Inhibition of eFGF expression in Xenopus embryos by antisense mRNA

This pilot study analyzed the bone reactions to early loaded titanium plasma-sprayed implants. A total of 24 titanium plasma-sprayed implants (12 in the maxilla and 12 in the mandible) (Primary Healing Implant, Legnano) were inserted into four Macaca fascicularis monkeys with instruments specially designed to obtain a precise fit of the implant in the bone socket. A metal superstructure was cemented into 10 mandibular and 10 maxillary implants 15 days after implant insertion. The four remaining implants were used as controls. Eight months after implant placement, a block section was carried out, the defect was filled with nonresorbable hydroxyapatite, and all 24 implants were retrieved. The implants were treated to obtain thin ground sections that were examined under normal and polarized light. Histologic analysis showed that bone was observed around the implant surface in all implants. Morphometric analysis demonstrated that bone lined 67.2% (SD = 3.1%) of the maxillary implant surface, and 80.71% (SD = 4.6%) of the mandibular implant surface. No differences were found in the percentage of bone-implant contact in the control implants. In the loaded implants, however, the bone around the implants had a more compact appearance. The study demonstrated that it is possible to obtain a high percentage of bone-implant contact in early loaded titanium plasma-sprayed implants.     

Nasal lavage as tool for health effect assessment of photochemical air pollution

In order to achieve esthetically more satisfying results, it has been proposed to place ITI implants with their border between the rough and smooth surfaces below the level of the alveolar crest, thereby obtaining a submucosally located implant shoulder following healing. The aim of the present experimental study was to clinically and radiographically evaluate the tissue response to the placement of one-stage transmucosal implants with the border between the rough and the smooth surfaces sunk by 1 mm into a subcrestal location. 11 patients underwent comprehensive dental care including the placement of 2 implants of the ITI Dental Implant System in the same quadrant (test and control). Randomly assigned control implants were placed according to the manufacturer's instructions, i.e. the border between the rough titanium plasma-sprayed and the smooth polished surfaces precisely at the alveolar crest. At the test implant the apical border of the polished surface was placed approximately 1 mm below the alveolar crest. Probing bone levels were assessed at implant placement (baseline), 4 and 12 months later. Modified plaque and modified gingival indices were recorded at 1, 2, 3, 4 and 12 months. Clinical probing depth and "attachment" levels were measured at 4 and 12 months. All parameters were assessed at 6 sites around each implant. The mean for each implant was calculated and used for analysis. The Wilcoxon matched pairs signed rank test and the Student t-test were applied to detect differences over time and between the test and control implants. At baseline, a mean difference in probing bone level of -0.86 mm (SD 0.43 mm, p < 0.05) was found between test and control implants with the test implants being placed more deeply. Both test and control implants lost a significant amount of clinical bone height during the first 4 months (test 1.16 mm, p < 0.05; control 0.58 mm, p < 0.05). However, only the test implants significantly lost clinical bone height from 4-12 months (test 1.04 mm, p < 0.05; control 0.45 mm, p = 0.08). Overall, the test implants lost 2.26 mm and the control implants 1.02 mm of bone height during the first year of service. On the average, the test implants demonstrated a bone level of 0.38 mm lower than the controls at 12 months. Except for the modified gingival index at 4 months (mean difference 0.21, SD 0.19, p < 0.05), no clinical parameters yielded significant differences between test and control implants at any time. It is concluded that in addition to the crestal bone resorption occurring at implants placed under standard conditions, the bone adjacent to the polished surface of more deeply placed ITI implants is also lost over time. From a biological point of view, the placement of the border between the rough and the smooth surfaces into a subcrestal location should not be recommended.     

Rapid bone resorption adjacent to hydroxyapatite-coated implants

This paper describes rapid bone resorption in the peri-implantitis of HA implants based on both our clinical observations of and histological research on extracted dense hydroxyapatite (HA) implants. The surfaces of extracted HA implants were rough, although they were smooth at fixture placement. Plaque formed on the necks of the implants, whereas little plaque was seen on the bottoms. The plaque consisted of cocci and rods, including filamentous bacteria. Few spirochetes were observed. Although surrounding bone was formed rapidly around the HA implant, bone thickness gradually decreased compared with the titanium implant. These facts suggest that the rigid biointegration of HA with the thin surrounding bone--that is, the overstressing of the bone--causes rapid bone resorption rather than plaque accumulation on HA.     

Histological and biomechanical analysis of bone and interface reactions around hydroxyapatite-coated intramedullary implants of different stiffness: a pilot study on the goat

We hypothesized that reduced stem stiffness of orthopaedic implants contributes to a high risk of loosening, since interface stresses and relative motions may exceed a tolerable range. To study this hypothesis, three types of load-bearing implant with different stiffnesses were inserted into the tibia of the goat. Histological analysis was performed of bone repair after insertion of the implant, bone ingrowth, interface disruption and loosening. A finite element model of the configuration provided the quantitative range of interface stresses and relative motions for the present experiment. The implants were made out of stainless steel, hollow titanium and a thin titanium core covered with a polyacetal coating. The stiffness ratios of these implants were approximately 10:4:1, respectively. All implants were coated with a layer of hydroxyapatite (HA) in order to minimize the possible biological effects of the different implant materials. Irrespective of the type of implant, there was a repair phase that lasted 6-12 weeks. The stiff implants functioned well. Large areas of bone bonding to the HA layer were found after the repair phase at 12 weeks postoperatively. After 24 weeks, some signs of loosening were observed. More loosening occurred with the hollow titanium and polyacetal implants, mainly during the repair phase. Three hollow titanium and three polyacetal coated implants survived this period, and were killed after 24 weeks. The integrity of the HA layer at the bone-implant interface of the titanium implants was good. In the polyacetal implants, the repair reaction of the cortical bone was incomplete. Bone ingrowth into HA was largely lacking. In conclusion, we found significant differences in the repair and interface reactions around implants of different stiffness. Stiff implants showed favourable initial interface conditions for bone ingrowth. Intermediate and flexible implants provoked unfavourable interface conditions for initial bone ingrowth. The finite element study showed that the flexible stems produce larger micromotions and higher interface stresses at the bone-prosthesis interface than the stiff stems, indicating an explanation for the histological findings.     

Magnetic resonance imaging lesion analysis in neurofibromatosis type 1

The purpose of this prospective study was to investigate the clinical outcome and marginal bone resorption of three different endosseous implants placed in the anterior mandibles of 15 elderly patients. Eleven women and 4 men (ranging from 65 to 80 years, mean 71 years) had three different endosseous implants placed in the anterior mandible; one titanium plasma-sprayed cylinder implant (4-mm diameter), one titanium cylinder implant with hydroxyapatite coating (4-mm diameter), and one standard threaded titanium implant (3.75-mm diameter). Three months later, at the second-stage surgical procedure, ball abutments were connected and an overdenture was placed. At 12, 24, and 36 months, marginal bone resorption and Periotest values were recorded. None of the implants was lost in this period. An analysis of variance with repeated measurement was performed annually to test the existence of significant differences between the implants. When differences appeared, paired t tests were used to identify which differences were significant. Bonferroni multipliers were used to adjust for multiple testing. When marginal bone resorption was concerned, threaded titanium and hydroxyapatite-coated implants had significantly better scores than titanium plasma-sprayed cylinder implants. Periotest values for hydroxyapatite-coated implants were significantly better than test values for the other implants after 2 years. After 3 years significance was obtained between hydroxyapatite and screw-shaped implants only (P < .05). It was concluded that titanium plasma-sprayed cylinder implants have a less favorable prognosis than the other implants used in this study.     

Parental awareness of dental caries in toddlers

Endodontic endosseous implants stabilize teeth that have crown-root ratios compromised by periodontal disease, trauma, or apical resorption. By increasing the crown-root ratio, the implant improves the prognosis of the tooth, thus increasing its longevity. The purpose of this study was to evaluate, in vivo, the healing response to a newly introduced titanium endodontic implant. Eight implants were placed in the maxillary incisors and mandibular premolars of two adult beagle dogs after completion of root canal and osseous preparation. Peri-implant tissues were examined radiographically and histologically at 6 months postinsertion. Radiographically, the periapical area and tissue surrounding the implants seemed normal. Histologically, fibrous connective tissue and healthy bone intimately surrounded the implant. Epithelium or chronic inflammatory cells were not observed along the length of the implant. These findings suggest that titanium is a biocompatible metal when used as an endodontic endosseous implant.     

Microscopical features in retrieved human Branemark implants: a report of 19 cases

The authors present a histologic analysis of 19 Branemark titanium implants retrieved for different causes: four implants were removed for abutment fracture, one for dental nerve dysesthesia, two for bone overheating, two for peri-implantitis, nine for mobility, one for unknown causes. In the implants removed for fracture a high bone-implant contact percentage was present (71.83 +/- 4.96%) with compact, mature bone at the interface. The picture of the failure due to bone overheating was characteristic with the presence of bone sequestra and of a gap between implant and bone filled by lymphocytes and plasma cells: many bacteria surrounded the necrotic bone and no newly regenerated bone was present. In peri-implantitis an inflammatory infiltrate was observed in the peri-implant tissues: a dense fibrous connective tissue was present around implants failed for mobility. The microscopical picture is certainly extremely important in identifying the causal determinants of an implant failure.     

Wear analysis of a retrieved hip implant with titanium nitride coating

There is increasing interest in using surface modification technology to improve the wear properties of titanium alloy and limit articular surface wear of metal and polyethylene components. This report details the in vivo wear performance of titanium nitride coating on a retrieved hip implant obtained postmortem from a low demand patient 1 year after total hip arthroplasty. Analysis of the well-functioning implant revealed that wear debris can originate from a titanium nitride coated femoral head, as delaminated surface asperities, and manifest as adhesive wear on the articular surface. The wear observed on this implant indicates that rigorous testing and evaluation of titanium nitride coating technology should be conducted prior to widespread use on total joint implants.     

A histological study on tissue responses to titanium implantation in rat maxilla: the process of epithelial regeneration and bone reaction

The present study aimed to establish a titanium implantation model using rat maxillae as well as demonstrate the chronological tissue responses to implantation. Pure titanium implants were inserted in the upper first molar extraction sites of Wistar rats 1 month after tooth extraction. The animals were sacrificed at 1 to 30 days postimplantation, and prepared tissue specimens were processed for light microscopy. The removal of implants from tissue blocks was done using 2 methods: mechanical removal or a cryofracture technique. In the early stages, peri-implant tissues showed severe damage to the oral epithelium and collagen bundles with significant inflammatory cell infiltration. The peri-implant epithelium grew apically along the implant by 10 days postimplantation, and regenerated to show a similar feature of junctional epithelium seen in normal rats at 15 days postimplantation, at which time no signs of inflammation were observed. The regenerated collagen bundles in the connective tissue were arranged circumferentially to the implants in the horizontal sections. New bone formation first appeared around the implants at 5 days postimplantation, covering the entire perimeter of implants by 30 days postimplantation. Scanning electron microscopic observations of the surface texture of the removed implants suggest the probability of an adhesive mechanism between the implants and the peri-implant epithelium and/or the alveolar bone. These findings indicate that this experimental model is useful for detailed analysis of peri-implant tissue because of its easy implantation procedure.     

Short-term healing following the use of calcium sulfate as a grafting material for sinus augmentation: a clinical report

Because of the frequent lack of bone in the posterior maxilla, sinus augmentation has become a commonly practiced treatment modality. Many different materials have been used for augmenting the sinus, and the ideal graft is yet to be found. The present article reports the results of sinuses grafted with calcium sulfate in 2 patients. Bone biopsies were harvested 9 months after the augmentation procedure. In the first patient, 3 titanium threaded-cylinder implants were placed in the grafted area after 9 months, while in the second, 1 acid-etched, screw-shaped titanium implant was placed simultaneously with the graft. Light microscopic evaluation revealed new bone formation with ongoing remodeling and progressive lamellar maturation in the specimens. No remnants of the alloplastic material were detectable in any section, either within the bone or in the medullary tissue. When reevaluated at the uncovering procedure, the implants were radiographically and clinically judged to be osseointegrated. These observations suggest that, when used in the appropriate form and with the proper technique, calcium sulfate is a promising graft material for sinus augmentation, producing adequate quantity and quality of new bone for implant placement.     

Osseointegration enhanced by chemical etching of the titanium surface. A torque removal study in the rabbit

Roughened implant surfaces are thought to enhance osseointegration. Torque removal forces have been used as a biomechanical measure of anchorage or osseointegration in which the greater forces required to remove implants may be interpreted as an increase in the strength of osseointegration. The purpose of this study was to compare the torque resistance to removal of screw shaped titanium implants having an acid etched (HC1/H2SO4) surface (Osseotite) with implants having a machined surface. Two custom screw shaped implants, 1 acid etched and the other machined, were placed into the distal femurs of 10 adult New Zealand White rabbits. These implants were 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Following a 2 month healing period, the implants were removed under reverse torque rotation with a digital torque measuring device. Two implants with the machined surface preparation failed to achieve osseointegration. All other implants were found to be anchored to bone. Resistance to torque removal was found to be 4 x greater for the implants with the acid etched surface as compared to the implants with the machined surface. The mean torque values were 20.50 +/- 6.59 N cm and 4.95 +/- 1.61 N cm for the acid etched and machined surfaces respectively. The results of this study suggest that chemical etching of the titanium implant surface significantly increases the strength of osseointegration as determined by resistance to reverse torque rotation.     

Surface-dimpled commercially pure titanium implant and bone ingrowth

The purpose of this investigation was to examine the effect of the surface macrostructure of a dimpled commercially pure titanium (cp Ti) implant on bone ingrowth in vivo by means of histological examination and a push-out test. Cylindrical implants were inserted in one femur of each experimental rabbit and the animals were killed at 1.5, 3 and 13 months after implantation. The femur with the implant of each animal was then examined in a push-out test. The fracture surfaces of the bone-implant interface after the push-out test were examined under light and electron microscopy. It seems that the dimpled cp Ti surface results in the increased retention of the cp Ti implant in bone due to interlocking between vital bone and the dimples.     

Morphology of the bone that supports endosteal dental implants. Transmission electron microscopic and high voltage electron microscopic observations

The morphologic features of the bone-dental implant interface were investigated using an in vivo dog model. The undecalcified bone and associated support tissues were serially sectioned and examined with both conventional and high voltage transmission electron microscopy. A varied morphologic appearance of the tissues supporting clinically and radiographically appearing integrated implants was observed. Osteoblasts were observed at the implant interface, and osteocytes were routinely seen encased within lacunae extremely close to the implant surface. Often these osteocytes extended cellular projections to the implant surface. The variable tissue types observed were suggestive of healthy lamellar and appositional type mineralization patterns adjacent to the implants.     

Cemented femoral component surface finish mechanics

A cemented femoral component's surface finish may influence implant function through variations in cement adhesion and abrasion properties. Morphologic characterization of historic and current femoral hip prosthesis surface finishes show greater than x 20 range in implant roughness. Early implants typically had relatively smooth surfaces, whereas many of the more recent implants have rougher surface finishes. Smoother implant surfaces have lower cement-metal interface fixation strength, whereas rougher surfaces have greater fixation strength. With interface motion, the smoother surfaces are less abrasive of bone cement, whereas rougher implant surfaces are more abrasive. Because of enhanced bone cement attachment, rougher implant surfaces may have a lower probability of interface motion, while at the same time, a higher debris generation consequence if motion occurs. In contrast, smoother implant surfaces may have a higher probability of interface motion with a lower debris generating consequence of that motion. The prolonged use of cemented total hip replacement may be approached by either extending the duration of implant function after cement-metal interface loosening with smooth surfaced implants or, in contrast, by extending the duration of cement-metal interface adhesion with rougher surfaced implants.     

Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials

This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant.     

Mechanical and histological fixation of hydroxylapatite-coated pyrolytic carbon and titanium alloy implants: a report of short-term results

Historically, pyrolytic carbon has been a material for cardiovascular applications, but it has several properties suited for orthopedic uses as well. Pyrolytic carbon has an elastic modulus similar to bone and is highly fatigue resistant, but has not been used in orthopedics because of poor fixation to bone. Plasma sprayed hydroxylapatite (HA) has significantly improved the bonding of bone to titanium alloy implants. The effect of plasma-sprayed HA on pyrolytic carbon implants was investigated in this study. Cylindrical samples were implanted through a single cortex in Beagle femurs. The animals were sacrificed after 8 weeks, and a mechanical push-out test was performed on the implants immediately after explantation. Samples were microradiographed, stained for histology, and examined histomorphometrically. Interface strength for each type of implant was calculated. Pyrolytic carbon showed almost no attachment strength with an average strength value of 1.59 MPa. HA-coated pyrolytic carbon (8.71 MPa) yielded the same interfacial strength as HA-coated titanium (8.71 MPa). Histology revealed that bone was in direct apposition to all implants, both HA coated and noncoated. Failures occurred between the core material and the coating, or within the coating, but not at the bone/HA interface. Histomorphometry results confirmed that the two types of HA-coated implants had more bone apposition than the uncoated pyrolytic carbon implants. It was concluded that a plasma sprayed HA coating significantly improves the bone fixation of pyrolytic carbon.     

Effect of a titanium surface on bone marrow-derived osteoblastic cells in vitro

The initial interaction between a titanium implant and the surrounding cancellous bone tissue was investigated by means of in vitro cultures of bone marrow-derived osteoblastic clone TMS-12 cells. Proliferation of TMS-12 cells cultured on a titanium surface was significantly reduced compared with that of control cells cultured directly on plastic, but alkaline phosphatase activity was the same as control cells. Co-culture of spleen cells with TMS-12 cells in the presence of a 1 alpha,25-dihydroxyvitamin D3 on titanium resulted in significant inhibition of tartrate-resistant acid phosphatase activity compared to control cultures on plastic. More prostaglandin E2 (PGE2) was produced by cells grown on a titanium surface than on plastic tissue-culture plates. On the other hand, mouse calvaria-derived osteogenic MC3T3-E1 cells, known to proliferate well on titanium, released similar amounts of PGE2 on titanium surfaces as on plastic tissue culture plates, indicating additional marked differences between the two osteoblastic cell types in response to a titanium surface. These results suggest that the reaction of bone marrow-derived osteoblastic cells to a titanium surface may fundamentally differ from that of calvaria-derived osteoblastics even though both cells are from bone tissue.     

In Situ Laser Coating of Calcium Phosphate on TC4 Surface for Enhancing Bioactivity

 Titanium alloy has been a successful implant material owing to its excellent ratio of strength to weight, toughness, and bio inert oxide surface. Significant progress has been made in improving the bioactivity of titanium alloy by coating its oxide surface with calcium phosphates. In the present study, in situ coating was reported on Ti6Al4V(TC4) surface with calcium phosphate (Ca P) bioceramics synthesized and synchronously cladded by laser beam. This coating was grown by first preplacing directly the raw powders, which contain 80% of CaHPO4·2H2O, 20% of CaCO3, and dram of rare earth (RE), on the TC4 surfaces, and then exposing the surfaces to the laser beam with a power density of 1273-1527 MW·m-2 and a scanning velocity of 105 m/s. The resultant coating was characterized using scanning electron microscopy (SEM), X ray diffraction (XRD), thermogravimetric analysis and Different thermal Scanning (TG DSC), and Energy Dispersive X ray Detection (EDX). The results show that these laser ceramics include hydroxyapatite (HA), tricalcium phosphate (TCP), Ca2P2O7, and other Ca P phases, and the interface between the coating and the TC4 substrate has tighter fixation, in which the chemical bonding is approved. These laser hybrid coatings are useful in enhancing the bioactivity of titanium alloy surfaces.     

Influence of metal implants on infection. An experimental study in rabbits

We implanted cylinders of cobalt-chrome or titanium, with smooth or porous surfaces, into rabbit bones which had been inoculated with suspensions of Staphylococcus aureus in various doses. The bacterial concentration required to produce infection of porous-coated titanium implants was 2.5 times smaller than that necessary to infect implants with polished surfaces. Porous-coated cobalt-chromium implants required bacterial concentrations that were 40 times smaller than those needed to infect implants with polished surfaces, and 15 times smaller than those required to infect porous-coated titanium implants. The other advantages and disadvantages of the various implants, such as improved osseointegration, larger ion-release surfaces, surface wear and relative stiffness, must be weighed against the higher infection rates in the porous-coated implants, and particularly in the cobalt-chromium implants.     

Adenosquamous carcinoma of the tongue: report of a case with histochemical, immunohistochemical, and ultrastructural study and review of the literature

The histologic examination of dental implants retrieved from humans is important to establish the causal determinants of implant failure, and to compare and validate the results obtained from animal studies. This study presents a retrospective review of the histologic features of 230 implants retrieved in an 8-year period (1989-1996). All the implants were treated to obtain thin (20 to 30 microm) ground sections. The majority of implants were retrieved because of mobility (n=56), peri-implantitis (n=54), or fractures (n=90). Peri-implantitis occurred more frequently before (n=44) than after (n=10) abutment connection. A dense fibrous connective tissue with no inflammatory cells was present at the interface in the implants retrieved for mobility; bone was found only in the most apical part. In many of these implants epithelial cells were present. The main histologic features of peri-implantitis consisted of the presence of a bone sequestrum near the implant, many bacteria present on the implant surface, and an inflammatory infiltrate (macrophages, lymphocytes, and plasma-cells) nearby. Histology showed that in the implants removed for fracture, there was a very high percentage (80 to 100%) of peri-implant bone.