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At least 343 records · Page 19Linked to original sources

PubMed2003

[Investigation of biocompatibility of the apatite cement].

The results of experimental studies of biocompatibility of the apatite cement, implanted in the muscular tissue of rats and bone tissue of rabbits were presented in this study. Investigations of the local reactions of the muscular tissue were carried out on 18 rats of Wistar type by implanting samples from the apatite cement in the dorsal muscles. Macroscopic and microscopic investigations were carried out 7, 14, 30, 180, 270 days after the implantation. Investigations of local reactions of bone tissue were carried out on 12 rabbits of New Zealand breed. By implanting the tested material into the femoral bone in the region of trochanter. Sections of the animals were made 1, 3, 6, and 9 months after the surgery. In the early period active inflammatory process was seen in the muscles in the direct vicinity of the implant and then it disappeared leading to formation of a thin fibrous connective tissue capsule. Histological investigations made of bone tissue later showed, formation of young tissue with small focuses of fibrous connective tissue. In the carried out investigations it was shown that the apatite cement is characterized with a high degree of biocompatibility and osteoinductive activity.

Animals↗

PubMed2003

[Investigation of tissue reaction of apatite cement implants impregnated with vancomycin].

Investigation of biocompatibility degree of apatite cement as a carrier of antibiotic--vancomycin was the purpose of the experimental study. Investigation of local reactions of muscular tissue was carried out on 18 rats of Wistar type, by implanting samples of apatite cement with vancomycin in the dorsal muscles. Sections of the animals and microscopic investigations were made 7, 14, 30, 90, 180 and 270 days after the implantation. Investigation of local reactions of bone tissue were carried out on 12 rabbits of New Zealand breed, by implanting the investigated samples into the femoral bone in the region of trochanter. Macroscopic, radiological and microscopic investigations were carried out 1, 3, 6 and 9 months after the surgery. The obtained results of the investigations from muscular and bone tissue, were compared to the investigations in analogical tissues of apatite cement without the medication. In macro- and microscopic investigations in the early period inflammatory reaction of muscles was noticed to be stronger around the samples with vancomycin, in comparison to the control implant. In the later period there was no inflammatory reaction and a thin fibrous connective tissue surrounded the implant and a histological picture was similar, as in cases of an implant without the antibiotic. The local reaction of bone tissue both in the control and in the investigated group (apatite cement with vancomycin) was similar. In the early period the proliferation of rich cellular connective tissue, was noticed. In the later period starting from the 3rd month, formation of young bone tissue was noticed and only locally there were focuses of fibrous tissue. The process observed after splitting of the tested materials into bone tissue, was very similar to healing processes after long bone fraction. The carried out investigations showed, that tissue reaction after implantation of apatite cement and its composite with vancomycin, was very similar and showed a high degree of tissue biocompatibility.

Animals↗

PubMed2004

In vitro buffering properties of 3 composite resins.

AIM: A dental composite resin, Ariston pHc, has been described as having a cariostatic effect by buffering acid saliva and preventing decalcification and infiltration of restorations. The buffering effect has been reported due to the release of OH- originated from the alkaline glass embedded in the resin. The release would occur only in the presence of low salivary pH values. The aim of this in vitro investigation was to evaluate pH variations induced by Ariston pHc and 2 other composite resins (P60 and Z100). METHODS: Eighteen samples were prepared for each composite and 5 specimens of each brand were embedded in artificial saliva according to Brugirar and Mazille, at 3 different pH values. A 1(st) group of 5 specimens of each tested resin was immersed in neutral artificial saliva at pH 7.7, a 2(nd) group in acidified artificial saliva at pH 5.45 and a 3(rd) group in alkalised saliva at pH 9.25. Three other samples of each resin were immersed in tubes containing distilled water at pH 7.23 and served as controls. Twelve tubes were filled only with neutral, alkalised and acidified artificial saliva and distilled water at the above mentioned pH values. Measurements of pH modifications were taken after 1, 3, 9, 14, 31 days. RESULTS. Ariston pHc raised the pH of distilled water up to 9.59 after 1 day, and to 8.42 after 31 days. This pH modification shown by Ariston pHc in distilled water, compared to those of the other 2 composites were statistically highly significant, with p<0.001, while the pH variations of saliva containing the 3 resins were negligible, except for acidified saliva with Ariston pHc, where a slight pH enhancement with some statistical significance (p=0.04) was found. However, acidified saliva without any resin embedded was found to shift to neutrality as well. CONCLUSION: These results strongly suggest that none of the 3 tested materials can achieve an effective buffering action in vitro on low salivary pH values. However, the ability of Ariston pHc to raise the pH in distilled water, and to a lesser degree in acidified saliva, suggests that an in vivo buffering effect cannot be excluded.

Buffers↗

PubMedDate not supplied

Gas chromatographic/mass spectrometric determination of 3-methoxy-1,2-propanediol and cyclic diglycerols, by-products of technical glycerol, in wine: interlaboratory study.

The aim of the present study was to provide the official wine control authorities with an internationally validated method for the determination of 3-methoxy-1,2-propanediol (3-MPD) and cyclic diglycerols (CycDs)-both of which are recognized as impurities of technical glycerol-in different types of wine. Because glycerol gives a sweet flavor to wine and contributes to its full-body taste, an economic incentive is to add glycerol to a wine to mask its poor quality. Furthermore, it is known that glycerol, depending on whether it is produced from triglycerides or petrochemicals, may contain considerable amounts of 3-MPD in the first case or CycDs in the second. However, because these compounds are not natural wine components, it is possible to detect glycerol added to wine illegally by determining the above-mentioned by-products. To this end, one of the published methods was adopted, modified, and tested in a collaborative study. The method is based on gas chromatographic/mass spectrometric analysis of diethyl ether extracts after salting out with potassium carbonate. The interlaboratory study for the determination of 3-MPD and CycDs in wine was performed in 11 laboratories in 4 countries. Wine samples were prepared and sent to participants as 5 blind duplicate test materials and 1 single test material. The concentrations covered ranges of 0.1-0.8 mg/L for 3-MPD and 0.5-1.5 mg/L for CycDs. The precision of the method was within the range predicted by the Horwitz equation. HORRAT values obtained for 3-MPD ranged from 0.8 to 1.7, and those obtained for CycDs ranged from 0.9 to 1.3. Average recoveries were 104 and 109%, respectively.

Diglycerides↗

PubMed2005

[Biomechanical evaluation of stiffness of long-segment instrumented spine].

OBJECTIVE: To test the changes of the stiffness of the intact, released, and instrumented spines in an in vitro porcine model. METHODS: Twelve porcine spines (12 segments each) were harvested for the biomechanical tests with Material Test System. Stiffness during flexion, extension, lateral bending, and axial rotation were recorded; then the specimen was released with intervertebral discs and the facet joints removed, followed by repeating the biomechanical tests for stiffness; and finally, a double-rod titanium construct was applied for internal fixation to each released spine and stiffness tests were repeated again. RESULTS: Compared with the intact porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 52.89 +/- 15.98, 105.43 +/- 56.38, 42.09 +/- 14.73, and (16.94 +/- 4.85) N x mm/degrees, respectively], the stiffness of the released porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 44.04 +/- 13.73, 41.46 +/- 10.80, 31.75 +/- 7.23, and (9.10 +/- 2.07)N x mm/degrees, respectively] significantly decreased (P < 0.05), while significantly increased stiffness was found in the instrumented porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 385.96 +/- 143.25, 138.96 +/- 59.41, 152.56 +/- 87.15, and (55.91 +/- 16.49) N x mm/degrees, respectively] (P < 0.05). CONCLUSION: Higher instant stiffness was found in instrumented spine than the intact one during flexion, extension, lateral bending and axial rotation.

Animals↗

PubMed1992

A new, compound-curved needle for vascular surgery.

A new, compound-curved needle has been designed and developed for vascular surgery from a unique stainless steel alloy, American Society for Testing Materials (ASTM) 45500. This needle has two different radii of curvature and a relatively straight body followed by a short, curved tapered point. Despite its geometry, it exhibits a similar sharpness, as well as resistance to bending and breakage, as did a curved needle with a single radius of curvature manufactured from the same alloy. The design of this new needle enabled the surgeon to pass it through the vessel wall with greater accuracy to a controlled depth and length of bite than the curved cutting edge needle with a single radius of curvature.

Biomechanical Phenomena↗

PubMedDate not supplied

Shear bond strength of pit-and-fissure sealants to saliva-contaminated and noncontaminated enamel.

PURPOSE: The purpose of this study was to investigate the shear bond strength of 2 resin-based pit-and-fissure sealants--Clinpro and Fluroshield--to saliva-contaminated and noncontaminated enamel. METHODS: Forty buccal halves of permanent molar crowns were individually embedded in polyester resin and ground with wet silicone carbide papers to obtain flat enamel surfaces. The specimens were randomly assigned to 2 groups: (A) without contamination; and (B) contaminated with 0.01 ml of fresh human saliva. Each group was divided into 2 subgroups (N=10), according to the sealant applied: (1) Clinpro; and (2) Fluroshield. Shear bond strength was tested at a crosshead speed of 0.5 mm/min. Failure mode was assessed. RESULTS: Means (MPa) were: (1) A1=7.66 +/- 3.12; A2=12.39 +/- 4.34; (2) B1=5.05 +/- 1.44; B2=10.44 +/- 2.35. Data were submitted to analysis of variance and Scheffé's statistical test (P<.05). There was a statistically significant difference (P<.05) between both the sealants and the experimental conditions analyzed. Fluroshield provided higher bond strength and was different from Clinpro (P<.05) in the absence of contamination. Within the saliva-contaminated group, however, no statistically significant difference (P>.05) was observed between the tested materials. CONCLUSIONS: It may be concluded that, under dry conditions, the filled pit-and-fissure sealant (Fluroshield) yielded better bonding performance. Salivary contamination undermined the adhesion of both materials to enamel and resulted in lower bond strengths.

Analysis of Variance↗

PubMed1991

Color stability of restorative resins.

The purpose of the present study was to evaluate the color stability of selected indirect composite resins. Twenty-six specimens each of Dentacolor, VisioGem, Brilliant D. I., and Concept were fabricated and immersed in chlorhexidine, coffee, and tea. The modifying effect of saliva on staining was also studied. Coffee and tea both stained the tested materials, but tea stained more than coffee. The addition of chlorhexidine and saliva increased staining when used with tea. Most staining was superficial and could be removed with regular oral hygiene; however, residual staining, which might become cumulative, was recorded. Brilliant D. I. samples exhibited the most discoloration and Concept samples the least.

Chlorhexidine↗

PubMed1987

Biomechanical effects of point configuration in Kirschner-wire fixation.

The drilling and bone holding properties of Kirschner wires of three different tip designs have been investigated. The tip designs studied were the commercially available trocar- and diamond-shaped tips and the homemade cut tip produced by cutting the pin obliquely with wire cutters. Thirteen canine metacarpals were drilled with wires of each tip design at 400 and 800 rpm. A servohydraulic test machine (Materials Test Systems, Minneapolis, MN) simultaneously measured axial loads, torque, and displacement during insertion and pull-out. Kirschner wires of each tip configuration were also placed in seven canine metacarpals for a three-week in vivo test. After the animals were killed, peak pull-out forces were measured and compared with in vitro results. The trochar-tipped wire displayed the highest required torque and axial load to penetrate bone. It also demonstrated the highest pull-out force immediately after drilling, especially when inserted at the low drill speed. After placement for three weeks, pull-out force of the diamond-tipped wire equaled the trochar. The homemade cut wire consistently yielded inferior holding properties. For immediate and sustained strong fixation in bone, a wire with a trochar tip configuration should be inserted at low drill speeds.

Animals↗

PubMedDate not supplied

Effect of surface finish on the flexural strength of feldspathic and aluminous dental ceramics.

The effects of surface finish on flexural strength of a feldspathic porcelain, aluminous porcelain, and a computer aided design-computer aided machining porcelain (Vitabloc MKI) were examined. A total of 105 bars of the feldspathic ceramic were made, randomly divided into seven groups, and sintered according to manufacturer's recommendations. The groups consisted of as-fired, self-glazed, overglazed, ground, polished, ground/annealed, and polished/annealed. A total of 45 bars of the aluminous ceramic and Vitabloc MKI were made and randomly divided into three groups: as-fired, ground, and polished. Overglazing, grinding, and polishing all significantly increased (P < .05) the flexural strength (four-point-bend test) of the tested materials (15% to 30%).

Aluminum Oxide↗

PubMed1996

Effect of light intensity on polymerisation of three composite resins.

The polymerisation ability of twelve light activation units, a mixture of new and old, was assessed by micro-hardness evaluation of samples of three composite resins cured with the lights. Light intensity was assessed using a commercially available band held dental radiometer. Intensity values were representative of the range of intensities that may be found in clinical practice. When a 2 mm thick sample of a microfilled composite was cured for 40s less than half of the light units evaluated produced an acceptable lower surface polymerisation. All but one of the light units tested produced a satisfactory lower surface cure with the monomodal and the hybrid composites. For the products tested material composition was an important factor in regard to the ability to cure a 2 mm thick increment of material with a 40s irradiation time. A significant correlation was found between lower surface hardness and light intensity. Standardising the area of the light sensing device of the hand held radiometer with respect to the diameter of the specimen to be cured improved the correlation between light intensity and lower surface micro-hardness.

Composite Resins↗

PubMed1997

On the three-point flexural tests of dental polymeric resins.

Currently acrylic resins are commonly employed in many medical applications, especially for the fabrication of long span provisional restorations in dentistry and bone cement in orthopedics. On of the major problems associated with the conventional type of acrylic resins is their unsatisfactory mechanical properties. Among many attempts to strengthen acrylic resins, it has been demonstrated that they can be strengthened through the addition of reinforcement(s) as structural components of different size, shape and chemical composition, dispersed in the acrylic matrix, thus forming a composite structure. In the course of studies to strengthen dental polymeric resins by admixing various metallic oxide particles, PMMA-, PEMA-, and PIMA-based resins were reinforced by 2 vol.% added alumina, magnesia, zirconia, and silica powders. It was found that PMMA admixed with 2 vol.% zirconia exhibited the best improvement of mechanical properties (breaking strength, modulus of elasticity, offset yield strength, and fracture toughness as well). All tests were conducted under three-point bending. It was also found that the breaking strength based on the original sample dimension was, at most 20% less than those based on the final sample dimension. Moreover, this discrepancy was independent of the type of tested material, but dependent on the sample's modulus of elasticity.

Analysis of Variance↗

PubMed1997

An evaluation of the allergic contact dermatitis potential of colloidal grain suspensions.

BACKGROUND: Colloidal grain suspensions have been used for decades as adjuncts in the treatment of atopic dermatitis, especially in the US. In Italy, many young children have been exposed to colloidal grains. Recently, it was suggested that these bath therapies may induce allergic contact dermatitis in some young atopic children. OBJECTIVE: To evaluate the allergic skin reactions to topical oat and rice colloidal grain suspensions of normal and atopic children with and without previous exposure to colloidal grain suspensions. METHODS: A double-blind, randomized patch study. Two concentrations of oat and rice colloidal grains (0.007% and 0.7%) were applied occlusively to the backs of 65 children living in Italy, ages 6 months to 2 years (43 were atopic and 22 were normal). RESULTS: There were neither immediate urticarial nor allergic reactions in any of the 65 study subjects, atopic or nonatopic; 5 of 43 (12%) atopic subjects developed irritant reactions to the test materials. Radioallergosorbent tests (RAST) tests were performed on 55 subjects. The negative RAST test results found in the nonatopic group correlated well with nonatopic status, but positive RAST tests were found in only 8 of 35 (23%) atopic dermatitis subjects. None of the sera from positive RAST scores corresponded to subjects with irritant patch reactions. CONCLUSIONS: The data indicate that topical colloidal grains can be used as an adjunct in the management of mild atopic dermatitis in children under 2 years of age. There was no evidence of sensitization to topical colloidal grains in the group studied.

Avena↗

PubMed1997

The soft keratoprosthesis.

PURPOSE: The purpose of this work was to develop a keratoprosthesis which utilizes a biocolonizable skirt attached to a soft, elastomeric optic for world-wide application. METHODS: Over a period of 20 years, using in vivo animal implantation studies, a series of experiments was conducted testing materials for biocompatibility and durability which resulted in the development of an improved design. A new surgical technique was developed, using porous, biocolonizable haptics embedded within the sclera and combined with the established techniques of resection of Descemet's membrane and a conjunctival flap. RESULTS: Animal implantation studies indicated that 6 haptics, equidistantly placed, was the optimal shape. Two clinical trials resulted in the selection of an aliphatic polyether-based urethane for the optic and 60 mu pore polytetrafluoroethylene for the porous ingrowth material. Heated, pressurized injection moulding proved to be the optimal bonding method between the skirt and the optic. Sclerally embedded haptics achieved excellent integration with the tissue. CONCLUSIONS: This keratoprosthesis is a significant improvement over previous models with a rigid optic in that: 1. The porous ingrowth haptic is sclerally anchored, preventing extrusion. 2. It has a soft elastomeric optic which more successfully defuses the shearing forces of the keratoprosthesis/tissue interface secondary to blinking. 3. The optic is less massive and of greater circumference at the optic/tissue interface, thereby imparting less energy per area with a given movement. 4. The optic does not project posteriorly thereby decreasing anterior chamber irritation and reducing the possibility of glaucoma, uveitis, endophthalmitis, and retinal detachment. 5. This keratoprosthesis allows a normal field of view for the patient and an effective funduscopic view for the surgeon. 6. The large optical diameter eliminates problems with decentralization of the image. 7. It has a significantly better cosmetic appearance.

Aged↗

PubMedDate not supplied

A quantitative comparison of machined commercially pure titanium and titanium-aluminum-vanadium implants in rabbit bone.

Screw-shaped implants made from rods of commercially pure titanium (grade 1) and titanium-aluminum-vanadium (grade 5) were machined, and the implant surface structures were numerically described before being placed in rabbit tibiae for healing periods of 1 months, 6 months, and 12 months. Quantitative comparisons of the removal torque (Ncm) necessary to loosen the implants from the bone bed were performed. Short-term (1 month) observations revealed no significant differences between the two tested materials. However, after 6 and 12 months, the commercially pure titanium implants were significantly more stable in the bone bed, as compared to the alloy samples. After 6 months, the commercially pure titanium had a mean removal torque of 29 Ncm versus 23 for the alloy (P = .01), and after 12 months, the mean removal torque was 38 Ncm for commercially pure titanium as compared to 35 Ncm for the alloy (P = .01). Quantifications of the bone tissue response to the materials did not show any significant differences; however, the commercially pure titanium showed a tendency to have a higher percentage of bone in contact with the implant as compared to the alloy screws. Bone volumes in the threads were similar. The absence of any quantitative light microscopic difference after 1 month following placement may relate to the fact that there was a sparse amount of bone, since the tissue was in the organization/granulation phase. After 6 and 12 months of follow-up, substantial bone formation had occurred, resulting in significantly increased removal torques for the commercially pure titanium samples.

Alloys↗

PubMed1989

[Study on the finishing line of the metal framework in terms of modal analysis].

The finishing line on a metal framework strengthens the mechanized coupling between the metal and the resin. However, due to extreme variations in metal thickness on the finishing line section, stress tends to concentrate in certain areas during function, making the finishing line an area with frequent denture breakage in a clinical setting. The author used modal analysis to clarify the manner in which stress concentrates on the finishing line. The activity observed was them used to determine the influence on the activity of the finishing line from factors such as differences in the finishing line angle, differences in the major connector and differences in the skeleton configuration. The following results were obtained. 1. Regarding the resonance frequency of the test materials, modes 6-7 were detected. 2. Displacement in the periphery of the finishing line and for the major connector in each mode was extremely small compared to the amount of downward pressure on the mucose and the labio-lingual displacement of natural teeth. 3. The activity of the test materials between 200Hz and 300Hz was the rigid body mode for the entire test material using as a fulcrum the rest on the side where vibration was applied. There was resonance detected in the test materials between 1 kHz and 6 kHz. 4. It is believed that there is less concentration of stress on a palatal bar when the angle of the finishing line is an obtuse angle. 5. It was difficult to determine any effect on activity due to the difference in the angle of the finishing line on a palatal bar, lingual bar and lingual plate. 6. The skeleton configuration was more bended the lattice type than the ladder type.

Dental Stress Analysis↗

PubMed1994

Characterization of exposure and dose of man made vitreous fiber in experimental studies.

The use of fibrous test materials in in vivo experiments introduces a number of significant problems not associated with nonfibrous particulates. The key to all aspects of the experiment is the accurate characterization of the test material in terms of fiber length, diameter, particulate content, and chemistry. All data related to fiber properties must be collected in a statistically sound manner to eliminate potential bias. Procedures similar to those outlined by the National Institute of Occupational Safety and Health (NIOSH) or the World Health Organization (WHO) must be the basis of any fiber characterization. The test material to which the animal is exposed must be processed to maximize the amount of respirable fiber and to minimize particulate content. The complex relationship among the characteristics of the test material, the properties of the delivery system, and the actual dose that reaches the target tissue in the lung makes verification of dose essential. In the case of man-made vitreous fibers (MMVF), dose verification through recovery of fiber from exposed animals is a complex task. The potential for high fiber solubility makes many of the conventional techniques for tissue preservation and digestion inappropriate. Processes based on the minimum use of aggressive chemicals, such as cold storage and low temperature ashing, are potentially useful for a wide range of inorganic fibers. Any processes used to assess fiber exposure and dose must be carefully validated to establish that the chemical and physical characteristics of the fibers have not been changed and that the dose to the target tissue is completely and accurately described.

Animals↗

PubMedDate not supplied

The effects of vehicles on the human dermal irritation potentials of allyl esters.

Allyl esters, frequently used in the fragrance industry, often contain a certain percentage of free allyl alcohol. Allyl alcohol is known to have a potential for delayed skin irritation. Also present in the finished product are different solvent systems, or vehicles, which are used to deliver the fragrances based upon their intended application. This study was conducted to determine whether different vehicles affect the skin irritation potential of five different allyl esters. The allyl esters tested were allyl amyl glycolate, allyl caproate, allyl (cyclohexyloxy)acetate, allyl cyclohexylpropionate, and allyl phenoxyacetate in the vehicles diethyl phthalate, 3:1 diethyl phthalate:ethanol, and 1:3 diethyl phthalate:ethanol at concentrations of 0.1%, 0.5%, 1.0%, and 2.0% (w/w). A modified cumulative irritation test was conducted in 129 human subjects. Test materials (0.3 ml) were applied under occlusion to skin sites on the back for 1 day (24 h) using Hill Top chambers. Irritation was assessed at 1, 2, 4, and 5 days following application of test materials. Cumulative irritation scores varied considerably among test materials. There were no delayed irritation observations. The highest irritation scores were observed at the 2.0% concentration for all test materials. The irritation scores for allyl amyl glycolate, allyl (cyclohexyloxy)acetate, and allyl phenoxyacetate were highest in 1:3 diethyl phthalate:ethanol, thus the resulting calculated no-observed-effect levels, 0.12%, 0.03%, and 0%, respectively, were much lower for this vehicle compared to the diethyl phthalate vehicle, 0.33%, 0.26%, 0.25%, respectively. These data showed a trend for lower concentration thresholds to induce irritation when higher levels of ethanol were used in the vehicle.

Esters↗