In sutures, there is proliferation of connective tissue followed by replacement of bone. This is called:

 # In sutures, there is proliferation of connective tissue followed by replacement of bone. This is called:

A. Endochondral bone growth

B. Intramembranous growth

C. Appositional growth

D. Periosteal growth

The correct answer is B. Intramembranous growth.

During the fourth month in utero, there is an ingrowth of blood vascular elements into various points of the chondrocranium (and the other parts of the early cartilaginous skeleton). These areas become centers of ossification, at which cartilage is transformed into bone in the process called endochondral ossification, and islands of bone appear in the sea of surrounding cartilage. The cartilage continues to grow rapidly but is replaced by bone with equal rapidity. The result is that the amount of bone increases

rapidly and the relative (but not the absolute) amount of cartilage decreases. Eventually, the old chondrocranium is represented only by small areas of cartilage interposed between large sections of bone, which assume the characteristic form of the ethmoid, sphenoid, and basioccipital bones. Growth at these cartilaginous connections between the skeletal bones is similar to growth in the limbs.

Not all bones of the adult skeleton were represented in the embryonic cartilaginous model, and it is possible for bone to form by secretion of bone matrix directly within connective tissues, without any intermediate formation of cartilage. Bone formation of this type is called intramembranous ossification. This type of bone formation occurs in the cranial vault and both jaws. 

Ref: Contemporary Orthodontics, William R. Proffit

Epigenetic factors controlling the growth of skeleton are:

 # Epigenetic factors controlling the growth of skeleton are:

A. Genetic factors present within skeleton

B. Genetic factors present outside skeleton

C. Local genetic factors

D. General non-genetic factors

The correct answer is B. Genetic factors present outside the skeleton.

According to "Van Limborgh's" multifactorial theory, growth is under control of genetic and environmental factors. Intrinsic genetic factors are the factors present within the skeleton. Epigenetic factors present outside the skull and manifests their influence in indirect way by intermediary action on associated structures Eg:- Eyes, brain etc. 

All of the following increase primary stability of miniscrew implants EXCEPT:

 # All of the following increase primary stability of miniscrew implants EXCEPT: 

A. Cortical predrilling

B. Cortical bone thickness

C. Spongy bone thickness

D. Length or diameter

The correct answer is A. Cortical predrilling

• Studies about various miniscrew designs to improve primary stability are increasing. Different changes in screw diameter, length and the design of the threads have been investigated

• Primary stability is influenced and increased by optimum loading, good bone density, more cortical bone thickness, advance screw design and root proximity. 

• Drill free method of MSI insertion is much better than pre-drilled method for primary stability of mini screw implants as in case of pre drilled method more heat is produced which leads to compromised bone regeneration hence jeopardize implant stability. 

The characteristic feature of Brader arch form is:

 # The characteristic feature of Brader arch form is:

A. Resembles metal chain hanging from two ends

B. Expanded in second molar region

C. Constricted in second molar region

D. Offsets in premolar region are present

The correct answer is C. Constricted in the second molar region.

Brader arch form: 

• Based on a trifocal ellipse 

• Trifocal ellipse almost the same wide as the catenary curve anterior segment 

• It has a somewhat wider premolar segment than the catenary curve 

• In the posterior segment trifocal ellipse constricts gradually while catenary curve does not 

• This arch form is more constricted or closely approximate at 2nd & 3rd molars