lesson 12 the process of tooth eruption and the shedding of primary teeth

How does the crown move with eruption?

moves up into the mouth; occlusally

how does the root move with eruption?

growing apical and of the root maintains position

How do incisors typically erupt? (directionally)

erupt straightforwardly into occlusion.

Where do premolars position themselves during eruption?

between the roots of the primary molars they will replace.

What is unique about the eruption of first molars?

develop easily as they do not have any teeth to replace.

How do second and third molars typically erupt?

are usually positioned further back/out of place and must rotate and tip into position as they erupt.

which teeth have to rotate and tip into position due to how they form out of place?

second and third molars

what sheds the primary teeth?

odontoclasts

What are odontoclasts?

Cells that differentiate from ectomesenchyme and are responsible for resorbing tooth structures during shedding.

what specific tooth structures do odontoclasts resorb?

cementum, dentin, enamel

What role do osteoclasts play in tooth eruption?

absorb alveolar bone that may obstruct the path of the adult tooth during eruption.

What happens to the root structure of primary teeth during shedding?

Odontoclasts eat away at it

what is the process of shedding?

root resorbs, PDL is lost, rootless crown of tooth "falls" off the jaw

What is ankylosis in the context of tooth eruption?

occurs when a tooth fuses to the bone, preventing normal eruption due to the absence of a periodontal ligament.

what is missing in ankylosis?

PDL

how many teeth erupt for the primary dentition?

20

What is the typical sequence of tooth eruption for primary teeth?

central incisor, lateral incisor, first molar, canine, second molar

primary maxillary central incisor eruption

8-12 months

primary maxillary lateral incisor eruption

9-13 months

primary maxillary canines eruption

16-22 months

primary maxillary first molars eruption

13-19 months

primary maxillary second molars eruption

25-33 months

primary mandibular central incisor eruption

6-10 months

primary mandibular lateral incisor eruption

10-16 months

primary mandibular canine eruption

17-23 months

primary mandibular first molar eruption

14-18 months

primary mandibular second molar eruption

23-31 months

are baby teeth present in the jawbones at birth?

yes, teeth begin forming before birth (think of the neonatal line)

do the mandibular or maxillary teeth erupt first?

mandibular

by what age do all of your child's primary teeth appear by?

age 3

how can you determine the shedding sequence of primary dentition?

it aligns with the eruption dates of the permanent dentition

what is the usual sequence of eruption of the permanent dentition in each quadrant?

1. first molar

2. central incisor

3. lateral incisor

4. first premolar

5. second premolar

6. canine

7. second molar

8. third molar

what is the first tooth to erupt in the permanent dentition?

first molar ("6 year molar")

permanent maxillary first molar, mandibular first molar, and mandibular central incisor eruption

6-7 years

permanent mandibular lateral incisor and maxillary central incisor eruption

7-8 years

permanent maxillary lateral incisor eruption

8-9 years

permanent mandibular canine eruption

9-10 years

permanent maxillary first premolar eruption

10-11 years

permanent mandibular first premolar and maxillary second premolar eruption

10-12 years

permanent mandibular second premolar and maxillary canine eruption

11-12 years

permanent mandibular second molar eruption

11-13 years

permanent maxillary second molar eruption

12-13 years

permanent mandibular and maxillary third molar eruption

17-21 years

permanent dentition eruption sequence? (check)

1. mand and max first molar, mand central incisor

2. max central incisor and mand lateral incisor

3. max lateral incisor

4. mand canine

5. max first premolar

6. max second premolar and mand first premolar

7. mand second premolar and max canine

8. mand second molar

9. max second molar

10. max and mand third molar

What three causes can a delay in tooth eruption?

if no permanent successor is present, the primary tooth may be used for many more years without loss of root (root resorption of primary roots may occur in various ways),

external resorption of permanent tooth roots if remnants of the developmental dental follicle of permanent tooth are next to it (third molar resting against second molar root)

if primary incisor is knocked out (age 3-5) sometimes the permanent incisor eruption is delayed for years

what can happen if there is no permanent successor of a primary tooth?

root resorption won't occur for many years

what can cause resorption of permanent tooth roots?

remnants of developmental dental follicle of a permanent tooth next to it

where does this often occur: permanent root resorption from developmental dental follicle of permanent tooth next to it

when impacted third molar rests against the root of a second molar

what can happen if a primary incisor is knocked out during the ages of 3 to 5?

permanent incisor may have delayed eruption of several years