Stages of Tooth Development in a Multirooted Tooth

 Description of modified Moorrees' stages (Moorrees et al., 1963a,b) used to identify tooth developmental stages of multirooted teeth. 

Average vertical length a mandible moves in a chewing cycle is:

  # Average vertical length a mandible moves in a chewing cycle is:

A. 3-5 mm

B. 10-12 mm

C. 16-20 mm

D. 50-60 mm

The correct answer is C. 16-20 mm.

Chewing is highly complex oral motor behavior usually seen in the frontal plane in simple form. No archetypal chewing cycle exists. The means of the dimensions of the chewing cycle are between 16 and 20 mm for vertical movements and between 3 and 5 mm for lateral movements. The duration of the cycle varies from 0.6 to 1 second depending on the type of food. The speed of masticatory movement varies within each cycle, both according to the type of food and among individuals. Speed, duration, and form of the chewing cycle vary with the type of occlusion, kind of food, and presence of dysfunction.

Reference: Wheeler's 10th Edition Page 263

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Oblique ridge at the centre of occlusal surface is reduced to the level of:

  # Oblique ridge at the centre of occlusal surface is reduced to the level of:

A. Central groove

B. Marginal ridges

C. Cusp tips

D. All of the above

The correct answer is B. Marginal ridges.

The oblique ridge is a ridge that crosses the occlusal surface obliquely. The union of the triangular ridge of the distobuccal cusp and the distal ridge of the mesiolingual cusp forms it. This ridge is reduced in height in the center of the occlusal surface, being about on a level with the marginal ridges of the occlusal surface. Sometimes it is crossed by a developmental groove that partially joins the two major fossae by means of its shallow sulcate groove.

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Which Premolar develops from five lobes?

  # Which of the following premolars develop from five lobes?

A. Maxillary first premolar

B. Maxillary second premolar

C. Mandibular first premolar

D. Mandibular second premolar

The correct answer is D. Mandibular second premolar.

The mandibular first premolars are developed from four lobes, as were the maxillary premolars. The mandibular second premolars are, in most instances, developed from five lobes, three buccal and two lingual lobes.

Reference: Wheeler's, 10th Edition, Page 151