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 effec ts on underlying dental hard tissues of a high pulse rate carbon dioxide (C O2) laser that was designed for soft tissue surgery. Methods: Eighteen extracted human teeth were sectioned longitudinally, clea ned, and varnished, leaving nine exposed windows on each: six on the corona l surface (enamel) and three on the root surface (cementum, dentin). The CO 2 irradiation conditions used were: wavelength 10.6 mum; 1.2-2.6 J/cm(2) fl uence per pulse; repetition rate 120-1000 Hz; 100-200 ms pulse duration; an d cumulative fluences ranging from 14 to 2200 J/cm(2). Each window was irra diated with a 0.3 mm beam diameter atone of nine power settings for 0. 1, 0 .5, or 1.0 s. The pulp chamber temperature was measured with a microthermoc ouple. The irradiated teeth were evaluated by Polarized Light Microscopy (P LM) and Scanning Electron Microscopy (SEM). Results: The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM r evealed crystal fusion in both enamel and dentin at all cumulative fluences . At cumulative fluences of 40 J/cm(2), 200 pulses/second and higher, measu rable tissue loss was observed with PLM both in dentin and enamel. Conclusions: These results indicate there are threshold conditions above wh ich pulsed CO2 laser light used for soft tissue surgery may cause detriment al changes to underlying oral hard tissue and to the pulp. (C) 2001 Publish ed by Elsevier Science Ltd.