The condylar cartilage in the mandible is held to be a:

# The condylar cartilage in the mandible is held to be a: 

A. Primary cartilage

B. Secondary cartilage

C. Tertiary cartilage

D. Non growing cartilage

The correct answer is B. Secondary cartilage.

Meckel's cartilage is the primary cartilage of mandible. The cartilages at the condyle, coronoid and symphysis are the secondary cartilages. The condylar cartilage is considered as the pacemaker for growth of that bone. Nasal septum is considered as the pacemaker for growth of maxilla. 

In Peck and Peck index, mesiodistal and buccolingual measurements of which of the following tooth is taken:

 # In Peck and Peck index, mesiodistal and buccolingual measurements of which of the following tooth is taken: 

A. Maxillary central incisor 

B. Mandibular central incisor

C. Maxillary premolars 

D. Mandibular molars 

The correct answer is B. Mandibular central incisor.

Peck and Peck index: 

The mandibular incisors in persons with no crowding will have smaller mesiodistal width and large labiolingual width than in persons with incisal crowding.

The proportion of the mesiodistal width of each tooth to the labio lingual thickness is calculated using the formula:

M.D.W./L.L.W x100 

Mean value for lower central incisor should be 88 to 92%. 

Mean value for lower lateral incisor should be 90 to 95% 

If the calculated value is greater than mean value, it indicates that the mesiodistal width is more than labiolingual width and hence proximal stripping is indicated. 

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According to Edward H. Angle's classification of malocclusion, what is the defining characteristic of Class III malocclusion?

 # According to Edward H. Angle's classification of malocclusion, what is the defining characteristic of Class III malocclusion?

A) Normal relationship of the molars but malposed teeth

B) Lower molar distally positioned relative to the upper molar

C) Lower molar mesially positioned relative to the upper molar

D) Correct line of occlusion with rotated teeth

The correct answer is C. Lower molar mesially positioned relative to the upper molar.

Angle’s classification of malocclusion in the 1890s was an important step in the development of orthodontics because it not only subdivided major types of malocclusion but also included the first clear and simple definition of normal occlusion in the natural dentition. Angle’s postulate was that the upper first molars were the key to occlusion and that the upper and lower molars should be related so that the mesiobuccal cusp of the upper molar occludes in the buccal groove of the lower molar. If the teeth were arranged on a smoothly curving line of occlusion and this molar relationship existed, then normal occlusion would result. This statement, which 100 years of experience has proved to be correct except when there are aberrations in the size of teeth, brilliantly simplified normal occlusion.

Angle then described three classes of malocclusion, based on the occlusal relationships of the first molars:

• Class I: Normal relationship of the molars, but line of occlusion incorrect because of malposed teeth, rotations, or other causes

• Class II: Lower molar distally positioned relative to upper molar, line of occlusion not specified

• Class III: Lower molar mesially positioned relative to upper molar, line of occlusion not specified

Ref: Proffit, W. R., Fields, H., Msd, D. M., Larson, B., & Sarver, D. M. (2019). Contemporary Orthodontics, 6e: South Asia Edition-E-Book. Elsevier India.