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The literature increasingly indicates that lasers will have a multitude of applications for dental hard
tissue procedures, e.g. preventive therapy, caries removal, laser etching and endodontic therapy.
However, it is critical that such laser therapies avoid the production of heat levels which will be
damaging to the surrounding vital tissues, such as the dental pulp and periodontal tissues. Our
preliminary research on temperature changes across C02 lased dentin indicated that for single
preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot) the mean temperature rise across
350 j.tm of dentin was 0.57 0C while across 1000 .tm of dentin the mean rise was only 0.18 °C. Further
research utilizing multiple preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot, 3 x
1.0 sec. intervals) showed mean temperature elevations of 1.56 0C across 350 m of dentin and 0.66 O
across 1000 xm of dentin. While these temperature elevations, which would be associated with
preventive therapy, are very low and would be biologically acceptable, it must be noted that exposures of
higher intensities are required to fuse enamel and porcelain, or remove decay. This current research
investigates temperature elevations which occuT during C02 lasing utilizing the following exposure
parameters: 8.0 W., 1.0 mm focal spot, 0.1 sec. exposures, 2 or 4 exposures per site pulsed 1.0 sec. apart.
Three dentin thicknesses were utilized, i.e. 1000 jim, 1500 p.tm and 2000 .tm. Four sections of each
thickness were utilized with four exposure sites per specimen (2 with 2 exposures, 2 with 4 exposures).
All dentin sections were prepared from non-carious third molars using a hard tissue microtome. A
thermistor was placed on the dentin surface opposite each lased site and temperature changes were
recorded for approximately 50 sec. following lasing. Mean temperature elevations ranged from a
high of 3.07 C for the 1000 xm section utilizing four exposures to a low of 0.37 0C for the 2000 m section
utilizing two exposures. Analysis of Variance (p < .0001) and Duncan's Multiple Range Test (p =.05)
indicated significant differences existed among the mean temperature elevations observed. While
significant differences in temperature elevation can be observed both by numbers of exposures and by
dentin thickness, it would appear that, under the conditions of this study, the temperature changes
across CO2 lased dentin are all relatively low. It should be reiterated that the lasing parameters used
in this study are far in excess of those necessary for preventive applications and are, in fact, in the
range of exposures which will fuse enamel and dental porcelain, or remove dental caries. The modest
temperature elevations observed, combined with the relatively severe exposure parameters utilized on
thin sections of dentin, demonstrate the effective protective barrier which dentin provides for the
dental pulp relative to heat damage from C02 lasing.
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