Fluoride release and uptake by glass-ionomers and related materials and its clinical effect.

The anticariogenic effect of silicate cement is well known and considered a result of fluoride release. In several studies a similar fluoride release from conventional glass-ionomer cement (GIC) has been established. Therefore, an anticariogenic effect may be predicted from the GICs too. In my studies the fluoride release was studied by exposing the test specimens to a continuous flow of running tap water. At certain time periods the specimens were transferred for 1 week in a small amount of deionized water (5 ml). The determination of the fluoride content of the solution showed the fluoride release of the material at that time. There was an initial 'burst' effect of fluoride release and then the release gradually decreased, settling at a constant level. The long-term release from conventional GICs was shown to remain on the same level for at least 8 years. The amount of the constant release did not differ much between different brands. Resin-modified GICs released fluoride to the same extent and in the similar way as conventional GICs whereas polyacid-modified composites ('compomers') did not show an initial fluoride 'burst' effect. To study the fluoride binding ability of GICs, specimens which had been exposed to running water for different periods of time were treated with a 50 ppm fluoride solution. After this 'recharging' GIC and resin-modified GIC specimens released more than twice the amount of fluoride released before the treatment. The fluoride treatment had no effect on polyacid-modified composites or on fluoride-containing composites or on the amalgams. To get an impression of the clinical effect of GICs a questionnaire was handed out to practitioners attending courses in the Nordic countries and in Australia during the period 1991-1992 which resulted in 954 answers. Among other questions, the dentists were asked if they had observed caries and gingival inflammation in association with GIC and composite fillings. According to the opinion of most dentists caries and gingival inflammation had never or only seldom been observed in association with GIC fillings whereas most dentists had observed these complications often in connection with composite restorations.

Resin-modified glass ionomer cements: fluoride release and uptake.

The aim was to study the short- and long-term fluoride release from resin-modified glass ionomer cements (GIC). The aim was also to determine the effect of fluoride treatment of 9-month-old specimens, consistency of the mix, and pH of the environment on the fluoride release. GIC test specimens were continually exposed to running water, and the fluoride release was measured periodically by storing the specimens in 5 ml deionized water for 1 week and measuring the fluoride content of the solution. After 24 h, 1 month, 9 months, and 11 months in running water four of the six resin-modified GICs released as much as or more fluoride than the auto-curing GIC tested for comparison. Fluoride treatment after 9 months also increased the fluoride release of these four brands, as was the case with the conventional GIC. At 24 h and 1 month two of the resin-modified GICs released smaller amounts of fluoride than the other materials, and the fluoride treatment used on those had no or only a minimal effect. Thin consistency of a mix resulted in higher fluoride release for one resin-modified material than a thick mix. Low pH increased the fluoride release for all materials.

Observations in Australia of the use of glass ionomer cement restorative material.

The aim of this study was to evaluate, with the aid of a questionnaire distributed to selected groups of dentists, the use of glass ionomer cement in different types of proximal restorations and further to evaluate any complications observed with the use of GIC. Few dentists responded in the 'Often' category regarding the observation of secondary caries or gingival inflammation in association with GIC fillings compared with about three-quarters of the dentists who reported on posterior composite resin restorations. Tunnel cavities had been prepared and restored by 54 per cent of the dentists, simple proximal restorations in primary molars by 89 per cent and 'sandwich' restorations by 69 per cent. Few dentists with at least two years experience with tunnel restorations observed biological complications, but fracture of the marginal ridge was reported in the 'Often' category by 12 per cent. Among the dentists with at least five years experience with proximal restorations in primary molars 59 per cent of the operators mentioned more complications with these than with amalgam restorations. Biological complications were not a great problem with glass ionomer/composite laminates but wear or dissolution of the proximal GIC surface was recorded in the 'Often' section by 14 per cent of those placing them.

Clinical experience with glass ionomer for proximal fillings.

The aim of this study was to evaluate, with the aid of a questionnaire handed out to a selected group of dentists, the use of glass ionomer cement (GIC) in different types of proximal preparations. The aim was to evaluate the experience of complications associated with the use of GIC. Very few had often observed secondary caries or gingival inflammation in association with GIC fillings, compared with about 70% of the dentists in association with posterior composites. Tunnel fillings had been made by 60% of the dentists, simple proximal fillings in primary molars by 80%, and sandwich restorations by 80%. Few dentists with at least 2 year's experience with tunnel fillings had observed biologic complications, but ridge fractures had often been observed by 10%. Among the dentists with at least 2 years' experience with proximal fillings in primary molars, 40% mentioned more complications with these than with amalgams. Biologic complications were also not a great problem with GIC/composite sandwich restorations, but wear or dissolution of the proximal GIC surface was often seen by 17% of the dentists.

Short- and long-term fluoride release from glass ionomer based liners.

The aim of the study was to measure the fluoride release from glass ionomer based liners/bases after storing the specimens for 24 h and for 6 months in running water. The fluoride release was greater in the beginning than after half a year. From most liner materials the initial and the long-term release was greater than from the glass ionomer filling material studied for comparison. From two liners the release was minimal, just at the detection limit.

Fluoride release and uptake by glass ionomers.

The aim was to study the fluoride release 1) from 7 and 15-month-old glass ionomer specimens after treating them with fluoride; 2) from fresh compared with matured material; and 3) from specimens stored for 29 months in running water. Glass ionomer test specimens which had been in running water for first 7 then 15 months were treated with a 50 ppm fluoride solution after which the specimens were again exposed to running water for first 24 h and then 1 wk. The fluoride release was measured after each of the two periods of time. The fluoride treated specimens released more fluoride than the nontreated ones. This effect was not observed with composite resin specimens which were studied for comparison. Fluoride release from fresh glass ionomer specimens was observed to be 3-10 fold compared to specimens that had matured for 3 days. The release of fluoride from specimens that had been in running water for 29 months was measured and the results were compared with those of earlier measurements. It was found that the release reached a constant level for all tested glass ionomers during the second year.

Short- and long-term fluoride release from glass ionomers and other fluoride-containing filling materials in vitro.

Test specimens of seven different glass ionomer filling materials and one fissure sealant were exposed to running water for 2 yr. One amalgam and one composite, both containing fluoride, were included for comparison. The fluoride release from the specimens was measured periodically after storing the specimens for 24 h or 1 wk in a small amount of water. The fluoride release from the glass ionomers decreased with time and a constant level was reached for most products during the 2-yr period. The release was increased by lowering the pH of the storage solution. The release from the glass ionomers was clearly greater than from the amalgam and the composite.

Glass ionomers in proximal cavities of primary molars.

Proximal cavities with or without a dovetail were prepared in primary molars of 5-7-yr-old children. The cavities were filled with either a traditional glass ionomer (Ketac-Fil) or a cermet (Ketac-Silver). A total number of 199 treated teeth were available for evaluation 5-14 months after placement of the fillings. The percentage of success was 84% for Ketac-Fil and 77% for Ketac-Silver. There was no clear difference in rate success between the two different types of cavities.

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.

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.