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Additional types of silicone biopolymers are widely used in maxillofacial prosthetics. Therefore, the knowledge of the solar radiation's effect on their structural stability is highly important. Four different industrially synthesized biomaterials were examined, called Episil Europe 1, Europe 2, Europe 3 and Africa 3, which were exposed to solar radiation (UVA, UVB) for eight different time periods (from 8 to 168 h). Structural damages due to irradiation exposure were investigated by mechanical tests (compression) and differential scanning calorimetry (DSC) methods. Simple mathematical models were developed, containing parameters with physical meaning such as maximum stress (sigma(max)), maximum strain (epsilon), elasticity parameter (E), and viscoelastic parameter (p), for the compression test, and melting temperature (T (m)) and Enthalpy in melting point (Heat) for DSC. With increasing irradiation time their maximum stress and strain decreased significantly, and the materials lost their elasticity and molecular stability. A decrement in their melting points and heats was observed as irradiation time was increasing. Finally, experimental results demonstrated that solar radiation has a severe effect on the structural stability of the examined biomaterials.

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STATEMENT OF PROBLEM: The ultimate goal of denture repair is to restore the denture's original strength and avoid further fracture. The best materials and methods for repair have not been conclusively determined. PURPOSE: This study investigated the fracture force, deflection at fracture, and toughness of a heat-polymerized denture base material repaired with heat-polymerized resin, autopolymerized resin alone, or autopolymerized resin with glass fiber or wire reinforcement. MATERIAL AND METHODS: Eight groups were evaluated: 6 with autopolymerized resin repairs, 1 with heat-polymerized resin repairs, and a control group of intact specimens. The 6 autopolymerized resin groups included 1 group with no reinforcement, 1 treated with microwave irradiation after polymerization, 2 with monolayer or multilayer glass fiber reinforcement, and 2 with round or braided wire reinforcement. Each group consisted of 12 specimens. The experimental specimens were cut, and a 3-mm butt joint gap was repaired as indicated by the group assignment. A 3-point bending test was used to determine the fracture force, deflection at fracture, and toughness of the specimens. The data were analyzed with 1-way analysis of variance and the Tukey post-hoc test (alpha=.05). RESULTS: The fracture force (28.4 to 73.4 N), deflection (1.6 to 3.8 mm), and toughness (0.02 to 0.13 J) values for all repaired groups were significantly lower than those for the control group (82.79 N, 4.4 mm, and 0.16 J, respectively), with one exception: the mean fracture force of specimens reinforced with round wire (102.9 N). Failure mode was always adhesive, meaning that fracture occurred between the denture base and repair resin. CONCLUSION: Among the repair treatments tested, the most effective was microwave-irradiated, autopolymerized resin reinforced with round wire or monolayer glass fiber ribbon.

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PURPOSE: The purpose of this study was to determine the hardness of plasticized acrylic resin soft lining materials over time when curing procedures were modified and when surface sealers were either used or omitted. MATERIALS AND METHODS: A chairside plasticized acrylic resin material and a heat processed plasticized resin material were made into disks 40 mm in diameter and 10 mm in thickness. Materials were cured by processing at an elevated temperature or at mouth temperature. Five samples were used with each processing method. Half of all samples were treated with a surface sealer, whereas the other samples received no surface treatment. After processing, the samples were immersed in 37 degrees C water for a total time of 1 year. Specimens were tested to determine hardness on a monthly basis. Testing was accomplished using a Shore A durometer. RESULTS: Hardness testing showed differences relative to material and to time after processing. The heat-processed plasticized resin material showed significantly higher Shore A hardness values than the chairside over the entire experimental period (p <.01). Increased hardness was seen for all materials over time, but this was more pronounced with plasticized acrylic resin in which the hardness increased from 28.4% to 115.8% depending on processing method and surface treatment. Surface treatment showed significant softening only when the samples were cured at simulated mouth temperature (p <.05). CONCLUSIONS: Processing method and time after processing have an effect on surface hardness of the tested materials, but neither of these effects is as profound as the initial choice of material. J Prosthodont 2001;10:42-45.

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The expression of lactoferrin (LF), ceruloplasmin (CP) and secretory component (SC) in various thyroid diseases was investigated using an immunohistochemical method. LF is an iron-binding protein overexpressed in certain human adenocarcinomas. CP is implicated in carcinogenesis and SC is part of the local immune defense system. Sections of 15 follicular adenomas, 5 follicular carcinomas (FC), 16 papillary carcinomas (PC), 15 goitres and 2 cases of lymphocytic thyroiditis were re-examined and investigated immunohistologically by a streptavidin-biotin method. A positive immunostain reaction for CP and LF was observed in all cases of PC and FC. A positive immunostain reaction for SC was observed in 13/16 cases of PC and 4/5 cases of FC. A negative immunostain reaction for CP, LF and SC was observed in medullary cancers, in follicular adenomas and in the cases with goitre. We conclude that the immunostain expression of LF, CP and SC is a valuable diagnostic aid in the differential diagnosis between benign and malignant thyroid tumors. The expression of SC indicates the presence of a local immunodefensive system.

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STATEMENT OF PROBLEM: Facial prostheses worn over an extended time are exposed to various environmental factors, including sebaceous oils (sebum) and perspiration. PURPOSE: This study investigated the physical properties of tensile strength and modulus, elongation, tear strength, hardness, weight, and color change, of a silicone facial elastomer after immersion for 6 months in simulated sebum and perspiration at 37 degrees C. MATERIAL AND METHODS: Specimens made of Episil silicone elastomer were immersed in simulated alkaline or acidic perspiration as well as in sebum. Tensile and tear tests were conducted according to ISO specifications no. 37 and 39, respectively, in a Monsanto testing machine. Shore A hardness measurements were run according to ASTM D 2240. Weight changes were followed at 5, 15, 30, and 180 days, and color changes were determined in the CIE LAB system using a tristimulus colorimeter. RESULTS: An improvement of mechanical properties for specimens immersed in acidic perspiration was attributed to facilitation of the propagation of cross-linking reaction during aging of the silicone samples. Some weight increase was observed for the specimens immersed into the aqueous solution, whereas for those immersed in sebum, weight loss was recorded, probably because of extraction of some compounds. In this latter case, the color change was lower than that corresponding to simulated perspiration. CONCLUSION: The silicone specimens aged for a period, which simulates 1.5 years of clinical service, showed minimal changes with respect to the properties studied.

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BACKGROUND: Gangliocytic paraganglioma of the duodenum is a peculiar neuroendocrine tumor, often revealed as an incidental radiographic finding or as a result of gastrointestinal hemorrhage, due to frequent ulceration of the overlying mucosa. Most lesions are pedunculated and submucosal with distinctive histology, consisting of endocrine, ganglion and spindle-shaped Schwann cells. METHODS: A case of a duodenal gangliocytic paraganglioma is reported in a 50-year-old woman presenting with episodes of melena. Enteroclysis revealed a pedunculated tumor observed either in the second or third portion of the duodenum. Upper gastrointestinal endoscopy revealed a pedunculated ulcerated tumor which was subsequently confirmed by computed tomography. The tumor was simply excised through a duodenotomy. RESULTS: The size of the tumor was 4.5 x 3 x 1.5 cm. Immunohistochemical and ultrastructural features of the tumor classified it as a typical duodenal gangliocytic paraganglioma with positive cellular reaction for neuron-specific enolase, chromogranin, somatostatin, gastrin and S100. CONCLUSION: Forty-six months after surgery, the patient is well with no evidence of recurrence. The majority of the reported duodenal gangliocytic paragangliomas were of benign nature. However, the fact that in 4 isolated cases there was lymph node involvement indicates that thorough investigation for lymph node metastases is needed, as well as thorough postoperative follow-up.

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UNLABELLED: The aim of this study was to investigate the presence of a local immunological defense mechanism of the secretory IgA class in the female genital tract. MATERIAL AND METHODS: We studied by a streptavidin-biotin method the secretory component (SC) and IgA distribution in paraffin-embedded sections of 90 formalin-fixed specimens. We studied 10 normal and 5 neoplastic cervical specimens, 20 normal, 10 hyperplastic endometrial specimens and 10 endometrial adenocarcinomas, 5 normal ovarian tubes and 30 ovarian epithelial neoplasms, serous and mucinous. A polyclonal SC and (Dako) and a mab IgA (Dako) was used and the reaction was scored from 1-3. RESULTS: Normal cervical mucosa and atrophic endometria were negative, while the basal portion of the endometrium, focally the proliferative glands, most of the secretory glands and most of the hyperplastic glands were positive for SC. IgA showed a similar distribution and a perivascular stromal reaction. Adenocarcinomas were positive for SC, but the intensity of the reaction was dependent on the differentiation of the tumors. Mucous and most serous neoplasms were negative for SC. IgA showed a similar reaction. CONCLUSION: There is evidence that the female genital tract has a local defensive immune system that may be hormone dependent. SC is a valuable marker of glandular differentiation.

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The pathological features of three cases of verrucus carcinoma of the vulva, examined in our laboratory during the last decade are presented. Verrucus carcinoma of the vulva is of special interest because of its rarity (6.5% of our cases of malignant lesions of the vulva), its special morphology and the problems in differential diagnosis that are encountered. There is also evidence that there is an association with HPV infection. We present the pathological features of three cases of verrucus carcinoma that we studied in the last decade in our Laboratory among 48 malignant lesions of the vulva. An immunohistochemical detection of HPV was performed by the streptavidine-viotine method and classification by in situ hybridization showed the presence of HPV 6/11 in all cases.

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With the advent of newer methods of activation of the polymerisation of denture base resins, there is a need to compare their physical properties using various modes of activation. Indentation creep, recovery and hardness of denture base resins polymerised either by microwave irradiation or heat were compared. A microwave curing cycle of 3 minutes at 500W was used. The Wallace microhardness tester and an indentation creep test were employed in order to evaluate the denture base resins. Under the experimental conditions of the study the results indicated that indentation creep, recovery and cyclic loading-deloading were similar in the resins polymerised by the two methods. Hardness was either similar or a softer produce was produced by microwave irradiation for two of the resins used. Hardness seems to be more sensitive to residual monomer levels, and for this reason a suitable microwave curing cycle should be employed to optimise all the physical properties.

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Three bonding agents were evaluated to determine their effect on the strength of the bond when Silskin II and Cosmesil SM4 silicone facial elastomers were polymerized to a light-activated denture resin. A silane bonding agent proved to be superior, whereas a light-activated bonding agent had inferior bonding characteristics. Intensive heat aging had no significant effect on bond strength.

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A new denture base system, Provac, has been developed for complete and partial dentures, and for relining. The Provac material is methyl methacrylate, which cures with the aid of barbituric acid. In this study the physical and mechanical properties of the new resin were investigated and compared with those of a conventional autopolymerizing material (Croform) and a conventional heat polymerizing material (Trevalon). It was found that the dimensional accuracy of Provac was better than that of the conventional heat-curing material, Trevalon, and the denture was finished more easily and quickly. The physical and mechanical properties of Provac resin were found to be similar to those of the other two materials, and conformed to the International Specifications for denture base materials. The residual monomer levels in Provac material were always higher than the minimal obtainable values associated with conventional heat-cured materials when these were polymerized with a terminal boil during the curing cycle.

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