Role of Liners in Restorative Dentistry.

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)

Functions of Root Canal Sealers- A Review.

Endodontic therapy is a treatment for the diseased pulp of a tooth. It will result in the removal of infection and the preservation from further microbial invasion. The principle constituents of an endodontic filling are- a core material “gutta percha” and “endodontic sealers”. All the current obturating techniques make use of the sealer to augment the seal endodontic filling material. It fills the space between canals. Endodontic sealer fills the space between the material as well as root dentin. Different types of sealers are available (resin sealers, ZOE sealers, mineral trioxide aggregate sealer, bio-ceramic containing sealers, glass ionomer containing sealer, calcium hydroxide containing sealer). Root canal sealers have different functions- antibacterial, lubricant for core material, to increase radio-opacity of core or as a filling material. Different types of microorganisms as well as microbial products cause pulpal as well as peri-radicular diseases. Microorganisms persist in the canal due to poor irrigation. We wanted to evaluate the various functions of different endodontic sealers. The perfect apical seal obtained by use of sealers is one which is stable and non-irritating in nature. It should also give us a smoother seal. Biocompatibility of root canal sealer has importance as it is placed directly in contact with the living tissue. Response of dental tissue help in the final outcome of successful endodontic treatment. Bond strength between canal walls exhibit through micromechanical retention. It helps in preventing the dislodgement of filling material. It ultimately helps in maintenance of interface between filling material and sealers. Push out test is the process to assess bond strength among filling material and sealers. Endodontic sealer has sufficient amount of radiopacity so that it can be clearly visualised among material and adjacent anatomical structures.

Removal Techniques for Intracanal Medicament- A Review

This article reviews irrigation techniques for removal of intracanal medicament in endodontic practice. Microorganisms are the primary etiological factors for pulpal and periradicular diseases. So primary purpose is to completely eradicate microorganism from the root canal. It is done through chemo-mechanical preparation of the canal. Complete disinfection of the pulp space cannot be achieved with most sophisticated instrumentation techniques. Therefore use of inter appointment intracanal medicaments is mandatory. Removal of the medicament is mandatory, as its remnants may mechanically block the apical area of the root canal system. Also affects viscosity, working time, tubule penetration and adhesion of root canal sealers. Remnants of Ca(OH)2 in the canal react with unreacted eugenol present in ZOE based sealer to form calcium eugenolate. Today’s irrigation armamentarium presents a diverse variety of tools and techniques , that can assist the practitioner in reducing bacteria, debris, intracanal medicament within the canal system. Conventional syringe irrigation is a routinely practiced method for removal of medicament. It consists of delivering the irrigant in the canal passively or by agitation. Rotary brush does not actually render irrigating solution for removal of medicament. This acts like auxiliaries during removal of medicament from canal or for increased movement of irrigating solution. Ultrasonic irrigation is done with or without simultaneous ultrasonic instrumentation. EndoVac is negative pressure irrigation, which can be used as an alternative method that helps in safe removal of medicament in apical thirds. RinsEndo is also based on pressure alteration technology like EndoVac. Sonically driven system safely acti­vates various intracanal reagents and vigorously produces the hydrodynamic phenomenon as it includes EndoActivator and Vibringe. Laser activated irrigation is more effective for cleaning of root canal. Er:YAG is most commonly used laser in endodontics. Therefore, the aim of this article is to highlight the irrigation techniques used for removal of the intracanal medicament in endodontic practice.

Microleakage in Composite Resin Restoration- A Review Article.

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.