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Biomedical subjects

L Forsten

Publications and source records attributed to L Forsten.

At least 37 records · Page 2Linked to original sources
PubMed1984

Bond between subsequently added light activated composite resin and hardened material.

Because of the limited depth of cure, subsequent layers frequently have to be cured separately in connection with large fillings of light activated composite resins. This method is successful only provided that the different layers adhere to each other. Rectangular rodlike specimens of four light activated composites, two macro- and two microfilled brands, were made in three pieces cured separately (test specimens). The transverse strength of these specimens was compared with that of specimens made in one piece (controls). The strength of both test and control specimens of the macrofilled brands was the same even when water contamination was included when preparing the test specimens. In connection with the microfilled brands there was an indication of lower strength, at least after water contamination.

Chemical Phenomena↗
PubMed1984

The alkaline and antibacterial effect of seven Ca(OH)2 liners in vitro.

The alkaline effect of seven Ca(OH)2 liners was studied, using extractions with unbuffered 0.9% NaCl solutions and buffered bacterial growth media. The antibacterial effect was studied by cultivating Streptococcus mutans in the presence of liner specimens. All liners made the NaCl solutions strongly alkaline (pH greater than 10), although MPC and Reolite released much less Ca than did Dycal, Life, Procal, Renew, and Reocap-E. The weaker alkaline effect of MPC and Reolite was shown by the extractions with the growth media. Consequently, these two liners were not able to prevent the growth of Str. mutans. No growth was observed in the presence of the other five liners, and the media remained alkaline during the 12-h incubation period. Regrowth of the bacteria grown in the presence of these effective liners showed that only Dycal could be considered bactericidal, whereas the four other liners acted bacteriostatically.

Alkalies↗
PubMed1984

Curing depth of visible light-activated composites.

Three composites, two microfilled (Heliosit and Silux) and one macrofilled (Prisma-Fil), were exposed to visible light from three different light units. The depth of the cure was estimated by measuring the length of the test specimen after removing the uncured material. The macrofilled composite cured to a greater depth than the microfilled materials. The curing depth of Heliosit was lower, of Silux about the same, and of Prisma-Fil higher than the values of curing depth given by the manufacturers. The shade of the pastes influenced the curing depth of the macrofilled more than that of the microfilled composites. Doubling the exposure time increased the curing depth by about 1/3. Exposure through tooth substance reduced the curing depth by at least 1/3. The curing effectivity of Prisma-Lite was slightly greater than that of Heliomat and the 3M unit.

Color↗
PubMed1980

Sealing of preventively enlarged fissures.

The occlusal fissures of 156 permanent first molars in 63 children, 7--8 years of age, were sealed with a chemically polymerizing material (Delton). Deep and narrow fissures were opened up with a pointed diamond before etching and sealing. The treatment was performed by untrained dental students. The patients were called back for treatment every 6 months. 2/3 of the patients were followed up for a period of 2 1/2 years. After that period the retention of sealants was 93% (74 sealants) in ground deep fissures and 88% (28 sealants) in unground shallow fissures.

Acid Etching, Dental↗
PubMed1978

Marginal leakage and consistency of the composite resin material in etched cavities.

The purpose of the study was to evaluate the degree of adaptation of undiluted and diluted composite resin to etched enamel walls with and without an intermediary resin. Cavities (O = 2 mm) were drilled in extracted teeth and the walls were etched with phosphoric acid. Fillings were made of Concise composite resin, without applying an intermediary resin (1), after applying the resin layer (2), after diluting the mix with one (3) or two (4) drops of catalyst resin but without an intermediary resin, and after diluting the mix and applying the resin layer (5). The fillings were ground flush with the tooth surface and the teeth were cycled thermally between two dye solutions baths. The marginal penetration of the dye was evaluated by measuring the discoloured portion of the margin at different depths using a stereomicroscope. The restorations with an intermediary resin (2 and 5) exhibited significantly less leakage than fillings without the intermediary layer (1, 3 and 4). When no resin layer was applied the dilution of the mix seemed to reduce the leakage compared with undiluted material but the differences were not statistically significant. The results indicate the advantage of using an intermediary resin with etching even when the composite is diluted.

Acid Etching, Dental↗
PubMed1977

Working time and strength in relation to consistency of composite resins.

Composite resin pastes can be made more fluid for injection purposes by adding small amounts of enamel bond resin before mixing. The aim of this work was to study the influence of the added resin on the working time and on the early and final strength of the composite. The pastes of two different brands diluted with their respective resins and the working time of the mix was determined by measuring the time during which it was possible to squeeze the material from a Centrix syringe. The results revealed that adding universal resin reduced the working time of both brands. The catalyst resin increased the working time of Adaptic but with Concise the amount of the catalyst paste had also to be increased to gain more working time. Adding catalyst resin did not affect the early strength or the strength after 24 h. Furthermore, it was observed that adding resin reduced the amount of porosities in the composite.

Composite Resins↗
PubMed1977

Fluoride release from a glass ionomer cement.

The release of fluoride from a glass ionomer cement (ASPA) was compared with that from a silicate cement. Test specimens were shaken in a solution with hydroxyapatite for 7 weeks. The solution was changed every week and the fluoride taken up by the hydroxyapatite measured. The specimens released considerably more fluoride during each of the first 2 weeks than during each of the subsequent 5 weeks. The continued release did not decrease very much with time. Slightly more fluoride was released from the glass ionomer cement than from the silicate.

Dental Cements↗
PubMed1977

Effect of a Ca(OH)2 solution and a chlorhexidine based detergent on the microbial activity of human carious teeth.

Occlusar carious lesions from human molars, preserved in continuous humidity after extraction, were removed using conventional clinical techniques. Bacteriological samples were taken after rinsing the cavity with water only, after experimentally infecting the cavity and after treating uninfected cavities either with a saturated Ca(OH)2 solution or with a chlorhexidine based detergent. The samples were cultivated on blood agar plates aerobically and anaerobically. Cavities rinsed with water only showed very sparce bacterial growth. After experimental infection the growth was significant, but decreased radically after treatment with the test materials. In order to describe the effect of the two test materials on the microbial enzyme activity in infected dentin, cryostat sections of 10 micrometer were prepared from undermineralized carious dentin fragments excavated from freshly extracted human teeth. Conventional histochemical techniques were applied to demonstrate the aminopeptidase activity in the sections using N-L-leucyl-2-naphthylamide as a substrate. The aminopeptidase activity of carious dentin was inhibited totally with the Ca(OH)2 solution, whereas the chlorhexidine based detergent had no effect on the enzyme activity.

Aminopeptidases↗
PubMed1976

Fluoride release from a fluoride-containing amalgam and two luting cements.

The release of fluoride from an amalgam and two luting cements, silicophosphate and polycarboxylate, was studied by shaking test specimens in a solution with hydroxyapatite, and measuring the fluoride taken up by the apatite. The initial release was significant for all three materials. After 1 week the amalgam released only minor amounts of fluoride, whereas the cements continued to liberate fluoride during the 5-week observation time to the same extent as silicates in earlier studies.

Dental Amalgam↗
PubMed1976

Fluoride uptake from restorative dental materials by human enamel.

The purpose of the study was to determine the uptake in vitro of fluoride from restorative materials by tooth enamel and whether prior etching of the enamel causes a change of uptake. The outermost layer of the labial surface of extracted canines was removed by grinding and the enamel was covered with five different fluoride-containing materials; a silicate, a composite resin, an amalgam, a silicophosphate, and a polycarboxylate luting cement. The material was either removed immediately or after storing the tooth in distilled water. The fluoride content was determined using a sensitive physical method based on the 19F (p,alpha gamma) 16 O reaction. In addition, the fluoride content of enamel after etching for different periods of time and of etched enamel which had been in contact with silicate cement was determined. The mean fluoride content of uncovered interior enamel was 226 parts/10(6). All materials, except the composite, increased clearly the fluoride content of the underlyaing enamal. Etching of interior enamel also increased the fluoride values. No difference could be shown in fluoride uptake from silicate and composite resin between etched and unetched enamel.

Acid Etching, Dental↗