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Biomedical subjects

H Gilde

Publications and source records attributed to H Gilde.

At least 19 recordsLinked to original sources
PubMed2004

In vitro investigation of marginal accuracy of implant-supported screw-retained partial dentures.

Mismatch occurring during the fabrication of implant-supported dentures may induce stress to the peri-implant bone. The purpose of this study was to investigate the influence of two different alloys and the fabrication method on the marginal accuracy of cast partial dentures. Two laboratory implants were bonded into an aluminium block so that the distance between their longitudinal axes was 21 mm. Frameworks designed for screw-retained partial dentures were cast either with pure titanium (rematitan) or with a CoCr-alloy (remanium CD). Two groups of 10 frameworks were cast in a single piece. The first group was made of pure titanium, and the second group of a CoCr-alloy (remanium CD). A third group of 10 was cast in two pieces and then laser-welded onto a soldering model. This latter group was also made of the CoCr-alloy. All the frameworks were screwed to the original model with defined torque. Using light microscopy, marginal accuracy was determined by measuring vertical gaps at eight defined points around each implant. Titanium frameworks cast in a single piece demonstrated mean vertical gaps of 40 microm (s.d. = 11 microm) compared with 72 microm (s.d. = 40 microm) for CoCr-frameworks. These differences were not significant (U-test, P = 0.124) because of a considerable variation of the values for CoCr-frameworks (minimum: 8 microm and maximum: 216 microm). However, frameworks cast in two pieces and mated with a laser showed significantly better accuracy in comparison with the other experimental groups (mean: 17 microm +/- 6; P < 0.01). (i) The fit of implant-supported partial dentures cast with pure titanium in a single piece is preferable to that of those made with the CoCr-alloy and (ii) the highest accuracy can be achieved by using a two-piece casting technique combined with laser welding. Manufacturing the framework pieces separately and then welding them together provides the best marginal fit.

Bone Screws↗
PubMed2001

Color stability of highly filled composite resin materials for facings.

OBJECTIVES: The aim of the investigation was to examine the color stability of seven resin-based facing composites with a high content of inorganic filling material (Colombus, Artglass, Sinfony, Targis, Zeta LC, Zeta HC, BelleGlass HP/dentine, BelleGlass HP/enamel). METHODS: Changes in color of test samples were determined after UV irradiation in a fast-action UV instrument, Sunset CPS+, and after storage in a mouthrinse, tea, coffee, red wine and a 0.1% turmeric (curcuma) solution. Color differences were measured by using a Castor colorimeter and the total amount of color difference represented as DeltaE. RESULTS: Red wine and the turmeric solution caused the most severe cases of discoloration (DeltaE>10). Tea, coffee, the mouthrinse and UV irradiation caused invisible (DeltaE<1) or visible (DeltaE>1), and to some extent clinically unacceptable (DeltaE>3.3), discoloration. SIGNIFICANCE: It is apparent from the results that it remains essential to improve the color stability of the composite resin materials used for facings.

Color↗
PubMed1991

[The stability of orthodontic treatment results].

A posttreatment evaluation of 72 patients, who are approximately 5.8 years out of retention, showed only little changes between the last appointment and the follow-up examination. The results can be considered stable. The statistic analysis indicated a correlation among some changes, which are important for treatment and therapy planning. For the stability in transversal and sagittal direction a maximal intercuspidation of the premolars and molars is as important as the exact positioning of the canines with lateral contacts in the dental arch. Transversal over-expansion should be avoided, because those results cannot be stabilized in the postretention period. The functional adaptation of muscles, the abolishment of habits and the duration of retention are essential preconditions for a stable treatment result.

Adolescent↗
PubMed1991

[Study of pressure resistance of galvano-crowns].

Ceramic veneered galvano crowns demonstrated an axial loading limit of 220 N on incisors and of 297 N on canines. Compressive strength values are only slightly lower at 45 degrees loading. These use of a bonding agent did not significantly affect strength.

Chromium Alloys↗
PubMed1989

[Comparison of two powder-stream systems for tooth polishing].

The effect of two airpolishing systems on the surface roughness of polished ceramic test pieces was compared and evaluated using standardized procedures. Test pieces resembling enamel in hardness were treated with these air-polishing systems. Using a Perthometer surface roughness was found to increase significantly. Thus the possible effects of airpolishing systems on the enamel surface should be considered. Efficiency of extrinsic stain removal was studied by SEM and documented. Photographic techniques provided information on the homogeneity of the sodium bicarbonate spray.

Bicarbonates↗
PubMed1989

[Experiments on abrasion and wear of dental diamond instruments].

In spite of identical ISO standards for shape, grain size, and largest head diameter of diamond abrasive instruments there are major differences in the machining performance among the various makes. These differences are largely due to variations in shape and diamond partical size. Diamond burs from different manufacturers of the same visual shape and particle size do not show any significant differences in performance. However, not only the abrasive performance but to a greater extent the design of the preparation margin determine the selection of a bur. It would be desirable that manufacturers be more specific about the particle size used and the shape of the bur, since the ISO standard does not include sufficiently accurate data about diamond particle size and shape design. The life of a diamond instrument is limited by the wear of its tip. Here the diamond layer wears off faster than on the rest of the instrument. This calls for early replacement of the instrument in clinical use even if the shaft still might be functionable.

Carbon↗
PubMed1989

[Studies on the compressive strength of ceramic veneers].

Ceramic veneers were constructed following either a chamfer or a shoulder preparation (with rounded internal line angles). In laboratory tests both veneer forms displayed adequate compressive strengths. A beveled incisal finish line proved to be slightly superior to complete incisal coverage.

Aluminum↗
PubMed1980

[Elasticity of secondary cone crowns made of fusing alloys].

Deformations under stress due to production-related fitting inaccuracies were measured in nonfaced and faced secondary cone crowns. During the tests, four of the 40 tested crowns developed cracks in the ceramic facing. No chipping was observed. Loaded free-end cone crowns withstood 1 mm settling at the distal end of the structure for more than 5,000 stress applications. Defects were first noted when the amount of settling exceeded 1.2 mm.

Biomechanical Phenomena↗