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Join date : 2010-09-19
|Subject: Chap 6 from Dental Embryology, Histology, and Anatomy Sun Sep 19, 2010 1:00 am|| |
chap 6 Questions from Kathy Svec
36. What are the developmental disturbances that can occur with cementum and root formation? answer on page 83.
-disturbance of the root is called dilaceration. It causes the root to be distorted or crown angulation in a formed tooth.
37. What portion of the tooth is considered the root trunk? answer on page 82.
-base of the crown from a single root for a premolars and molars.
38. How do multirooted teeth develop? answer on page 82.
-Differential growth of Hertwigs's Epithelial Root Sheath (HERS) causes the root trunk of the multirooted teeth to divide into two or three roots. Elongation of its cervical loop occur in such a way that long, tongue like horizontal epithelial extensions or flaps develop within. The single cervical opening of the coronal enamel organ is then divided into two or three openings by these horizontal extensions. On the pulpal surfaces of these holes, dentin formation starts after the induction of the odontoblasts and disintegration of HERS and the associated basement membrane. At the periphery of each opening are cementoblasts induced to form cementum on the newly formed dentin. Root development the proceeds in the same way for single rooted tooth.
39. What is the differences between active and passive eruption? answer on page 84.
-the difference is that active eruption involves actual vertical movement compare to passive eruption. Passive eruption occur as we age, gingiva recedes and no actual tooth movement takes place.
40. What occurs during active eruption? answer on page 85,86.
-The reduced enamel epithelium (REE) fuses with the oral epithelium lining the oral cavity. Enzymes from REE disintegrate the central portion of the fused tissue, leaving an epithelial tunnel for the tooth to erupt through into the surrounding oral epithelium of the oral cavity, the coronal portion of the fused epithelial tissues peels back off the crown leaving the cervical portion still attached the neck of the tooth.