Elsevier

Journal of Endodontics

Volume 36, Issue 10, October 2010, Pages 1643-1647
Journal of Endodontics

Basic Research
Effect of Hydration on the Strain Gradients in Dental Hard Tissues after Heat and Cold Application

https://doi.org/10.1016/j.joen.2010.06.027Get rights and content

Abstract

Introduction

This study was aimed to investigate the thermal strain gradients on dental hard tissues to localized heat and cold applications, applied to assess the vitality of pulp. The role of hydration on the thermal strain distribution within the enamel, dentin, and dentino-enamel junction (DEJ) was examined by using a digital moiré interferometry.

Methods

Extracted bovine incisors were prepared, and high-frequency diffraction gratings were replicated on one surface. Heat (120°C–140°C) and cold (–50°C) stimuli were applied on the external surface, and the strain patterns were recorded and analyzed for the first 3 seconds. The specimens were tested under fully hydrated and partially dehydrated conditions (72 hours at 24°C, 60% relative humidity).

Results

Distinct thermal strain gradient was observed in the enamel, dentin, and DEJ after the application of heat and cold stimuli. Application of both heat and cold resulted in significantly higher strains in the partially dehydrated teeth than in the fully hydrated teeth (P < .05). There was only a marginal increase in strains at the location of application of stimuli in hydrated teeth. The DEJ in both the fully hydrated and partially dehydrated teeth showed the highest strains.

Conclusions

There was a marked difference in the thermal strain gradients within dental hard tissues after the application of heat/cold stimuli, depending on the level of tissue hydration. The findings from this study highlighted the role of free water and structural characteristics of enamel, dentin, and DEJ in dissipating the thermal strains in the tooth.

Section snippets

Specimen Preparation

Eight extracted bovine incisors maintained in deionized water at 4°C were used in this study. The teeth were transilluminated and excluded from the experiment if cracks were present. Specimens were prepared as 3-mm parallel-sided slabs along the sagittal plane, as mentioned in the previous literature (Fig. 1A) (12).

Experiments

Details of DMI used in this study are described elsewhere (12). The specimen gratings were produced by replicating a high-frequency cross-line grating (1200 lines/mm) onto the

Strain Distribution in Dental Hard Tissues

Fig. 2 shows the strain distribution pattern in dental hard tissues in the direction perpendicular to the dentinal tubules (U field) in the partially dehydrated and fully dehydrated conditions. The initial zero-order fringe pattern showed deformation after application of heat/cold stimuli. In fully hydrated condition, the DEJ showed highest strains as compared with enamel and dentin. In a fully hydrated tissue both heat and cold stimuli did not produce any significant change in strains in

Discussion

Sagittal section of bovine teeth (faciolingual plane) was examined in this study to evaluate the thermal strain distribution in enamel, dentin, and DEJ (11). This anatomical section was chosen because of the prominent gradients in mineralization and mechanical properties (elastic modulus and hardness) exhibited by dentin in this plane (18). The pulp tissue consists of a connective tissue system made up of cells and fibers embedded in an extracellular matrix. The extracellular matrix proteins

Acknowledgments

The authors disclose no conflicts of interest.

References (27)

  • M. Brannstrom et al.

    Movements of the dentin and pulp liquids on application of thermal stimuli: an in vitro study

    Acta Odontol Scand

    (1970)
  • D.H. Pashley et al.

    Dentin permeability: effects of temperature on hydraulic conductance

    J Dent Res

    (1983)
  • R.Z. Wang et al.

    Strain-structure relations in human teeth using Moiré fringes

    J Biomech

    (1998)
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