Noninvasive control of dental caries in children with active initial lesions. A randomized clinical trial.

The aim of this study was to investigate whether DMFS increment can be decreased among children with active initial caries by oral hygiene and dietary counseling and by using noninvasive preventive measures. Except for mentally disabled and handicapped children attending special schools, all 11- to 12-year-olds in Pori, Finland, with at least one active initial caries lesion were invited to participate in the study and were then randomized into two groups. Children in the experimental group (n = 250) were offered an individually designed patient-centered preventive program aimed at identifying and eliminating factors that had led to the presence of active caries. The program included counseling sessions with emphasis on enhancing use of the children's own resources in everyday life. Toothbrushes, fluoride toothpaste and fluoride and xylitol lozenges were distributed to the children. They also received applications of fluoride/chlorhexidine varnish. The children in the control group (n = 247) received basic prevention offered as standard in the public dental clinics in Pori. For both groups, the average follow-up period was 3.4 years. A community level program of oral health promotion was run in Pori throughout this period. Mean DMFS increments for the experimental and control groups were 2.56 (95% CI 2.07, 3.05) and 4.60 (3.99, 5.21), respectively (p < 0.0001): prevented fraction 44.3% (30.2%, 56.4%). The results show that by using a regimen that includes multiple measures for preventing dental decay, caries increment can be significantly reduced among caries-active children living in an area where the overall level of caries experience is low.

Clinical study on the effect of professional cleaning of occlusal tooth surfaces on laser fluorescence measurements.

Manufacturer's advice is to professionally clean teeth before using a laser fluorescence (LF) device in order to avoid false-positive diagnoses. Professional cleaning is not included in routine dental check-ups in children in Finland because it is time-consuming. The aim of our present study was to evaluate the effect of professional cleaning of teeth on LF in children. A total of 642 occlusal surfaces in permanent molars and premolars in 9- to 16-year-olds (n = 46) were first examined visually. After that the first measurements with LF were made without cleaning the teeth. At the same appointment the second measurements were carried out after professional cleaning using a soft rubber cup and either polishing paste or plain water spray. The differences in LF of uncleaned and cleaned teeth were determined separately for teeth with a visual score of 0 (sound) and > 0. In premolars cleaning had no significant effect on LF. In molars, the values increased when the teeth were cleaned, the difference of the measurements being statistically significant in molars with visual score > 0 cleaned with plain water spray. For molars that were cleaned with paste, the differences were not statistically significant. Sealants did not modify the effect of cleaning. As a conclusion cleaning with a rotating instrument and water spray before LF measurements is recommended in teeth with visible plaque. Also in clean teeth, cleaning is advisable in cases where LF readings approach threshold level for operative intervention. The finding that uncleaned teeth gave lower values than cleaned teeth is opposite to what has been suggested.

A follow-up study of the use of DIAGNOdent for monitoring fissure caries in children.

OBJECTIVES: The aim of this study was to evaluate the utility of the laser fluorescence device DIAGNOdent for monitoring occlusal caries longitudinally as part of a routine dental check-up in a public dental clinic. METHODS: Children aged 7-8 and 13-14 years at baseline participated in the study. As part of two consecutive dental check-ups with a mean interval of 1,19, years, 423 permanent molars and 315 primary molars in 81 children were examined visually and using DIAGNOdent by one dentist. In teeth where, as judged by visual examination, caries had emerged or progressed during the follow-up, the DIAGNOdent values had increased significantly from the baseline. RESULTS: In permanent teeth with a change in visual score from sound to enamel or dentin caries, the mean DIAGNOdent value increased from 24 to 37 and in primary teeth from 8 to 40. The increase in DIANGOdent values correlated positively with the increase in visual score. The mean DIAGNOdent value at baseline was significantly higher in teeth that became carious than in those that remained sound during the follow-up. For permanent teeth with a visual reversal from inactive or active enamel caries to a sound surface, the mean DIAGNOdent value decreased from 36 to 24. CONCLUSIONS: These results suggest that DIAGNOdent is useful in monitoring occlusal caries in both permanent and primary molars.

Clinical study of the use of the laser fluorescence device DIAGNOdent for detection of occlusal caries in children.

Diagnosis of non-cavitated occlusal caries is generally considered problematic. The aim of this study was to evaluate the utility of the laser fluorescence device DIAGNOdent as part of routine dental check-ups in children. A total of 613 occlusal surfaces on permanent molars and 436 surfaces on primary molars in children aged 7-8 (n = 55) and 13-14 years (n = 54) were examined visually, using DIAGNOdent and for most 13- to 14-year-olds also using radiographs. The teeth were not cleaned professionally before examination. To provide a gold standard for carious teeth, the depth of the caries lesion was determined in those lesions that were judged visually to need opening by drilling (51 teeth). The higher the visual score, the higher were the mean DIAGNOdent values, but in each visual category the variation among values was large. The presence of a clear sealant did not affect DIAGNOdent measurements. The values for permanent and primary molars differed slightly. For permanent teeth, Youden's index value was highest (60%) at a cut-off value of 30, which indicates that the overall performance for DIAGNOdent in detecting dentinal caries was best at this point. Using this cut-off, sensitivity was 92% and specificity 69% with visual examination for validation, while sensitivity was 92% and specificity 82% with validation by fissure opening. Of the three methods, radiographic examination was the least accurate. In routine dental check-ups of children, DIAGNOdent appears to be useful as an adjunct to visual examination.

Caries occurrence in a fluoridated and a nonfluoridated town in Finland: a retrospective study using longitudinal data from public dental records.

The tap water of Kuopio, Finland, was fluoridated from 1959 to 1992. In the first decade of fluoridation, children in Kuopio had lower DMF values than children in Jyväskylä, a nearby low-fluoride town, but later differences between the towns have been small and inconsistent. The present study aimed to gain further insight into caries occurrence in Kuopio and Jyväskylä using longitudinal tooth-specific data from public health records on cohorts born in 1970/71 and 1980/81 (total n = 1,503). Survival analyses were used to summarize the tooth-specific times elapsed between eruption and the first filling (used as a proxy for dental caries). Generally, the first filling was placed sooner after eruption in the 1970/71 cohort than in the 1980/81 cohort. The curves for the two towns were virtually identical except for the first molars of the 1970/71 cohort, for which the percentage of filled first molars was consistently lower in Jyväskylä than in Kuopio. This study indicates that, among children and adolescents whose permanent teeth erupted in the mid-1970s or thereafter, even a longitudinal approach did not reveal a lower caries occurrence in the fluoridated than in the low-fluoride reference community. The main reason for the modest effect of water fluoridation in Finnish circumstances is probably the widespread use of other measures for caries prevention. The children have been exposed to such intense efforts to increase tooth resistance that the effect of water fluoridation does not show up any more. The results must not be extrapolated to countries with less intensive preventive dental care.

Dental check-up intervals and caries preventive measures received by adolescents in Finland.

OBJECTIVE: The aim was first to estimate the mean length of dental examination intervals and the mean number of preventive procedures in two Finnish towns during the periods of 1990-1992 and 1993-1995. Secondly, to ascertain whether the length of the check-up interval and the intensity of prevention varied according to the caries experience at the beginning of a treatment period. Participants A random sample of all 12- and 15-year-old children was drawn in 1992 and 1995 in the towns of Jyväskylä and Kuopio. METHOD: Oral health records obtained from public dental clinics were used for gathering the data on dental check-ups, DMFT and all preventive and treatment measures during the previous three years. The data were available for 267 and 590 subjects in 1992 and 1995, respectively. RESULTS: For 12-year-old children in 1990-1992, the mean length of check-up interval was 13.0 months in Kuopio and 12.4 months in Jyväskylä, while in 1993-1995 it was 18.1 months and 16.1 months, respectively. Among 15-year-old children in 1990-1992, the mean was 12.3 in Kuopio and 14.7 in Jyväskylä. During the latter period the interval was 1.2 months longer (P<0.05) in Kuopio, but there was no lengthening in Jyväskylä. Fluoride varnish applications, sealants, and instruction in oral hygiene were the most commonly used preventive measures. Practically no other fluoride methods than varnish applications were performed in dental clinics. Prevention seemed to be based mainly on procedures performed by the staff at the dental clinics and less attention was paid to the promotion of self-care. There was very little difference in the mean length of check-up interval and prevention between children who were caries free at the beginning of the treatment period and those with present or past caries experience. CONCLUSION: Between 1990-1992 and 1993-1995, the frequency of dental check-ups and the number of preventive procedures decreased. There was no indication of an increased caries frequency. Prevention appeared to be stereotyped and often had little relevance to the actual needs of the individual patient.

Caries data collected from public health records compared with data based on examinations by trained examiners.

Collecting data for dental caries studies is costly. In countries where uniform patient records are available for virtually the whole population, it is tempting to use them as a data source. Our aim was to compare data collected from patient records to those obtained by trained examiners. In 1992 and 1995, dentists who were specially trained and calibrated examined random samples of 12- and 15-year-olds living in two towns in Finland. The dental record of each child was obtained from public dental clinics, the dental status was entered into a computer file, and the DMFS value was calculated. Data were available for 824 children. In the two data sets, 1.3% of the tooth surfaces were recorded differently (DMF vs. sound) with the related kappa value being 0.70. In two thirds of the discrepancies, the reason was that a filling was marked in only one of them, which confirms the known difficulty in discerning a white filling. For 48% of the subjects, the DMFS values calculated from the two sets of data were equal. The difference was 1 and 2 surfaces for 28 and 11%, respectively. Public health dentists had almost equally often registered more and less DMF surfaces compared to trained examiners. The results suggest that data collected from public health records are not decisively inferior to those obtained from examinations by trained examiners. In large enough settings, data obtained from patient records could possibly be used as a replacement for separate surveys.

The future of preventive programs in countries with different systems for dental care.

From 1990 onward the decline of caries has leveled off in economically developed countries and the effectiveness of preventive programs seems to have diminished. The aim of this paper is to consider the future of caries prevention in the light of the studies conducted during the past decade. A shift from population-based prevention to a high-risk strategy has been promoted in countries where caries is strongly polarized. In Finland, however, an intensive preventive program targeted to high-risk individuals had little effect on caries increment, which suggests that the utility of a high-risk strategy is questionable. The relative effects of population-based methods have also decreased during the last decades. Although discontinuation of water fluoridation had no effect on caries in Kuopio, Finland, water fluoridation is still effective in countries with a lower level of basic prevention and a less homogenous social structure. From the standpoint of cost-effectiveness, the use of professionally applied fluoride gels has been questioned in children with a low caries rate, and the same is probably true for fluoride varnishes. In countries with a high caries rate, a low level of basic prevention, and an unorganized dental care system any preventive program seems to be effective. The importance of fluoride toothpastes as a cost-effective and feasible method of fluoride delivery is indisputable and will be so in all countries irrespective of the caries level and dental care systems. Population-based dental health education continues to be important, also in the countries where the caries rate has so far been low.

Caries trends 1992-1998 in two low-fluoride Finnish towns formerly with and without fluoridation.

Water fluoridation in Kuopio, Finland, was stopped at the end of 1992. In our previous study, no increase in caries was found in Kuopio 3 years after the discontinuation of water fluoridation. The aim of the present study was to further observe the occurrence and distribution of caries in Kuopio and Jyväskylä, which was used as the reference town for Kuopio. In 1992, 1995 and 1998 independent random samples of all children aged 3, 6, 9, 12 and 15 years were drawn in Kuopio and Jyväskylä. The total numbers of subjects examined were 688, 1,484 and 1,530 in 1992, 1995 and 1998, respectively. Calibrated dentists registered caries clinically and radiographically. No indication of increasing caries could be found in the previously fluoridated town during 1992-1998. In both towns the mean dmfs and DMFS values either decreased or remained about the same during the observation period. When all study years and both towns were pooled, 25% of the 12- and 15-year-olds with the highest DMFS counts accounted for 79 and 67%, respectively, of all affected surfaces. The mean numbers of fluoride varnish and sealant applications had markedly decreased in 1993-1998 compared to 1990-1992. The fact that no increase in caries was found in Kuopio despite discontinuation of water fluoridation and decrease in preventive procedures suggests that not all of these measures were necessary for each child.

Caries in the primary dentition, after discontinuation of water fluoridation, among children receiving comprehensive dental care.

UNLABELLED: The city of Kuopio in central Finland had fluoridated piped water for 33 years, beginning in 1959. Due to strong opposition by various civic groups, water fluoridation was stopped at the end of 1992. There is little information on the consequences of stopping fluoridation in a community with comprehensive dental care for all children and adolescents, who are frequently exposed to different fluoride measures both at home and in the dental office. OBJECTIVES: The aim of this repeated cross-sectional survey was to examine how discontinuation of water fluoridation in Kuopio affected caries in the primary dentition. Changes in the mean dmfs values between 1992 and 1995 in Kuopio were compared to those in Jyväskylä, a low-fluoride community that has repeatedly been used as the reference area for Kuopio. METHODS: In 1992 and 1995, independent random samples of all children aged 3, 6 and 9 years were drawn in Kuopio and Jyväskylä. The total number of subjects examined was 421 in 1992 and 894 in 1995. Calibrated dentists registered caries clinically and radiographically. RESULTS: In all age groups both in 1992 and 1995, the point estimates for mean dmfs values were lower in the non-fluoridated town. In both towns, the observed mean dmfs values were smaller in 1995 than in 1992. CONCLUSION: Despite discontinuation of water fluoridation, no increase of caries frequency in primary teeth was observed in Kuopio within a three-year period.

Application of the high-risk strategy to control dental caries.

OBJECTIVE: The aim of this prospective study was to determine whether a child population with low overall caries frequency benefits when prevention is targeted to high-risk individuals. METHODS: Data from clinical examinations and salivary tests were used to assess caries risk in 12-year-olds (n=1465). Children who were regarded as being at high risk of developing caries were randomized into two groups. Half (HRI group) were offered intensive prevention (counseling, F-varnish applications, F-lozenges, sealants, chlorhexidine), and the other half (HRB group) were provided the same basic prevention given to low-risk children (counseling, one F-varnish application/year). A random sample of the low-risk children (LRB) was followed up for the same 3-year period as the high-risk children. The number of children completing the study was 216 in the LRB group, 199 in the HRI group and 174 in the HRB group. RESULTS: The mean (SD) 3-year DMFS increment was 2.0 (2.4), 4.4 (4.7) and 5.1 (5.0) in the LRB, HRI and HRB groups, respectively. Comparison between the LRB and HRB groups revealed that risk assessment was fairly successful in terms of mean DMFS increment. However, 63% of the children in the LRB group developed at least one new lesion (max. 12). CONCLUSIONS: The negligible difference between the HRI and HRB groups implies that intensifying prevention produced practically no additional benefit. By offering all children only basic prevention, virtually the same preventive effect could have been obtained with substantially less effort and lower costs.

Human growth differentiation factor 9 (GDF-9) and its novel homolog GDF-9B are expressed in oocytes during early folliculogenesis.

Growth differentiation factor 9 (GDF-9) is a transforming growth factor-beta family member that is required for normal folliculogenesis in female mice, but its role as a regulator of human fertility is still unclear. We determined here by in situ hybridization and immunohistochemical analyses the localization of the GDF-9 messenger ribonucleic acid (mRNA) and protein during human folliculogenesis. The GDF-9 transcripts were not detected in primordial follicles, but they are abundantly expressed in primary follicles in frozen sections of ovarian cortical tissue material obtained at laparoscopic surgery. We raised antipeptide antibodies against GDF-9 and showed by immunohistochemical studies on paraffin sections of whole human ovaries that the GDF-9 protein is most abundantly expressed in primary follicles. We recently demonstrated that a novel GDF-9-related factor, GDF-9B, is coexpressed with GDF-9 during murine folliculogenesis. We now isolated human GDF-9B complementary DNA and genomic clones and report the unusually restricted expression pattern of human GDF-9B. The human GDF-9B transcript can be detected only in the gonads by RT-PCR analysis, and in situ hybridization studies indicate that it is not expressed in small primary follicles but, rather, in the oocytes of late primary follicles. Functional studies using the Xenopus laeuis embryo model indicate that unlike the transforming growth factor-beta family members activin and bone morphogenetic protein-4, neither GDF-9 nor GDF-9B affects mesoderm induction, suggesting that they may use signaling pathways distinct from those well defined for activin and bone morphogenetic protein-4. We conclude that 1) both GDF-9 mRNA and protein are abundantly expressed in oocytes of primary follicles in human ovary, suggesting that the GDF-9 transcript is translated at this early stage of folliculogenesis; 2) human GDF-9B is specifically expressed in gonads at low levels; and 3) the expression of GDF-9 mRNA begins slightly earlier than that of GDF-9B in the human oocytes during follicular development. Our results are consistent with the suggestion that GDF-9 and GDF-9B may regulate human folliculogenesis in a manner specific to the ovary.

Differentiation lineage-specific expression of human heat shock transcription factor 2.

Differentiation of multipotential hematopoietic cells into lineage-committed precursors involves the selection and maintenance of appropriate programs of gene expression, regulated by specific transcription factors. Using human K562 erythroleukemia cells capable of differentiating along erythroid and megakaryocytic lineages, we explore the differentiation-related role of heat shock transcription factor 2 (HSF2), which belongs to a family of transcription factors generally known to regulate heat shock gene expression. We demonstrate that enhanced HSF2 expression and the acquisition of HSF2 DNA binding activity are strictly specific for erythroid characteristics of K562 cells. Our results reveal a multistep regulatory process of HSF2 gene expression. In K562 cells undergoing hemin-mediated erythroid differentiation, the increase in HSF2 protein levels is preceded by transcriptional induction of the HSF2 gene, accompanied by increased HSF2 mRNA stability. In contrast, during megakaryocytic differentiation induced by the phorbol ester TPA, expression of HSF2 is rapidly down-regulated, leading to a complete loss of the HSF2 protein. These results indicate that the determination of HSF2 expression occurs at the early stages of lineage commitment. Taken together, our data suggest that HSF2 could function as a lineage-restricted transcription factor during differentiation of K562 cells along either the erythroid or the megakaryocytic pathway.

Efficacy and safety of fluoride varnishes.

Clinical studies show that fluoride varnishes, such as Duraphat, are effective in increasing the fluoride content in the enamel and preventing caries. Varnish application is fast and easy. A professional prophylaxis before varnish application is not necessary, which decreases the application time. Patients receive significant preventive benefits with only semiannual varnish applications. Finally, and most importantly, studies show that fluoride varnishes are safe. Effectiveness, application ease, and safety give fluoride varnishes an advantage over other types of topical fluoride treatments, such as gels and rinses.

Caries frequency in permanent teeth before and after discontinuation of water fluoridation in Kuopio, Finland.

UNLABELLED: The piped water of Kuopio, Finland, was fluoridated in 1959. Owing to strong opposition by different civic groups, water fluoridation was stopped at the end of 1992. OBJECTIVES: The aim of this study was to examine the consequences of the discontinuation on dental health. METHODS: In 1992 and 1995, independent random samples of all children aged 6, 9, 12 and 15 years were drawn from Kuopio and Jyväskylä, a nearby low fluoride town whose distribution of demographic and socio-economic characteristics was fairly similar to Kuopio's. The total number of subjects examined was 550 in 1992 and 1198 in 1995. Caries was registered clinically and radiographically by the same two calibrated dentists in both towns. RESULTS: In 1992, the mean DMFS values were lower in the fluoridated town for the two older age groups, the percentage differences for 12- and 15-year-olds being 37% and 29%, respectively. For the two younger age groups no meaningful differences could be found. In 1995, the only difference with possible clinical significance was found in the 15-year-olds in favor of the fluoridated town (18%). In 1995, a decline in caries was seen in the two older age groups in the nonfluoridated town. In spite of discontinued water fluoridation, no indication of an increasing trend of caries could be found in Kuopio. The mean numbers of fluoride varnish and sealant applications decreased sharply in both towns between 1992 and 1995. In spite of that caries declined. CONCLUSIONS: These findings suggest that the decline of caries has little to do with professional preventive measures performed in dental clinics.

Accumulation of strontium and fluoride in approximal dental plaque and changes in plaque microflora after rinsing with chlorhexidine-fluoride-strontium solution.

OBJECTIVES: To find out if strontium is incorporated into plaque and enamel in vivo during a 2-week rinsing period with a chlorhexidine-fluoride-strontium solution and to determine the effects of the rinsing on the numbers of mutans streptococci and lactobacilli in plaque. SUBJECTS AND METHODS: A total of 18 adult participants rinsed their mouths twice a day for 2 weeks, first with a placebo solution and subsequently, separated by a 1-week interval without rinsing, with a chlorhexidine gluconate (0.05%)-sodium fluoride (0.04%)-strontium (100 ppm as SrCl2) rinsing solution (CXFSr) for another 2 weeks. RESULTS: After the CXFSr rinsing period the strontium and fluoride contents (microgram g-1 plaque dry weight; mean +/- sr) of approximal plaque were 32.5 +/- 4.7 and 72.8 +/- 9.0, compared with the respective contents of 8.4 +/- 1.2 and 42.0 +/- 4.8 after placebo rinsing (P = 0.0001 for both comparisons). The strontium content remained elevated for 6 weeks. The median proportion of mutans streptococci of approximal plaque of the total viable count of bacteria was 1% after placebo rinsing but decreased to 0.2% after CXFSr rinsing. The proportion of mutans streptococci remained low at 3 weeks (P = 0.018 vs placebo) but had reached the placebo level at 6 weeks. Rinsing with CXFSr solution did not reduce lactobacilli in plaque. The strontium or fluoride contents of the enamel surfaces subjected to tooth brushing did not significantly change. CONCLUSIONS: Strontium and fluoride accumulated in dental plaque during a 2-week CXFSr rinsing period and the proportion of mutans streptococci in approximal plaque was reduced at least for 3 weeks after completion of the rinsing.

Salivary fluoride concentration in adults after different fluoride procedures.

Today, several alternatives for fluoride therapy are available. To give advice on the choice of method, the dentist should have information on how effective different fluoride treatments are in increasing salivary fluoride concentration. The aim of the present study was to measure the fluoride concentration of saliva after the use of four different fluoride methods commonly used in the Nordic countries: F mouthrinse (0.023% F), F toothpaste (1.1% F). F lozenge (0.25 mg F), and F chewing gum (0.25 mg F). In addition, a new method using toothpaste water mixture as a mouthrinse was included in the study. Fourteen adult volunteers used each of the five methods on separate days. Unstimulated saliva samples were collected at base line and 0, 10, 20, 30, 45, and 60 min after the fluoride procedure. Fluoride was separated by the microdiffusion method and analyzed using a fluoride-specific electrode. Fluoride mouthrinse and fluoride toothpaste increased the fluoride concentration of saliva significantly more than fluoride lozenge and fluoride chewing gum. For both of the latter, salivary fluoride concentration was still increased after 1 h. Toothpaste-water rinse was more effective than brushing with toothpaste. Rinsing with toothpaste-water mixture appears a good alternative for adults who need extra fluoride therapy but are not motivated enough to brush their teeth several times a day.

Plaque fluoride and mutans streptococci in plaque and saliva before and after discontinuation of water fluoridation.

Our aim was to compare plaque fluoride and the level of mutans streptococci in saliva and plaque before and 1 and 2 years after discontinuation of water fluoridation in Kuopio, Finland. For comparison, a low-fluoride community was included in the study. Pooled plaque and saliva were collected from a random sample of 12-year-olds in both communities (n = 139). Enumeration of mutans streptococci in plaque was made on MSB agar and the level of salivary mutans streptococci was measured using the Strip mutans method. Fluoride was analyzed using a fluoride specific electrode. Caries, gingival status, fluoride varnish applications and self-reported oral health habits were recorded at baseline. Before discontinuation of fluoridation, the level of mutans streptococci in saliva was significantly lower in the fluoridated than in the non-fluoridated community. The difference in plaque mutans streptococci was not statistically significant. After discontinuation of water fluoridation, there was a significant shift towards elevated values of salivary mutans streptococci in the fluoridated community, but the level of mutans streptococci in plaque remained at the baseline level. There was no significant difference between the communities in the fluoride content of plaque either before or after discontinuation of fluoridation. From the background factors, only caries scores (higher in the non-fluoridated community) and oral hygiene (better in the non-fluoridated community) were significantly different between the communities.

High strontium addition to chlorhexidine-fluoride gel does not increase its caries-preventive effect in rats.

One hundred Osborne-Mendel rats were weaned at the age of 21 to 22 days, inoculated with Streptococcus mutans in the mouth, and fed a semisynthetic diet for the next 43 days. The control group received no treatment. The study groups received gel applications on their molars with placebo, chlorhexidine-fluoride (CXF), CXF plus 50 ppm Sr, or CXF plus 250 ppm Sr daily for the first 21 days of the experiment Although caries was significantly reduced by CXF and CXF plus 50 ppm Sr treatments, the Sr additive did not significantly improve the caries-preventive effect of CXF. The addition of 250 ppm Sr to the CXF gel seemed markedly to weaken the effect of CXF.

Inhibitory effect on S. mutans by fluoride-treated conventional and resin-reinforced glass ionomer cements.

The aim of the present study was to study the effect of fluoride gel treatment on fluoride release and inhibition of acid production of Streptococcus mutans by different glass ionomer cements. Test slabs of four glass ionomer materials were fitted into the bottom of a test tube. A layer of S. mutans cells was centrifuged onto the test slabs, and the specimens were incubated for 4 h in 1.7% sucrose solution. Incubations were made using fresh, aged (29 d), aged and F-treated (1.25% F-gel), and aged, F-treated and aged samples (n = 15 per group). After each incubation, pH and F contents of the fluid phase were determined. The freshly mixed glass ionomer samples released large amounts of fluoride, and the pH fall in the fluid phase was significantly inhibited. For aged samples, the fluoride release decreased strongly and no inhibitory effect on acid production by S. mutans was seen. After application of fluoride gel, fluoride release and inhibitory effect were significantly higher than initially for all glass ionomer cements. In conclusion, all glass ionomer cements were able to take up fluoride and subsequently release it, which resulted in reestablishment of their antibacterial effect. The patterns of fluoride release and antibacterial action were virtually the same for conventional and resin-reinforced glass ionomer cements.