Studies on the Effect of Fluoride Released by Glass Ionomers in the Oral Cavity

Numerous in vitro studies have shown that fluoride released by glass ionomers can have effects on enamel, dentin, and plaque adjacent to the material. However, the action of fluoride in vivo may be different from that found in vitro. The aim of the present series of studies was to investigate the effects of glass ionomers in oral conditions. This was tested in clinical experiments conducted on adults who had freshly made or old glass ionomers in their mouths. The results of the studies showed that fluoride released by glass ionomers may increase the fluoride content of plaque close to the material. Fluoride content decreased rapidly with decreasing fluoride release from glass ionomer, but it was increased slightly even in plaque growing on three-year-old fillings. However, the effect appeared to be very local, and no increase in salivary fluoride content due to glass-ionomer fillings was found. Although the growth of plaque was not inhibited, the proportion of mutans streptococci was significantly reduced in plaque growing on glass ionomer during the six weeks after placement of the material. No such effect, however, could be seen in the case of three-year-old glass-ionomer fillings. Although in vitro studies have shown that glass ionomers can take up fluoride and subsequently release it, applying fluoride gel to old glass-ionomer fillings did not result in an increased fluoride concentration of plaque growing on the fillings in vivo. Further studies are needed to find out whether the recharging of glass ionomers with fluoride has clinical significance.

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.

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.

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

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.

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

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.

Fluoride varnish versus acidulated phosphate fluoride gel: a 3-year clinical trial

The aim of this trial was to compare the caries-preventive effect of sodium fluoride varnish and acidulated phosphate fluoride (APF) gel. A total of 254 children aged 12-13 years with high past caries experience were randomly divided into two groups. The participants received semi-annual applications of either fluoride varnish or APF gel for 3 years. During the study, the mean (+/- SD) total DMFS increments of the varnish and gel groups were 6.8 +/- 5.6 and 7.7 +/- 6.4, respectively, when initial caries was included, and 3.1 +/- 3.7 and 3.6 +/- 4.6 when initial caries was excluded. The difference was most evident on the approximal surfaces (varnish: 1.4 +/- 2.4; gel: 1.9 +/- 3.1). However, this difference was not statistically significant. Although larger studies are needed for firm conclusions about the comparative effect of the two fluoride measures, the results suggest that fluoride varnish is as effective as fluoride gel at least in preventing approximal caries. Taking into account the shorter treatment time, using fluoride varnish for professional applications seems justified.

Fluoride concentration, mutans streptococci and lactobacilli in plaque from old glass ionomer fillings

Previous studies have found that the fluoride concentration of plaque growing on or adjacent to glass ionomer cement (GIC) is increased and the proportion of mutans streptococci in plaque is reduced. So far, there are only a few studies of the long-term effect of glass ionomer fillings on plaque in vivo. The aim of this study was to determine whether old GIC fillings have effects on plaque fluoride and microflora and whether this effect can be increased by topical application of fluoride on GIC fillings in vivo. The participants were 27 adults with at least 3 GIC fillings about 3 years old. Plaque was collected from sites adjacent to the GIC fillings and from the contralateral teeth, after which a 1.2% fluoride gel was applied to all teeth. Three days later, plaque was collected from the same sites as before. Stimulated saliva was also collected at both appointments. The results show that none of the patients had elevated levels of fluoride in their saliva either before or 3 days after the fluoride treatment. The fluoride concentration was 0.51 microgram/mg protein in plaque on GICs and 0.35 microgram/mg protein in plaque on contralateral teeth (p = 0.028). After the fluoride treatment, the respective fluoride concentrations were 0.59 microgram/mg and 0.75 microgram/mg (p = 0.849). No significant differences in the proportion of mutans streptococci and lactobacilli in plaque from GIC and contralateral teeth were found. The results suggest that the fluoride concentration of plaque growing on old GIC fillings is slightly increased. In this study, however, this had no significant effect on the cariogenic microflora.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Comparison of glass-ionomer and resin-based fissure sealants: a 2-year clinical trial

In recent years, the interest in the use of glass-ionomer materials as fissure sealants has increased. The aim of this study was to compare the retention and caries-preventive effect of glass-ionomer (Fuji III) and resin-based light-cured (Delton) fissure sealants. Three health center dentists applied the sealants to 166 children; glass-ionomer sealants on one side and resin-based sealants on the contralateral side of the mouth. After 2 yr, one pair of molar teeth in the mouths of 151 children was compared. Twenty-six percent of glass-ionomer and 82% of resin-based sealants were totally present (P < 0.001). During the 2 yr, in both groups 4.6% of the sealed surfaces became carious. The results show that the retention of glass-ionomer sealants is markedly inferior to the resin-based sealants. In this study, however, no difference in caries increment on the sealed surfaces was observed. This may be due to the different mechanism of caries prevention for the sealant materials, or to the overall low caries activity of the participants.

Caries-preventive effect of fluoride varnish with different fluoride concentrations

Based on the current concept of the caries-preventive mechanism of fluoride, the fluoride concentration of some professionally applied fluoride preparations appears unnecessarily high. The aim of this trial was to study whether reducing the fluoride concentration of the sodium fluoride varnish Duraphat from the present 2.3% to 1.1% affects its clinical efficacy. A total of 274 children aged 12-14 years and having high past caries experience were randomly divided into two groups. The participants received 3 annual applications of either 2.3% or 1.1% varnish for 3 years. Clinical and radiographical examinations were performed at baseline and at the end of the follow-up. The mean total DMFS increments of the 2.3% and 1.1% varnish groups were 5.5 (SD 5.7) and 5.7 (5.3), respectively, when initial caries was excluded, and 14.3 (12.0) and 14.9 (12.9) when initial caries was included. The differences were statistically non-significant. There were no significant differences in the surface-specific DMFS increments between the groups either. The 95% confidence interval for the difference between the groups in total mean DMFS increment (initial caries excluded) was calculated at -1.21 to + 1.54, i.e. at this level of confidence at most 0.5 surfaces per year would have been saved using the more concentrated varnish. Consequently, it can be stated at a reasonable level of certainty that if a difference in the efficacy of the two varnishes exists, it probably is minute. Lowering the fluoride concentration of Duraphat is worth considering at least when used for children.

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.

Relationship between oral hygiene and approximal caries in 15-year-old Norwegians

The objective of the present study was to investigate the relationship between oral hygiene level, as judged from the number of non-bleeding papillae (NBP), and approximal caries development and progression in 14- to 15-year-old Norwegians. NBP, according to Gjermo, were registered in 165 15-year-old Norwegians. Approximal lesions in the outer half (D1) or in the inner half (D2) of the enamel or in dentin (D3) and the total numbers of carious approximal surfaces (D1 + D2 + D3), filled approximal surfaces, and sound approximal surfaces were recorded from bite-wing radiographs from premolars and molars at the age of 14 and 15 years (values expressed as mean +/- SD). The average number of NBP in the whole group was 4.6 +/- 4.5. One group with good oral hygiene (NBP > or = 5, 8.7 +/- 3.3, n = 76) and one group with bad oral hygiene (NBP < 5, 1.2 +/- 1.5, n = 89) were established. Carious approximal surfaces and filled approximal surfaces were significantly higher in the group with few than in the group with many NBP (6.0 +/- 5.9 vs. 1.7 +/- 2.8 and 2.6 +/- 4.3 vs. 0.9 +/- 1.8, respectively). The number of lesions at the age of 15 and progression of lesions from 14 to 15 years were also significantly higher in the group with few NBP. It is concluded than in populations exposed regularly to fluoride, the oral hygiene level may be an important indicator of a high caries risk.

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)

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.

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.

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.

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.

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.

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.

Resistance of occlusal fissures to demineralization after loss of glass ionomer sealants in vitro

Seventy-one caries-free human occlusal fissures were used for this study. Twenty-two fissures were sealed with a glass ionomer sealant (Fuji Ionomer Type III--G-C Dental Industrial Corp., Tokyo, Japan), 24 were widened with a diamond bur and sealed with the glass ionomer sealant, and 25 were left unsealed. After one week, the sealants were removed as completely as possible with a probe. All fissures were demineralized for seven weeks. Sections made from the fissures were examined with a polarizing microscope, and the depths of the fissure lesions were measured. The mean lesion depths for controls, sealed natural fissures, and sealed widened fissures were 143, 93, and 75 microns, respectively. A statistically significant difference was noted between the two experimental groups and the control group (no sealant). The results suggest that fissures sealed with glass ionomer are more resistant to demineralization than control fissures, even after macroscopic sealant loss. This may be the result of the combined effect of fluoride released by glass ionomer and residual material in the bottom of the fissures.

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.

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.

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.

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.

Prevention of rat fissure caries by sodium fluoride varnish (Duraphat) with different fluoride concentrations

125 Osborne-Mendel rats were weaned at 22-23 days, inoculated with Streptococcus sobrinus and fed a cariogenic diet for 40 days. The control group received no treatment; the study groups received applications of Duraphat containing 2.3, 1.1, or 0.6% fluoride or a placebo varnish on days 21-23. The placebo varnish had no effect on caries. Fissure caries was significantly reduced by the 2.3 and 1.1% fluoride varnishes, whereas the caries reduction found after treatment with the 0.6% fluoride varnish was not statistically significant. These results suggest that reducing the fluoride content of Duraphat by half does not significantly reduce its caries-preventive effect, but the progress of caries seems to be somewhat slower with the 2.3% fluoride varnish.

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.

Effects of a sodium fluoride solution and a varnish with different fluoride concentrations on enamel remineralization in vitro

To study the efficacy of sodium fluoride varnishes and a NaF solution in remineralization of enamel, 120 slabs of non-carious human enamel enamel were presoftened for 6 h and randomly divided into six groups. The slabs were stored in synthetic saliva for 9 days, except for a daily 30-min immersion in 0.1 M lactic acid-NaOH buffer. During the 9-day period, one group of the slabs received no treatment, and the rest were treated once or three times with 2.3% or 1.1% sodium fluoride varnish Duraphat, or nine times with a 0.1% NaF solution. Finally, the slabs were demineralized for 1 h, and the amount of dissolved Ca and F was determined. Microhardness of enamel was determined initially, after presoftening, after the 9-day period, and after the 1-h demineralization. All fluoride treatments prevented enamel softening almost completely during the 9 days, but the control slabs softened markedly. Fluoride varnishes were more effective than NaF solution. Three applications of 2.3% Duraphat were slightly more effective than any of the other varnish treatments, but one treatment with 2.3% varnish was not more effective than treatments with 1.1% varnish. Enamel treated three times with 1.1% varnish showed the greatest acid resistance during the 1-h demineralization. The results suggest that the efficacy of the varnish was not proportional to the fluoride concentration but rather to the number of applications. Fluoride uptake by enamel was greatest with the most concentrated varnish. Enamel solubility was not, however, directly proportional to the fluoride content of enamel.

Frequency of initial caries lesions as predictor of future caries increment in children

The aim of this study was to evaluate the predictive power of the frequency of initial caries lesions in selecting persons at high risk for caries. The subjects (n = 124) were 11-13 yr old at the beginning of the follow-up. Caries was registered initially and and after 5 yr. Evaluation of the predictions was based on cross-tabulations of the subjects according to their predicted caries risk and the actual 5-yr caries increment. Logistic regression analyses were used to produce the individual risk scores. In addition to the caries scores, age of the subjects was included in the prediction function. In bivariate analyses the total initial caries score at baseline correlated better with caries increment than FS and DS scores did (r = 0.40, 0.13, and 0.31, respectively). When past caries experience was used as predictor, 69% of the children were classified correctly into the low and high risk groups. Surprisingly, only two more subjects (2%) were classified correctly when initial caries score was included in the function. These results suggest that inclusion of initial caries score adds little to the predictive power of the conventional DS and FS scores.

Streptococcus mutans counts obtained by a dip-slide method in relation to caries frequency, sucrose intake and flow rate of saliva

The level of Streptococcus mutans in saliva was determined by a dip-slide method in 841 13-year-old children in order to identify children with high caries risk. For each child, the flow rate of saliva was determined. Caries scores were obtained from Public Dental Health records. A sucrose intake score was calculated based on self-reported frequency of intake of six types of sugary products. As S. mutans counts increased, there was a significant trend of increased DMFS and DS scores. No linear correlation was observed between reported intake of sucrose and S. mutans counts, but the children with the highest counts (class 3) tended to have significantly higher sucrose intake than the rest of the children. The flow rate of saliva decreased significantly as S. mutans increased.

Prevention of fissure caries in rats by dietary F supplement with and without topical application of F and Sr + F

In our previous studies, combined dietary and topical fluoride have shown to be more effective than each alone. Moreover, supplementation of chlorhexidine-fluoride solution with Sr was beneficial for caries prevention in rats. In the present study, the caries-preventive effect of fluoride added to the diet plus F and/or Sr applications was studied in two experiments with rats. One group received dietary fluoride supplement only. In other groups, either a Sr solution, a fluoride varnish, or a Sr solution plus fluoride varnish were applied to newly erupted molars. In addition, one group received both topical applications of Sr + F and dietary fluoride. Caries development was followed longitudinally during periods of 15, 30 or 54 days. The greatest and most significant reduction of caries resulted from the combination of fluoride varnish plus dietary fluoride supplement. Treatment with Sr solution at the beginning of the experiment had no effect on caries either alone or combined with fluoride varnish. It was found that caries increased rapidly and then levelled off after the 30-days feeding period in all groups. In the treatment groups, however, caries was arrested at a considerably lower level than in the control group.

A scanning electron microscopic study of bacterial penetration of human enamel in incipient caries

In 23 human teeth, cracked enamel under white spot lesions without any visible loss of tooth substance was examined. Bacterial contamination from the enamel surface was prevented by brushing and consequent fixing of the remaining surface coatings before the enamel was fractured. In 7 of 23 specimens, bacterial colonies were observed under the enamel surface, sometimes as deep as the enamel-dentine junction and the dentine. In most samples the subsurface enamel appeared to be partly disintegrated. Bacteria can thus be found under surface enamel at an early stage of caries while the surface is still intact.