Guided bone regeneration around titanium plasma-sprayed, acid-etched, and hydroxyapatite-coated implants in the canine model

Hydroxyapatite nano-pillars on TI-6Al-4V: Enhancements in cell spreading and proliferation during cell/surface integration

Despite the attractive combinations of cell/surface interactions, biocompatibility, and good mechanical properties of Ti-6Al-4V, there is still a need to enhance the early stages of cell/surface integration that are associated with the implantation of biomedical devices into the human body. This paper presents a novel, easy and reproducible method of nanoscale and nanostructured hydroxyapatite (HA) coatings on Ti-6Al-4V. The resulting nanoscale coatings/nanostructures are characterized using a combination of Raman spectroscopy, scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanostructured/nanoscale coatings are shown to enhance the early stages of cell spreading and integration of bone cells (hFOB cells) on Ti-6Al-4V surfaces. The improvements include the acceleration of extra-cellular matrix, cell spreading and proliferation by nanoscale HA structures on the coated surfaces. The implications of the results are discussed for the development of HA nanostructures for the improved osseointegration of Ti-6Al-4V in orthopedic and dental applications.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

Current Concepts of Surface Topography of Implants: A Review

Both the rate of osseointegration and its extent depend upon the characteristics of the implant surface.1 2 3 4 5 Depending on the surface of the implant determination of implant–bone contact area, the rate of bone formation around the implant can be done.6 Hence, the implant surface plays an important part in multiple ways in the osseointegration process.

In Vitro and In Vivo Biocompatibility Studies of a Cast and Coated Titanium Alloy

The biocompatibility of a cast porous and with a calcium titanate reaction layer functionalized titanium alloy (Ti-6Al-7Nb) was tested by means of cell culture, and a small (rat) and large animal (sheep) model. The uncoated titanium material served as a control. In-vitro tests included the validation of osteoblast-like cells attached to the surface of the material with scanning electron microscopy and immunofluorescence of cytoskeletal actin as well as their osteogenic development, the ability to mineralize, and their vitality. Following the in-vitro tests a small animal (rat) and big animal (sheep) model were accomplished by inserting a cylindrical titanium implant into a drill hole defect in the femoral condyle. After 7, 14, and 30 days (rat) and 6 months (sheep) the condyles were studied regarding histological and histomorphometrical characteristics. Uncoated and coated material showed a good biocompatibility both in cell culture and animal models. While the defect area in the rat is well consolidated after 30 days, the sheep show only little bone inside the implant after 6 months, possibly due to stress shielding. None of the executed methods indicated a statistically significant difference between coated and uncoated material.

Osteogenesis-Related Gene Expression and Guided Bone Regeneration of a Strontium-Doped Calcium-Phosphate-Coated Titanium Mesh

Guided bone regeneration using a perforated titanium membrane is actively used in oral and orthopedic surgeries to provide space for the subsequent filling of a new bone in the case of bone defects and to achieve proper bone augmentation and reconstruction. The surface modification of a titanium membrane using a strontium-substituted calcium phosphate coating has become a popular trend to provide better bioactivity and biocompatibility on the membrane for improving the bone regeneration because strontium can stimulate not only the differentiation of osteoblasts but also inhibit the differentiation of osteoclasts. The strontium-doped calcium phosphate coating on the titanium mesh was formed by the cyclic precalcification method, and its effects on bone regeneration were evaluated by in vitro analysis of osteogenesis-related gene expression and in vivo evaluation of osteogenesis of the titanium mesh using the rat calvarial defect model in this study. It was identified that the strontium-doped calcium phosphate-treated mesh showed a higher expression of all genes related to osteogenesis in the osteoblast cells and resulted in new bone formation with better osseointegration with the mesh in the rat calvarial defect, in comparison with the results of untreated and calcium phosphate-treated meshes.

Chemical and Structural Characterization of Sandlasted Surface of Dental Implant using ZrO2 Particle with Different Shape

The clinical success of dental implantation is associated with the phenomenon of osteointegration. Geometry and topography of the implant surface are critical for the short- and long-term success of an implantation. Modification of the surface of endosseous part of the implant with sandblasting was of special interest for our study. Taking into account the advantages of currently used ceramic abrasives: aluminum oxide, titanium oxide, calcium phosphate, these materials are able to break down during collision with the treated surface, the possibility of incorporation of their residues into the implant surface, as well as the difficulty of removing these residues. This paper aimed to determine the preferred composition and the shape of the abrasive, as well as the treatment regime for ZrO2 sandblasting modification of the surface of the endosseous part of the dental implant. Tetragonal and cubic solid solutions are based on ZrO2, as an abrasive that is applied for zirconium-niobium alloy sandblasting under different pressures. Optical and scanning electron microscopy, the physical and chemical state of the surface of implants as well as contact angle measurement and cell viability were used to assess surface after sandblasting. The results demonstrate the potential of using granular powders that are based on zirconium dioxide as an abrasive to create a rough surface on endosseous part of dental implants made from zirconium-based alloys. It does not lead to a significant change in the chemical composition of the surface layer of the alloy and it does not require subsequent etching in order to remove the abrasive particles. Based on structural and chemical characterization, as well as on cell viability and contact angle measurement, sandblasting by tetragonal ZrO2 powder in 4 atm. and an exposure time of 5 s provided the best surface for dental implant application.

Composition and Modifications of Dental Implant Surfaces

Since Brånemark discovered the favorable effects of titanium in bone healing in 1965, titanium has emerged as the gold standard bulk material for present-time dental implantology. In the course of years researchers aimed for improvement of the implants performance in bone even at compromised implant sites and multiple factors were investigated influencing osseointegration. This review summarizes and clarifies the four factors that are currently recognized being relevant to influence the tissue-implant contact ratio: bulk materials and coatings, topography, surface energy, and biofunctionalization. The macrodesigns of bulk materials (e.g., titanium, zirconium, stainless steel, tantalum, and magnesium) provide the mechanical stability and their influence on bone cells can be additionally improved by surface treatment with various materials (calcium phosphates, strontium, bioglasses, diamond-like carbon, and diamond). Surface topography can be modified via different techniques to increase the bone-implant contact, for example, plasma-spraying, grit-blasting, acid-etching, and microarc oxidation. Surface energy (e.g., wettability and polarity) showed a strong effect on cell behavior and cell adhesion. Functionalization with bioactive molecules (via physisorption, covalent binding, or carrier systems) targets enhanced osseointegration. Despite the satisfying clinical results of presently used dental implant materials, further research on innovative implant surfaces is inevitable to pursuit perfection in soft and hard tissue performance.

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

Maxillary sinus floor augmentation using a nano-crystalline hydroxyapatite silica gel: case series and 3-month preliminary histological results

The aim of this case series is to histologically examine a new hydroxyapatite in sinus lift procedure after 3 months. Ten 2-stage sinus lifts were performed in 10 healthy patients having initial bone height of 1-2mm and bone width of 5mm, asking for a fixed implant-supported rehabilitation. After graft material augmentation, a rough-surfaced mini-implant was inserted to maintain stability of the sinus widow. A bioptical core containing a mini-implant was retrieved 3 months after maxillary sinus augmentation with NanoBone(®) and processed for undecalcified histology. From the histomorphometric analysis, NanoBone(®) residuals accounted for the 38.26% ± 8.07% of the bioptical volume, marrow spaces for the 29.23% ± 5.18% and bone for the 32.51% ± 4.96% (new bone: 20.64% ± 2.96%, native bone: 11.87% ± 3.27%). Well-mineralized regenerated bone with lamellar parallel-fibred structure and Haversian systems surrounded the residual NanoBone(®) particles. The measured bone-to-implant contact amounted to 26.02% ± 5.46%. No connective tissue was observed at the implant boundary surface. In conclusion, the tested material showed good histological outcomes also 3 months after surgery. In such critical conditions, the use of a rough-surfaced mini-implant showed BIC values supposed to be effective also in case of functional loading. Although longer follow-up and a wider patient size are needed, these preliminary results encourage further research on this biomaterial for implant load also under early stage and critical conditions.

Periosteum-derived cells as an alternative to bone marrow cells for bone tissue engineering around dental implants. A histomorphometric study in beagle dogs

BACKGROUND

The aim of this study is to investigate the potential use of periosteum-derived cells (PCs) for tissue engineering in peri-implant defects.

METHODS

Bone marrow cells (BMCs) and PCs were harvested from seven adult beagle dogs, cultured in vitro, and phenotypically characterized with regard to their osteogenic properties. The animals were then subjected to teeth extraction, and 3 months later, two implant sites were drilled, bone dehiscences created, and dental implants placed. Dehiscences were randomly assigned to one of two groups: PCs (PCs + carrier) and BMCs (BMCs + carrier). After 3 months, the animals were sacrificed and the implants with adjacent hard tissues were processed for undecalcified sections. Bone-to-implant contact, bone fill within the limits of implant threads, and new bone area in a zone lateral to the implant were histometrically obtained.

RESULTS

In vitro, phenotypic characterization demonstrated that both cell populations presented osteogenic potential, as identified by the mineral nodule formation and the expression of bone markers. Histometrically, an intergroup analysis showed that both cell-treated defects had similar bone fill within the limits of implant threads and bone-to-implant contact (P >0.05), and although a trend toward higher new bone area values was found for the PC group, there was no significant difference between the experimental groups (P >0.05).

CONCLUSIONS

Periosteal and bone marrow cells presented a similar potential for bone reconstruction. As such, periosteum may be considered as an alternative source of osteogenic cells in implant dentistry.

Transmucosal healing around peri-implant defects: crestal and subcrestal implant placement in dogs

OBJECTIVE

This study was designed to evaluate the transmucosal healing response of implants placed with the junction of the smooth surfaces, either crestal or subcrestal, into simulated extraction defects after healing periods of 1 and 3 months.

MATERIALS AND METHODS

A total of 23 Straumann SP v3.3 mm NN, SLA 10 mm implants were placed in the mandibular premolar regions of three greyhound dogs 3 months after the teeth were removed. Five control implants were placed at the crestal bone level, and test implants with surgically created peri-implant defects of 1.25 mm wide x 5 mm depth were placed either at the crestal (nine implants) or at the 2 mm subcrestal (nine implants) bone level. Implants on the right side were placed 1 month before the dogs were sacrificed, and implants on the left side were placed 3 months before sacrifice. All dogs had daily plaque control following surgery and were sacrificed 3 months after implant placement for histological and histometric analyses.

RESULTS

Mesial-distal ground sections of the control and test implant specimens showed a greater %BIC in the coronal defect region after 3 months of healing. This healing response was incomplete for the test implants compared with the control implants after a 1-month healing period. The histometric measurements for test implants placed at the crestal bone level or 2 mm subcrestal with surgically created peri-implant defects were more coronal or closer to the implant margin compared with the control implants. Additionally, the degree of osseointegration between the newly formed bone and the implant surface was similar between the test implants.

CONCLUSION

Peri-implant defects of 1.25 mm width healed with spontaneous bone regeneration around implants placed transmucosally at crestal or 2 mm subcrestal with a high degree of osseointegration after a 3-month healing period.

In vivo bone response and mechanical evaluation of electrosprayed CaP nanoparticle coatings using the iliac crest of goats as an implantation model

Recent trends in clinical implantology include the use of endosseous dental implant surfaces embellished with nano-sized modifications. The current study was initiated to evaluate the mechanical properties, as well as the potential beneficial effects, of electrosprayed CaP nanoparticle-coated (nano-CaP) implants on the in vivo osteogenic response, compared with grit-blasted, acid-etched (GAE) implant surfaces as controls. For this purpose nano-CaP coatings were deposited on cylindrical screw-type (St) implants and implanted bilaterally into the iliac crest of goats for 6weeks. In addition to histological and histomorphometrical analyses, insertion torque and removal torque values were measured on implant placement and retrieval, respectively. The present study showed similar insertion and removal torque values for nano-CaP-coated and GAE control implants, with no statistically significant increase in torque value during the implant period for either group. With regard to bone-implant contact and peri-implant bone volume, no significant differences were found between nano-CaP-coated and GAE implants after 6weeks implantation. In conclusion, this study has demonstrated that in situations in which implants are placed in a non-compromised situation using a standard press fit implantation strategy the performance of electrosprayed nano-CaP coatings is comparable with GAE implants, both with respect to implant fixation and bone healing response.

An oxidized implant surface may improve bone-to-implant contact in pristine bone and bone defects treated with guided bone regeneration: an experimental study in dogs

BACKGROUND

The aim of the present study was to histometrically evaluate bone healing in the absence of bone defects and in the presence of surgically created bone defects treated by guided bone regeneration at oxidized and turned implant surfaces.

METHODS

Three months after dental extractions, standardized buccal dehiscence defects (height: 5 mm; width: 4 mm) were surgically created following implant site preparation in the mandible of 10 dogs. Oxidized-surface implants (OSI) and turned-surface implants (TSI) were inserted bilaterally, and the bone defects were treated by guided bone regeneration. After 3 months of healing, the animals were sacrificed, blocks were dissected, and undecalcified sections were obtained and processed for histometric analysis. The percentage of bone-to-implant contact (BIC) and bone density (BD) was evaluated inside the threads on the buccal (regenerated bone) and lingual sides (pristine bone) of the implants. Data were evaluated using two-way analysis of variance (P <0.05).

RESULTS

New bone formation could be observed in OSI and TSI in the region of the defect creation. The BIC values observed in OSI for pristine and regenerated bone were 57.03% +/- 21.86% and 40.86% +/- 22.73%, respectively. TSI showed lower values of BIC in pristine bone (37.39% +/- 23.33%) and regenerated bone (3.52% +/- 4.87%). The differences between OSI and TSI were statistically significant. BD evaluation showed no statistically significant differences between OSI and TSI in pristine and regenerated bone.

CONCLUSION

The oxidized implant surface promoted a higher level of BIC than the turned implant surface at pristine and regenerated bone.

Improvement of osseointegration of titanium dental implant surfaces modified with CO ions: a comparative histomorphometric study in beagle dogs

The aim of this study was to compare carbon-oxygen (CO) ion implantation as a surface treatment with diamond-like carbon and commercially treated implants, including double acid-etched (Osseotite), oxidized (TiUnite) and sandblasted and acid-etched (SLA), using machine-turned titanium implants as control. A total of 72 dental implants divided into 6 groups were placed in the mandibles of 12 beagle dogs. Evaluation was performed by conventional light transmission microscopy and environmental scanning electron microscopy (ESEM). The histological results obtained via ESEM demonstrated bone-implant contact percentage (%BIC) for implants treated with CO ion implantation of 61% and 62% at 3 and 6 months, respectively. At the same time points, the values were 48% and 45% for double acid-etched, 46% and 52% for sandblasted and acid-etched, 55% and 46% for oxidized, and 33% and 49% for machine-turned titanium control implants. Values of %BIC were statistically significantly higher in implants treated with CO ion implantation compared to the commercially treated implant group (p=0.002 and p=0.025) and the control implants (p=0.001 and p=0.032) at 3 and 6 months, respectively. No significant differences were observed between the three groups of commercially treated implants. The larger %BIC of the ion-implanted group was observable at an early stage.

Platelet-rich plasma may not provide any additional effect when associated with guided bone regeneration around dental implants in dogs

OBJECTIVE

The aim of this study was to evaluate histometrically bone healing in surgically created dehiscence-type defects around titanium implants treated with an association of platelet-rich plasma (PRP) and guided bone regeneration (GBR).

MATERIALS AND METHODS

Ten male adult mongrel dogs were used, from which the three low premolars (P2, P3, P4) and the first molar were extracted. Three months after teeth extraction, two implant sites were bilaterally drilled, buccal bone dehiscences were created and four titanium implants were placed. Dehiscences were randomly assigned to the following groups: (1) PRP, (2) GBR, (3) PRP+GBR and (4) control. After 3 months, the animals were sacrificed and the implants and adjacent hard tissues were processed for undecalcified sections. Bone-to-implant contact (BIC), bone density within the limits of implant threads (BW), bone density (BD) and new bone area (BA) in a zone lateral to the implant corresponding to bone defects were obtained and measured.

RESULTS

Intergroup analysis (two-way ANOVA -alpha=5%) demonstrated that when PRP was utilized,no differences were observed for all parameters (P>0.05). However, significant differences were observed for BIC and BW toward membrane-treated groups (P<0.05).

CONCLUSION

Within the limits of this study, it was concluded that PRP does not exert additional effects on bone healing in bone defects created around dental implants and treated by GBR.

Surface treatments of titanium dental implants for rapid osseointegration

The osseointegration rate of titanium dental implants is related to their composition and surface roughness. Rough-surfaced implants favor both bone anchoring and biomechanical stability. Osteoconductive calcium phosphate coatings promote bone healing and apposition, leading to the rapid biological fixation of implants. The different methods used for increasing surface roughness or applying osteoconductive coatings to titanium dental implants are reviewed. Surface treatments, such as titanium plasma-spraying, grit-blasting, acid-etching, anodization or calcium phosphate coatings, and their corresponding surface morphologies and properties are described. Most of these surfaces are commercially available and have proven clinical efficacy (>95% over 5 years). The precise role of surface chemistry and topography on the early events in dental implant osseointegration remain poorly understood. In addition, comparative clinical studies with different implant surfaces are rarely performed. The future of dental implantology should aim to develop surfaces with controlled and standardized topography or chemistry. This approach will be the only way to understand the interactions between proteins, cells and tissues, and implant surfaces. The local release of bone stimulating or resorptive drugs in the peri-implant region may also respond to difficult clinical situations with poor bone quality and quantity. These therapeutic strategies should ultimately enhance the osseointegration process of dental implants for their immediate loading and long-term success.

Two Human Hydroxyapatite-Coated Dental Implants Retrieved After a 14-Year Loading Period: A Histologic and Histomorphometric Case Report

BACKGROUND

Controversy over the long-term clinical effectiveness of hydroxyapatite (HA)-coated dental implants still persists, despite numerous clinical studies documenting high survival rates. Concerns about the degradation of the coating over the years have been raised; it has been speculated that resorption of the HA could produce a space between the implant and the bone with a resultant mechanical instability.

METHODS

Two HA-coated implants were retrieved due to a fracture of the abutment screws after a loading period of 14 years and were treated to obtain thin ground sections for histologic evaluation.

RESULTS

At low-power magnification, it was possible to observe that the HA coating was in contact with mature bone. No gaps or connective fibrous tissue was found at the implant-bone interface. No epithelial downgrowth was present. No acute or chronic inflammatory cell infiltrate was present at the implant-bone interface. No foreign body reaction was present in the peri-implant tissues. Some osteocytes were in direct contact with the coating. For implant 1, the percentage of bone-titanium contact was 25% +/- 2.1%, and the percentage of bone-HA contact was 35% +/- 1.4%. The total bone-implant contact was approximately 60%. The HA coating appeared to be resorbed in 46% +/- 3.2% of the implant perimeter, especially in the coronal portions of the implant. For implant 2, the mean percentage of bone-HA contact was 13% +/- 1.8%, and the mean percentage of bone-titanium contact was 15% +/- 2.3%. The total bone-implant contact was approximately 28%. The HA coating appeared to be resorbed for a mean of 68% +/- 4.1% of the implant perimeter, especially in the coronal portion of the implant.

CONCLUSIONS

No acute or chronic inflammatory cell infiltrate was present in the peri-implant tissues. No signs of coating infection, fatigue, or failure were observed in two specimens. The HA coating may not be susceptible to degradation or dissolution under long-term function.

Influence of alcohol and tobacco habits on peri-implant marginal bone loss: a prospective study

A prospective clinical study was conducted to explore the possible link between peri-implant bone loss and the widespread habits of tobacco smoking and alcohol consumption. One hundred and eighty-five patients who received 514 implants were followed up for 3 years. Peri-implant marginal bone loss was evaluated by digital panoramic radiography and image analysis techniques. Multivariate analysis showed that peri-implant marginal bone loss was significantly related to a daily consumption of >10 g of alcohol, tobacco use and increased plaque levels and gingival inflammation. The present results indicate that daily alcohol consumption and tobacco use may have a negative influence on predictable long-term implant treatment outcomes, producing peri-implant bone loss and compromising restorative treatment with implant-supported prostheses.