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Introduction: The purpose of this in vitro study was to determine if enamel that had been bleached by carbamide (urea) peroxide gel (CPG) was at increased risk of either acid erosion or demineralisation (early caries) than un-bleached enamel.Methods: Human incisors were employed. The samples were randomly assigned to one of 4 groups; a) 10% CPG, b) 16% CPG, c) 22% CPG and d) 10% CPG with xylitol, fluoride and potassium. Each specimen was moistened with saliva and the appropriate formulation placed for 2 hours for a total of 40 hours of exposure. In order to ensure that bleaching had taken place, tooth shades were monitored using the Shade-Eye device. Following the bleaching process, one half of the specimen was subjected to an erosive challenge, the other to a demineralisation system with one half of each sub-sample retained as a non-bleached control. Samples were assessed longitudinally with quantitative light-induced fluorescence (QLF) and at the conclusion of the study with transverse micro-radiography (TMR).Results: Erosion was detected in all samples (DeltaQ 126+/-23.4), in both bleached and non-bleached areas. There was no statistical difference between the bleached and non-bleached areas either within the treatment groups or between them. Caries-like lesions were detected on all samples; TMR revealed sub-surface lesions on all teeth and QLF data supported this (DeltaQ 89+/-18.9). Following statistical analysis there were no differences detected between the bleached and non-bleached areas, nor between the different concentrations of the bleaching solution.Conclusion: These results suggest that tooth bleaching with carbamide (urea) peroxide (using commercially available concentrations) does not increase the susceptibility of enamel to acid erosion or caries. [ABSTRACT FROM AUTHOR]

Objective: To determine the effects of a detergent-free, whitening dentifrice using an in vivo plaque regrowth model with the novel application of QLF as a planimetric analysis tool.Method: A total of 20 subjects took part in a double blind, single-centre, crossover study in which slurry rinses were the only form of plaque control over a 5-day period. Following a washout and prophylaxis the subjects used 2 daily rinses in the absence of all other plaque control methods. Subjects returned to the clinic on the afternoon of day 5 when plaque was disclosed and assessed by the plaque index and area using both a photographic and novel fluorescent planimetric technique. A further 9-day washout was carried out and the rinse period repeated to ensure that each subject had used both experimental and comparator slurries.Results: Twenty subjects completed the trial. The test product showed a significant inhibition of plaque re-growth (16.9%) compared with a fluoride-matched comparator using the Turesky index (P < 0.0001), the photographic planimetric technique (17.5%) (P < 0.0001) and the novel QLF technique (18.4%) (P < 0.0001).Conclusion: The results confirm that plaque inhibition capability of a detergent-free whitening dentifrice is at least as effective as a fluoride matched comparator. QLF is a promising tool for disclosed plaque quantification. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effect of hydration [distilled water (DH2O) and saliva] on lesions of varying severity and determine an optimal drying method to obtain reliable quantitative light-induced fluorescence (QLF) readings. Ten previously extracted molars were placed into a demineralizing solution for 7, 14 and 21 days. Between each demineralizing cycle the teeth were removed. To test for in vitro reliability the teeth were rinsed in DH2O for 1 min and then QLF images were taken every 10 s (control cycle with no drying employed – bench drying only). This was repeated following (i) compressed air drying for 30 s or 15 s and (ii) 30 s cotton wool roll application (CWR). To test for in vivo reliability the experiment was repeated using whole human saliva in place of DH2O. Control groups demonstrated the effect of hydration on QLF reliability; at 7 days reliable results were obtained after 370·4 s (DH2O) and 432·3 s (saliva). Air drying of both DH2O and saliva-rinsed teeth reduced reliability time to 2·1 (±6·0) and 3·2 s (±7·6), respectively. Cotton wool roll application produced reliable results in 89 s with DH2O and 110 s with saliva. As lesion severity increased [14 days mean Δ Q 115 (±90·2), 21 days mean Δ Q 168·0 (±120·7)] time to reach reliability significantly increased under control drying and CWR ( P > 0·05). Time taken for compressed air-dried teeth to produce reliable results was not significantly different across the groups. Compressed air-drying for 15 s produces reliable results with both DH2O and saliva-hydrated lesions. Future in vivo experiments will be required to determine if the air-drying can be reduced further in a clinical situation. [ABSTRACT FROM AUTHOR]

The use of optical methods in the diagnosis of early caries is developing rapidly. The introduction of the quantitative light-induced fluorescence (QLF) device has promised the use of a quantifiable technique in vivo . This study describes the effect that ambient light has upon the reliability of QLF analyses. Using human teeth and simulated lesions the study examined the effect of 15 different light levels on three severities of carious lesions. The study found that a light level of 88 lux could be employed in areas where QLF is to be used without significantly affecting the reported value, ΔQ . This study impacts upon the health and safety issues surrounding QLF usage as well as ethical issues relating to working in dark environments. [ABSTRACT FROM AUTHOR]

In 2 separate studies, plaque was harvested (i) from 15 smokers and 15 non-smokers after a 48-h period without oral hygiene, and (ii) from 15 smokers and 12 non-smokers after a 48 h hygiene-free period following complete plaque removal by toothbrushing. No significant association emerged between wet weight of accumulated plaque and cigarette smoking, in either study. In the second study, the mean plaque calcium concentration was raised in smokers compared with non-smokers, and significantly raised in 7 heavy smokers relative to non-smokers. In both instances, calcium concentration was significantly raised relative to (total) phosphorus concentration, which may indicate that the additional calcium was not in mineral deposits. These results may reflect an association between calcium concentration of plaque and tobacco consumption. [ABSTRACT FROM AUTHOR]

An obituary for George Neil Jenkins, the first professor of oral physiology in Great Britain, is presented.

ObjectiveTo determine the effects of a detergent-free, whitening dentifrice using an in vivo plaque regrowth model with the novel application of QLF as a planimetric analysis tool.MethodA total of 20 subjects took part in a double blind, single-centre, crossover study in which slurry rinses were the only form of plaque control over a 5-day period. Following a washout and prophylaxis the subjects used 2 daily rinses in the absence of all other plaque control methods. Subjects returned to the clinic on the afternoon of day 5 when plaque was disclosed and assessed by the plaque index and area using both a photographic and novel fluorescent planimetric technique. A further 9-day washout was carried out and the rinse period repeated to ensure that each subject had used both experimental and comparator slurries.ResultsTwenty subjects completed the trial. The test product showed a significant inhibition of plaque re-growth (16.9%) compared with a fluoride-matched comparator using the Turesky index (P<0.0001), the photographic planimetric technique (17.5%) (P<0.0001) and the novel QLF technique (18.4%) (P<0.0001).ConclusionThe results confirm that plaque inhibition capability of a detergent-free whitening dentifrice is at least as effective as a fluoride matched comparator. QLF is a promising tool for disclosed plaque quantification. [ABSTRACT FROM AUTHOR]

summary The influence of abrasion from oral soft tissues on softened enamel lesion remineralization and erosion development was investigated. Using orange juice, softened enamel lesions were produced on 20 human premolars assigned randomly to 10 volunteers. Sections used as control and two test slabs were cut from each tooth. One of the two slabs from each tooth had an appliance built on it, which protected the lesion from abrasion. The two slabs (with/without appliance) were bonded to the palatal surfaces of upper right and left lateral incisor teeth of the participants who chewed sugar-free gum four times daily. After 28-day intra-oral exposure, mineral loss (ΔZ ) and lesion depth (ld) in both control and test samples were quantified using transverse microradiography, and the data was analysed by paired t -test. ΔZ was significantly lower in lesions with appliance (protected), but higher in lesions without appliance (unprotected) when compared with control (unexposed). Similar pattern was observed with lesion depth. In unprotected slabs the lesions were abraded resulting in eroded enamel lesions. It was concluded that erosion observed clinically is the combined effect of demineralization of the tooth surface by an erosive agent and abrasion of the demineralized surface by surrounding oral soft tissues and through food mastication. Abrasion from oral soft tissues can contribute to site-specificity of dental erosion. [ABSTRACT FROM AUTHOR]

The dose of gamma irradiation sufficient to sterilize enamel samples to be used for intra-oral cariogenicity tests (ICT) without alteration to the structure or solubility of the enamel was determined. Each bovine incisor used was cut vertically into eight portions and each portion assigned to one of eight groups. Group 1 was used as control while other groups were subjected to respective doses of gamma irradiation from a cobalt-60 source. Following sterilization, both control and experimental groups were incubated in nutrient broth for 7 days at 37 °C under aerobic and anaerobic conditions. Caries-like lesions were subsequently produced in each specimen using acidic buffer solution, and mineral loss quantified using transverse microradiography. Data were analysed statistically. There was no significant difference in mineral loss between the control and experimental groups, but the numerical value of mineral loss was lower in groups irradiated with> 4080 Gy, in addition to full sterilization and enamel discoloration to cream colour observed in these groups. Microbial growth was observed in the control group and in groups irradiated with <4080 Gy but no discoloration. With 4080 Gy full sterilization without discoloration was observed. It was concluded that 4080 Gy of gamma irradiation is optimal for sterilization of enamel samples for use in ICT. [ABSTRACT FROM AUTHOR]

The influence of temperature, duration of exposure, and enamel type on the development and progression of dental erosion has been determined. Three experiments were devised as follows. Eroded lesions were produced on enamel samples with orange juice: (1) at different temperatures; (2) for different lengths of time; and (3) on bovine permanent, human deciduous and human permanent enamel. Lesion parameters (mineral loss and lesion depth) were quantified using transverse microradiography. Both lesion parameters were significantly lower at 4 °C when compared with 20 °C and 37 °C, and at 20 °C when compared with 37 °C. Lesion parameters increased significantly as the length of exposure increased, and were positively correlated (r=0·98, P<0·05) to the exposure time. Both parameters were significantly greater in bovine enamel than human permanent and deciduous enamel, and in human deciduous than permanent enamel. Lesion progression, as measured by mineral loss, was in the ratio 2·0:1·5:1·0 for bovine:human deciduous:human permanent, and by lesion depth, 1·7:1·3:1·0. In conclusion, the erosiveness of orange juice was less pronounced at a lower temperature, and increased with an increased exposure time. Erosion progressed twice as fast in bovine permanent than in human permanent enamel, and 1·5 times more rapidly in human deciduous than in permanent enamel. [ABSTRACT FROM AUTHOR]

This project firstly demonstrated an in vitro technique for the production of eroded lesions which simulates the in vivo conditions, and secondly evaluated the influence of salivary parameters on the degree of erosion in vitro. Teeth were sectioned sagitally into three equal portions. The portions were randomly assigned to one of three experimental groups (A, B and C). Lesions were produced by cycling the teeth between orange juice and either artificial saliva (A) or water (B) for a total period of 12 h, or by a single 12 h immersion in orange juice (C). Sections were prepared from each specimen and mineral loss was quantified using transverse microradiography. Mineral loss was significantly lower in group A compared with B and C. Greatest mineral loss was observed in B though not significant when compared with C. The present technique mimics the in vivo conditions with the saliva reducing the degree of erosion and possibly remineralizing the lesions. [ABSTRACT FROM AUTHOR]

The use of fluorescein-enhanced quantitative light-induced fluorescence (QLF) in the detection of in vitro root caries demineralization and reminerlization was investigated. Fourteen previously extracted human premolar roots were selected and determined to be caries-free. Cementum was removed and nail varnish applied leaving an exposed window. Positive and negative controls were selected. During a demineralizing regimen, roots were removed at regular intervals (12, 48, 72 and 120 h) and immersed in sodium fluorescein (0·2 mg L−1). Following gentle rinsing, each root was examined using QLF before being returned to the demineralizing solution. Following 120 h, each tooth was sectioned through the lesion and one-half retained for transverse micro radiography (TMR) analysis. The remaining half were subjected to a remineralizing regimen undergoing the same fluorescein and QLF examinations at 7, 28 and 36 days. Results showed that QLF effectively monitored demineralization/remineralization of root dentine as represented by fluorescein penetration. TMR analysis showed good correlations with QLF (Δ Z/Δ Q) after demineralization ( r = 0·89) and remineralization ( r = 0·84). The technique could represent an in vivo method for root caries detection and classification. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the acid anions produced in plaque after chewing various cereal-based foods and fruits for one minute. Test foods were oranges, apples, bananas, Cornflakes®, Branflakes®, Weetabix®, Alpen®, white bread, wholemeal bread, rice and spaghetti, plus positive and negative controls of 10% sucrose and 10% sorbitol, 4 males and 3 females, aged 22-37 years, participated in the study. 7 min from the start of chewing, 48-h plaque was collected from all accessible smooth surfaces, with no attempt to collect interproximal plaque, and centrifuged. Plaque fluid was withdrawn and analyzed by iso-tachophoresis for formate, succinate, lactate. acetate and propionate. At rest, acetate was the major anion present in plaque fluid, whereas following carbohydrate consumption, highest levels of lactate were detected followed by acetate. The amount of lactate only, detected in plaque fluid, was significantly correlated to the carbohydrate present in the food. It was concluded that important information regarding the acidogenicity of test foods is gained by studying the acid anion profile of plaque fluid. [ABSTRACT FROM AUTHOR]