Effects on wound healing of hydroxyapatite-collagen complex implants in periodontal osseous defects in the dog

Animal models for periodontal regeneration and peri-implant responses

Translation of experimental data to the clinical setting requires the safety and efficacy of such data to be confirmed in animal systems before application in humans. In dental research, the animal species used is dependent largely on the research question or on the disease model. Periodontal disease and, by analogy, peri-implant disease, are complex infections that result in a tissue-degrading inflammatory response. It is impossible to explore the complex pathogenesis of periodontitis or peri-implantitis using only reductionist in-vitro methods. Both the disease process and healing of the periodontal and peri-implant tissues can be studied in animals. Regeneration (after periodontal surgery), in response to various biologic materials with potential for tissue engineering, is a continuous process involving various types of tissue, including epithelia, connective tissues and alveolar bone. The same principles apply to peri-implant healing. Given the complexity of the biology, animal models are necessary and serve as the standard for successful translation of regenerative materials and dental implants to the clinical setting. Smaller species of animal are more convenient for disease-associated research, whereas larger animals are more appropriate for studies that target tissue healing as the anatomy of larger animals more closely resembles human dento-alveolar architecture. This review focuses on the animal models available for the study of regeneration in periodontal research and implantology; the advantages and disadvantages of each animal model; the interpretation of data acquired; and future perspectives of animal research, with a discussion of possible nonanimal alternatives. Power calculations in such studies are crucial in order to use a sample size that is large enough to generate statistically useful data, whilst, at the same time, small enough to prevent the unnecessary use of animals.

Effect of new bone substitute materials consisting of collagen and tricalcium phosphate

The purpose of this study was to investigate the effect of new bone substitute materials consisting of collagen and tricalcium phosphate (TCP). Prior to the experiment, mandibular dog teeth were extracted. After 3 months, specific cavities were prepared on the alveolar ridge. In one group, cavities were filled with collagen sponge (CS group), in the other, cavities were filled with TCP sponge (TCP group). Cavities with no fillings (Cont group) were created as controls. Mandibular bone was evaluated histopathologically at experimental time periods of 1, 2, 4, and 8 weeks. Due to the non critical inflammatory symptoms that each group showed throughout all the time periods investigated, a low irritation level was observed. Absorption of material was almost complete at after 4 weeks in the CS group, and at after 8 weeks in the TCP group. At the top of the cavity, the TCP group exceeded the Cont group in amount of neogenesis at after 8 weeks. The materials examined in this study showed good osteoconduction and biodegradable character. The TCP Group, in particular, showed highly acceptable results, demonstrating that the materials used were excellent candidates as bone substitute materials.

Histological Evaluation of Apatite Cement Containing Atelocollagen

Tissue response to apatite cement (AC) containing atelocollagen (AC (ate)) was evaluated using conventional AC (c-AC) as a control material. At one week, the only difference between AC (ate) and c-AC was found in the soft tissue response. With c-AC, a moderate inflammatory response was exhibited: small particles of c-AC were scattered in the cutaneous tissue and many foreign body giant cells were aggregated around the scattered c-AC, whereas AC (ate) showed only a slight inflammatory response with few foreign body giant cells. In terms of bone tissue response, difference between AC (ate) and c-AC was observed at four weeks. New bone formation was observed along the cement at the edge of the pre-existing cortical bone in both c-AC and AC (ate). However, in the case of AC (ate), more abundant and thicker new bone was formed along the cement in the bone marrow when compared with c-AC.

Characterization of nano hydroxyapatite/collagen surfaces and cellular behaviors

Osseointegration at the bone-implant interface is a prerequisite for endosseous implants to succeed in achieving and maintaining their long-term stability in bone tissue. The achievement of osseointegration is significantly affected by surface nature of implants. To optimize osseointegration, this study presents the characterization of synthesized nanocrystalline hydroxyapatite (nano HA) and in vitro studies on nano HA, nano-HA/collagen, and titanium surfaces. Voids were found within the grain of nano HA, which consisted of the shell and the core. The finding assists the clarification of microstructures of nano HA. By low-temperature mixing nano-HA sol with collagen gel (nano-HA/collagen 80:20), nano HA, and nano-HA/collagen coated on pure titanium or porous anodic titanium oxides resulted in higher wettability and lower roughness. The in vitro studies showed that porous structures produced by anodic oxides on titanium served as positive anchorage sites for cell filopodia to connect, and nano HA decreased cell attachment of osteoblasts and induced well-developed long filopodia and broad lamellipodia, thereby enhancing cellular motility. Collagen involvement enhanced cell adhesion to nano HA. Cell reactions to nano HA, nano-HA/collagen, native, and porous titanium surfaces provide some guidance for an optimal osseointegration by their application in surface modifications for implants.

An in vivo study of a bone grafting material consisting of hydroxyapatite and reconstituted collagen

This study aims to evaluate the performance of our recently developed microspheres of hydroxyapatite/reconstituted collagen as a bone grafting material. The microspheres were fabricated into a circular disc and implanted in a pre-drilled hole in a rat's calvaria. The bone tissue had regenerated and grown into the disc bone graft 4 weeks following implantation. After 16 weeks of implantation, the regenerated bone had integrated with the remaining material and made close contact with it. The disc had been completely absorbed with almost no visible bone graft left after 24 weeks of implantation. In contrast, a hydroxyapatite disc still remained intact on the 24th week after implantation. These results suggested that the hydroxyapatite/reconstituted collagen microsphere can be used as an excellent bone grafting material.

A comparative study on the use of a HA/collagen/chondroitin sulphate biomaterial (Biostite) and a bovine-derived HA xenograft (Bio-Oss) in the treatment of deep intra-osseous defects

OBJECTIVES

This parallel-group, randomized, clinical trial was designed to evaluate the clinical outcome of deep intra-osseous defects following reconstructive surgery with the use of a synthetic hydroxyapatite/equine Type I collagen/chondroitin sulphate biomaterial (Biostite), as compared to a bovine-derived hydroxyapatite xenograft (Bio-Oss).

MATERIAL AND METHODS

Twenty-four systemically healthy subjects with moderate to advanced periodontitis, 11 females and 13 males, aged 30-64 years, seven smokers, were selected. Patients presented with one interproximal deep intra-osseous defect (intra-osseous component >or=4 mm) as clinically and radiographically evaluated. Immediately before surgery and 12 months after surgery, pocket probing depth (PPD), clinical attachment level (CAL) and radiographic depth of the defect (DEPTH) were evaluated.

RESULTS

Thirteen defects were treated with Biostite (test) and 11 defects with Bio-Oss (control). In the test group, PPD amounted to 7.8+/-1.3 mm before surgery, and decreased significantly to 3.6+/-1.6 mm 12 months following surgery, while in the control group PPD significantly decreased from 7.5+/-2.0 mm pre-surgery to 3.1+/-1.0 mm post-surgery. At 1 year, CAL gain and DEPTH gain were 2.9+/-1.9 and 2.5+/-1.4 mm, respectively, in the test group, and 4.0+/-2.4 mm and 3.1+/-1.8 mm, respectively, in the control group. No statistically significant differences for PPD reduction, CAL gain and DEPTH gain were detected between the groups.

CONCLUSIONS

The results of the present study indicate that both Biostite and Bio-Oss grafting biomaterials have determined a clinically and statistically significant improvement in terms of CAL gain, PPD reduction and radiographic DEPTH gain when used for the treatment of deep intra-osseous defects.

Porous alginate/hydroxyapatite composite scaffolds for bone tissue engineering: Preparation, characterization, andin vitro studies

In this study a series of alginate/hydroxyapatite (HAP) composite scaffolds was prepared by phase separation. HAP was incorporated into the alginate gel solution to improve both the mechanical and cell-attachment properties of the scaffolds. These scaffolds had a well-interconnected porous structure with an average pore size of 150 microm and over 82% porosity. The alginate/HAP scaffold prepared at -40 degrees C with a 50% HAP content showed the best mechanical properties. The morphology of scaffolds could be manipulated by tuning the quenching temperature during the preparation. The dissolution of alginate/HAP composite scaffolds could be slowed by the pretreating them by immersion in 1.0 M CaCl(2) solution. The rat osteosarcoma UMR106 cells, an osteoblastic cell line, seeded in the scaffolds, displayed better cell attachment to the 75/25 and 50/50 alginate/HAP composite scaffolds than to the pure alginate scaffold. The natural polymeric sponges that fabricated in this study may be a promising approach for tissue-engineering applications.

Collagen-hydroxyapatite/tricalcium phosphate microspheres as a delivery system for recombinant human transforming growth factor-beta 1

The purpose of this study is to evaluate the carrier capability of collagen-hydroxyapatite/tricalcium phosphate (Col-HA/TCP) microspheres to the rhTGF-beta 1 (recombinant human transforming growth factor-beta 1). After anesthesia, a bone defect (7.0 mm in diameter and 10.0 mm in depth) was created at the distal femoral condyles of New Zealand white rabbits. These defects were then completely filled with the implant materials. After 5, 7, 9, 11, 13, and 15 weeks, the animals were sacrificed and histological evaluations were performed. The results showed that when the defects were treated with Col-HA/TCP microspheres without rhTGF-beta 1, there was only spotty new bone formation during the 15 week experimental period and most of the defect was filled with fibrous tissue and inflammatory cells, whereas active bone formation with mature marrow tissue formation was evident in the defect treated with Col-HA/TCP microspheres containing rhTGF-beta 1. Collagen-hydroxyapatite/tricalcium phosphate microspheres were expected to be replaced by the regenerated bone structure as the bone reconstruction and bone-remodeling process occurred. It was apparent that bone regeneration was influenced by the addition of rhTGF-beta 1. Collagen-hydroxyapatite/tricalcium phosphate microspheres were a good carrier for rhTGF-beta 1.

Collagen-hydroxyapatite microspheres as carriers for bone morphogenic protein-4

The purpose of the current study is to evaluate the carrier capability of collagen-hydroxyapatite microspheres to the bone morphogenic proteins (BMP). After anesthesia, a bone defect (6.0 mm in diameter and 10.0 mm in depth) was created at the distal femoral condyles of New Zealand white rabbits. These 10.0 mm3 defects were then completely filled with the implant materials. After 2, 4, 6, and 8 weeks, the animals were sacrificed and histological evaluations were performed. The results showed that when the defects were left untreated, there was no evidence of bone formation during the eight-week experimental period. In the group treated with collagen-hydroxyapatite microspheres without BMP-4, the defect was filled with fibrous tissue and inflammatory cells, while active bone formation with mature marrow tissue formation was evident in the defect treated with collagen-hydroxyapatite microspheres containing BMP-4. Collagen-hydroxyapatite microspheres were expected to be replaced by the regenerated bone structure as the bone reconstruction and bone remodelling process occurred. It was apparent that bone regeneration was influenced by the addition of BMP-4. Collagen-hydroxyapatite microspheres were good carriers for bone morphogenic proteins.

A trial to prepare biodegradable collagen-hydroxyapatite composites for bone repair

This paper is a trial to prepare collagen-hydroxyapatite composites in vitro by an alternate immersion method. Collagen sponges of different biodegradabilities were prepared through chemical cross-linking of Type I collagen with glutaraldehyde (GA) at concentrations of 0.2, 1.0, and 2.0 wt%. The sponges were immersed at 37 degrees C in Tris-HCl-buffered solution containing 200 mM CaCl2 (pH 7.4) for 2 h and then in an aqueous solution of 120 mM Na2HPO4 (pH 9.3) for a 2 h further (one immersion cycle). The alternate immersion cycle was repeated for different times to obtain collagen-hydroxyapatite composites. The characterization of the resulting composites was performed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD), and scanning electron microscopy (SEM). The weight of composites increased with an increase in immersion cycles and the rate of increase became greater with higher GA cross-linking levels for collagen sponge preparation. The pH of the phosphate solution decreased with the immersion cycle, which suggests H+ generation accompanied hydroxyapatite formation. Irrespective of the GA concentration and immersion cycle, every composite showed IR absorption bands attributable to phosphate and hydroxyl groups at 950-1100 or 550-650 and 3000-3500 cm(-1) and broad peaks specific to hydroxyapatite on the XRD charts. SEM study revealed small white clusters of hydroxyapatite interspersed uniformly on/in the collagen framework without any preferential orientation. The composite prepared from 0.2 wt% GA cross-linked collagen sponge which showed favourable characteristics was applied to a rat skull defect to evaluate its osteoconductivity as well as biodegradability. The formation of new bone tissue was histologically observed at the defect 12 weeks after application in marked contrast to the collagen sponge alone. The composite degraded without any inflammation reaction. It is concluded that the collagen-hydroxyapatite composite prepared by the present method is a biodegradable biomaterial of osteoconductivity applicable to bone repair.

Microspheres of hydroxyapatite/reconstituted collagen as supports for osteoblast cell growth

Microspheres comprised of particulate hydroxyapatites dispersed in fibrous collagen matrices were prepared. The procedure involved the droplet formation of hydroxyapatite/collagen mixture emulsified in olive oil, followed by the reconstitution of collagen in the presence of hydroxyapatite particles at 37 degrees C. Various sizes of microspheres could be obtained by controlling the stirring speed of the emulsified mixture. By increasing the stirring speed from 200 to 350 and 500 rpm, the average diameter of the microspheres decreased from 1038 to 513 and 226 microm, respectively. The sizes of the microspheres reduced substantially to a range of 141 microm when 2%. Span 85 was present in the emulsion mixture stirring at 200 rpm. The microspheres thus obtained can be used as carriers to support the growth of osteoblast cells. Osteoblast cells derived from calvaria proliferated from 1.5 x 10(5) to 4.5 x 10(5) cells/ml in 7 days. Correspondingly, the alkaline phosphatase activity increased 6 fold during this period. These results suggested that the hydroxyapatite/collagen microspheres could be used as the filling materials for bone defect.

Guided tissue regeneration in conjunction with hydroxyapatite-collagen grafts for intrabony defects. A clinical and radiological evaluation

This clinical and radiological study evaluated the healing of 3 + 2 + 1 wall-combined intrabony defects treated using the guided tissue regeneration technique (GTR) with and without hydroxyapatite-collagen alloplastic graft materials (HAC), in comparison to that of HAC alone and conventional flap surgery (CF). 40 interproximal defects with probing depth > 6 mm were treated in 18 adult periodontitis patients of ages 35-60 years. After non-surgical therapy, the defects were randomly grouped into 4 groups of 10 defects each. These groups were designated: (1) expanded polytetrafluoroethylene membrane (e-PTFE), (2) e-PTFE + HAC, (3) HAC alone and (4) CF. At 6 months, the following changes in parameters were recorded. Mean PPD reduction for each group was 5.83, 5.85, 3.80 and 3.17 mm respectively. PPD reduced very significantly in all groups (p < 0.01), the highest and lowest reductions in PPD being for the e-PTFE + HAC and CF group respectively. Comparison between the 4 groups showed higher PPD reduction in both membrane groups than in either of the non membrane groups (p < 0.05) with the difference between the e-PTFE and CF groups being very highly significant (p < 0.001). Mean attachment gain for the 4 groups was 3.70, 3.80, 2.60 and 2.1 mm, respectively. Similarly attachment gain for all groups was very significant (p < 0.01) and the highest and lowest attachment gains were for the e-PTFE + HAC and CF group respectively. Both membrane groups showed significantly more attachment gain than the CF group (p < 0.05). Change in probing bone level (BL) for the 4 groups was 1.60, 1.90, 1.0 and 0.65 mm respectively. Again the highest changes in BL were recorded for the e-PTFE + HAC group. Significant differences were found between both membrane groups and the CF group (p < 0.05). Radiological evaluation using standardized radiographs and millimeter grids showed change in radiographic bone level at the deepest point of the defect on the radiograph to be 1.50, 1.55, 0.85 and 0.60 mm, respectively and this was significantly higher in both membrane groups than in the CF group (p < 0.05). This study therefore found e-PTFE membranes both alone and when combined with HAC to lead to more attachment gain and bone fill than did HAC alone or CF. It found HAC combined with e-PTFE to perform better although not significantly better than e-PTFE alone.