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Biomedical subjects

G Oilo

Publications and source records attributed to G Oilo.

At least 55 records · Page 3Linked to original sources
PubMed1985

Replica techniques for in vivo studies of tooth surfaces and prosthetic materials.

In order to obtain a replica technique suitable for a complete or segments of a dental arch two different impression materials were combined with two epoxy resin model materials. The models were examined and photographed in an optical microscope and a scanning electron microscope. No systematic differences were found between the used combinations of materials except a tendency towards greater contraction of one of the model materials. The A-silicone impression materials combined with one of the epoxy resin material seemed to be the easiest to handle and to give the best models.

Calcium Sulfate↗
PubMed1985

Porosities in a dental silver-palladium casting alloy.

Twelve single crowns were cast in a silver-palladium alloy by six different casting techniques. Polished sections of the crowns were inspected and photographically recorded by light microscopy. The area of the inspected section of the casting and the number and area of pores were recorded on the photographs by means of a digitizing table connected to a microcomputer. A great number of defects were observed unevenly distributed in all castings. Only small variations were observed between the various casting techniques.

Crowns↗
PubMed1984

Clinical study of two luting cements used on student-treated patients: an interim report.

A long-term clinical test has been started to compare a zinc phosphate with a polycarboxylate cement as luting materials for crowns and fixed partial dentures. The present report includes an evaluation of two groups of student-treated patients regarding their suitability for this type of testing, as well as certain clinical and radiographic criteria recorded 6 and 18 months after insertion of the restorations. No significant differences were observed regarding the composition of the patients or the type of treatment. No loosening of restorations and no differences between the two groups in other respects such as subjective complaints, clinical symptoms, carious lesions, or periapical changes were observed. So far, both cements seem equally suitable as luting materials.

Adult↗
PubMed1984

Early erosion of dental cements.

The disintegration in water of various unset glass ionomer cements, a polycarboxylate and a zinc phosphate cement was measured gravimetrically after exposure of the cements to a constant water jet. The test gave reproducible results with significant variations between the various types and brands of cements. For zinc phosphate and polycarboxylate cements, no weight loss was observed in the period from 4 to 8 min after commencement of mixing. All the glass ionomer cements showed a significant loss of weight at 4 min and a somewhat reduced weight loss at 6 min after start of mixing. Two cements, a filling and a luting material, showed reduced weight when exposed to a water jet even 8 min after start of mixing. The early erosion as recorded in the present study conforms with the setting of the glass ionomer cements.

Chemical Phenomena↗
PubMed1983

Dental casting alloys with a low content of noble metals: physical properties.

Several physical properties such as strength (UTS and fracture and proof stress), modulus of elasticity, strain (elastic and plastic elongation), hardness, and hardening ability were determined for five low-gold alloys and two conventional gold casting alloys (types III and IV). The composition and the structure (pores and defects) of the cast tensile test specimens were also studied. The results showed that alloys with a low content of noble metals could have properties comparable to those of the traditional types III and IV dental gold casting alloys. A marked difference was seen in the plastic elongation (ductility). A great number of defects (pores and oxide inclusions) were also observed, especially in the specimens with a high content of both palladium and silver.

Chemical Phenomena↗
PubMed1982

A novel miniature bite force recorder and its clinical application.

Solid state components were used to construct a miniature bite force recorder suitable for registrations in large study groups. A semiconductor was chosen as the sensory unit. The complete recording system included a power supply, the bite force recorder, a chart recorder and a millivoltmeter. Laboratory calibration tests were performed to screen the limitations of the recorder. Series of loads were applied in the range from 10 to 1000 N. Eight females and eight males, 20 to 25 years old, were asked to produce a succession of maximum bites at three second intervals for as long as possible. The bite force recorder was positioned between the first molars on the left side. The laboratory tests showed that loads in the range from 10 to 1000 N were recorded with an error less than four percent. In the clinical tests, the mean maximal bite force was 500 N ranging from 330 to 680 N. The number of maximum bites varied from 5 to 27. No statistically significant differences were observed between the sexes as regards the maximal bite force and the number of bites.

Adult↗
PubMed1982

The effect of asbestos-alternatives on the accuracy of cast veneer crowns.

The effect of three different lining materials on the investment expansion during the casting procedure, was compared. The accuracy of the castings was assessed by measuring slits at the gingival shoulder of a cast veneer crown. The liners were made of asbestosos, paper and a glassfiber material. They were used with a gypsum bonded and a phosphate bonded investment material using a regular type III and a high-fusing alloy. The glass-fiber material seemed to give a good and reproducible accuracy with both investments. The effect of this liner seemed to be comparable or better than that of the conventional asbest material. The paper liner sometimes allowed a sufficient expansion, but with varying results. Additional problems were connected to this material as it was burnt to ash during the mould heating procedure.

Asbestos↗
PubMed1981

Bond strength of porcelain to dental alloys - an evaluation of two test methods.

Two methods for measuring shear strength of the porcelain-metal interface, a rod/disk-push test and a cube/cube-push test, were compared using the same metals and porcelain material. Both types of specimen showed evidence of complex stress distribution at the interface during loading and a fracture line located mainly in the opaque porcelain layer. Both methods were thus mainly a test of the "strength" of the porcelain at the interface. The "bond strength values" obtained with the rod/disk specimen seemed to depend on the geometry of the specimen and the values obtained with the cube/cube specimen seemed to depend on the quality of the porcelain work. It seems questionable whether "bond strength values" as obtained with these two methods can be the basis for requirements in a standard for porcelain-metal systems.

Chemical Phenomena↗
PubMed1981

Bond strength of new ionomer cements to dentin.

The bond strength of two glass ionomer and two polycarboxylate cements to dentin was compared in vitro. The results showed that a new luting type of the glass ionomer cements had an increasing bond strength with increasing storage time in water. After 3 d the values were comparable to those obtained for the polycarboxylate cements. It was also shown that the breakage of bond was due to a cohesive failure of the cement. The glass ionomer cements seem to be sensitive to moisture during setting.

Chemical Phenomena↗