Graham G. Craig

The inability of Streptococcus mutans and Lactobacillus acidophilus to form a biofilm in vitro on dentine pretreated with ozone

BACKGROUND The use of ozone therapy in the treatment of dental caries is equivocal. The aim of this study was to use an in vitro model to determine the effects of prior ozone application to dentine on biofilm formation and to measure any associated reduction in bacteria viability. METHODS Twenty dentine discs were bonded to the bases of 5 mL polycarbonate screw top vials. Ten dentine discs were infused with ozone for 40 seconds, 10 samples remained untreated as a control. The vials were filled with nutrient medium, sterilized and placed into the outflow from a continuous chemostat culture of Streptococcus mutans and Lactobacillus acidophilus for four weeks. At the conclusion of the experiment bacterial growth was monitored by taking optical density readings of the growth medium in each vial and the outer surface of the dentine specimens were examined by scanning electron microscopy as shown by SEM analysis. RESULTS Ozone infusion prevented biofilm formation on all the treated samples while there was substantial biofilm present on the control specimens. While the average optical density of the control specimens was almost twice that of the ozone infused dentine (0.710 for the control with a SD of 0.288 and 0.446 for the ozonated samples with a SD of 0.371), the results were not significant (p > 0.05). CONCLUSIONS This preliminary study has shown that the infusion of ozone into non-carious dentine prevented biofilm formation in vitro from S. mutans and L. acidophilus over a four-week period. The possibility exists that ozone treatment may alter the surface wettability of dentine through reaction with organic constituents.

Effect of Stannous Fluoride Treatments on the Progression of Initial Lesions in Approximal Surfaces of Permanent Posterior Teeth

Home use of a SnF2 dentifrice in combination with the professional application of a 10% SnF2 solution markedly retarded the growth of initial lesions over a four-year period. Overall, the SnF2 dentifrice alone showed inhibitory properties, whereas the SnF2 solution alone had no discernible effect on lesion development.

Clinical evaluation of a modified silver fluoride application technique designed to facilitate lesion assessment in outreach programs

BackgroundAn advantage of using silver fluoride treatments for carious primary teeth in outreach programs especially where dental resources are limited is that the treatments can be carried out by dental auxiliaries. One limitation to date is that assessments of lesion status have been based on a tactile test where a sharp probe or explorer is drawn across the surface of a lesion to assess its hardness. This is a technique-sensitive step and has the potential for iatrogenic damage, especially when a lesion is deep. This study was undertaken to determine whether an alternative, non-invasive, visual assessment could be a reliable indicator of lesion status. The approach was based on the retention, or otherwise, of a black surface deliberately created at the time of initial treatment.MethodsA total of 88 lesions in the primary molars of 45 children, aged 5 to 10 years, were treated with a one-minute application of 40% silver fluoride. The surface of the lesions was then deliberately turned black by the application of 10% stannous fluoride as a reducing agent. All lesions were on an approximal or occlusal surface of a first or second primary molar. The presence or absence of a continuous black surface at 6 months and any changes in radiographic depth that had occurred in that period were determined from digitized photographs and bitewing radiographs.ResultsThe retention of an uninterrupted black surface was associated with minimal or no caries progression whereas lesions with an incomplete or lost black surface were 4.6 times more likely to have progressed. Use of the Datta and Satten Rank-Sum Test to account for any clustering effect showed that the difference was statistically significant (p < 0.0001). The sensitivity and specificity of the approach were 80% and 81% respectively.ConclusionThe retention of a continuous black surface after the application of silver fluoride followed by a reducing agent on carious lesions in primary molars can provide a useful visual indicator of lesion progression and so be relevant for use in dental outreach programs.

An In Vitro Investigation of the Penetrating Efficacy of BIS-GMA Resin Pit and Fissure Coatings

The frequency of complete penetration of two commercial BIS-GMA resin pit and fissure coating materials into wide and constricted fissures was assessed from photomicrographs. It was found that 334 of the 390 wide fissures examined were completely filled by the coating materials. However, in contrast, only 28 of the 650 constricted fissures examined were completely filled by these resins.