Strategies for Improving Impaired Osseointegration in Compromised Animal Models.

Implant osseointegration is reduced in patients with systemic conditions that compromise bone quality, such as osteoporosis, disuse syndrome, and type 2 diabetes. Studies using rodent models designed to mimic these compromised conditions demonstrated reduced bone-to-implant contact (BIC) or a decline in bone mineral density. These adverse effects are a consequence of disrupted intercellular communication. A variety of approaches have been developed to compensate for the altered microenvironment inherent in compromised conditions, including the use of biologics and implant surface modification. Chemical and physical modification of surface properties at the microscale, mesoscale, and nanoscale levels to closely resemble the surface topography of osteoclast resorption pits found in bone has proven to be a highly effective strategy for improving implant osseointegration. The addition of hydrophilicity to the surface further enhances osteoblast response at the bone-implant interface. These surface modifications, applied either alone or in combination, improve osseointegration by increasing proliferation and osteoblastic differentiation of osteoprogenitor cells and enhancing angiogenesis while modulating osteoclast activity to achieve net new bone formation, although the specific effects vary with surface treatment. In addition to direct effects on surface-attached cells, the communication between bone marrow stromal cells and immunomodulatory cells is sensitive to these surface properties. This article reports on the advances in titanium surface modifications, alone and in combination with novel therapeutics in animal models of human disease affecting bone quality. It offers clinically translatable perspectives for clinicians to consider when using different surface modification strategies to improve long-term implant performance in compromised patients. This review supports the use of surface modifications, bioactive coatings, and localized therapeutics as pragmatic approaches to improve BIC and enhance osteogenic activity from both structural and molecular standpoints.

A scoring system to evaluate stability of percutaneous osseointegrated implants for transfemoral amputation with validation in the ITAP clinical trial.

Percutaneous osseointegrated implants for individuals with lower limb amputation can increase mobility, reduce socket related pain, and improve quality of life. It would be useful to have an evaluation method to assess the interface between bone and implant. We assessed outpatient radiographs from the Intraosseous Transcutaneous Amputation Prosthesis clinical trial using an interface scoring system which summed and weighted equally measures of implant collar cortical ongrowth and radiolucency along the implant stem/bone interface. Radiographs from 12 participants with unilateral transfemoral amputations (10 males, 2 females, mean age = 43.2, SD = 7.4 years) in the clinical trial from cohort I (implanted in 2008/09) or cohort II (implanted in 2013/14) were collated (mean image span = 7.2, SD = 2.4 years), scale normalised, zoned, and measured in a repeatable way. Interface scores were calculated and then compared to clinical outcomes. Explanted participants received the lowest interface scores. A higher ratio of stem to residuum and shorter residuum's produced better interface scores and there was an association (weak correlation) between participants with thin cortices and the lowest interface scores. A tapered, cemented, non curved stem may provide advantageous fixation while stem alignment did not appear critical. In summary, the interface score successfully demonstrated a non-invasive evaluation of percutaneous osseointegrated implants interfaces when applied to the Intraosseous Transcutaneous Amputation Prosthesis clinical trial. The clinical significance of this work is to identify events leading to aseptic or septic implant removal and contribute to clinical guidelines for monitoring rehabilitation, design and surgical fixation choices.

The assessment of implant shape-dependent failure mechanisms in primary total hip arthroplasty using finite element analysis.

The three mechanisms known to be responsible for the failure of uncemented femoral stems in primary total hip arthroplasty (THA) are the stress shielding, excessive bone-implant interface stress, and excessive initial micromotion. Since implant designers usually have to sacrifice two mechanisms to improve the other one, the aim of this study was to assess which of them plays a more important role in the failure of uncemented stems. Two hip implant stems which are widely used in the primary THA and their mid-term clinical outcomes are available, were selected. Then, the amount of the three failure mechanisms created by each stem during the normal walking gait cycle was determined for a 70 kg female patient using the finite element method. The results indicated that the stem with better clinical outcome induced an average of 36.6% less stress shielding in the proximal regions of femur bone compared with the other stem. However, the maximum bone-implant interface stress and maximum initial micromotion were, respectively, 30 and 155% higher for the stem with better clinical outcomes. It was therefore concluded that the stress shielding has a more significant impact on the mid-term life of uncemented stems. However, care must be taken to ensure that the other two failure mechanisms do not exceed a certain threshold. It was also observed that the thinner and shorter stem created a smaller amount of stress shielding in the femur bone. The outcomes of this study can be used to design new hip implant stems that can potentially last longer.

Quantifying the immediate post-implantation strain field of cadaveric tibiae implanted with cementless tibial trays: A time-elapsed micro-CT and digital volume correlation analysis during stair descent.

Primary stability, the mechanical fixation between implant and bone prior to osseointegration, is crucial for the long-term success of cementless tibial trays. However, little is known about the mechanical interplay between the implant and bone internally, as experimental studies quantifying internal strain are limited. This study employed digital volume correlation (DVC) to quantify the immediate post-implantation strain field of five cadaveric tibiae implanted with a commercially available cementless titanium tibial tray (Attune, DePuy Synthes). The tibiae were subjected to a five-step loading sequence (0-2.5 bodyweight, BW) replicating stair descent, with concomitant time-elapsed micro-CT imaging. With progressive loads, increased compression of trabecular bone was quantified, with the highest strains directly under the posterior region of the tibial tray implant, dissipating with increasing distance from the bone-implant interface. After load removal of the last load step (2.5BW), residual strains were observed in all of the five tibiae, with residual strains confined within 3.14 mm from the bone-implant interface. The residual strain is reflective of the observed initial migration of cementless tibial trays reported in clinical studies. The presence of strains above the yield strain of bone accepted in literature suggests that inelastic properties should be included within finite element models of the initial mechanical environment. This study provides a means to experimentally quantify the internal strain distribution of human tibia with cementless trays, increasing the understanding of the mechanical interaction between bone and implant.

An analytical model to measure dental implant stability with the Advanced System for Implant Stability Testing (ASIST).

A non-invasive method of quantitatively assessing dental implant stability is important to monitor its long-term health. The Advanced System for Implant Stability Testing (ASIST) is a noninvasive technique that couples the impact technique with a linear vibration model of the implant system, such that the measured signal can be used to determine a matching analytical response. The purpose of this study was to evaluate the ASIST technique by comparing stability estimates obtained from artificial implant installations with various abutments. Two Straumann dental implants were installed in four densities of uniform polyurethane foam, and the stability of each installation was measured using different healing abutments and artificial dental crowns. With the ASIST, values for the estimated interfacial stiffness increased with foam density and did not significantly change with abutment type for a specific sample. This provides evidence that the analytical model is representative of the physical system. Current methods, such as resonance frequency analysis, interpret the interface stiffness based on a single frequency measurement. With the ASIST, the measured signal provides information about the first and second modes of vibration of the implant system, both of which are influenced by the properties of the corresponding abutment. The consideration of both modes allows the technique to reliably measure the interfacial stiffness independently of the system components. As a result, the ASIST technique may provide an improved non-invasive method of measuring the stability of dental implants.

Antibiotic prophylaxis dysregulates dental implant placement surgery-induced osteoimmune wound healing and attenuates the alveolar bone-implant interface in mice.

AIM: Antimicrobial-induced shifts in commensal oral microbiota can dysregulate helper T-cell oral immunity to affect osteoclast-osteoblast actions in alveolar bone. Antibiotic prophylaxis is commonly performed with dental implant placement surgery to prevent post-surgical complications. However, antibiotic prophylaxis effects on osteoimmune processes supporting dental implant osseointegration are unknown. The aim of the study was to discern the impact of antibiotic prophylaxis on dental implant placement surgery-induced osteoimmune wound healing and osseointegration. MATERIALS AND METHODS: We performed SHAM or dental implant placement surgery in mice. Groups were administered prophylactic antibiotics (amoxicillin or clindamycin) or vehicle. Gingival bacteriome was assessed via 16S sequencing. Helper T-cell oral immunity was evaluated by flow cytometry. Osteoclasts and osteoblasts were assessed via histomorphometry. Implant osseointegration was evaluated by micro-computed tomography. RESULTS: Dental implant placement surgery up-regulated TH 1, TH 2 and TREG cells in cervical lymph nodes (CLNs), which infers helper T-cell oral immunity contributes to dental implant placement osseous wound healing. Prophylactic antibiotics with dental implant placement surgery caused a bacterial dysbiosis, suppressed TH 1, TH 2 and TREG cells in CLNs, reduced osteoclasts and osteoblasts lining peri-implant alveolar bone, and attenuated the alveolar bone-implant interface. CONCLUSIONS: Antibiotic prophylaxis dysregulates dental implant placement surgery-induced osteoimmune wound healing and attenuates the alveolar bone-implant interface in mice.

Functionally Tailored Metal-Organic Framework Coatings for Mediating Ti Implant Osseointegration.

Owing to their mechanical resilience and non-toxicity, titanium implants are widely applied as the major treatment modality for the clinical intervention against bone fractures. However, the intrinsic bioinertness of Ti and its alloys often impedes the effective osseointegration of the implants, leading to severe adverse complications including implant loosening, detachment, and secondary bone damage. Consequently, new Ti implant engineering strategies are urgently needed to improve their osseointegration after implantation. Remarkably, metalorganic frameworks (MOFs) are a class of novel synthetic material consisting of coordinated metal species and organic ligands, which have demonstrated a plethora of favorable properties for modulating the interfacial properties of Ti implants. This review comprehensively summarizes the recent progress in the development of MOF-coated Ti implants and highlights their potential utility for modulating the bio-implant interface to improve implant osseointegration, of which the discussions are outlined according to their physical traits, chemical composition, and drug delivery capacity. A perspective is also provided in this review regarding the current limitations and future opportunities of MOF-coated Ti implants for orthopedic applications. The insights in this review may facilitate the rational design of more advanced Ti implants with enhanced therapeutic performance and safety.

Theoretical modeling approach for adsorption of fibronectin on the nanotopographical implants.

The success of orthopedic implants depends on the sufficient integration between tissue and implant, which is influenced by the cellular responses to their microenvironment. The conformation of adsorbed extracellular matrix is crucial for cellular behavior instruction via manipulating the physiochemical features of materials. To investigate the electrostatic adsorption mechanism of fibronectin on nanotopographies, a theoretical model was established to determine surface charge density and Coulomb's force of nanotopography - fibronectin interactions using a Laplace equation satisfying the boundary conditions. Surface charge density distribution of nanotopographies with multiple random fibronectin was simulated based on random number and Monte Carlo hypothesis. The surface charge density on the nanotopographies was compared to the experimental measurements, to verify the effectiveness of the theoretical model. The model was implemented to calculate the Coulomb force generated by nanotopographies to compare the fibronectin adsorption. This model has revealed the multiple random quantitative fibronectin electrostatic adsorption to the nanotopographies, which is beneficial for orthopedic implant surface design.Significance: The conformation and distribution of adsorbed extracellular matrix on biomedical implants are crucial for directing cellular behaviors. However, the Ti nanotopography-ECM interaction mechanism remains largely unknown. This is mostly because of the interactions that are driven by electrostatic force, and any experimental probe could interfere with the electric field between the charged protein and Ti surface. A theoretical model is hereby proposed to simulate the adsorption between nanotopographies and fibronectin. Random number and Monte Carlo hypothesis were applied for multiple random fibronectin simulation, and the Coulomb's force between nanoconvex and nanoconcave structures was comparatively analyzed.

Laser microgrooving and resorbable blast texturing for enhanced surface function of titanium alloy for dental implant applications.

Long-term dental implant success is dependent on biocompatibility and osseointegration between the bone and the implant. Surface modifications such as laser-induced microgrooving which increase contact area can enhance osseointegration by establishing and directing a stable attachment between the implant surface and peri-implant bone. The objective of this study was to evaluate pre-osteoblast proliferation, morphology, and differentiation on titanium alloy (Ti64) surfaces-Laser-Lok© (LL), resorbable blast textured (RBT), and machined (M)-compared to tissue culture plastic (TCP) control. We hypothesized the LL surfaces would facilitate increased cellular alignment compared to all other groups, and LL and RBT surfaces would demonstrate enhanced proliferation and differentiation compared to M and TCP surfaces. Surface roughness was quantified using a surface profilometer, and water contact angle was measured to evaluate the hydrophilicity of the surfaces. Cellular function was assessed using quantitative viability and differentiation assays and image analyses, along with qualitative fluorescent (viability and cytoskeletal) imaging and scanning electron microscopy. No differences in surface roughness were observed between groups. Water contact angle indicated LL was the least hydrophilic surface, with RBT and M surfaces exhibiting greater hydrophilicity. Cell proliferation on day 2 was enhanced on both LL and RBT surfaces compared to M, and all three groups had higher cell numbers on day 2 compared to day 1. Cell orientation was driven by the geometry of the surface modification, as cells were more highly aligned on LL surfaces compared to TCP (on day 2) and RBT (on day 3). At day 21, cell proliferation was greater on LL, RBT, and TCP surfaces compared to M, though no differences in osteogenic differentiation were observed. Collectively, our results highlight the efficacy of laser microgrooved and resorbable blast textured surface modifications of Ti64 for enhancing cellular functions, which may facilitate improved osseointegration of dental implants.

Tooth-Implant-Supported Prosthetic Structures Versus Implant-Supported Restorations.

Objectives: The primary aim was to compare the amount of bone height change that occurs around the tooth and the implant when having tooth-implant-supported prosthetic restorations versus bone height change that appears around implants in only implant-supported prosthetic restorations. The secondary aim was to examine the influence of various factors such as the number of teeth involved in the construction, their endodontic treatment, number of implants, the type of implantology construction, the jaw in which the construction is located, the condition of the opposite jaw, gender, age, and working time, as well as to examine whether the initial bone level influenced the amount of change in bone height itself. Materials and methods: With a total of 50 respondents, 25 X-ray panoramic images were representing tooth-implant-supported prosthetic restorations, while the other 25 were representing implant-supported prosthetic restorations. Bone measures were taken (from enamel-cement junction/implant neck to the most apical bone point) from 2 panoramic radiographs. The first one is immediately after the implant placement and the second and the last one again in half a year up to seven years after, depending on the time when the photo was taken for each patient. The obtained difference represented the bone resorption, the bone formation, or a state without change. Influence of different factors, such as sex, age of the patient, working time, the number of teeth involved in the construction, endodontic treatment, number of implants, the type of implant construction, the jaw where the construction is located, the condition of the opposite jaw, as well as the initial bone condition, was examined. During the statistical analysis, frequency tables, basic statistical parameters, the Mann-Whitney U test, the Kruskal-Wallis Anova, Wilcoxon test, and regression analysis were used, and the results were presented in tabular form and the form of the Pareto diagram of t-values. Results: No statistically significant difference in bone change (whether we are talking about the place of the implant (-0.359±1.009 and median value 0.000), the place of a tooth (-0.428±0.746 and median value -0,150) in tooth-implant supported restorations, or the place of the implant in case of implant-supported structures (-0,059±0,200 and median value -0,120)) was proven. When talking about the influence of other factors, by regression analysis, the number of implants was shown to be the only factor with a statistically significant influence (ß=0.54; P=0.019) in a change of bone level, but only when talking about implant-supported restorations. Conclusion: No significant difference was proven between bone height change, neither around the tooth nor the implant in tooth-implant-supported prosthetic restorations compared to the bone height changes around the implant in only implant-supported prosthetic restorations. Among all the examined factors, the number of implants has shown to have statistically significant contribution to the amount of bone height change in implant-supported prosthetic restorations.

Evaluation of hydrophilic surface osseointegration in low-density bone: Preclinical study in rabbits

Abstract The aim of this study was to evaluate the osseointegration of a hydrophilic surface (blasting + acid etching + immersion in isotonic solution) in comparison with that of a control surface (blasting + acid etching) using an experimental model of low-density bone. To perform the study, 24 rabbits were submitted to the installation of 4 implants in the iliac bone bilaterally: 2 implants with a control surface and 2 implants with a hydrophilic surface. The rabbits were euthanized at 2, 4, and 8 weeks after implant installation. After euthanasia, one implant from each surface was used to perform the removal torque analysis, and the other implant was used for the execution of non-decalcified histological sections and evaluation of the bone implant contact (% BIC) as well as the fraction of bone tissue area between the implant threads (% BBT). The implants with a hydrophilic surface presented higher %BIC (42.92 ± 2.85% vs. 29.49 ± 10.27%) and % BBT (34.32 ± 8.52% vs. 23.20 ± 6.75%) (p < 0.05) in the 2-week period. Furthermore, the hydrophilic surface presented higher removal torque in the 8-week period (76.13 ± 16.00 Ncm2 vs. 52.77 ± 13.49 Ncm2) (p<0.05). Implants with a hydrophilic surface exhibited acceleration in the process of osseointegration, culminating in greater secondary stability in low-density bone than in implants with a control surface.

Resumo O objetivo deste estudo foi avaliar a osseointegração de uma superfície hidrofílica (jateamento + ataque ácido + imersão em solução isotônica) em comparação com uma superfície controle (jateamento + ataque ácido) usando um modelo experimental de osso de baixa densidade. Para realizar o estudo, 24 coelhos foram submetidos a instalação de 4 implantes bilateralmente no osso ilíaco: 2 implantes com superfície controle e 2 implantes com superfície hidrofílica. Os coelhos foram eutanasiados com 2, 4 e 8 semanas após a instalação dos implantes. Após a eutanásia, um implante de cada superfície foi usado para avaliar o torque de remoção, e o outro implante foi utilizado para execução de cortes histológicos não descalcificados e avaliação de contato osso implante (% BIC) bem como a fração da área tecido ósseo entre as roscas do implante (% BBT). Os implantes com superfície hidrofílica apresentaram maior %BIC (42.92 ± 2.85% vs. 29.49 ± 10.27%) e % BBT (34.32 ± 8.52% vs. 23.20 ± 6.75%) (p < 0.05) no período de 2 semanas. Além disso, a superfície hidrofílica apresentou maior torque de remoção no período de 8 semana (76.13 ± 16.00 Ncm2 vs. 52.77 ± 13.49 Ncm2) (p<0.05). Implantes com a superfície hidrofílica apresentaram aceleração no processo de osseointregração, culminando em melhor estabilidade secundária no osso de baixa densidade em relação a implantes com superfície controle.

Finite element analysis in implant dentistry: State of the art and future directions.

OBJECTIVE: To discuss the state of the art of Finite Element (FE) modeling in implant dentistry, to highlight the principal features and the current limitations, and giving recommendations to pave the way for future studies. METHODS: The articles' search was performed through PubMed, Web of Science, Scopus, Science Direct, and Google Scholar using specific keywords. The articles were selected based on the inclusion and exclusion criteria, after title, abstract and full-text evaluation. A total of 147 studies were included in this review. RESULTS: To date, the FE analysis of the bone-dental implant system has been investigated by analyzing several types of implants; modeling only a portion of bone considered as isotropic material, despite its anisotropic behavior; assuming in most cases complete osseointegration; considering compressive or oblique forces acting on the implant; neglecting muscle forces and the bone remodeling process. Finally, there is no standardized approach for FE modeling in the dentistry field. SIGNIFICANCE: FE modeling is an effective computational tool to investigate the long-term stability of implants. The ultimate aim is to transfer such technology into clinical practice to help dentists in the diagnostic and therapeutic phases. To do this, future research should deeply investigate the loading influence on the bone-implant complex at a microscale level. This is a key factor still not adequately studied. Thus, a multiscale model could be useful, allowing to account for this information through multiple length scales. It could help to obtain information about the relationship among implant design, distribution of bone stress, and bone growth. Finally, the adoption of a standardized approach will be necessary, in order to make FE modeling highly predictive of the implant's long-term stability.

Analysis of bone stress and primary stability of a dental implant using strain and torque measurements.

Introduction: The consensus among researchers is that early failure of dental implants is due to the lack of primary stability and compressive stress on the peri-implant bone that exceeds the physiological tolerance. Objective: The objective of this work is to propose a new methodology to quantify bone stress during dental implant insertion and to correlate it with primary stability. Materials and Methods: Titanium dental implants with a diameter of 3.75 mm were inserted in a 3.35 mm hole of a synthetic bone of polyurethane (PU) foam with a density of 20 PCF (0.32 g/cm3). During insertion, the insertion torque was measured with a digital torque meter and the bone strain was measured with strain gages located at 2, 4, 6, 8, and 10 mm from the coronal region. Results: The tests showed that the compressive strain is maximum in the third coronal region and decreases in the apical direction. The data also showed that there is a relationship between strain, insertion torque, and the primary stability of dental implants. Conclusion: The stress and strain on the bone progressively decreased from the coronal to the apical third. The maximum compressive stress (0.42 MPa) during insertion of the implant did not exceed bone strength. Insertion of 3.75 mm implants in type D2 bone with a 3.35 mm hole provides adequate primary stability without excessive compression of the bone. Clinical Significance: For the implant-bone combination used in the present study, the compressive stress generated during implant insertion did not exceed the physiological limit of cortical and medullary bone to the point of impairing osseointegration.

Debonding of coin-shaped osseointegrated implants: Coupling of experimental and numerical approaches.

While cementless implants are now widely used clinically, implant debonding still occur and is difficult to anticipate. Assessing the biomechanical strength of the bone-implant interface can help improving the understanding of osseointegration phenomena and thus preventing surgical failures. A dedicated and standardized implant model was considered. The samples were tested using a mode III cleavage device to assess the mechanical strength of the bone-implant interface by combining experimental and numerical approaches. Four rough (Sa = 24.5 µm) osseointegrated coin-shaped implants were left in sheep cortical bone during 15 weeks of healing time. Each sample was experimentally rotated at 0.03°/sec until complete rupture of the interface. The maximum values of the torque were comprised between 0.48 and 0.72 N m, while a significant increase of the normal force from 7-12 N to 31-43 N was observed during the bone-implant interface debonding, suggesting the generation of bone debris at the bone-implant interface. The experimental results were compared to an isogeometric finite element model describing the adhesion and debonding phenomena through a modified Coulomb's law, based on a varying friction coefficient to represent the transition from an unbroken to a broken bone-implant interface. A good agreement was found between numerical and experimental torques, with numerical friction coefficients decreasing from 8.93 to 1.23 during the bone-implant interface rupture, which constitutes a validation of this model to simulate the debonding of an osseointegrated bone-implant interface subjected to torsion.

Noninfectious tissue interactions at periprosthetic interfaces.

The success of hip arthroplasty is based on modern materials in addition to the continuous development of surgical techniques and clinical experience gained over six decades. The biocompatible implant materials used in hip arthroplasty can be textured or coated with biomimetic surfaces to ensure durable component ingrowth and moderate host response. Material integrity plays a critical role in the durability of the stable interface between implant components and periprosthetic tissues. Inflammation at the interfaces due to the release of degradation products from the implant materials is one of the causes of hip arthroplasty failure. This review summarizes the implant materials currently used in hip arthroplasty, their preclinical testing and the postoperative neogenesis of periprosthetic tissues, and the interactions of periprosthetic bone and the implant materials at the periprosthetic interfaces.

[Physiological reactions in the interface between cementless implants and bone]. / Physiologische Reaktionen im Interface zementfreier Implantate.

BACKGROUND: Surgical treatment of patients with osteoarthritis of the hip and persisting symptoms under conservative therapy has become increasingly important against the background of an aging population. OBJECTIVES: What are the physiological reactions in the interface between cementless implants and bone? METHODS: The literature is reviewed, expert opinions and animal models are analyzed and discussed. RESULTS: Surface coating of implants with hydroxyapatite or titanium can have positive effects on osteointegration. Additional local application of mediators might be beneficial for osteointegration in the future. CONCLUSION: Early peri-implant bone healing directly after implantation and late remodeling of the bone-implant interface are essential for secondary implant stability.

Impact of bone-implant gap size on the interfacial osseointegration: an in vivo study.

BACKGROUND: The bone-implant gap resulted from morphological mismatch between cervical bony endplates and implant footprint may have adverse impact on bone-implant interfacial osseointegration of cervical disc arthroplasty (CDA). The purpose of the study was to evaluate the impact of bone-implant gap size on the interfacial osseointegration in a rabbit animal model. METHODS: A series of round-plate implants with different teeth depth (0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm) was specifically designed. A total of 48 New Zealand white rabbits were randomly categorized into four groups by the implants they received (0.5 mm: group A, 1.0 mm: group B, 1.5 mm: group C, 2.0 mm: group D). At 4th and 12th week after surgery, animals were sacrificed. Micro-CT, acid fuchsin and methylene blue staining and hematoxylin and eosin (HE) staining were conducted. RESULTS: At 4th week and 12th week after surgery, both micro-CT and HE staining showed more new bone formation and larger bone coverage in group A and group B than that in group C and group D. At 12th week, the bone biometric parameters were significantly superior in group C when compared with group D (p < 0.05). At 12th week, hard tissue slicing demonstrated larger portion of direct contact of new bone to the HA coating in group A and group B. CONCLUSIONS: Bone-implant gap size larger than 1.0 mm negatively affected bone-implant osseointegration between compact bone and HA coated implant surface.

Modeling the debonding process of osseointegrated implants due to coupled adhesion and friction.

Cementless implants have become widely used for total hip replacement surgery. The long-term stability of these implants is achieved by bone growing around and into the rough surface of the implant, a process called osseointegration. However, debonding of the bone-implant interface can still occur due to aseptic implant loosening and insufficient osseointegration, which may have dramatic consequences. The aim of this work is to describe a new 3D finite element frictional contact formulation for the debonding of partially osseointegrated implants. The contact model is based on a modified Coulomb friction law by Immel et al. (2020), that takes into account the tangential debonding of the bone-implant interface. This model is extended in the direction normal to the bone-implant interface by considering a cohesive zone model, to account for adhesion phenomena in the normal direction and for adhesive friction of partially bonded interfaces. The model is applied to simulate the debonding of an acetabular cup implant. The influence of partial osseointegration and adhesive effects on the long-term stability of the implant is assessed. The influence of different patient- and implant-specific parameters such as the friction coefficient [Formula: see text], the trabecular Young's modulus [Formula: see text], and the interference fit [Formula: see text] is also analyzed, in order to determine the optimal stability for different configurations. Furthermore, this work provides guidelines for future experimental and computational studies that are necessary for further parameter calibration.

Do dental implants facilitate bone invasion in patients with oral squamous cell carcinoma? A case series.

Osseointegrated dental implants in the vicinity of oral squamous cell carcinoma (OSCC) will become more common given the increasing popularity of dental implants. Reports and studies of OSCC around dental implants are rare, as is the topic of how to handle OSCC surgically when implants are in contact with the tumour. In view of this uncertainty, a histological study was performed to assess tumour behaviour around implants. The aim was to determine whether an implant facilitates inward growth of the tumour and how this should be taken into account during staging and treatment planning. A total of 20 specimens were collected. The implants were macroscopically in contact with OSCC in 13 of the 20 specimens. Histologically, tumour tissue near the implant was indeed confirmed in nine of these cases. In seven cases, tumour invasion had led to resorption of the underlying jaw bone; tumour between the bone-implant interface was identified in only two of these cases, but without downward growth along the implant. In conclusion, no proof was found to confirm that the bone-implant interface is a preferred route for invasion. Therefore, dental implants in the vicinity of OSCC should not influence staging and treatment planning in this regard.

Effects of customized CAD/CAM abutments on cytokine levels in peri-implant crevicular fluid during early implant healing: a pilot study.

OBJECTIVES: This study aimed to assess levels of biomarkers associated with inflammation and tissue destruction in peri-implant crevicular fluid (PICF) of implants provided with customized or standard healing abutments during early implant healing. MATERIALS AND METHODS: Thirty implants were placed in 22 patients with partial posterior edentulism. Subsequently, test group implants (n=15) received one-piece titanium abutments that were fabricated using computer-aided design/computer-aided manufacturing (CAD/CAM). Control group implants (n=15) were provided with standard abutments. PICF collection and standardized periapical radiographs were carried out at suture removal one week later, following crown delivery after 3 months and at 6 months. Expression of C-reactive protein (CRP), interferon-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12A, IL-17A, macrophage inflammatory protein (MIP)-1α, matrix metalloproteinase (MMP)-13, osteopontin, osteoactivin, Receptor Activator of NF-κB (RANK), and TGF-ß were analyzed using a multiplex ELISA kit. RESULTS: Both groups showed a significant decrease in protein expression of CRP, IL-1ß, IL-6, IL-8, MIP-1α, osteopontin, osteoactivin, and TGF-ß, while MMP-13 levels increased during the observation period. A rise in OPG and RANK levels was detected among customized abutments. Expression of CRP was higher, whereas IL-1ß, IL-1α, and MIP-1α were decreased in control compared to test group implants after 6 months. Marginal bone loss did not depend on abutment modality. CONCLUSIONS: Both abutment types showed distinctive temporal expression of inflammatory biomarkers during 6 months following implant placement. TRIAL REGISTRATION: ISRCTN98477184, registration date 18/05/2022 CLINICAL RELEVANCE: Customized healing abutments exert similar effects on inflammation during early implant healing compared to standard healing abutments.