Effects of nanosecond‑ and microsecond‑pulse Er, Cr: YSGG laser on the morphology and pulp temperature of dentin in dental restoration debonding

Objective: This study evaluated dentin morphology and pulp cavity temperature changes during nanosecond‑ and microsecond‑pulse Er, Cr: YSGG laser debonding restoration and residual adhesive.

Materials and methods: Ten caries-free teeth had their enamel removed perpendicular to the long axis, followed by bonding of glass ceramic restorations. The samples were randomly divided into two groups and subjected to Er, Cr: YSGG laser (3 mJ, 100 Hz, 100 ns), (3 mJ, 100 Hz, 150 µs) for debonding of restoration and residual adhesive on dentin surfaces. Thermocouples and scanning electron microscopy were used to monitor pulp cavity temperature and dentin surface morphology during debonding.

Results: Both nanosecond- and microsecond-pulse lasers effectively debonding restorations, leaving residual adhesive on dentin surfaces that required further treatment. The temperature change of pulp cavity with nanosecond pulses laser was 1.8 ℃ and 2.8 ℃ during debonding of restoration and residual adhesive, and with microsecond pulses were also 3.4 ℃ and 5.8 ℃, respectively. The dentinal tubules in the nanosecond pulses laser group were completely opening, while those in the microsecond pulses laser group were partially opening.

Conclusions: Nanosecond pulses of Er, Cr: YSGG laser are preferable over microsecond pulses for debonding restoration and residual adhesive on dentin surfaces. Nanosecond pulses induce smaller temperature changes in the pulp cavity and more pronounced opening of dentinal tubules, facilitating subsequent bonding processes.