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Biomedical subjects

R Suuronen

Publications and source records attributed to R Suuronen.

At least 37 records · Page 2Linked to original sources
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

Fixation of mandibular body osteotomies using biodegradable amorphous self-reinforced (70L:30DL) polylactide or metal lag screws: an experimental study in sheep.

Mandibular body osteotomies were fixed in nine sheep using new totally amorphous (70L:30DL), self-reinforced, polylactide (SR-PLA) lag screws and in nine sheep using standard stainless steel lag screws. No intermaxillary fixation was used. During follow-up, radiological, histological and microradiological studies were undertaken at 3, 6, 12 and 24 weeks. In both groups, all osteotomies consolidated at similar rates and no adverse reaction to the screws was seen. However, displacements of the fixed osteotomy fragments were common in both groups during the first 3 weeks. The biocompatibility of SR-PLA during the follow-up period was found to be good. Only initial signs of biodegradation were seen. The results of this study indicate that (70L:30DL) SR-PLA has potential for use as a fixation screw material in oral and maxillofacial surgery, and that further studies using this material are justified.

Absorbable Implants↗
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↗
PubMed1999

Update on bioresorbable plates in maxillofacial surgery.

Biodegradable materials, mainly polymers and copolymers of polylactide and polyglycolide, are today routinely used as fixation materials in craniomaxillofacial surgery. Several research groups have shown that these materials can adequately fix osteotomies and fractures of the craniofacial skeleton. Although there are some differences between polymers, in general their biocompatibility is good. They gradually lose their strength, enabling the underlying bone to take up the stress. Secondary procedures for removal of the material causing discomfort and pain are not needed. An overview of the development of biodegradable materials, their characteristics, and illustrations of different applications in craniomaxillofacial surgery are presented. More than 200 patients have been treated successfully so far in our units, the longest follow-up time being now over 7 years. The good results indicate that the use of bioresorbable fixation can be considered routine and will be definitely state of art at the beginning of the new millennium.

Absorbable Implants↗
PubMed1999

Osteotomy site healing following mandibular sagittal split osteotomy and rigid fixation with polylactide biodegradable screws.

Follow-up of 47 patients, treated using mandibular bilateral sagittal split osteotomy and self-reinforced poly-L-lactide acid (SR-PLLA) screws for rigid internal fixation, is presented. The focus was on clinical and radiological osteotomy healing. The average follow-up time was 2.1 years (range 0.5-5 years). Clinical recovery and radiological osteotomy healing during follow-up were uneventful. Osteolytic changes were seen around the SR-PLLA screws in 27% of cases. The majority of the screw canals remained as radiolucent shadows without bony filling.

Absorbable Implants↗
PubMed1998

A 5-year in vitro and in vivo study of the biodegradation of polylactide plates.

PURPOSE: The purpose of this study was to investigate the long-term tissue response and duration of degradation of self-reinforced poly-L-lactide (SR-PLLA) multilayer plates in vivo. MATERIALS AND METHODS: Mandibular osteotomies in sheep were fixed with SR-PLLA multilayer plates. The animals were followed for 1, 2, 3, 4, and 5 years, after which histologic studies were performed. RESULTS: The foreign-body reaction was mainly mild, and the osteotomies were well united. After 5 years in vivo, the material was almost completely resorbed, but small particles of polymer could still be detected at the implantation site. SR-PLLA plates were also incubated in vitro for 5 years. The material degraded considerably faster in vivo than in vitro. Molecular weight, melting temperature, and crystallinity of the plates remained at a constant level after 2 years in vitro, indicating very slow degradation of the oligomeric (molecular weight [Mw], 3500 daltons), highly crystalline (heat of fusion, 70 J/g), PLLA residue solely as a result of hydrolysis. Although the plates became increasingly fragile as they degraded, they retained their macroscopic form until the end of the 5-year follow-up. Loss of mass of the plates was 52%+/-8% after 5 years of incubation in vitro. CONCLUSIONS: Although the long degradation period may seem to be a minor drawback to the use of such plates, it does not appear to affect the healing process.

Absorption↗
PubMed1998

Skeletal stability following mandibular advancement and rigid fixation with polylactide biodegradable screws.

Skeletal stability during the first year after mandibular advancement surgery and fixation using biodegradable self-reinforced poly-l-lactide (SR-PLLA) screws, without postoperative intermaxillary fixation, was studied in 25 patients by means of cephalometric measurements. The magnitude of advancement was on average, 3.88 mm at pogonion (PG) (range 1.25-6.5 mm) and 4.57 mm at B-point (range 2.75-7.5 mm). After one year a mean relapse backwards of 0.59 mm at the PG (15%) and 0.78 mm at the B-point (17%) was observed. Nineteen patients (76%) and 17 patients (68%) were stable at PG and B-point, respectively. SR-PLLA screws are considered to be comparable to other forms of rigid internal fixation for fixation of bilateral splitting osteotomies after mandibular advancement, as far as skeletal stability is concerned.

Absorption↗
PubMed1998

Biodegradable polylactide plates and screws in orthognathic surgery: technical note.

In orthognathic surgery, the bone fragments are usually fixed with metallic plates and screws. Metallic devices other than titanium plates are usually removed after the osteotomy has consolidated, which often requires general anaesthesia. Titanium plates, supposed to be biotolerable, have been introduced in order to overcome this need for secondary intervention. However, due to corrosion, titanium particles have been found in scar tissue covering these plates and in locoregional lymph nodes. Therefore, their removal is also advocated. Self-reinforced poly (L-lactide) homopolymer (PLLA) and poly (L/D-lactide) stereocopolymers with a L/D molar ratio up to 85/15 have sufficient strength to overcome the need for additional support for the fixation of fractures. The plates can be bent at room temperature. The surgical technique and early results of a case of bimaxillary surgery and genioplasty fixed with bioresorbable material without postoperative rigid maxillomandibular fixation are reported.

Absorption↗
PubMed1998

Fibrous wound repair associated with biodegradable poly-L/D-lactide copolymer implants: study of the expression of tenascin and cellular fibronectin.

Extracellular matrix (ECM) proteins are known to play a role in inflammatory and hyperplastic processes. Our aim in the present study was to study the distribution of tenascin (Tn), cellular fibronectins (cFn) and myofibroblasts around biodegradable poly-L/D-lactide (PLA) implants with monoclonal antibodies (MAb). Ethylene-oxide and gamma-irradiation sterilized PLA plate-type implants were inserted into the dorsal subcutaneous tissue of ten adult rabbits. Follow-up times were 4, 12, 16, 36 and 48 wk. Only some inflammatory cells were observed. In electron microscopy, a close coherence between the implant and the stromal tissue was seen. Immunoreactivity for Tn, cFn and alpha-actin was detected as a distinct layer bordering the implant, regardless of the sterilization method for the first 36 wk. From week 36 onwards, Tn immunoreactivity was downregulated while cFn immunoreactivity still persisted. A moderate upregulation for myofibroblasts was seen on the week 48 specimens, when hydrolysation of PLA implant had started. The persistent content of myofibroblasts, Tn and cFn suggests a prolonged wound healing produced by PLA implants. The absence of Tn at the week 48 specimens suggests that cFn, rather than Tn may be needed for alpha-actin-mediated contraction by myofibroblasts.

Journal Article↗
PubMed1997

Mandibular osteotomy fixed with biodegradable plates and screws: an animal study.

The objective of the study was to evaluate the use of a totally biodegradable fixation device in the fixation of mandibular osteotomy in sheep. Mandibular unilateral body osteotomies were fixed with biodegradable self-reinforced poly-L-lactide (SR-PLLA) multi-layer plates and screws in nine sheep. The unoperated sides acted as control. The follow-up times were 6, 12 and 24 weeks, after which radiological, mechanical and histological studies were carried out. An analysis of the implanted material was also carried out. The results showed that the SR-PLLA plates and screws were strong enough to fix the osteotomy and that the osteotomies healed mainly with callus formation. Therefore we conclude that SR-PLLA multi-layer plates and screws can be used together successfully in the fixation of mandibular osteotomies without maxillomandibular fixation. However, before they can be used in humans, the size of the plate and screws should be decreased.

Animals↗
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↗
PubMed1994

Sagittal ramus osteotomies fixed with biodegradable screws: a preliminary report.

Nine patients underwent bilateral sagittal split osteotomies of the mandible. The osteotomies were fixed using two self-reinforced poly-L-lactide screws. No maxillomandibular fixation was used postoperatively. The preliminary results with the shortest follow-up of 15 months show that primary healing was normal. No late-term clinical complications were encountered during the follow-up, the longest of which is now 23 months.

Adult↗
PubMed1994

The effect of osteotomy and osteosynthesis in the mandibular condyle. A radiologic and histologic study in sheep.

Eighteen oblique osteotomies in sheep mandibular condylar necks were fixed with self-reinforced poly-L-lactide (SR-PLLA) (n = 9) or stainless steel (n = 9) screws (core diameters 2.4, 2.7, 3.0, or 3.5 mm). No intermaxillary fixation (IMF) was applied. The follow-up periods were 6, 12, and 24 weeks, respectively, after which the sheep were killed, and the status of the condylar head was assessed radiographically and histologically. The results showed that the fixation had been adequate. Bony destruction, osteophytes, and flattening of the condylar head, however, were frequently observed in both groups, as compared with the unoperated contralateral condyle. Histologic studies revealed that the thickness of the condylar head cartilage had increased and that the boundaries of the different cell layers were irregular, as was the junction of cartilage and bone. The diameter of the screw did not seem to have any influence on the occurrence of either radiologic or histologic signs of condylar degeneration. These findings indicate that screw fixation of condylar fractures in the mandible without IMF might result in degenerative joint disease.

Animals↗
PubMed1992

New generation biodegradable plate for fracture fixation: comparison of bending strengths of mandibular osteotomies fixed with absorbable self-reinforced multi-layer poly-l-lactide plates and metallic plates--an experimental study in sheep.

Eighteen osteotomies of sheep's mandibular corpus were fixed: nine with self-reinforced multi-layer poly-l-lactide (SR-PLLA) plates and nine with metallic plates. Both plates were fixed with similar metallic screws. The right corpus of each sheep acted as a control. Radiographic analysis was carried out at 3 weeks and at sacrifice (6, 12 or 24 weeks) when the bending force needed to break the osteotomy site was measured. At 6 and 12 weeks of follow-up the osteotomy fixed with the PLA-plate seemed to tolerate the bending force better but no significant differences were detected at 3 or 24 weeks. The results have been satisfactory and have led the authors to continue with the development of a SR-PLLA plate-and-screw device for fracture fixation.

Absorption↗
PubMed1992

Comparison of absorbable self-reinforced multilayer poly-l-lactide and metallic plates for the fixation of mandibular body osteotomies: an experimental study in sheep.

Eighteen unfavorable transverse osteotomies were created in the mandibular body of sheep. Nine were fixed with self-reinforced poly-l-lactide and nine with metallic dynamic compression plates. Both plates were fixed with similar titanium screws. The follow-up times for radiographic, histologic, and microradiographic studies were 6, 12, and 24 weeks. With both methods, bony union with callus formation was accomplished by 6 weeks in all but one osteotomy in the metallic fixation group. There were no signs of plate failure.

Animals↗
PubMed1992

Sagittal split osteotomy fixed with biodegradable, self-reinforced poly-L-lactide screws. A pilot study in sheep.

Self-reinforced poly-L-lactide (SR-PLLA) screws were used to fix bilateral mandibular sagittal split osteotomies (SSO) in six sheep. No intermaxillary fixation was used postoperatively. The follow-up time was 16 weeks, after which the sheep were killed. Both sides of the mandible were photographed and radiographed. The bending strength of the osteotomy was measured on the left side of the mandible. Histological and microradiographic studies were performed on the right side of the mandible. The results showed that the SR-PLLA screws were strong enough to fix the SSO rigidly. The bending force needed to break the bone was greater than that for the average unoperated mandible. The histological and microradiographic studies showed uneventful healing of the osteotomies in all six sheep. The results indicate that this method should be suitable for rigid fixation of SSO and fractures of the mandible in human beings.

Animals↗
PubMed1992

Polylactide screws in the fixation of olecranon osteotomies. A mechanical study in sheep.

We studied absorbable self-reinforced poly-L-lactide screws in the fixation of osteotomies in sheep. A left olecranon osteotomy in 10 sheep was fixed with polylactide screws and in an additional 10 sheep with metallic AO cortical screws. Follow-up times were 6 and 12 weeks. 8 polylactide fixations healed and 2 failed. All metal fixations united; one of them had a fracture of the proximal fragment resulting in malposition. After killing the sheep the olecranons were radiographed and the shear strengths of the osteotomies were compared with those of the non-operated contralateral bones. After 6 weeks the mean comparative strength was 74 percent in the polylactide group and 83 percent in the metallic control group. After 12 weeks the corresponding values were 112 and 47 percent (P less than 0.05). Our study demonstrated that the mechanical weakening of fixed bone can be avoided by using absorbable polylactide screws instead of metallic screws. However, polylactide screws are not recommended for use without external support in places of high mechanical strain.

Animals↗