Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study.

Objectives: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO₂) laser that was designed for soft tissue surgery.

Methods: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO₂ irradiation conditions used were: wave length 10.6 μm; 1.2–2.6 J/cm² fluence per pulse; repetition rate 120–1000 Hz; 100–200 ms pulse duration; and cumulative fluences ranging from 14 to 2200 J/cm². Each window was irradiated with a 0.3 mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0 s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM).

Results: The pulp chamber temperature rise ranged from 0.5 to 19° C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40 J/cm², 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel.

Conclusions: These results indicate there are threshold conditions above which pulsed CO₂ laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.