Early closure of a suture is called:

 # Early closure of a suture is called: 

A. Synchondrosis 

B. Ankylosis 

C. Synostosis 

D. Epiphysis

The correct answer is C. Synostosis.

Synostosis is the early or premature fusion of two or more bones that normally remain separate. In the context of cranial sutures, synostosis refers to the premature fusion of the fibrous connective tissue that normally separates the cranial bones, resulting in a reduction or loss of cranial flexibility. This condition is also known as craniosynostosis and can lead to abnormalities in skull shape and brain growth if not treated appropriately.

In contrast, synchondrosis is a type of joint where the bones are connected by hyaline cartilage, such as the joints between the ribs and sternum. Ankylosis refers to the fusion of a joint due to disease or injury, while epiphysis refers to the rounded end of a long bone that forms a joint with another bone.

First evidence of calcification of deciduous incisors is at:

 # First evidence of calcification of deciduous incisors is at:

A. 2 months 

B. Between 1 to 2 months

C. 30 weeks in utero 

D. 11 weeks in utero

The correct answer is D. 11 weeks in utero.

According to "Developmental Dentistry" by J.R. Rooper and A.M. Foreman, the calcification of deciduous incisors begins at around 11 weeks in utero, followed by the development of other teeth in a specific sequence over the subsequent weeks and months of fetal development. 

Maximum development of face takes place in:

 # Maximum development of face takes place in:

A. 1st to 3rd  week of intrauterine life

B. 3rd to 8th week of intrauterine life

C. 9th to 12th week of intrauterine life

D. After 12th  week of intrauterine life

The correct answer is B. 3rd to 8th week of intrauterine life.

The maximum development of the face takes place during the 3rd to 8th week of intrauterine life. This is the critical period for the formation of the facial structures and features such as the eyes, nose, mouth, and ears. During this time, the embryonic tissue undergoes complex interactions and transformations that ultimately give rise to the characteristic appearance of the human face. After the 8th week, further growth and refinement of the facial structures continue, but the basic blueprint has already been established.

Reference: Langman's Medical Embryology by T.W. Sadler

The intercanine width in the mandible is completed by:

 # The intercanine width in the mandible is completed by:

A. 4 to 5 years

B. 7 to 8 years

C. 9 to 10 years

D. 10 to 12 years

The correct answer is C. 9 to 10 years.

The intercanine width in the mandible is typically completed by the time a child is 9 to 10 years old, which is when the mandibular canine teeth have fully erupted and have reached their final position in the arch. This timing can vary slightly between individuals, and it is important to consider other factors such as dental crowding or spacing when evaluating intercanine width.

The reference for this explanation is: Naini FB. Biological basis of orthodontics. John Wiley & Sons; 2015. Chapter 5: Growth and development of the mandible.