Localized chronic suppurative bone infection as a sequel of peri-implantitis in a hydroxyapatite-coated dental implant

Role of New Hydrophilic Surfaces on Early Success Rate and Implant Stability: 1-Year Post-loading Results of a Multicenter, Split-Mouth, Randomized Controlled Trial

OBJECTIVE

 To compare early implant failure and implant stability of one-stage Hiossen ET III implants with its new hydrophilic (NH) surface, compared with Hiossen ET III implants with the sandblasted and acid-etched (SA) surface at 1-year follow-up.

MATERIALS AND METHODS

 This study was designed as a split-mouth, multicenter randomized controlled trial aimed to compare SA surface implants (SA group) and NH surface, (NH group). Outcomes were implant and prosthetic survival rates, complications, the insertion torque at implant placement, and implant stability quotient (ISQ) values.

RESULTS

 Twenty-nine patients (mean age 59.9 ± 11.3 years) were treated and followed up to 1 year after loading. No patient dropped out. Fifty-eight implants (29 SA group and 29 NH group) were placed. No implants or prostheses failed and no complications were experienced during follow-up. The mean insertion torque was 40.5 ± 3.23 (38.17-41.83) Ncm in the SA group and 40.48 ± 3.49 (38.02-41.98) Ncm in the NH group (p = 0.981). There was a statistically significant difference at the second week (T2) with higher values in the NH group (p = 0.041). Similar results were found in the maxilla (p = 0.045), but not in the mandible (p = 0.362). A positive correlation was found between initial insertion torque and ISQ with higher value in the NH group (0.73 vs. 0.66).

CONCLUSIONS

 NH implants are a viable alternative to SA surface, as they seem to avoid the ISQ drop during the bone remodeling phase.

Non-Invasive Luciferase Imaging of Type I Interferon Induction in a Transgenic Mouse Model of Biomaterial Associated Bacterial Infections: Microbial Specificity and Inter-Bacterial Species Interactions

The performance of biomaterials is often compromised by bacterial infections and subsequent inflammation. So far, the conventional analysis of inflammatory processes in vivo involves time-consuming histology and biochemical assays. The present study employed a mouse model where interferon beta (IFN-β) is monitored as a marker for non-invasive rapid detection of inflammation in implant-related infections. The mouse model comprises subcutaneous implantation of morphologically modified titanium, followed by experimental infections with four taxonomically diverse oral bacteria: Streptococcus oralis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Treponema denticola (as mono culture or selected mixed-culture). IFN-β expression increased upon infections depending on the type of pathogen and was prolonged by the presence of the implant. IFN-β expression kinetics reduced with two mixed species infections when compared with the single species. Histological and confocal microscopy confirmed pathogen-specific infiltration of inflammatory cells at the implant-tissue interface. This was observed mainly in the vicinity of infected implants and was, in contrast to interferon expression, higher in infections with dual species. In summary, this non-invasive mouse model can be used to quantify longitudinally host inflammation in real time and suggests that the polymicrobial character of infection, highly relevant to clinical situations, has complex effects on host immunity.

The Impact of Engineered Silver Nanomaterials on the Immune System

Over the last decades there has been a tremendous volume of research efforts focused on engineering silver-based (nano)materials. The interest in silver has been mostly driven by the element capacity to kill pathogenic bacteria. In this context, the main area of application has been medical devices that are at significant risk of becoming colonized by bacteria and subsequently infected. However, silver nanomaterials have been incorporated in a number of other commercial products which may or may not benefit from antibacterial protection. The rapid expansion of such products raises important questions about a possible adverse influence on human health. This review focuses on examining currently available literature and summarizing the current state of knowledge of the impact of silver (nano)materials on the immune system. The review also looks at various surface modification strategies used to generate silver-based nanomaterials and the immunomodulatory potential of these materials. It also highlights the immune response triggered by various silver-coated implantable devices and provides guidance and perspective towards engineering silver nanomaterials for modulating immunological consequences.

Do the New Hydrophilic Surface Have Any Influence on Early Success Rate and Implant Stability during Osseointegration Period? Four-Month Preliminary Results from a Split-Mouth, Randomized Controlled Trial

OBJECTIVE

The objective of this study is to compare the implant stability of Hiossen ET III implants with its new hydrophilic (NH) surface and Hiossen ET III implants with the sandblasted and acid-etched (SA) surface.

MATERIALS AND METHODS

Patients required at least two teeth to be rehabilitated with a fixed, implant-supported restoration, consecutively enrolled. Patients randomly received SA surface implants (SA group) or SA implants with a newly developed bioabsorbable apatite nanocoating (NH group). Outcome measures were implant and prosthetic survival rate, complications, insertion torque, and implant stability quotient (ISQ) measured at implant placement and every week up to 8 weeks after implant placement. Comparison between groups was made by unpaired t-test, while the comparison between each follow-up will be made by paired t-tests to detect any change during the follow-up. Complications and failures were compared using Fisher's exact test.

RESULTS

A total of 14 patients were treated with 28 implants (14 SA and 14 NH). No implant and prosthesis failed 4 months after implant placement. No complications were experienced. At the 2nd week after implants placement, two implants in the SA group showed discontinuous measurements versus none in the NH group (p = 0.4815). Implants unscrewed during ISQ measurements and were rescrewed. Data recording stopped for 6 weeks. Both implants osseointegrated without any further complication. The NH implants did not show physiological ISQ decrease between 2nd and 4th week after implant placement, showing a more even pattern of ISQ values compared with SA implants (77.1 ± 4.6 vs. 72.9 ± 11.5; difference: 4.2 ± 12.1; p = 0.258). High ISQ values were found in both groups at each time point.

CONCLUSIONS

NH implants are a viable alternative to SA surface, as they seem to avoid the ISQ drop during the remodeling phase.

Comparison of peri-implant and periodontal marginal soft tissues in health and disease

The integrity of the peri-implant soft-tissue seal is crucial for maintaining peri-implant tissue health. Whilst the transmucosal component of the restored implant shares some common features with teeth, namely the presence of a junctional epithelium and a connective tissue component, there are some important differences. A key difference is the nature of the relationship of the connective tissue with the implant surface, whereby there is 'adaptation' of collagen fibers in a parallel orientation in relation to the implant, but insertion of fiber attachment perpendicularly into cementum in the case of teeth. This, combined with reduced cellularity and vascularity in the peri-implant connective tissue, may make implants more susceptible to disease initiation and progression. Furthermore, the presence of a subgingival connection between the implant and the abutment/restoration poses some specific challenges, and maintaining the integrity of this connection is important in preserving peri-implant tissue health. Implant design features, such as the nature of the connection between the implant and the abutment, as well as the surface characteristics of the abutment and implants, may influence the maintenance of the integrity of soft tissue around implants. Iatrogenic factors, such as incorrect seating of the abutment and/or the restoration, and the presence of residual subgingival cement, will lead to loss of soft-tissue integrity and hence predispose to peri-implant disease.

Evaluation of osseous integration of titanium orthopedic screws with novel SLA treatment in porcine model

The success of many endosseous implants in orthopaedic and dental applications depends on the surface characteristics, as they affect osseous integration. Previous investigations indicated that a novel large-grit sand-blasted and acid-etched (SLA) titanium (denoted as SLAffinity-Ti) implant had better bone integration than that of a comparably shaped implant with a plasma-sprayed titanium surface. The purpose of the present investigation was to create a SLAffinity surface on pedicle screws and trauma screws and to compare it with the surfaces of a sand-blasted-only implant and commercial implants in terms of bone integration. The cortical bone and spine of twelve minipigs were implanted with 3 and 4 implants, respectively, and the bone integration was evaluated using micro-computed tomography (micro-CT), mechanical tests (pull-out strength and stripping torque), and histological analysis (toluidine blue and hematoxylin and eosin staining) one and three months after implantation. The micro-CT images showed that the gap between the bone and implant was consistently higher in the sand-blasted-only and commercial groups compared to that in the SLAffinity group 1 and 3 months after implantation. Moreover, the bone volume of implant inserted into bone and the percentage of implant inside bone tissue were greater in the SLAffinity screws 1 and 3 months after implantation, as compared to the sand-blasted and commercial screws. In the mechanical tests, the removal torque and pull-out strength (p < 0.05) were higher in the SLAffinity group at 1 and 3 months. The histological results were consistent with mechanical testing, showing that the SLAffinity group had the most mineralized matrix, the most bone formation around the screws, and the most bone cells in bone tissue. These findings indicate that a SLAffinity surface can effectively enhance the holding strength and integration of pedicle screws and cortical screws, promoting early healing and improving outcomes, compared to sand-blasted-only and commercial implants.

Chitosan-Recombinamer Layer-by-Layer Coatings for Multifunctional Implants

The main clinical problems for dental implants are (1) formation of biofilm around the implant—a condition known as peri-implantitis and (2) inadequate bone formation around the implant—lack of osseointegration. Therefore, developing an implant to overcome these problems is of significant interest to the dental community. Chitosan has been reported to have good biocompatibility and anti-bacterial activity. An osseo-inductive recombinant elastin-like biopolymer (P-HAP), that contains a peptide derived from the protein statherin, has been reported to induce biomineralization and osteoblast differentiation. In this study, chitosan/P-HAP bi-layers were built on a titanium surface using a layer-by-layer (LbL) assembly technique. The difference in the water contact angle between consecutive layers, the representative peaks in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and the changes in the topography between surfaces with a different number of bi-layers observed using atomic force microscopy (AFM), all indicated the successful establishment of chitosan/P-HAP LbL assembly on the titanium surface. The LbL-modified surfaces showed increased biomineralization, an appropriate mouse pre-osteoblastic cell response, and significant anti-bacterial activity against Streptococcus gordonii, a primary colonizer of tissues in the oral environment.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

Since various interactions among cells, surrounding tissues and implanted biomaterials always occur at their interfaces, the surface properties of potential implants appear to be of paramount importance for the clinical success. In view of the fact that a limited amount of materials appear to be tolerated by living organisms, a special discipline called surface engineering was developed to initiate the desirable changes to the exterior properties of various materials but still maintaining their useful bulk performances. In 1975, this approach resulted in the introduction of a special class of artificial bone grafts, composed of various mechanically stable (consequently, suitable for load bearing applications) implantable biomaterials and/or bio-devices covered by calcium orthophosphates (CaPO4) to both improve biocompatibility and provide an adequate bonding to the adjacent bones. Over 5000 publications on this topic were published since then. Therefore, a thorough analysis of the available literature has been performed and about 50 (this number is doubled, if all possible modifications are counted) deposition techniques of CaPO4 have been revealed, systematized and described. These CaPO4 deposits (coatings, films and layers) used to improve the surface properties of various types of artificial implants are the topic of this review.

Surface characteristics and bioactivity of a novel natural HA/zircon nanocomposite coated on dental implants

The surface characteristics of implant which influence the speed and strength of osseointegration include surface chemistry, crystal structure and crystallinity, roughness, strain hardening, and presence of impurities. The aim of this study was to evaluate the bioactivity and roughness of a novel natural hydroxyapatite/zircon (NHA/zircon) nanobiocomposite, coated on 316L stainless steel (SS) soaked in simulated body fluid (SBF). NHA/zircon nanobiocomposite was fabricated with 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% of zircon in NHA using ball mill for 20 minutes. The composite mixture was coated on 316L SS using plasma spray method. The results are estimated using the scanning electron microscopy (SEM) observation to evaluate surface morphology, X-ray diffraction (XRD) to analyze phase composition, and transmission electron microscopy (TEM) technique to evaluate the shape and size of prepared NHA. Surfaces roughness tester was performed to characterize the coated nanocomposite samples. The maximum average R a (14.54 μm) was found in the NHA 10 wt.% of zircon coating. In addition, crystallinity (X c ) was measured by XRD data, which indicated the minimum value (X c = 41.1%) for the sample containing 10 wt.% of zircon. Maximum bioactivity occurred in the sample containing 10 wt.% of zircon, which was due to two reasons: first, the maximum roughness and, second, the minimum crystallinity of nanobiocomposite coating.

Histopathological spectrum of bone lesions associated with dental implant failure: osteomyelitis and beyond

Early or late post-implant placement complications are usually localized infectious/inflammatory processes and treated accordingly. If the healing process does not take place within a reasonable timeframe, the possibility of a pathologic process beyond localized infection/inflammation should be suspected. We describe a radiological/histopathological spectrum of bony lesions ranging from inflammatory to malignant lesions surrounding failed dental implants. Five cases of mandibular dental implant failure that clinically, radiologically and histopathologically appeared to be inflammatory processes are presented. The failure of the dental implants was immediate in two cases and late in the remaining three. The radiological features were essentially similar for all five, and they included radiolucent or mixed radiolucent-radiopaque lesions with poorly defined borders. Three lesions were limited to the area of the failed implant, while the other two extended to a large part of the mandible. The histopathological findings ranged from acute osteomyelitis and chronic osteomyelitis with features of a fibro-osseous-like lesion and occasional rimming of atypical osteoblasts to osteogenic sarcoma that was admixed with a component of osteomyelitis (diagnosis of the latter was achieved only after a series of biopsies). In-depth investigative procedures are imperative in order to establish an accurate diagnosis whenever the histopathological diagnosis is inconsistent with persisting clinical signs and symptoms in bone lesions associated with failed dental implants.

Significance of calcium phosphate coatings for the enhancement of new bone osteogenesis--a review

A systematic analysis of results available from in vitro, in vivo and clinical trials on the effects of biocompatible calcium phosphate (CaP) coatings is presented. An overview of the most frequently used methods to prepare CaP-based coatings was conducted. Dense, homogeneous, highly adherent and biocompatible CaP or hybrid organic/inorganic CaP coatings with tailored properties can be deposited. It has been demonstrated that CaP coatings have a significant effect on the bone regeneration process. In vitro experiments using different cells (e.g. SaOS-2, human mesenchymal stem cells and osteoblast-like cells) have revealed that CaP coatings enhance cellular adhesion, proliferation and differentiation to promote bone regeneration. However, in vivo, the exact mechanism of osteogenesis in response to CaP coatings is unclear; indeed, there are conflicting reports of the effectiveness of CaP coatings, with results ranging from highly effective to no significant or even negative effects. This review therefore highlights progress in CaP coatings for orthopaedic implants and discusses the future research and use of these devices. Currently, an exciting area of research is in bioactive hybrid composite CaP-based coatings containing both inorganic (CaP coating) and organic (collagen, bone morphogenetic proteins, arginylglycylaspartic acid etc.) components with the aim of promoting tissue ingrowth and vascularization. Further investigations are necessary to reveal the relative influences of implant design, surgical procedure, and coating characteristics (thickness, structure, topography, porosity, wettability etc.) on the long-term clinical effects of hybrid CaP coatings. In addition to commercially available plasma spraying, other effective routes for the fabrication of hybrid CaP coatings for clinical use still need to be determined and current progress is discussed.

Improved bonding of partially osteomyelitic bone to titanium pins owing to biomimetic coating of apatite

Increased fixation strength of the bone-pin interface is important for inhibiting pin loosening after external fixation. In a previous study, an apatite (Ap) layer was formed on anodically oxidized titanium (Ti) pins by immersing them in an infusion fluid-based supersaturated calcium phosphate solution at 37 °C for 48 h. In the present study, an Ap layer was also successfully formed using a one-step method at 25 °C for 24 h in an infusion fluid-based supersaturated calcium phosphate solution, which is clinically useful due to the immersion temperature [corrected]. After percutaneous implantation in a proximal tibial metaphysis for four weeks in rabbits (n = 20), the Ti pin coated with the Ap layer showed significantly increased extraction torque compared with that of an uncoated Ti screw even with partial osteomyelitis present, owing to dense bone formation on the Ap layer in the cortical and medullary cavity regions. When the infection status was changed from "no osteomyelitis" to "partial osteomyelitis," the extraction torque in the Ap group with "partial osteomyelitis" was almost identical to that for "no osteomyelitis" cases. These results suggest that the Ap layer formed by the room temperature process could effectively improve the fixation strength of the Ti pin for external fixation clinically even with partial osteomyelitis present.

Antimicrobial surfaces for craniofacial implants: state of the art

In an attempt to regain function and aesthetics in the craniofacial region, different biomaterials, including titanium, hydroxyapatite, biodegradable polymers and composites, have been widely used as a result of the loss of craniofacial bone. Although these materials presented favorable success rates, osseointegration and antibacterial properties are often hard to achieve. Although bone-implant interactions are highly dependent on the implant's surface characteristics, infections following traumatic craniofacial injuries are common. As such, poor osseointegration and infections are two of the many causes of implant failure. Further, as increasingly complex dental repairs are attempted, the likelihood of infection in these implants has also been on the rise. For these reasons, the treatment of craniofacial bone defects and dental repairs for long-term success remains a challenge. Various approaches to reduce the rate of infection and improve osseointegration have been investigated. Furthermore, recent and planned tissue engineering developments are aimed at improving the implants' physical and biological properties by improving their surfaces in order to develop craniofacial bone substitutes that will restore, maintain and improve tissue function. In this review, the commonly used biomaterials for craniofacial bone restoration and dental repair, as well as surface modification techniques, antibacterial surfaces and coatings are discussed.

Calcium orthophosphate coatings, films and layers

In surgical disciplines, where bones have to be repaired, augmented or improved, bone substitutes are essential. Therefore, an interest has dramatically increased in application of synthetic bone grafts. As various interactions among cells, surrounding tissues and implanted biomaterials always occur at the interfaces, the surface properties of the implants are of the paramount importance in determining both the biological response to implants and the material response to the physiological conditions. Hence, a surface engineering is aimed to modify both the biomaterials, themselves, and biological responses through introducing desirable changes to the surface properties of the implants but still maintaining their bulk mechanical properties. To fulfill these requirements, a special class of artificial bone grafts has been introduced in 1976. It is composed of various mechanically stable (therefore, suitable for load bearing applications) biomaterials and/or bio-devices with calcium orthophosphate coatings, films and layers on their surfaces to both improve interactions with the surrounding tissues and provide an adequate bonding to bones. Many production techniques of calcium orthophosphate coatings, films and layers have been already invented and new promising techniques are continuously investigated. These specialized coatings, films and layers used to improve the surface properties of various types of artificial implants are the topic of this review.

Biomaterial and antibiotic strategies for peri-implantitis: a review

Dental implants have 89% plus survival rates at 10-15 years, but peri-implantitis or dental implant infections may be as high as 14%. Peri-implantitis can limit clinical success and impose health and financial burdens to patients and health providers. The pathogenic species associated with periodontitis (e.g., Fusobacterium ssp, A. actinomycetemcomitans, P. gingivalis) are also associated with peri-implantitis. Incidence of peri-implantitis is highest within the first 12 months after implantation, and is higher in patients who smoke or have poor oral health as well as with calcium-phosphate-coated or surface-roughened implants. Biomaterial therapies using fibers, gels, and beads to deliver antibiotics have been used in the treatment of Peri-implantitis though clinical efficacy is not well documented. Guided tissue regeneration membranes (e.g., collagen, poly-lactic/glycolic acid, chitosan, ePTFE) loaded with antimicrobials have shown success in reosseointegrating infected implants in animal models but have not been proven in humans. Experimental approaches include the development of anti-bioadhesion coatings, coating surfaces with antimicrobial agents (e.g., vancomycin, Ag, Zn) or antimicrobial releasing coatings (e.g., calcium phosphate, polylactic acid, chitosan). Future strategies include the development of surfaces that become antibacterial in response to infection, and improvements in the permucosal seal. Research is still needed to identify strategies to prevent bacterial attachment and enhance normal cell/tissue attachment to implant surfaces.

Titanium Dental Implant Surface Micromorphology Optimization

The purpose of this investigation was to create an acid-etched implant surface that is similar to that created by sandblasting combined with acid etching and to compare it with the surfaces of various commercially available screw-type implants. Titanium grade 5 disks were machined in preparation for acid etching. Tests were carried out using different acids and combinations of them with varying time exposures. All etched surfaces were scanned with an electron microscope, and digital images were created for visual evaluation and description of the surfaces. The etched surfaces were evaluated for surface morphology (combination of microroughness and waviness); the surface most like the sandblasted/acid-etched surface was best obtained with a combination of sulfuric and hydrochloric acids. The etched titanium disks were fixed in acrylic resin (2 were cut and polished and 2 were scored and fractured) and the surface profile was examined. In the second part of the investigation, 28 screw-shaped implants that were manufactured from commercially available titanium grade 5 were selected and divided into 2 groups: 3 implants were used as controls (machined surface), and 25 implants were processed using the preferred etching method determined in the first part of the investigation. Magnifications of 27, 200, and 2000 were used to analyze the first 2 consecutive crests of threads, flanks, and root of threads of each implant with the treated surface. A 3-dimensional optical interferometer was used to characterize the surface roughness of both control and test groups. Three screws were selected from each group and measured at 9 sites: 3 measurements each on the crest, root, and flank of the threads. To describe the surface roughness in numbers, the following parameters were used: the average height deviation (Sa), the developed interfacial area ratio (Sdr), the fastest decay autocorrelation length (Sal), and the density of summits (Sds). In addition, in a third experiment, the surfaces of 5 commercially available screw-type implants and the experimental ones were analyzed and compared. It was concluded that the new experimental acid-etched titanium surface had the features of a roughened titanium surface, with glossily microroughness and large waviness. In general, the experimental surface was significantly rougher than the selected commercially available implants and similar to a sandblasted/acid-etched surface (top Sa: 2.08 +/- 0.36 microm, Sdr: 1.34 +/- 0.3 microm, valleys: 1.16 +/- 0.1 microm and 0.68 +/- 0.1 microm, flanks: 2.24 +/- 0.8 microm and 1.27 +/- 0.1 microm, respectively).

Submental Cutaneous Sinus Tract as a Result of Progressive Peri-Implantitis: A Case Report

BACKGROUND

The aim of the present case report was to define diagnosis and treatment options of a submental cutaneous sinus tract as a result of a progressive peri-implantitis around mandibular dental implants in a patient with a history of oral squamous cell carcinoma.

METHODS

Before the removal of the submental fistula, a panoramic radiograph and a computed tomography of the head and neck were assessed to identify the implants responsible for the cutaneous sinus tract and to exclude the presence of a tumor recurrence and lymph node metastases. The involved implants were removed, as there was a communication along them between the oral cavity and the cutaneous sinus tract resulting from progressive peri-implantitis. A histological examination of the excised fistula was carried out.

RESULTS

The histological examination excluded a recurrence of the oral squamous cell carcinoma. The fistula completely consisted of granulation tissue without epithelialization. After affected implants were removed, the wound healing was uneventful.

CONCLUSIONS

A panoramic radiograph is mandatory to identify the involved implants. Computed tomography, and excision of the fistula and a histological examination should be performed only in patients with a history of oral squamous cell carcinoma. Since the cutaneous sinus tract showed no epithelialization, it healed spontaneously after the removal of the responsible implants. Because of the large bony defect caused by progressive peri-implantitis leading to a communication of the oral cavity with the cutaneous sinus tract, more conservative treatment options with preservation of the implants could not be adopted in the present case.

Optimal implant stabilization in low density bone

Initial stability of the implant is one of the fundamental criteria for obtaining osseointegration. An adequate primary anchorage is often difficult to achieve in low density bone (type IV). Various surgical suggestions were advanced in the 1980s which were aimed at achieving optimal osseous integration in poor quality bone. They offered satisfactory short-term results. Recently, as a result of surgical and technological innovations, new therapeutic proposals have shown very interesting results in their initial studies.

Histopathologic observations on late oral implant failures

BACKGROUND

Despite good success rates of osseointegrated oral implants, failures do occur. To minimize losses, failure mechanisms should be elucidated.

PURPOSE

This study sought to describe the morphology of tissues surrounding late failed Brånemark implants in relation to their clinical and radiographic findings to acquire a better understanding of the etiologic factors.

MATERIAL AND METHODS

Ten failed implants and their surrounding tissues were consecutively retrieved from nine patients after prosthesis placement (late losses). On radiographs, a radiolucent line was visible around nine clinically mobile implants. Tightening of the abutment screw evoked pain at seven mobile implants. Clinically, no other visual inflammatory sign or symptom was manifest. A fistula originated from one stable implant, surrounded on radiographs by a diffuse bone rarefaction. Retrieved implants were electrochemically dissolved. Intact tissue-implant thin (1 micron) and ultrathin (70-80 nm) sections were analyzed with light and transmission electron microscopy.

RESULTS

Peri-implant marginal tissues displayed moderate inflammatory infiltrates located adjacent to and beneath the junctional epithelium. One patient affected by oral lichen planus displayed an intense lymphocyte/plasma cell-dominated immune reaction. Deep peri-implant tissues surrounding mobile implants consisted of a dense, fibrous tissue capsule with minimal inflammation. Epithelial downgrowth was observed around four implants. Small areas of nonmineralized bone in contact with the implant were noticed in the apical portion of two implants. One implant was almost entirely colonized by bacterial plaque with the exception of its apical portion, where bone-implant contact was observed. The stable implant was characterized by bone-implant contact.

CONCLUSION

Altogether clinical, radiographic, and histologic findings indicated that two major etiologic factors might have been implicated in the failure process of the investigated implants: excessive occlusal load in relation to the bone-supporting capacity and, in two cases, infection.

A methodological study for the analysis of apatite-coated dental implants retrieved from humans

The stability of thermally processed hydroxyapatite coatings for oral and orthopedic bioprostheses has been questioned. Information on the chemical changes, which occur with hydroxyapatite biomaterials post-implantation in humans, is lacking. The purpose of this investigation was to begin to examine post-implantation surface changes of hydroxyapatite-coated implants using scanning electron microscopy (SEM), x-ray microanalysis (EDAX), Fourier transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD). Three retrieved dental implant specimens from humans following clinical failure due to peri-implantitis were examined. Unimplanted cylinders served as controls. Clinically, the retrieved specimens were all enveloped by a fibrous tissue capsule with bone present at the apical extent of the implant. SEM analysis showed that the retrieved surfaces were coated with both calcified and proteinaceous deposits. EDAX scans of the retrieved specimens demonstrated evidence of hydroxyapatite coating loss reflected by increasing titanium and aluminum signals. Other foreign ions such as sodium, chloride, sulfur, silica, and magnesium were detected. XRD of the control specimens showed that the samples were predominantly apatite; however, two peaks were detected in the diffraction pattern, which are not characteristic of hydroxyapatite, indicating that small amounts of one or more other crystalline phases were also present. The retrieved specimens showed slightly larger average crystal size relative to the control sample material, and the non-apatite lines were not present. FTIR evaluation of the retrieved specimens revealed the incorporation of carbonate and organic matrix on or into the hydroxyapatite. Narrowing of and increased detail in the phosphate peaks indicated an increase in average crystal size and/or perfection relative to the controls, as did the XRD results. Based on these results, we conclude that chemical changes may occur within the coating, with the incorporation of carbonate and concomitant reduction in hydroxyapatite coating thickness. Thermodynamic dissolution-reprecipitation of the coating itself and subsequent surface insult by bacterial and local inflammatory components may be involved with these changes.

Histologic observations on 230 retrieved dental implants: 8 years' experience (1989-1996)

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.