Relationship between Changes in Chemical Composition of Enamel Subsurface Lesions and the Emitted Nonlinear Optical Signals: An in vitro Study.

The development of new diagnostic technologies based on the light scattering and autofluorescence properties of dental tissues is required to improve the diagnostic ability of initial caries lesions earlier than previously done and promoting the potential of treatment without surgical intervention. The aim of this study is to correlate fluorescence-based results provided by multiphoton microscopy (MPM) with confocal Raman microscopy records using phosphate level at 960 cm-1 and the organic matrix at ∼2,931 cm-1 in healthy and demineralized human enamel. Measurements on 14 teeth were made using two incident lights of different wavelengths, released by confocal Raman microscopy and MPM. Raman phosphate peak intensity at 960 cm-1 along with organic to mineral ratio at (2,931/430 cm-1) and nonlinear optical signals (second harmonic generation [SHG] and intrinsic two-photon excited fluorescence [I2PEF]) were recorded from the demineralized and healthy enamel sites. Raman spectral maps showed that the higher the organic/mineral ratio in the demineralized enamel, the lower the intensity of mineral component in the same zone. MPM revealed new optical indicators of carious lesion as shown by the presence of a red-shifted fluorescence peak in the 650- to 750-nm area of the fluorescence spectrum of demineralized enamel. Moreover, on sample regions with insignificant autofluorescence, the emergence of the SHG signal could be noted. By comparing I2PEF images with the structural motifs observed by the confocal Raman imaging system, the morphological similarity of the acquired images was quite evident. Any change in the I2PEF spectra reflects alterations in the chemical composition of enamel. These findings may provide an important basis for potentially valuable applications of photonic tools in the clinical diagnosis of tooth pathological conditions, besides exposing the fundamental role of organic matrix in enamel integrity and reparation.

Effect of Preventive Dental Products on Bonding Force: An in vitro Study.

Aim: Testing the effect of Fluoride, chlorhexidine, and molecular iodine applications on the mean micro-shear bond strength (SBS) of enamel in an attempt to preserve enamel integrity during the bonding process. Materials and Methods: The study was an observational case-control one in which 150 human teeth were classified into 10 groups according to the product kind and the prescribed treatment. Each group consisted of 15 teeth. Group C was the control group. Groups FP, FV, and OS utilized products that could be utilized in a professional dental setting. Group FP was treated with 1.23% NaF prophy paste, Group FV was treated with 5% NaF varnish, and Group OS was treated with Opal® Seal Fluoride releasing primer and sealant. Groups L, LF, CHX, and I were treated with mouth rinses. Group L was treated with Listerine Zero Fluoride-Free Mouthwash, Group LF with Listerine Zero 0.02% NaF Mouth Rinse, Group CHX with 0.12% chlorhexidine gluconate, and Group I with ioRinse RTU 100 ppm molecular iodine rinse. Groups TP and G utilized alternative remineralization products. Group TP was treated with Fluoro Calcium Phosphosilicate bioglass containing toothpaste, and Group G was treated with Curodont Protect remineralizing tooth gel. One-way ANOVA test was utilized to perform all statistical analysis in this study. Results: For mean micro-SBS, no significant difference (P > 0.05) between any of the experimental groups was observed when compared to the control group. There was a significant difference (P < 0.05) between Opal Seal versus Listerine Total, Opal Seal versus Peridex, Listerine versus Listerine Total, and Listerine versus Peridex. All other experimental group comparisons revealed a nonsignificant difference (P > 0.05). Conclusions: As the null hypothesis (H0) assumes that changes observed in an experiment are due to chance, hence, the outcomes of this study are coherent with (H0) since the aforementioned application methods did not significantly impact the SBS of orthodontic resin cement to enamel.

Formation and assessment of enamel subsurface lesions in vitro.

The present study compared two pH-cycling models designed to induce subsurface lesions (SLs) with a less demineralized surface layer on teeth, with the aim of developing new technologies for assessment of such lesions by examining the performance of confocal Raman microscopy for detection of white spot lesions (WSLs). Twelve sound premolars were exposed to two sets of model conditions (A, B) designed to induce SLs. Teeth on which white lesions had formed in vivo were used as positive controls. All specimens were inspected using an intraoral camera and Raman microscopy to detect small changes in the appearance and structure of the enamel. Changes in the natural color of the teeth during the treatment were recorded via the camera. Phosphate maps with their spectra were constructed from the phosphate peak at 960 cm-1. The depth of lesions was measured on the basis of variations in phosphate peak intensity. Protocol B was reliable for reproducing SLs in a relatively short period. Both protocols had intrinsic limitations in not completely simulating the complex intraoral conditions leading to WSL formation with respect to lesion depth and preservation of an intact surface layer. Raman microscopy can be considered the gold standard for analysis of hard tissue mineralization.