George K. Stookey

Comparative Study to Quantify Demineralized Enamel in Deciduous and Permanent Teeth Using Laser– and Light–Induced Fluorescence Techniques

Caries is a disease that affects both deciduous and permanent dentitions. Caries progresses more rapidly in deciduous enamel than in permanent enamel. Therefore, new caries diagnostic methods need to be tested on the deciduous teeth as well. Quantitative laser–induced fluorescence (QLF I) as well as the quantitative light–induced fluorescence (QLF II) seem promising for the quantification of mineral loss from dental caries but have only been tested on the permanent dentition. The objective of this study was to determine and compare the ability of QLF I and QLF II to quantify mineral loss from carious lesions in both deciduous and permanent teeth. Thirty sound deciduous and 30 sound permanent teeth were cleaned and divided into three groups each containing 10 deciduous and 10 permanent teeth. Windows on the buccal or labial enamel surfaces were demineralized for 48, 72, or 96 h. Images of demineralized enamel were captured using QLF I and QLF II. The images were analyzed to determine the mean change in fluorescence radiance (ΔF, %). The teeth were then sectioned for assessment of lesion depth (µm) and integrated mineral loss (IML, vol% ×µm) using transverse microradiography (TMR), as the ‘gold standard’ for lesion analysis. The results indicated a good correlation for ΔF between QLF I and QLF II in both deciduous (r = 0.96) and permanent teeth (r = 0.98). There was a good correlation between ΔF and TMR (lesion depth and IML) in deciduous teeth (r = 0.76 and 0.84 with QLF I, r = 0.81 and 0.88 with QLF II). In permanent teeth, the correlation between ΔF and TMR (lesion depth and IML) was lower than in deciduous teeth (r = 0.07 and 0.53 with QLF I, r = 0.15 and 0.62 with QLF II). From these results it can be concluded that either QLF method is capable of quantifying mineral loss in early carious lesions in deciduous teeth. Moreover, under the conditions of this study, the use of either QLF method to quantify mineral loss in early carious lesions in deciduous teeth is slightly more accurate than in permanent teeth.

Dental Fluorosis: Variability among Different Inbred Mouse Strains

Concurrent with the decline in dental caries has been an increase in the prevalence of dental fluorosis, a side-effect of exposure to greater than optimal levels of fluoride during amelogenesis. The mechanisms that underlie the pathogenesis of dental fluorosis are not known. We hypothesize that genetic determinants influence an individual’s susceptibility or resistance to develop dental fluorosis. We tested this hypothesis using a mouse model system (continuous eruption of the incisors) where genotype, age, gender, food, housing, and drinking water fluoride level can be rigorously controlled. Examination of 12 inbred strains of mice showed differences in dental fluorosis susceptibility/resistance. The A/J mouse strain is highly susceptible, with a rapid onset and severe development of dental fluorosis compared with that in the other strains tested, whereas the 129P3/J mouse strain is least affected, with minimal dental fluorosis. These observations support the contribution of a genetic component in the pathogenesis of dental fluorosis.

In vitro Removal of Stain with Dentifrices

An in vitro model has been developed for the purpose of evaluating the cleaning ability of dentifrices. A stained film is slowly deposited on enamel sections and subsequently removed using a mechanical brushing procedure. Results from this test procedure compare favorably with the results of controlled, clinical cleaning studies.

An in vitro Comparison between Laser Fluorescence and Visual Examination for Detection of Demineralization in Occlusal Pits and Fissures

It has been demonstrated that when excited by laser light carious enamel appears dark compared to luminescent sound enamel. The aim of this study was to compare the sensitivity and specificity of visual exams (V), laser fluorescence (LF) and dye-enhanced LF (DELF) for detecting demineralization in occlusal pits and fissures. The actual presence of lesions was determined by subsequent confocal laser microscopy (CM), which was compared to histology (H). Independent clinical examiners visually graded three sites on occlusal surfaces of extracted, human premolars as sound or carious and also rated the color of each graded site as: 0 = same as surrounding enamel; 1 = white; 2 = light brown, or 3 = brown/dark brown. An argon laser was used to illuminate the teeth for LF and DELF; the images were captured with a CCD camera and then analyzed. DELF images were captured after the teeth had been exposed to 0.075% sodium fluorescein. Sections were then cut from each specimen and analyzed by CM and H for the presence or absence of caries. Results showed that DELF (0.72) was significantly more sensitive (p < 0.05) than LF (0.49) and V (0.03) for detecting caries, but there were no significant differences among the methods in specificity (V 1.00; LF 0.67; DELF 0.60). When color was used as an indication of caries in V (VC, sensitivity 0.47; specificity 0.70), V exams were not different from LF. The area under the ROC curve, using H as the gold standard and CM as the test, was 0.78. Results indicated that DELF was the best diagnostic tool and that VC and LF were equally effective as diagnostic methods, when color of fissures was included as an indication of demineralization in the visual exam.

Residual Caries Detection Using Visible Fluorescence

This study investigated the ability of a new fluorescence method to detect residual caries in vitro. Gross caries was removed from 40 teeth with D2 caries. Samples were excited with violet-blue light and viewed through a 530-nm high-pass filter. Residual caries (orange-red fluorescing dentin) was detected in all samples. Further tooth substance was removed from half of the samples until no residual caries was detectable using the new method. Half of the samples remained untreated. A blinded examiner checked all samples for residual caries using DIAGNOdent, a visual tactile examination, and Caries Detector® dye. Presence or absence of residual caries in each sample was determined using a fluorescent nucleic acid stain in conjunction with confocal microscopy. The new method, Visible Fluorescence, had the greatest sensitivity, specificity, percent correct score and predictive values of any of the methods tested. The new method had significantly higher percent correct score than any of the other methods and significantly higher specificity than visual tactile and Caries Detector. It was concluded that Visible Fluorescence is an improvement on the currently available aids for residual caries detection.

Evaluation of Biochemical Validation Measures in Determination of Smoking Status

This study was designed to evaluate the use of salivary cotinine, salivary thiocyanate, and expired-air carbon monoxide as biochemical validation measures for assessing the smoking status of adults. The participants were 20 known non-smokers plus 216 admitted smokers and 102 proclaimed quitters participating in a clinical trial of approaches to facilitate smoking cessation. Conventional analytical procedures were utilized. By use of data from known non-smokers and admitted smokers, the sensitivity and specificity of the validation measures were as follows: salivary cotinine, 99% and 100%; expired-air carbon monoxide, 96% and 100%; and salivary thiocyanate, 67% and 95%, respectively. The salivary cotinine and expired-air carbon monoxide tests confirmed smoking cessation for 55% and 74%, respectively, of the proclaimed quitters. The length of time since quitting was significantly related to the results observed with the latter measures. Consideration of these observations along with various practical factors suggests that expired-air carbon monoxide assays may be the validation measure of choice for most clinical trials.

The Relative Anticaries Effectiveness of Three Fluoride-Containing Dentifrices in Puerto Rico

The objective of this research was to evaluate the anticaries effectiveness of a low-dose (500 ppm F, low-NaF) sodium fluoride dentifrice, a high-dose (2,800 ppm F, high-NaF) sodium fluoride dentifrice and an experimental 0.454% stabilized stannous fluoride (1,100 ppm F) with sodium hexametaphosphate (SnF2-HMP) dentifrice, each relative to a standard 1,100 ppm F sodium fluoride positive control dentifrice. Subjects (n = 955, with ∼239 per group) with a mean age of 10.6 (∼9–12 years) were randomly assigned to one of four dentifrice treatments. Two calibrated examiners independently measured visual-tactile caries as DMFS that was supplemented with a radiographic examination at baseline, 12 months and 24 months for each subject. Generally similar results were independently observed by both examiners at the conclusion of the 2-year study period. Considering all subjects that attended at least 60% of the supervised brushing sessions, statistically significantly less caries was observed in the high-NaF group compared to the control group. Similarly, statistically significantly less caries was observed in the SnF2-HMP group as compared to the control group. Differences in caries increments between the low-NaF and control groups were not statistically significant. One of the examiners observed these same statistically significant differences after 1 year. In conclusion, the results of this clinical trial indicated that while no difference in caries increments was observed between the low-NaF and control groups, both the high-NaF and the SnF2-HMP groups experienced significantly fewer lesions than the control group.

The Validity and Repeatability of Three Light–Induced Fluorescence Systems: An in vitro Study

New optical systems are being developed that aim to determine the extent of demineralization in enamel. In our laboratory we have compared three such systems: a ring illuminator equipped with a laser, a beam splitter also equipped with a laser and an intra–oral camera equipped with a white–light arc lamp. The aim of the study was to compare the ability of the different optical systems to detect small enamel lesions with microradiographic analysis and to determine the repeatability of these systems. Forty human enamel specimens (3mm in diameter) were mounted in acrylic and polished. The specimens were kept moist throughout the study. Each specimen of the four groups was individually exposed to 14 ml of Carbopol demineralizing solution for 24, 48, 72 and 96 h, respectively. The mineral loss of the 40 specimens was assessed with blue–violet light– induced fluorescence. Each image was captured with a video camera and analysed with dedicated software. The measurements were repeated 3 times with complete shut–down of the system in between the measurements. The same measurements were performed with the ring illuminator, the beam splitter and the arc lamp. The specimens were then cut into thin sections and analysed with microradiography. Similar high correlations between microradiography and the light–based analysis systems were found for the beam splitter and the clinical caries camera set–up. The repeatability was best for the beam splitter set–up. This indicates that the light–induced fluorescence measurement technique can be used in different configurations and that the repeatability of the measurements is influenced by the physical stability of the set–up.

Laboratory Studies Concerning the Enamel and Dentin Abrasion Properties of Common Dentifrice Polishing Agents

In view of the meager amount of information available concerning commercially available dentifrices, a study was conducted to evaluate 43 dentifrices with regard to abrasion to enamel and dentin and enamel polishing ability. The results indicated a wide range of abrasiveness and polishing ability.

An in vitro Microbial Model for Studying Secondary Caries Formation

Secondary caries is a major reason for the replacement of restorations. Because it is hypothesized that the development of secondary caries is closely associated with pathogenic oral bacteria, an in vitro microbial model has been developed to produce secondary carious lesions. A mixture of overnight cultures of Streptococcus mutans and Lactobacillus casei in dextrose-free trypticase soy broth, supplemented with 5% sucrose (TSBS), at 37 degrees C was used in this model as the inoculum for the experimental groups. Uninoculated control groups were incubated with medium only. Groups of human tooth specimens restored using composite, together with their respective controls, were exposed for 7 or 12 days to circulating cycles of TSBS (30 min each, 3 times per day) and a mineral wash solution (for a total of 22.5 h per day), at 37 degrees C. The pH of the experimental groups dropped to 4.l-4.5 during the test periods. The pH of the control groups remained at 6.8-7.0. The inoculated bacteria remained viable throughout the study. No contamination of experimental or control samples occurred. Laser scanning confocal microscopy demonstrated the development of incipient surface and wall lesions in all the specimens of experimental groups in as few as 7 days. Reproducibility of the model was confirmed in a second investigation. Therefore, it was concluded that this model can be used for studying the microbial etiology and prevention of secondary caries.