Evert Schepers

Bioactive glass particles of narrow size range: a new material for the repair of bone defects

A clinical trial to treat dental osseous lesions with bioactive glass granules of narrow size range (300 to 360 μm) has been conducted since early spring 1990. This study followed an animal study in which the osseous tissue repair properties of bioactive glass granules of narrow size range and hydroxyapatite granules were compared for up to 2 years of implantation. The therapeutic response to the bioactive glass material exceeded the response to the hydroxyapatite as evidenced by very extensive osteoconduction, as well as the capacity to cause differentiation of osteoprogenitor cells to osteoblasts. The clinical study was started by virtue of the bioactive glass granules of narrow size range eliciting expeditious bone tissue formation throughout a defect. In this clinical study 87 patients and 106 defects were treated. The indications selected were apical resection areas, cystic defects, extraction sites, and defects of the alveolar ridge due to surgery or resorption. After insertion, the particles remained well in place and only small changes in the contours of the restored defects were seen, at the most up to 2 months postinsertion. At 3 months the application sites had fully solidified. Radiographic analysis indicated that the material integrated into the bone tissue, and at 6 months any difference between glass particles and bone tissue had nearly disappeared. The few initial cases with limited clinical results were caused by factors unrelated to the glass granules, mostly the surgical technique. By adapting the surgical technique, no unfavorable clinical results were subsequently experienced. The follow-up, exceeding 3 years, demonstrated that bioactive glass granules of narrow size range constitute a valuable material to aid in the repair of dental bone lesions. (Implant Dent 1993;2:151–156)

Guiding Periodontal Pocket Recolonization: a Proof of Concept

The complexity of the periodontal microbiota resembles that of the gastro-intestinal tract, where infectious diseases are treatable via probiotics. In the oropharyngeal region, probiotic or replacement therapies have shown some benefit in the prevention of dental caries, otitis media, and pharyngitis, but their effectiveness in the treatment of periodontitis is unknown. Therefore, this study addressed the hypothesis that the application of selected beneficial bacteria, as an adjunct to scaling and root planing, would inhibit the periodontopathogen recolonization of periodontal pockets. Analysis of the data showed, in a beagle dog model, that when beneficial bacteria were applied in periodontal pockets adjunctively after root planing, subgingival recolonization of periodontopathogens was delayed and reduced, as was the degree of inflammation, at a clinically significant level. The study confirmed the hypothesis and provides a proof of concept for a guided pocket recolonization (GPR) approach in the treatment of periodontitis.

Bone healing in porous implants: a histological and histometrical comparative study on sheep

Tissue integration in four types of porous implant materials (Interpore 200® or Corallin hydroxyapatite, hydroxyapatite blocks, hydroxyapatite granules and polymethylmethacrylate) was evaluated in vivo. Porous blocks measuring 20 mm × 10 mm × 8 mm were implanted in mandibles and iliac crests of sheep. Bone healing in porous blocks was studied at 2 and 6 months after implantation. The behavior of the material itself was also analyzed. Histological and histomorphometrical analysis revealed bone healing depending upon healing time and material. On the basis of analysis of variance, differences in amounts of bone ingrowth at 2 and 6 months were statistically significant (p = 0.0039 in mandible; p = 0.0351 in iliac crest). The longer the time span, the more mineralized tissues were observed in the specimen. Our data confirmed that hydroxyapatite has osteoconductive capacities. Porous PMMA was found to be biocompatible, but it showed less bonegrowth within the pores. Interpore 200®, which had the highest surface to volume ratio was found to display the highest level of osseointegration and biodegradation.

Microchemical transformation of bioactive glass particles of narrow size range, a 0-24 months study.

Previous studies demonstrated the capacity of bioactive glass particles of narrow size range (300–355 μm, Biogran®) to stimulate bone tissue formation without contact with pre-existing bone tissue. Chemical interactions between the bioactive glass and the surrounding tissue fluids caused the glass transformation. This study quantifies the time-dependent transformation process. Particles were implanted in the jaws of beagle dogs and resected after 1, 2, 3, 6, 12 and 24 months. Microchemical analysis was performed using a scanning electron microscope equipped with an energy dispersive X-ray analysis system. After one month, Na-ions were leached out and the particles transformed into two layers. In the center, a Si-rich gel was found on the outer surface, a Ca- and P-rich shell. After two months, the concentration levels of the outer Ca- and P-rich shell remained. In the center the Si-concentration decreased and the Ca and P concentration increased. After three months, Si disappeared completely from the center of the particle, while the Ca and P concentration increased. At one and two years, the Ca and P concentrations in the transformed particles equalled those of bone tissue, turning the transformed particle into a chemical equivalent of the bone mineral phase.

Quantitative Screening of Engineered Implants in a Long Bone Defect Model in Rabbits

We have standardized a long bone defect model in rabbits to quantitatively compare the bone healing performance of engineered biological implants and have tested the bone healing efficiency of porous cylindrical scaffolds (ø-h, 6-20 mm [diameter 6 mm, height 20 mm] porosity, 70%) that were produced from hydroxyapatite (HA), titanium (Ti), and a novel biodegradable polymer-bioceramic composite (PH70alphaTCP). Scaffolds were perfused with or without 20 x 10(6) rabbit periosteal cells (RPCs) in a bioreactor and implanted in a standardized 2 cm defect in rabbit tibiae. X-rays revealed that new bone had formed at 3 weeks after creation of the defects. At sacrifice after 10 weeks, bone corticalization was observed in the majority of animals. Although PH70alphaTCP scaffolds did not inhibit callus formation, histomorphometric analysis revealed that there was no bone within the biomaterial, in contrast to HA and Ti scaffolds (bone volume ranging from 10% to 25%). We found that Ti and HA scaffold had good osteoconductive properties, but only HA scaffolds seeded with RPCs contributed to long bone mechanical functionality, with the maximum energy and angle being 308% and 155% greater than in control defects without scaffold.

Interfacial tissue response to bioactive glasses with reduced surface reactivity

Bone bonding of surface active glasses paralleled compositional changes of the reacting glass surface. These reaction layers, however, were susceptible to mechanical failure upon loading. The objective of the current work was to study the relationship between the kinetics of the thickness of the interfacial layers and the glass composition. Specifically the composition was changed by adding CaF2 and by increasing the SiO2 concentration. Three samples of each of five glass compositions were implanted in the partial edentulous jaws of beagle dogs. After 3 months, they were resected and prepared for histological analysis with the implants in situ. Bone bonding was observed at the surface of all five glass compositions. The glasses with low CaF2 content showed large areas of bone bonding and the bone growth along the implant surface was enhanced by osteoconductivity. The bone bonding around glasses with high CaF2 content was rather patchy. Small areas of bone bonding alternated with small islands of fibrous tissue contact. Osteoconductivity was observed also around these glass compositions. Scanning electron microscopy analysis revealed that the thickness of the reacted glass decreased with an increase of the CaF2 concentration. The glasses with high CaF2 concentrations showed spots of excessive ion dissolution which could delay the bone bonding in this area. This was due probably to local variations of the microstructure of the glass. CaF2 addition increased the risk for crystallization of the glass. It was suggested that the interface boundaries between the crystalline and amorphous phases were more susceptible for ion dissolution.