Intrapulpal Temperature Research Articles

Changes in Intrapulpal Temperature After Er:YAG Laser Irradiation

This study was performed to investigate the changes in temperature induced by an Er:YAG laser irradiation and to find the means to minimize potential thermal damage due to temperature rise after irradiation. Intrapulpal temperature rise was found to last after irradiation at times, although the addition of appropriate water spray during tooth ablation by Er:YAG laser produced efficient ablation with little thermal damage. To investigate intrapulpal temperature change, each extracted tooth specimen was embedded into a resin block and temperature-measuring probes were placed on the irradiated and the opposite pulpal walls. An Er:YAG laser irradiation was performed at 300 mJ/pulse and 20 Hz, with a water flow rate of 1.6 mL/min for 3 sec. Each lasing was followed by (1) no application of post-irradiation water spray, (2) post-irradiation water spray for 1 sec and (3) for 2 sec. No significant temperature change was found on the irradiated pulpal wall during Er:YAG laser, while there existed significant temperature rise on the irradiated pulpal wall after irradiation. However, the addition of water spray for 1 or 2 sec after irradiation significantly decreased intrapulpal temperature compared to no application of post-irradiation water spray. There were no significant differences between the 1- and 2-sec groups. It is suggested that the addition of water spray for 1 or more seconds after irradiation reduces post-irradiation temperature rise, possibly leading to thermal damage on the dental pulp tissue.

Effect of composite temperature on in vitro intrapulpal temperature rise

Objectives To measure in vitro intrapulpal temperature when placing and restoring with either room-temperature or pre-heated (54 and 60 °C) composite. Methods A K-type thermocouple was placed in the pulpal chamber of an extracted, human bifurcated upper premolar which had a Class V preparation (1 mm remaining dentin thickness) on the facial surface. Tooth roots were immersed in a thermostatically controlled water bath and perfused with water at 1.25 μl/min to simulate physiological circulation in the pulp chamber. The thermocouple was connected to an analog-to-digital converter. The preparation was filled using composite either at room-temperature, or pre-heated to 54 or 60 °C with a commercial compule heater (Calset™), using standard clinical procedures by one person while continuously monitoring intrapulpal temperature ( n = 5). Temperature rise over baseline values were determined at various stages during the restoration process: composite placement, contouring, prior to light-curing, and immediately after light-curing (20 s, Optilux 501). At each measurement interval, intrapulpal temperature values were compared using ANOVA and the Tukey–Kramer post hoc test ( α = 0.05). Results Significant differences were found in intrapulpal temperature when comparing pre-heated and room-temperature composite treatments with respect to baseline among the stages of the restorative process. However, the extent of this increase with heated composite was only 0.8 °C. A 5 °C intrapulpal temperature rise was seen for all groups during photopolymerization. Significance Use of pre-heated composite only mildly increased intrapulpal temperature values when compared to composite delivered at room-temperature in an in vitro test environment. The largest temperature change occurred with application of the curing light.

Effects of an In-office Bleaching System (ZOOM™) on Pulp Chamber Temperature In Vitro

Several new techniques and materials for in-office bleaching have been introduced recently. The aim of this in vitro study was to measure the temperature increase in the pulp chamber of extracted teeth produced by the Zoom! in-office bleaching system and to investigate the influence of this light in conjunction with the bleaching gel on pulp temperature rise. Ten extracted, caries-free, unrestored human maxillary central incisor teeth were used for the study. The root of each tooth was cut approximately 2-3 mm apical to the cementoenamel junction (CEJ), and the apical orifice of the root canal was enlarged. The remaining pulp tissue was removed and the empty pulp chamber was filled with a heat sink compound. A thin K-type thermocouple was inserted into the pulp chamber through the cut root area. The root surfaces of the teeth were partially submerged in a water bath during the testing procedure at 37 degrees C. A whitening gel containing 25% hydrogen peroxide was applied to the buccal surfaces of all ten teeth and exposed to a Zoom! activation light for twenty minutes for three times; this was designated as Group I. The same teeth were then exposed with the Zoom! light for the same time period without the application of the bleaching gel and designated as Group II. The intrapulpal temperature pre-treatment (baseline) and the temperature increase during treatment was measured for both treatment groups. There was a statistically significant difference between the two groups (p=0.003). Application of the Zoom! light in conjuction with the application of bleaching gel produced a greater temperature rise than did the light alone. The mean temperature rise for Group I (light and bleaching gel) was 1.11 degrees C (0.18 degrees C) and 1.01 degrees C (0.12 degrees C) for Group II (light alone) at the end of a five-minute exposure. The Zoom! light either used with or without bleaching gel showed no significant increase in the intrapulpal temperature of teeth when used for the recommended exposure time.

Increases in intrapulpal temperature during polymerization of composite resin

The polymerization of dental composite resins can generate increases in intrapulpal temperature that may damage the pulp. The development of new polymerization devices such as the argon laser makes the assessment of these temperatures important. This study compared increases in temperature generated by argon laser and halogen light when polymerizing a bonding system and a composite resin, and also sought to determine whether both types of polymerization lights generate temperature increases below the safe limit of 5.5 degrees C. Thermocouples linked to a temperature reading system were positioned in the pulp chamber of 10 extracted bovine incisors. Class V cavities were prepared, etched, and filled with a 1-bottle bonding system (Single Bond) and composite resin (Z-100). The test groups were as follows (n = 5 for all groups): halogen light for bonding system (HB); halogen light for composite resin (HC); argon laser for bonding system (LB), and argon laser for composite resin (LC). The polymerization parameters were halogen light operated at 600 mW/cm2 for 40 seconds, which served as control, and argon laser operated at 200 mW for 10 seconds. Data were analyzed by a 2-way (light versus material) analysis of variance (ANOVA) (alpha = .05). The average temperature increases were 2.35 degrees C (HB), 2.69 degrees C (HC), 1.25 degrees C (LB), and 1.5 degrees C (LC). Significant differences between halogen light and argon laser (P = .002), but not between composite and bonding system, were demonstrated. The argon laser produced significantly lower increases in pulpal temperature than the halogen light, independent of the thickness of the polymerized material.

Temperature Response in the Pulpal Chamber of Primary Human Teeth Exposed to Nd:YAG Laser Using a Picosecond Pulsed Regime

This study was conducted to analyze temperature variation in the pulpal chamber using the (Nd:YAG) picosecond-pulsed laser to promote ablation in enamel and dentin of primary teeth. Several previous studies reported the temperature rise in pulpal chamber during laser irradiation. Since there are no reports about pulp chamber temperature changes during irradiation with picosecond-pulsed laser, the purpose of our investigation is to quantify the intrapulpal temperature changes following picosecond-pulsed Nd:YAG laser irradiation of enamel and dentin of primary teeth. In this study, we used 10 intact primary exfoliated teeth: five molars and five incisors. We used a commercial neodymium:- yttrium-aluminum-garnet continuous-wave (CW)-pumped Q-switched and mode-locked Nd:YAG laser, with varying power levels (200, 300, and 350 mW) operating with 100-psec pulsed duration. Typical plots show differences between heating and cooling of enamel and dentin of anterior and posterior teeth. Whereas for enamel the time evolution curves are dependent on power used for the investigated range (200-350 mW), for dentin the differences are not so evident. Observing temperature enhancement for each power, we were able to analyze operational conditions where temperature changes do not exceed 5.5 degrees C. Power-time-temperature (PTT) diagrams for clinical operations were determined based on varying power level and exposition time. Through the heating-cooling cycle, we could extract conventional heating and cooling times for enamel and dentin. We have shown that the Nd:YAG picosecond-pulsed laser is a safe tool for ablation of primary teeth in a broad range of operational parameters.

External bleaching therapy with activation by heat, light or laser—A systematic review

Objective External bleaching procedures utilizing highly concentrated 30–35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures. Sources Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review. Data Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 °C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation. Conclusion Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.

Temperature rise during orthodontic bonding with various light-curing units--an in vitro study.

The purpose of this in vitro study was to investigate the temperature changes in the pulp chamber during bracket bonding using three different light sources. Bracket bonding was performed on one lower first premolar and one lower central incisor at two different distances (surface and 10 mm). The measurements were taken with a J-type thermocouple wire, placed in the pulp chamber and connected to a data logger. Analysis of variance revealed that pulp chamber temperature changes were influenced by the light source, the tooth type, and the distance from the tip of the light guide to the bracket surface. Halogen induced significantly higher intrapulpal temperature changes than light-emitting diode and Xenon Plasma Arc (PAC) (P = .000). The temperature increase was significantly higher when the light-guide tip was positioned at the surface of the teeth than at the 10-mm distance with all light-curing units (P = .000). All light-curing units produced higher intrapulpal temperature increase in the mandibular incisor than in the premolar. Power PAC produced significantly higher heat changes in the incisor than in the premolar. Orthodontic bonding with different light-curing units did not exceed the critical 5.5 degrees C value for pulpal health.

Chemical, Morphological and Thermal Effects of 10.6-.MU.m CO2 Laser on the Inhibition of Enamel Demineralization

Studies have shown that enamel can be modified by pulsed CO2 laser to form a more acid-resistant substrate. This study evaluated the effects of a 10.6-microm CO2 laser on enamel surface morphology and chemical composition as well as monitored intrapulpal temperature changes during irradiation. Human teeth were irradiated with fluences of 1.5-11.5 J/cm2, and pulpal thermal as well as chemical and morphological modifications on enamel were assessed. The teeth were submitted to a pH-cycling model, and the mineral loss was determined by means of cross-sectional microhardness. For all irradiated groups, intrapulpal temperature changes were below 3 degrees C. FT-Raman spectroscopy and scanning electron microscopy indicated that fluences as low as 6.0 J/cm2 were sufficient to induce chemical and morphological changes in enamel. Then, for fluences reaching or exceeding 10.0 J/cm2, laser-induced inhibitory effects on demineralization were observed. It was thus concluded that laser energy density in the range of 10.0 and 11.5 J/cm2 could be applied to dental enamel in order to produce chemical and morphological changes and reduce the acid reactivity of enamel without compromising the pulp vitality.

Surface and intra-pulpal temperature rises during tooth bleaching: an in vitro study

To measure the surface and intra-pulpal temperature increases in vitro on upper and lower anterior teeth during tooth whitening procedures. A thermocouple was used to measure the temperature increase on the surface of an extracted upper central incisor tooth. Intra-pulpal temperature readings were made on upper and lower central incisors, lateral incisors and canines. Four lamps recommended for tooth bleaching were tested; a plasma arc lamp, a xenon-halogen lamp, a standard halogen lamp and a diode laser lamp. Temperature measurements were made with and without the bleaching agent present on the labial tooth surface. The increase in surface temperature readings ranged from 0.44 degrees C (luma arch) to 86.3 degrees C (laser) with no bleaching gel present. Intra-pulpal temperature increases ranged from 0.30 degrees C to 15.96 degrees C. The presence of the bleaching gel reduced temperature increases seen at the tooth surface and within the pulp. The increase in the intrapulpal temperature with most bleaching lamps was below the critical threshold of a 5.50 degrees C increase thought to produce irreversible pulpal damage. The only lamp that produced an intrapulpal temperature increase above this threshold was the laser-based lamp and caution is advised when using this equipment.

Intra-pulpal temperature rises in power bleaching

Objective To measure the surface and intra-pulpal temperature increases in vitro on upper and lower anterior teeth during tooth whitening procedures. Method A thermocouple was used to measure the temperature increase on the surface of an extracted upper central incisor tooth. Intra-pulpal temperature readings were made on upper and lower central incisors, lateral incisors and canines. Four lamps recommended for tooth bleaching were tested; a plasma arc lamp, a xenon-halogen lamp, a standard halogen lamp and a diode laser lamp. Temperature measurements were made with and without the bleaching agent present on the labial tooth surface. Results The increase in surface temperature readings ranged from 0.44°C (luma arc) to 86.3°C (laser) with no bleaching gel present. Intra-pulpal temperature increases ranged from 0.30°C to 15.96°C. The presence of the bleaching gel reduced temperature increases seen at the tooth surface and within the pulp. Conclusions The increase in the intrapulpal temperature with most bleaching lamps was below the critical threshold of a 5.50°C increase thought to produce irreversible pulpal damage. The only lamp that produced an intrapulpal temperature increase above this threshold was the laser-based lamp and caution is advised when using this equipment.

Intrapulpal Temperature during Preparation with the Er:YAG Laser: Anin VitroStudy

This investigation evaluated the variation of the intrapulpal temperature when dentine was irradiated by the Er:YAG laser. The effect of preparation with the Er:YAG laser on the intrapulpal temperature is probably the biggest problem in using the laser for preparation of dental hard tissue. Seventy-two bovine incisors were studied that had the enamel and dentine of the buccal surface polished to a thickness of 2.0 mm. The teeth were divided into three groups, according to the repetition rate used (Group I = 2 Hz, Group II = 4 Hz, and Group III = 6 Hz), and irradiated, with or without water cooling, using 250, 300, and 350 mJ of energy per pulse. Thermocouples were introduced inside the pulp chamber through the palatine opening of the samples and fixed to the vestibular wall of the pulp chamber using a thermal paste. It was verified that there was a decrease of the intrapulpal temperature for all of the parameters in the Group I irradiated with water cooling and for the parameters of 350 mJ/4 Hz with water cooling. The other irradiations showed an increase of the intrapulpal temperature, varying from 0.03 degrees to 2.5 degrees C. We conclude that the use of the Er:YAG laser promoted acceptable temperature increases inside the pulp chamber. However, we do not recommend this procedure without water cooling because macroscopic observations of the dentine irradiated without water cooling showed dark lesions, suggesting carbonization of this tissue.

Laser Er:YAG et odontologie restauratrice

The capacity of Er:YAG laser (λ = 2,940 nm) both to eliminate carious tissues and to prepare cavities for adhesive restorations has been widely demonstrated. The marketed apparatus allow cavities preparation with a suitable clinical working time. All of them are equipped with an internal cooling system for air and water pulverisation at the impact point of the laser beam. This system limits intrapulpal temperature rise to less than the biologically acceptable threshold of 5°C. Histological studies showed that the pulpal response to the Er:YAG laser irradiation of dental hard tissues is minor, localised and reversible, equivalent to those consecutive to the use of high speed rotative instruments in the same refreshment conditions. When Er:YAG laser has been used on dentin, the microscopic examinations revealed the absence of smear layer and open dentinal tubules. The intertubular dentin is partially removed due to the larger water content in its composition. Conversely, Er:YAG laser is less effective on peritubular dentin; it does not enlarge the tubule orifices, providing a microcrater-like appearance of laser irradiated surfaces. Direct composite resin bonding to the Er:YAG laser irradiated dentin, without acid pre-treatment, has been suggested. In a recent publication, the authors demonstrate that acid pre-treatment of the irradiated dentin surface results in similar microscopic observations at dentin-composite resin interfaces when compared with dentin bur preparation. The adhesion values of the composite resin to the irradiated dentin with or without acid etching are comparable to those measured with conventional bonding (bur + acid). Conversely, composite restorations of laser Er:YAG cavity preparations show significantly less microleakage when orthophosphoric acid is applied before bonding. First clinical applications concerning the preparation of Er:YAG laser cavities did not show any side effects. The absence of pain, noise and vibrations are of value in comparison with conventional mechanical preparations.

Temperature Analysis during Bonding of Brackets Using LED or Halogen Light Base Units

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance.

Pulpal temperature rise during light‐activated bleaching

The purpose of this study was to measure intrapulpal temperature rise induced by two kinds of bleaching gels when the tooth was exposed to a variety of light-curing units and a diode laser in vitro. The root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth. Two bleaching agents containing heat-enhancing colorant was applied to the labial surface. Light-curing units used were a conventional halogen (40 s), a high-intensity halogen (30 s), a light-emitting diode unit (40 s), and a diode laser (15 s). The temperature rise was measured in the pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Ten specimens were used for each system and bleaching-agent combination. Differences between the starting temperature and highest temperature reading were taken and the calculated temperature changes were averaged to determine the mean value in temperature rise. Temperature rise values were compared using two-way analysis of variance (ANOVA) at a preset alpha of 0.05. Temperature rise varied significantly depending on curing unit and diode laser used. The diode laser induced significantly higher temperature increases than any other curing unit (11.7 degrees C). The light-emitting diode unit produced the lowest temperature changes (6.0 degrees C); however, there were no statistically significant differences among the curing units and there were no statistically significant differences between bleaching agents. Light activation of bleaching materials with diode laser caused higher temperature changes as compared to other curing units and the temperature rise detected was viewed as critical for pulpal health.

Precision ablation of dental enamel using a subpicosecond pulsed laser.

In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel.

Subpicosecond laser ablation of dental enamel

Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1–1.4)×1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2±0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 °C during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 °C. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques.

Intrapulpal temperature changes during root surface irradiation with an 809-nm GaAlAs laser.

The aim of this study was to explore, in vitro, whether the irradiation of human root surfaces with a diode laser might induce nonphysiologic intrapulpal temperature elevations and, therefore, jeopardize pulp vitality. The pulps were removed from human maxillary and mandibular incisors extracted for periodontal reasons. The root canals were enlarged to an apical size #60 file. The teeth were radiographed with standard dental films and a millimeter grid to determine root thickness. The thickness of dentin between the root surface and the pulp in the irradiation areas was 1, 2, and 3 mm. To determine intrapulpal temperature changes during laser irradiation, 0.5-mm K-type thermocouples were inserted. An 809 nm GaAlAs laser with a 400-micron optical fiber was used. The power output varied between 0.5 and 2.5 W in the continuous-wave mode (0 Hz). Irradiation was continued for up to 120 seconds. Temperature elevations between 0.5 and 32.0 degrees C were registered in an energy- and time-dependent manner. Dentin thickness had a significant effect on intrapulpal temperature changes (Mann Whitney U test, P <.05), with a thinner dentin layer resulting in higher temperature elevations. Diode-laser irradiation may jeopardize pulp vitality. It must be recommended to limit power output to 0.5 W and the time of irradiation to 10 seconds when lasing the root surfaces of lower incisors and first maxillary premolars. With other teeth, a power output of 1.0 W and an exposure time of 10 seconds must not be exceeded to ensure a safe clinical application.

Effect of light-enhanced bleaching on in vitro surface and intrapulpal temperature rise.

This study investigated the effect of the presence, absence, and aging of a heat-enhancing compound (colorant) added to bleaching gel on the temperature rise of the gel itself, as well as the temperature rise within the pulp chamber, when a tooth was exposed to a variety of light-curing units in vitro. An extracted human upper central incisor was fitted with thermocouples placed in the pulp chamber as well as on the facial tooth surface. A temperature-controlled simulated intrapulpal fluid flow was provided to the tooth, and bleaching agent (Opalesence XTRA, Ultradent) containing heat-enhancing colorant, aged colorant, or no colorant was applied to the facial surface. The tooth and light-curing unit were placed in a thermostatically controlled oven at 37 degrees C, and real-time gel and intrapulpal temperature values were recorded digitally. Light-curing units used were a plasma arc light (PAC) (PowerPac, ADT), a conventional quartz tungsten halogen source (QTH) (Optilux 501, Demetron/Kerr), the QTH light used in high-power (bleaching) mode, and an argon ion laser (AccuCure 3000, LaserMed). An exposure scenario simulating light-enhanced bleaching of 10 upper teeth was developed. Temperature rise over the pre-exposure, baseline value associated with the last light exposure in the bleaching sequence was calculated for each curing and bleaching combination. Five replications for each test condition were made. Temperature rise values were compared using analysis of variance (ANOVA) at a preset alpha of 0.05. When fresh colorant-containing bleach was used, the PAC light increased bleach temperature 39.3 degrees C above baseline. With no added colorant, temperature rise was 37.1 degrees C. The QTH light in bleach mode resulted in gel temperature 24.8 degrees C above baseline, whereas the temperature increase was only 11.5 degrees C when no colorant was used. Conventional QTH light use increased fresh bleach temperature by 17.7 degrees C, whereas an increase of only 11.1 degrees C was measured without colorant. The argon ion laser produced equivalent temperature rise regardless of the presence or freshness of the colorant, approximately 9.4 degrees C. Intrapulpal temperatures were all significantly lower than those recorded in the bleaching gel and ranged from 5 degrees to 8 degrees C. As a rule, the presence of fresh heat-enhancing colorant in the bleaching gel resulted in a significant intrapulpal temperature increase (approximately 1 degrees C) over that reached using other lights. The PAC and the QTH light used in bleach mode induced greater intrapulpal temperature rise than the laser. Freshness of bleaching agent incorporating light-activated, heat-enhancing colorant influences temperature rise of bleaching gel and also may increase intrapulpal temperature values. Use of intense lights does elevate bleach temperature and also results in increased intrapulpal temperature that may further impact on patient sensitivity and pulpal health resulting from this treatment.

Human teeth exposed to argon laser irradiation: determination of power-time-temperature working conditions.

This study was conducted to establish the operating parameters of the argon laser without thermal damage to the pulp tissue for clinical applications. Previous studies have mainly compared the temperature modifications of the pulp chamber in a very limited situation, where a complete view of the thermal history cannot be obtained nor even extrapolated to new applications. We used samples of molar and premolar tooth where a class V cavity was prepared and illuminated with an argon laser at different power levels, fixing the exposition area for all cases. Situations including open cavity and teeth restoration were analyzed. High-precision thermistors were placed in four different positions, one of which was inside the pulp chamber. The temperature evolution was monitored continuously by an interfaced computer during all laser exposure. Special attention was paid to the intrapulpal temperature variation because it is considered the most vulnerable thermal region. The temperature time evolution allowed the determination of the operating conditions (power-time-temperature variation) in which the use of the argon laser causes no pulpal damage. As a function of temperature variation, we divided the whole parameter space (power-time-temperature) into zones and the optimum zone of operation was determined. We created a diagram called power-time-temperature (PTT) where zones of temperature increased under laser irradiation allow the verification of which condition is safe for clinical laser application. The results have a broad use when this type of analysis is applicable.

Intrapulpar temperature during continuous CO2 laser irradiation in human molars: an in vitro study.

To establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2-10 W and exposure times of 0.5-25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and the applied power. A variance analysis produced the linear regression equation: T = 1.10 + (0.127)E where T is the temperature and E the energy. The results showed that, with a power of 4 W and maximum exposure time of 2:5 s (10 J) and a power density of 12,738.85 W cm-2, there will be no damaging reactions affecting the pulpal tissues.