Intraoral contact allergy to materials used in dental practice. A critical review.
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Intraoral contact allergy reactions are clinically poorly differentiated and understood, and are not very commonly described in the specialized literature. Although such reactions appear to be scantly relevant, evidence suggests that they may be more frequent than previously believed. No single or specific clinical picture of intraoral contact allergy exists, though lichenoid reactions appear to be the most common manifestations. Epicutaneous patch testing, together with the clinical manifestations, constitute the most widely used diagnostic approach in such situations. Metals used in dental practice--particularly amalgams and gold--are the most commonly reported causes of intraoral allergic reactions, though hypersensitivity to resins is increasingly mentioned in the literature, as a consequence of their increasingly widespread use. The systematic intraoral elimination or substitution of materials inducing cutaneous hypersensitivity has recently been questioned, while on the other hand it not possible to discard an allergic component in some nonspecific stomatological disorders. The present study offers clinicians an evidence-based update of current knowledge in this field. (+info)
Effects of cyclic loading on viscoelastic properties of soft lining materials.
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The cyclic loadings during mastication supposedly accelerate degradation of soft lining materials. The purpose of this study was to investigate the effects of cyclic loading on viscoelastic properties of soft lining materials. Two plasticized acrylics, two silicones and one isoprene-based monomer contained elastomer were selected. Cylindrical-shaped specimens, 10 mm X 10 mm phi, were prepared. Twenty specimens were subjected to cyclic loading in a water bath at 37 degrees C; another twenty specimens were without cyclic loading. The viscoelastic properties were measured using a creep-meter. The cyclic loading significantly decreased the heights of the two materials, the instantaneous elastic displacements of one acrylic liner and the viscous flows of three materials. The cyclic loading affected mainly delayed deformations. Therefore, cyclic loading was a useful method for evaluating the durability of soft lining material. (+info)
Wear test combining simulated occlusal wear and toothbrush wear.
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A new wear testing system, which carries out toothbrush wear and simulated occlusal wear tests alternately, was developed. Differences in wear behavior among three modes of wears, combined wear, toothbrush wear and simulated occlusal wear, were investigated using polymethylmethacrylate (PMMA) and two commercial resin composites (Z100, APX). The area of the material loss after each test was measured on the worn surfaces to evaluate the different modes of wears. On PMMA and Z100, the toothbrush wear corresponded to the combined wear, suggesting that toothbrush wear was dominant in the combined wear for these materials. On the other hand, the occlusal wear was dominant corresponding to the combined wear on APX. Both the simulated occlusal wear and toothbrush wear tests are essential to evaluate the wear behavior of restorative materials, and the combined wear test is effective to analyze the wear behavior of restorative materials under different wear processes which consist of toothbrush wear and simulated occlusal wear. (+info)
Gypsum-bonded investment and dental precision casting (I) two investments.
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The present study compared the TE of two gypsum-bonded dental casting investments, the oldest K and more recent G. They had almost identical composition, 70% refractory (cristobalite) and 30% binder, but had different recommended water/powder ratios, 0.40 (K) and 0.33 (G). The average TE was significantly less (1.19%) in K than in G (1.45%); the volume decrease accompanied by the phase change of gypsum was more pronounced in the less dense K. When the dehydration conditions around gypsum are similar to those prevailing in wet calcinations methods, an expansion is likely to occur in the mold due to the formation of dental stone by recrystallization. This additional expansion has not been detected in ordinary laboratory measurement but can effectively increase the actual TE of an investment. The present study has proved the formation of dental stone by rapid heating of an investment. Specific laboratory techniques may have been supplementing low TE by this mechanism. (+info)
Changes in occupational health problems and adverse patient reactions in orthodontics from 1987 to 2000.
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The purpose of the present investigation was to assess the reasons for changes in occupational health problems and patient reactions to orthodontic treatment after a survey carried out in 1987. Questionnaire data on occupation-related health complaints and patient reactions over the preceding 2 years were obtained from 121 of 170 Norwegian orthodontists (71 per cent). Most health complaints were dermatoses of the hands and fingers related to the processing of acrylic removable appliances, to composite bonding materials, or gloves. A few reactions were of a respiratory or systemic nature. In total, occupation-related dermatoses were reported by 17.4 per cent (21/121) compared with 40 per cent previously. Non-dermal complaints comprised 9 per cent compared with 18.2 per cent in 1987. Patient reactions were distributed equally between intra-oral reactions affecting lips, gingiva, oral mucosa, and tongue, and dermal reactions affecting the corner of the mouth, the dorsal part of the neck, the peri-oral area, cheeks, chin or skin elsewhere. A few patients had systemic reactions. The assumed eliciting agents of intra-oral reactions were fixed metallic appliances, acrylic removable appliances, polymer brackets or composite bonding materials, or were related to elastics. Extra-oral (dermal) reactions were attributed to metallic, elastic or textile parts of the extra-oral appliances. Some reactions were verified as allergies. The percentage of patient reactions in total was estimated to be 0.3-0.4 per cent compared with 0.8-0.9 per cent in 1987. The reduction in occupation-related health complaints among orthodontists was explained by changes in previously important hygiene factors such as soaps, detergents, etc., whereas the biomaterials-related reactions persisted. The reduction in the 2 year incidence of patient reactions was associated with a marked reduction in extra-oral reactions following preventive measures such as coating metallic devices, whereas the intra-oral reactions persisted at the same level as previously. (+info)
Effects of a non-rinse conditioner on the enamel of primary teeth.
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The aim of this in vitro study was to evaluate by scanning electron microscopy the morphological aspects of the enamel of primary teeth after etching with 36% phosphoric acid or a non-rinse conditioner. Ten naturally exfoliated anterior primary teeth were selected. The samples were subjected to prophylaxis with pumice paste and water using a low-speed hand piece. Etching was done on the buccal surface. Specimens were divided into 2 groups: G1 (n=10): etching with 36% phosphoric acid gel - Conditioner 36 (Dentsply) for 20 s, followed by water rinse for 15 s; G2 (n=10): etching with NRC - Non Rinse Conditioner (Dentsply) for 20 s, followed by air drying for 15 s. The samples were dehydrated, mounted on metal stubs, coated with gold and observed with Jeol JSM-6100 scanning electron microscope. Electron-micrographic analysis showed that both etching agents were effective for etching the enamel of primary teeth causing the formation of microporosities on the enamel surface, although the etching pattern was more effective with the use of 36% phosphoric acid gel. (+info)
In vitro inhibition of caries-like lesions with fluoride-releasing materials.
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The aim of this study was to compare the in vitro caries inhibition of various resin-based materials. Class V cavities were prepared in twenty-five freshly extracted human premolar teeth which were then restored with glass-ionomer cement (Chemfill II), compomer (Compoglass F, Dyract AP) and composite resin (Tetric Ceram and Z 100). The teeth were submerged in an acid gel for 6 weeks. Each specimen was sectioned. These sections were left in water for 24 hours, and then examined using polarized light microscopy. The lesion consisted of two parts, the outer surface lesion and the cavity wall lesion. There was no significant difference in the body depth of the outer lesion and in the depth of the wall lesion among teeth restored with Compoglass F, Dyract AP and Chemfill II (P > 0.05). There was a significant difference between those restored with Z 100 and Tetric Ceram (P < 0.05). The length of the wall lesion for the teeth restored with Chemfill II was significantly smaller than that in the remaining groups (P < 0.05). The length of the wall lesion for teeth restored with Tetric Ceram and Z 100 was significantly higher than in the remaining groups (P < 0.05). These results suggest that composite materials and compomer provide less caries inhibition than glass-ionomer cements. (+info)
Evidence that HSP70 gene expression may be useful for assessing the cytocompatibility of dental biomaterials.
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In the current studies, we examined the possibility of using HSP70 gene regulation as a cytocompatibility test for dental biomaterials. For this reason, we assessed the effects of three metal salts, HgCl2, CuSO4 and NiCl2 on HSP70 gene expression in HeLa S3 cells using real-time Taqman quantitative PCR. Incubation of the cells for 4 h in medium containing HgCl2 (20 or 40 microM), CuSO4 (157, 313, 625 or 1250 microM) or NiCl2 (5000 and 10000 microM) significantly induced HSP70 mRNA. The real-time Taqman quantitative PCR was able to detect HSP70 mRNA induction at 4-fold lower concentrations of HgCl2 and 8-fold lower concentrations of CuSO4 than the Neutral Red cell viability assay. These results indicate that real-time Taqman quantitative PCR, in combination with the monitoring of cell viability, may be a valuable tool for distinguishing between specific HSP70 mRNA induction and cytocompatibility of metals in dental biomaterials. (+info)