Dentosphere : World of Dentistry

# To extend the life of a tungsten carbide bur, the bur should... A. Be moving slow before contacting tooth structure B. Be sterilized with heat sterilization C. Contact tooth structure before rotating D. Be moving fast before contacting tooth structure The correct answer is D. Be moving fast before contacting tooth structure. The lifespan of a tungsten carbide bur can be extended by bringing the bur up to speed  before contacting tooth structure, because it decreases the friction between the bur and the tooth structure thereby decreasing damage to the bur and the pulp. Sufficient rotating speed makes the cutting edge of the bur more efficient even with using light pressure. Heat sterilization corrodes the carbon steel and anneals the cutting edge of the bur.

# In Which dental procedure is a rubber dam most indicated? A. Deep caries B. Direct pulp capping C. Indirect pulp capping D. Preparing a crown The correct answer is: B. Direct Pulp capping.  In direct pulp capping, it is essential to have adequate access, visibility, and isolation of the operating field. Direct pulp capping is indicated if a pin-point pulp exposure is made during cavity preparation. Teeth should be properly isolated to avoid saliva and bacterial contamination during direct pulp caps. Proper isolation of the operating field also allows proper sealing of the cavity of the tooth. 

# The single most important factor in producing cariogenic plaque is: A. High amount of glucose exposure B. High frequency of glucose exposure C. High amount of sucrose exposure D. High frequency of sucrose exposure The correct answer is: D. High frequency of sucrose exposure. High-frequency exposure to fermentable carbohydrates such as sucrose may be the most important factor in producing cariogenic biofilm and ultimately caries lesions. Frequent ingestion of fermentable carbohydrates begins a series of changes in the local tooth environment, essentially changing the composition of the biofilm, thus favoring the growth of highly acidogenic bacteria that eventually leads to caries lesion formation. In contrast, when ingestion of fermentable carbohydrates is severely restricted or absent, biofilm growth typically does not lead to caries lesions. Sucrose in particular allows the formation of extracellular polysaccharides, which render the biofilm viscous and stic...

# The liquid system of glass ionomer restorative material is essentially: A. Polyalkanoic acid B. Phosphoric acid C. Polyacrylic-itaconic acid D. Hydrochloric acid The correct answer is C. Polyacrylic-itaconic acid. COMPOSITION OF GLASS IONOMER CEMENTS Powder/liquid materials Powder -  Sodium aluminosilicate glass with about 20% CaF and other minor additives Liquid - Aqueous solution of acrylic acid/itaconic acid copolymer or Aqueous solution of maleic acid polymer or maleic/acrylic copolymer and Tartaric acid in some products to control setting characteristics Powder/water materials Powder - Glass (as above) + vacuum-dried polyacid (acrylic, maleic or copolymers) Liquid - Manufacturers supply a dropper bottle which the operator fills with water or The manufacturer supplies a dilute aqueous solution of tartaric acid