Cavities that occur exclusively in posterior teeth are:

 # Cavities that occur exclusively in posterior teeth are:

A. Class 1 cavities

B. Class 5 cavities

C. Class 2 cavities

D. Class 4 cavities

The correct answer is C. Class 2 cavities.

Based on anatomical location of carious lesion, Greene Vardiman Black (G.V. Black) classified tooth preparations into five different classes. Later an additional class, class VI was also added. Class I refers to pit and fissure lesions, whereas all other classes are smooth surface lesions.

G.V. Black's Classification of Tooth Preparations

Class I	All pit and fissure preparations. It Includes: ➤ occlusal surfaces of premolars and molars, ➤ occlusal two-thirds of the facial and lingual surfaces of molars, and ➤lingual surfaces of maxillary incisors
Class II	Preparations involving the proximal surfaces of posterior teeth  (i.e. Premolars and Molars)

Diagnosis of cracked tooth syndrome

 # Diagnosis of cracked tooth syndrome is made by:

A. Biting on solid object and release of pressure

B. Only during bites

C. Percussion

D. All of the above

The correct answer is A. Biting on solid object and release of pressure

The bite test is useful in identifying a cracked tooth or fractured cusp when pressure is applied in a certain direction to one cusp or section of the tooth. It is also helpful in diagnosing cases wherein the pulpal pathosis has extended into the periradicular region causing apical periodontitis. The Tooth Slooth  and the Frac Finder are the popular commercially available devices for the bite test.

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Pain on tooth preparation even on the enamel layer

 # Some patients experience pain on tooth preparation even on the enamel layer. This may be due to:

A. Enamel Tufts

B. Enamel lamellae

C. Enamel spindles

D. Striae of Retzius

The correct answer is C. Enamel Spindles.

Odontoblastic processes occasionally cross the DEJ into enamel; these are termed enamel spindles when their ends are thickened. They may serve as pain receptors, explaining the enamel sensitivity experienced by some patients during tooth preparation.

Ref: Sturdevant’s Art and Science of Operative Dentistry, 7e, André V. Ritter, Lee W. Boushell, Ricardo Walter, Second South Asia Edition, 2019

Page No: 8

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The largest portion of a tooth is formed by:

 # The largest portion of a tooth is formed by:

A. Enamel

B. Dentin

C. Pulp

D. Cementum

The correct answer is B. Dentin.

Dentin forms the largest portion of the tooth structure, extending almost the full length of the tooth. Externally, dentin is covered by enamel on the anatomic crown and cementum on the anatomic root. Internally, dentin forms the walls of the pulp cavity (pulp chamber and pulp canals).

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