Understanding the response of dental enamel to mid-infrared radiation

Human dental enamel has a porous mesostructure at the nanometre to micrometer scales that affects its thermal and mechanical properties relevant to laser treatment. We exploit finite element models to investigate the response of this mesostructured enamel to mid infrared lasers (CO2 at 10.6 μm and Er:YAG at 2.94 μm). Our models might easily be adapted to investigate ablation of other brittle composite materials. The studies clarify the role of pore water in ablation, and lead to an understanding of the different responses of enamel to CO2 and Er:YAG lasers, even though enamel has very similar average properties at the two wavelengths. We are able to suggest effective operating parameters for dental laser ablation, which should aid the introduction of minimally-invasive laser dentistry. In particular, our results indicate that, if pulses of ≈ 10 μs are used, the CO2 laser can ablate dental enamel without melting, and with minimal damage to the pulp of the tooth. Our results also suggest that pulses with 0.1-1 μs duration can induce high stress transients which may cause unwanted cracking. PACS: 87.50.Hj; 42.62.Be; 44.30.+v; 02.60.-x; 02.70.Dh; 07.05.Tp Submitted to: Physics in medicine and biology