Biomedical subjects

E Hellwig

Publications and source records attributed to E Hellwig.

At least 55 records · Page 3Linked to original sources

PubMed1997

Effect of fluoride treatment on remineralization of bleached enamel.

The objective of the study was to evaluate the remineralizing capacity of different fluoride treatments on dental enamel bleached with carbamide peroxide (Opalescence). Sixty bovine enamel slabs were subjected to four cycles comprising bleaching (12 h) and remineralization in artificial saliva (8 h). The samples were evenly distributed among four groups (A-D). During the first hour of the remineralization period the specimens in Group A were covered with a fluoride varnish (Duraphat; 2.23% F-). In group B the enamel slabs were stored in a fluoride solution (0.2% F- as NaF) for 1 min prior to remineralization. Group C did not receive a fluoride treatment, and group D (control) was stored in distilled water instead of bleaching. Microhardness (VHN) was evaluated before the experiments and after the second and fourth cycle, respectively. Final hardness was calculated as percentage of the initial hardness. Analysis of variance was applied to the data followed by pairwise comparisons with corrected level of significance (P < 0.01). Hardness decreased significantly in groups A-C compared to the control group (D). The bleached and unfluoridated specimens (group C) showed a significantly higher hardness loss compared to the fluoridated specimens, whereas no significant difference was observed between the two fluoridated groups. It is concluded that remineralization of bleached enamel is improved by application of highly concentrated fluorides.

Analysis of Variance↗

PubMed1997

Irradiation effects on microhardness of fluoridated and non-fluoridated bovine dentin.

The objective of this study was to evaluate the effects of irradiation on microhardness of dentin. Dentin blocks from the cervical region of bovine incisors were treated as follows: (1) no irradiation; (2) irradiation of specimens up to 60 Gy (2 Gy/day, 5 days/week); (3) no irradiation, but fluoridation of specimens for 5 min/d; (4) irradiation of specimens and daily fluoridation. Knoop hardness number (KHN) of the control specimens was 62.63+/-14.75 (mean+/-SD). This was significantly different from the irradiated dentin samples (8.74+/-2.59 KHN). Hardness of the fluoridated dentin specimens was 11.19+/-1.95 KHN in the non-irradiated group and 10.03+/-2.76 KHN in the irradiated groups, respectively. Within the limitations of an in vitro study, it is concluded that dentin is severely affected by irradiation. This could be an explanation for the frequently observed side-effects of irradiation like loss of enamel, gap formation at the amelodentinal junction, and caries of the cervical region. Fluoridation with acidic gels decreases microhardness of dentin surface, and does not prevent softening due to radiation, when saliva is absent.

Animals↗

PubMed1996

Influence of enamel conditioning on bond strength of resin-modified glass ionomer restorative materials and polyacid-modified composites.

This study evaluated enamel bond strength of restorative materials containing both glass ionomer and composite components. Three resin-modified glass ionomer restorative materials (Fuji II LC, Vitremer, Photac-Fil), three polyacid-modified composites (VariGlass VLC, Dyract, Ionosit Fil), a hybrid composite (blend-a-lux) and a chemical-cured glass-ionomer cement (ChemFil Superior) were tested for enamel tensile bond strength with and without conditioning of the tooth surfaces. Tensile bond strength was determined for five specimens each of conditioned and unconditioned bovine teeth. Specimen conditioning was performed as recommended by the manufacturers. The tensile bond strength was tested with a universal testing machine. Except for the enamel bond strength of ChemFil Superior, all materials showed greater adhesion to conditioned tooth surfaces than to unconditioned specimens. Enamel bond strengths of the polyacid-modified composites applied after a phosphoric acid etching technique (Ionosit Fit, Dyract, VariGlass) were greater compared with the materials applied after surface conditioning with polyacrylic acid-containing agents. No significant difference was observed between the hybrid composite and the tested materials attached with the phosphoric acid etching technique. To improve adhesion of the tested materials to enamel, following the manufacturer's instructions about tooth surface conditioning is recommended. Superior bond strength to enamel was obtained for polyacid-modified composites, which are attached with the phosphoric acid etching technique and thereby resemble the adhesion patterns of composites.

Acid Etching, Dental↗

PubMed1996

Properties of resin-modified glass-ionomer restorative materials and two polyacid-modified resin composite materials.

The objective of the study was to evaluate the physical properties of four resin-modified glass-ionomer cements (Fuji II LC, Ionosit Fil, Vitremer, Photac-Fil) and two polyacid-modified resin composite materials (Dyract and Variglass VLC)). They were compared with a hybrid resin composite (blend-a-lux) and a chemically cured glass-ionomer cement (ChemFil Superior). The compressive strength, flexural strength, modulus of elasticity, and surface microhardness of the resin-modified glass-ionomer materials and the polyacid-modified resin-composite materials were inferior to those of the hybrid resin composite and similar to those of the conventional glass-ionomer cement. The hybrid resin composite exhibited the lowest resistance to wear caused by brushing. Some of the materials showed a marked decrease in hardness at depths exceeding 2.0 mm. Generally, the strength properties of the tested resin-modified glass-ionomer materials and the polyacid-modified resin composite materials were inferior to those of the hybrid resin composite.

Chemical Phenomena↗

PubMed1996

Salivary fluoride content after toothbrushing with a sodium fluoride and an amine fluoride dentifrice followed by different mouthrinsing procedures.

The aim of the present study was to determine the salivary fluoride content after toothbrushing with a sodium fluoride and amine fluoride dentifrice followed by two different mouthrinsing procedures. Twenty-four dental students took part in this six-treatment, six-period study with a cross-over design. They brushed their teeth with an amine fluoride, a sodium fluoride, and a non-fluoridated dentifrice. After toothbrushing the subjects spat out the saliva/dentifrice slurry and underwent one of the following procedures: 1) mouthrinsing with 20 ml distilled water; 2) no mouthrinsing after spitting out. Whole saliva samples were collected before (baseline), 10 and 90 min after toothbrushing and mouthrinsing, respectively. Fluoride analysis was performed with a fluoride-sensitive electrode. Both dentifrices caused an elevated fluoride level in saliva after brushing. Use of the amine fluoride dentifrice resulted in higher salivary fluoride contents compared to the sodium fluoride toothpaste. However, this difference was statistically significant only 90 min after toothbrushing when preceded by mouthrinsing after brushing. Mouthrinsing with water after brushing led to significantly lower fluoride levels compared to the non-rinsing technique 10 min after brushing. Mouthrinsing after toothbrushing with fluoride dentifrices reduces the salivary fluoride concentration of both an amine and a sodium fluoride dentifrice.

Adult↗

PubMed1996

Influence of dentin conditioning on bond strength of light-cured ionomer restorative materials and polyacid-modified composite resins.

The purpose of the study was to evaluate the dentin bond strength of restorative materials containing both glass ionomer and composite resin components. Three resin-modified glass ionomer restorative materials (Fuji II LC, Photac-Fil, Vitremer), three polyacid-modified composite resins (Dyract, Ionosit Fil, VariGlass VLC), a hybrid composite (blend-a-lux) and a chemical-cured glass ionomer cement (ChemFil Superior) were investigated for dentin tensile bond strength with and without conditioning of the tooth surfaces. For each material, tensile bond strength was determined using five conditioned and five unconditioned bovine tooth specimens. Conditioning of the specimens was performed according to the manufacturers' instructions. The tensile bond strength was tested with a universal testing machine. Statistical analysis was performed with analysis of variance, the Scheffe's-test and the Student's t-test. All materials showed higher adhesion to conditioned dentin than to unconditioned specimens. Except for Photac-Fil, the bond strength to conditioned dentin of all resin-modified glass ionomer restorative materials and polyacid-modified composite resins was higher as compared to the chemical-cured glass ionomer and the hybrid composite. However, these differences were not statistically significant. All polyacid-modified composite resins resulted in higher bond strengths to conditioned dentin as compared to the resin-modified glass ionomer restorative materials. These differences were statistically significant only for VariGlass VLC as compared to Photac-Fil. In order to improve adhesion of the tested materials to dentin it is highly recommended to follow the manufacturers' instructions concerning dentin conditioning.

Acrylic Resins↗

PubMed1995

Fluoride retention of incipient enamel lesions after treatment with a calcium fluoride varnish in vivo.

The aim was to determine the fluoride retention in plaque-covered and clean incipient enamel lesions after topical application of a CaF2/NaF varnish (Bifluorid 12). In 50 specimens of bovine enamel an incipient lesion was produced with acidic hydroxyethylcellulose (pH 4.8; 72 h). 40 specimens were fluoride varnished; the 10 remaining specimens were used for measuring baseline fluoride content. Each six of the fluoridated specimens were recessed in the buccal aspects of an intraoral appliance worn for 5 days. During the experimental period one side of the appliance was kept clean, and plaque growth was allowed on the other. KOH-soluble and structurally bound fluoride were determined immediately, 1 day, 3 days and 5 days after fluoridation, and compared with the baseline fluoride content of the enamel. Immediately after fluoridation, a considerable amount of KOH-soluble fluoride was bound, but after 5 days 80% had been lost. Simultaneously a significant increase of non-KOH-soluble or structurally bound fluoride was detected in both plaque-covered and clean enamel. It is evident that this CaF2/NaF varnish deposits more KOH-soluble fluoride on the surface of demineralized enamel than other varnishes, but after 5 days fluoride retention is similar to that from other varnishes.

Analysis of Variance↗

PubMed1995

Plaque surface area after rinsing with a low-level fluoride-containing Darjeeling tea.

Plaque surface area after rinsing with a tea, containing low levels of fluoride, was evaluated in 30 human volunteers with a single-blind, one-operator, three-period, three-treatment cross-over study. The mouthwashes employed were: (1) tea (Darjeeling first flush:< 0.2 ppm F-), (2) Meridol(R), (3) control (tap water:< 0.2 ppm F-). During the experiment the participants refrained from oral hygiene procedures and rinsed their mouth three times a day after each meal with 20 ml of the respective rinse. After 3 d standardized photographs were taken of the upper canines and premolars and the plaque areas were measured planimetrically. Statistical analysis showed a marked decrease in plaque surface area after rinsing with Meridol, whereas no difference in plaque surface area was observed after mouthrinsing with tea and tap water, respectively.

Adolescent↗

PubMed1995

[Mercury release from separated amalgam after the use of different disinfectants].

Set amalgam, annealed for twelve days, was cut with water cooling and sucked into eight dental units (Systematica 1062 T), equipped with an amalgam separator (Multisystem Type 1). Disinfection of the suction devices was performed with seven commonly used disinfectants according to the manufacturer's guidelines. Rinsing with water served as a control in the last experimental series. The waste water was collected at the beginning of the experiments and after disinfection. Repeating the experiments for seven times resulted in 112 specimens that were analyzed by atomic absorption spectrophotometry. The use of Green & Clean M2 and S & M matic resulted in very low releases of mercury. Disinfection with Alprojet D and Alprojet DD M2 was comparable with the control group. The release of mercury was significantly increased, if compared to Green & Clean and S & M matic (p < or = 0.05). The use of Orotol Ultra, Aseptoclean 2, and Tiutol resulted in significantly higher releases of mercury, if compared to all other disinfectants (p < or = 0.05). Disinfectants containing oxidizing agents provoke an increasing release of mercury, thus accumulating the amounts of mercury in the general environment.

Analysis of Variance↗

PubMed1995

Endodontic therapy in a postirradiated child: review of the literature and report of a case.

Exodontia of extremely carious teeth leads to a significant risk of osteoradionecrosis in patients who have undergone radiotherapy. In these patients, endodontic treatment could be an alternative. Successful root canal therapy in a girl who had been irradiated for head and neck neoplasms is reported. The results indicated that use of calcium hydroxide to obturate the root canals is a viable method of postirradiation endodontics in primary teeth.

Animals↗

PubMed1995

The relative caries-inhibiting efficacy of amine fluoride and sodium fluoride in compatible dentifrices--results of a consensus conference.

A conference concerning the caries-inhibiting efficacy of dentifrices that contain amine and sodium fluorides compared relevant clinical studies and found that both fluoride compounds contribute to the maintenance of dental health. Because of the differing test conditions, the study results cannot, however, be compared. Thus, there is no definite scientific proof of the superiority of one fluoride compound, and no such proof will exist until dentifrices containing amine fluoride and sodium fluoride are tested in a direct clinical comparison.

Amines↗

PubMed1993

[Does the application of a fluoride lacquer modify the de- and remineralization of initial carious lesions in vitro?].

Bovine enamel specimens with artificial initial lesions were fluoridated with a fluoride lacquer (Duraphat) for 6 hours. Subsequently artificial plaque (Streptococcus mutans, FA1) was grown on the enamel blocks in an artificial mouth. During the experimental period (23 days) the specimens were continuously rinsed with synthetic saliva and with sucrose twice daily. Nonfluoridated specimens served as controls. At the end of the experiment microhardness was evaluated in three levels parallel to the enamel surface. In addition, the concentration of KOH-soluble and structurally bound fluoride was determined. In the fluoridated specimens microhardness increased in levels near the surface of the lesion, but decreased in the next two lower levels. However, in the nonfluoridated enamel specimens microhardness decreased in all three levels and was more pronounced compared to the fluoridated specimens. At the end of the experiment no KOH-soluble fluoride could be determined on the surfaces of the artificial lesion. In contrast, structurally bound fluoride was significantly increased in the fluoridated specimens. A single application of the fluoride lacquer on initial enamel lesions resulted in remineralization of the outer enamel layers even under persisting cariogenic conditions. However, lesion progression could not be inhibited totally.

Animals↗

PubMed1992

Fluoride retention in dentin after topical application of aminefluoride.

The retention of KOH-soluble and structurally bound fluoride in dentin after topical application of aminefluoride was investigated. One cylindrical dentin sample was prepared from each of 40 extracted third molars. All samples received one topical application of 1 microL of aminefluoride solution (1.23% F) for three min. Ten of them were analyzed immediately after fluoridation. The remaining 30 samples were mounted in the buccal aspects of a special mouth application which was carried by a person for five days. After one, three, and five days, 10 of the 30 samples were removed from the appliance. In all samples, the amount of structurally bound fluoride was determined in three layers (20 microns, 20 microns, 20 microns) by use of a special grinding technique. Before each grinding step, the dentin specimens were analyzed for KOH-soluble fluoride. The total amount of KOH-soluble fluoride in dentin was 48.7 +/- 14 micrograms/cm2. It decreased drastically during the experimental period. Structurally-bound fluoride increased one day after fluoridation in the first and second layers. Thus, topical application of aminefluoride resulted in a significant accumulation of KOH-soluble fluoride in dentin. This precipitate was unstable, but fluoride ions released from it could perhaps increase the amount of structurally bound fluoride.

Amines↗

PubMed1991

[Primary accuracy of fit of composite inlays produced according to the indirect method].

The primary accuracy of fit of three composite inlay systems was evaluated comparatively. Control inlays were made of a phantom metal. In the proximal-cervical surfaces the resulting median widths of the open margins showing luting agent were as follows: EOS (74.1 microns) greater than Ful-Fil (59.5 microns) greater than Brilliant (43.13 microns) greater than Phantom metal (18.6 microns). Even though, under clinical conditions, composite inlays are attached by means of adhesives, the primary accuracy of fit achieved should be comparable to that of cast restorations, because the long-term stability of the material used for fasting the inlays cannot be warranted.

Composite Resins↗

PubMed1991

[Effects of an incremental application technique on the polymerization of two light-activated composite filling materials].

The influence of the use of an incremental technique on the polymerization depth of two light-activated composite resins (hybrid composite resin, microfilled composite resin) was investigated in vitro. Of each of the two materials specimens were produced using variable increments and different polymerization times. Polymerization depth was determined by means of a microhardness tester (Vickers hardness). At the bottom of the cavity hardness values were significantly higher in samples produced in small increments (2 mm) than in samples with thicker layers (3 mm). A polymerization time of 20 s resulted in a significantly poorer polymerization at the bottom of the cavity than longer polymerization times. Hardness values decreased within each layer from the surface to the bottom. Irrespective of the material and the duration of illumination SEM pictures showed the presence of a line in the interface of the layers. The use of incremental technique in class II restorations resulted in differently polymerized zones that are exposed to the varying conditions of the oral cavity.

Composite Resins↗

PubMed1990

[In situ fluoride uptake of initial caries lesions following application of two children's toothpastes].

Cylindrical blocks of enamel with initial caries lesions were brushed twice a day for 6 days using amine fluoride or monofluorophosphate children's toothpaste (250 ppm F-). Some of the enamel samples were left in the oral cavity for three further days after the end of the trial, during which time a fluoride-free toothpaste was used for daily oral hygiene. Half of the enamel blocks showed plaque formation during this period. The other half were kept clean. Fluoride soluble in KOH was only detected on the enamel blocks that had been brushed with amine fluoride children's toothpaste. The amount of solidly bound fluoride was significantly higher following the use of amine fluoride children's toothpaste than with monofluorophosphate children's toothpaste. The amounts of KOH-soluble fluoride and solidly bound fluoride fell again 3 days after discontinuation of fluoride application. But only the drop in the amount of KOH-soluble fluoride in demineralised tooth enamel after application of the two children's toothpastes can be explained by the differing reaction mechanisms of the two fluoride compounds.

Dental Enamel↗

PubMed1990

[Identification of children with high risk of caries related to caries occurrence in the past].

In several studies high correlations were found when the prevalence of caries in the past was correlated with future caries risk in children and adolescents. The practical value of this method for the identification of children with high risk for caries can be assessed by measurement of the ability of the method to recognize subjects who will develop caries (sensitivity) and to exclude those who will not (specificity). Taking into consideration worldwide studies from recent years the problems of this method were pointed out and discussed.

Child↗

PubMed1990

[Mercury release of silver amalgam fillings in vitro].

In vitro mercury release from silver amalgam fillings was analyzed by ICP (Inductively-coupled-plasma-atomic-emission-spectroscopy). Within 14 days 63.2 micrograms Hg and 41.5 micrograms Hg respectively, were released from unfinished and finished amalgam fillings (n = 5). The amounts of mercury found in this study were several times higher compared with the results from other in vitro-studies.

Dental Amalgam↗