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PubMed2006

The effect of adjacent dentine blocks on the demineralisation and remineralisation of enamel in vitro.

The aim was to investigate interactions between enamel and dentine at low pH under conditions simulating those at the enamel-dentine junction. Sound enamel blocks were demineralised in acid-gel systems, at pH 4.6, either in isolation, next to one, or in the middle of two, abutting dentine blocks. The gels were initially infinitely undersaturated with respect to enamel. In a second study, enamel blocks containing pre-formed lesions were placed in acid-gel systems, at pH 5.0, either in isolation or next to dentine blocks. The systems were initially either partially or infinitely undersaturated. In the partially saturated systems, calcium and phosphate concentrations were representative of plaque fluid. In the first study, demineralisation of enamel next to one dentine block was reduced in inverse proportion to the distance from the dentine. Demineralisation of enamel between two dentine blocks was retarded markedly across the whole block. In the second study, in the partially saturated systems, enamel lesions next to dentine blocks remineralised, whereas those in isolation demineralised further. We suggest that diffusion of dissolved dentine mineral over the enamel in the infinitely undersaturated system was sufficient to reduce undersaturation, thus retarding demineralisation, and that in the partially saturated systems, dentine dissolution together with the added calcium phosphate caused remineralisation of enamel lesions. Fluoride released from dissolving dentine may have augmented these effects. Different rates of demineralisation in enamel and dentine, or enamel remineralisation with concurrent dentine demineralisation, enabled by differences in their solubilities, could help explain the progression of so-called 'hidden caries'.

Analysis of Variance↗
PubMed2006

Prevention of erosion and abrasion by a high fluoride concentration gel applied at high frequencies.

The aim of this study was to determine maximum attainable protection of enamel from erosion and erosion abrasion using a highly fluoridated gel with and without additional fluoride from toothpaste. Thirty-six bovine enamel specimens were subjected to six erosive attacks per day (1% citric acid with pH 2.3 for 30 s), while the rest of the day the specimens were in artificial saliva. There were four treatment groups (9 specimens in each group): fluoride-free toothpaste/saliva slurry twice daily (group T0), fluoride-containing toothpaste/saliva slurry twice daily using 1,250 ppm F toothpaste (group TF), fluoride-containing toothpaste/saliva slurry twice per day plus application of a highly fluoridated gel (12,500 ppm F) twice a day for 120 s (group 2F) and a group with gel application 8 times a day (group 8F). Additionally, half of each specimen in all groups was subjected to brushing abrasion during application of the toothpaste/saliva slurry. Brushing abrasion alone led to no observable enamel loss measured with profilometry. After 14 days of cycling of erosion without toothbrushing abrasion, high-fluoride gel application 2 or 8 times daily showed significantly less enamel loss (median 24/19 microm) than with toothpaste with or without fluoride (41/45 microm). After 14 days of cycling of erosion and toothbrushing abrasion, gel application 2 or 8 times daily (33/29 microm) showed significantly less enamel loss than toothpaste with or without fluoride (57/62 microm). We conclude that a highly fluoridated acidic gel is able to protect enamel from erosion and toothbrushing abrasion while fluoridated tooth paste provides little protection.

Amines↗
PubMed2006

The effect of fluoride at plaque fluid concentrations on enamel de- and remineralisation at low pH.

The aim was to study the effect of fluoride, at concentrations typical of plaque fluid, on de- and remineralisation of subsurface lesions at low pH. Artificial lesions in human enamel were microradiographed to quantify mineral loss and placed in acid-gel systems at pH 4.8, 5.0 and 5.2. Calcium and phosphate were added to give initial Ca and Pi concentrations of either 4.1 and 8.0 mM, or 4.7 and 9.7 mM, at each pH value. Further, at each pH and combination of Ca and Pi, fluoride was added to the gels to give initial concentrations of 1, 2 or 5 ppm, with a non-fluoride control group. The lesions were removed after 10 days and change in mineral content quantified. Those in the non-fluoride control groups had demineralised further. Those exposed to fluoride had remineralised, the amount increasing with increasing fluoride concentration, up to a maximum value of approximately 75%. Calcium activity in the gels was reduced significantly, to levels similar to those reported for plaque fluid at low pH. Fluoride activity was also reduced, though to a lesser extent. These findings contrast with those from studies which have simulated conditions on smooth surface sites and which used experimental solutions composed to reflect salivary fluoride concentrations, where net demineralisation was observed at low pH. This reflects the need for further study of de- and remineralisation under plaque-fluid conditions. In conclusion, subsurface lesions were remineralised at low pH by fluoride at concentrations found in plaque fluid during a cariogenic challenge.

Adult↗
PubMed2006

The effect of lesion characteristics at baseline on subsequent de- and remineralisation behaviour.

The aim was to study the effect of lesion characteristics at baseline on subsequent de- and remineralisation behaviour. Artificial lesions used during in vitro and intra-oral studies exhibit an increasing tendency toward net remineralisation with increasing integrated mineral loss at baseline (DeltaZ(base)). Proposed explanations include: (i) small lesions may be more vulnerable to demineralisation, and (ii) large lesions may be more difficult to remineralise. To evaluate these hypotheses, subsurface lesions were created in numerous blocks of human and bovine enamel, with a range of depths and DeltaZ(base), measured by microradiography. One group of lesions was further demineralised, a second group remineralised, and subsequently, both groups re-analysed. Under demineralising conditions, there was a marked decrease in further mineral loss with increasing DeltaZ(base). Under remineralising conditions lesions gained mineral in proportion to DeltaZ(base). The decrease in demineralisation of lesions with larger DeltaZ(base) may be partially a result of decreased intrinsic solubility through modified chemical composition, e.g. loss of magnesium, carbonate etc. The results may explain the tendency toward net remineralisation with increasing DeltaZ(base) in pH-cycling regimes.

Acids↗
PubMed1992

Influence of fluoride and pH on in vitro remineralization of bovine enamel.

Subsurface lesions in bovine enamel slices were remineralized. The remineralization solutions contained either 0.03, 0.3, or 1.0 ppm fluoride at either pH 5.5 or 6.8. The amount of remineralization was determined after periods of up to 610 h, using quantitative microradiography. The results showed that after 126 h of remineralization in the presence of 0.03 ppm fluoride significantly (p less than 0.05) more remineralization occurred at pH 6.8 than at pH 5.5. At 0.3 and 1.0 ppm fluoride no significant differences between pH 5.5 and pH 6.8 were observed. An interaction between fluoride and pH was observed. The observed differences in the rates of remineralization are explained by the formation and subsequent transformation of the precursors octacalcium phosphate (pH 6.8) and brushite (pH 5.5) into (fluor)apatites.

Animals↗
PubMed1992

A flexible and rapid pH cycling procedure for investigations into the remineralisation and demineralisation behaviour of human enamel.

A rapid and flexible model system has been developed to study human enamel behaviour under conditions of oscillating pH similar to those experienced in the mouth. The model uses realistic time intervals and operates at in vivo temperatures (35-37 degrees C). Mineral loss or gain is measured quantitatively on a volume basis. Results indicate that for single 1-day periods with three 20-min exposures to acid, 1% v/v of enamel mineral was lost. These results, together with the histological appearance of the tissue, are in close agreement with previous studies of enamel caries.

Calcium↗
PubMed1992

Noncariogenicity of maltitol in specific pathogen-free rats infected with mutans streptococci.

The effect of maltitol on caries development was examined in an experimental caries system employing specific pathogen-free (SPF) Sprague-Dawley rats. Fourteen strains of oral streptococci, including mutans streptococci, did not utilize the maltitol nor produce sufficient acid to demineralize tooth enamel. Furthermore, maltitol did not serve as a substrate for glucosyltransferases of either Streptococcus mutans MT8148R or Streptococcus sobrinus 6715 to synthesize water-insoluble glucan. Maltitol induced no significant dental caries in SPF rats infected with these mutans streptococci, and replacement of the dietary sucrose content with maltitol resulted in a trend towards caries reduction in SPF rats.

Animals↗
PubMed1992

Effect of hard cheese exposure, with and without fluoride prerinse, on the rehardening of softened human enamel.

The in situ rehardening effect was compared between Cheddar cheese consumption and saliva secretion with and without a fluoride pretreatment on softened human enamel. Ten volunteers wearing prostheses which held slices of human enamel participated in this study. Average microhardness of enamel was determined on the surface at baseline, after exposing to an acidic beverage, after exposing to saliva and mastication of cheese, with and without a mouth F prerinse (10 ml Meridol containing 0.025% F). The rehardening was increased in the groups consuming cheese compared to the saliva controls. The effect was increased by an F prerinse; the initial hardness of the intact enamel surface, however, was not reached.

Amines↗
PubMed1992

Validity of probing for fissure caries diagnosis.

One hundred extracted molar teeth with discoloured fissures but without any visible carious cavitation were selected from a large supply, using standardized criteria. The teeth were mounted, placed on a mechanical balance, and probed with a force of 500 g in every fissure, at as many places as possible. Every time the probe was found to stick, the spot was marked. After probing colour slides were made of the occlusal faces. Subsequently, the crowns were embedded in epoxy resin. 700 microns thick sections were cut in a facial-lingual direction with a diamond wheel. From the sections X-rays were taken which were scored as follows: a measuring grid was placed on the X-ray image of a section, and the caries score (0-4) for every millimetre was determined. By scoring every section of a tooth in this way, an overview was obtained of the location of all caries lesions in the occlusal surface. By comparing this overview with the colour slide of the tooth, the relationship between the sticky spots and the lesions was visualized. The results indicate that only 24% of the caries lesions were discovered by probing for stickiness (low sensitivity), but that the probe seldom stuck in a sound fissure (high specificity, > 99%). Probing proved to be unreliable for the diagnosis of fissure caries.

Dental Enamel↗
PubMed1992

Effects of chewing gums sweetened with sorbitol or a sorbitol/xylitol mixture on the remineralisation of human enamel lesions in situ.

Intra-oral remineralisation of experimental caries-like lesions in human enamel, as determined by polarised light microscopy and quantitative microradiography, was promoted to a similar extent (% fall in delta Z, 18.6 and 19.0) by chewing a sorbitol or sorbitol/xylitol (3:1)-sweetened gum for 20 min after each of three meals and two sugary snacks daily. The results suggest that reported differences in the properties of the two sweeteners do not affect their ability to enhance remineralisation due to salivary stimulation.

Adult↗
PubMed1993

Rehardening of surface softened and surface etched enamel in vitro and by intraoral exposure.

The rehardening of surface-softened and surface-etched enamel was investigated in vitro and by intraoral exposure. Surface-softened enamel was obtained by treatment with 0.1 M acetic acid buffer solution (pH = 5.5) for 3 h. Surface-etched enamel was obtained by the acid etch procedure used in clinical situations (37% phosphoric acid gel, 30 s). The enamel lesions were treated in vitro, with calcifying solutions for 8 h or were carried for 48 h in an intraoral appliance. Changes at the enamel surfaces were investigated by surface microhardness measurements. Following the treatment with calcifying solutions a significantly greater indentation length was observed in surface-etched than in surface-softened enamel. No significant difference in indentation length between both types of enamel lesions was observed following intraoral exposure. It was concluded that the initial rate of rehardening between both types of enamel lesions is comparable. At his stage remineralization occurs in microspaces created in the slightly destroyed enamel structures. The influence of the etch pits on the indentation length becomes dominating when remineralization continues. An obliteration of etch pits was observed in enamel samples treated with the calcifying solution with the highest degree of saturation. It was suggested that freshly prepared highly supersaturated calcifying solutions can be used to enhance mineral appositions in accidental etch pits.

Acetates↗
PubMed1993

In situ remineralization of subsurface enamel lesion after the use of a fluoride chewing gum.

In situ remineralization of early enamel lesions by a fluoride chewing gum was studied. Human enamel specimens with subsurface lesions were mounted in removable lower appliances for 6 adults. Subjects used a F-free dentifrice 3x/day and chewed five sticks/day for the F gum group (0.1 mg F/stick) or five sticks of sugarless gum. No gum was chewed for controls. Surface microhardness was performed on: (1) sound enamel; (2) lesions; (3) after intraoral exposure, and (4) after acid-resistance testing (ART). Separate specimens were etched and measured for F uptake and image analyses on microradiographs were performed for all regimens. delta Z values were calculated and converted to percent of mineralization. Values for F gum were significantly higher (p > 0.05) than non-F gum and controls for ART, percent remineralization, and F uptake up to 70 microns depth.

Adult↗
PubMed1993

Microbiological validation of assessments of caries activity during cavity preparation.

The operative management of primary and secondary caries assumes that all discoloured tissue at the enamel-dentine junction (EDJ) represents active disease and this is removed to arrest the carious process. This study aims to establish clinical criteria to differentiate between active and arrested caries at the EDJ using microbiological assessment of dentine samples to verify its clinical status. Radiographs were available for posterior teeth. Cavities (n = 205) were prepared under rubber dam. After gaining access, areas of the EDJ were chosen and assessments made of consistency (soft, medium, hard), colour (dark brown, mid-brown, pale) and moisture content (wet, dry). Dentine was removed by using a No. 3 round burr and placed in 1 ml of bacteriological culture broth. This sampling procedure was repeated at the same site once during cavity preparation and again when the cavity was judged as fully prepared. Samples were vortexed, diluted and cultured to give viable counts of the total anaerobic microflora, mutans streptococci and lactobacilli; viable counts were expressed as log10 (CFU per sample +1). Results showed no significant differences between the microflora of primary and secondary caries. The number of bacteria recovered diminished significantly as cavities were completed. Initial samples from soft and wet lesions harboured significantly more bacteria, lactobacilli and mutans streptococci than samples from medium, hard or dry lesions. Lesions visible on radiographs harboured more bacteria, including lactobacilli and mutans streptococci, while dentine colour was not discriminatory.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Comparison of different methods for the diagnosis of fissure caries without cavitation.

The aim of this study was to compare the accuracy of several common methods for the diagnosis of fissure caries. 63 human teeth without fillings and without any macroscopic carious cavitation but with different degrees of fissure discoloration and decalcification were selected from a pool. Dentists were asked to examine embedded teeth for fissure caries. The examination was done under standard conditions in a professional dental unit. The methods employed were: visual inspection (VI, n = 26 dentists), visual inspection with a magnifying glass (2x; VIM; n = 26), conventional bite-wing radiography (BW; n = 24), visual inspection combined with conventional bite-wing radiography (VI + BW; n = 10), and visual inspection combined with light pressure probing (VI + P; n = 23 dentists). In order to measure the reproducibility, VI and VI + BW were repeated. After the last inspection, the teeth were histologically prepared, serially sectioned perpendicular to the occlusal surface, and diagnosed for the presence of caries. The agreement between histological and clinical diagnosis was assessed. Specificities and sensitivities were: VI = 93 and 12%, VIM = 89 and 20%, BW = 83 and 45%, VI + BW = 87 and 49%, and VI + P = 93 and 14%, respectively. The following likelihood ratios were found: VI = 1.84, VIM = 1.86, BW = 2.6, VI + BW = 3.85, and VI + P = 2.05. It was concluded that the rather low sensitivity especially for VI and VI + P may lead to a significant number of teeth with dentinal caries being undetected.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Enamel↗
PubMed1993

In situ remineralization of enamel lesions using continuous versus intermittent fluoride application.

Remineralization of early enamel lesions was studied in situ using a F chewing gum or a F-releasing device (FRD). Enamel specimens with subsurface lesions were mounted in removable lower appliances in 6 adults. A F-free dentifrice was used for all regimens. Test groups chewed five sticks/day (0.1 mg F/stick), or one FRD (0.5 mg F/day) was mounted in the midline of the appliance. The microhardness was measured after the 21-day intraoral exposure, and in vitro acid resistance testing was performed. Separate specimens were used to measure F content or changes in mineral density. Comparable values for both F gum and FRDs were higher (p > 0.05) than controls for acid resistance testing and percent remineralization. The F content for FRDs exceeded that of both F gum and controls.

Adult↗
PubMed1994

Effect of fluoride varnish and solution on enamel erosion in vitro.

The effect of fluoride varnish and solution on initial enamel erosion was studied. Enamel specimens prepared from human third molars were treated for 24 h with Duraphat varnish (2.26% F) or for 48 h with NaF solution (1.2% F), washed, and immersed in cola beverage (pH 2.6) for up to 15 min. The surface microhardness was measured using a Vickers diamond in a Leitz indentation apparatus at base-line, after fluoride treatment, and after 1, 5, and 15 min exposure to acidic drink. The specimens were then prepared and studied using a JEOL JSM-35 scanning electron microscope. The results showed that both fluoride treatment caused an increase in enamel hardness values and subsequent inhibition of softening which was statistically highly significant. Scanning electron micrographs revealed the difficulty of removing Duraphat varnish from the enamel surface, and remnants of varnish were seen irrespective of vigorous sonication in acetone. However, in areas devoid of varnish, erosion was observed as mainly irregular lesions similar to those seen in the NaF solution treated and control specimens. The present study showed that treatment of enamel with topical fluoride prior to acidic challenge can inhibit initial erosion.

Adult↗