Interface mechanics and histomorphometric analysis of hydroxyapatite-coated and porous glass-ceramic implants in canine bone

Benefits of Residual Aluminum Oxide for Sand Blasting Titanium Dental Implants: Osseointegration and Bactericidal Effects

OBJECTIVES

The purpose of this work was to determine the influence of residual alumina after sand blasting treatment in titanium dental implants. This paper studied the effect of alumina on physico-chemical surface properties, such as: surface wettability, surface energy. Osseointegration and bacteria adhesion were determined in order to determine the effect of the abrasive particles.

MATERIALS AND METHODS

Three surfaces were studied: (1) as-received, (2) rough surface with residual alumina from sand blasting on the surface and (3) with the same roughness but without residual alumina. Roughness was determined by white light interferometer microscopy. Surface wettability was evaluated with a contact angle video-based system and the surface free energy by means of Owens and Wendt equation. Scanning electron microscopy equipped with microanalysis was used to study the morphology and determine the chemical composition of the surfaces. Bacteria (Lactobacillus salivarius and Streptococcus sanguinis) were cultured in each surface. In total, 110 dental implants were placed into the bone of eight minipigs in order to compare the osseointegration. The percentage of bone-to-implant contact was determined after 4 and 6 weeks of implantation with histometric analysis.

RESULTS

The surfaces with residual alumina presented a lower surface free energy than clean surfaces. The in vivo studies demonstrated that the residual alumina accelerated bone tissue growth at different implantation times, in relation to clean dental implants. In addition, residual alumina showed a bactericidal effect by decreasing the quantity of bacteria adhering to the titanium.

CONCLUSIONS

It is possible to verify the benefits that the alumina (percentages around 8% in weight) produces on the surface of titanium dental implants.

CLINICAL RELEVANCE

Clinicians should be aware of the benefits of sand-blasted alumina due to the physico-chemical surface changes demonstrated in in vivo tests.

Effect of Different Morphology of Titanium Surface on the Bone Healing in Defects Filled Only with Blood Clot: A New Animal Study Design

Background

The objective of the present histologic animal study was to analyze whether roughness of the titanium surface can influence and/or stimulate the bone growth in defects filled with the blood using a rabbit tibia model.

Materials and Methods

Forty sets (implant and abutment), dental implant (3.5 mm in diameter and 7 mm in length) plus healing abutment (2.5 mm in diameter), were inserted in the tibiae of 10 rabbits. Moreover, twenty titanium discs were prepared. The abutment and discs were treated by 4 different methods and divided into 4 groups: (group A) machined abutments (smooth); (group B) double acid etching treatment; (group C) treatment with blasting with particles of aluminum oxide blasted plus acid conditioning; (group D) treatment with thorough blasting with particles of titanium oxide plus acid conditioning. The discs were used to characterize the surfaces by a profilometer and scanning electronic microscopy.

Results

After 8 weeks, the new bone formation around the sets of the samples was analyzed qualitatively and quantitatively in relation to bone height from the base of the implant and presence of osteocytes. Group C (1.50±0.20 mm) and group D (1.62±0.18 mm) showed bone growth on the abutment with higher values compared to group A (0.94±0.30 mm) and group B (1.19±0.23 mm), with significant difference between the groups (P < 0.05). In addition, osteocyte presence was higher in groups with surface treatment related to machined (P < 0.05).

Conclusions

Within the limitations of the present study, it was possible to observe that there is a direct relationship between the roughness present on the titanium surface and the stimulus for bone formation, since the presence of larger amounts of osteocytes on SLA surfaces evidenced this fact. Furthermore, the increased formation of bone tissue in height demonstrates that there is an important difference between the physical and chemical methods used for surface treatment.

Evaluation of bone morphogenic proteins in periodontal practice

Forty years ago Marshal R. Urist discovered a substance in bone matrix that had inductive properties for the development of bone and cartilage, until date, at least 20 bone morphogenetic proteins (BMPs) have been identified, some of which have been shown in vitro to stimulate the process of stem cell differentiation into osteoblasts in human and animal models. The purpose of this paper is to give a brief overview of BMPs and to review critically the clinical data currently available on the use of BMPs in various periodontal applications. The literature on BMPs was reviewed. A comprehensive search was designed. The articles were independently screened for eligibility. Articles with authentic controls and proper randomization and pertaining specifically to their role in periodontal applications were included. The available literature was analyzed and compiled. The analysis indicates BMPs to be a promising, as well as an effective novel approach to reconstruct and engineer the periodontal apparatus. Here, we represent several articles, as well as recent texts that make up a special and an in-depth review on the subject. On the basis of the data provided in the studies that were reviewed BMPs provide revolutionary therapies in periodontal practice.

Evaluation of the Surface Treatment on Bone Healing in a Transmucosal 1-mm Area of Implant Abutment: An Experimental Study in the Rabbit Tibia

PURPOSE

The objective of the present study was to investigate the effect on bone tissue healing patterns in 1-mm area treated in the transmucosal surface of the abutment in the tibia of rabbits.

MATERIALS AND METHODS

Forty-six abutments were divided into two groups: control group (CG) with 14 abutments with smooth surface and experimental group (EG) with 32 abutments presenting a 1-mm area of the transmucosal surface treated through sandblasting with microparticles of titanium oxide followed by acid etching. Five samples of each group were analyzed using an optical laser profilometer for surface roughness characterization. Thirty-six Morse taper implants (3.5 mm in diameter and 7 mm in length) were inserted 1.5 mm subcrestal into the tibiae of nine rabbits. The implants were removed after 8, 10, and 12 weeks for histological analysis. The histological slides were prepared and analyzed qualitatively in relation to the new bone at the interface bone-abutment and quantitatively, in relation to bone height from the base of the implant. These data were computed and statistically compared inside the groups using analysis of variance and the U-test between groups for same time.

RESULTS

Both groups exhibited bone growth in the direction and over the surface of the abutments, with good healing. However, the EG group showed an increased height of bone formation in the crestal direction, and highly significant differences were observed (p < .001) between these measured values.

CONCLUSIONS

Under the limitations of the present study, histological follow-up at 8, 10, and 12 weeks showed that transmucosal 1-mm area of implant abutment with treatment of the surface facilitated the maintenance of bone height around the abutment compared with the same abutment with the totally smooth surface.

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.

A review of protein adsorption on bioceramics

Bioceramics, because of its excellent biocompatible and mechanical properties, has always been considered as the most promising materials for hard tissue repair. It is well know that an appropriate cellular response to bioceramics surfaces is essential for tissue regeneration and integration. As the in vivo implants, the implanted bioceramics are immediately coated with proteins from blood and body fluids, and it is through this coated layer that cells sense and respond to foreign implants. Hence, the adsorption of proteins is critical within the sequence of biological activities. However, the biological mechanisms of the interactions of bioceramics and proteins are still not well understood. In this review, we will recapitulate the recent studies on the bioceramic-protein interactions.

Administration of pamidronate alters bone-titanium attachment in the presence of endotoxin-coated polyethylene particles

Bisphosphonates are promising in the treatment of periprosthetic osteolysis induced by particulate wear debris. The in vivo effects of pamidronate with different doses and durations of administration on bone-titanium attachment in the presence of endotoxin-coated polyethylene particles were examined in a rat model in this study. Titanium pins and endotoxin-coated polyethylene particles were introduced into rat femoral canals followed by intraperitoneal injection of pamidronate every other day. The treatment varied in the dose from 0 to 40 microg/kg and the duration of either 10 days or 6 weeks. Bilateral femurs were harvested after 6 weeks and examined by bone densitometer and MicroCT scan. Pamidronate increased the bone density of the left, unoperated femurs in a dose and duration dependent manner. Bone-titanium attachment significantly increased in all treatment groups compared to the control group. When pamidronate was administered for 10 days, the increase of bone-titanium attachment was significantly dose-dependent. However, when pamidronate was given for 6 weeks at 4 microg/kg, the bone-titanium attachment was significantly (p < 0.001) lower compared to the 10 day treatment of the same dose, although it was significantly higher than controls. Our results suggest that pamidronate effectively increase bone-titanium attachment even in the presence of endotoxin-coated polyethylene particles. However, long-term administration may reduce its efficacy.

Accumulation of LPS by polyethylene particles decreases bone attachment to implants

Molecules absorbed on the surface of particulate wear debris may contribute to inflammatory reactions that lead to aseptic loosening of implants. Lipopolysaccharide (LPS), a bacterial endotoxin, can attach to many biomaterials and stimulate macrophages to secrete osteoclast-activating cytokines. We tested the adsorption of LPS by polyethylene particles in vitro and examined the biological effects of LPS absorption on bone remodeling around implants in vivo. Polyethylene particles were incubated in radiolabeled LPS solutions, and adsorption of LPS by the particles was quantified by radioassay. Because polyethylene particles are hydrophobic and less dense than water, they floated and clumped when incubated in a water solution of LPS, resulting in low adsorption of LPS. However, when particles were incubated in an ethanol solution of LPS, most of the LPS was adsorbed by the particles, and was resistant to washing with water. Triton X-100 (10%), however, effectively washed the LPS off the particles. In a rat model, the presence of polyethylene particles around the implant in the femoral canal decreased bone attachment to the implant at 6 weeks. Incubating the particles with LPS before implantation, or intermittent administration of LPS systemically, further decreased bone-implant attachment to similar extents, but had no effect on the bone density of the control side femurs. Our data indicate that polyethylene particles have high affinity for LPS, depending on many factors, especially the solvents of the LPS. Intermittent systemic administration of LPS affects bone remodeling but only occurs in the area containing polyethylene particles and titanium implants, supporting the hypothesis that the presence of polyethylene particles around implants can result in accumulation of LPS from exogenous sources. This may cause local levels of LPS that are high enough to affect bone remodeling around implants.

Experimental studies on a new bioactive material: HAIonomer cements

The lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents has resulted in the development of glass ionomer cements (GICs) for biomedical applications. In order to improve biocompatibility and biomechanically match GICs to bone, hydroxyapatite-ionomer (HAIonomer) hybrid cements were developed. Ultra-fine hydroxyapatite (HA) powders were produced using a new induction spraying technique that utilizes a radio-frequency source to spheriodize an atomized suspension containing HA crystallites. The spheriodized particulates were then held at 800 degrees C for 4 h in a carbolite furnace using a heating and cooling rate of 25 degrees C/min to obtain almost fully crystalline HA powders. The heat-treated particles were characterized and introduced into a commercial glass ionomer cement. 4 (H4), 12 (H12) and 28 (H28) vol% of fluoroalumino silicate were substituted by crystalline HA particles that were dispersed using a high-speed dispersion technique. The HAIonomer cements were subjected to hardness, compressive and diametral tensile strength testing based upon BS6039:1981. The storage time were extended to one week to investigate the effects of cement maturation on mechanical properties. Commercially available capsulated GIC (GC) and GIC at maximum powder:liquid ratio (GM) served as comparisons. Results were analyzed using factorial ANOVA/Scheffe's post-hoc tests and independent samples t-test at significance level 0.05. The effect of time on hardness was material dependent. With the exception of H12, a significant increase in hardness was observed for all materials at one week. A significant increase in compressive strength was, however, observed for H12 over time. At 1 day and 1 week, the hardness of H28 was significantly lower than for GM, H4, and H12. No significant difference in compression and diametral tensile strengths were observed between materials at both time intervals. Results show that HAIonomers is a promising material, which possess good mechanical properties. Potential uses of this new material include bone cements and performed implants for hard tissue replacement in the field of otological, oral-maxillofacial and orthopedic surgery.

Dental materials: 1996 literature review. Part 2

This critical review of the published literature on dental materials for the year 1996 has been compiled by the Dental Materials Panel of the UK. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, resin-bonded bridges and ceramo-metallic restorations, ceramics, denture base resins and soft lining materials, impression materials, implants materials, orthodontic materials, biomechanics and image processing, resin composites and casting investment materials and waxes). Three hundred and thirteen articles have been reviewed.

Reconstruction of human maxillary defects with nacre powder: histological evidence for bone regeneration

The defective areas in the premolar-molar region of maxillary alveolar bone of eight patients were reconstructed using powdered nacre from the giant oyster Pinctada maxima. Histological, microradiographic and polarized light studies of drill biopsies taken 6 months postoperatively showed that nacre was tightly bound to newly-formed bone. The nacre was gradually and centripetally biodissolved and replaced with immature and then mature lamellar bone. These results are in agreement with our previous experimental in vitro data indicating that nacre has good osteogenic properties.