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.

The main growth site for mandible is:

 # The main growth site for mandible is:

A. Condyle 

B. Angle

C. Symphysis 

D. Body

The correct answer is A. Condyle.

The mandibular condyle is the main growth site for the mandible. The condyle is a specialized growth center that contributes to both the length and width of the mandible. The condyle grows through endochondral bone formation, which involves the transformation of cartilage into bone tissue. The growth of the condyle is regulated by various factors such as growth hormones, growth factors, and mechanical stimuli.

While the other parts of the mandible also contribute to its overall growth and development, the condyle is the primary growth site for the mandible.

Therefore, the correct answer is A, the condyle.

Reference: Proffit, W. R., Fields, H. W. Jr, & Sarver, D. M. (2013). Contemporary Orthodontics. (5th ed.). St. Louis, MO: Mosby/Elsevier. Chapter 4: Growth of the Face and the Jaws.

Meckel's cartilage is essential for mandibular growth because:

 # Meckel's cartilage is essential for mandibular growth because:

A. It is converted into bone 

B. It is a template for bone deposition

C. It is a skeletal unit

D. It is a secondary cartilage

The correct answer is B. It is a template for bone deposition.

Meckel's cartilage is a temporary cartilage structure that forms the basis of the mandibular skeleton in the early embryo. During development, the cartilage acts as a template for the formation of bone, and the mandible grows around it. Meckel's cartilage eventually undergoes resorption, and the mature mandible is formed through a combination of endochondral and intramembranous ossification.

Therefore, the correct answer is B, that Meckel's cartilage is essential for mandibular growth because it serves as a template for bone deposition.

Reference: Proffit, W. R., Fields, H. W. Jr, & Sarver, D. M. (2013). Contemporary Orthodontics. (5th ed.). St. Louis, MO: Mosby/Elsevier. Chapter 4: Growth of the Face and the Jaws.