Elsevier

Journal of Dentistry

Volume 30, Issues 7–8, September–November 2002, Pages 291-296
Journal of Dentistry

Pulpal space pressure and temperature changes from Nd:YAG laser irradiation of dentin☆

https://doi.org/10.1016/S0300-5712(02)00023-4Get rights and content

Abstract

Objectives. To investigate pulpal space pressure and temperature after application of Nd:YAG laser, and high-speed diamond bur on dentin surface.

Methods. One and 3 W Nd:YAG laser and high-speed diamond bur were used to remove dentine from twenty extracted premolars. The pulp chambers were monitored for pressure and temperature changes with a pressure transducer and thermocouple, respectively.

Results. Regardless of the remaining dentin thickness (RDT), laser irradiation and high-speed diamond bur use generated an increase in pulpal space pressure and temperature (ANOVA and Fisher's LSD tests, P<0.001). Pressure and temperature increased with an increase in laser power. Three-Watt laser irradiation caused greater changes than 1 W (1.75 kPa and 1.31 °C, 0.53 kPa and 0.34 °C, respectively). Both pulpal space pressure (P<0.001) and temperature (P<0.005) increased as the RDT decreased.

Conclusions. Laser irradiation and the use of a high-speed diamond bur generated an increase in pulpal space pressure and temperature. Pulpal space pressure and temperature increased with an increase in energy density of laser and a decrease in RDT.

Introduction

The thermal effects of laser irradiation on the dental pulp have been studied [1], [2], and researchers have measured the temperature increase in the pulp chamber both in the laboratory and in vivo as a means of investigating pulpal damage. However, pulpal pressure is another characteristic of pulpal physiology which should be investigated [3]. Pulpal space pressure is thought to play a significant role in pulpal inflammation. It has been shown that during pulpal inflammation, pulpal tissue pressure rises [3], [4]. Changes in the pulpal pressure due to different clinical procedures have also been studied both in vivo and in vitro [5], [6], [7]. The thermal effect of laser radiation on dental pulp tissue has been investigated histopathologically, and by measurement of pulpal temperature. However, the effect of laser irradiation on pulpal space pressure has not yet been investigated. The objective of this study was to quantify pulpal space pressure changes and temperature changes during the application of laser irradiation from Nd:YAG laser and to compare it to the pressure produced while cutting with a diamond bur in high-speed handpiece.

Section snippets

Materials and methods

The root tips of 20 sound premolar teeth were collected from adolescents aged between 11 and 18 undergoing orthodontic treatment that required extraction were transected 7 mm from the cementoenamel junction and the root canals were widened to suit the stainless steel pressure transducer tubing. A 1 mm diameter hole was drilled through the proximal surface into the pulp chamber and a calibrated thermocouple wire (Type J Data Instruments, USA) was passed through the hole to monitor temperature

Effect of different tooth preparations

The mean and standard deviation (SD) of pressure and temperature changes for 1, 3 W Nd/YAG laser radiation, changes on removing lased tooth surface (laser surface cut) with the diamond bur and for removing fresh tooth surface (fresh cut) are shown in Table 1. The highest mean pressure and temperature changes (pooled data) were found with 3 W laser irradiation followed by 1 W laser and fresh cut. Mean pressure and temperature changes on removing lased tooth surface with the diamond bur were −0.17 

Discussion

The principal morphologic characteristic of dentin is its fluid-filled tubular structure connecting the pulp to the enamel–dentin junction. It is therefore permeable and almost all dental treatment is believed to alter dentin permeability and allow movement of tubular fluid [9], [10]. When different laser energy densities are used, both a decrease and an increase in dentin permeability was found to be related to specific changes in the dentin surface caused by laser irradiation [11], [12].

Conclusions

The results demonstrate that laser irradiation and use of a high-speed diamond bur did create measurable pulpal space pressure and temperature changes. There was an increase in pulpal temperature and pressure as the power (and corresponding energy density) of laser irradiation increased and the RDT decreased. The high power laser cutting clearly produced approximately four times the pressure changes in the pulpal space and two to three times the temperature change effect of current clinical

Acknowledgements

This study was supported by the University of Melbourne and the Australian Prosthodontic Society. The authors wish to thank Mr P. Barnes and Dr I. Cernavin for their technical assistance and Ms Florence Choo, Statistical Consulting Center, University of Melbourne, for her statistical assistance.

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    ☆

    Based on a thesis submitted to the University of Melbourne, partial fulfillment of the requirements for the degree of Master of Dental Science.

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