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Biomedical subjects

L Seppä

Publications and source records attributed to L Seppä.

At least 37 records · Page 2Linked to original sources
PubMed1994

Fluoride release and effect on enamel softening by fluoride-treated and fluoride-untreated glass ionomer specimens.

The effect of fluoride application on fluoride release and enamel protection was studied using conventional and light-activated glass ionomers and composite. The specimens prepared from the materials were tested as (1) freshly mixed, (2) aged (29 days), (3) aged and fluoride treated, and (4) aged, fluoride treated, and aged (29 days). For fluoride application, the specimens were immersed in 1.2% NaF solution for 10 min and washed. After handling, the specimens were glued on polished bovine enamel slabs and immersed in lactic acid (pH 5.0) for 3 h. The microhardness of the enamel was measured before and after the acid immersion. Freshly mixed glass ionomers significantly prevented enamel softening. The effect disappeared (conventional glass ionomer) or decreased (light-activated glass ionomer) during aging, but was reestablished by fluoride application. After the subsequent 4 weeks of aging, no significant protective effect could be seen for either of the glass ionomers. The fluoride release, which was greatly increased by fluoride application, was still elevated after 4 weeks of aging for both materials.

Animals↗
PubMed1994

Professional topical fluoride applications--clinical efficacy and mechanism of action.

All currently used topical fluoride agents deposit soluble fluoride as calcium fluoride on enamel or in lesions. Calcium fluoride serves as a source of fluoride for the formation of fluorapatite. The latter phase is formed when pH drops in plaque, not during topical application. The potential for calcium fluoride formation should probably be increased in topical fluoride agents. In countries with low caries prevalence, the clinical recommendations for topical fluoride need to be reconsidered. Toothpaste is the basic fluoride regimen recommended for everybody. The need for additional fluoride supplementation depends on caries activity. There is no distinct difference in the caries-preventive effects of concentrated fluoride solutions, gels, or varnishes. Thus, the choice of method depends on costs, convenience, patient acceptance, and safety. The use of fluoride varnishes has proven to be a feasible and safe method of fluoride application. With fluoride varnishes, the amounts of fluoride exposure can be better controlled, and less chair-time is required compared with conventional solutions and gels. No dose-response effect to concentrated fluoride agents is apparent, and the benefit of frequent application is not clearly established. In individuals with the most severe cariogenic challenge, combinations of fluoride and antimicrobials may give better clinical effects than fluoride alone.

Calcium Fluoride↗
PubMed1993

The effect of different strontium concentrations on the efficacy of chlorhexidine-fluoride-strontium gel in preventing enamel softening in vitro.

The effects were compared of strontium concentrations of 0, 15, 50 and 250 parts/10(6) in chlorhexidine(0.20%)-fluoride(0.16%) gel in preventing the softening of bovine enamel during bacterial fermentation. Fresh Streptococcus sobrinus cells were suspended in a buffer solution (pH 6.0) with 3.3% sucrose and centrifuged as a plaque-like layer on the top of enamel slabs covered with 10 microliters gel. AFter 24 h incubation, the pH fall of the fluid was significantly smaller in all test groups than in the placebo group. Strontium seemed to have an inhibitory effect on the pH fall. All test gels significantly prevented softening and dissolution of enamel during bacterial fermentation, which was directly related to strontium concentration. The amounts of calcium and phosphorus in the cells and fluid after incubation were the smallest in the group with 250 parts/10(6) strontium. In a second experiment without bacteria, new enamel slabs were covered with 10 microliters gel containing chlorhexidine and NaF with 0 and 250 parts/10(6) strontium to study the protective effect of strontium. After 24 h gel treatment, each enamel slab was dissolved in 1 ml 0.1 M lactic acid, pH 5.0, for 2 h. Significantly less calcium and phosphorus were dissolved from the enamel in both test groups than in the control and placebo groups. However, the placebo gel also prevented calcium and phosphorus dissolution significantly. These results suggest that the addition of strontium to chlorhexidine-fluoride gel improves the ability of this combination to prevent caries-like enamel softening. The inhibition of bacterial acid production by the strontium-containing gel may explain this enhanced protection of enamel.

Administration, Topical↗
PubMed1993

The effect of fluoride application on fluoride release and the antibacterial action of glass ionomers.

The aim of this study was to investigate whether the release of fluoride and the antimicrobial effect of freshly mixed glass ionomers could be prolonged by application of fluoride on aged material. Test slabs of freshly mixed and aged (14 d in water) conventional and silver glass ionomer (Ketac-Fil and Ketac-Silver, Espe, Seefeld, Germany) and composite (Silux Plus, 3M, St. Paul, MN) were fitted into the bottom of a test tube. A layer of S. mutans Ingbritt cells was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% sucrose solution. After the incubation, pH, F, and Ca contents of the fluid phase, and F, Mg, P, and K contents of the cells were determined. The aged glass-ionomer samples were then covered with toothpaste (0.1% F) or with fluoride gel (1.25% F), and the composite samples with fluoride gel. After being thoroughly rinsed, S. mutans cells were incubated on the samples as above. The pH fall was significantly inhibited by freshly mixed glass ionomers, and there were changes in cellular cation and phosphorus contents. Large amounts of fluoride were found in the fluid and cells. For old glass ionomers, no inhibitory effect on pH fall could be seen. Fluoride release had decreased to a low level.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Enamel and plaque fluoride following glass ionomer application in vivo.

Glass ionomer fillings have been suggested to act as a fluoride-releasing system in the mouth. The aim of the present study was to evaluate whether a glass ionomer slab applied on the enamel can increase the fluoride content of the enamel and plaque of adjacent teeth in real-life conditions with frequent exposure to fluoride from other sources. Twenty-five adults living in a town with fluoridated drinking water participated in the study. The initial enamel fluoride content on the buccal surface of the contralateral premolars was determined using the acid etch biopsy technique. A round glass ionomer slab was placed buccally on the first molar on a randomly chosen side of the mouth (test side). After 2 weeks, the enamel fluoride content of premolars on the test and control sides was again determined whilst avoiding the site of the first biopsy. In addition, one biopsy was made on a previously etched area. After 2 and 4 weeks, plaque was collected from three approximal surfaces both on the test and control side, and the total fluoride content of the plaque was analysed. There were no significant differences in the fluoride content of sound or etched enamel before and after placement of glass ionomer. The fluoride content of approximal plaque of teeth close to glass ionomer was not higher than that of the control teeth, either after 2 or 4 weeks. Using the present method, no increase in the fluoride level of teeth adjacent to glass ionomer could be demonstrated. This may be due to the masking effect of fluoride from other sources.

Adult↗
PubMed1992

Effect of different glass ionomers on the acid production and electrolyte metabolism of Streptococcus mutans Ingbritt.

In order to study the effects of different glass ionomers on the metabolism of Streptococcus mutans, test slabs of freshly mixed conventional glass ionomer (Fuji), silver glass ionomer (Ketac-Silver), composite (Silux), and 2-week-old Fuji were fitted into the bottom of a test tube. A plaque-like layer of S. mutans strain Ingbritt was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% (w/v) sucrose solution. For freshly mixed Fuji and Ketac-Silver, the pH fall was significantly smaller than for old Fuji and composite. These materials also released the largest amount of fluoride into the fluid phase. Incubation with glass ionomer materials led to an increase in the cellular concentration of fluoride in bacteria, but intracellular fluoride did not correlate with the fall in pH. The lowest pH was associated with the lowest cellular magnesium content. Ketac-Silver released large amounts of calcium in the fluid phase, and the cellular calcium content was doubled in this group. The results show that freshly mixed glass ionomers affect acid production and electrolyte metabolism of S. mutans in vitro. The effect of conventional glass ionomer, however, seems to disappear after a few weeks. The effects of calcium and silver released by cermet glass ionomer deserve further study.

Acids↗
PubMed1991

In vitro abrasion resistance and hardness of glass-ionomer cements.

The aim of this study was to compare the abrasion resistance and surface hardness of four glass-ionomer cements. The effects of hydration and dehydration on wear resistance were also studied. A composite material, enamel, and dentin were used as controls. For wear testing, the specimens were abraded on abrasion discs under water. All glass ionomers showed greater wear than composite and enamel, but less wear than dentin. Ketac-Fil showed the highest and Ketac-Silver the lowest wear resistance. Hydration or dehydration of the specimens did not significantly influence the wear rate of conventional glass ionomers, but the wear resistance of Ketac-Silver was increased due to dehydration. Ketac-Fil had the highest and Ketac-Silver the lowest hardness rating of the glass ionomers. The cement material did not show abrasion resistance better than that of the conventional glass ionomers, as has previously been suggested.

Cermet Cements↗
PubMed1991

Effect of intensified caries prevention on approximal caries in adolescents with high caries risk.

The aim of this study was to evaluate the effect of two preventive programs carried out in Public Dental Clinics for children with high caries risk. From all the 13-year-olds living in Kuopio (n = 871), 323 (37%) were selected as a high-risk group on the basis of the level of salivary mutans streptococci or DS score. They were randomly divided into two groups. The first group continued with the preventive care they had received before the study. The dentists treating the children in the second group were specifically informed about their high caries risk, and instructions concerning intensified prevention were given. For comparison, half of the 13-year-olds with low caries risk were included in the study (group 3, n = 248). No special instructions concerning these children were given. After 2 years, approximal caries increment in the two risk groups was three times that of the low-risk group (2.6, 2.3 and 0.7 in groups 1-3, respectively). There was no significant difference between the two risk groups in spite of the fact that significantly more preventive procedures were provided for group 2 than for group 1. The results indicate that assessment of the subjects as high and low-risk groups was successful, but caries prevention targeted for the risk groups failed to lower the rate of caries to the same level as that of the children with an anticipated low risk. For children at high risk, the intensified prevention program monitored by dental authorities was no more successful than prevention planned by individual dentists.

Adolescent↗
PubMed1991

Fluoride and mutans streptococci in plaque grown on glass ionomer and composite.

The aim of this study was to compare the levels of fluoride and mutans streptococci in plaque grown on glass ionomer (Ketac-Fil) and composite (Silar) restorations in vivo. From tunnels left under the brackets bonded either with glass ionomer or composite, 14-day-old plaque samples were collected 14, 28, and 42 days after bonding. For glass ionomer the mean counts of mutans streptococci in plaque were 0.5 x 10(3), 6.7 x 10(3), and 8.8 x 10(3) CFU at the first, second, and third collection, respectively, whereas for composite restorations the corresponding values were 32.1 x 10(3), 14.6 x 10(3), and 120.6 x 10(3) CFU. For glass ionomer the mean concentrations of fluoride were 19,985, 5,788, and 5,019 ppm at first, second, and third collections of 14-day-old plaque samples, respectively, whereas for composite restorations the mean concentrations of fluoride were about 200 ppm throughout the study. The results show that the fluoride level in plaque growing on glass ionomer is much higher than that on composite restorations which seems to affect the level of mutans streptococci in dental plaque.

Acrylic Resins↗
PubMed1991

Plaque accumulation on glass ionomer filling materials.

It has been suggested that fluoride released by glass ionomers inhibits the growth of plaque. The aim of this study was to compare plaque accumulation on glass ionomers and composite. The materials tested were (1) freshly mixed glass ionomer (Ketac-Fil), (2) artificially aged glass ionomer (Ketac-Fil), (3) freshly mixed silver glass ionomer (Ketac-Silver) and (4) light-cured hybrid composite (Valux). Ten volunteers wore an acrylic appliance for three periods of 18 hours, one for each glass ionomer. A glass ionomer disk was inserted on one randomly chosen side of the appliance and the composite disk on the other. The volunteers rinsed once an hour with a 15% sucrose solution. The amount of pellicle and plaque on the disk was estimated by analysing its protein content. During each cycle, more plaque accumulated on the glass ionomers than on the composite (fresh Ketac-Fil/Valux p less than 0.05, aged Ketac-Fil/Valux p less than 0.01, Ketac-Silver/Valux NS). On examination using a scanning electron microscope the surfaces of the glass ionomers were found to be markedly more porous, and to contain more microbes, than the composite surface. The presence of silver in the silver glass ionomers may have affected the initial adherence of bacteria.

Adult↗
PubMed1991

Studies of fluoride varnishes in Finland.

Despite the artificial fluoridation of drinking water in Kuopio, part of the children have high caries incidence. We therefore started our studies on fluoride varnishes in 1977 in an attempt to find a feasible means of applying fluoride topically in children at high risk of caries. In our first trial, the sodium fluoride varnish Duraphat was found to be effective in preventing caries, but the effectiveness of the silane fluoride varnish Fluor Protector could not be unequivocally established, despite the fact that Fluor Protector deposited markedly more fluoride in enamel than Duraphat. In a second study in children in a low-fluoride area, use of Duraphat was found to be more effective than fortnightly fluoride rinses or Fluor Protector. Increasing the frequency of application from two to four times a year did not increase the effectiveness of Duraphat even in highly caries-prone children in a 2-year trial. On the basis of peak values of fluoride in parotid saliva after application, use of either fluoride varnishes was considered safe. Although the fluoride content of the enamel remained elevated for at least two years after discontinuation of treatment with both varnishes, the caries preventive effect did not continue after the applications were stopped. This shows that increasing the fluoride content of enamel is not the main mechanism by which fluoride varnishes prevent caries, and that the applications need to be continued as long as caries is a problem.

Adolescent↗
PubMed1990

Caries preventive effect of fluoride varnish applications performed two or four times a year.

The efficacy of Duraphat varnish applications performed two or four times a year was compared in a 2-yr clinical trial. 254 children aged 9-13 yr and having higher than average DMFS values participated in the study. The children were randomly divided into two treatment groups. Clinical and radiographical examinations were performed at baseline and after 2 yr by one dentist. For the group receiving applications every 3 months, the 2-yr DMFS increment was 2.90 (SD 4.45) and for the group receiving applications every 6 months, 2.92 (4.47). There were no significant differences in DMFS increments between the groups for any type of tooth surfaces. Neither was there any difference between the groups when the children were divided into two subgroups on the basis of baseline DMFS values. The increments for the children with high (greater than or equal to 10) baseline DMFS values were 4.25 (4.81) and 4.30 (5.53) in the groups receiving applications four times and twice a year, respectively. The results suggest that fluoride varnish applications performed more frequently than twice a year may not provide additional caries protection in a population with relatively low caries activity.

Adolescent↗
PubMed1990

Prevention of enamel demineralization adjacent to glass ionomer filling materials.

In order to study the release of fluoride and prevention of enamel demineralization by different filling materials, standardized cavities were prepared in 80 extracted human molars. The cavities were filled as follows: 1. Fuji II F; 2. Ketac-Fil; 3. Ketac-Silver; 4. Silar. Twenty molars were used as controls (no filling). Enamel slabs with the fillings were subjected to 9 days of demineralization (30 min daily) and remineralization (artificial saliva, replaced daily). Fluoride release in the saliva was determined on days 1, 3, 5, and 9. Enamel fluoride content adjacent to the cavities was determined initially and after the de-remineralization using the acid etch technique. On day 1, the largest amount of fluoride in the saliva was released by Fuji, but on day 9 the largest amount was released by Ketac-Fil. Ketac-Silver released significantly less fluoride than Fuji and Ketac-Fil. The average initial fluoride content of enamel was 2200 ppm. After the test period, fluoride contents adjusted for biopsy depth were 1822, 1690, 1693, 1337, and 888 ppm in groups 1-5, respectively. The amounts of phosphorus dissolved by the second acid etch were 28.9 (SE 2.6), 30.2 (2.0), 34.4 (2.8), 44.1 (2.7), and 42.2 (2.4) micrograms, respectively. Softening of surface enamel during the test period was clearly reduced in teeth filled with Fuji and Ketac-Fil. The results show that glass ionomer materials release considerable amounts of fluoride and prevent demineralization of the adjacent enamel in vitro. Fuji and Ketac-Fil seem to be more effective than Ketac-Silver.

Acrylic Resins↗
PubMed1990

Short-term retention of glass-ionomer fissure sealants.

In some studies, rapid loss of glass-ionomer sealants has been reported. The aim of this study was, therefore, to examine the retention rate of 4 month old glass-ionomer sealants (Fuji III). The sealants were applied in 93 newly erupted molars and premolars. After four months, 75% of the sealants were totally present, 22% partially lost and 3% totally lost. No caries was observed. Impressions were taken from occlusal surfaces showing total or partial loss of sealants, and the casts were examined using a stereomicroscope or SEM. Examination revealed that in most of these cases, the material was still left in the bottom of the fissures. This may partly explain why glass-ionomer sealants have prevented caries even after they appear to have been lost. In order to examine the penetration of the sealant into the fissures, 28 teeth were sealed in vitro, bisected and examined using a stereomicroscope. In 19 cases, the sealant had penetrated whole fissure, in 7 cases two thirds of the fissure and in 2 cases one third of the fissure or less.

Adolescent↗
PubMed1989

Wear of dental restorative and prosthetic materials in vitro.

The aim of this study was to evaluate the wear of some modern materials for fixed crown and bridge restorations and fillings in vitro. Eighteen commercial materials (8 composites, 4 alloys, 4 façade materials, and 2 denture-base resins) were tested. Enamel was used as the control. Test specimens were abraded on abrasion discs under water or in artificial saliva. There was a great variation in the wear rates of the tested materials. The greatest wear was shown by resins used for base material and the smallest by gold and Cr-Co alloys and porcelain. Most of the composites had a wear rate near that of enamel. The wear for amalgam was slightly greater than for most of the composites. When one is using several different materials for reconstructing occlusion, differences in wear resistance should be taken into account.

Dental Materials↗
PubMed1989

Past caries recordings made in Public Dental Clinics as predictors of caries prevalence in early adolescence.

The aim of the present study was to evaluate the power of past caries experience in primary and permanent dentition in predicting caries prevalence at the age of 13 yr. Clinical and radiographical examination was performed in 512 13-yr-olds by a trained research team. The 6-12-yr dmfs and DMFS values were obtained from the Public Dental Care records. For evaluating the accuracy of predictions, the children were cross-classified according to each past caries score and the 13-yr score. The cutting points were selected to that the children in the upper quartile of caries experience formed the predicted and true high caries groups, leaving about 75% in the low caries groups. Pearson correlations were also calculated. Sensitivity and specificity of caries in primary teeth (6 yr) were 57% and 85%, respectively. For permanent dentition, sensitivity was the lowest (28%) at the age of 6, reached 68% at the age of 9 and remained at that level until age 12. Specificity decreased from 92% (6 yr) to 85% (9 yr) and then steadily increased to 93% (12 yr). Correlation increased with age from 0.37 to 0.82. When screening for high caries increment in young children, caries in primary dentition seems a better screening criterion than caries in permanent first molars. When the aim is to identify those subjects with high caries increment later on, screening at age 9 seems as accurate as that done later.

Adolescent↗
PubMed1989

Protection by F, I, Sr, and combinations against fermentation attack by Streptococcus sobrinus artificial plaque on bovine enamel.

Labial surfaces of 64 bovine incisors (8 teeth/treatment) were subjected to 1-min treatment with (1) 500 ppm Sr, (2) 0.5% I2 plus 1% KI solution, (3) F varnish treatment (Duraphat) for 24 h, or (4) combined treatments. The treated teeth were incubated under an artificial Streptococcus sobrinus plaque for 10 days. The 'oral fluid' with maleate buffer (pH 5.8) partially saturated with Ca3(PO4)2 and with or without 3.3% sucrose or sucrose plus 25 ppm F, was replaced by a mixture containing thioglycolate broth and the buffer for 4 h daily. This was done in an attempt to maintain the viability of the plaque as it was not renewed. Analysis of the Ca and inorganic P in the fluid phase taken after the 1st and the 10th day of incubation indicated that complete protection was obtained with F varnishing plus 25 ppm F in the fluid, with added sucrose. The Sr plus F treatment was more protective than F or Sr alone. The iodine treatment was slightly protective when combined with F varnishing. The results of the enamel surface and subsurface F and Sr as well as measurements of surface microhardness also indicated the highest protective effect with the double-F treatment and a marked protection provided by the Sr plus F treatment. The efficacy of the double-F treatment was partly explained by the prevention of a fall in 'plaque' pH and partly by the release of bacterial inorganic P in the extracellular fluid. The present caries model is versatile in quantification of changes in numerous parameters (14 parameters measured) involved in the caries-like process and its inhibition.

Acid Etching, Dental↗