Post-brushing rinsing for the control of dental caries: exploration of the available evidence to establish what advice we should give our patients.

Post-tooth brushing rinsing behaviours have the potential to either reduce or enhance the effectiveness of fluoride toothpaste and show wide variation in the general population. There is a lack of high-quality evidence to support definitive guidance in this area. However, the currently available international guidelines provide consistent recommendations despite the limited evidence. To explore the available evidence base and recommendations on optimal post-brushing rinsing behaviour relating to the use of both water and mouth rinses, a meeting was held between the authors and other experts. This paper reports the consensus views of those present at the meeting concerning what advice we should give our patients. A full list of meeting attendees is provided at the end of this article.

Effects of flossing and rinsing with a fluoridated mouthwash after brushing with a fluoridated toothpaste on salivary fluoride clearance.

The aims of this study were to test the hypothesis that flossing after brushing with a fluoridated toothpaste may lower salivary fluoride (F), and to evaluate the consequence of subsequent F mouthwash use. Twenty adults used 3 oral hygiene regimes in a randomised order: A, brushing with an NaF toothpaste; B, as A but followed by professional flossing; C, as B followed by rinsing with an NaF mouthwash. Saliva samples were collected up to 120 min after each regime and analysed for F. The mean area under the clearance curve value for regime C was statistically significantly greater than the corresponding values for A and B (p < 0.0001), which differed little. The regime that included the mouthwash may provide better anticaries protection.

Effect of rinsing with mouthwashes after brushing with a fluoridated toothpaste on salivary fluoride concentration.

The aim of the study was to determine whether rinsing with a mouthwash after brushing with a fluoridated toothpaste affected oral fluoride (F) retention and clearance compared with an oral hygiene regime without mouthwash. In this supervised, single-blind study, 3 regimes were compared: (A) brushing for 1 min with 1 g of 1,450 microg F/g NaF toothpaste followed by rinsing for 5 s with 10 ml water; (B) as A but followed by rinsing for 30 s with 20 ml of 100 mg F/l NaF mouthwash, and (C) as B but rinsing for 30 s with a non-fluoridated mouthwash. Twenty-three adults applied each treatment once in a randomised order, separated by 1-week washout periods, and used a non-fluoridated toothpaste at home prior to and during the study. Whole saliva samples (2 ml), collected before each treatment commenced and 10, 20, 30, 60, 90 and 120 min afterwards, were subsequently analysed for fluoride by ion-specific electrode. The mean (SD) back-transformed log (area under salivary F clearance curve) values were: A = 2.36 (+3.37, -1.39), B = 2.54 (+2.72, -1.31) and C = 1.19 (+1.10, -0.57) mmol F/l x min, respectively. The values for regimes A and B were statistically significantly greater than that for regime C (p < 0.001; paired t test). These findings suggest that use of a non-F mouthwash after toothbrushing with a F toothpaste may reduce the anticaries protection provided by toothbrushing with a F toothpaste alone. The use of a mouthwash with at least 100 mg F/l should minimise this risk.

Fluoride uptake to demineralised enamel: A comparison of sampling techniques.

Fluoride uptake is a recognised way of assessing the potential anticaries efficacy of fluoride (F) treatments. The aim of the present study was to compare an abrasion method of sampling treated enamel, based on that of Weatherell et al. [Caries Res 1985;19:97-102], with the acid-etch method of Raven et al. [Caries Res 1991;25:130-137]. Two adjacent demineralised areas were created on the polished surfaces of bovine incisors using an acid gel system. One artificial lesion from each tooth was subsequently treated for 6 h at 37 degrees C with one of two fluoridated dentifrice slurries (1 part: 3 parts water), whereas the other was treated similarly with a slurry of non-F control dentifrice. One set of treated lesions was then separated, the base of each enamel block polished until planoparallel with the demineralised surface and the lesions isolated by cutting away the adjacent sound enamel. Each block was mounted on the probe of a digital micrometer and the demineralised surface abraded with silicon carbide lapping film until sound material was reached. Abraded material was dissolved in perchloric acid and the buffered solution analysed for fluoride by ion-selective electrode. Each lesion of a second set of treated, demineralised enamel blocks was etched by 20microl acid and the resulting solutions analysed for F. Mean F uptakes [microg cm-2 (SD)] were: abrasion (n = 7/treatment); F dentifrice A = 1.39 (0.89) and B = 0.86 (0.45) relative to non-F controls = 0.11 (0.12), 0.14 (0.06), respectively; and acid-etch (n = 14/treatment); A = 1.27 (0. 49), B = 0.69 (0.23), controls = 0.12 (0.06), 0.12 (0.06), respectively. Significant differences (p<0.05) for both data sets were: A>B> control. The results show good agreement between the sampling methods and demonstrate the ability of the abrasion technique to distinguish between F treatments.

Acute bereavement services and routine referral as a mechanism to increase donation.

Efforts to develop a mechanism that improves donation rates and provides better service to patients and staff are presented in this article. The University of Nebraska Medical Center has incorporated a routine referral process into its acute bereavement services requiring representatives to respond to each in-house death to provide consistent support and management for the decedent's family and the hospital staff. Every family was offered bereavement support and the opportunity to consent to autopsy as well as to organ and tissue donation if medically appropriate. Key data related to death and consent discussions were documented, routinely reviewed, and reported to a central location. Appropriate and timely access of these data helped to modify the program and assess its need for additional education or intervention.

Effect of low levels of fluoride on calcium uptake by demineralized human enamel.

The effect of fluoride (ca. 0.1 parts/10(6)) on calcium uptake by enamel was examined under alternating remineralizing and demineralizing conditions. The remineralizing solutions contained either 0, 0.058, 0.104, or 0.138 parts/10(6) fluoride (ex NaF), while the demineralizing solutions contained no added fluoride. During the demineralization periods, calcium loss was similar for all groups. However, during the remineralizing periods, all levels of added fluoride were found to promote calcium uptake. Calcium levels taken up by the artificial lesions were sound to increase with increasing fluoride concentration in solution, and were independent of surface area of exposed enamel. In the absence of fluoride, even under conditions that are considered to be remineralizing, further demineralization took place.

Studies on plaque fluoride after use of F-containing dentifrices.

Increased fluoride levels in plaque and saliva have been associated with improved protection against dental caries for dentifrices which contained sodium monofluorophosphate (Duckworth et al., 1992). The main aim of the present work was to test whether oral fluoride retention depended on F source after use of dentifrices containing either NaF or Na2FPO3. In study 1, plaque samples were collected from 474 subjects who had been using one of six test dentifrices for two years, and analyzed by F extraction with water. The dentifrices contained 1000 or 1500 micrograms F/g as either NaF or Na2FPO3. Significantly more fluoride was found in plaque from subjects who were using the NaF dentifrices than in plaque from subjects who were using Na2FPO3 dentifrices of the same F content. Subsets of plaque samples were large enough to divide into two parts for extraction by both acid and water. No significant difference was found between mean fluoride contents, indicating that the majority of fluoride retained in plaque from these conventional dentifrices appears to be relatively labile. The results of two small-scale human enamel studies showed that NaF dentifrices gave elevated F concentrations in plaque and saliva, respectively, compared with Na2FPO3 dentifrices of equivalent F content, consistent with the main plaque study 1. These findings demonstrate that oral F retention from dentifrices is dependent on the source of ionic fluoride and support the view that NaF dentifrices may be more clinically effective than dentifrices which contain the same amount of F as Na2FPO3.

Studies on the cariostatic mechanisms of fluoride.

This paper reviews mechanisms underlying the caries-preventive effects of fluoride, with special reference to factors which govern the efficacy of topical treatments. Fluoride reduces demineralisation in several ways: by reducing bacterial acid production and acidurance; by reducing the equilibrium solubility of apatite; and by the fluoridation of apatite crystal surfaces, reducing the dissolution rate, whether or not there is reduced solubility of the bulk mineral. On available evidence, the last seems to be the most important effect. The effect depends upon the presence of sufficiently high, dissolved fluoride concentrations to maintain the surface fluoridation. The provision of dissolved fluoride is the key to successful therapy, especially topical treatments. Fluoride also promotes remineralisation even at low concentrations, thus slowing or preventing overall mineral loss. The formation of intra-oral fluoride reservoirs capable of supplying ions for a prolonged period is crucial to the success of topical treatments. Such reservoirs include calcium fluoride, formed mainly at tooth surfaces, and fluoride associated with organic components of plaque and oral soft tissues. The patterns of fluoride clearance from intraoral reservoirs are discussed. Fluoride may be present in dentifrices as the fluoride ion (F-) or as the monofluorophosphate ion (FPO3(2-)). It is concluded that the efficacy of FPO3(2-) probably depends on enzymic hydrolysis to F-. Monofluorophosphate appears to be retained less well in intra-oral fluoride reservoirs and reasons for this are discussed.

Effect of mouthwashes of variable NaF concentration but constant NaF content on oral fluoride retention.

Previous work showed that oral fluoride levels increased with increasing applied F dose for both mouthwashes and dentifrices. This study aimed to determine whether the above dependence was related to applied fluoride concentration or applied fluoride amount. Ten adults mouthrinsed with aqueous NaF solutions of 1-10 ml, each of which contained 2.5 mg F, i.e. in the concentration range 250-2,500 ppm F. Subjects rinsed for 1 min and then spat out. Samples of mixed saliva were collected for 3 h afterwards, which were analysed for fluoride. Salivary fluoride clearance curves were obtained which could be fitted to a pharmacokinetic model involving processes ascribed to loss of fluoride from saliva by swallowing and to exchange of fluoride between saliva and an oral reservoir. Mean salivary fluoride concentrations increased significantly with increasing applied F concentration both within the first 3 h after single use and up to at least 18 h after regular daily use. These findings suggest that applied F concentration is a more important factor than applied F amount per se in determining the elevation of oral fluoride levels following topical fluoride use. This implies that application of a given F dose, in a smaller volume at higher concentration than the current norm, may increase efficacy without increasing the risk of adverse effects.

The science behind caries prevention.

Many agents have been shown to have an anticaries effect or to have the potential for such an effect. They can be categorised by their modes of action into three groups: those which affect plaque and plaque bacteria, those which affect tooth enamel chemistry and those which buffer oral pH. To be effective clinically, agents must not only possess intrinsic efficacy but also good oral retention characteristics. Currently, chlorhexidine is arguably the only antibacterial agent to have inhibited caries in humans, but is not employed in anticaries dentifrices and mouthrinses intended for long-term unsupervised daily use because of formulation difficulties and undesirable side effects such as tooth stain. Certain calcium salts and xylitol may also exert some clinical effect. The only extensively clinically-proven agent is fluoride. Well established reasons for the success of fluoride are its abilities to inhibit demineralisation of enamel and to enhance the remineralisation of incipient caries lesions. Recent research has highlighted the persistence of fluoride in saliva and plaque at potentially-active concentrations between successive regular applications of dentifrices and mouthrinses as a further important mechanistic step. Oral fluoride retention studies can explain recent clinical observations of increased efficacy of sodium fluoride dentifrices compared with sodium monofluorophosphate dentifrices of equivalent fluoride content.

Oral fluoride measurements for estimation of the anti-caries efficacy of fluoride treatments.

The aims of this work were (a) to assess the oral bioavailability of fluoride delivered from dentifrices and (b) to test for a possible link between the results and clinical data obtained with the same dentifrices. Oral fluoride concentrations were measured in samples of saliva and plaque taken from seven subjects, after use of dentifrices which contained 0, 1000, 1500, and 2500 micrograms F/g as sodium monofluorophosphate. Salivary fluoride in samples obtained within the first few hours after a single dentifrice application, or up to 20 h after four weeks' daily use, increased with increasing F content of the dentifrice. For example, the mean zero-time intercepts of the second phase of salivary fluoride clearance curves for the above dentifrices were 0.46, 1.48, 1.88, and 3.03 mumol F/L, respectively. Plaque fluoride measured after four weeks' daily use of the dentifrices exhibited similar dose-response behavior. Linear regression analysis showed these trends to be statistically significant for both saliva (p less than 0.001) and plaque (p less than 0.025). Mean saliva and plaque fluoride concentrations were inversely associated with mean three-year caries increments for the three fluoride-containing dentifrices obtained in a recent clinical trial: DMFS scores 6.80, 6.33, and 5.71, respectively (Stephen et al., 1988). This suggests that oral fluoride measurements are a valuable in vivo method for the evaluation of the potential anti-caries efficacy of fluoride-containing dental products.

Intra-oral models to assess cariogenicity: evaluation of oral fluoride and pH.

The main purpose of this paper is to review the various methods used for evaluation of fluoride retention in saliva, plaque, and enamel following application of topical anti-caries treatments such as F dentifrices and F mouthwashes. Such methods monitor delivery of fluoride to the site of action, the mouth, and so can be regarded as assessing potential for treatment action. It is concluded that intra-oral fluoride measurements are appropriate to support bioequivalence claims for anti-caries treatments, provided that particular chosen methods have been calibrated against clinical data. Studies purporting to show superiority are of interest mechanistically, but links to caries are not sufficiently understood to define superiority claims. A wide variety of methods has been used for determination of the fluoride content of enamel. Of these, well-established methods such as the micro-drill and acid-etch procedures are appropriate for routine comparative testing, whereas sophisticated instrumental techniques such as SIMS are more appropriate for detailed mechanistic studies. Intra-oral pH measurements are also relevant to many topical treatments. Single-site determinations in plaque are preferred, but for comparative studies non-specific determinations may be adequate.

Effect of mouthrinsing after toothbrushing with a fluoride dentifrice on human salivary fluoride levels.

In a recent clinical trial of sodium monofluorophosphate dentifrices, oral rinsing habits were found to influence dental caries. Thus an oral fluoride clearance study has been undertaken which was designed to test a possible mechanism for the observed effects. Eight subjects brushed with one of the trial dentifrices and then rinsed using 1 of 8 procedures of varying thoroughness. The salivary fluoride concentration measured 5 min after dentifrice application decreased significantly with increasing rinse volume, rinse duration, and rinse frequency (p less than 0.01, analysis of variance). The area under the clearance curve determined over a further 3 h was significantly higher (300%; p less than 0.01) following use of the least thorough rinsing procedure (5 ml x 2 s once) as compared with the corresponding area under the clearance curve following the most thorough procedure (20 ml x 10 s twice). These findings indicate that rinsing habits may play an important role in the oral retention of fluoride from dentifrices which may, in turn, affect their clinical efficacy.

Oral fluoride retention after use of fluoride dentifrices.

Fluoride is the only extensively clinically proven means of reducing dental caries. Despite a large body of epidemiological data on the effectiveness of fluoride, delivered in the form of dentifrices, mouthrinses, drinking water, etc., the precise mode of action of fluoride is not completely understood. The purpose of this paper is to report an investigation of the link between oral fluoride levels and applied fluoride dose from dentifrices. Human salivary fluoride clearance studies and equilibrium baseline studies of fluoride in saliva and plaque have been carried out with dentifrices which contained 1,000, 1,500 and 2,500 micrograms fluoride per gram as sodium monofluorophosphate. After a single brushing with a fluoride dentifrice, salivary fluoride decreased in two distinct phases: an initial rapid phase which lasted for 40-80 min, depending on the individual, and a second slow phase lasting for several hours. The latter phase is believed to be due to fluoride released from an oral fluoride reservoir. During regular repeated use of the test dentifrices, the equilibrium baseline fluoride concentration, attained in both saliva and plaque between one application and the next, increased significantly compared with placebo values. Such elevated baseline fluoride concentrations also increased with increasing Na2FPO3 content of the dentifrices. The present work supports the concept that labile fluoride, stored in an oral fluoride reservoir at the time of treatment application, may maintain a prolonged protective effect against dental caries.

Comparison between evaluation methods for the anti-caries efficacy of monofluorophosphate-containing dentifrices.

A comparison is described of three methods of preclinical assessment of potential anti-caries efficacy for topical fluoride treatments. Methods are compared using dentifrices containing 1,000, 1,500 and 2,500 ppm F as sodium monofluorophosphate (SMFP). These formulations have been shown elsewhere to give a statistically significant dose response of increasing anti-caries efficacy [Stephen et al., 1988]. An in situ enamel insert model, oral fluoride pharmacokinetics and F uptake to demineralised enamel are all shown to correlate with clinical efficacy for the test dentifrices studied.