The effect of chewing gum use on in situ enamel lesion remineralization.

Two independent cross-over studies investigated the possibility of enhanced early enamel lesion remineralization with the use of chewing gum. The first study involved a sorbitol-containing chewing gum, and the second, which had an identical protocol, tested a sucrose-containing chewing gum. In each study, 12 volunteers wore in situ appliances on which were mounted enamel sections containing artificial caries lesions. Subjects brushed twice daily for two min with a 1100-ppm-F (NaF) dentifrice (control and test) and in the test phase chewed five sticks of gum per day for 20 min after meals and snacks. Microradiographs of the enamel lesions were made at baseline and at the end of the seven-week experimental period. In the sugar-free gum study, the weighted mean total mineral loss (delta z) difference [(wk7-wk0) x (-1)] was 788 vol.% min. x micron for the gum, corresponding to remineralization of 18.2%, vs. the control value of 526 vol.% min. x micron, 12.1% remineralization (p = 0.07). There were no significant differences for the surface-zone (p = 0.20) and lesion-body (p = 0.28) values. In the sucrose-containing gum study, the delta z difference was 743 vol.% min. x micron for the gum, corresponding to a remineralization of 18.3%, vs. the control value of 438 vol.% min. x micron, 10.8% remineralization (p = 0.08). The surface-zone values were not significantly different (p = 0.55). For the lesion body, however, the sucrose-containing gum value of 6.11 vol.% min. was significantly different (p = 0.01) from that of the control (2.81 vol.% min.).

The pH and titratable acidity of a range of diluting drinks and their potential effect on dental erosion.

OBJECTIVES: To investigate, in vitro, the potential dental effects of diluting juices by measuring their acidity levels and to examine the effect dilution has on the potential erosive properties of the drinks. METHODS: Four commonly available diluting drinks were assessed for both pH and titratable acidity at a variety of dilutions, reflecting the range of concentrations over which such drinks may be consumed. Predetermined dilutions of citric acid and hydrochloric acid, with similar pH values to those of the drinks, were used as positive control acidic solutions. The pH measurements throughout the study were made using a pH electrode connected to an Orion EA940 IonAnalyser. RESULTS: All four drinks demonstrated a high degree of resistance to a rise in pH, indicating high intrinsic buffering capacity. The measured pH changed very little with increasing dilution ratio when compared to the citric and hydrochloric acid controls, even when considered extremely dilute. In contrast, the titratable acidity of each of the drinks reduced proportionally with increasing dilution, thereby reducing considerably its erosive potential. CONCLUSIONS: While dilution had very little effect on the measured pH values, the titratable acidity reduced as the drink became more dilute. Since there appears to be a direct relationship between dilution and titratable acidity, the erosive potential of diluting juices may be reduced substantially by the addition of water. It remains unlikely, however, that the drinks would ever be consumed at a 'safe' level of dilution due to diminished taste and colour.

The release of mercury from dental amalgam and potential neurotoxicological effects.

OBJECTIVES: The aim of this study was to estimate the amount of mercury released into both air and saliva from fresh and aged, abraded amalgam discs and then investigate neurotoxic effects of inorganic mercury upon sensory neuronal cultures. METHODS: An air-tight chamber was constructed to allow the combined estimation of mercury species released from amalgam pellets. The level released into air and saliva from both freshly packed and aged-abraded amalgam pellets was assessed. Dorsal root ganglia cultures from male CBA mice were exposed to 1 and 10 microM mercuric chloride concentrations. The effects of this were assessed by means of morphology, adhesion, size and immunocytochemistry. RESULTS: The mercury released into air from dry fresh amalgam was low and less than the recommended industrial exposure limit for mercury. However, covering the discs with saliva reduced air-mercury levels by 46-56% and there was a statistically significant difference in the air-mercury levels recorded (p=0.013-0.048). The mercury released into air from dry abraded amalgam was shown to be above the recommended industrial limit. Coating the abraded amalgam discs with saliva reduced the mercury by 66-72% with the levels recorded being significantly lower (p<0.001). The level of total mercury within the saliva was found to be highly variable. Little change was noted in the neuronal cultures treated with 1 microM mercuric chloride. However, the cultures exposed to high level (10 microM) mercuric chloride showed cells that became rounded and clumped together indicating pathological change. CONCLUSIONS: Amalgam placement appears to present minimal mercury exposure risk. To reduce the amount of mercury released into air, however, amalgam should be polished in a moist atmosphere with high volume aspiration. The neurotoxic effect of mercury appears to be related to concentration, as only in the cultures treated with 10 microM mercuric chloride showed striking qualitative and quantitative cellular changes.

Fluoride release from orthodontic band cements-a comparison of two in vitro models.

OBJECTIVES: To compare, in vitro, the fluoride release from a conventional glass ionomer cement (Ketac-Cem), a resin-modified glass ionomer cement (3M-Multicure) and a polyacid modified composite (Ultra Band-Lok) using a banded tooth model and a disc model with the same mean cement weight. METHODS: Forty pairs of caries-free third molars were collected and divided into two groups, each of 20 teeth. One tooth from each pair was banded with Ketac-Cem and the other with Ultra Band-Lok or 3M-Multicure; the average band size for each cement group was the same. Two coats of nail varnish were painted on each tooth to within 1mm of the band margin. Five discs (4.5mm diameter and 2mm depth) were prepared for each cement, these dimensions having been calculated so that the mean cement weight of the banded tooth model matched that of the disc model for each cement. The fluoride released into 2ml of deionised water, from each banded tooth or disc, was measured at regular intervals over 30 days using an Orion ion-selective electrode connected to an ion analyser. RESULTS: At 30 days, for both banded tooth and disc models, the mean cumulative fluoride release was greatest from 3M-Multicure followed by Ketac-Cem, which in turn released more fluoride than Ultra Band-Lok. These differences were all significant (p<0.05). Despite having the same mean cement weight, the banded tooth model for Ketac-Cem and 3M-Multicure released approximately 3-4 times more cumulative fluoride than the disc model after 30 days (p<001). For Ultra Band-Lok, both models released comparable levels of fluoride (p>0.05). CONCLUSIONS: Cement type, specimen geometry and surface area appear to influence significantly fluoride release characteristics.

The effect of a resin-modified glass ionomer restorative material on artificially demineralised dentine caries in vitro.

OBJECTIVES: Recurrent caries is one of the most common reasons for the replacement of restorations. One method of reducing the frequency of this problem may be by using fluoride-releasing restorative materials. The aim of this in vitro study was to evaluate the progression of artificial lesions around resin-modified glass ionomer (Vitremer) restorations placed in root surfaces. Class V cavities were prepared on the mesial and distal surfaces of 28 human premolar teeth. Artificial carious wall lesions were created in all cavities. The root of each tooth was then hemisected through the middle of the two cavities, before being restored with either the glass ionomer or amalgam, while the opposing cavities on the same root portion were varnished as negative controls. Forty-eight specimens were pH-cycled in remineralising and demineralising solutions for 20 h and 4 h, respectively, each day for 4 weeks, whilst in a smaller control group of eight specimens, the demineralising solution was replaced with deionised water. Mineral changes in the carious lesions were evaluated using contact microradiography. RESULTS: Results showed that varying degrees of subsurface demineralisation and remineralisation were evident, with a laminated appearance in lesions adjacent to the glass ionomer. There was higher remineralisation in the glass ionomer-filled cavities compared with the amalgam-filled cavities. In the water-cycled group, glass ionomer showed an increase in mineral content (p < 0.05), while no changes were observed in the amalgam-filled cavities. CONCLUSIONS: This model has shown that glass ionomer has a greater potential than amalgam for remineralisation of artificially created wall lesions within an acidic environment.

Fluoride release and cariostatic ability of a compomer and a resin-modified glass ionomer cement used for orthodontic bonding.

OBJECTIVES: The aims of this study were to compare the local and systemic uptake of fluoride released from a compomer material (Dyract Ortho) and a resin-modified glass ionomer cement (Vitremer) with that of a conventional resin adhesive (Right-On) and to compare the cariostatic ability of each of the test materials with that of the resin control. METHODS: Twenty six patients were randomly allocated to have a bracket bonded to a premolar on one side of the arch with one of the test materials and on the opposite side with the control material. Premolars destined for extraction as part of an orthodontic treatment plan were selected for bonding. A non-fluoride toothpaste was used by all participants for 4 weeks prior to bracket bonding and throughout the 4 week trial period. Fluoride release was measured in saliva, plaque and urine samples taken pre-bonding and 4 weeks post-bonding. Enamel demineralisation was assessed by scoring the buccal surface of each extracted tooth using a caries index. RESULTS: Neither Vitremer nor Dyract Ortho altered salivary or urinary fluoride concentration significantly 4 weeks post-bonding but plaque fluoride concentration increased significantly around premolars bonded with Vitremer. The test materials as a combined group were associated with significantly less demineralisation than the control material but there was no significant difference in cariostatic ability detected between either Dyract Ortho or Vitremer when each group was compared separately with the control. CONCLUSIONS: Fluoride released from Dyract Ortho or Vitremer is likely to exert a local and not a systemic effect. In a 4-week clinical study, the cariostatic ability of the fluoride-releasing cements, as a combined group, was superior to that of the non-fluoride releasing control but there was no significant difference in cariostatic ability between the two test materials when each test group was compared separately with the control.

Daily exposure to fluoride mouthrinse produces sustained fluoride release from orthodontic adhesives in vitro.

OBJECTIVES: To determine firstly, if sustained fluoride release can be achieved from five orthodontic adhesives: Ketac-Cem, Fuji ORTHO LC, Sequence, Transbond and Right-On, with daily exposure to fluoride mouthrinse in vitro, and secondly, if sustained fluoride release can be re-established from the same specimens, after an interruption in mouthrinse exposure. METHODS: Ten brackets were bonded to bovine incisors using each adhesive. Each adhesive group was divided equally into a test and a control sub-group. In phase 1 (42 days), the test sub-groups were exposed for 1min daily to fluoride mouthrinse (225 ppm), followed by immersion in de-ionised water for 42 days to deplete their fluoride reserves. Mouthrinse exposure was then resumed in phase 2 (28 days). Mean cumulative fluoride release (MCFR) was calculated for days 0-21 of phase 1 and for the plateau portion of the fluoride release curves in phase 1 (days 21-42) and phase 2 (days 7-28). RESULTS: During phase 1, the MCFR for each test sub-group was significantly greater than its control (p<0.05). There was no significant difference in MCFR between the curve plateau portion of phases 1 and 2 for all adhesives except Transbond, for which MCFR was less in phase 2 (p<0. 05). CONCLUSIONS: Sustained fluoride release occurred for each adhesive exposed daily to fluoride mouthrinse, at a level significantly greater than its control. After fluoride exhaustion, re-exposure to daily fluoride mouthrinse produced sustained fluoride release levels comparable to those prior to exhaustion, for all adhesives except Transbond.

Fluoride release from orthodontic cements-effect of specimen surface area and depth.

OBJECTIVE: The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material. METHODS: Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period. RESULTS: For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements. CONCLUSIONS: For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

In vitro dentine permeability: the relative effect of a dentine bonding agent on crown preparations.

OBJECTIVE: The aim of this study was to determine whether a dentine bonding agent (DBA) had an effect in reducing fluid filtration under cemented provisional crowns. METHODS: Crown preparations on 34 premolars, randomly allocated to two equal-sized test and control groups, were assessed for dentine permeability by a fluid filtration technique. In the test group, prepared crowns were acid-etched and then treated with a DBA (Prime & Bond NT). In the control group, no such DBA was applied. Provisional crowns were cemented on both groups of teeth using non-eugenol zinc oxide cement. Fluid filtration rates were measured repeatedly after crown preparation, at cementation, 1 h, 1 day, 1 week and 3 weeks following crown cementation for both groups. Filtration rates were also measured after acid-etching and dentine bonding for the test group. RESULTS: There was insufficient evidence to suggest any statistically significant differences either between the two groups or, on average, across the five time points in each group in terms of the relative percentage of fluid filtration. CONCLUSION: The DBA used did not seal dentinal tubules any more than did the smear layer and provisional crowns luted with a non-eugenol ZnO cement.

The effect of saliva on enamel and dentine erosion.

The present study aims to assess the ability of saliva, both in vitro and in situ, to prevent surface mineral loss from enamel and dentine when exposed to an erosive challenge. Fifteen groups of four varnished thin tooth sections were stored in saliva collected from individuals taking part in the in situ study and a further eight groups, each containing four sections, were stored in deionised water. In vitro, sections were stored in saliva or water for 14 days. In addition, fifteen subjects each wore an appliance with four varnished sections. Appliances with sections were worn for 14 days. All sections were exposed to 25 ml of erosion solution for 5 min twice daily. Microradiography and image analysis of the recovered sections demonstrated significant protection of surface mineral loss from enamel and dentine by saliva in vitro and in situ compared with deionised water (p < 0.05). Significantly less mineral loss (p < 0.05) was observed for enamel and dentine stored in situ compared with storage in saliva in vitro. Generalised linear modelling demonstrated both the subject and protocol had significant effect on mineral loss. A weak positive correlation (r = 0.64) was noted when in situ and in vitro mineral loss from enamel were compared, demonstrating greater reactivity of the in vitro enamel specimens to the erosion challenge. The dentine data did not show any linear correlation. Saliva protected against mineral loss by erosion and, for enamel, in vitro results demonstrated a weak positive correlation with in situ results.

Fluoride release, microbial inhibition and microleakage pattern of two orthodontic band cements.

OBJECTIVES: To compare, in vitro, the fluoride release, microbial inhibition and microleakage pattern of a conventional glass ionomer cement (Ketac-Cem) and an acid-modified composite (Ultra Band-Lok) for band cementation. METHODS: Fluoride release was measured from cement discs (3.0 mm diameter and 1.5 mm thick) at regular intervals over 40 days using a potentiometric method. Microbial inhibition was determined for each cement using an agar diffusion test against one of four different strains of Streptococcus mutans. Thirty pairs of banded third molars (15 banded pairs for each cement) were thermocycled and microleakage determined by a dye penetration method. The depth of microleakage was assessed by an index applied by two examiners independently to photographic records taken of the mid-buccal aspect of each tooth. RESULTS: The cumulative and daily fluoride release for days 5, 15 and 40 were significantly greater for Ketac-Cem than for Ultra Band-Lok (all p < 0.05). After the initial set, the anti-microbial activity was significantly greater for Ketac-Cem than for Ultra Band-Lok over the following 24 h period for all four strains of S. mutans (all p < 0.05). There was no significant difference between the two cement groups for microleakage at the cement/enamel interface (p = 0.66) but a borderline significance was detected for microleakage at the cement/band interface (p = 0.051). CONCLUSIONS: The fluoride release and anti-microbial activity of Ketac-Cem were greater than that of Ultra Band-Lok. There was no significant difference in microleakage between the cements at the cement/enamel interface but a borderline difference existed between the cements at the cement/band interface.

Fluoride uptake and release characteristics of glass ionomer cements.

The aims of this study were firstly to investigate the fluoride-releasing characteristics of five commercial glass ionomer materials: Ketac Fil, Chemfil Superior, Fuji II LC, Aquacem and Vitrebond. The second aim was to assess the fluoride uptake and subsequent release from the same range of materials. In both tests, ten discs, 6 mm in diameter with a thickness of 1.5 mm, were made for each material. The initial fluoride release was assessed over a 60-day period for all materials. Each disc was immersed in 2 ml of de-ionised water within a plastic vial. The solutions were changed daily up to day 15, and thereafter every 3 and 4 days until the end of the test. All of the materials released measurable amounts of fluoride throughout the test period, with a considerable range on day 1 (15.3-155.2 ppm F). The concentration of fluoride released on the 2nd day fell sharply for all materials (range 6.3-44.3 ppm F). By day 60 all materials continued to release fluoride, albeit to a lesser extent (range 0.9-3.99 ppm F). With regard to the uptake and release of fluoride, a similar protocol was employed, although all samples were immersed in 1 litre of de-ionised water for 60 days to allow the majority of the fluoride to leach out from the materials. The ten pellets for each material were divided into two groups, five samples as control and five samples as test. Each day over a 20-day period all test samples were exposed to a 1000-ppm F solution for 2 min.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of fluoride-releasing bonding composites in the development of artificial white spot lesions. An ex vivo study.

This study investigates the effects of fluoride-releasing bonding composites on the development of artificially created white spot lesions ex vivo. The severity of the lesions was estimated visually using the von der Fehr Caries Index. The integrated mineral loss of the lesions (delta z) was measured using microradiography/microdensitometry. The results of the visual assessment indicated that teeth bonded with Reliance exhibited more Grade 2 lesions than expected. Teeth bonded with Mirage Dual Cure, however, showed a high prevalence of teeth with no lesions (Grade 0) and few with Grade 2. Microdensitometric analysis found 17 subsurface lesions; 14 of these were in the non-fluoridated groups (Right-On and Heliosit), and 3 and 1 in the fluoridated groups (Reliance and Mirage Dual Cure), respectively. Lesion mineral content ranged from 64.93 to 20.43 per cent for Right-On, from 32.53 to 26.72 per cent for Heliosit, from 19.52 to 19.58 per cent for Reliance, and 23.58 per cent for Mirage Dual Cure. The results of this study suggest that fluoride-releasing composites may have a caries preventive effect around orthodontic brackets.

An ex vivo investigation into the release of fluoride from fluoride-containing orthodontic bonding composites.

This study was concerned with an evaluation of fluoride release from commercially available orthodontic bonding composite resins, known as Reliance and Mirage Dual Cure, which are claimed to release ionic fluoride. Forty-eight premolar teeth had brackets bonded with four different composite resins--Mirage Dual Cure, Reliance, Right-on and Heliosit. They were then immersed in a demineralizing solution. The amount of fluoride released from the composites into the solution was measured. The results indicated that Mirage Dual Cure released statistically significant amounts of fluoride over the first 2 days. A similar pattern was noted with Reliance albeit releasing a lesser amount. From the third day onwards, fluoride release levelled out to concentrations similar to those of the two control materials, Right-on and Heliosit (i.e. 0.09 ppm). Fluoride-releasing composite resins, therefore, failed to demonstrate any potential long-term fluoride release within the ex vivo model. Even in the short term, the amount of fluoride released was very small.

The effect of saliva on fluoride release by a glass-ionomer filling material.

The initial aim of this study was to investigate the effect of saliva and the formation of pellicle on the fluoride release in vitro of the glass-ionomer filling material, Chemfil Superior. For the first study glass-ionomer discs of 6 mm in diameter and 1.5 mm thick were made. Ten discs were immersed in whole stimulated saliva each day for 10 min and 10 control discs were immersed in deionized water. For the remaining 23 h and 50 min of each day, over the 20-day experimental period, both test and control discs were placed in deionized water. A considerable amount of fluoride was released on the first day (14.5 ppm F control and 13.3 ppm F test). The concentration of fluoride released on the second day fell sharply to 5.3 ppm F for controls and 4.9 ppm F for tests. This release had almost reached a plateau by day 10 and at day 20 the pellets continued to release low levels of fluoride. The concentration of fluoride released was only slightly higher for controls than for test discs when both were immersed in deionized water until day 20. However, during the 10-min period between 1.5 and 2 times as much fluoride was released into the deionized water as into saliva until day 20 when the ratio fell to 1.2:1. The second experiment assessed fluoride release when specimens were incubated for 1 h using an identical protocol. Again, less fluoride was released from the saliva-coated specimens compared with the controls (17%), which was not substantially different to the comparable 10-min samples (13%). This study indicates that saliva retards the release of fluoride from glass-ionomer and that this retarding effect is still present when discs are subsequently immersed in water compared with those that were placed in water alone. This suggests that salivary deposits have formed within minutes of immersion in saliva. This retarding effect was observed throughout the study period with the exception of the 20-day samples which had been incubated in saliva for 10 min.

Caries detector dyes--an in vitro assessment of some new compounds.

Previous studies have shown that the caries detector dyes, basic fuchsin and acid red, lack specificity. Accordingly, their clinical use can lead to the unnecessary removal of sound tissue. In the present study, the specificity of three further dyes, Carbolan Green, Coomassie Blue and Lissamine Blue was studied. Carious dentine was removed in vitro by means of rotary instruments until the cavities were deemed caries free by conventional clinical criteria. Experimental dyes were applied to the cavity floors, all of which became stained. Stained dentine was removed from half the cavity by means of a burr, the other half remaining as a control. Further stain was then applied and the procedure repeated until no further reduction of the staining of the cavity floor could be achieved. Light microscopy of ground sections of experimental teeth showed that sound tissue had been removed unnecessarily from the experimental half of the cavity due to the lack of specificity of these dyes. This lack of specificity of staining was similar to basic fuchsin and acid red. Only Carbolan Green showed possible differential staining between control and experimental sites, but this was not caries specific. If a clinically useful dye is to be developed, it would need to specifically stain either bacteria in infected dentine and/or the carious degradation products of dentine matrix.

Buffering capacities of soft drinks: the potential influence on dental erosion.

The pH of fruit juices and carbonated drinks are known to be low and have, therefore, been implicated in the increasing incidence of erosion. The ability of a drink to resist pH changes brought about by salivary buffering may play an important part in the erosion process. The aims of this study were to measure the initial pH of several widely available soft drinks and determine their buffering capacities. As part of a larger study, the following groups of drinks were tested: pure fruit juices, non-fruit-based carbonated drinks, fruit-based carbonated drinks, flavoured spring waters, and plain carbonated mineral waters as positive controls with still water as the negative control. The measurement of pH was carried out using a pH electrode connected to an Orion EA940 Ionanalyser. One hundred millilitres of each drink was then titrated with 1 M sodium hydroxide, added in 0.5 mL increments, until the pH reached 10. Each titration was repeated three times. The average initial pH was lowest for the non-fruit-based drinks (2.81+/-0.274) and highest for plain mineral water (7.4+/-0.1002). The buffering capacities can be ordered as follows: fruit juices>fruit-based carbonated drinks and flavoured mineral waters>non-fruit-based carbonated drinks>sparkling mineral waters>still mineral water. It is concluded that fruit juices and fruit-based carbonated beverages, with their increased buffering capacities, may induce a prolonged drop in oral pH.

Calcium ion diffusion from calcium hydroxide-containing materials in endodontically-treated teeth: an in vitro study.

The aim of this in vitro study was to determine the amount and duration of diffusion of calcium ions from both a calcium hydroxide-containing root canal sealer and an intracanal medicament, through the apical foramen and the dentinal tubules of endodontically-treated teeth. The root canals of 88 freshly extracted single-rooted teeth were prepared using the modified double flared, balanced force technique with patency filing. The teeth were divided into four test groups of 20 teeth each and a control group of eight teeth. One group was dressed with a non-setting calcium hydroxide while the other was obturated using cold lateral condensation of gutta-percha with a calcium hydroxide-containing sealer. An artificial root defect was created in the apical third of the root of the teeth in the other two groups and the root canals were either dressed or obturated in the same way as the first two groups. All groups were incubated at 37 degrees C and were sampled for calcium diffusion after 1, 2 and 3 days and 1, 2, 3, 4 and 8 weeks. There was statistically significantly more calcium diffusion with the non-setting groups compared with the sealer groups (P < 0.05). There was more calcium ion diffusion from teeth with a patent apical foramen than those with an artificial resorptive root defect (P < 0.05).

Effect of fluoride exposure on cariostatic potential of orthodontic bonding agents: an in vitro evaluation.

AIMS: The aims of this in vitro study were to compare the cariostatic potential of a resin modified glass ionomer cement (Fuji Ortho LC) to that of a resin control (Transbond) for bracket bonding and to compare the effect of extrinsic fluoride application on the cariostatic potential of each material. SETTING: Ex vivo study. MATERIALS AND METHODS: Orthodontic brackets were bonded to 40 extracted premolars, 20 with Fuji Ortho LC and 20 with Transbond. The teeth were subjected to pH cycling, pH 4.55, and pH 6.8, over a 30-day period. Ten teeth bonded with each material were immersed in a 1000 ppm fluoride solution for 2 minutes each day. Fluoride release was measured throughout the study from all teeth. After 30 days, the teeth were assessed visually for signs of enamel decalcification. RESULTS: Significant differences in decalcification existed macroscopically between all four groups of teeth, with the exception of those bonded with Fuji Ortho LC alone compared with Transbond alone (P = 0.22), and Fuji Ortho LC alone compared with Transbond with added fluoride (P = 0.3). Fluoride release from Fuji Ortho LC alone fell to minimal values, but with the addition of extrinsic fluoride the levels fell initially and then followed an upward trend. There was minimal fluoride release, from Transbond alone, but with daily addition of extrinsic fluoride, subsequent fluoride release was increased. Significant differences existed in the amount of fluoride released between all groups, except comparing Fuji Ortho LC alone and Transbond with added fluoride. CONCLUSIONS: The results of this study have indicated that with an in vitro tooth-bracket model, the creation of white spot inhibition could best be achieved by the use of a resin-modified glass ionomer cement, supplemented with fluoride exposure. The least protection was afforded by the composite control. The resin-modified glass ionomer cement alone and the composite with added fluoride demonstrated equivalent protection.

Varnish or polymeric coating for the prevention of demineralization? An ex vivo study.

OBJECTIVE: The ability of an experimental coating, Odyssey, to prevent demineralisation ex vivo was compared with that of a fluoride varnish, Duraphat and a chlorhexidine-containing varnish, Cervitec. DESIGN: an ex vivo single-blind study. SETTING: Hard tissue research laboratory. MATERIALS AND METHODS: thirty bovine enamel blocks 0.5 cm x 1.5 cm were divided into 6 groups of 5 specimens. The enamel blocks were then allocated to one of 6 surface treatments. INTERVENTIONS: (1) surface left unprepared (control), (2) Duraphat application, (3) Cervitec application, (4) experimental polymer coating, (5) enamel conditioned with 10% citric acid and coated with the experimental polymer coating Odyssey (O + C), (6) enamel etched for 30 sec with 37% phosphoric acid and coated with the experimental coating (O + E). All specimens were cycled for 7 days through a daily procedure of demineralisation for 4 hours and remineralisation for 20 hours, and exposed to an equivalent of 2 months toothbrushing. A single operator blinded to the treatment allocation of each specimen carried artificial lesion depth assessment out using computer-assisted transverse microradiography. RESULTS: The control group had the greatest mean lesion depth (97.16 + 29.8 microm) with the Duraphat group exhibiting the lowest mean lesion depth (24.53 + 15.44 microm). The Duraphat, Odyssey, O + C and O + E groups all had significantly less lesion depth when compared with no surface preparation (p < 0.05 for all comparisons). There were no significant differences between any of the Odyssey groups. CONCLUSIONS: The efficacy of Duraphat application in preventing demineralisation ex vivo has been demonstrated in the present study, but clinical trials are required to assess its usefulness in orthodontic practice.