SURFACE MELTING AND THERMAL ABLATION PATTERNS INDUCED IN ENAMEL AND CEMENTUM BY10.6-m TEA-CO2LASER RADIATION. II. THEORETICAL MODELS FOR RADIATION-ENAMEL INTERACTIONS

2fluence – and foremost, the periodic patterns reported for the first time in Part I of this study – a theoretical analysis of the physical interactions has been carried out. The exponential or Langmuir-type saturation of the RMS roughness vs. fluence relationship points to the competition between the laser pulse melting of the surface layer and a ‘relaxation’ by own internal dynamics with an energy barrier which opposes to the external action. The energy balance of the interactions between the laser pulse and enamel suggests large lossesfrom the incident energy in the plasma formation. Models are suggested for the ultrastructural changesproduced by the non-polarized laser pulses with Gaussian profile at 625 J/cm 2 fluence.Theoretical predictions for resonant periodic structures based on the electrodynamical mechanism of diffraction and interference of laser radiation in the melted surface enamel layer fit excellently to the ~11 m short length waves seen in the enamel with perpendicular prisms. The thermophysical description of the interaction between the laser pulse and the target evidences relationships between the resonant periodic structures, the pulse fluence threshold, the pulse duration and enamel’s constants like specific vaporization heat and thermal diffusivity.The present results introduce our theoretical analysis as a powerful approach and encourage further developments.