This PDF file contains the front matter associated with SPIE Proceedings Volume 11942, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Raman spectroscopy (RS) has emerged as a method of choice for label-free, nondestructive, objective, and rapid analysis of biological samples. RS has found profound applications in dental research with studies on early caries detection, carbonate and phosphate contents, mineralization and demineralization patterns and stresssignatures in teeth samples. Raman dental spectral features are usually affected by fluorescence, especially archaeological samples, and are prone to thermal damage when laser power is increased for superior signal-to-noise ratio. This affects the quality of Raman dental maps, limiting their utility. This also warrants the need for exhaustive spectral preprocessing. One way to refine signal quality is through enhanced collection efficiency. In this study, we explored if spectra-quality from dental samples can be improved by signal collection through water-immersion objectives, since informative Raman regions are not affected by water. Raman maps were obtained from tooth samples under air-immersion objectives (10X and 50X) and a water-immersion objective (63X) using 532 nm laser. Spectra acquired through the different objectives were compared. We observed that the water-immersion objective reduced fluorescence, decreased baseline, and prevented thermal heating/damage to the samples. Dental samples were not affected by prolonged immersion in water. The improved spectral quality allows lower acquisition-time for mapping experiments. Further, it also reduces the preprocessing required to obtain sufficient signal-to-noise quality. Thus, application of water-immersion objectives in Raman experiments has the potential to enhance spectral quality and experimental outcomes while keeping the samples preserved for further analyses.

We have developed a clinical probe capable of acquiring simultaneous, multispectral short wavelength infrared (SWIR) reflectance and occlusal transillumination images of lesions on tooth proximal and occlusal surfaces to reduce the potential of false positives and enhance diagnosis. The dual probe was 3D printed and the imaging system uses an InGaAs camera and broadband light sources at 1310 nm for occlusal transillumination and 1600 nm for cross- polarization reflectance measurements. In this study a mathematical model to estimate the penetration depth of “hidden” occlusal lesions from the SWIR images was developed. We compared the model’s estimated lesion depth on 18 extracted teeth with lesions against microCT measurements. Although the model estimated depth deviates from that measured in microCT at higher depths, there is a good linear correlation (R² = 0.93) between the estimated depth from SWIR images and the measured depth using microCT. SWIR occlusal transillumination images at 1300 nm also provide information about interproximal lesion penetration depth which can be directly viewed from the occlusal surface. SWIR occlusal transillumination and reflectance depth measurements on 49 natural interproximal lesions were compared with microCT measurements. There was significant correlation between the depths measured with SWIR occlusal transillumination (R² = 0.81) and reflectance (R² = 0.19) compared with the depths measured with microCT.

Secondary caries occurs when leakage in the interfaces between restorative materials and tooth structure allow fluid and bacterial acid infiltration. Thermal imaging coupled with dehydration can be used to measure this increase in fluid permeability for secondary lesions in teeth. Thermal imaging exploits the temperature change due to water evaporation during dehydration to measure the rate of water diffusion from porous lesion areas. Previous in vitro and in vivo thermal imaging studies on enamel and root surfaces have been promising for assessing natural lesion activity. In this study, the rates of dehydration for secondary lesions on extracted teeth were measured. The secondary lesions were also assessed by optical coherence tomography (OCT) and correlated with dehydration rates to determine lesion activity. Future studies with μCT will be used to further confirm lesion severity and structure.

Tooth whitening has grown as one of the most requested dental procedures as the public continuously demands whiter smiles for appearance enhancement. This demand resulted in many options of home-based products (toothpastes, films, gels) and in-office-based products based on concentrated bleaching agents (typically hydrogen peroxide and carbamide peroxide) to be applied under professional supervision. However, protocols involving bleaching agents may increase tooth demineralization, tooth-surface roughening/softening, as well as degradation of dental restorations. Violet illumination alone has been proposed as an alternative to reduce tooth sensitivity while keeping desired whitening effects. In this study, we assessed the effectiveness of whitening treatments using violet illumination (VI) alone or combined with 35% hydrogen peroxide (HP) gel, as well as cleaning teeth with and without mineral oil. This assessment was performed by calculating whiteness and yellowness indexes based on the color change for the experimental groups: control, VI alone (VI group), VI with 35% HP gel (VI + HP group), violet illumination without 35% HP gel and cleaned with mineral oil before washing (VI + HP + oil group). All procedures were performed in 16 bovine teeth (1) stored in 5% thymol solution immediately after extraction, (2) subsequently cleaned and (3) stained with instant coffee solution for 24 hours (except by the control group). Our results suggested that the VI + gel whitening treatment was able to completely restore the teeth whiteness while lowering its yellowness by 31.2% compared to the control group. The VI + oil treatment was 3.7 times more effective in increasing whiteness and decrease yellowness compared to VI treatment. The performance of whitening treatments could potentially be increased by cleaning the tooth surface with mineral oil. The VI + gel treatment should be recommended against coffee stains and potentially investigated for stain types in future research.

Dental shade determination and seamless integration of restorative work in the oral cavity are challenging and important tasks in the everyday clinical dental practice. The aim of this in-vitro study was to evaluate comparatively the capability of software-based color analysis of mobile phone photography, with the spectrophotometric and visual methods for dental shade determination. Visual shade determination of the incisal, middle, and cervical thirds parts of ten extracted human teeth was performed using the Vita Classical and Vita 3D Master stock shade guides. Shade determination of the thirds of each tooth was performed using the Vita Easyshade spectrophotometer. Subsequently, photographs of each tooth were captured using a mobile phone camera. Color charts were produced using an in-house image processing technique, and the tooth color captured by the mobile phone photography was matched to the shade guides. The results show that the camera-based method had better agreement with the spectrophotometric and visual methods when the Vita Classical shade guide was employed. Software-based color analysis of mobile phone photography should be further explored for its use as an affordable potential tool for increasing objectivity and accuracy in dental shade determination.

The aim of our study was 3D objectification of stereolithography prepared printed models. Patients during clinical treatment were scanned by an optical scanner. Data from scanner were transferred to the STL files and then stereolithographic models were prepared. Method of optical triangulation, photogrammetric methods and mathematical model analysis were used for measurements. The surface profile was also evaluated. After three years, the quality of STL models was smooth and homogeneous and it was directly connected with the type and structure of filaments. Clinical applications demonstrated also treatment options for patients with nausea, rare diseases, or with small space between upper and lower jaw.

Objectives: The cross-over in-situ study aimed to evaluate the effect of CO₂ laser (9.3μm) irradiation, in combination with an AmF/NaF/SnCl₂ rinse on prevention and control of Erosive Tooth Wear (ETW) in human enamel. Materials and Methods: Two different settings were tested with, 1) as ETW-prevention (starting from sound tooth surfaces) (Setting-1), and 2) as ETW-control (substrates presented at start an artificial erosive lesion) (Setting-2). Additionally, in in one subset samples were exposed to AmF/NaF/SnCl₂ solution (Phase I) while in the other no exposure to the Fluoridetin rinse occurred (Phase). 192 samples of human enamel (3x3x1mm) were randomly divided into 4 experimental groups: (C) without treatment (negative control); (F) AmF/NaF/SnCl₂ solution (positive control); (L) CO2 laser irradiation; (L+F) CO₂ laser+AmF/NaF/SnCl₂ solution. 12 volunteers wearing removable devices participated in the study, carrying 8 samples per device. The erosive challenges (4×5min/day) occurred ex-vivo. The surface loss over time was measured using an optical profilometer (n=12 per group). Setting-1 data were analyzed by one-way ANOVA and Setting-2 data by two-way repeated measures ANOVA, both with Tukey post-hoc tests (α=5%). Results: Setting-1: groups L (4.59 ±2.95μm) and L+F (1.58±1.24μm) showed significantly less surface loss in preventing ETW than groups C and F. Setting-2: in controlling the progression of ETW, L+F was the only group with no significant surface loss between initial erosive lesion (3.65 ±0.16μm) and after erosive challenge (4.99 ±1.17μm). Conclusions: CO₂ 9.3μm laser application prevented and controlled ETW progression in human enamel, with greater efficiency when combined with AmF/NaF/SnCl2 solution application.*

Dental fluorosis is an increasing problem in the U.S. due to excessive exposure to fluoride from the environment. Fluorosis causes hypomineralization of the enamel during tooth development and mild fluorosis is visible as faint white lines on the tooth surface while the most severe fluorosis can result in pitted surfaces. It is difficult to differentiate lesions due to fluorosis from those due to caries. Dental fluorosis appears with extremely high contrast at short wavelength infrared (SWIR) wavelengths of 1450 and 1960 nm coincident with higher water absorption. In this study reflectance measurements at 1450 and 1950 nm were used to monitor the dehydration dynamics of lesions due to fluorosis on extracted teeth. The dehydration dynamics were compared with the lesion structure that was measured with microCT. Sixteen extracted teeth with suspected fluorosis were imaged and microCT showed that the mean surface zone thickness was 118 ± 30 μm and the lesion depth was 284 ± 105 μm for the areas of fluorosis investigated. The dehydration dynamics of lesions due to fluorosis appeared most similar to those of arrested caries lesions. There was no significant correlation (P <0.05) of the intensity change and rate of the intensity change at 1450 or 1950 nm with either the lesion surface zone thickness or the lesion depth.

Previous studies have shown that optical coherence tomography (OCT) can be used to show the formation of a transparent surface zone on caries lesions indicative of remineralization. Studies have also shown that monitoring changes in the diffuse reflectivity of caries lesions during drying with air can be used to assess lesion activity and that the largest changes occur at SWIR wavelengths coincident with high water absorption at 1450 and 1950 nm. The purpose of this study was to determine when remineralization has occurred by monitoring changes in SWIR reflectance measurements and OCT images of simulated lesions over an extended time period during exposure to a remineralization solution. Eight bovine enamel surfaces each with two treatment windows were exposed to a pH cycling regimen to produce simulated lesions 50-100 μm deep. OCT at 1310 nm was used to image the samples at each time point. An extended range tungsten halogen lamp with a 1450 nm band pass filter and a broadband amplified spontaneous emission source centered near the peak of the water-absorption band at 1950 nm were used as light sources. An extended range InGaAs camera (1000–2340 nm) was used to acquire reflected light images as the samples were dried with air. After 32 days of exposure to the remineralization solution there were no further changes to the samples suggesting they had been completely arrested.

It has been well established that CO₂ laser irradiation can be used to transform the mineral phase of dental enamel to make it more resistant to acid dissolution. The purpose of this study was to investigate if carbon dioxide laser irradiation and topical fluoride can be used to treat incipient caries lesions to inhibit further progression, i.e. treat active lesion surfaces as opposed to sound surfaces prior to subjecting them to an acid challenge. Simulated active caries lesions were produced on twenty eight bovine enamel samples using a pH cycling model and those surfaces were irradiated by a 9.4 μm CO₂ laser and treated with topical fluoride. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, optical coherence tomography (OCT), and SWIR reflectance surface dehydration rate measurements at 1950 nm after exposure to a further acid challenge. There was a significant reduction (P < 0.05) of further lesion progression for lesion windows treated with CO₂ laser irradiation followed by the application of an acidulated phosphate fluoride gel compared to the untreated lesion windows on each sample. Treatment by laser irradiation alone was not effective. The degree of lesion inhibition was not as high as has been previously observed for laser irradiated sound enamel surfaces exposed to an acid challenge.