ABSTRACT
Tooth has two main organs- pulp and dentin which remain closely integrated. They depend on each other both functionally and anatomically, throughout the life of tooth. Protection of these tissues is important from trauma during cavity preparation or tooth preparation, from caries, from mechanical forces, from chemicals produced by bacteria and from galvanic shock and thermal injury. The main aim of the operative dentistry is to protect this tissue and preserve tooth vitality.(1) The purpose of a restoration is to replace missing tooth structure and provide the pulp adequate strength and protection from external insults. Sometimes, the restorations and \ or the restorative material is incapable of providing this property; hence, an auxiliary material such as liner and base or sub-base is required, which can fulfil this function. The material used to protect this tissue is called pulp protecting material or pulp capping material. For many decades clinicians have been using liners and bases under restorations. The type of auxiliary material to be used depends upon the minimum dentinal thickness which is left between the surface of the cavity and pulp. This is known as remaining dentin thickness (RDT). Dentin has excellent buffering capacity to neutralize the effects of cariogenic acids, and insulates the pulp from temperature increases during cavity percolation. The single most important criterion for protecting pulp is remaining dentinal thickness which is dependent upon the depth of cavity preparation.(2)
ABSTRACT
The most important feature that a material must have is sufficient, long term sealing of the restorative margins. No restorative material developed to date is completely adhesive to the tooth structure. Every restorative material allows some degree of passage of fluids and micronutrients through it. It is termed as Leakage. By definition Micro leakage is “the clinically undetectable passage of bacteria, fluids, molecules or ions between a cavity wall and the restorative material”. It is the flow of a substance into a defect at the interface of restoration and tooth margin. Marginal leakage around restorative margins has been a concern with various clinical conditions. It includes quickening of the breakdown and dissolution of restorative materials. Marginal staining leads to collapse of margins, compromise in aesthetics and with time the need to substitute the restoration. Microleakage depends on several variables like dimensional change of restorative material mainly because of thermal contraction, polymerisation shrinkage, water sorption, mechanical stresses and dimensional changes of tooth. Almost all microleakage studies suggested that the majority of the materials accessible currently leak meaning that they allow penetration of dyes, radioisotopes, or bacteria. Microleakage can be calculated by various in vitro methods with or without thermocycling like staining, SEM, chemical agents, neutron activation analysis, ionization, autoradiography, radioisotope, and reversible radioactive adsorption. Reducing the marginal leakage and enhancing the marginal adaptation involves various factors like choice or combinations of materials, use of cavity liner or base, cavity design or configuration factor changes, acid etching and bonding, technique of restoration placement, direct or indirect techniques, sealing the marginal gaps, and different curing strategies. This article describes in depth the knowledge about various aspects of leakage such as sequelae and causes of microleakage, methods of detection of microleakage in vitro as well as clinically, and the measures taken to reduce or decrease the microleakage when restoring tooth with resin-based restorations.