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.

CLICK HERE FOR MORE MCQs

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

CLICK HERE FOR MORE MCQs

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).

CLICK HERE FOR MORE MCQs

Number of enamel rods in a maxillary molar is about:

 # Number of enamel rods in a maxillary molar is about:

A. 8 million

B. 12 million

C. 20 million

D. 30  million

The correct answer is B. 12 million.

The rods vary in number from approximately 5 million for a mandibular incisor to about 12 million for a maxillary molar. The rods are densely packed and intertwined in a wavy course, and each extends from the dentinoenamel junction (DEJ) to the external surface of the tooth.

CLICK HERE FOR MORE MCQs

Teeth with longest roots in human dentition are:

 # Teeth with longest roots in human dentition are:

A. Incisors

B. Canines

C. Premolars

D. Molars

The correct answer is B. Canines.

Canines possess the longest roots of all teeth and are located at the corners of the dental arch. They function in the seizing, piercing, tearing and cutting of food. From a proximal view, the crown also has a triangular shape, with a thick incisal ridge. The anatomic form of the crown and the length of the root make these teeth strong, stable abutment teeth for a fixed or removable prosthesis.

CLICK HERE FOR MORE MCQs

The remnants of epithelial root sheath found in periodontal ligament

 # The remnants of epithelial root sheath found in periodontal ligament are called:

A. Enamel pearls

B. Enamel knots

C. Rests of Malassez

D. Epithelial diaphragm

The correct answer is C. Rests of Malassez.

The development of root does not begin till the enamel and dentin reach the future cemento-enamel junction. In development of root, enamel organ performs a very important function by forming Hertwig’s epithelial root sheath. Hertwig’s epithelial root sheath is molded and assumes tall shape of root by initiation of radicular dentin formation with the help of differentiation of radicular cells into the odontoblasts. Enamel on radicular portion is not formed because of the absence of stratum intermedium. The remnants of the epithelial root sheath are embedded in the periodontal ligament of erupted teeth and are called as epithelial rests of Malassez.

CLICK HERE FOR MORE MCQs