Pericision is carried out as an adjunct retention for:

 # Pericision is carried out as an adjunct retention for:

A. Midline diastema

B. Rotation

C. Proclination

D. Extrusion

The correct answer is B. Rotation.

It is generally assumed that a stable position of the teeth in the dental arch after orthodontic tooth

movement can only be established when the connective tissues of the gingiva have been allowed to adapt to the newly created situation. Supracrestal gingival fibers of an orthodontically moved tooth get

stretched and undergo readaptation very slowly. The pull of these fibers is a major factor in relapse. If these supracrestal fibers are sectioned and allowed to heal while the teeth are held in the proper position, relapse caused by gingival elastic fibers is greatly reduced.

Reattachment of these fibers at a new relaxed position on the root surface stabilizes the tooth in its new

position. This procedure is effective in controlling relapse of derotated teeth.

Reference: Textbook of Orthodontics, 2nd Edition Gurkeerat Singh, Page 279

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Anterior crossbite should be corrected:

 # Anterior crossbite should be corrected:

A. During mixed dentition

B. After all permanent teeth have erupted

C. As soon as possible

D. Any time

The correct answer is C. As soon as possible.

Lingually positioned incisors limit lateral jaw movements and they or their mandibular counterparts sometimes suffer significant incisal abrasion, so early correction of the crossbite is indicated.

Early correction of dental cross bites in the mixed dentition is recommended because it eliminates functional shifts and wear on the erupted permanent teeth, and possibly dentoalveolar asymmetry. There are three basic approaches to the treatment of moderate posterior crossbites in children:

i) Equilibration to eliminate mandibular shift

ii) Expansion of a constricted maxillary arch, and

iii) Repositioning of individual teeth to deal with intra-arch asymmetries.

Reference: Contemporary Orthodontics, Proffit, 4th Edition Page no 248

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# If the permanent canines are lost prematurely, the permanent incisors may drift:

 # If the permanent canines are lost prematurely, the permanent incisors may drift:

A. Labially

B. Distally

C. Medially

D. Lingually

The correct answer is B. Distally.

When a primary first molar or canine is lost prematurely, there is also a tendency for the space to close. This occurs primarily by distal drift of incisors, not by mesial drift of posterior teeth. The impetus for distal drift appears to have two sources: force from active contraction of transseptal fibers in the gingiva, and pressures from the lips and cheeks. 

Reference: Contemporary Orthodontics, 4th Edition, Profitt, Page no. 140

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Final determination of the dental arch form depends on:

 # Final determination of the dental arch form depends on:

A. Angle’s classification

B. Growth pattern

C. Facial type

D. Balance between extraoral and intraoral muscle forces

The correct answer is D. Balance between extraoral and intraoral muscle forces.

Although negative pressure is created within the mouth during sucking, there is no reason to believe that this is responsible for the constriction of the maxillary arch that usually accompanies sucking habits. Instead, arch form is affected by an alteration in the balance between cheek and tongue pressures. If the thumb is placed between the teeth, the tongue must be lowered, which decreases pressure by the tongue against the lingual of upper posterior teeth. At the same time, cheek pressure against these teeth is increased as the buccinator muscle contracts during sucking. Cheek pressures are greatest at the corners of the mouth, and this probably explains why the maxillary arch tends to become V -shaped with more constriction across the canines than the molars. A child who sucks vigorously is more likely to have a narrow upper arch than one who just places the thumb between the teeth.

Reference: Contemporary Orthodontics, 4th Edition, Proffit, Page NO. 152

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