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Biomedical subjects

G M Lösche

Publications and source records attributed to G M Lösche.

8 recordsLinked to original sources
PubMed2000

Marginal integrity of large compomer Class II restorations with cervical margins in dentine.

OBJECTIVES: The aim of the present study was to investigate the marginal integrity of total-bond Dyract AP restorations in large Class II restorations with cervical margins in dentine. The efficacy of a new non-rinse conditioner and the effect of beveling the enamel margins were also studied. METHODS: Large MOD cavities with cervical margins located 1mm below the CEJ were prepared in 48 extracted human molars. Six groups (n=8) were filled using a total-bond technique with Spectrum TPH or Dyract AP or a sandwich technique with Dyract in combination with Spectrum TPH. For Dyract AP total-bond restorations, a new non-rinse conditioner was tested vs. a total-etch with 36% phosphoric acid in beveled and butt-joint cavities. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were produced for quantitative marginal analysis in the SEM. Afterwards, teeth were immersed in 0.5% basic fuchsin for 24h and dried. Percent dye penetration over the total margin length was analysed in three layers using a sequential grinding technique. Statistical analysis was performed with non-parametric tests and the Bonferroni correction for multiple comparisons at p<0.05. RESULTS: All restoration types showed microleakage. On cervical margins in dentine, Dyract AP restorations showed better marginal adaptation than Spectrum TPH total-bond restorations (marginal openings (MO), median 33.8 vs. 79.6%), but were inferior to Dyract/Spectrum TPH sandwich restorations (MO: 0. 0%). The non-rinse conditioner improved the marginal adaptation of Dyract AP restorations in dentine (MO: 4.7 vs. 38.4%, p=0.0206 for beveled cavities, 12.2 vs. 33.8%, p=0.0238, for butt-joint cavities) and yielded similar results in enamel margins provided that enamel margins were beveled. Beveling of enamel significantly reduced the occurrence of enamel microcracks. CONCLUSIONS: The use of a non-rinse conditioner in combination with Dyract AP may improve the marginal adaptation of Class II restorations compared to composite restorations. The sandwich technique with Dyract results in better marginal adaptation in cervical dentine compared to all other restorative techniques tested in this study. However, microleakage cannot predictably be prevented with the sandwich technique.

Acid Etching, Dental↗
PubMed1999

Marginal adaptation of direct composite and sandwich restorations in Class II cavities with cervical margins in dentine.

OBJECTIVES: The aim of this study was to evaluate the marginal adaptation of direct Class II sandwich restorations with resin-modified glass-ionomer cements and compomers in comparison to base and total bond restorations. For sandwich restorations with a triple cure resin-modified glass-ionomer cement the influence of different light curing techniques was also evaluated. METHODS: Large butt-joint class II cavities with cervical margins 1 mm below the cemento-enamel junction were cut into 120 extracted human molars. The cavities (15 groups, n = 8) were filled using a sandwich, base or total bond technique with materials from five different manufacturers. A three-sited light curing technique was used in 13 groups. For the material combination Vitremer/Z100 two additional groups with a different wand positioning and a metal matrix were evaluated. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were quantitatively analysed in the SEM. Statistical analysis was performed with the Kruskal-Wallis test and the Bonferroni test at p < 0.05. RESULTS: The marginal adaptation of vertical enamel margins was not dependent on the restorative technique. For margins in dentine, marginal adaptation was significantly better with the sandwich technique than with a base or total bond technique for all materials. There were no significant differences between the base and total bond technique. Overall, resin-modified glass-ionomer cements showed somewhat better results than compomers in sandwich restorations, though differences were not significant for some criteria. Vitremer/Z100 sandwich restorations applied with a metal matrix showed the highest mean percentage of excellent margins of all experimental groups. CONCLUSIONS: Both resin-modified glass-ionomer cements and compomers can improve the marginal quality when used in a sandwich technique. Further research is necessary to determine the ideal material combination for sandwich restorations.

Compomers↗
PubMed1999

Marginal adaptation of Class II composite fillings: guided polymerization vs reduced light intensity.

PURPOSE: To improve the marginal adaptation of Class II composite fillings, a three-sited light-curing technique was proposed by Lutz et al in 1986 and has proven to be effective in several studies. This study investigated whether this effect, attributed to guided polymerization towards the cavity margins, might also be due to the decreased polymerization stress resulting from reduced curing light intensity caused by transdental curing. MATERIALS AND METHODS: Forty extracted human molars were mounted in casts and 40 Class II slot-type cavities were cut (cervical margins 0.5 mm above the CEJ). To measure the light being transmitted from a halogen curing light onto a composite layer within a cavity, miniature photodetectors were used and irradiance measured for a three-layer technique (1st: cervical-horizontal; 2nd and 3rd: lateral-diagonal) with occlusal or three-sited curing. To evaluate the influence of light intensity on marginal adaptation, the prepared cavities were treated as follows: after base placement and acid etching, the cavities were filled with Herculite XR (Kerr, Romulus, MI, USA) in three increments. All cavities were filled with the layering technique described above. In two groups (n = 10), curing was carried out only from occlusal. In the remaining groups, the cervical composite layer was cured through a light-transmitting, lateral reflective wedge, and the following layers transdentally with a proximal wand positioning. Using the photodetectors, the output power of an argon laser was adjusted so that the composite was cured with the equivalent irradiance calculated for occlusal (high-intensity groups) and three-sited curing occlusal (low-intensity groups). Replicas were produced after storing in water for 21 days and thermocycling (2000x, 5 degrees C to 55 degrees C). The margins of the fillings were quantitatively assessed using a SEM at 200x. The results were statistically analyzed (ANOVA, Bonferroni/Dunn; p < 0.05). RESULTS: The summed values for the criteria "restoration margin fracture", "enamel margin fracture," and "marginal opening" at the cervical margins were 11.3 +/- 11.5 (three-sited curing, low intensity), 14.1 +/- 15.7 (occlusal curing, low intensity), 25.4 +/- 21.2 (three-sited curing, high intensity), and 27.8 +/- 30.6 (occlusal curing, high intensity). CONCLUSION: No significant difference was found between curing techniques at equal energy levels; the effect of the three-sited light curing technique should therefore not be attributed to guided polymerization but to the reduction of light intensity.

Analysis of Variance↗
PubMed1994

Dye penetration in root canals filled with AH26 in different consistencies.

It is recommended that the powder to liquid ratio of AH26 be very high and that the mixture be warmed to decrease viscosity before insertion into the root canal. In this study, the effectiveness of the powder to liquid ratio and temperature were assessed using 60 root canals of maxillary central incisors randomly divided into four groups after their cleaning and shaping. The teeth were obturated by either lateral condensation or the single-cone technique using AH26 warmed or at room temperature. After exposure to basic fuchsin, the teeth were embedded and cross-sectioned using a diamond saw. The dye penetration was measured microscopically and reported as a percentage of the total circumference of the filling of each slice using a goniometric eye-piece. After statistical analysis, it was concluded that AH26 in combination with lateral condensation leads to less leakage when used at room temperature.

Bismuth↗
PubMed1993

Inlays and onlays.

Dentists must meet the increased demands of patients for esthetic dentistry. Because the substitution of amalgam with direct composite restorations is somewhat problematic and restricted to special indications only, the most suitable method is the esthetic inlay. All available systems are reviewed and described. These restorations must be inserted with adhesive techniques. The performance and the problems associated with these techniques are described in detail. Improvements in luting techniques, eg, the use of ultrasonic energy, may further simplify the application technique for esthetic inlays. For clinical success, the margin quality of adhesively luted inlays is essential. In vitro and in vivo studies with esthetic inlays report good clinical behavior of such restorations. However, until the results of long-term clinical studies are available, these systems should not be used on a routine basis as a substitute for amalgam.

Composite Resins↗
PubMed1991

[Opacity and opacity changes in composites].

The opacity of 5 self-curing and 11 light-curing composite resins was measured 24 hours after sample/preparation and after 6 months of storage (dry or in water) by means of an UV-visible spectrophotometer. The opacity of the investigated hybrid composite resins was between 47.3 and 62.4%. The opacity of the microfilled composite resins ranged from 48 to 64.4%. The opacity was not influenced by the polymerization time. The spectral opacity decreased with greater wavelengths, particularly in microfilled composite resins. All materials except Durafill, which became more translucent, were more opaque after 180 days of storage in water. Storage in water for 180 days caused greater changes of the opacity than dry storage for the same time. The opacity changes resulting from storage in water can be reduced by increasing the polymerization time.

Analysis of Variance↗
PubMedDate not supplied

Influence of dentin conditioning and contamination on the marginal integrity of sandwich Class II restorations.

This study investigated the influence of dentin conditioning and contamination on the marginal adaptation of Class II sandwich restorations. Large butt-joint MOD cavities with cervical margins located 1 mm below the CEJ were cut into 72 extracted human molars. Nine groups were filled using a total-bond technique with Z100 or a sandwich technique with either Vitremer or F2000 in combination with Z100. For all three material combinations three different pretreatments were compared: total etch, selective etch and dentin contamination with saliva and blood prior to primer/adhesive application. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C) replicas were produced for quantitative marginal analysis in the SEM. Teeth were immersed in 0.5% basic fuchsin for 24 hours and dried. Percent dye penetration over the total marginal length was analyzed in three layers using a sequential grinding technique. Statistical analysis was performed using a two-way ANOVA. Post-hoc analyses were carried out with univariate Mann-Whitney-U-tests adjusting for multiple comparisons by a sequentially rejective test procedure (Bonferroni-Holm) at p < 0.05. Both F2000 and Vitremer sandwich restorations showed better marginal adaptation than Z100 total-bond restorations with all pretreatments. Acid etching of the dentin significantly influenced the marginal adaptation of Z100 total-bond restorations and Vitremer sandwich restorations. All types of restorations showed considerable microleakage. On contaminated dentin, sandwich restorations showed better marginal integrity than total-bond restorations. Marginal adaptation did not correspond with microleakage in all groups. In conclusion, F2000/Z100 and Vitremer/Z100 sandwich restorations show better marginal adaptation than Z100 total-bond restorations in large Class II cavities with cervical margins in dentin. Microleakage cannot predictably be prevented with the sandwich technique. Sandwich restorations seem to be less sensitive to contamination with saliva and blood.

Acid Etching, Dental↗