Cenk Balcik

Synthesis and mechanical properties of interpenetrating networks of polyhydroxybutyrate-co-hydroxyvalerate and polyhydroxyethyl methacrylate

Naturally occurring, biocompatible, and biodegradable polyhydroxybutyrate-co-hydroxyvalerate (PHBV), and synthetic, non-degrading polyhydroxyethylmethacrylate (PHEMA) membranes were prepared and their mechanical properties were studied. Their performances were compared with the interpenetrating networks (IPN) prepared by photopolymerization of HEMA in the presence of PHBV. The modulus of elasticity, failure stress and failure strain indicated that the IPNs are viscoelastic with properties closer to PHEMA but much stronger than PHEMA homopolymers. Incorporation of PHBV (7, 14 and 22% HV) affected the mechanical properties positively. Increasing the PHBV content increased the modulus of elasticity and failure stress nearly in all samples tested. PHBV (7, 14, and 22% HV, 300 mg) samples showed an approximately 17-30 fold increase in terms of modulus of elasticity and 7-10 fold increase in terms of failure stress. The scanning electron micrographs of the membranes showed that the PHEMA membranes are more porous than the PHBV membranes but the IPN structure displayed channels on the membrane surface indicating that HEMA polymerization was achieved by using the PHBV as a scaffold. With the use of the present technique, it is possible to synthesize supramolecular structures from molecules that are not compatible and miscible with each other.

Comparison of Fixation Stability of Resorbable Versus Titanium Plate and Screws in Mandibular Angle Fractures

PURPOSE The aim of this study was to compare the fixation reliability and stability of titanium and resorbable plates and screws by simulating chewing forces. MATERIALS AND METHODS Mandibular angle fractures in 11 sheep hemimandibles were fixed with 4-hole straight titanium plates and 2.0 x 7-mm titanium screws; in addition, 11 hemimandibles were fixed with 4-hole straight resorbable plates and 2.5 x 6-mm resorbable screws according to the Champy technique. The hemimandibles were mounted with a fixation device in a servohydraulic testing unit for compressive testing. Displacement values under 20, 60, 100, 120, 150, and 200 N; maximum displacements; and maximum forces that the model could resist before breakage were recorded and compared. RESULTS Significant differences were found between resorbable and titanium plates and screws at all forces (20, 60, 100, 120, 150, and 200 N) (P < .05). We found no statistically significant differences in the breaking force and maximum displacement values (displacement values at the breaking forces) between the groups. CONCLUSIONS The stability of mandibular angle fractures with titanium miniplates under simulated chewing forces was significantly higher than with the resorbable system. Metallic and resorbable fixation systems cannot be used interchangeably to treat mandibular angle fractures under similar loading conditions.

Effect of dietary selenium and vitamin E on the biomechanical properties of rabbit bones.

SummaryIt is generally agreed that combined deficiency of selenium and vitamin E leads to several abnormalities including Kashin-Beck disease which is an endemic and chronic degenerative osteoarthrosis. The abnormalities can be reversed by the administration of various forms of selenium and vitamin E.The present study was designed to investigate the effects of dietary selenium and vitamin E on bone tissue and on the biomechanical properties of bone. Young rabbits of both sexes were fed with either a selenium- and vitamin E-adequate diet (control group), or a selenium- and vitamin E-deficient diet or a selenium-excess diet. The selenium-deficient diet resulted in a significant decrease in plasma selenium level and the selenium-excess diet resulted in a significant increase in the plasma selenium level with respect to the corresponding control values (p<0.05). The diets did not affect the blood cell counts considerably but erythrocyte glutathione peroxidase activity increased (decreased) relatively when the plasma selenium level increased (decreased) (p<0.05). The light microscopic investigations of the bone tissues of the two experimental groups indicate that the findings of the present work are compatible with osteomalacia. The biomechanical properties of the bones from the three groups were determined experimentally with bending tests. Both the Se-and vitamin E-deficient diet and the Se-excess diet decreased the biomechanical strength of the bones significantly while the bones belonging to the control group always had the largest modulus of elasticity (p<0.05).

Effects of different mandibular fracture patterns on the stability of miniplate screw fixation in angle mandibular fractures

The aim of the present study was to evaluate the effects of horizontally favourable and unfavourable mandibular fracture patterns on the fixation stability of titanium plates and screws by simulating chewing forces. Favourable and unfavourable mandibular fractures on 22 sheep hemimandibles were fixed with 4-hole straight titanium plates and 2.0mm×7mm titanium screws according to the Champy technique. Hemimandibles were mounted with a fixation device in a servohydraulic testing unit for compressive testing. Displacement values under 20, 60, 100, 120, 150, 200N, maximum displacements, and maximum forces the model could resist before breakage were recorded and compared. The authors found no statistically significant differences between the groups for the displacement values in the force range 60-200N (60, 100, 120, 150 and 200N). Statistically significant differences for maximum displacement values (displacement values at the breaking forces) between the groups were found (P<0.05). There was no evidence for the need to apply different treatment modalities to mandibular fractures regardless of whether the factures are favourable or not.

The Shape of the Lumbar Vertebral Canal in Newborns

Study Design. This study used geometric measurement criteria to assess the incidence of a trefoil spinal canal configuration in neonates. Objectives. To examine the shape of the neonatal lumbar vertebral canal with regard to its shape and the incidence of trefoilness. Summary of Background Data. Many studies consider the trefoil canal to be a developmental feature. Because of a lack of neonatal samples it is still unknown whether some individuals are prone to develop a trefoil spinal canal because of genetically determined factors. Methods. The last two lumbar vertebrae of 31 term neonatal cadavers from the collection of the Anatomy Department of Ondokuz Mayis University were examined. After removal, the vertebrae were processed and embedded in paraffin blocks to enable accurate sectioning at the pedicle level. Subsequently, unmagnified images were obtained through a color photocopy machine. These two‐dimensional images were digitalized, and accurate measurements were made to determine the circularity and the trefoilness. Results. Trefoilness assessment indicated that the trefoil‐shaped spinal canal does not exist in newborns. The spinal canal at this age is mostly dome‐shaped. Conclusions. In accordance with the previous hypotheses made by other authors, the authors of this study found that the trefoil shape of the lumbar vertebra does not occur at the end of the intrauterine period.

Comparison of repair techniques in small and medium-sized rotator cuff tears in cadaveric sheep shoulders

OBJECTIVE The aim of this study was to compare new knotless single-row and double-row suture anchor techniques with traditional transosseous suture techniques for different sized rotator cuff tears in an animal model. METHODS The study included 56 cadaveric sheep shoulders. Supraspinatus cuff tears of 1 cm repaired with new knotless single-row suture anchor technique and supraspinatus and infraspinatus rotator cuff tears of 3 cm repaired with double-row suture anchor technique were compared to traditional transosseous suture techniques and control groups. The repaired tendons were loaded with 5 mm/min static velocity with 2.5 kgN load cell in Instron 8874 machine until the repair failure. RESULTS The 1 cm transosseous group was statistically superior to 1 cm control group (p=0.021, p<0.05) and the 3 cm SpeedBridge group was statistically superior to the 1 cm SpeedFix group (p=0.012, p<0.05). The differences between the other groups were not statistically significant. CONCLUSION No significant difference was found between the new knotless suture anchor techniques and traditional transosseous suture techniques.

Effect of static magnetic field on experimental dermal wound strength.

Context: An animal model. Aim: We sought to evaluate the effect of static magnetic fields on cutaneous wound healing. Materials and Methods: Male Wistar rats were used. Wounds were created on the backs of all rats. Forty of these animals (M group) had NeFeB magnets placed in contact with the incisions, either parallel (Pa) and perpendicular (Pr) to the incision. The other 40 animals (sham [S] group) had nonmagnetized NeFeB bars placed in the same directions as the implanted animals. Half of the animals in each group were killed and assessed for healing on postoperative day 7 and the other half on postoperative day 14. The following assessments were done: gross healing, mechanical strength, and histopathology. Statistical Analysis Used: Intergroup differences were compared by using the Mann-Whitney U or t test. Values for P less than 0.05 were accepted as significant. Results and Conclusions: There were no differences between the magnetic and sham animals with respect to gross healing parameters. The mechanical strength was different between groups. On postoperative day 14, the MPr14 had significantly higher scores than the other groups. When static, high-power, magnetic fields are placed perpendicular to the wound, increased wound healing occurs in the skin of the experimental model.

The effects of extracorporeal shock waves on carrageenan-induced Achilles tendinitis in rats: a biomechanical and histological analysis

OBJECTIVE The aim of this study was to investigate the influence of low-dose extracorporeal shock waves (ESW) on the healing potential of Achilles tendinitis in the rat. METHODS The 36 adult Sprague-Dawley rats used in this study were randomly divided into four groups. Group A (n=10) were injected with carrageenan, Group B (n=10) were injected with carrageenan and received ESW, Group C (n=10) received ESW only, and Group D (n=6) was a sham group. Rats were injected with 10 microliters of 3% carrageenan or a saline solution eight times during a one-week period with a subcutaneous needle. One week following the final injection, ESW was applied at a rate of 500 impulses in 5 minutes at 2 bars (comparative to 0.09 mJ/mm²) to rats in Groups B and C. Rats were sacrificed three weeks later. Tensile strength, inflammation, and vascularity and collagen density were measured. RESULTS Failure of the tendon ultimate loads was significantly lower in the study groups than in the control group (p<0.05). Collagen fiber density was higher in the control group than in the other groups (p=0.59). No other histological differences were found. CONCLUSION Low-dose ESW has a negative effect on tendon tensile strength in this animal model.