Purpose: Ultra-short laser pulses (USLP) have the potential for materials processing with almost no collateral thermal or mechanical damage. Thus they are well suited for hard tissue preparation in dentistry. But since sharp focusing has to be applied to reach the high intensities required for plasma-mediated ablation, the small focal spot must be scanned over a larger area representing the cross section of a conventional dental drill. This paper investigates cavity shape and morphology for two different pulse lengths, as longer pulses would allow less expensive laser sources to be used in later industrial development of a medical device. Materials and Methods: 700 fs and 12 ps laser pulses were applied on human dentin with a pulse repetition rate of 35 kHz using a newly developed rotating scanner working in r/ϕ-coordinates. Cavity shape and morphology of different scanning patterns were evaluated using ESEM and 3D light microscopy. Results: Ablated surfaces show a high macro- and microscopic quality. The achieved microretentive patterns show promise of providing good bonding to composite resin filling materials. Conclusion: Even at high pulse repetition rates, laser pulses in the low picosecond regime are very well suited for hard tissue ablation. The absence of collateral damage makes them as applicable for dental hard tissue preparation as femtosecond pulses.
Keywords: scanning, ultra-short laser pulses, cavity preparation, conservative dentistry, tissue processing, preparation quality