Dentosphere : World of Dentistry

 # Which of the following describes the etiology of cone-cutting? A. Inadequate exposure time B. Excessive mA C. Excessive kVp D. Incorrect source-object distance E. Incorrect placement of X-ray machine The correct answer is E. Incorrect placement of X Ray machine. Cone-cutting occurs when the X-ray machine is not lined up properly with the X-ray sensor or film. The film or sensor should be placed perpendicular to the X-ray collimator to ensure that all of the necessary information is picked up. External devices are often used to ensure that the film/sensor are perpendicular to the X-ray collimator.

  # A periapical radiograph suggests an opaque mass Over the apex of the maxillary right 2nd molar. A second periapical radiograph is made with the X-ray head adjusted in a more mesial direction. The second periapical suggests that the object in question has moved distally compared to the 1st radiograph. Which of the following directions describes the location of the object? A.In-between the roots B. Buccal to the tooth C. Lingual to the tooth D. Not enough information is provided The correct answer is B. Buccal to the tooth. The SLOB (Same Lingual, Opposite Buccal) rule suggests that the object is buccal to the tooth. Because the object moved opposite to the positioning of the X-ray device for the 2nd radiograph it demonstrates buccal positioning If the object moved mesially with the head of the X-ray head being moved mesially, it would have demonstrated lingual/palatal positioning.

 # A person wearing complete denture has difficulty in pronouncing T. The reason may be: A. Too thick palatal area B. Incorrect position of upper incisor teeth C. Too thick mandibular bone D. Reduced salivary flow The correct answer is B. Incorrect position of upper incisor teeth.  - Sounds like t, d, n, etc. are alveolar sounds. These sounds are produced with tip of tongue touching anterior palate. - If maxillary anterior teeth are placed too far anteriorly, 'd' will sound like 't'. - If they are placed too palatally, 't' will sound like 'd'. 

 # Lentulo spirals are used for: A. Locating canal orifice B. Pulp extirpation C. Enlarging coronal third of the root canal D. Application of root canal sealer The correct answer is D. Application of root canal sealer.  - Finger pluggers are used for vertical compaction of gutta percha.  - Finger spreaders are used for  lateral compaction of gutta percha. - Lentulo spiral is used to deliver sealer or triple antibiotic paste to the root canal.