PGCEE MDS 2022: Enzyme responsible for breakdown of ground substance is:

 # Enzyme responsible for breakdown of ground substance is:

a) Hyaluronidase 

b) Coagulase

c) Phosphorylase 

d) Acid phosphatase

The correct answer is A. Hyaluronidase.

Collagenase is responsible for the breakdown of periodontal fibers in periodontitis. It is released by bacteria (P. gingivalis mostly), polymorpho-nuclear leukocytes, and some populations of fibroblasts. Hyaluronidase causes the breakdown of ground substances and helps in the spread of inflammation (cellulitis).

PGCEE MDS 2022: Rapid maxillary expansion is not indicated after:

 # Rapid maxillary expansion is not indicated after:

a) 6 years 

b) 9 years

c) 12 years 

d) 15 years

The correct answer is D. 15 years.

Rapid maxillary expansion should be initiated prior to the ossification of the mid-palatal suture. The time of ossification of the mid-palatal suture is about 16 years in girls and 18 years in boys with a broad range of 15-27 years.

Contraindications of Rapid maxillary expansion:

• Single tooth crossbites

• In adults with severe anteroposterior skeletal discrepancies.

• Vertical growers

• Periodontally weak conditions

The retention period following rapid maxillary expansion should be at least 3 - 6 months.

In slow expansion, the maxillary arch is expanded at a rate of 0.5 - l mm per week.

The forces generated in slow expansion procedures are 2-4 pounds while it is 10-20 pounds (1 pound = 450 gms) in RME.

In rapid maxillary expansion, the treatment is completed in 1-2 weeks whereas in the slow expansion it may take as much as 2-5 months.

PGCEE MDS 2022: Gubernacular canal guides the eruption of:

 # Gubernacular canal guides the eruption of:

a) Primary teeth 

b) Permanent teeth

c) First molar

d) Third molar

The correct answer is B. Permanent teeth. 

Actually the correct answer is Succedaneous teeth. Because, not all permanent teeth have a gubernacular canal. The gubernacular canal and cord help in guiding the permanent teeth during the process of eruption. Except molars, all the permanent teeth (incisors, canines, and premolars) are known as succedaneous teeth because they take the place of their primary predecessors.

Permanent molars are not succedaneous teeth, as they develop from the distal extension of the dental lamina. Successional lamina, which is present on the lingual side of primary dental lamina, is absent for permanent molars.

PGCEE MDS 2022: Chronic burrowing ulcer is caused by:

 # Chronic burrowing ulcer is caused by:

a) Microaerophilic streptococci

b) Peptostreptococcus

c) Streptococcus viridans 

d) Streptococcus pyogenes

The correct answer is A. Microaerophilic Streptococci.

Chronic burrowing type of ulcer is due to symbiotic action of microaerophilic non-haemolytic streptococci and hemolytic Staphylococcus aureus. Clinically it is undermined ulcer with lot of granulation tissue in the floor. This condition is painful, toxaemic and the general condition of the patient deteriorates without treatment. Radical drainage is necessary for cure, antibiotics alone being useless.