formation of biofilms in vitro for a common strain of Staphylococcus aureus on four implantable materials. The implantable materials included titanium and polylactide resorbable plates. RESULTS: Consistent with the authors' prior findings, they were able to produce bacterial biofilm reliably on a silicone pressure equalizing tube but were unable to demonstrate biofilm formation on the titanium or resorbable implants. CONCLUSION: The absence of biofilm formation on these implants can best be explained by the surface charge or polarity properties of these materials. These findings are consistent with the relatively low incidence of infections among patients receiving these implants in maxillofacial applications.     

Evaluation of the osseointegration of dental implants coated with calcium carbonate:an animal study

In an attempt to overcome the limitations of titanium in dental and orthopaedic clinical applications, a new method has been developed to prepare calcium carbonate coatings on sandblasted and acid-etched (SA) titanium implants. The purpose of this study was to investigate the effect of calcium carbonate-SA (CC-SA) implants on osseointegration in vivo. The surfaces of SA and CC-SA implants were characterised for surface morphology and surface chemistry. Subsequently, these two kinds of implants were implanted in the femoral condyles of rabbits. The implants were retrieved and prepared for histological and histomorphometric evaluation 1, 2, 4, 8 and 12 weeks after implantation. Significantly higher values of bone-to-implant contact of the entire implant except the gap area (BIC_ALL) and the bone-to-implant contact of the gap area (BIC_GAP) were found in animals with the CC-SA implants than in those with the SA implants at 4 weeks. Higher values of total gap bone were found in those with the CC-SA implants than in those with the SA implants at 1, 2 and 4 weeks. In conclusion, the current findings demonstrate that the calcium carbonate coating can improve and accelerate the early ingrowth of bone and osseointegration at the early healing phase. This may reduce clinical healing times and thus improve implant success rates.     

Osteoblast integration of dental implant materials after challenge by sub-gingival pathogens:a co-culture study in vitro

Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium (Ti), titanium-zirconium (TiZr) alloys and zirconia surfaces. Monoculture studies with either U2OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2OS osteoblasts were favourable on all materials. Adhering U2OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from TiZr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.     

Osteoblast reaction on SLA and microgrooved implant surfaces]

The osseointegration process of dental implants depends on the tissue reaction at the tissue-implant interface. Osteoblasts are the main cells responsible for the regulation of osteoinduction. The manner and kinetics of the tissue reaction crucially depend on the interaction between osteoblasts and the morphology of the implant surface. The aim of this study was to investigate osteoblast behaviour on different implant surfaces (smooth, microgrooved, SLA) under standardized conditions. For this in vitro investigation we used primary bovine osteoblasts. Attachment kinetics, proliferation rate and synthesis of bone-associated proteins were used as parameters for cell reaction. The results demonstrate that both attachment and adhesion strength of the primary cell surface interaction was higher on the microgrooved surfaces than on SLA surfaces. The proliferation rate of cells and the synthesis of bone-specific proteins were higher on microgrooved surfaces in contrast to SLA surfaces. Ultrastructural analysis revealed phenotypic osteoblast-like cells on smooth and microgrooved surfaces, whereas cells on SLA surfaces showed a more fibroblastic appearance. This study demonstrates that the morphology of the implant surface determined the subsequent osteoblast reaction. An optimal cell reaction was found at surfaces which are smooth in the microenvironment of osteoblasts.     

Bacterial biofilms may contribute to persistent cochlear implant infection.

OBJECTIVES: To determine if bacterial biofilms are present on the surface of extruding or persistently infected cochlear implants. METHODS: Scanning electron microscopy was performed on cochlear implants removed from two patients because of recalcitrant infection, two implants removed secondary to device failure, and two devices that had never been implanted. Preparations were examined by experienced microbiologists for the presence of bacterial biofilms. RESULTS: Microorganisms and amorphous extracellular debris were found on the surface of the infected cochlear implants and the implants removed because of device failure. Biofilm formation was deemed definite in one infected device and possible in the other explanted devices. The never-implanted controls demonstrated microbial contamination without exopolymeric matrix, inconsistent with biofilms. CONCLUSION: Bacterial biofilm formation may play a role in recalcitrant cochlear implant infections. This may have profound implications for the treatment of cochlear implant infections.     

Chemically modified, ultra-hydrophilic titanium implant surfaces]

Recently, a chemically modified ultra-hydrophilic sand-blasted, large grit and acid-etched (modSLA) titanium surface has been introduced in order to enhance bone apposition. Indeed, preliminary preclinical and clinical data have indicated that modSLA implants may enhance bone apposition during early stages of wound healing. These positive effects on bone regeneration might be probably mainly due to the hydrophilic surface properties noted for modSLA which ensured a stabilization of the blood clot.The aim of the present review article is to evaluate, based on the currently available evidence, the potential impact of modSLA surfaces for implant dentistry.     

Effect of KTP laser on implants used in middle-ear surgery

The present study is intended to explore the effects of the KTP laser on various types of implant, used in middle-ear surgery. A laboratory study was undertaken to evaluate the interaction between the KTP laser (KTP-532 Orion Laser, Laserscope, UK) and individual middle-ear implants. A variety of middle-ear implants were used: a silicone sheet, Teflon, hydroxylapatite, ionomeric cement, gold and titanium prostheses as well as gelfoam. Following exposure to the laser, these implants were studied by direct inspection using an operating microscope. The KTP laser induced no detectable alteration in any of the implants when they were clean and dry. However, in the presence of fresh blood, under the influence of the energy of the absorbed laser, the silicone burnt and melted and the Teflon piston was vaporized. Likewise, a few tiny holes appeared on the surface of the ionomeric implant and then the prosthesis deformed. The hydroxylapatite implant broke into two pieces. However, no detectable alteration could be observed on gold or titanium pistons, even in the presence of blood. The authors conclude, that in the presence of blood, interaction between the KTP laser and both silicone and hydroxylapatite implants needs to be avoided. Teflon prostheses can be cautiously vaporized. Gold and titanium prostheses were unaffected by laser even in the presence of blood.     

Craniofacial augmentation with porous polyethylene implants (Medpor: first clinical results]

SUBJECT: Porous polyethylene (Medpor) is an alloplastic material commonly used in craniofacial reconstruction. We report about our first clinical experiences with Medpor for facial augmentation procedures. PATIENTS AND METHODS: We treated 27 patients between 2001 and 2005 (11 female, 16 male) with 48 Medpor-implants. The indications for application of porous polyethylene implants in our clinic were congenital malformations (15), post-traumatic defects (10), and reconstructions after tumor resection (2). The implants were used for nasal/paranasal augmentations (16), for zygomatico-orbital augmentations (18), and for augmentations of the chin and malar region (11). The procedures were performed in a standardized manner. We used prefabricated, self-contoured implants and fixed them subperiosteally with titanium osteosynthesis screws. All operations were performed under general anesthesia. We evaluated the aesthetic results and the ingrowth behavior clinically and histologically. RESULTS: We achieved good aesthetic results and the patients showed no signs of discomfort or rejection. Four patients required a second intervention. These revision surgeries included two cases of local infections and two for aesthetic contouring. The necessary reduction of the implants allowed the harvesting of tissue and implant samples for microscopy. CONCLUSION: Porous polyethylene implants showed a good fibrovascular integration without encapsulation under the light microscope. Giant cells were detected on the surface of the implants. Besides this there was evidence for resorption of the implant material. Fixation with titanium screws is very effective. No implant dislocation or implant fracture occurred. The implants showed high volume stability and were easily handled and contoured. It is not possible to visualize Medpor implants with current imaging techniques, because polyethylene shows no contrast.     

Does metal coating improve the durability of silicone voice prostheses?

Voice prostheses, which are used for voice rehabilitation in cancer patients after laryngectomy, usually become colonized with a mixed biofilm of bacteria and Candida after 2-4 months and lose their efficiency. It is essential to ensure the stability and biocompatibility of these implants. With the aid of surface frame analysis we have shown that local antifungal treatment is inadequate for eliminating the deep infiltration and encapsulation of Candida colonies in silicone. A surface that prevents the adhesion of microorganisms is required. Because of its special properties there are few methods available for coating silicone. We employed, for the first time, a new method of surface modification using anodic vacuum arc coating. Using this method it was possible to obtain a solid film of gold or titanium metal with a layer thickness < 100 nm. Resistance against Candida colonization and destruction of coated prostheses were tested both in vitro and in vivo. A titanium coating seemed to provide the optimal solution to the problem, because surface adhesion and the smoothness of the material appeared to be superior to those of a gold coating.     

Extracellular Matrix Components in Nasal Polyposis

Voice prostheses, which are used for voice rehabilitation in cancer patients after laryngectomy, usually become colonized with a mixed biofilm of bacteria and Candida after 2-4 months and lose their efficiency. It is essential to ensure the stability and biocompatibility of these implants. With the aid of surface frame analysis we have shown that local antifungal treatment is inadequate for eliminating the deep infiltration and encapsulation of Candida colonies in silicone. A surface that prevents the adhesion of microorganisms is required. Because of its special properties there are few methods available for coating silicone. We employed, for the first time, a new method of surface modification using anodic vacuum arc coating. Using this method it was possible to obtain a solid film of gold or titanium metal with a layer thickness &lt; 100 nm. Resistance against Candida colonization and destruction of coated prostheses were tested both in vitro and in vivo. A titanium coating seemed to provide the optimal solution to the problem, because surface adhesion and the smoothness of the material appeared to be superior to those of a gold coating.     

Interaction of spiral ganglion neuron processes with alloplastic materials in vitro(1)

The cochlear implant (CI) involves the introduction of alloplastic materials into the cochlea. While current implants interact with cochlear neurons at a distance, direct interactions between spiral ganglion (SG) neurites and implants could be fostered by appropriate treatment with neurotrophic factors. The interactions of fibroblasts and osteoblasts with alloplastic materials have been well studied in vitro and in vivo. However, interactions of inner ear neurons with such alloplastic materials have yet to be described. To investigate survival and growth behavior of SG neurons on different materials, SG explants from post-natal day 5 rat SG were cultured for 72 h in the presence of neurotrophin-3 (10 ng/ml) on titanium, gold, stainless steel, platinum, silicone and plastic surfaces that had been coated with laminin and poly-L-lysine. Neurite outgrowth was investigated after immunohistological staining for neurofilament, by image analysis to determine neurite extension and directional changes. Neurite morphology and adhesion to the alloplastic material were also evaluated by scanning electron microscopy (SEM). On titanium, SG neurites reached the highest extent of outgrowth, with an average length of 662 microm and a mean of 31 neurites per explant, compared to 568 microm and 21 neurites on gold, 574 microm and 24 neurites on stainless steel, 509 microm and 16 neurites on platinum, 281 microm and 12 neurites on silicone and 483 microm and 31 neurites on plastic. SEM revealed details of adhesion of neurites and interaction with non-neuronal cells. The results of this study indicate that the growth of SG neurons in vitro is strongly influenced by alloplastic materials, with titanium exhibiting the highest degree of biocompatibility with respect to neurite extension. The knowledge of neurite interaction with different alloplastic materials is of clinical interest, as development in CI technology leads to closer contact of implanted electrodes with surviving inner ear neurons.     

Osseointegration of Titanium Prostheses on the Stapes Footplate

The success of middle ear reconstructive surgery depends on stable coupling between the prosthesis and residual ossicles. To establish a stable fixed point on the stapes footplate for subsequent prosthesis reconstruction, a titanium footplate anchor was coated with osteoinductive substances to induce a controlled osseointegration on the footplate. Various studies have shown that collagen-based matrices with and without bone growth and differentiation factors can induce and enhance bone formation and consequently increase implant stability. The ears of 23 one-year-old Merino sheep (n = 46) were divided into five groups and implanted with a specially designed footplate anchor. The surface of each implant was modified by applying a collagenous matrix (collagen I or II) either with immobilized bone morphogenic protein (BMP-4) or transforming growth factor-ß, respectively, to stimulate osteoblastic activation and differentiation on the stapes footplate with subsequent osseointegration. Polychrome labeling was used to assess new bone formation and remodeling during the study. After study termination on day 84, synchrotron radiation-based computed microtomography and histomorphometry were used to identify bone implant contact. Eight implants showed radiographical and/or histological evidence of integration by newly formed bone. An osseointegration could histologically be proven in two of these eight specimens, and additional ectopic bone formations were seen in another 21 specimens. In all animals, bone turnover on the footplate was proven by polychrome labeling. This study proves the general ability to induce a controlled osseointegration of titanium implants biologically activated with artificial extracellular matrices on their surfaces on the stapes footplate in a mammalian organism.     

Reconstruction of the frontal bone with individual titanium implants after surgical therapy of osteomyelitis of the frontal bone

Individually prefabricated titanium implants enable the reconstruction of the frontal bone after surgical therapy of osteomyelitis without compromising mechanical stability or aesthetic results. Primarily the infected bone tissue is removed. Helical computed tomographic systems are used for the aquisition of patient data. After being transmitted to a computer aided design system (CAD-system) this data is used for construction of the implant geometry using freeform-surfaces. The outer surface contour is derived from the contours of the bone defect. The completed computer-based implant design is finally transformed into control data to run the milling machine which produces the implant from a block of titanium. Modern industrial CAD/CAM-technology allows standardized prefabrication using data from CT-scans. The precision of all implants was predictable and duration of the reconstructive procedure could be reduced. During postoperative follow-up (5-24 months) no loss of implant or recurrence of the osteomyelitis could be observed.     

Development of cochlear-wall implants for electrical stimulation of the auditory nerve

The aim of these experiments was to investigate the use of titanium implants for anchorage of stimulating electrodes or other clinical or experimental devices in the bony wall of the cochlea. Twenty-six cylindrical titanium fixtures, 0.6 mm in diameter, were inserted into holes drilled in the otic capsule in 8 ears in 5 nonhuman primates and then examined for stability after periods of 2 months to 2 years. Following sacrifice, the bone-metal interfaces were examined microscopically. Fourteen of the implants were firmly fixed in the bone, 6 were loosely fixed and 6 came out. Poor fixation was associated with infection in the middle ear. In uninfected ears, 90% of the implants were stable. The implants were not osseointegrated in the classic sense, but in stable implants, direct bone contact covering 5 to 60% of the titanium oxide surface of the implant shaft was observed.