The influence of some Dentin primers on Calcium Hydroxide Lining Cement:

Introduction

Calcium hydroxide liners are often placed in deep cavities under restorative materials to protect the pulpal tissues from chemical insults.  Calcium hydroxide has the ability to stimulate restorative dentin formation with direct pulp contact.  It also serves as a protective barrier for pulp tissue not only by blocking patent dentinal tubules, but also by neutralizing the attack of inorganic acids and leached products from certain cements and restorative materials.¹  Conventional formulations of calcium hydroxide demonstrate low physical properties because it has a low modulus of elasticity.²

Although calcium hydroxide has been used for many years as a dental base or pulp capping material, no specific information exists in the literature on the effect of dentin primers or dentin adhesives that may contain acetone, alcohol, or water on the properties of hard-set calcium hydroxide.

The effect of acid solubility on calcium hydroxide is considered an important property of the material because accidental contamination can occur during the acid-etch technique.³  It is highly desirable that calcium hydroxide over the dentin does not dissolve in the etching solution.⁴

Bruk and Watts⁵ found calcium hydroxide lost a significantly greater percentage of its mass following phosphoric acid etching and washing cycles.  McComb⁶ reported Dycal™ exhibited pronounced solubility in water, while other types of calcium hydroxide remained fairly resistant to acid attack.

Dentin primer is applied routinely prior to bonding to improve the sealing properties of direct polymerizing resins.  Some dentin bonding agents or primers contain water, acetone, or alcohol that may affect the properties of calcium hydroxide.  If dentin bonding agents, or dentin primers are vigorously applied in the cavity without caution, calcium hydroxide can be softened or smeared over the cavity wall and the bonding to dentin will be impaired.  Therefore, the cement must be removed, the wall must be cleansed, and the procedure should be repeated with careful application of a dentin primer.

The aim of this study was to determine the surface erosion and compressive strength of a calcium hydroxide liner after exposure to different types of commercially available dentin primers or dentin adhesives for different periods of time.

Collected by: Dr. Basem Hosnee