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Author(s): Tressel, John T; Abdelaziz, Marwa; Fried, Daniel | Abstract: SignificanceIt is not sufficient to detect caries lesions on tooth surfaces; it is also necessary to measure the activity of the lesions to determine if intervention is needed. Changes in the reflectivity of lesion areas during dehydration with forced air at short wavelength infrared (SWIR) wavelengths can be used to assess lesion activity since these changes represent the evaporation dynamics of water from the lesion.AimThe aim of this study is to develop new optical methods for assessing lesion activity on tooth surfaces utilizing the strong water absorption band near 1950-nm.ApproachThe time-resolved reflectivity of 20 active and arrested caries lesions on the surfaces of human extracted teeth was monitored at 1300 to 2000nnm using broadband light sources and an extended range InGaAs camera during drying with air.ResultsMultiple parameters representing the rate of change of the lesion reflectivity correlated with the presence of a highly mineralized outer surface zone indicative of lesion arrest measured with x-ray microtomography (microCT). Performance at 1950-nm was higher than for other wavelengths.ConclusionsThis study demonstrates that SWIR imaging near 1950-nm has great potential for the assessment of lesion activity.

Significance: Dental caries is the most common oral disease, with significant effects on healthcare systems and quality of life. Developing diagnostic methods for early caries detection is key to reducing this burden and enabling non-invasive treatment as opposed to the drill-and-fill approach. Aim: The application of a thermophotonic-based 3D imaging modality [enhanced truncated-correlation photothermal coherence tomography (eTC-PCT)] to early dental caries is investigated. To this end, the detection threshold, sensitivity, and 3D lesion reconstruction capability of eTC-PCT in imaging artificially generated caries and surface erosion are evaluated. Approach: eTC-PCT employs a diode laser with pulsed excitation, a mid-IR camera, and an in-house developed image reconstruction algorithm to produce depth-resolved 2D images and 3D reconstructions. Starting with healthy teeth, dental caries and surface erosion are simulated in vitro through application of specific demineralizing/eroding acidic solutions. Results: eTC-PCT can detect artificial caries as early as 2 days after onset of artificial demineralization and after 45 s of surface erosion, with a laser power equivalent to 64% of maximum permissible exposure. In both cases, the lesion is not visible to the eye and undetected by x-rays. eTC-PCT is capable of monitoring lesion progression in 2-day increments and generating 3D tomographic reconstructions of the advancing lesion. Conclusions: eTC-PCT shows great potential for further development as a dental imaging modality combining low detection threshold, high sensitivity to lesion progression, 3D reconstruction capability, and lack of ionizing radiation. These features enable early diagnosis and frequent monitoring, making eTC-PCT a promising technology for facilitating preventive dentistry.

Statement of the Problem: After introducing digital radiography, practitioners started reading radiographs from computer monitors; however, many still prefer hard-copy radiographs. Purpose: This study aimed to assess the possible superiority of either type of radiograph recording media (computer monitor, film, or paper) in diagnosis and perception of the depth of the cariogenic lesions. Materials and Method: Twenty digital bitewing radiographs, obtained from 200 posterior extracted teeth, were displayed on an LG monitor and printed on paper and film using Kodak printers. Two observers independently measured lesions depth on the images. Serial sections of teeth were obtained and the sections were evaluated by a stereomicroscope to determine the actual depth of cariogenic lesions. The efficacy of the each medium was assessed by determining its specificity and sensitivity in comparison with those of histological images. Weighted kappa coefficients and the ROC analysis were used for the statistical analysis. Results: Strong intra- and inter-observer agreements (0.818 to 0.958, 0.77 to 0.85) were found for all detection methods. The highest Az value was obtained with the monitor-displayed images (Az: 0.879); however, differences between detection methods were not statistically significant (p> 0.05). Conclusion: Monitor-displayed bitewing radiographs, paper, and film prints used in our study performed similarly in the detection of proximal caries.

Sugar-rich diets and poor dental hygiene promote the formation of a biofilm (plaque) that strongly adheres to the dental enamel surface and fosters the evolution of aciduric bacteria. The acid contributes to demineralization of the exterior tooth enamel, which accelerates after the pH drops below a critical value (∼5.5) for extended time periods resulting in the need for restorative procedures. Preventative techniques to alert the dentist and caries-susceptible patients regarding vulnerability to dental decay require a clinical measure of plaque activity. Therefore, there is a need to evaluate the acid production capability of plaque deposits in the pits and fissures of occlusal and interproximal regions. A ratiometric fluorescence pH-sensing device has been developed using an FDA-approved dye and LED excitation. Fluorescein spectral profiles were collected using a spectrometer and analyzed with a spectral unmixing algorithm for calibration over the pH range of 4.5 to 7. An in vivo pilot study on human subjects was performed using a sucrose rinse to accelerate bacterial metabolism and to measure the time-dependent drop in pH. The optical system is relatively immune to confounding factors such as photobleaching, dye concentration, and variation in excitation intensity associated with earlier dye-based pH measurement techniques.

Aims To investigate the diagnostic quality of different quality, individually calibrated ink-jet printers for the very challenging dental radiographic task of approximal carious lesion detection. Materials and methods A test-pattern evaluating resolution, contrast and homogeneity of the ink-jet prints was developed. 50 standardized dental radiographs each showing two neighbouring teeth in natural contact were printed on glossy paper with calibrated, randomly selected ink-jet printers (Canon S520 and iP4500, Epson Stylus Photo R2400). Printing size equalled the viewing size on a 17″ cathode-ray-tube monitor daily quality-tested according to German regulations. The true caries status was determined from serial sectioning and microscopic evaluation. 16 experienced observers evaluated the radiographs on a five-point confidence scale on all prints plus the viewing monitor with respect to the visibility of a carious lesion. A non-parametric Receiver-Operating Characteristics (ROC-) analysis was performed explicitly designed for the evaluation of readings stemming from identical samples but different modality. Significant differences are expressed by a critical ratio z exceeding ±2. Diagnostic accuracy was determined by the area (Az) underneath the ROC-curves. Results Average Az-values ranged between 0.62 (S520 and R2400) and 0.64 (monitor, iP4500), with no significant difference between modalities (P = 0.172). Neither significant (range mean z: −0.40 (S520) and −0.11 (iP4500)) nor clinically relevant differences were found between printers and viewing monitor. Conclusions Our results for a challenging task in dental radiography indicate that calibrated, off-the-shelf ink-jet printers are able to reproduce (dental) radiographs at quality levels sufficient for radiographic diagnosis in a typical dental working environment.

A number of different designs of cells have been developed for the study of dissolution processes in packed apatite powders. Basic design requirements were that no deleterious processes, such as high temperature sintering or binding agents, were involved, and that there was maximum opportunity for experimental study. One design used alternating filter paper discs and apatite layers (typically 42 mg). At the end of an experiment, the cell could be disassembled and infrared spectra and X–ray powder diffraction patterns made of individual layers. Cells without filter paper discs were also made, but terminal sampling at well–defined depths was more difficult or impossible. The cells were constructed from poly(methylmethacrylate) so the course of dissolution could be monitored by radiography. Subsurface loss of apatite was almost always seen after from 2 weeks to 8 months exposure to buffer solutions at pH 3.0–5.5. The greatest loss of apatite was typically 0.4–2 mm below the surface, which is at a larger distance than usually seen for dental enamel. This may be attributable to the low packing density (typically 35–60 vol%) found in the present systems compared with enamel.

The aim of the present study was to evaluate the significance of diffusion barriers in the development of artificial caries-like lesions. A 30-mm2 enamel surface area was covered with a layer of filter paper and exposed to a gently agitated 50 mM acetate buffer, pH 4.5, containing either 0.1 or 1.0 ppm fluoride for up to 48 h at 20 degrees C. Similar enamel surfaces, but unprotected by filter paper, served as controls. It was found that below the filter paper an approximately 60-microns-deep caries-like lesion was developed exhibiting a preserved surface layer, the mineral content of which depended on the fluoride concentration of the buffer. The lesions of the control teeth without a filter paper coverage were erosion-like surface lesions. In the filter paper calcium and phosphate released from the enamel combined with fluoride from the bulk solution had established a supersaturation with respect to fluorapatite while the undersaturation with respect to hydroxyapatite was maintained, which caused a caries lesion to develop. The lesions produced in noncovered enamel by bulk solution unsaturated with respect to both apatites were erosion-like. It was concluded that a diffusion barrier can significantly favor the establishment of supersaturation with respect to fluorapatite and thus facilitate the development of a subsurface caries-like lesion at the expense of the erosion.

The British Association for the Study of Community Dentistry (BASCD) has coordinated National Health Service surveys of the dental health of school children since 1985, when Wales and parts of England were included. Scotland joined in 1987 and Northern Ireland in 1994. This series spans an interesting time in the growth of accessible technology in both statistics and medical research. The purpose of this paper is to chart the development of this data base from pen and paper via microcomputers to the Internet. The annual work now involves calibration of examiners, data collection with portable computers or by manual transcription and subsequent 'punching', paper reports passed to regional coordinators who fill in spread sheets that are passed by e-mail or through posted discs to the data coordinating centre at the Dental Health Services Research Unit at the University of Dundee. The data is checked; statistical analyses are undertaken; a paper is prepared for print and the data is deposited on the BASCD Web Site. Four operating systems and at least eight software packages are used to produce and distribute the survey results.