In vitro assessment of temperature change in the pulp chamber during cavity preparation

Statement of problem. Tooth preparation with a high-speed handpiece may cause thermal harm to the dental pulp. Purpose. This in vitro study evaluated the temperature changes in the pulp chamber during 4 different tooth preparation techniques and the effects of 3 different levels of water cooling. Material and methods. The tip of a thermocouple was positioned in the center of the pulp chamber of 120 extracted human premolar teeth. Four different tooth preparation techniques were compared: (1) Low air pressure plus low load (LA/LL), (2) low air pressure plus high load (LA/HL), (3) high air pressure plus low load (HA/LL), and (4) high air pressure plus high load (HA/HL) in combination with 3 different water cooling rates. Control specimens were not water cooled; low water cooling consisted of 15 mL/min, and high water cooling consisted of 40 mL/min. Twelve different groups were established (n = 10). An increase of 5.5degreesC was regarded as critical value for pulpal health. The results were analyzed with a 3-factor ANOVA and Bonferroni adjusted Mann Whitney U test (alpha = .004). Results. For all techniques without water cooling (LA/LL/0, LA/HL/0, HA/LL/0, and HA/HL/0), the average temperature rise within the pulpal chamber exceeded 5.5degreesC during cavity preparation (7.1degreesC; 8.9degreesC; 11.4degreesC, and 19.7degreesC, respectively). When low water cooling was used with high air pressure and high load technique (HA/HL/15), the average temperature rise exceeded 5.5degreesC limit (5.9degreesC). However, when high water cooling (LA/LL/40, LA/HL/40, HA/LL/40, and HA/HL/40) was utilized, the critical 5.5degreesC value was not reached with any air pressure or load (3.1degreesC, 2.8degreesC, 2.2degreesC, and -1.8degreesC, respectively). Conclusion. Within the limitations of this in vitro study, the results indicate that reducing the amount of water cooling or increasing air pressure and load during cavity preparation increased the temperature of the pulp chamber in extracted teeth.