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Electrical Measurements for Use in Caries Clinical Trials

¹ Dental School and Dental Health Services Research Unit, Dental School, University of Dundee, Park Place, Dundee, DD1 4HR, Scotland, UK; and
² Dept of Dentistry, University of Groningen, A. Deuslinglaan 1, NL 9713 AV Groningen, The Netherlands;

^* corresponding author, c.longbottom{at}dundee.ac.uk

	ABSTRACT

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
This paper reviews the use of electrical measurements of caries, particularly in relation to caries clinical trials. Electrical measurements change as tooth tissue porosity alters in the caries process, but several other variables also have a significant effect on these electrical measurements and hence upon their diagnostic validity. Available electrical-method data, in the context of clinical trials, relate to the use of the Electronic Caries Monitor (ECM), which measures "bulk" resistance. The device is presently limited in scope to occlusal surfaces, and only limited ECM data from clinical trials are available. In the context of clinical trials, more work is needed to determine the potential role of electrical measurements. Such research will need to focus both on an understanding of those electrical parameters which are most valuable in identifying changes and stages in the caries process in individual teeth and also on identifying the extent of the effects of the variables affecting these measurements.

KEY WORDS: caries • electrical measurement • caries clinical trials

	INTRODUCTION

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
This paper considers electrical methods of caries detection in relation to caries clinical trials. Specifically, it seeks to consider the question: How effective are electrical measurements in caries detection in a caries clinical trial context?

	OUTLINE OF PAPER

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
To ascertain the effectiveness of a measuring technique, one must first determine and describe how the technique works in the chosen application. This leads to a detailed examination of what the technique actually measures and what factors may or may not influence these measurements. There is more than one way to make electrical measurements, so the different measurement options are reviewed.

In terms of the particular application—caries clinical trials (CCTs)—the fundamental question being asked is, "Can a technique be used to measure caries to determine anti-caries effects?" Hence, what is the accuracy of the technique in measuring what it purports to measure—caries?

Factors affecting the process of data analysis also need to be considered. Only then can examination and analysis of the available data from the use of electrical measurements in CCTs thus far reported be used to help to determine whether the results can allow conclusions to be drawn about the applicability and effectiveness of the technique in CCTs. The paper will conclude by summarizing the above review and suggesting recommendations regarding electrical measurements in caries clinical trials.

	HOW DO ELECTRICAL MEASUREMENTS OF DENTAL CARIES WORK?

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
Put in a fairly simple yet reasonably accurate form, as a tooth demineralizes in the caries process, the loss of mineral leads to increased porosity in the tooth structure. This porosity is filled with fluid from the oral environment which contains many ions. Increased ionic content in the pores leads to increased electrical conductivity, or, conversely, increased porosity leads to decreased electrical resistance or impedance.

	WHAT DO ELECTRICAL MEASUREMENTS ACTUALLY MEASURE?

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
The ECM device, which uses a single fixed-frequency alternating current, attempts to measure the "bulk resistance" of tooth tissue—i.e., it attempts to locate the resistance of teeth to current as close to zero frequency as feasible. This would be the "true" value of the electrical resistance of the tooth, were there no polarizing effects caused by direct-current application. The inherent electrical properties of materials, including tooth tissues, include resistance, capacitance, and inductance. Fortunately, inductance is not an issue with unrestored teeth, so resistance and capacitance are the main parameters of interest. For several decades, Electrical Impedance Spectroscopy (EIS) has been the conventional means of determining the electrical properties of materials. Its principal advantage over single (fixed)-frequency measurements is that, since materials have different electrical responses at different frequencies, EIS can help to determine more accurately the various parameters which demonstrate these differences. However, it is only in the last decade or so that EIS has been applied to teeth.

	FACTORS AFFECTING ELECTRICAL MEASUREMENTS

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
Whether the technique uses a single frequency or EIS, the factors affecting measurement will be the same. There are at least 6 factors which can have a significant impact on electrical measurements of teeth: the porosity of the tissues, the surface area of the electrical contact, the thickness of the tissues, the extent of hydration of the tissues, and the temperature and the concentration of the ions in the fluid within the tooth. To understand what electrical measurements mean in the context of CCTs, one must examine each of these factors to determine their extent and significance.

Porosity
Porosity is a somewhat ambiguous term and, in the context of the electrical measurement of teeth, could mean three slightly different things:

1. Do electrical measurements measure pore volume? If so, is it total pore volume?
   
2. Do electrical measurements measure pore depth? If so, what is the effect of mineral "layering" of natural caries lesions on these measurements? or
   
3. Is the tortuosity of the pores—i.e., the three-dimensional complexity of the lesion pores—a principal determinant of the electrical conductivity in relation to ionic conductance?
   

In relation to porosity, it is well-recognized that teeth undergo a maturation process after eruption; this process has a significant effect on porosity and hence electrical properties. There are variations in the process between and among individuals, as demonstrated recently by Schulte et al.(1999) and by Wang et al.(2001), and there is a period of up to 15–18 months after eruption in which the electrical impedance characteristics of particular teeth can vary. This is of particular relevance to CCTs involving adolescents, in whom several teeth are relatively recently erupted, notably the second permanent molars.

Surface Area
The surface area of the electrode contact with the tooth is a significant factor in electrical measurements. The two modes of "site- (or point-)specific" and "surface-specific" electrodes produce different values for electrical properties, and slight but evident differences in the validation studies reported in the literature for the two techniques tend to confirm this effect.

The Thickness of the Tissues
Thickness of the tissues, especially in relation to the variation of enamel fissure thickness, will affect electrical measurements, and differences between tooth types have been demonstrated previously. More recently, analysis of data from Wang et al.(2000) suggests that within-tooth site differences can affect electrical measurements.

Hydration of the Enamel
Hydration of the enamel will affect electrical measurements. The commercially available ECM device, for example, is designed to operate with a specific air-flow, but care must be taken that the teeth are not previously dehydrated prior to measurement. The use of a contact medium of toothpaste or gel minimizes this effect to a certain extent, but again care has to be taken to standardize, as much as possible, any drying prior to the contact medium application.

Temperature
Huysmans et al.(2000) recently demonstrated that the temperature of the teeth affects the electrical values obtained, though the fact that this effect was linear simplifies in vitro to in vivo extrapolations of absolute values of parameters.

The Concentrations of Ions in the Dental Tissue Fluids
The concentrations of ions in the dental tissue fluids, particularly within enamel, are critical to electrical measurement values, yet little is known about the possible extent of the effect of variations of this on measurements in vivo. For example, will a recently consumed sugary snack initiate sufficient demineralizing activity in the surface layer and body of a lesion to alter the ionic inter-prismatic fluid concentration, hence electrical measurement values, obtained during the time of the initial pH drop in the Stephan curve?

	SINGLE- OR MULTIPLE-FREQUENCY MEASUREMENTS

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
The fixed-frequency (23 Hz) measurements obtained by ECM are limited to occlusal sites, and the device attempts to measure the "bulk resistance" of teeth. It is designed to be operated in a "site-specific" mode, but if the airflow is turned off and a contact medium, such as toothpaste, is applied, a "surface-specific" measurement can be carried out. EIS (Electrical Impedance Spectroscopy) scans a range of electrical frequencies and provides information on impedance and capacitance, among other parameters. The development of an Equivalent Circuit for the tissue being measured is a way of describing the electrical behavior of that tissue in terms of resistors, capacitors, and constant-phase elements. Enamel and dentin are relatively "simple" materials, and Equivalent Circuits for teeth have been developed. Caries makes these circuits somewhat more complex, but these are being investigated. The process provides the potential for more detailed information to be obtained about the physical structure of the tooth being measured—hence the determination of its caries status—than the use of a single-frequency measurement.

EIS has been applied to approximal sites in vitro, and it has the potential for application to occlusal and free smooth-surface sites in vivo, with the use of suitable contact probes.

One prototype EIS device has been developed—the ACIST device—but this is not yet commercially available. The use of a prototype—the pre-ACIST device—was investigated on a subset of subjects in a recent clinical trial, but details are not yet available, since they are still subject to commercial confidentiality. The results will be presented in due course.

	VALIDITY

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The validity of electrical caries detection methods was the subject of a critical review by Huysmans (2000) and papers by Ashley et al.(2000) and Wang et al.(2000). Huysmans pointed out that ECM measurements provide quantitative data, and thus it was best to use a correlation with a gold standard of lesion progression. Almost all the published data relate to ECM data; correlations range from 0.47 to 0.82.

In terms of traditional caries thresholds used in CCTs, there are sensitivity and specificity data for D1 (enamel) caries and D3 (dentinal) caries for both site-specific and surface-specific ECM methods. For site-specific D1 measurements, the sensitivity (Se) figures from different studies range between 0.70 and 0.92, with specificity (Sp) values of 0.78 to 1.00. The equivalent figures for surface-specific measurements are 0.61 to 0.65 (Se) and 0.73 to 0.86 (Sp).

For dentinal caries, the equivalent figures for these ranges are 0.39 to 0.97 (Se) and 0.56 to 0.98 (Sp) for site-specific measurements and 0.68 to 0.78 (Se) and 0.76 to 0.90 (Sp) for surface-specific measurements.

	HOW DO THESE FIGURES RELATE TO CCTS?

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The range of sensitivity and specificity values for the ECM is such that the confidence interval for absolute Diagnostic Value (which depends on caries prevalence) may be considerable and, if incorporated into the data analysis, may be too large to permit significant differences in product effects to be shown.

Subjects in different CCTs may have relatively different caries prevalence and/or incidence rates at occlusal, approximal, and/or free smooth-surface sites. Thus, the usefulness of ECM measurements—which apply to occlusal sites only—for a CCT may vary according to the relative occlusal to approximal to free smooth-surface caries ratios for prevalence and/or incidence in the subjects in a particular CCT site.

Thus, ECM may be useful in determining product differences in CCTs in areas with incidence rates of occlusal caries that are high relative to approximal caries, but be less useful for CCT in an area with a relatively higher approximal to occlusal caries incidence ratio. There is, of course, a less than simple relationship between total (and/or site) caries prevalence and incidence, since this depends on such factors as the age of the subjects at the time of data collection and population levels of caries.

	FACTORS AFFECTING MEASUREMENTS IN RELATION TO DATA ANALYSIS

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
Porosity
Porosity is of importance in relation to maturation, fluorosis, and hypomineralization. If teeth are measured by the ECM within 18 mos of eruption, the data are confounded by the maturation effect. Simply treating these types of data as equivalent to measurements on mature teeth will lead to skew, especially if mean values are used for caries increments. Similarly, the data from subjects with fluorosis, of whatever degree, which will increase porosity and reduce resistance values, should not be treated as the same as that from non-fluorosed subjects. Randomizing may eliminate this effect within a trial, but comparisons between trials may be affected if there are significantly different levels of even mild fluorosis between the datasets. Similar concerns apply to hypomineralized teeth.

Ten Bosch et al.(2000) confirmed the time-dependent decrease in the porosity of newly erupted teeth but also noted an unexpected seasonal variation in the ECM measurements on recently erupted teeth. The seasonal variations in these measurements were statistically significant, hence should be taken into account in any analysis of data collected over several months in a clinical trial environment.

Surface Area
In relation to surface area, different tooth types have different surface areas of contact. This relates particularly to "surface-specific" electrical measurements. Thus, different threshold values for electrical measurements may need to be applied to molars and premolars, respectively.

Thicknesses of Enamel
Different tooth types have different thicknesses of enamel, and such differences can occur even within tooth types; thus, ECM site measurements may need different threshold values for different sites for premolars and molars or even for occlusal and palatal/buccal sites in the same molar.

Hydration
Different hydration states of the measured teeth may occur if the measurement sequence involves holding each subject’s mouth open for sufficient time for dehydration to affect the electrical measurements. This latter critical period is in reality only a matter of seconds. Thus, skewed distributions of electrical measurement data in relation to left-right side and/or upper-lower jaws may require the application of "compensatory" statistics, or modification of the measurement protocol.

Temperature
The effects of temperature appear unlikely to require statistical intervention, since mouth temperatures are likely to stay within a small range for even a large number of subjects, though extremes of climate may have a minor effect on electrical measurements.

Fluid Ionic Concentration
Although enamel fluid ionic concentration may seem, at first thought, to have minor significance, the extent to which the time at which electrical measurements are taken in relation to school breaks and hence eating patterns does not appear to have been investigated. It is difficult, in any event, to see how this could be compensated for statistically.

	LONGITUDINAL CARIES STUDIES

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The first study to carry out longitudinal electrical measurements of the same teeth was conducted by White et al.(1981) using the now-unavailable Vanguard device. In total, 769 tooth sites, in the posterior teeth of a pediatric clinic sample, were measured at 6, 12, and 18 mos from baseline. The authors concluded that results showed that the instrument was a better predictor of the "clinically evident anatomical lesions" than was the dental explorer. The relevance of these results to today’s CCT environment, with generally lower caries prevalence/incidence and the move away from the use of the explorer, is difficult to assess.

Ie et al.(1995) and Fennis-Ie et al.(1998) reported on the use of the ECM in a longitudinal study of the first and second molars of 50 children aged 5–7 and 11–15 yrs. Comparisons were made with clinical-visual and FOTI techniques, and the teeth were monitored on six occasions at six-monthly intervals—a total of 2.5 yrs. Although the differences were reported to be very small, the authors concluded that ECM measurements were superior to FOTI and clinical-visual assessments for the prediction of occlusal caries.

	CARIES CLINICAL TRIALS

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The available published data on electrical measurements in CCTs are limited. Ashley (1997) and Ashley et al.(2000) reported on a study in Northwest England, and recently initial results have been presented by Matuliene et al.(2001), Bedinskaite et al.(2001), and Chesters et al.(2001) in relation to a study carried out in Vilnius, Lithuania. As-yet-unpublished data from these and other studies may appear in the public domain in the near future. In relation to root caries, Baysan et al.(2001) reported on a six-month clinical trial carried out in a dental school.

In the Ashley study, surface-specific electrical measurements were recorded every 6 mos during the second 18-month period of a three-year clinical trial comparing two products whose relative anti-caries effects were unknown. The second molars in 316 subjects aged 13.9 yrs at the ECM-baseline were measured and caries status for electrical measurements designated according to D1 and D3 cut-off values previously determined by laboratory studies.

The findings of this CCT were that, over the 18-month period, ECM measurements demonstrated a significant difference in the mean DFS increment between the test and the control groups at the p < 0.05 level. In contrast, the conventional detection methods used in the trial were unable to discriminate between the products over 3 yrs.

In the Vilnius study, which used two products with different effects of known extent, as shown previously by conventional detection methods, site-specific ECM measurements were recorded on all posterior teeth in 2387 subjects (aged 11–14 yrs) at baseline and 12 mos, using pre-determined D1 and D3 threshold points. For analysis, the ECM data were log-transformed. No product differences were found with the ECM, but they were found with a new Clinical Visual system—the Dundee Selectable Threshold Method (DSTM)—on approximal but not occlusal surfaces.

In addition, ECM readings were found to be highly significantly tooth-dependent, with higher readings the more posterior the tooth type. ECM readings were highly significantly jaw-dependent, with mandibular teeth generally scoring higher than maxillary teeth, except for first premolars. There was also a strong relationship between the ECM scores and the Clinical Visual Assessment (CVA) scores.

With the results of only two studies published for coronal caries available for review, the results are tantalizing: The Ashley study shows a possible but not conclusive ability of ECM to discriminate between products, but it was not conclusive, since the relative anti-caries effects of the two products were not known. This study also shows the inherent scientific invalidity of using an insensitive technique (CV) as the "gold" standard for demonstrating product effects when these are compared with new detection systems.

The Vilnius study shows the need for extreme care in data analysis when electrical measurements are used. As noted above, there are many factors which can affect ECM readings. This study also illustrates the possible effect of relative occlusal to approximal caries prevalence and/or incidence ratios in the subjects on the ability of ECM to demonstrate a product effect. The prevalence of occlusal caries in Vilnius was very high. This may have reduced the relative occlusal to approximal caries incidence to a level at which, in the time-scale of the measurement points, the product effects could not be demonstrated at occlusal sites compared with approximal sites.

The only reported longitudinal study involving electrical measurements of root caries involved 186 subjects examined at baseline, 3 mos, and 6 mos. All subjects had at least one primary root caries lesion at baseline, and these lesions were assessed clinically and with the ECM. The subjects were randomly assigned to one of two groups, one using a 5000-ppm-fluoride-containing dentifrice, and the other a 1100-ppm-fluoride-containing dentifrice. After 6 mos, 57% of the subjects in the 5000-ppm-F^– group and 27% of those in the 1100-ppm-F^– group had lesions which had hardened clinically (p = 0.002). Between baseline and 6 mos, the log₁₀ mean ± SD resistance values of lesions for subjects in the 1100-ppm-F^– group decreased by 0.004 ± 0.70, whereas in the 5000-ppm-F^– group, they increased by 0.56 ± 0.76 (p < 0.0001). The authors noted that the plaque index in the 5000-ppm-F^– group was significantly reduced compared with the 1100-ppm-F^– group. This latter difference may be a confounding factor in relation to interpreting the results, since plaque removal per se can alter the activity, hence the hardness, of root caries lesions.

	SUMMARY

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 

• An understanding of what electrical measurements actually measure and the various factors which affect them is essential to understanding their possible value in recording caries in CCTs.
  
• Maturation status, tooth type, tooth site, jaw and hydration status all have an impact on electrical measurements and should be taken into account when CCT data are analyzed.
  
• Fixed-frequency measurements have some limitations in the amount of information they provide on tooth structure and, hence, on caries status.
  
• ECM measurements have higher sensitivity but lower specificity than Clinical Visual methods and are currently limited to occlusal sites; the latter could pose problems in relation to interpreting and comparing CCT results in which subjects have differing relative occlusal:approximal caries prevalence and/or incidence ratios.
  
• The limited published data from CCTs of ECM measurements have produced "mixed" and "tantalizing" results.
  
• Electrical measurements may yet be extended to approximal and free smooth-surface sites.
  
• EIS measurements may provide more information for use in CCTs than fixed-frequency measurements, but data for these types of measurements have not yet been published.
  
• More ECM data from recent CCTs are likely to be published in the near future and will thus help further elucidation of the possible role of electrical measurements in CCTs.
  

	RECOMMENDATIONS

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 

• Detailed and careful analysis of current and emerging raw ECM (and other electrical) measurement data from CCTs should be carried out to understand the extent of the various factors influencing readings. (Data recording these factors should be gathered for each subject in the trials by researchers carrying out CCTs). This analysis should facilitate the application of appropriate statistical techniques to ensure accurate interpretation of CCT electrical data.
  
• More CCTs using electrical measurements are required before a definitive conclusion can be reached on the extent of the applicability and usefulness of electrical measurements in CCTs.
  

In conclusion, electrical measurements are showing early promise as a technique for the clinical detection of caries in the context of caries clinical trials. Careful analysis of current and emerging CCT data will help to determine the extent of the usefulness of the application of the method in this field.

	FOOTNOTES

 
Presented at the International Consensus Workshop on Caries Clinical Trials, Glasgow, Scotland, January 7–10, 2002

	REFERENCES

TOP ABSTRACT INTRODUCTION OUTLINE OF PAPER HOW DO ELECTRICAL MEASUREMENTS... WHAT DO ELECTRICAL MEASUREMENTS... FACTORS AFFECTING ELECTRICAL... SINGLE- OR MULTIPLE-FREQUENCY... VALIDITY HOW DO THESE FIGURES... FACTORS AFFECTING MEASUREMENTS... LONGITUDINAL CARIES STUDIES CARIES CLINICAL TRIALS SUMMARY RECOMMENDATIONS REFERENCES

 
Ashley PF (1997). The use of electrical impedance measurements for the diagnosis of posterior occlusal caries in clinical trials (PhD thesis). Manchester, UK: University of Manchester.

Ashley PF, Ellwood RP, Worthington HV, Davies RM (2000). Predicting occlusal caries using the Electronic Caries Monitor. Caries Res 34:201–203.[ISI][Medline]

Baysan A, Lynch E, Elwood R, Davies R, Petersson L, Borsboom P (2001). Reversal of primary root caries using dentifrices containing 5,000 and 1,100 ppm fluoride. Caries Res 35:41–46.[ISI][Medline]

Bedinskaite R, Sabatalaite R, Gendvilyte A, Huntington E, Matuliene G, Balciuniene I, et al. (2001). Comparison of DIAGNOdent and ECM techniques with radiography for the assessment of caries (abstract). Caries Res 35:279–280.

Chesters RK, Huntington E, Kvedariene A, Matuliene G, Balciuniene I, Nicholson JA, et al. (2001). Clinical visual assessment and the second permanent molar: a sensitive method for assessing anticaries efficacy (abstract). Caries Res 35:278.

Fennis-Ie YL, Verdonschot EH, van’t Hof MA (1998). Performance of some diagnostic systems in the prediction of occlusal caries in permanent molars in 6- and 11-year-old children. J Dent 26:403–408.[ISI][Medline]

Huysmans MCDNJM (2000). Electrical measurements for early caries detection. In: Early detection of dental caries II. Proceedings of the 4th Annual Indiana Conference. Stookey GK, editor. Indianapolis: Indiana University School of Dentistry, pp. 123–142.

Huysmans MCDNJM, Christie AM, Longbottom C, Bruce PG, Shellis RP (2000). Temperature dependence of the electrical resistance of sound and carious teeth. J Dent Res 79:1464–1468.[Abstract/Free Full Text]

Ie YL, Verdonschot EH, Schaeken MJM, van’t Hof MA (1995). Electrical conductance of fissure enamel in recently erupted molar teeth as related to caries status. Caries Res 29:94–99.[ISI][Medline]

Matuliene G, Gendvilyte A, Sabatalaite R, Huntington E, Pitts NB, Balciuniene I, et al. (2001). Discriminatory power of DIAGNOdent and Electrical Caries Monitor for assessing anti-caries activity of dentifrices (abstract). Caries Res 35:279.

Schulte A, Gente M, Pieper K (1999). Posteruptive changes of electrical resistance values in fissure enamel of premolars. Caries Res 33:242–247.[ISI][Medline]

Ten Bosch JJ, Fennis-Ie Y, Verdonschot EH (2000). Time-dependent decrease and seasonal variation of the porosity of recently erupted sound dental enamel in vivo. J Dent Res 79:1556–1559.[Abstract/Free Full Text]

Wang J, Sakuma S, Yoshihara A, Kobayashi S, Miyazaki H (2000). An evaluation and comparison of visual inspection, Electrical Caries Monitor and Caries Detector Dye methods in detecting early occlusal caries in vitro study. J Dent Hlth 50:223–230.

Wang J, Sakuma S, Yoshihara A, Miyazaki H (2001). Investigation of enamel maturation in post-eruptive molars by electrical caries monitor. Poster presentation at 4th Asia Academic Preventive Dentistry, Sept 20–23, Beijing.

White GE, Tsamtsouris A, Williams DL (1981). A longitudinal study of electronic detection of occlusal caries. J Pedodont 5:91–101.

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