Microleakage and SEM evaluation of fissure sealants placed by use of self-etching priming agents.

OBJECTIVES: This study evaluated the microleakage and internal seal of fissure sealants placed by use of self-etching priming agents in comparison to phosphoric acid etching of enamel. METHODS: Seventy-two caries-free extracted human molars were divided into six groups with 12 teeth each. Occlusal surfaces were cleansed by either pumicing (Groups I, III, V) or by 15-s air-abrasion treatment with 25 microm aluminum oxide particles (Groups II, IV, VI). Fissures were sealed with the self-etching priming systems, Clearfil Liner Bond 2 (Groups I, II) or Resulcin AquaPrime (Groups III, IV). In Groups V and VI, sealants were placed after phosphoric acid etching. Half of the teeth in each group were thermocycled. After staining with 0.5% methylene blue, the teeth were sectioned for evaluation of microleakage. Internal adaptation of the fissure sealants was analyzed by SEM on replicas of cross sections. RESULTS: Independent of the methods used for cleansing of the occlusal surfaces, fissure sealants in Groups I and II showed significantly more microleakage and less sufficient internal seal as compared to sealants placed in Groups III to VI. Sealants placed by Resulcin AquaPrime (Groups III, IV) leaked significantly more than sealants applied after phosphoric acid etching (Groups V, VI) of the enamel. However, statistical analysis (H-test) did not reveal significant differences concerning the internal adaptation of sealants placed in Groups III, IV, V and VI. CONCLUSIONS: Concerning the microleakage data, use of the self-etching bonding systems, Clearfil Liner Bond 2 and Resulcin AquaPrime, cannot be recommended for fissure sealing, since the sealing ability is less effective as compared to the conventional acid-etching technique.

Effect of different luting materials on the marginal adaptation of Class I ceramic inlay restorations in vitro.

OBJECTIVES: The aim of this in vitro study was to assess the marginal adaptation of prefabricated Class I ceramic inlay restorations placed with various luting materials. METHODS: Forty-two standardized occlusal cavities were prepared in extracted human molars with diamond burs exactly corresponding to the dimensions of prefabricated glass ceramic inlays. The prepared teeth were randomly assigned to seven groups of six teeth each and restored using (1). the composite resin Tetric Ceram in increment technique [Group I] or (2). ceramic inlays (Cerana) luted with: the composite based materials Dual Cement [Gr. II] and Panavia 21 [Gr. III], the compomer material Dyract Cem [Gr. IV], Dyract Cem with additional use of Prime & Bond 2.1 [Gr. V], the silicophosphate cement Trans-Lit [Gr. VI], or the ethylcyanoacrylate Cyano-Veneer [Gr. VII]. Marginal adaptation was evaluated by SEM-analyses before and after thermal cycling (2500 cycles; 5-55 degrees C) and mechanical loading (100N; 500000 cycles) using replica models. Kruskal-Wallis H-test and Mann-Whitney U-test were used for statistical analyses. RESULTS: Group I (increment technique) as well as Groups II-V (inlay technique) revealed high percentages of perfect marginal adaptation in over 95% of the analyzed margins, both before and after thermo-mechanical loading. Statistical significant differences could not be detected within these groups. All inlays luted with silicophosphate cement (Group VI) and four of six inlays applied with Cyano-Veneer (Group VII) fractured under occlusal load. SIGNIFICANCE: A stable bonding to the enamel and to the ceramic inlay was achievable with the composite luting resins Dual Cement and Panavia 21 as well as with the compomer based luting material Dyract Cem but not with the use of the silicophosphate cement Trans-Lit or the ethylcyanoacrylate Cyano-Veneer.

In-vitro pulp chamber temperature rise during composite resin polymerization with various light-curing sources.

OBJECTIVES: The purpose of this in vitro study was to measure the pulp chamber temperature increase induced during composite resin polymerization with various visible light-curing units. METHODS: A Class II cavity was prepared in an extracted molar tooth, leaving a dentin layer 1 mm thick between pulp chamber and proximal cavity wall. A 2 mm composite resin layer was applied to the proximal box and light-cured with the selected curing units: Heliolux II (H; 320 mW/cm2), QHL 75 (Q; 505 mW/cm2), Astralis 5 (A; 515 mW/cm2), Optilux 500 (O; 670 mW/cm2), Elipar Highlight (EH; 730 mW/cm2), ADT 1000 PAC (P; 1196 mW/cm2). Light-curing took place for 40 s (H, A, Q, O, EH), 5 and 10 s (P). Measurement of pulp chamber temperature changes (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization was performed with a K-type thermocouple positioned at the pulp-dentin junction. Mean values were calculated from 10 measurements with each light-curing unit. ANOVA and Dunnett t-test were used for statistical analyses. RESULTS: Maximum temperature changes varied significantly depending on the light-curing unit used: 2.9 +/- 0.3 degrees C (H), 4.7 +/- 0.5 degrees C (A), 5.4 +/- 0.3 degrees C (P, 5 s), 5.6 +/- 0.4 degrees C (Q), 6.1 +/- 0.2 degrees C (EH, 2-step mode: 100 mW/cm2 over 10 s, 730 mW/cm2 over 30 s), 6.9 +/- 0.4 degrees C (EH), 7.3 +/- 0.3 degrees C (O), 7.8 +/- 0.9 degrees C (P, 10 s). SIGNIFICANCE: It is concluded that light-polymerization with curing units characterized by high energy output (A,EH,O,P,Q) causes significantly higher pulp chamber temperature changes as compared to the conventional curing light (H). Therefore, clinicians should be aware of the potential thermal hazard to the pulp which might result from visible-light curing of composite resins.

Self-etching primer vs phosphoric acid: an alternative concept for composite-to-enamel bonding.

The purpose of this in vitro study was (1) to investigate the composite-to-enamel bond strength and (2) to analyze the marginal adaptation of resin composite restorations in class 2 cavities using three self-etching priming agents in comparison to conventional phosphoric acid etching and bonding application. In the first part of the study 24 extracted bovine incisors were embedded in acrylic resin and ground flat with 800-grit paper. The following three self-etching priming agents/composite resins were applied to the enamel surfaces of six teeth each: Clearfil Liner Bond 2/Clearfil AP-X (Group I), Etch & Prime 3.0/Degufill mineral (Group II), Resulcin AquaPrime + MonoBond/Ecusit (Group III). In Group IV Ecusit-Mono/Ecusit was used after enamel etching with phosphoric acid (37%). Shear bond strength values measured on a T22 K testing machine at a crosshead speed of 1 mm/min were: 24.2 +/- 3.0 MPa (Group I), 21.9 +/- 1.4 MPa (II), 34.0 +/- 3.6 MPa (III), and 26.3 +/- 1.8 MPa (IV). ANOVA revealed significant (P < 0.05) differences in shear bond strength between groups, except comparison of Group I and II, and Group I and IV. In the second part of the study 24 standardized class 2 cavity preparations with the approximal box extending 1 mm above the CEJ were prepared in extracted human molars. Enamel margins were beveled and the teeth were divided into four groups of six teeth each. Cavities were restored using the self-etching priming agents Clearfil Liner Bond 2 (Group I), Etch & Prime 3.0 (Group II), and Resulcin AquaPrime + MonoBond (Group III). In Group IV composite resin restorations were placed after 37% phosphoric acid etching and bonding application (Ecusit-Mono). Quantitative SEM analysis of the marginal adaptation of the restorations after thermocycling (5-55 degrees C, 2500 cycles) and mechanical loading (100 N, 500,000 cycles) revealed excellent, gap-free margins in 91.2% (Group I), 93.0% (Group II), 92.0% (Group III), and 92.5% (Group IV) of the restorations' approximal area. There were no statistically significant differences between the four groups (P < 0.05). In conclusion, results of the present in vitro study indicate that use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in composite-to-enamel bonding restorative techniques.

Prosaposin deficiency: further characterization of the sphingolipid activator protein-deficient sibs. Multiple glycolipid elevations (including lactosylceramidosis), partial enzyme deficiencies and ultrastructure of the skin in this generalized sphingolipid storage disease.

Sphingolipid activator protein (SAP) deficiency, previously described in two sibs and shown to be caused by the absence of the common saposin precursor (prosaposin), was further characterized by biochemical lipid and enzyme studies and by ultrastructural analysis. The 20-week-old fetal sib had increased concentrations of neutral glycolipids, including mono-, di-, tri- and tetrahexosylceramide, in liver, kidney and cultured skin fibroblasts compared with the controls. Glucosylceramide and lactosylceramide were particularly elevated. The kidney of the affected fetus showed additional increases in the concentration of sulphatide, galactosylceramide and digalactosylceramide. Free ceramide was stored in the liver and kidney, and GM3 and GM2 gangliosides were elevated in the liver, but not the brain, of the fetus. Phospholipids, however, were normal in the affected fetus. In the liver biopsy of the propositus, who later died at 16 weeks of age, only a few lipids could be studied. Glucosylceramide, dihexosylceramide and ceramide were elevated in agreement with our previous study. Enzyme studies were undertaken using detergent-free liposomal substrate preparations and fibroblast extracts. The sibs' beta-glucocerebrosidase and beta-galactocerebrosidase activities were clearly reduced, but their sphingomyelinase activities were normal. The normal activity of the latter enzyme and the almost normal tissue concentration of sphingomyelin in prosaposin deficiency suggest that the prosaposin-derived SAPs are not required for sphingomyelinase activity in vivo. In keeping with the biochemical findings, skin biopsies from the sibs showed massive lysosomal storage with a vesicular and membranous ultrastructure. The function of SAPs in sphingolipid degradation and the role of SAPs for enzyme activity in vitro are discussed. In addition, the similarity in neutral glycolipid accumulations in Niemann-Pick disease type C and in prosaposin deficiency are noted. The phenotype of the prosaposin deficient sibs resembled acute neuronopathic (type 2) Gaucher disease more than Farber disease in several aspects, but their genotype was unique.

GM2D gangliosidosis B1 variant in a boy of German/Hungarian descent.

After the introduction of 4-methylumbelliferyl-2-acetamido-2-deoxy-beta A-D-glucopyranoside (4MUG) and its sulfated form (4MUGS) in the pre- and postnatal diagnosis and carrier identification of gangliosidosis genotypes, infrequent forms of the GM2 gangliosidosis Type B (Tay-Sachs disease) have been observed which show normal activity of Hexosaminidase A (Hex A) isoenzyme with the substrate 4MUG but absent or deficient activity against the sulfated form 4MUGS. Here we report the observation of a German/Hungarian boy aged 12 when he died with a prolonged course of a neurodegenerative disorder, later biochemically identified as a GM2 gangliosidosis B1-variant which is characterized by a deficient Hex A activity only against 4MUGS. The first clinical symptoms had occurred after the age of 14 months with a clear manifestation of the disease at age 3, when he presented disturbances of movement and tended to fall down. The slowly progressive course with brain atrophy, seizures and severe mental deterioration resulted in death after almost 9 years. At autopsy, the typical light microscopic neuronal changes of a "lysosomal storage disorder" were found, with multilamellar concentric bodies (MCB) and Zebra bodies in the neuronal cytoplasm at the electron microscopic level.

Neural network classification of mutagens using structural fragment data.

A neural network was applied to a large, structurally heterogeneous data set of mutagens and non-mutagens to investigate structure-property relationships. Substructural data comprising a total of 1280 fragments were used as inputs. The training of the back-propagation networks was directed by an algorithm which selected an optimal subset of fragments in order to maximize their discriminating power, and a good predictive network. The system comprised three programs: the first used a keyfile of 100 fragments to generate training and test files, the second was the network itself and a procedure for ranking the effectiveness of these fragments and the third randomly replaced the lowest fragments. This cycle was then repeated. After running on a 386/33 PC several networks produced approximately 11% failures in the test set and 6% in the training set. By simplifying the output of the hidden layer it was possible to describe the hidden layer states in terms of clusters of mutagens and non-mutagens. Some of these clusters were structurally homogeneous and contained known mutagenic and non-mutagenic structural classes. This analysis provided a useful means of demonstrating how the network was classifying the data.

Disorders of glycoprotein degradation.

The intracellular degradation of glycoproteins occurs predominantly in the lysosomes through the concerted action of proteases and glycosidases. Genetic defects in any of the enzymes cleaving the oligosaccharide side chains lead to specific diseases because of an excessive lysosomal accumulation of partially degraded material, mostly oligosaccharides. This paper presents an overview of the biochemistry and the clinical spectrum of this group of diseases including sialidosis, galactosialidosis, alpha- and beta-mannosidosis, fucosidosis, aspartylglucosaminuria, and alpha-N-acetylgalactosaminidase deficiency (Schindler disease). In addition, the sialic acid storage disorder (Salla disease) which is caused by a defect in the lysosomal transport of this acidic monosaccharide is included because of functional and clinical correlations.

Defective lysosomal release of glycoprotein-derived sialic acid in fibroblasts from patients with sialic acid storage disease.

Fibroblasts from patients with sialic acid storage disease (SASD), sialidosis, mucolipidosis II, and from normal controls, were incubated in the presence of the glycoprotein fetuin that was tritium-labelled in its sialic acid residues by the periodate/[3H]borohydride reduction method, and the fate of the intracellular radioactive sialic acid (C7-sialic acid) followed in pulse-chase experiments. The model glycoprotein was readily endocytosed and degraded, more than 90% of the radioactivity being trichloroacetic acid (TCA)-soluble after 4 days of incubation. In all of the patients' fibroblasts, there was an increased accumulation of TCA-soluble radioactivity and, upon chase, a much lower rate of elimination than in normal controls. Gel chromatography of the material from the chase experiment showed that, in normal cells, most of the radioactivity at zero time behaved as free C7-sialic acid. This, as well as material of larger size (sialyloligosaccharides), was very much diminished by 48 h. In cells from two patients with SASD, there were large peaks both in the sialic acid and oligosaccharide positions; whereas the oligosaccharides were somewhat decreased by the end of the chase period, the sialic acid was essentially unchanged. In sialidosis fibroblasts, the radioactive material consisted of oligosaccharides, but very little C7-sialic acid; the elimination of the oligosaccharides was retarded. In normal cells, about 80% of the radioactivity released into the medium after 48 h chase behaved as free C7-sialic acid upon gel chromatography and t.l.c. Subcellular fractionation in Percoll gradients showed that the radioactive C7-sialic acid remaining in normal cells after 48 h of chase was mainly localized in the cytosol. In SASD cells, on the other hand, it was associated with lysosomal fractions which, unexpectedly, exhibited an abnormally low density. Our findings demonstrate that SASD fibroblasts degrade the sialoglycoprotein but, unlike normal cells, accumulate the liberated C7-sialic acid along with sialyloligosaccharides in their lysosomes. The results therefore support the concept of a defective transport system for sialic acid in the lysosomal membrane of patients with SASD.

Lysosomal sialidase deficiency: increased ganglioside content in autopsy tissues of a sialidosis patient.

Organs obtained at autopsy from a patient with sialidosis were analyzed for 'bound' sialic acid and their ganglioside and neutral glycolipid patterns determined. The water-soluble bound sialic acid was increased between 10- and 17-fold in visceral organs, but only about 2-fold in the brain, when compared to normal controls. Lipid-bound sialic acid was increased up to 8-fold in visceral organs due to elevated amounts of gangliosides GM3, GD3 and probably GM4 and LM1, whereas the brain showed no deviation from controls. An alteration of the neutral glycolipid pattern was also observed. The results indicate an impaired catabolism of gangliosides in sialidosis in addition to that of sialyloligosaccharides and sialoglycoproteins.

Micellar properties of glycosphingolipids in aqueous media.

The aggregation properties of neutral glycosphingolipids and gangliosides were investigated by ultracentrifugal sedimentation and gel permeation chromatography. Initially, glycosphingolipids in buffer formed high molecular aggregates. On standing, the glycosphingolipids produced smaller and stable micelles in equilibrium with their monomers at the critical micellar concentration (cmc). The cmc's of monohexaosyl- to tetrahexaosylceramides were on the order of 10(-8) to 10(-7)M. In contrast, values of 10(-8)M for monosialogangliosides and 10(-6)-10(-5)M for di- and trisialogangliosides were found. From estimations of hydrodynamic radii, Svedberg coefficients, and partial specific volumes, relative masses of glycosphingolipid micelles were calculated to be in the range of 300 to 1000 for the neutral glycosphingolipids and 100 to 350 for the gangliosides.