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Biomedical subjects

J F Lontz

Publications and source records attributed to J F Lontz.

12 recordsLinked to original sources
PubMed1998

Human ejaculate. Effects on the biomechanical properties of the human chorioamniotic membranes.

OBJECTIVE: To determine the effects of human ejaculate on the biomechanical properties of the human chorioamniotic membranes. STUDY DESIGN: Equivalent strips of chorioamniotic membranes were obtained from 30 term, uncomplicated pregnancies immediately after delivery and incubated for 0, 1 and 24 hours with either ejaculate or pseudoamniotic fluid. Three biomechanical properties--rupture tension, strain to rupture and work to rupture--were compared. RESULTS: One hour of incubation with pseudoamniotic fluid alone did not significantly change the membrane biomechanical parameters, but these parameters were reduced after one hour of exposure to ejaculate (P < .05). Twenty-four hours of incubation decreased all three properties in both the ejaculate and control groups without any significant difference between the two groups. CONCLUSION: In vitro exposure to human ejaculate for one hour significantly weakens the human chorioamniotic membranes.

Amnion↗
PubMed1998

Efficacy of fibrin glue for in vitro sealing of human chorioamniotic membranes.

OBJECTIVE: To assess the changes in tensile strength properties of artificially punctured chorioamniotic membranes after sealing the defect with fibrin glue, a tissue sealant. STUDY DESIGN: Chorioamniotic membranes were obtained from 30 term, uncomplicated pregnancies immediately after delivery. Adjacent, same-sized strips were cut from each membrane sample. After baseline tensile strength properties were obtained, identical size holes were made on each strip, and fibrin glue was applied onto half the specimens. Following adequate stabilization of fibrin, tensile strength properties--rupture tension, strain to rupture and work to rupture--were measured. RESULTS: Membrane puncture decreased the tensile strength characteristics, indicating weakening of the chorioamniotic membranes: Rupture tension (g/cm) dropped from 153.1 +/- 12.3 to 76.8 +/- 15.7; strain to rupture (%) from 193.9 +/- 29.9 to 152.6 +/- 36.8; and work to rupture (g x cm) from 560.8 +/- 51.8 to 239.0 +/- 65.5 (P < .05). Significant increases were noted in rupture tension (116.0 +/- 19.6), strain to rupture (173.5 +/- 30.8) and work to rupture (394.3 +/- 91.3) after application of fibrin glue; however, all three measurements remained less than prepuncture values (P < .05). CONCLUSION: Fibrin glue effectively improved the structural integrity of artificially punctured chorioamniotic membranes.

Amnion↗
PubMed1995

Laser-assisted fibrin clot soldering of human menisci.

Fibrin mixtures have been used as a solder in conjunction with argon ion lasers to create strong tissue welds in several organ systems. An analogous method of meniscus repair could obviate the need for partial meniscectomy and its subsequent degenerative effects in a subset of meniscal tears. This study measured the in vitro tensile strength in 4 groups of human menisci (1-mm x 2-mm x 5-mm sections): (1) bisected menisci repaired with fibrin clot mixture, (2) bisected menisci bonded by fibrin clot mixture and exposure to argon laser energy (energy density, 60 W/cm2), (3) bisected menisci repaired with 2 interrupted sutures, and (4) untreated meniscal controls. After irradiation with argon ion laser energy, the tensile strength of the laser-assisted fibrin clot-bonded menisci increased 40-fold over that of nonirradiated fibrin clot-bonded menisci. Suture controls (0.515 +/- 0.221 MPa) had a higher tensile strength than the fibrin clot mixture and irradiated groups; however, the suture controls had only 8.5% the strength of native menisci (6.081 +/- 0.221 MPa). Laser-assisted fibrin clot soldering may allow the opposing edges of a meniscal tear to be held together with a biologic scaffold, possibly inducing reparative cell migration and proliferation.

Combined Modality Therapy↗
PubMed1992

The effects of laser-assisted fibrinogen bonding on suture material.

To evaluate the effect of laser-assisted fibrinogen bonding on the tensile strength of suture material, 10 types of sutures were exposed to various time intervals of diode laser energy after pretreatment with dye-enhanced fibrinogen solder. After exposure, each suture material was stressed on a tensometer and compared with nonlased suture material. Our results indicate that polytetrafluoroethylene suture material was virtually unaffected at all time intervals of exposure to laser energy. Polyester suture material retained 64.3% of its tensile strength at 60 sec of exposure to laser energy. White silk suture material maintained 80% of its initial tensile strength at 60 sec of exposure. These suture materials may be used safely in conjunction with laser-assisted fibrinogen bonding even if prolonged laser exposure is necessary. The other suture materials tested may be compromised significantly by prolonged exposure to laser energy and must be used with relatively shorter irradiation periods.

Biocompatible Materials↗
PubMed1992

Comparison of laser-assisted fibrinogen-bonded and sutured canine arteriovenous anastomoses.

The effect of laser-assisted fibrinogen bonding (LAFB) on the development of intimal hyperplasia was studied with stress-strain profiles and histologic evaluation of canine arteriovenous fistulas (AVFs). In 19 animals femoral AVFs were created with an 808 nm diode laser after topical application of fibrinogen mixed with indocyanine green dye; in the contralateral limb a sutured AVF was created. The animals were divided into three groups. Group 1 dogs (n = 6) were killed serially up to 4 weeks after surgery to examine the healing of the anastomoses created with LAFB. Group 2 dogs (n = 6) were killed 1 month after surgery, and the fresh specimens were strained axially to produce a stress-strain profile graph. Group 3 dogs (n = 7) were killed 7 months after surgery, and the AVFs were infused with formalin under pressure and histologically prepared to allow comparison of the ratio of maximum to minimum intimal hypertrophy. Fibrinogen used for LAFB was resorbed during the first month after operation without evidence of foreign body reaction or inflammation. Tensile break force was not significantly different in the laser-bonded group (4.6 +/- 2.4 pounds) and the sutured group (4.3 +/- 1.7 pounds). The modulus (tensile break force per square inch), a measure of elasticity, identified the laser-bonded AVF (149 +/- 44 pounds per square inch) to be less rigid than the sutured AVF (203 +/- 35 pounds per square inch) (p less than 0.05). No significant differences in the degree of intimal hyperplasia were noted in any area of the anastomoses. Use of LAFB neither accelerates nor prevents intimal hyperplasia in a canine AVF model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Laser-assisted fibrinogen bonding of vascular tissue.

Characterization of the stress-strain profiles of welded tissue would provide an additional means of analyzing this new technology and comparing it with alternative anastomosing techniques. Rabbit longitudinal aortotomies were repaired with either 7-O polypropylene sutures or an 808-nm diode laser (power density, 4.8 watts/cm2) after topical application of fibrinogen mixed with indocyanine green dye (peak absorption, 805 nm). The rabbits were sacrificed between 0 and 28 days, and the fresh aortic specimens were strained axially in diluted plasma solution until ultimate breakage occurred in order to produce a stress-strain profile graph. No significant differences were noted between sutured and bonded aorta at any time interval. Nonincised aortic tissue (378 lb/in2) withstood significantly higher stress (P less than 0.05) than both sutured (257 lb/in2) and bonded (210 lb/in2) groups at the time of creation. By 7 days after operation, however, no significant differences were noted among any of the three groups. At 28 days after operation, the laser-bonded aorta was significantly stronger than the control aorta (P less than 0.05). The only significant difference in modulus (stretchability) identified the sutured aorta (373 lb/in2) to be more rigid than the control aorta (231 lb/in2) (P less than 0.05). Both sutured and laser-bonded anastomoses are weaker than control aorta initially; however, after an early critical period, both treatments achieve the strength of control aorta. By 1 month postoperatively, sutured anastomoses have the disadvantage of being less distensible.

Animals↗
PubMed1990

State-of-the-art materials used for maxillofacial prosthetic reconstruction.

The present state-of-the-art rests primarily on three general types of polymeric materials based on chemical configurations, that of polyacrylates, polydimethylsiloxane, and segmented block polyetherurethanes. Each of these types is currently prominent in a wide range of dental prosthodontics and surgical prosthetics with continued chemical variants emerging to attain enhanced biocompatibility for safety and effectiveness. However, owing to the disproportionally lower demand, the state-of-the-art for maxillofacial restorative prosthetics has not focused adequately on the specific array of the properties needed for the ideal prosthesis. To approach the ideality will require synthesizing new molecular configurations adjusted with component structures either as block copolymers or as intermediate oligomers. The synthetic effects must have a comprehensive plan of immediate assessments on terms of biocompatibility for safety to orofacial tissues and effective durability against all conceivable deterioration of the chemical structure. Above all, inasmuch as the skilled art and techniques of maxillofacial prosthetics is a custom-made specialty allied to the prosthodontics, the improved material for ideality should be readily amenable to molding by the well-established dental stone mold technology, for reasons of cost and simplicity.

Biocompatible Materials↗
PubMed1986

Materials and their specifications for vascular prostheses. Specifications and performance standards.

Specification and performance standards represent distinctly different criteria for safe and effective cardiovascular materials and devices, in distinct areas of materials and device conversions, with consideration of implant as well as physiological assault. Cardiovascular device failures need more definitive, realistic, and creative approaches to devising standards of performance with relevance to the physiological environment.

Biocompatible Materials↗