Colour Stability of Composite- A Review.

Current innovations in restorative dentistry include nanofilled composite resinmaterials for direct and indirect restorations. Moreover, the advances in adhesivedentistry have provided autopolymerising, dual-polymerizing and lightpolymerizing resin-based adhesives for ceramic restoration bonding. In addition,resin cements have been combined with self-adhesive components for adhesiveprocedures. Composite failure has been a great challenge for dental clinician all overthe world , making it difficult for the dentist to satisfy patients. Major problems seeninclude polymerization, shrinkage and colour instability. There being no perfectmethod for this restorative material to overcome the problems, clinicians must keepin mind as to what material and technique should be used in a patient dependingupon the case. The success of composite restorations is due to their colour stabilityover time. Accurate shade matching of tooth coloured restoration with the adjacentdentition is essential not only at the time of fabrication but also for the lifetimedurability. Discolouration of composite resins can be caused by internal or externalfactors. Internally induced discolouration is permanent and is related to polymerquality, filler type, and amount, as well as the synergist added to the photo initiatorsystem. Alterationof matrix or filler components of resin composites andincomplete polymerization constitute intrinsic factors leading to discolouration. It isreported that saliva, food components, and beverages may affect the aesthetics andintegrity of dental composites. This is a factual truth for dental porcelain but incontradiction, colour instability in porcelain restoration is a common dilemmanowadays, especially when they are exposed to routinely consumable beverages.We have reviewed different factors responsible for colour stability of compositerestoration, and different s

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.

Dentinal Pre-Treatment in Restorative Dentistry.

The advances in adhesive techniques for bonding dental cements to teeth have long been advantageous in dentistry. Adhesive systems offer retaining areas that permit dental restorations to be placed. Bonding to tooth includes bonding to both enamel and underlying dentin. Adhesion to dentin is the main concern as most of damaged teeth have significant amount of misplaced enamel and require good adhesion to dentin. However, dentin exhibits complex structure which makes it difficult to bond with various materials. Hence to enhance bonding between dentin/tooth and adhesive material, it vital to pre-treat dentin with different gents. Various agents are used to treat dentin before restoration is placed. The agents used are chlorhexidine, sodium hypochlorite, benzalkonium chloride, iodine-based disinfectants, ozone, lasers, glutaraldehyde and proanthocyanidins, added hydrophobic resin layer application, ethanol, biomimetic, remineralizing agents, ethylene diamine tetra acetic acid, polyacrylic acid. 2% Chlorhexidine digluconate wash has been shown to successfully conserve the bond strength, when etch-and-rinse adhesive systems were used for up to 6 months. This can be due to inhibitory ability of CHX to the matrix metalloproteinases (MMPs) found in etched dentin. Dentinal pre-treatment is also done to eliminate bacteria remaining in cavity wall. 2.5% NaOCl pretreatment decreased the shear bond strength (SBS) of self-etch adhesive system and suggested NaOCl disinfectant to be used with etch-and-rinse bonding systems. The residual bacteria left behind after restorative procedure may endure and multiply which may lead to pulpal irritation, threat of recurrent caries and / or postoperative sensitivity, and therefore leads to failure of the dental restoration. The occurrence of secondary caries is the most common reason for the restorations failures.Attention to the antimicrobial agents and their effects on the pulp began in the early 1970s by Brännström and Nyborg, who focused on the significance of eliminating residual bacteria remaining on cavity walls.Use of 5.25% NaOCl solution for 15 seconds to eradicate “Staphylococcus aureus, Candida albicans, Porphyromonas gingivalis, and Prevotella intermedia, Porphyromonas endodontalis. Iodine based compounds have capacity to destroy the bacterial cell by affecting its proteins, nucleotides, and fatty acids. EDTA composition are highly successful in eliminate existing biofilms. It prevents biofilm formation by decreasing the adhesion of bacteria.This article reviews various agents, their mechanisms of action on dentin, effect on bond strength, their antibacterial activity, effect of agents on pulp, and comparative studies of these pretreatments. Several available agents have various advantages and disadvantages. Therefore, it is necessary to select appropriate agent for better bonding.