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

A Study of the Peculiarities of the Formation of a Hybrid Interface Based on Polydopamine between Dental Tissues and Dental Composites, Using IR and Raman Microspectroscopy, at the Submicron Level

The creation of buffer (hybrid) layers that provide improved adhesion to two heterogeneous materials is a promising and high-priority research area in the field of dental materials science. In our work, using FTIR and Raman microspectroscopy at the submicron level in a system of dental composites/intact dental enamel, we assessed the molecular features of formation and chemically visualized the hybrid interface formed on the basis of a nature-like adhesive, polydopamine (PDA). It is shown that a homogeneous bioinspired PDA-hybrid interface with an increased content of O-Ca-O bonds can be created using traditional methods of dental tissue pretreatment (diamond micro drilling, acid etching), as well as the subsequent alkalinization procedure and the developed synthesis technology. The development of the proposed technology for accelerated deposition of PDA-hybrid layers, as well as the creation of self-assembled biomimetic nanocomposites with antibacterial properties, may in the future find clinical application for minimally invasive dental restoration procedures.

Organic volume and permeability variations in the surface layer of artificial and natural enamel carious lesions

OBJECTIVES

Test the hypothesis the type of enamel caries (natural, artificial induced by gel, and artificial induced by acid solutions) affect the organic volume and the permeability of the surface layer in enamel caries lesions.

DESIGN

Artificial enamel caries, induced by either acidic solution (organic-poor; Group 1) or acidic gel (organic-rich; Group 2), and natural non-cavitated inactive approximal enamel caries lesions (NEC; Group 3) were obtained, from which longitudinal ground sections were prepared. Measurements of the mineral (V_min) (by microradiography), and water (α) and organic (β) volumes (by optical birefringence) were obtained at three points in the surface layer (n = 30/group).

RESULTS

The main outcomes were the ratio between experimental β by predicted β (β Ratio) and the ratio between experimental and predicted permeabilities (α_d Ratio). β Ratio in Group 1 was lower than in Groups 2 (Cohen's d: -1.81; 95% CI:-1.45,-2.32; p < 0.001) and 3 (Cohen's d: -0.71; 95% CI:-0.27,-1.18; p = 0.004), and Group 2 surpassed Group 3 (Cohen's d: 0.49; 95% CI:0.07,0.94; p = 0.03). α_d Ratio in Group 1 was higher than in Groups 2 (Cohen's d: 1.86; 95% CI:1.49,2.33; p < 0.001) and 3 (Cohen's d: 0.60; 95% CI:0.18,1.14; p = 0.01), and Group 3 surpassed Group 2 (Cohen's d: 0.61; 95% CI:0.23,1.07; p = 0.01).

CONCLUSIONS

The highest organic volume and the lowest permeability occurred at the surface layer of gel-induced artificial enamel caries lesions, which should be preferred in in vitro studies on de- and remineralization and resin infiltration.

Dental Age Estimation Using Multiphoton Microscopy: A Potential Tool for Forensic Science

Normal aging affects the different structures of teeth, in particular, the dentine. These changes are useful in forensic disciplines as a tool for age estimation. Although multiphoton (MP) microscopy has been used to explore dental pieces, a relationship between age and MP response of the human dentine has not been proposed yet. The relationship between MP signals and natural dentine aging is investigated herein. An index of age (INAG) combining two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) images has been used to quantify these changes. The results show that the INAG significantly decreases with age. Moreover, peritubular dentine size and collagen internal properties are also modified with age. This information confirms the usefulness of this technique in forensic age estimation after disasters (natural or manmade) with a lack of comprehensive fingerprint database. Courts and other government authorities might also benefit from this tool when the official age of individuals under special circumstances is required for legal or medical reasons.

Development of a Visualisation Approach for Analysing Incipient and Clinically Unrecorded Enamel Fissure Caries Using Laser-Induced Contrast Imaging, MicroRaman Spectroscopy and Biomimetic Composites: A Pilot Study

This pilot study presents a practical approach to detecting and visualising the initial forms of caries that are not clinically registered. The use of a laser-induced contrast visualisation (LICV) technique was shown to provide detection of the originating caries based on the separation of emissions from sound tissue, areas with destroyed tissue and regions of bacterial invasion. Adding microRaman spectroscopy to the measuring system enables reliable detection of the transformation of the organic–mineral component in the dental tissue and the spread of bacterial microflora in the affected region. Further laboratory and clinical studies of the comprehensive use of LICV and microRaman spectroscopy enable data extension on the application of this approach for accurate determination of the boundaries in the changed dental tissue as a result of initial caries. The obtained data has the potential to develop an effective preventive medical diagnostic approach and as a result, further personalised medical treatment can be specified.

Chemical and morphological changes of femtosecond laser-irradiated enamel using subablative parameters

Chemical composition of dental enamel has a great relationship with the prevention of caries. The objective of the present work was to evaluate the chemical and morphological changes of femtosecond laser-irradiated enamel with subablative parameters using Raman spectroscopy, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Bovine incisor teeth were used to obtain 30 enamel specimens (5 × 5 mm² ). The chemical composition of the control sample was analyzed by Raman spectrometry to acquire the absorption spectrum, delimiting the areas under the carbonate and phosphate bands. This analysis was used to evaluate the change in the chemical composition of the sample after irradiation. The specimens were irradiated (IRR) with a Ti:Sapphire laser system (pulsed and focused modes, femtosecond regime 70 fs, average power of 1 W and exposure time of 15 s). After irradiation, the areas under the carbonate and phosphate absorption bands were delimited in each specimen. Raman spectrometry data were analyzed using Student's t-test (α = 5%). By comparing the spectra of the IRR and non-irradiated (NI) specimens, the results showed a significant increase in the area value for the phosphate peaks and a significant reduction in the area value for the carbonate peak and the carbonate:phosphate ratio. CLSM and SEM analyses did not reveal structural alterations in the subsurface nor morphological alterations in the IRR enamel surface, respectively. It was concluded that femtosecond laser irradiation using subablative parameters reduced the carbonate content and the carbonate/phosphate ratio without altering the structure and morphology of the dental enamel.