Ultrashort pulsed laser (USPL) application in dentistry: basic investigations of ablation rates and thresholds on oral hard tissue and restorative materials

Abstract

Modern ultrashort pulse lasers with scanning systems provide a huge set of parameters affecting the suitability for dental applications. The present study investigates thresholds and ablation rates of oral hard tissues and restorative materials with a view towards a clinical application system. The functional system consists of a 10 W Nd:YVO4 laser emitting pulses with a duration of 8 ps at 1,064 nm. Measurements were performed on dentin, enamel, ceramic, composite, and mammoth ivory at a repetition rate of 500 kHz. By employing a scanning system, square-shaped cavities with an edge length of 1 mm were created. Ablation threshold and rate measurements were assessed by variation of the applied fluence. Examinations were carried out employing a scanning electron microscope and optical profilometer. Irradiation time was recorded by the scanner software in order to calculate the overall ablated volume per time. First high power ablation rate measurements were performed employing a laser source with up to 50 W. Threshold values in the range of 0.45 J/cm(2) (composite) to 1.54 J/cm(2) (enamel) were observed. Differences between any two materials are statistically significant (p < 0.05). Preparation speeds up to 37.53 mm(3)/min (composite) were achieved with the 10 W laser source and differed statistically significant for any two materials (p < 0.05) with the exception of dentin and mammoth ivory (p > 0.05). By employing the 50 W laser source, increased rates up to ∼50 mm(3)/min for dentin were obtained. The results indicate that modern USPL systems provide sufficient ablation rates to be seen as a promising technology for dental applications.

Effect of Different Surface Treatments on Porcelain‐Resin Bond Strength

“…A large number of parameters determine the suitability of modern UPLS's (with scanning systems) for dental applications. Nevertheless, the ablation rates afforded by these systems make them promising for dental applications . Pedrazzi et al evaluated the SBS of repairs in porcelain conditioned with a UPLS (760 mW and 900 mW) for 10 seconds or with 10% HF acid for 2 minutes.…”

“…Ultrashort-pulse laser systems are not suitable for direct clinical use; however, many studies have reported on the bond strength of dental tissues subjected to treatments using a UPLS. 26,[37][38][39] Lorenzo et al 26 reported stronger bonding of brackets to enamel treated with a UPLS rather than other laser systems. The ablation from UPLS's is induced by a plasma, which imparts less thermal damage than do the longer pulses of ER:YAG lasers.…”

Investigations of the damage mechanisms during ultrashort pulse laser ablation of dental tissue

“…A discussion about how the ablation rate can be scaled using ultrashort pulse lasers can be found in several publication [7][8][9]. Recently, Schelle et al demonstrated that the ablation rate scales linear with power up to 50 W at a repetition rate of 500 kHz, enabling removal rates of up to 50 mm³/min [10].…”

Wettability of dentin after Yb:KYW thin-disk femtosecond ablation

“…Some investigators have shown that dental hard tissue could be precisely ablated with a femtosecond-pulsed laser; with appropriate laser and scanning parameters, collateral damage involved could be minimal [15][16][17][18][19][20][21][22][23]. In previous reports, it has been indicated that femtosecond-pulsed laser use alters the surface roughness of dental hard tissues, depending on the parameters used [24,25].…”