Biomedical subjects

M Ekholm

Publications and source records attributed to M Ekholm.

5 recordsLinked to original sources

PubMed2006

A histological and immunohistochemical study of tissue reactions to solid poly(ortho ester) in rabbits.

In many cases only the temporary presence of a biomaterial is needed in tissue support, augmentation or replacement. In such cases biodegradable materials are better alternatives than biostable ones. At present, biodegradable polymers are widely used in the field of maxillofacial surgery as sutures, fracture fixation devices and as absorbable membranes. The most often used polymers are aliphatic polyesters, such as polyglycolic acid (PGA) and polylactic acid (PLA). Poly(ortho ester) is a surface eroding polymer, which has been under development since 1970, but is used mostly in drug delivery systems in semisolid form. The aim of this study was to evaluate the tissue reactions of solid poly(ortho ester) (POE), histologically and immunohistochemically. Resorption times and the effect of 2 different sterilization methods (gamma radiation and ethylene oxide) upon resorption were also evaluated. Material was implanted into the tibia and subcutaneously into the mandibular ramus area of 24 rabbits. Follow-up times were 1-10, 14 and 24 weeks. Histological studies showed that POE induces a moderate inflammation in soft tissue and in bone. At 24 week follow-up, inflammation was mild in soft tissue and moderate in bone. In immunohistochemical studies, no highly fluorescent layer of tenascin or fibronectin was found adjacent to the implant. Resorption of gamma-sterilized rods was faster than ethylene oxide-sterilized rods. The total resorption time was more than 24 weeks in both groups. Clinically the healing was uneventful and the implants the well tolerated by the living tissue. This encourages these authors to continue studies with this interesting new material to search for the ideal material for bone filling and fracture fixation.

Absorbable Implants↗

PubMed2006

The copolymer of epsilon-caprolactone-lactide and tricalcium phosphate does not enhance bone growth in mandibular defect of sheep.

In the field of craniomaxillofacial and orthopaedic surgery there is a constant need for bone or bone substitute. At the present, the most effective way to enhance bone healing clinically is to use autogenous bone grafts. The problems associated with the use of these autografts are donor site morbidity, limited supply and need for a second operative site. Currently there are several different synthetic products commercially available in the market; nevertheless, none of them is ideal for filling bone defects. Therefore, search for new synthetic materials for bone replacement is necessary. A mixture of tricalcium phosphate (TCP) and epsilon-caprolactone-lactide copolymer P(epsilon -CL/DL-LA) was prepared and implanted in critical size mandibular bone defects in twelve sheep. Contralateral side was used as a control. Follow-up times for histological and radiological studies were 9, 14, 24 and 52 weeks. We found that the implanted material did not enhance bone formation compared to control site. We also confirmed that defect size was of critical size, since there was no complete healing of the control site either. The results do not encourage us to continue our studies with the mixture of TCP and P(epsilon-CL/DL-LA) as a filling material for bone defects. Therefore the search for the ideal material is still ongoing.

Animals↗

PubMed1999

Histological study of tissue reactions to epsilon-caprolactone-lactide copolymer in paste form.

In previous studies, epsilon-caprolactone-lactide copolymer in solid form has been used in experimental animals as suture material, and as a biodegradable nerve guide. The aim of the study reported here was to assess tissue reactions to epsilon-caprolactone-lactide copolymer in paste form, histologically, and to compare bone healing at the sites of implantation versus that at control sites. The other purpose of the study was to evaluate the properties of the implanted material as a filling material for bone defects. Resorption time and intensity of inflammatory reaction were also evaluated. Material was implanted into the abdominal walls and femurs of 34 rats. Follow-up times were from 2 weeks to 1 year. The results showed that epsilon-caprolactone-lactide copolymer in paste form induces a severe inflammatory reaction when placed in muscle, and moderate inflammation when implanted into bone. The resorption time was more than 1 year. Bone healing at sites of implantation was slower than at control sites.

Animals↗

PubMed1999

Mixture of epsilon-caprolactone-lactide copolymer and tricalcium phosphate: a histological and immunohistochemical study of tissue reactions.

In cranio-maxillofacial surgery, bone transplantation is needed for treatment of bony defects. An autograft, allograft or biomaterial can be used. Autogenous bone grafts are considered to be the best materials available, but there are some disadvantages in their use including donorsite morbidity, need for a second operative site and limited graft supply. A search for new bone-graft materials therefore remains necessary. We prepared a mixture of tricalcium phosphate (TCP), which is a resorbable, non-toxic, osteoconductive ceramic material and epsilon-caprolactone-lactide copolymer P(epsilon-CL/DL-LA), a resorbable polymer, and placed it in the dermis and in mandibular bone defects in 13 rabbits. Follow-up times were two, three, seven, eight, 12, 15 and 18 weeks, tissue reactions were assessed, histologically and immunohistochemically. Times of resorption of the material from tissues were reported. We found that the mixture caused a mild inflammatory reaction when placed in bone and severe inflammation when placed in dermis. No highly fluorescent layer of tenascin or fibronectin was found surrounding the implant area. The mixture was excellent to handle and very easy to place into bone defects. The results are promising and have led us to continue development of the mixture.

Journal Article↗

PubMed1997

Biocompatibility of solid poly (ortho ester).

In previous studies poly (ortho ester) (POE) has shown promise as a resorbable device, a hemostatic sealant and as a carrier for drugs in bone surgery. The aim of this study was to evaluate the tissue reactions of solid poly (ortho ester) implanted into both tibiae of 17 rabbits. One half of the rods were sterilized by gamma radiation and the other half by ethylene oxide. The follow-up times were from 1 week to 21 weeks, after which the animals were killed and the bony specimens examined histologically. The connective tissue samples were examined immunohistochemically in order to study the occurrences of two extracellular matrix glycoproteins, tenascin and fibronectin. The results showed that solid poly (ortho ester)s induce a moderate inflammatory reaction for 9 weeks. Tenascin and fibronectin were present in samples from 1 week up to 4 weeks. It was also found that gamma sterilized POE was resorbed at week 7 and ethylene oxide sterilized POE at week 13.

Journal Article↗