G D Walker

University of Melbourne, Melbourne, Victoria, Australia

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Publications (9)20.68 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Dental erosion is an increasingly prevalent problem in Australia, with the consumption of sports beverages suggested as a risk factor. The aim of this study was to compare the erosive potential of Australian sports beverages. Ten beverages were selected and analysed to determine their pH, titratable acidity and apparent degree of saturation with respect to apatite. The erosive potential of the beverages was measured by human enamel surface loss and surface softening following a 30-minute exposure. A taste testing panel was established to determine the palatability of the sports beverages. All sports beverages except Sukkie and Endura produced substantial surface loss and surface softening. Compared with the other sports beverages, Sukkie and Endura had a higher pH, lower titratable acidity and higher calcium content. However, Sukkie and Endura were deemed to be less palatable than the other more acidic sports beverages. The majority of the sports beverages tested produced dental erosion in this in vitro model. However, two new products Sukkie and Endura have lower erosive potential but also lower palatability.
    Australian Dental Journal 09/2012; 57(3):359-64; quiz 398. · 1.37 Impact Factor
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    ABSTRACT: Quantitative light-induced fluorescence (QLF) and digital photography (DP) have been proposed as clinical methods for measuring changes in enamel mineral content. The aim of this study was to compare the ability of QLF and DP with the in vitro gold standard transverse microradiography (TMR) to measure the remineralization of enamel subsurface lesions. Subsurface lesions were formed in enamel (n = 40) and exposed to remineralization solutions for 10 days. Changes were analysed by DP, QLF and TMR to determine percentage changes in luminescence (%L), fluorescence (%F) and mineral content (%R), respectively and correlation between these parameters determined. The correlations between TMR and QLF (r = 0.63), TMR and DP (r = 0.59), and DP and QLF (r = 0.64) were all moderate but statistically significant (p < 0.001). The variability in %L and, to a lesser extent, %F values significantly impacted on the potential role of DP and QLF as methods by which mineral content changes produced by remineralization treatments could be accurately measured. Both QLF and DP provided data that correlated moderately with TMR data. QLF images were easier to analyse, free of glare and had less variability compared with those produced using DP.
    Australian Dental Journal 09/2012; 57(3):271-6. · 1.37 Impact Factor
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    ABSTRACT: Remineralisation has been shown to be an effective mechanism of preventing the progression of enamel caries. The aim of this double-blind, randomised, cross-over in situ study was to compare enamel remineralisation by chewing sugar-free gum with or without casein phosphopeptide amorphous calcium phosphate (CPP-ACP) where the enamel lesions were exposed to dietary intake and some were covered with gauze to promote plaque formation. Participants wore removable palatal appliances containing 3 recessed enamel half-slabs with subsurface lesions covered with gauze and 3 without gauze. Mineral content was measured by transverse microradiography, and plaque composition was analysed by real-time polymerase chain reaction. For both the gauze-free and gauze-covered lesions, the greatest amount of remineralisation was produced by the CPP-ACP sugar-free gum, followed by the gum without CPP-ACP and then the no-gum control. Recessing the enamel in the appliance allowed plaque accumulation without the need for gauze. There was a trend of less remineralisation and greater variation in mineral content for the gauze-covered lesions. The cell numbers of total bacteria and streptococci were slightly higher in the plaque from the gauze-covered enamel for 2 of the 3 treatment legs; however, there was no significant difference in Streptococcus mutans cell numbers. In conclusion, chewing sugar-free gum containing CPP-ACP promoted greater levels of remineralisation than a sugar-free gum without CPP-ACP or a no-gum control using an in situ remineralisation model including dietary intake irrespective of whether gauze was used to promote plaque formation or not.
    Caries Research 04/2012; 46(2):147-55. · 2.51 Impact Factor
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    ABSTRACT: To investigate, in vitro, the effect on enamel erosion of the addition of 0.2% w/v casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) to four commercially-available soft drinks, two of which were carbonated. Enamel specimens (n=27) were sectioned from sound extracted human third molar teeth and polished to a mirror finish. Exposed enamel windows of 1 mm2 were created by painting the surface with acid-resistant nail varnish. Four citric flavoured soft drinks (pH range 2.2 to 2.4) and distilled deionized water (DDW) were tested. Each drink was tested with and without 0.2% CPP-ACP w/v. The specimens were placed into 50 mL of solution at 37 °C for 30 minutes, rinsed and varnish removed. The samples were profiled with a white light profilometer and erosive depths recorded. All soft drinks tested caused enamel erosion but adding 0.2% w/v CPP-ACP significantly reduced (p<.05) erosive depth in all test solutions in comparison with the solutions without CPP-ACP. The erosive depths for all solutions with 0.2% CPP-ACP did not differ significantly from those of DDW. Adding CPP-ACP at 0.2% w/v significantly decreased the erosivity of all four soft drinks. The erosivity of the soft drinks with 0.2% CPP-ACP added did not differ significantly from that of distilled water.
    Australian Dental Journal 09/2010; 55(3):275-9. · 1.37 Impact Factor
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    ABSTRACT: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has been demonstrated to exhibit anticariogenic activity in randomized, controlled clinical trials of sugar-free gum and a tooth cream. Two randomized, double-blind, crossover studies were conducted to investigate the potential of CPP-ACP added to hard candy confections to slow the progression of enamel subsurface lesions in an in situ model. The confections studied were: (1) control sugar (65% sucrose + 33% glucose syrup); (2) control sugar-free; (3) sugar + 0.5% (w/w) CPP-ACP; (4) sugar + 1.0% (w/w) CPP-ACP; (5) sugar-free + 0.5% (w/w) CPP-ACP. Participants (10 and 14 in study 1 and 2) wore a removable palatal appliance containing enamel half-slabs with subsurface lesions, except for meals and oral hygiene procedures, and consumed 1 confection 6 times a day for 10 days. The enamel half-slabs were inset to allow the development of plaque on the enamel surface. Participants rested for 1 week before crossing over to another confection. The appliances were stored in a humid container at 37 degrees C when not in the mouth. After each treatment period, the enamel half-slabs were removed, paired with their demineralized control half-slabs, embedded, sectioned and then analysed using transverse microradiography. In both studies consumption of the control sugar confection resulted in significant demineralization (progression) of the enamel subsurface lesions. However, consumption of the sugar confections containing CPP-ACP did not result in lesion progression, but in fact in significant remineralization (regression) of the lesions. Remineralization by consumption of the sugar + 1.0% CPP-ACP confection was significantly greater than that obtained with the sugar-free confection.
    Caries Research 01/2010; 44(1):33-40. · 2.51 Impact Factor
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    ABSTRACT: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is an anticariogenic agent that is suitable to be added to foods. The aim of this double-blind, three-way crossover randomized study was to investigate the capacity of CPP-ACP, when added to bovine milk, to remineralize enamel subsurface lesions in situ. Ten subjects drank 100 mL of bovine milk containing no added CPP-ACP (control milk), 0.2% (w/v) CPP-ACP or 0.3% (w/v) CPP-ACP, for 30 seconds once daily for 15 days, whilst wearing removable appliances with attached slabs of enamel containing subsurface enamel lesions. After each treatment and a one-week washout period, subjects crossed over to another treatment and this was repeated until they had consumed each of the three milk products. At the completion of each treatment the enamel slabs were removed and remineralization was determined using microradiography. The results demonstrated that all three milk samples remineralized enamel subsurface lesions in situ. However, the two milk samples containing added CPP-ACP each produced significantly greater remineralization than the control milk. The remineralizing effect of CPP-ACP in milk was dose-dependent with milk containing 0.2% CPP-ACP and 0.3% CPP-ACP producing an increase in mineral content of 81% and 164%, respectively, relative to the control milk.
    Australian Dental Journal 10/2009; 54(3):245-9. · 1.37 Impact Factor
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    ABSTRACT: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slows the progression of caries and remineralizes enamel subsurface lesions. The aim of this study was to determine the ability of CPP-ACP to increase the incorporation of fluoride into plaque and to promote enamel remineralization in situ. Randomized, double-blind, cross-over studies involved mouthrinses and dentifrices containing CPP-ACP and fluoride. The mouthrinses were used for 60 sec, three times/day for 5 days, and supragingival plaque was collected and analyzed for F. The dentifrices were rinsed as a water slurry for 60 sec four times/day for 14 days in an in situ model. The addition of 2% CPP-ACP to the 450-ppm-F mouthrinse significantly increased the incorporation of fluoride into plaque. The dentifrice containing 2% CPP-ACP produced a level of remineralization similar to that achieved with a dentifrice containing 2800 ppm F. The dentifrice containing 2% CPP-ACP plus 1100 ppm F was superior to all other formulations.
    Journal of Dental Research 05/2008; 87(4):344-8. · 3.83 Impact Factor
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    ABSTRACT: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has been shown to remineralize enamel subsurface lesions in situ. The aim of this study was to investigate the effects of CPP-ACP in a fruit-flavoured sugar-free chewing gum containing citric acid on enamel remineralization, and acid resistance of the remineralized enamel, using an in situ remineralization model. The study utilized a double-blind, randomized, crossover design with three treatments: (i) sugar-free gum (2 pellets) containing 20 mg citric acid and 18.8 mg CPP-ACP, (ii) sugar-free gum containing 20 mg citric acid alone, (iii) sugar-free gum not containing CPP-ACP or citric acid. Ten subjects were instructed to wear removable palatal appliances, with 4 half-slab insets of human enamel containing demineralized subsurface lesions and to chew gum (2 pellets) for 20 min 4 times per day for 14 days. At the completion of each treatment the enamel half-slabs were removed and half of the remineralized lesion treated with demineralization buffer for 16 h in vitro. The enamel slabs (remineralized, acid-challenged and control) were then embedded, sectioned and subjected to microradiography to determine the level of remineralization. Chewing with gum containing citric acid and CPP-ACP resulted in significantly higher remineralization (13.0 +/- 2.2%) than chewing with either gum containing no CPP-ACP or citric acid (9.4 +/- 1.2%) or gum containing citric acid alone (2.6 +/- 1.3%). The acid challenge of the remineralized lesions showed that the level of mineral after acid challenge was significantly greater for the lesions exposed to the gum containing CPP-ACP.
    Caries Research 02/2007; 41(5):377-83. · 2.51 Impact Factor
  • E C Reynolds, F Cai, P Shen, G D Walker
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    ABSTRACT: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes incorporated into sugar-free chewing gum have been shown to remineralize enamel subsurface lesions in situ. The aim of this study was to compare the ability of CPP-ACP, with that of other forms of calcium, to be retained in supragingival plaque and remineralize enamel subsurface lesions in situ when delivered in a mouthrinse or sugar-free gum in randomized, double-blind trials. In the mouthrinse study, only the CPP-ACP-containing mouthrinse significantly increased plaque calcium and inorganic phosphate levels, and the CPP were immunolocalized to the surfaces of bacterial cells as well as the intercellular matrix. In the chewing gum studies, the gum containing the CPP-ACP, although not containing the most calcium per piece of gum, produced the highest level of enamel remineralization independent of gum-chewing frequency and duration. The CPP could be detected in plaque extracts 3 hrs after subjects chewed the CPP-ACP-containing gum. The results showed that CPP-ACP were superior to other forms of calcium in remineralizing enamel subsurface lesions.
    Journal of Dental Research 04/2003; 82(3):206-11. · 3.83 Impact Factor