Experimental study of turned and grit-blasted screw-shaped implants with special emphasis on effects of blasting material and surface topography

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.

Grafting of cross-linked hydrogel networks to titanium surfaces

The performance of medical implants and devices is dependent on the biocompatibility of the interfacial region between tissue and the implant material. Polymeric hydrogels are attractive materials for use as biocompatible surface coatings for metal implants. In such systems, a factor that is critically important for the longevity of an implant is the formation of a robust bond between the hydrogel layer and the implant metal surface and the ability for this assembly to withstand physiological conditions. Here, we describe the grafting of cross-linked hydrogel networks to titanium surfaces using grit-blasting and subsequent chemical functionalization using a silane-based adhesion promoter. Metal surface characterization was carried out using profilometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) analysis. Hydrogel layers composed of poly(ethylene glycol)-dimethacrylate (PEG-DMA), poly(2-hydroxyethylmethacrylate) (PHEMA), or poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) semi-interpenetrating polymer networks (semi-IPNs) have been prepared. The mechanical properties of these hydrogel-metal assemblies have been characterized using lap-shear measurements, and the surface morphology was studied by SEM and EDX. We have shown that both high surface roughness and chemical functionalization are critical for adhesion of the hydrogel layer to the titanium substrate.

Modified Titanium Surfaces Alter Osteogenic Differentiation: A Comparative Microarray-Based Analysis of Human Mesenchymal Cell Response to Commercial Titanium Surfaces

The differential effects of dual-acid etched (Osseotite), hydroxyapatite coated (HA) and sand-blasted/acid-etched (SLA) titanium surfaces on human bone marrow-derived mesenchymal cells (hMSCs) were investigated. Proliferation was significantly promoted on the SLA surfaces. 16 genes were significantly upregulated when hMSCs were cultured on the Osseotite and the HA surfaces and 15 genes on the SLA surfaces. Upregulated genes control cell differentiation, signal transduction, cell cycle regulation, angiogenesis, cell adhesion, and extracellular matrix and bone formation.

Biomaterials-based modulation of the immune system

The immune system is traditionally considered from the perspective of defending against bacterial or viral infections. However, foreign materials like implants can also illicit immune responses. These immune responses are mediated by a large number of molecular signals, including cytokines, antibodies and reactive radical species, and cell types, including macrophages, neutrophils, natural killer cells, T-cells, B-cells, and dendritic cells. Most often, these molecular signals lead to the generation of fibrous encapsulation of the biomaterials, thereby shielding the body from these biomaterials. In this review we will focus on two different types of biomaterials: those that actively modulate the immune response, as seen in antigen delivery vehicles for vaccines, and those that illicit relatively small immune response, which are important for implantable materials. The first serves to actively influence the immune response by co-opting certain immune pathways, while the second tries to mimic the properties of the host in an attempt to remain undetected by the immune system. As these are two very different end points, each type of biomaterial has been studied and developed separately and in recent years, many advances have been made in each respective area, which will be highlighted in this review.

Evaluation of stability changes in magnesium-incorporated titanium implants in the early healing period

The aim of the present study was to determine the bone response to magnesium (Mg) ion-incorporated titanium (Ti) implants during the early healing period. A total of 114 patients (69 men and 45 women aged between 29 and 71 years) participated in the study. Overall, one hundred thirty-three 10-mm-long fixtures were installed, composed of 65 Mg ion-incorporated fixtures in the test group (55 participants; 30 males and 25 females) and 68 resorbable blast media (RBM) surface fixtures in the control group (59 participants; 39 males and 20 females). The bone responses were evaluated by resonance frequency analysis (RFA) at the following time points after implant insertion (ie, the healing period): 0, 2, 4, 8, and 12 weeks. Each time an RFA measurement was taken, the stability changes relating to both bone quality and implant arch location (maxilla or mandible) were recorded for further analysis. The mean stabilities were lowest at week 4 of healing for both the test and control groups. Significant differences in RFA values between the 2 groups were found at week 12 of healing. The mean percentage change in implant stability quotient (ISQ) from the baseline revealed that the implant stability of the Mg ion-incorporated test group had increased (4.55%) more than the RBM surface group (2.23%) by week 12 of healing. With respect to bone quality, the mean ISQ of Mg-incorporated Ti implants only changed significantly during the 12-week period for type 4 bone. Furthermore, at weeks 4 and 12 of healing, significant differences were found between the 2 groups for type 2 and type 4 bone. A comparison of the stability patterns of mandibular and maxillary implants revealed that the overall stability was higher in the mandible; however, no significant difference was found for Mg-incorporated Ti implants. The Mg-incorporated Ti implants exhibited a slightly better bone response with respect to ISQ than did the RBM surface implants, and the percentage change in mean ISQ from the baseline was greater for the Mg-incorporated group than for the RBM surface group at the end point of this study.

Positive Biomechanical Effects of Titanium Oxide for Sandblasting Implant Surface as an Alternative to Aluminium Oxide

The aim of this study was to evaluate the physico-chemical properties and the in vivo host response of a surface sandblasted with particles of titanium oxide (TiO2) followed by acid etching as an alternative to aluminium oxide. Thirty titanium disks manufactured in the same conditions as the implants and 24 conventional cylindrical implants were used. Half of the implants had a machined surface (Gcon) while in the other half; the surface was treated with particles of TiO2 followed by acid etching (Gexp). Surface characterization was assessed by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), profilometry, and wettability. For the in vivo test, 12 implants of each group were implanted in the tibia of 6 rabbits, and were reverse torque tested after periods of 30 or 60 days after implantation. Following torque, SEM was utilized to assess residual bone-implant contact. The surface characterization by SEM showed a very homogeneous surface with uniform irregularities for Gexp and a small amount of residues of the blasting procedure, while Gcon presented a surface with minimal irregularities from the machining tools. Wettability test showed decreased contact angle for the Gcon relative to the Gexp. The Gexp removal torque at 30 and 60 days was 28.7%, and 33.2% higher relative to the Gcon, respectively. Blasting the surface with particles of TiO2 represents an adequate option for the surface treatment of dental implants, with minimal risk of contamination by the residual debris from the blasting procedure.

Estudo in vitro da influência do formato e do tratamento de superfície de implantes odontológicos no torque de inserção, resistência ao arrancamento e frequência de ressonância

OBJETIVO: A proposta do estudo foi avaliar a influência do formato e do tratamento de superfície na estabilidade primária de implantes odontológicos, inseridos em diferentes substratos, utilizando-se associação de métodos, como torque de inserção, resistência ao arrancamento e frequência de ressonância. MATERIAL E MÉTODO: Foram utilizados 32 implantes da marca Conexão® (Conexão Sistemas de Prótese Ltda, Arujá, São Paulo, Brasil), sendo: oito cilíndricos com tratamento Porous (CA), oito cilíndricos usinados (MS), oito cilíndricos tratamento duplo Porous (MP) e oito cônicos sem tratamento (CC). Os substratos utilizados para inserção foram: costela de porco; poliuretana Synbone©; poliuretana Nacional® (15, 20, 40 PCF), e madeira. O torque de inserção (TI) foi quantificado utilizando-se um torquímetro digital Kratos®; a força de arrancamento (RA) foi aferida por meio de tração axial, realizada em uma Máquina Universal de Ensaios (Emic® DL-10000), e utilizou-se também análise por meio de frequência de ressonância (RF). Para obtenção dos resultados estatísticos, utilizou-se análise de variância e teste de Tukey (significância de 5%). RESULTADO: Ao analisar o torque de inserção, verificou-se que os implantes com tratamento de superfície não foram diferentes estatisticamente dos usinados, assim como os implantes cilíndricos não tiveram diferença dos cônicos em todos os substratos (p>0,05), com exceção da poliuretana Synbone©. Em relação à resistência ao arrancamento, os implantes tratados e usinados, assim como cônicos e cilíndricos, não tiveram diferença estatística (p>0,05); a análise de frequência de ressonância mostrou que não houve diferença entre os implantes (p>0,05), com exceção da poliuretana Nacional® (20 PCF). CONCLUSÃO: Os formatos e o tratamento de superfície estudados não demonstraram valores significantes quando foram comparados os implantes entre si e, considerando os substratos avaliados, não houve diferença estatística entre os diferentes tipos de implantes.

The Influence of Low-Level Laser on Osseointegration Around Machined and Sandblasted Acid-Etched Implants: A Removal Torque and Histomorphometric Analyses

Evaluation of the influence of laser application on osseointegration around implants with different surface characteristics is limited. This study aims to evaluate the influence of low-level lasers on the early stages of osseointegration. Ninety-six external hex implants (3.75 mm × 5.0 mm) were placed in 24 rabbits-one machined and one sandblasted acid-etched per tibia. The rabbits were later divided into the laser group, which received a total dose of 24 J/cm(2) of gallium-aluminum-arsenide laser over 15 days, and a control group. At 16 and 30 days after surgery, removal torque and histomorphometric analyses were performed. No statistical differences in removal torque or histomorphometric analyses were verified between laser and control groups regardless of implant surface (P > .05). Time was the only variable presenting significant differences between measurements (P < .05). Low-level laser had no significant short-term effect on bone-to-implant contact and removal torque values regardless of implant surface characteristics.

The influence of surface treatment on the implant roughness pattern

An important parameter for the clinical success of dental implants is the formation of direct contact between the implant and surrounding bone, whose quality is directly influenced by the implant surface roughness. A screw-shaped design and a surface with an average roughness of Sa of 1-2 µm showed a better result. The combination of blasting and etching has been a commonly used surface treatment technique. The versatility of this type of treatment allows for a wide variation in the procedures in order to obtain the desired roughness.

Influence of Surface Treatments on the Bioactivity of Ti

Several techniques have been described to modify the surface of titanium to make it more bioactive. Heat treatment (HT) and sodium hydroxide treatment (NaOH) have been used and can change the crystallinity and surface chemistry of titanium implants. However, no studies have systemically focused on comparing these different methods and their effect on the bioactivity of Ti. Therefore, in this study, Ti substrates were systematically treated using HT, NaOH, and a combination of HT and NaOH. The Ti plates were heat treated at various temperatures, and the plates were subjected to HT followed by soaking in NaOH or first soaked in NaOH and then heat treated. The morphology, crystallinity, hardness, water contact angle, and surface energy of the samples were analyzed as well as the bioactivity after immersion in PBS. Morphology and crystallinity changed with increasing temperature. The difference was most pronounced for the 800°C treated samples. The water contact angle decreased, and the surface energy increased with increasing temperature and was highest for 800°C. The rutile surface showed faster hydroxyapatite formation. NaOH treatment of the HT Ti samples increased the surface energy and improved its bioactivity further. Also, HT of NaOH samples improved the bioactivity compared to only HT.

Comparing alumina-reduced and conventional surface grit-blasted acetabular cups in primary THA: early results from a randomised clinical trial

Alumina grit-blasted implants have been widely used in cementless total hip arthroplasty (THA). However, alumina particles can become embedded in the implant surface, leading to deposition in periprosthetic tissues and implant wear. We hypothesised that the alumina-reduced surface BICON-PLUS NT acetabular cup would improve implant fixation and clinical outcomes over the conventional surface BICON-PLUS cup. In a randomised controlled, double-blind study, patients with primary or secondary osteoarthritis requiring primary arthroplasty were randomly assigned to THA with either the BICON-PLUS or BICON-PLUS NT cup. All cups were combined with the SL-PLUS stem. In addition to clinical and radiographic assessments, dual-energy X-absorptiometry (DEXA) was performed preoperatively and at regular intervals during a planned 2-year follow-up period to measure bone mineral density as a marker of implant fixation. At 1 year, there were no differences in bone mineral density, or in clinical or radiographic outcomes between the BICON-PLUS and BICON-PLUS NT groups were identified, leading to early termination of the study. Both groups showed excellent clinical improvement and there were few complications. Both the alumina-reduced and conventional surface acetabular cups can be used with confidence in primary THA for osteoarthritis, although longer-term studies are required to confirm these findings.

Influence of nanocoated calcium phosphate on two different types of implant surfaces in different bone environment: an animal study

OBJECTIVE

The purpose of this study was to evaluate the osseointegration of two different types of surfaces, smooth and roughened surface implants nanocoated with calcium phosphate (CAP) around different bone environment.

MATERIALS AND METHODS

Five male mongrel dogs were used in this study. The premolars and molars were extracted on both sides of the mandible. Eight weeks after extraction, implants were submerged on both sides of the mandible. On the left, CAP nanocoated roughened surface (RCAP) implants were installed whereas, the CAP nanocoated smooth surface (SCAP) implants were installed on the right side. The control group had no defect, on the other hand, three-wall intrabony defects were surgically created adjacent to the implant in the experimental group. The dogs were sacrificed after 12 weeks.

RESULTS

Histological and histomorphometrical analysis were performed with the specimen. The SCAP and RCAP implants showed good osseointegration with no statistical significance in the control group. Histologically, the SCAP group showed little resolution of the defect compared with the RCAP group. In the experimental groups, there was a significant difference in defect fill between SCAP and RCAP.

CONCLUSION

Within the limits of our study, it can be concluded that SCAP and RCAP implants show no difference in sufficient bone area whereas, CAP nanocoating on roughened implant surface may enhance osseointegration in deficient bone environment.

Ordered and disordered proteins as nanomaterial building blocks

Proteins possess a number of attractive properties that have contributed to their recent emergence as nanoscale building blocks for biomaterials and bioinspired materials. For instance, the amino acid sequence of a protein can be precisely controlled and manipulated via recombinant DNA technology, and proteins can be biosynthesized with very high purity and virtually perfect monodispersity. Most importantly, protein-based biomaterials offer the possibility of technologically harnessing the vast array of functions that these biopolymers serve in nature. In this review, we discuss recent progress in the field of protein-based biomaterials, with an overall theme of relating protein structure to material properties. We begin by discussing materials based on proteins that have well-defined three-dimensional structures, focusing specifically on elastin- and silk-like peptides. We then explore the newer field of materials based on intrinsically disordered proteins, using nucleoporin and neurofilament proteins as case studies. A key theme throughout the review is that specific environmental stimuli can trigger protein conformational changes, which in turn can alter macroscopic material properties and function.

Peri-implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part II: a pilot study in dogs

PURPOSE

The aim of the present study was to evaluate bone-to-implant contact (BIC) and bone remodeling dynamics after immediate implant placement at different levels in relation to the crestal bone with two different implant designs in beagle dogs.

MATERIALS AND METHODS

The mandibular second, third and fourth premolars of six beagle dogs were extracted bilaterally and three implants were immediately placed in the hemi-arches of each dog. Randomly, three cylindrical and three tapered implants were inserted crestally (control group) or 2 mm subcrestally (test group). Both groups were treated with a minimal mucoperiosteal flap elevation approach. A gap from the buccal cortical wall to the implant was always left. Three dogs were allowed a 4-week submerged healing period and the other three an 8-week submerged healing period. The animals were sacrificed and samples were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out in order to compare BIC, de novo bone formation and bone remodeling.

RESULTS

All implants osseointegrated clinically and histologically. Healing patterns examined microscopically at 4 and 8 weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. The total BIC mean value for the crestal group was 36.48 ± 3.4% and for the subcrestal group was 41.46 ± 4.2%. The mean percentage of newly formed BIC was greater with the cylindrical implant design (46.06 ± 1.09%) than with the tapered design (33.89 ± 1.72%). There was less bone resorption in the subcrestal group (test) than crestal group (control).

CONCLUSION

These findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri-implant tissue remodeling. However, less resorption of the lingual crest may be expected when implants are placed 2 mm subcrestally. Moreover, higher BIC values were found in cylindrical implants placed subcrestally.

Biomedical Ti-Mo alloys with surface machined and modified by laser beam: biomechanical, histological, and histometric analysis in rabbits

PURPOSE

In vivo bone response was assessed by removal torque, hystological and histometrical analysis on a recently developed biomedical Ti-15Mo alloy, after surface modification by laser beam irradiation, installed in the tibia of rabbits.

MATERIALS AND METHODS

A total of 32 wide cylindrical Ti-15Mo dental implants were obtained (10mm × 3.75mm). The implants were divided into two groups: 1) control samples (Machined surface - MS) and 2) implants with their surface modified by Laser beam-irradiation (Test samples - LS). Six implants of each surface were used for removal torque test and 10 of each surface for histological and histometrical analysis. The implants were placed in the tibial metaphyses of rabbits.

RESULTS

Average removal torque was 51.5Ncm to MS and >90Ncm to LS. Bone-to-implant-contact percentage was significantly higher for LS implants both in the cortical and marrow regions.

CONCLUSIONS

The present study demonstrated that laser treated Ti-15Mo alloys are promising materials for biomedical application.

Surface characterization and biological response of carbon-coated oxygen-diffused titanium having different topographical surfaces

The materials (C-ODTi) with different topographical surfaces that possess interstitial oxygen atoms into the host titanium lattice and an upper nanometric surface layer of anatase-TiO(2) covered by a carbon thin layer were fabricated in this study. The carbon thin layer on the surface of C-ODTi was composed of amorphous carbon and nano-graphite crystals. In vitro tests, using human bone marrow-derived mesenchymal cells (hBMCs), were performed to check cytotoxicity, examining in particular cell morphology, cell proliferation, cell differentiation, and mineralization capability. After 10 days of culture a higher degree of cell viability was observed on the surface of C-ODTi with an abraded surface. We also observed that hBMCs cultured in direct contact with C-ODTi maintained their capability to express alkaline phosphatase activity (ALP) and formed mineralized nodules similar to the control cultures. Our results demonstrate that the carbon layer coating on the surface of C-ODTi possess better biological response than commercially pure titanium (cp Ti), which was evidenced by the higher proliferation rates of osteoblasts, higher osteo-differentiation and a higher mineralization capability.

Influence of novel nano-titanium implant surface on human osteoblast behavior and growth

PURPOSE

The aim of the study is to investigate human osteoblast-like cell behavior and growth in the presence of 3 different titanium implant surfaces.

MATERIALS

Human stem cells were first obtained and then sorted by fluorescence-activated cell sorter from mesenchymal stem cell clusters of human dental papilla. The obtained human dental papilla stem cells were induced to differentiate into osteoblast-like cells and were then analyzed by reverse transcriptase polymerase chain reaction and Western blot analyses. The cells proliferated and were cultured onto 3 different titanium discs (sandblasted, sandblasted and large-grit acid-etched, and full contact coverage [FCC]) and analyzed by scanning electron microscope.

RESULTS

In all analyses samples, a high cell activity was observed, with typical osteoblast mature morphostructural response on rough surface. The high number of osteoblast-like cells was found on titanium FCC discs. At the same time, scanning electron microscope analysis confirmed the high biocompatibility of this surface.

CONCLUSION

The rapid maturation of the osteoblast-like cells on FCC titanium surface suggests that this structure could play a central role during initial phases of bone healing processes.

Biomechanical and histologic evaluation of non-washed resorbable blasting media and alumina-blasted/acid-etched surfaces

OBJECTIVES

To compare the biomechanical fixation and histomorphometric parameters between two implant surfaces: non-washed resorbable blasting media (NWRBM) and alumina-blasted/acid-etched (AB/AE), in a dog model.

MATERIAL AND METHODS

The surface topography was assessed by scanning electron microscopy, optical interferometry and chemistry by X-ray photoelectron spectroscopy (XPS). Six beagle dogs of ∼1.5 years of age were utilized and each animal received one implant of each surface per limb (distal radii sites). After a healing period of 3 weeks, the animals were euthanized and half of the implants were biomechanically tested (removal torque) and the other half was referred to nondecalcified histology processing. Histomorphometric analysis considered bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Following data normality check with the Kolmogorov-Smirnov test, statistical analysis was performed by paired t-tests at 95% level of significance.

RESULTS

Surface roughness parameters S(a) (average surface roughness) and S(q) (mean root square of the surface) were significantly lower for the NWRBM compared with AB/AE. The XPS spectra revealed the presence of Ca and P in the NWRBM. While no significant differences were observed for both BIC and BAFO parameters (P>0.35 and P>0.11, respectively), a significantly higher level of torque was observed for the NWRBM group (P=0.01). Bone morphology was similar between groups, which presented newly formed woven bone in proximity with the implant surfaces.

CONCLUSION

A significant increase in early biomechanical fixation was observed for implants presenting the NWRBM surface.

Histologic and biomechanical evaluation of alumina-blasted/acid-etched and resorbable blasting media surfaces

This study evaluated the early biomechanical fixation and bone-to-implant contact (BIC) of an alumina-blasted/acid-etched (AB/AE) compared with an experimental resorbable blasting media (RBM) surface in a canine model. Higher texturization was observed for the RBM than for the AB/AE surface, and the presence of calcium and phosphorus was only observed for the RBM surface. Time in vivo and implant surface did not influence torque. For both surfaces, BIC significantly increased from 2 to 4 weeks.

Histomorphometric analysis and removal torque of small diameter implants with alternative surface treatments and different designs

This study was designed to investigate the histomorphometric and biomechanical comparison of small-diameter implants with different designs. These implants can be placed surgically in narrow bone spaces, such as the lower incisor region, that have low occlusal loading. Specimens of screw-shaped pin implants were designed for the study. These specimen implants were divided into 6 groups: group 1, machined implants; group 2, resorbable blast media (RBM)-treated implants; group 3, machined implants with a long vertical groove; group 4, RBM-treated implants with a long vertical groove; group 5, RBM-treated implants with a vertical groove on the upper thread; and group 6, RBM-treated implants with a vertical groove on the lower trunk. The specimen implants were placed surgically on the medial side of the rabbit tibia. Animals were sacrificed 2, 4, and 8 weeks after surgery. The removal torque was measured and tissues were prepared for histologic and histomorphometric analysis. The bone-to-implant contact and the percentage of the bone area inside the threads were measured. RBM-treated implants with vertical groove groups showed significantly higher values of removal torque, bone-implant contact, and bone area rate than the ones of machined surface groups.

An in vivo evaluation of bone response to three implant surfaces using a rabbit intramedullary rod model

Our study was designed to evaluate osseointegration among implants with three surface treatments: plasma-sprayed titanium (P), plasma-sprayed titanium with hydroxyapatite (PHA), and chemical-textured titanium with hydroxyapatite (CHA). Average surface roughness (Ra) was 27 microns for the P group, 17 microns for the PHA group, and 26 microns for the CHA group. Bilateral distal intramedullary implants were placed in the femora of thirty rabbits. Histomorphometry of scanning electron microscopy images was used to analyze the amount of bone around the implants at 6 and 12 weeks after implantation. Greater amounts of osseointegration were observed in the hydroxyapatite-coated groups than in the noncoated group. For all implant surfaces, osseointegration was greater at the diaphyseal level compared to the metaphyseal level. No significant differences were seen in osseointegration between the 6 and 12 week time points. Although the average surface roughness of the P and the CHA groups was similar, osseointegration of the CHA implants was significantly greater. The results of this in vivo lapine study suggest that the presence of an hydroxyapatite coating enhances osseointegration despite similarities in average surface roughness.

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.

The removal of Al2O3 particles from grit-blasted titanium implant surfaces: effects on biocompatibility, osseointegration and interface strength in vivo

For the improvement of surface roughness and mechanical interlocking with bone, titanium prostheses are grit-blasted with Al(2)O(3) particles during manufacturing. Dislocated Al(2)O(3) particles are a leading cause of third-body abrasive wear in the articulation of endoprosthetic implants, resulting in inflammation, pain and ultimately aseptic loosening and implant failure. In the present study, a new treatment for the removal of residual Al(2)O(3) particles from grit-blasted, cementless titanium endoprosthetic devices was investigated in a rabbit model. The cleansing process reduces residual Al(2)O(3) particles on titanium surfaces by up to 96%. The biocompatibility of the implants secondary to treatment was examined histologically, the bone-implant contact area was quantified histomorphometrically, and interface strength was evaluated with a biomechanical push-out test. Conventional grit-blasted implants served as control. In histological and SEM analysis, the Al(2)O(3)-free implant surfaces demonstrated uncompromised biocompatibility. Histomorphometrically, Al(2)O(3)-free implants exhibited a significantly increased bone-implant contact area (p=0.016) over conventional implants between both evaluation points. In push-out testing, treated Al(2)O(3)-free implants yielded less shear resistance than conventional implants at both evaluation points (p=0.018). In conclusion, the new surface treatment effectively removes Al(2)O(3) from implant surfaces. The treated implants demonstrated uncompromised biocompatibility and bone apposition in vivo. Clinically, Al(2)O(3)-free titanium prostheses could lead to less mechanical wear of the articulating surfaces and ultimately result in less aseptic loosening and longer implant life.

Influence of direct laser fabrication implant topography on type IV bone: a histomorphometric study in humans

The aim of this histologic study was to evaluate the influence of the direct laser fabrication (DFL) surface topography on bone-to-implant contact (BIC%), on bone density in the threaded area (BA%) as well as bone density outside the threaded area (BD%) in type IV bone after 8 weeks of unloaded healing. Thirty patients (mean age 51.34 +/- 3.06 years) received 1 micro-implant (2.5-mm diameter and 6-mm length) each during conventional implant surgery in the posterior maxilla. Thirty micro-implants with three topographies were evaluated: 10 machined (cpTi); 10 sandblasted and acid etched surface (SAE) and 10 DFL micro-implants. After 8 weeks, the micro-implants and the surrounding tissue were removed and prepared for histomorphometric analysis. Four micro-implants (2 cpTi, 1 SAE and 1DLF) showed no osseointegration after the healing period. Histometric evaluation indicated that the mean BIC% was higher for the DFL and SAE surfaces (p = 0.0002). The BA% was higher for the DFL surface, although there was no difference with the SAE surface. The BD% was similar for all topographies (p > 0.05). Data suggest that the DFL and SAE surfaces presented a higher bone-to-implant contact rate compared with cpTi surfaces under unloaded conditions, after a healing period of 8 weeks.

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.

Bone-added osteotome sinus floor elevation with simultaneous placement of non-submerged sand blasted with large grit and acid etched implants: a 5-year radiographic evaluation

PURPOSE

Implant survival rates using a bone-added osteotome sinus floor elevation (BAOSFE) procedure with simultaneous placement of a non-submerged sand blasted with large grit and acid etched (SLA) implant are well documented at sites where native bone height is less than 5 mm. This study evaluated the clinical results of non-submerged SLA Straumann implants placed at the time of the BAOSFE procedure at sites where native bone height was less than 4 mm. Changes in graft height after the BAOSFE procedure were also assessed using radiographs for 5 years after the implant procedure.

METHODS

The BAOSFE procedure was performed on 4 patients with atrophic posterior maxillas with simultaneous placement of 7 non-submerged SLA implants. At least 7 standardized radiographs were obtained from each patient as follows: before surgery, immediately after implant placement, 6 months after surgery, every year for the next 3 years, and after more than 5 years had passed. Clinical and radiographic examinations were performed at every visit. Radiographic changes in graft height were calculated with respect to the implant's known length and the original sinus height.

RESULTS

All implants were stable functionally, as well as clinically and radiographically, during the follow-up. Most of the radiographic reduction in the grafted bone height occurred in the first 2 years; reduction after 2 years was slight.

CONCLUSIONS

The simultaneous placement of non-submerged SLA implants using the BAOSFE procedure is a feasible treatment option for patients with severe atrophic posterior maxillas. However, the grafted bone height is reduced during the healing period, and patients must be selected with care.

Electrochemical growth behavior, surface properties, and enhanced in vivo bone response of TiO2 nanotubes on microstructured surfaces of blasted, screw-shaped titanium implants

TiO₂ nanotubes are fabricated on TiO₂ grit-blasted, screw-shaped rough titanium (ASTM grade 4) implants (3.75 × 7 mm) using potentiostatic anodization at 20 V in 1 M H₃PO₄ + 0.4 wt.% HF. The growth behavior and surface properties of the nanotubes are investigated as a function of the reaction time. The results show that vertically aligned nanotubes of ≈700 nm in length, with highly ordered structures of ≈40 nm spacing and ≈15 nm wall thickness may be grown independent of reaction time. The geometrical properties of nanotubes increase with reaction time (mean pore size, pore size distribution [PSD], and porosity ≈90 nm, ≈40–127 nm and 45%, respectively for 30 minutes; ≈107 nm, ≈63–140 nm and 56% for one hour; ≈108 nm, ≈58–150 nm and 60% for three hours). It is found that the fluorinated chemistry of the nanotubes of F-TiO₂, TiOF₂, and F-Ti-O with F ion incorporation of ≈5 at.%, and their amorphous structure is the same regardless of the reaction time, while the average roughness (Sa) gradually decreases and the developed surface area (Sdr) slightly increases with reaction time. The results of studies on animals show that, despite their low roughness values, after six weeks the fluorinated TiO₂ nanotube implants in rabbit femurs demonstrate significantly increased osseointegration strengths (41 vs 29 Ncm; P = 0.008) and new bone formation (57.5% vs 65.5%; P = 0.008) (n = 8), and reveal more frequently direct bone/cell contact at the bone–implant interface by high-resolution scanning electron microscope observations as compared with the blasted, moderately rough implants that have hitherto been widely used for clinically favorable performance. The results of the animal studies constitute significant evidence that the presence of the nanotubes and the resulting fluorinated surface chemistry determine the nature of the bone responses to the implants. The present in vivo results point to potential applications of the TiO₂ nanotubes in the field of bone implants and bone tissue engineering.

Dental implant systems

Among various dental materials and their successful applications, a dental implant is a good example of the integrated system of science and technology involved in multiple disciplines including surface chemistry and physics, biomechanics, from macro-scale to nano-scale manufacturing technologies and surface engineering. As many other dental materials and devices, there are crucial requirements taken upon on dental implants systems, since surface of dental implants is directly in contact with vital hard/soft tissue and is subjected to chemical as well as mechanical bio-environments. Such requirements should, at least, include biological compatibility, mechanical compatibility, and morphological compatibility to surrounding vital tissues. In this review, based on carefully selected about 500 published articles, these requirements plus MRI compatibility are firstly reviewed, followed by surface texturing methods in details. Normally dental implants are placed to lost tooth/teeth location(s) in adult patients whose skeleton and bony growth have already completed. However, there are some controversial issues for placing dental implants in growing patients. This point has been, in most of dental articles, overlooked. This review, therefore, throws a deliberate sight on this point. Concluding this review, we are proposing a novel implant system that integrates materials science and up-dated surface technology to improve dental implant systems exhibiting bio- and mechano-functionalities.

Cardoso LA, Shibli JA. Impact of Smoking on Human Bone Apposition at Different Dental Implant Surfaces: A Histologic Study in Type IV Bone

Smoking has adverse effects on peri-implant bone healing and can cause bone loss around successfully integrated implants placed on type IV bone. This study evaluated the influence of implant surface topography of microimplants retrieved from posterior maxilla of smokers after 2 months of unloaded healing. Seven partially edentulous patients received 2 microimplants (machined and sandblasted acid-etched surface) each during conventional implant surgery. Histometric evaluation showed that the mean bone to implant contact was 10.40 ± 14.16% and 22.19 ± 14.68% to machined and sandblasted acid-etched surfaces, respectively (P &lt; .001). These data suggest that the sandblasted acid-etched surface presented better results than the machined surface after a short healing time in smokers.