The clinical application of surface pH measurements to longitudinally assess white spot enamel lesions
Introduction
Conventionally dental caries has been treated by removing the carious hard tissues and the placement of a restorative material. Recently, a new approach has been adopted called the Minimal Intervention concept which aims to treat lesions in a non-invasive manner where possible.1 Non-cavitated white spot enamel lesions (WSEL) can be arrested or reversed if the cariogenic challenge is sufficiently controlled or therapeutic agents are applied to promote enamel remineralization.2 One such agent is MI Paste that contains casein phosphopeptide-stabilized amorphous calcium phosphate (CPP-ACP) that has been shown in clinical trials to promote the regression of early lesions.2, 3, 4, 5 Means of objectively assessing WSEL are critical for determining their potential activity and monitoring the success of preventive treatments.
Current methods for assessing the activity of WSEL include visual criteria,6, 7 and lactic acid sensitive alginate impression materials.8 Simple objective chair-side techniques for assisting with lesion activity assessment would be an invaluable aid for dental care providers for the management of early carious lesions. Historically, the pH of a range of intraoral fluids have been measured such as saliva9 and plaque.10 However, few of these pH measurement techniques have become routinely adopted in clinical practice.
One problem with measuring plaque is that often patients will remove it immediately prior to appointments by thorough brushing. This study sought to use an Ion Sensitive Field Effect Transistor (ISFET) pH probe11, 12, 13, 14 to measure the surface pH of WSEL and the sound enamel surrounding it with the prior removal of the overlying plaque. This pH probe has been used previously to examine the pH of arrested and active dentine caries in vitro and validated against a pH imaging microscope.14 To the authors knowledge this is the first time that a pH sensor has been used to measure surface pH as a means of monitoring WSEL. Therefore, the aim of this study was to assess longitudinally the pH of WSEL and the sound enamel surrounding it following the institution of a preventive program to determine whether differences existed and whether they would correlate to any observed changes in lesion appearance.
Section snippets
Study design and subject recruitment
Eight healthy subjects were recruited after ethical approval was obtained from the Ethics Committee of the Tokyo Medical and Dental University and informed consent forms were signed. Each volunteer completed a medical history, and was examined to assess their caries experience. For inclusion in the study subjects were required to have at least one WSEL. Exclusion criteria included smoking, evidence of poor oral health including periodontal disease, recent professional fluoride therapy (<2
Results
The sound enamel pH values were not statistically different in the same subject at the various time points and between subjects. The mean pH of all sound enamel measurements was 6.83 (95% CI 6.82–6.84, n = 135). The pH of the WSEL was significantly different from the surrounding sound enamel at all time points (p < 0.001). The differences with treatment time are shown in Table 1. At the initial visit the mean pH of the WSEL (5.94 ± 0.17) was significantly lower than at all the later time points once
Discussion
Dental caries is a result of pH fluctuations within a biofilm on the dental hard tissues and hence considerable research has been conducted on the pH of saliva and plaque fluid. Lesion fluid, being more difficult to measure, has not been studied as extensively. Additionally, the surface pH of WSEL and the sound enamel surrounding it has not been examined. Previous studies have demonstrated that intraoral pH fluctuates through the day due to consumption of fermentable carbohydrates or acidic
Acknowledgments
This project was supported by Grant #21592413 from the Japan Society for the Promotion of Science, and for Global Center of Excellence Program for International Research Center for Molecular Science in Tooth and Bone Diseases at Tokyo Medical and Dental University. Dr. Glenn Walker and Mr. Masaomi Ikeda are acknowledged for assistance with statistical analysis.
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