PDL fibers that prevent extrusion are:

 # PDL fibers that prevent extrusion are: 

A. Horizontal

B. Oblique

C. Transseptal

D. Alveolar crest fibers

The correct answer is D. Alveolar crest fibers.

Alveolar crest fibers extend obliquely from the cementum just beneath the junctional epithelium to the alveolar crest. Fibers also run from the cementum over the alveolar crest and to the fibrous layer of the periosteum that covers the alveolar bone. The alveolar crest fibers prevent the extrusion of the tooth and resist lateral tooth movements. The incision of these fibers during periodontal surgery does not increase tooth mobility unless significant attachment loss has occurred.

Reference: Carranza's

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