Epi-third and second harmonic generation microscopic imaging of abnormal enamel

Area of Science:

• Biomedical Optics
• Dental Research
• Materials Science

Background:

• Tooth enamel protects inner dental tissues and requires early diagnosis of anomalies for effective prevention and treatment.
• Detecting enamel defects is crucial for maintaining oral health and preventing further dental issues.

Purpose of the Study:

• To investigate the application of epi-harmonic generation microscopy for studying abnormal human tooth enamel.
• To identify contrast sources of Third Harmonic Generation (THG) and Second Harmonic Generation (SHG) in various enamel conditions.

Main Methods:

• Utilized a 1230 nm light source with an epi-collection scheme for imaging enamel.
• Achieved an imaging depth exceeding 300 micrometers.
• Compared THG and SHG signals from sound enamel with white spot lesions, cracks, and irradiated enamel.

Main Results:

• Identified THG contributions from interprismatic spaces, cracks, and material inhomogeneities within enamel prisms.
• Attributed SHG signals to strain-induced breakage of the 6/m point group symmetry in enamel.
• Demonstrated distinct contrasts between sound and abnormal enamel using THG and SHG imaging.

Conclusions:

• Infrared-laser-based epi-harmonic generation microscopy provides valuable 3D spatial resolution for differentiating abnormal enamel from sound enamel.
• This technique enables in vivo monitoring of morphological changes and strain status in hydroxyapatite crystals without sectioning or staining.
• The method shows potential as a non-invasive tool for early diagnosis and monitoring of dental enamel health.