# Biophotonics in Dentistry
## 4 Conclusions  
In this review paper, we comprehensively discussed the application of biophotonics in dentistry, especially elements such as photoelasticity, interferometry techniques, optical coherence tomography, laser and quantum dots. The development of photonics has been invaluable in many dentistry applications, including but not limited to diagnostics, biomechanical studies, treatment of oral cancers and caries and the development of dental prostheses. Photoelasticity is an optical technique that has been applied for many years in experimental stress analysis. Most transparent materials exhibit a temporary birefringence property when exposed to strain and loading due to changes in molecular orientation distribution. ESPI is a non-destructive optical technique and is capable of obtaining measurements of the surface with high sensitivity in a non-contact manner. Other uses of ESPI include the study of dentin compression in water, whereby the Young's modulus of root dentin under compression can be easily detected.  
Moire interferometry is an alternative optical method for strain analysis, with applications in many fields, including biomechanics, fracture mechanics and the study of composite materials. The high sensitivity associated with moire interferometry makes it a valuable technique for the real-time study of the biomechanics of dental structures. Optical coherence tomography (OCT) is a non-invasive, non-destructive, high-resolution, cross-sectional imaging technique widely used in various clinical applications, including ophthalmology, dentistry and gastroenterology.  
Laser refers to light amplification by stimulated emission of radiation; concentrated, focused and coherent monochromatic radiation is emitted in a single wavelength. When interacting with tissue, this radiation may be transmitted, absorbed, scattered or reflected, depending on the optical properties of the tissue and the wavelength of the laser. Various effects can be achieved, including photoablation, photochemical effect, fluorescence and vaporisation. Photoablation and vaporisation are used to remove tissue, fluorescence can be used to detect caries and the photochemical effect can be used to initiate chemical reactions, such as curing of composite resin.  
Quantum dots are semiconductor nanocrystals with unique optoelectronic properties; when stimulated and excited, they release energy via single photons. The potential applications for quantum dots in both medical and non-medical fields are considerable, including fluorescent labels for biomedical imaging and cancer research, photonic devices, sensor materials, quantum communication networks, greater efficiency in LEDs and solar cells, quantum computing, drug delivery and engineered tissues. Additionally, other dental  
Figure 15: Schematic of active thermography system. Adapted with permission from Ref. [161] 2022, AIP Publishing.  
applications of laser could be beneficial in oral surgery, prosthodontics, endodontics and orthodontics. For instance, applications in endodontics could include smile design, caries removal, cement curing and tooth etching, among others. For orthodontics, applications could include bracket curing, removal of residual cement, post orthodontics and exposure of impacted teeth. Finally, the best examples of prosthodontics applications are crown contouring and lengthening and sulcus deepening.  
This research received no external funding.  
Not applicable.  
The authors declare that they have no competing interests.