Dentosphere : World of Dentistry

# Each of the following patient situations is considered a contraindication for an all- ceramic crown EXCEPT one. Which one is the EXCEPTION? A. Extensive wear of tooth structure or restorations B. Previous history of ceramic crown fractures C. Amalgam restorations with marginal breakdown D. Severe bruxism The correct answer is C. Amalgam restorations with marginal breakdown.  A history of ceramic crown fractures and extensive wear of opposing tooth structure or restorations suggests to the clinician that a heavy occlusal load is present during occlusion. People who chew hard foods and brux severely will place the all-ceramic crown under strong occlusal forces that may cause it to fracture or overly wear the opposing teeth. Extensive and faulty amalgam restorations that are displayed or are not placed esthetically can be better replaced with an all-ceramic crown. Amalgam restorations with marginal leakage and/ or breakdo...

# Which method is the best to manage loss of apical seat due to over-instrumentation? A. Increasing the file size and decreasing the file length B. Prescribing analgesics and antibiotics C. Filling with a gutta-percha cone that is larger D. Using a chelating agent and packing with calcium hydroxide E. Filling with a warm gutta-percha technique The correct answer is A. Increasing the file size and decreasing the file length.  When the apical seat is accidentally removed, the ability to create a hermetic seal at the apex is compromised. In order to avoid this procedural error, a shorter length of file should be used to establish a correct working length. The correction of working length will eventually help re-establish apical seat, then adequate flaring of the apical portion of the canal can be done with the use of larger sized hand files. CLICK HERE FOR MORE MCQs

# Which of the following locations would a perforation present the HIGHEST failure risk? A. Furcation B. Apical 1/3 of the root C. Crown D. Middle 1/3 of the root E. Apex The correct answer is A. Furcation. The HIGHEST risk for endodontic failure is the perforation through the furcation because it is most difficult to seal. Perforations of the crown may be sealed with the final restoration. Perforations near the root apex can be sealed during obturation. Teeth with endodontic perforations may still be successful. Perforations are NOT a guarantee of endodontic failure. CLICK HERE FOR MORE MCQs

# A dentin bonding agent has both hydrophilic and a hydrophobic end. The hydrophilic end bonds to: A. Collagen of dentin B. Calcium of enamel C. Hydroxyapatite of hard tissues D. Resinous restorative material The correct answer is A. Collagen of Dentin. - Bonding of composite restoration to dentin depends on difunctional bonding agent.  - The dentin is hydrophilic and composites are hydrophobic. So, the primer used for bonding composites to dentin should have both the properties.  - Generally, 90% of dentin bonding agents are used for mechanical interlocking. - Key ingredients in primers of dentin bonding systems is hydroxyl ethyl methacrylate. (HEMA) CLICK HERE FOR MORE MCQs