26-Tooth root formation - stages. Resorption of primary teeth

Question 1

Phases of tooth root formation

Answer 1

1. Start of tooth root development
2. Short root walls
3. Root walls close to final length
4. Constructed root walls but underdeveloped apex
5. Constructed apex

Question 2

Start of tooth root development

Answer 2

Crown is formed

Root wall construction begins

Question 3

Short root walls

Answer 3

• Short, thin, tapered root walls
• Diverging
• Around end of root ⇢ Growth zone/Dental follicle
• Dental pulp apically wider than cervical ⇢ prior + during tooth eruption
• Periodontium built ⇢ ONLY where there are root walls + is very wide
• PDLs are NOT CONNECTED

Question 4

Root walls are elongated

Answer 4

• Root walls thicken ⇢ parallel + like a tapered spear
• Proliferative zone is clearly visible
• Pulp almost equally wide in cervical area + at end of root walls
• Timing of development of teeth must be known ⇢ avoid fatal errors
• Periodontium created at level of forming root
• Periodontal space is large

Question 5

Root walls are built without apex

Answer 5

• Eruption is completed + Tooth is in function
• Root walls reached length, thickened + slightly convergent
• Pulp is wider cervical + apically narrow
• Apex is not built
• Proliferative zone ⇣

Question 6

Closed apex

Answer 6

• Apex is built
• Periodontium is built along walls of root + area of apex
• Proliferative zone is lacking

Question 7

Root resorption of 1° teeth

Answer 7

Resorption of 1° teeth implemented by resorptive organ

Organ is attached to resorbing root

Resorption occurs under action of eruptive forces of permanent tooth

Question 8

Root resorption + pulp degeneration

Answer 8

1° tooth root susceptibility to resorption > permanent tooth root

• Gradual changes in pulp accompany process of resorption
• 1st sign ⇢ ⇣ no. of cells in pulp
• Nerve trunks degenerate
• Some fibrosis occurs
• Blood vessels remain until root is exfoliated

Question 9

Resorption of incisors + canines

Answer 9

• Permanent dental germs ⇢ situated orally to root of 1° teeth
• Resorption is more advanced orally + w/longer preserved vestibular part of root

Question 10

Resorption of molars

Answer 10

• Takes place between roots of 1° molars
• More advanced in distal part of the root
• Last is absorbed medial vestibular root

Question 11

Reasons for resorption

Answer 11

• Eruptional pressure of permanent tooth:
• Dental germ presses cells of overlying tissues
• Metabolism in these cells are changing
• Cells change their enzymatic activity
• Constructive cells are transformed into degradative cells

Question 12

Osteoclasts

Answer 12

Basic cells of resorption

• derived from monocytes + osteoblasts
• Become multinucleated cells
• 1st place of resorption ⇢ bone separating 1° from permanent tooth
• From here resorption begins

Function

• Resorb bone ⇢ secrete hydrolytic enzymes

Question 13

Phases of resorption

Answer 13

1. Extracellular phase ⇢ mineral separated from collagen + broken into small fragments
2. Intracellular phase ⇢ osteoclasts ingest fragments + continues dissolution of material.

• Crystals appear in cytoplasm of osteoclast + are gradually digested

Question 14

Fibroblast - Fibroclast

Answer 14

Destroy remaining collagen fibres by ingesting them w/intracellular phagolysosome system

• AAs resulting from this used in formation of collagen within the same cell
• Also used in same area for bone formation

Question 15

Stages of resorption

Answer 15

1. Resorbing bone plate between root of 1° tooth + permanent tooth follicle germ
2. Begin resorption of cement + dentin of root of 1° molars
3. Dentin resorption in its inner part by pulp

Question 16

Resorptive organ

Answer 16

Inner layer ⇢ made up of osteoclasts located at root of 1° tooth

Intermediate layer ⇢ infiltration of small cells

Outer layer ⇢ Granulation ⇢ contains blood capillaries + thin fibres