Comparison of three-dimensional digital analyses and two-dimensional histomorphometric analyses of the bone-implant interface

Histological analysis is considered to be the gold standard method of evaluating osseointegration around a bone-implant. However, this method requires invasive specimen preparation and is capable of representing only one plane. By comparison, micro-computed tomography (μCT) is a fast and convenient method that offers three-dimensional information but is hampered by problems related to resolution and artifacts, making it a supplementary method for osseointegration analysis. To verify the reliability of μCT for osseointegration evaluation, this animal model study compared bone-to-implant contact (BIC) ratios obtained by the gold standard histomorphometric method with those obtained by the μCT method, using a rabbit tibia implant model. A sandblasted, large-grit, acid-etched (SLA) implant and a machined surface implant were inserted into each tibia of two rabbits (giving eight implants in total). Bone-implant specimens were analyzed using μCT with a spiral scan technique (SkyScan 1275) and histological sections were prepared thereafter. Three-dimensional (3D) reconstructed μCT data and four two-dimensional (2D) μCT sections, including one section corresponding to the histologic section and three additional sections rotated 45°, 90°, and 135°, were used to calculate the BIC ratio. The Pearson's test was used for correlation analysis at a significance level of 0.05. The histomorphometric BIC and the 2D-μCT BIC showed strong correlation (r = 0.762, P = 0.046), whereas the histomorphometric BIC and 3D-μCT BIC did not (r = -0.375, P = 0.385). However, the mean BIC value of three or four 2D-μCT sections showed a strong correlation with the 3D-μCT BIC (three sections: r = 0.781, P = 0.038; four sections: r = 0.804, P = 0.029). The results of this animal model study indicate that μCT can be used to complement the histomorphometric method in bone-implant interface analyses. With the limitations of this study, 3D-μCT analysis may even have a superior aspect in that it eliminates random variables that arise as a consequence of the selected cutting direction.

Alloying design of biodegradable zinc as promising bone implants for load-bearing applications

Magnesium-based biodegradable metals (BMs) as bone implants have better mechanical properties than biodegradable polymers, yet their strength is roughly less than 350 MPa. In this work, binary Zn alloys with alloying elements Mg, Ca, Sr, Li, Mn, Fe, Cu, and Ag respectively, are screened systemically by in vitro and in vivo studies. Li exhibits the most effective strengthening role in Zn, followed by Mg. Alloying leads to accelerated degradation, but adequate mechanical integrity can be expected for Zn alloys when considering bone fracture healing. Adding elements Mg, Ca, Sr and Li into Zn can improve the cytocompatibility, osteogenesis, and osseointegration. Further optimization of the ternary Zn-Li alloy system results in Zn-0.8Li-0.4Mg alloy with the ultimate tensile strength 646.69 ± 12.79 MPa and Zn-0.8Li-0.8Mn alloy with elongation 103.27 ± 20%. In summary, biocompatible Zn-based BMs with strength close to pure Ti are promising candidates in orthopedics for load-bearing applications.

Effect of mussel adhesive protein coating on osteogenesis in vitro and osteointegration in vivo to alkali-treated titanium with nanonetwork structures

Purpose: On the basis of reasonable superposition of various surface treatment methods, alkali-treated titanium with nanonetwork structures (TNS) was coated with mussel adhesive protein (MAP) and named TNS-MAP. The aims were to optimize the biological properties of TNS, endue it with new properties, and enhance its utility in clinical dental applications. Methods: TNS disks were coated with MAP and the product surface was characterized. Its osteogenic properties were determined by evaluating its effects on cell adhesion, cell proliferation, the expression of osteogenesis-related genes, and in vivo experiments. Results: The treated materials showed excellent hydrophilicity, good surface roughness, and advantages of both TNS and MAP. TNS-MAP significantly promoted initial cell attachment especially after 15 mins and 30 mins. At every time point, cell adhesion and proliferation, the detection rate of osteogenesis-related markers in the extracellular matrix, and the expression of osteogenesis-related genes were markedly superior on TNS-MAP than the control. The in vivo experiments revealed that TNS-MAP promoted new bone growth around the implants and the bone-implant interface. Conclusion: We verified through in vitro and in vivo experiments that we successfully created an effective TNS-MAP composite implant with excellent biocompatibility and advantages of both its TNS and MAP parent materials. Therefore, the new biocomposite implant material TNS-MAP may potentially serve in practical dentistry and orthopedics.

Cone beam analysis of the buccal bone associated with a dental implant: A tridimensional assessment case report

OBJECTIVE

This case report presents cone beam computed tomography (CBCT) three-dimensional (3D) assessment of the buccal bone associated with an implant.

METHOD AND MATERIALS

A patient who had immediate implant replacement of a maxillary incisor received a CBCT examination after 6 months. The scanned volume was then subjected to segmentation of the buccal bone associated with the implant and to its three-dimensional rendering.

RESULTS

Virtual reconstruction allowed volumetric assessment of the buccal plate, and of the buccal marginal bone level.

CONCLUSION

Creating a 3D virtual volume permits a comprehensive evaluation of the anatomical information contained in the CBCT dataset.

Bone quality, and the combination and penetration of cement-bone interface: A comparative micro-CT study of osteoarthritis and rheumatoid arthritis

To compare the microstructure, bone quality, and the combination and penetration of cement-bone interface in tissue specimens from patients with osteoarthritis (OA) and rheumatoid arthritis (RA).A total of 80 femoral condyle tissue specimens from 20 OA patients (40 condyles) and 20 RA patients (40 condyles) who underwent total knee arthroplasty at the Department of Orthopaedics in Tengzhou Central People's Hospital were collected between January 2017 and September 2017. According to the random number table method, 20 specimens from the OA group were defined as group A, and 20 specimens in the RA group were defined as group B. The bone quality parameters were measured by micro-CT. The remaining 20 specimens in the OA group and the remaining 20 specimens in the RA group were defined as group C and group D, the cement-bone interfaces were established by the self-made bone cement compression device, and were analyzed by micro-CT.Micro-CT measurement revealed that the bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) in group A were significantly higher than those in group B (all P < .05). The bone surface/bone volume (BS/BV), structure model index (SMI), trabecular separation (Tb.Sp), and degree of anisotropy (DA) in group A were significantly lower than those in group B (all P < .05). The penetration depth of bone cement in group D was significantly greater than those in group C via x-ray detection.The bone quality of OA patients is better than that of RA patients, but the combination and penetration of cement-bone interface of RA patients are better than that of OA patients. The findings advance our understanding of knee prosthesis and have important clinical implications, but they require validations in future studies with larger sample sizes.

Four Stable and Functioning Dental Implants Retrieved for Fracture After 14 and 17 Years from the Same Patient: A Histologic and Histomorphometric Report

The aim of the present study was a histologic and histomorphometric analysis of the peri-implant tissue reactions and of the bone-titanium interface in successfully osseointegrated, clinically stable, and immobile retrieved titanium dental implants after a long loading period. Four successfully osseointegrated and stable implants with a sandblasted surface were retrieved from a patient due to fracture, two after 14 years of loading and two after 17 years. None of these implants has been previously reported. Mature, compact bone with a few marrow spaces was observed around all four implants. At low magnification, a high percentage of bone-implant contact (BIC) was present at the interface of almost all implants. BIC percentage for the four implants was 83%, 66%, 74%, and 65%. In almost all the implants, the space within the threads was almost completely filled by compact bone. Close, tight contact between bone and implant surface was observed in all specimens, and no gaps or fibrous connective tissue was found at the bone-implant interface. All implants appeared to be well integrated in the surrounding mineralized bone, and all showed adequate BIC percentages after a long loading history.

Neutron tomographic imaging of bone-implant interface: Comparison with X-ray tomography

Metal implants, in e.g. joint replacements, are generally considered to be a success. As mechanical stability is important for the longevity of a prosthesis, the biological reaction of the bone to the mechanical loading conditions after implantation and during remodelling determines its fate. The bone reaction at the implant interface can be studied using high-resolution imaging. However, commonly used X-ray imaging suffers from image artefacts in the close proximity of metal implants, which limit the possibility to closely examine the bone at the bone-implant interface. An alternative ex vivo 3D imaging method is offered by neutron tomography. Neutrons interact with matter differently than X-rays; therefore, this study explores if neutron tomography may be used to enrich studies on bone-implant interfaces. A stainless steel screw was implanted in a rat tibia and left to integrate for 6weeks. After extracting the tibia, the bone-screw construct was imaged using X-ray and neutron tomography at different resolutions. Artefacts were visible in all X-ray images in the close proximity of the implant, which limited the ability to accurately quantify the bone around the implant. In contrast, neutron images were free of metal artefacts, enabling full analysis of the bone-implant interface. Trabecular structural bone parameters were quantified in the metaphyseal bone away from the implant using all imaging modalities. The structural bone parameters were similar for all images except for the lowest resolution neutron images. This study presents the first proof-of-concept that neutron tomographic imaging can be used for ex-vivo evaluation of bone microstructure and that it constitutes a viable, new tool to study the bone-implant interface tissue remodelling.

Is cone beam computed tomography accurate for postoperative evaluation of implants? An in vitro study

OBJECTIVE

The aim of this study was to evaluate the accuracy of cone beam computed tomography (CBCT) for evaluation of the bone-implant interface in comparison with periapical radiography.

STUDY DESIGN

Titanium implants were inserted in 74 bovine rib blocks in intimate contact with bone walls and with a gap of 0.125 mm (simulating failure in the osseointegration process). Periapical radiographs were taken with conventional film, and CBCT scans were acquired with i-CAT (0.2 mm and 0.125 mm voxel) and Kodak (0.2 mm and 0.076 mm voxel) units. Three examiners evaluated the images using a 5-point scale. Diagnostic accuracy was analyzed through sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve (AUC) with 95% confidence intervals (CIs). Intra- and interexaminer agreements were analyzed through Kendall's concordance test.

RESULTS

Intra- and interexaminer agreements showed satisfactory results. The greatest accuracy was observed with conventional radiography (AUC = 0.963; CI 95% = 0.891-0.993). I-CAT 0.125-mm images showed good accuracy (AUC = 0.885; CI 95% = 0.790-0.947), with no significant difference compared with conventional radiography. Kodak images had high specificity and low sensitivity, presenting more false-negative results.

CONCLUSIONS

Conventional radiography showed the highest accuracy for assessment of the bone-implant interface. However, CBCT (i-CAT; 0.125-mm voxel), if available or if performed for preoperative assessment of another implant site, may provide similar accuracy.

Comparison of contact radiographed and stained histological sections for osseointegration analysis of dental implants: an in vivo study

OBJECTIVES

Histology is still regarded as the gold-standard to determine bone implant contact (BIC) as a parameter representing implant stability. As the further processing of cut slices for contact radiography (CR) to stained and polished histological sections is time consuming and error prone, our aim was to assess agreement between CR and Giemsa-eosin (GE) stained sections with regard to dental implants.

STUDY DESIGN

Threaded dental titanium implants (n = 54) from the maxillae of Goettingen minipigs were evaluated. After 28 and 56 days, BIC and the ratio of bone volume to total volume (BV/TV; 1000 μm) were determined on the same sections by using CR and GE staining, and the results were compared.

RESULTS

Moderate differences for BIC (0.6%; P = .53) and BV/TV (1.3%; P = .01) between the methods were determined, in which CR overestimated BIC and BV/TV. A strong correlation was seen between the modalities concerning BIC (28 days: r = 0.84; 56 days: r = 0.85; total: r = 0.85) and BV/TV (r = 0.96; r = 0.94; r = 0.96; all: P < .0001).

CONCLUSIONS

CR enabled determination of the bone-to-implant interface in comparison with GE-stained sections. BIC and BV/TV were slightly overestimated but correlated strongly between the methods. Therefore, if BIC and BV/TV are sufficient endpoints, CR is adequate and no further preparation and staining are necessary.

Time course of peri-implant bone regeneration around loaded and unloaded implants in a rat model

The time-course of cancellous bone regeneration surrounding mechanically loaded implants affects implant fixation, and is relevant to determining optimal rehabilitation protocols following orthopaedic surgeries. We investigated the influence of controlled mechanical loading of titanium-coated polyether-ether ketone (PEEK) implants on osseointegration using time-lapsed, non-invasive, in vivo micro-computed tomography (micro-CT) scans. Implants were inserted into proximal tibial metaphyses of both limbs of eight female Sprague-Dawley rats. External cyclic loading (60 or 100 μm displacement, 1 Hz, 60 s) was applied every other day for 14 days to one implant in each rat, while implants in contralateral limbs served as the unloaded controls. Hind limbs were imaged with high-resolution micro-CT (12.5 μm voxel size) at 2, 5, 9, and 12 days post-surgery. Trabecular changes over time were detected by 3D image registration allowing for measurements of bone-formation rate (BFR) and bone-resorption rate (BRR). At day 9, mean %BV/TV for loaded and unloaded limbs were 35.5 ± 10.0% and 37.2 ± 10.0%, respectively, and demonstrated significant increases in bone volume compared to day 2. BRR increased significantly after day 9. No significant differences between bone volumes, BFR, and BRR were detected due to implant loading. Although not reaching significance (p = 0.16), an average 119% increase in pull-out strength was measured in the loaded implants. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:997-1006, 2017.

A Two-Year Evaluation of a Sloped Marginal Contour Implant System Placed in Healed Sites

PURPOSE

The purpose of this clinical trial was to evaluate the survival rate, bone remodeling, and soft tissue health around sloped marginal contour implants when placed in healed sites posteriorly in the mouth.

MATERIALS AND METHODS

Implants were placed in healed sites at premolar and molar regions. After a 3-month osseointegration period, definitive prostheses were connected. Clinical and radiographic examinations were performed at implant placement and then 1, 3, 6, 12, and 24 months after implant placement. An assessment of implant stability, peri-implant mucosa, level of attached gingivae, occlusion, proximal contact, and marginal bone levels was performed at each respective visit.

RESULTS

Fourteen patients were treated and restored with 18 single crowns. The cumulative survival rate was 100% after 2 years. The mean marginal bone remodeling was 0.04 ± 0.26 mm (n = 18). The attached gingival change was +0.33 ± 0.35 mm.

CONCLUSION

The 24-month results indicate that the sloped marginal contour implant performed well in posterior healed sites with a 100% survival rate and good marginal bone maintenance.

Microbiologic and Clinical Findings of Implants in Healthy Condition and with Peri-Implantitis

PURPOSE

To compare implants in healthy conditions and implants with peri-implantitis with regard to their clinical parameters and the microbiologic composition at the peri-implant sulcus, inside the implant connection, and the gingival sulcus of neighboring teeth.

MATERIALS AND METHODS

A cross-sectional study was performed including consecutive patients with implants in healthy conditions and with peri-implantitis. Clinical parameters for which patients were screened included bleeding on probing, pocket depth, and plaque index at six sites. Samples for microbiologic analysis were obtained from three locations: the peri-implant sulcus, inside the implant connection, and the gingival sulcus of neighboring teeth. Quantitative real-time polymerase chain reaction (PCR) was carried out for total counts of 10 microorganisms: Aggregatibacter actinomycetemcomitans, Porphyromona gingivalis, Tanerella forsythia, Tanerella denticola, Prevotela intermedia, Peptostreptococcus micros, Fusobacterium nucleatum, Campylobacter rectus, Eikenella corrodens, and Candida albicans. The response variables were the percentage of positive sites and total bacterial counts.

RESULTS

One hundred twenty-two implants in 57 patients were analyzed in the healthy group and 113 implants in 53 patients in the peri-implantitis group. Differences between the groups were statistically significant for bruxism, probing pocket depth, bleeding on probing, and radiographic bone level. Orange complex species (P intermedia, P micros, F nucleatum) were the most prevalent in the three types of sites for both groups, and prevalence values were higher in the peri-implantitis group. Differences in prevalence between groups were more marked inside the connection than in the peri-implant sulcus. Absolute loads of most microbes and total bacterial counts were higher for the peri-implantitis group in the three locations. Again, differences were bigger inside the connection than at the peri-implant sulcus. Significant interactions were found for prevalence and absolute microbial loads between groups and locations, and for the interaction of group × location.

CONCLUSION

Clinical and microbiologic differences were observed between healthy subjects and those with peri-implantitis. Microbiologic differences between groups were more marked inside the connection than in the peri-implant sulcus. The potential role of the implant connection as a microbial reservoir for peri-implant diseases and in the outcome of their treatment should be confirmed with further studies.

Implant-delivered Alendronate Causes a Dose-dependent Response on Net Bone Formation Around Porous Titanium Implants in Canines

BACKGROUND

Bony fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving porous implant fixation could improve the reliability and durability of these reconstructive procedures.

QUESTIONS/PURPOSES

In this study, we asked whether there is a positive and dose-dependent effect of the local release of the bisphosphonate alendronate from (1) alendronate/hydroxyapatite (HA) porous-coated titanium implants compared with bare metal porous controls; and (2) alendronate/HA on porous-coated titanium implants compared with HA-coated porous controls with respect to extent of bone ingrowth, bone apposition, and periimplant bone formation in a canine model?

METHODS

Three-dimensional printed porous-coated cylindrical implants coated with three different doses (0.02, 0.06, and 0.18 mg/cm(2)) of alendronate were inserted bilaterally in the intramedullary canal of the proximal femora of 15 adult mongrel dogs (age range, 3-9 years; mean, 5 years) weighing between 36 kg and 60 kg (mean, 43 kg). In each dog, an implant coated with HA and one of three different doses of alendronate was inserted on one side while the contralateral femur had a bare metal porous control implant and an identical control implant with a coating of HA. The dose effect of locally released alendronate on the extent of bone ingrowth, bone apposition, and periimplant bone was assessed by backscattered electron microscopy of three pairs of cross-sections taken from each implant at 12 weeks after surgery. A linear mixed model was used to perform the statistical analyses to account for the correlation in the data resulting from the multiple measures performed on each dog.

RESULTS

Compared with paired bare metal controls, periimplant bone increased by 92% (p = 0.007), and 114% (p < 0.001) in the femora with the alendronate implants with a dose of 0.06 mg/cm(2), or 0.18 mg/cm(2), respectively. At a dose of 0.02 mg/cm(2), there was no difference (46% change; p = 0.184, with the numbers available). The comparison of the alendronate-dosed implants with their HA-coated controls showed that the intermediate dose of 0.06 mg/cm(2) alendronate had the greatest effect on net bone formation. Bone apposition was enhanced with the 0.06-mg/cm(2) alendronate femoral implants (82%; p = 0.008), although there was no change in bone ingrowth (37% change; p = 0.902, with the numbers available). When compared with the HA-coated control implants, the greatest effect of the alendronate-dosed implants was the increased amount of periimplant bone at the intermediate dose of 0.06-mg/cm(2) (108%, p = 0.009). There was no effect of the low (0.02-mg/cm(2)) and high (0.18-mg/cm(2)) alendronate-dosed implants (4%, and 6%, respectively; p = 0.321, p = 0.502). Overall, all three alendronate-dosed implants revealed little to no effect on bone ingrowth compared with the HA-coated control implants.

CONCLUSIONS

The local release of alendronate from a three-dimensional printed porous-coated implant from the three doses studied showed an overall improvement in bone apposition and periimplant bone at the intermediate dose compared with bare metal or with HA-coated controls, although the effect was more pronounced compared with bare metal. Long-term studies to show the effects of localized alendronate delivery and mechanical fixation would be the next step for future studies.

CLINICAL RELEVANCE

Local release of alendronate from a three-dimensional printed porous-coated implant may improve the reliability of cementless fixation of currently available porous-coated bare metal implants.

The Effects of Subcrestal Implant Placement on Crestal Bone Levels and Bone-to-Abutment Contact: A Microcomputed Tomographic and Histologic Study in Dogs

PURPOSE

Implant design and the implant-abutment interface have been regarded as key influences on crestal bone maintenance over time. The aim of the present study was to determine crestal bone changes around implants placed at different depths in a dog model.

MATERIALS AND METHODS

Thirty-six two-piece dental implants with a medialized implant-abutment interface and Morse taper connection (Ankylos, Dentsply) were placed in edentulous areas bilaterally in six mongrel dogs. On each side of the mandible, three implants were placed randomly at the bone crest, 1.5 mm subcrestally, or 3.0 mm subcrestally. After 3 months, the final abutments were torqued into place. At 6 months, the animals were sacrificed and samples taken for microcomputed tomographic (micro-CT) and histologic evaluations.

RESULTS

Micro-CT analysis revealed similar crestal or marginal bone loss among groups. Both subcrestal implant groups lost significantly less crestal and marginal bone than the equicrestal implants. Bone loss was greatest on the buccal of the implants, regardless of implant placement depth. Histologically, implants placed subcrestally were found to have bone in contact with the final abutment and on the implant platform.

CONCLUSION

Implants with a centralized implant-abutment interface and Morse taper connection can be placed subcrestally without significant loss of crestal or marginal bone. Subcrestal placement of this implant system appears to be advantageous in maintaining bone height coronal to the implant platform.