Hard tissue ablation with a spray-assisted mid-IR laser

Area of Science:

• Biomedical Engineering
• Laser Dentistry
• Materials Science

Background:

• Dental procedures often require precise removal of hard tissues like enamel.
• Laser ablation offers a minimally invasive alternative, but efficiency and safety are key considerations.
• Understanding ablation mechanisms is crucial for optimizing laser treatments.

Purpose of the Study:

• To investigate the dominant mechanisms of dental enamel ablation using an Er,Cr:YSGG laser with and without water spray.
• To compare the efficiency and surface characteristics of spray-assisted versus dry laser ablation.
• To determine the role of water spray in modifying ablation thresholds and material removal.

Main Methods:

• Human enamel samples were ablated using a free-running Er,Cr:YSGG laser at various radiant exposures.
• A comparison was made between ablation with distilled water spray and dry ablation.
• Ablation thresholds, transient acoustic waves, ablated volume, and surface morphology were analyzed.
• Optical coherence tomography (OCT) was used to measure ablation profile and depth.

Main Results:

• Spray-assisted ablation resulted in cleaner craters with less thermal damage compared to dry ablation.
• Despite a 60% higher ablation threshold due to water absorption, acoustic pressures were 6x higher with spray.
• Ablation volume was up to 2x larger with spray-assisted ablation.
• Dry ablation showed irregular surface modification, charring, and peripheral cracks.

Conclusions:

• The enhanced ablation performance with water spray is attributed to rapid water vaporization, recoil stress, interstitial water explosion, and potential liquid-jet formation.
• Spray-assisted laser ablation provides efficient material removal with reduced thermal damage.
• This method offers a potentially safe and effective modality for dental treatments.