Lasers in Dentistry Quiz

Lasers in Dentistry

• Lasers are light amplification by stimulated emission of radiation
• Population inversion is required for laser generation. This means a higher number of atoms/molecules need to be in higher energy levels than lower energy levels. Direct excitation doesn't achieve this, giving only ~50% excited atoms.
• Laser operation requires stimulated emission, and population inversion.

Laser Requirements

• Stimulated emission: A photon interacts with an excited atom, causing it to drop to a lower energy level and emit a new, identical photon (same wavelength)
• Population inversion: More atoms need to be in a higher energy level than a lower energy level. This is achieved in specific ways, as shown in the different types of lasers highlighted in the text.

Ruby Laser

• A three-energy-level solid-state laser, using synthetic ruby crystals
• Developed by Maiman in 1960
• Emits deep red light (694.3 nm)
• Uses a ruby crystal (Al2O3: Cr3+) as a laser medium
• Doped with chromium (Cr3+) ions in sapphire (Al2O3)
• Uses a flashtube as an energy source/pump to excite chromium ions
• High thermal properties of ruby

Laser Properties

• Monochromaticity: Photons have the same wavelength
• Directionality: Beam is parallel and not divergent
• Coherence: Photons propagate in phase
• Brightness: High intensity, compared to ordinary light sources

Other Solid-State Lasers

• Er:YAG lasers: Emit infrared light (2.940 µm), used in dentistry
• Erbium belongs to the rare-earth metal family
• Lasers based on rare-earth doped gain media are sometimes called lanthanide lasers
• Other solid-state lasers like Nd:YAG, Nd:YAG doubled, Argon ion, CO2, and Dye lasers; wavelength, and mode information given in Table in page 18.
• GaAlAs lasers emit mainly near-infrared photons at 980 nm.
• KTP lasers emit visible light at ~532nm

Gas Lasers

• Helium-Neon (He-Ne) lasers: Four-energy-level laser, with population inversion of Ne. Uses energy transfer from electrically excited He atoms. He:Ne ratio is typically 10:1. Emits a wavelength of 632.8 nm.
• Carbon Dioxide (CO2) lasers: Vibrational transitions in CO2 molecules produce laser emission (10.6 and 9.4 µm). Uses vibrational energy levels of CO2. He gas helps with pumping by efficient production of the first vibrational state of N2.

Human Teeth and their Chemical Composition

•  Water absorbs in the ultraviolet (UV) and infrared (IR regions)
•  Hydroxyapatite (a main component of dental tissues) absorbs strongly at ~10 µm in the IR region

Laser Applications

• Laser welding of detached eye retina
• Laser lithotripsy of calculi
• Selective bond breaking using lasers
• Laser capture microdissection (LCM)

Additional Information

• Wavelengths listed for various laser types
• Specific materials like hydroxyapatite & titanium
• Energy transfer processes for lasing
• Diagnostic techniques & safety considerations (e.g. MRI compared to CT
• Specific reaction types for certain applications (e.g., bond breaking)

Test your knowledge about lasers used in dentistry with this quiz. Learn about the principles of laser operation, the requirements for generating lasers, and the specifics of ruby lasers. Explore the physics behind these powerful tools and their applications in dental practices.