TOOTH ERUPTION

 

TOOTH ERUPTION

v  Eruption

Ø  The movement of the tooth through the surrounding tissue so that the clinical crown gradually appears longer

§  NOT Exfoliation (Don’t get clowned)

Ø  Tooth makes its appearance in the mouth when one-half of the root is completed

v  3 Stages of Dentition

Ø  Primary Dentition (6 ms to 6 yrs)

Ø  Mixed Dentition (6 yrs to 12 yrs)

§  Commences with the 1^st Perm Molars

Ø  Permanent Dentition (12 yrs+)

v  Permanent Dental Formula

Ø  I 2/2  C1/1  B2/2  M3/3 = 16 x 2 = 32

Ø  An imaginary animal (I 2/2  C1/1  M2/2) has the same # of anterior teeth as are found in a human’s permanent dentition

v  Deciduous Dental Formula

Ø  I 2/2  C1/1  M2/2 = 10 x 2 = 20

v  Succedaneous teeth

Ø  Centrals to 2^nd PMs

Ø  When extracting a primary Mx incisor in which the root has been partially resorbed due to pressure from its developing succedaneous tooth, the buccal aspect will usually be longest & attached most securely to the gingiva

Ø  The first evidence of root resorption on a primary incisor is seen on the lingual root surface

v  Primary Teeth

Ø  All 20 primary teeth – in utero

§  Begin to form about 6 weeks in utero

§  Begin to calcify about 4-6 months in utero

·         Primary teeth show calcification in utero during the 2^nd trimester

·         1^st and 2^nd molars show calcification during 5-6 months and completed by 3yrs

§  Primary roots are completed

·         14 months after emergence for Mn

¨       Mn teeth erupt from 6-7 months to 20 months

·         15 months after emergence for Mx

¨       Mx teeth erupt from 7 months to 24 months

§  Calcification of the roots is normally completed by 3-4 yrs old

·         Remember last tooth comes in at 24 months Primary Mx M2

§  At 1.5 yrs, roots are completed for Mn centrals and laterals and Mx Centrals???

Ø  Primary Calcification Initiation Sequence

§  Mn                                  (in weeks)

·         Centrals                 14

·         Laterals                 16

·         Canines                 17

·         M1                          15.5

·         M2                          18

§  Hypoplasia of primary teeth limited to the incisal thirds of incisors, incisal tips of canines, and occlusal portion of molars indicates a metabolic disturbance during the prenatal period

§  If a women took tetracycline during the second trimester, what teeth would be affected???? (Week 13-27)

·         Primary teeth ONLY

¨       Note Tetracycline affects teeth erupting 1-2 years after taking it

Ø  Eruption Sequence

§  Primary Eruption Sequence From the Tooth Bible

§  CLCLM1M1CaCaM2M2

C	L	C	L	M1	M1	Ca	Ca	M2	M2
6 mos	7	7.5	9	12	14	16	19	20	24

 

·         Mn central (6 months)

·         Mn laterals (7)

·         Mx central (7.5)

·         Mx lateral (9)

·         Mn M1 (12)

¨       1 yr, you should have 10 teeth…Unless you’re a girl then @13 months you’ll have 12 teeth!!!

·         Mx M1 (14)

·         Mn canine (16)

·         Mx canine (19)

·         Mn M2 (20)

·         Mx M2 (24)

§  Deciduous eruption sequence: Central, Lateral, M1, Canine, M2

·         The last primary tooth to erupt is the Mx M2

¨       Also last to start and finish calcifying

§  The first primary teeth to erupt are the Mn R & L central incisors

§  At 1 year, a child is expected to have erupted prim Mx & Mn incisors & M1s

·         A parent notices a new primary tooth at 12 months, most likely a Mn M1 (12 month Molar)

§  Prim M2s are expected to erupt shortly after the child’s 2^nd birthday

§  Last anterior tooth to calcify

§  Most dramatic change to the Oral Flora occurs à when primary teeth erupt

Ø  Exfoliation sequence for Primary Teeth

§  Centrals                         6-8 yrs

§  Laterals                         7-9 yrs

§  1^st Molars                      10-12 yrs

§  Canines                         9-12 yrs (10-11 for Mx canine was the correct answer option)

§  2^nd Molars                     10-12 yrs

Ø  Primate Space

§  Occur in deciduous dentition

§  Mx: space between laterals & canines

§  Mn: space between canines & M1s

§  NOTE: Spacing always occurs, but these are most noticeable

·         The perm dentition differs from primary in that primary teeth develop arch diastemata

§  Occur in 50% of children

§  Spacing between anterior teeth in the dentition is most frequently caused by growth of the dental arches

v  Permanent teeth

Ø  Begin to form at 4 months in utero

Ø  Calcification Initiation Sequence

§  Mx

·         M1                          Birth

·         Centrals                 3-4 months

·         Canines                 4-5 months

·         Laterals                 10-12 months

¨       The Last Permanent Anterior Tooth of the Mx to initiate calcification is the Lateral @10 months

·         PM1                       18-21 months

·         PM2                       2-2.5 years

·         M2                          2.5-3 years

·         M3                          7-9 years

§  Mn

·         M1                          Birth

·         Centrals                 3-4 months

·         Laterals                 3-4 months

·         Canines                 4-5 months

¨       Don’t get clowned, here it’s the Canine as the last anterior to initiate calcification

·         PM1                       21-24 months

·         PM2                       2-2.5 years

·         M2                          2.5-3 years

·         M3                          8-10 years

Ø  Mx & Mn M1s begin to calcify at birth

§  In development of the human permanent dentition, the first teeth to begin calcification are the Mn M1s

·         Initiation of calcification for the mandibular central incisors is 3-4 months

Ø  The incisal ridge is the 1^st structure to begin to calcify in an anterior tooth

Ø  Perm M3s begin to calcify at 8-10 yrs of age

Ø  Active eruption of teeth occurs after ½ of the root is formed (perm or primary)

§  50% of root calcification is complete at the time of eruption

Ø  The apex is usually fully developed by 2-3 years after eruption

v  Permanent Dentition Eruption Schedule

 

Permanent Dentition
Typical Eruption Age (yrs)	Range	Maxillary	Mandibular	Calcification	Root Completion	Enamel Completion
6	6 to 7		1st molar	Birth	9-10 yrs	2.5-3 yrs
6	6 to 7	1st molar		Birth	9-10 yrs	3-4 yrs
6	6 to 7		central incisor	3-4 mos	9 yrs	4-5 yrs
7	7 to 8	central incisor		3-4 mos	10 yrs	4-5 yrs
7	7 to 8		lateral incisor	3-4 mos	10 yrs	4-5 yrs
8	8 to 9	lateral incisor		10 months	11 yrs	4-5 yrs
10	9 to 10		Canine	4-5 mos	12-14 yrs	6-7 yrs
10	10 to 12		1st premolar	1.75-2 yrs	12-13 yrs	5-6 yrs
10	10 to 12	1st premolar		1.5-1.75 yrs	12-13 yrs	5-6 yrs
11	10 to 12		2nd premolar	2.25-2.5 yrs	13-14 yrs	6-7 yrs
11	10 to 12	2nd premolar		2-2.5 yrs	12-14 yrs	6-7 yrs
11	11 to 12	canine		4-5 mos	13-15 yrs	6-7 yrs
12	11 to 13		2nd molar	2.5-3 yrs	14-15 yrs	7-8 yrs
12	12 to 13	2nd molar		2.5 yrs	14-16 yrs	7-8 yrs
20	17 to 21		3rd molar	8-10 yrs	18-25 yrs	12-16 yrs
20	17 to 21	3rd molar		7-8 yrs	18-25 yrs	12-16 yrs

Ø  CRAP: The third pair of perm teeth to erupt in normal sequence is Mn lateral incisors (1996 Q53)???

·         UNLESS, they asked for 3^rd pair of succedaneous!!!

§  (Looks like 5^th pair to me, unless you go by molars – centrals – laterals, in which case, why specify Mn laterals?)

 

Ø  1^st succedaneous to erupt is the Mn central incisor at 6-7 yrs old (don’t get clowned – Mn M1 is not succedaneous)

§  Permanent max centrals erupt just after at 7-8 yrs

§  Permanent max laterals erupt at 8-9 yrs

Ø  6 yr old

§  Presents with all 20 primary and 4 perm 1^st molars

§  First sign of mixed dentition à Mn Molars at age 6

Ø  Ordinarily, a 6-year-old would have the following teeth clinically visible:

§  All primary teeth & permanent M1s

Ø  7 yr old (another Q said 6 ½ year old)

§  Presents with 18 primary and 6 perm teeth

·         4 perm molars

·         2 mand perm central incisors

§  On a panoramic radiograph of a 7-year-old, the dentist will expect to see all of the following:

·         Primary Mx laterals w/ partially resorbed roots

·         Partially erupted Mx centrals w/ incomplete root closure at the apex

·         Partially erupted Mn laterals w/ incomplete root closure at the apex

·         Fully erupted Mn M1s w/ incomplete root formation & non-closure at the apex

·         Would NOT find – fully erupted Mn centrals w/ complete root formation and closure at the apex (it takes 2-3 years)

Ø  At 8 years of age

§  The teeth normally present are perm central & lateral incisors, primary canines & molars, permanent first molars

§  The Perm Mx M1 has no distal contact (it does have a mesial contact with the primary Mx M2)

Ø  At 9 years of age,

§  12 primary teeth remain in the mouth (Primary C9 and 2 Molars per quadrant)

Ø  At 10 years of age

§  The perm teeth expected are central & lateral incisors, first premolars, and first molars (What about Mn Canines??)

§  One would expect the root of the perm M1s to be finished forming & calcifying

§  One would expect primary tooth ‘H’ (primary Mx canine) to be mobile due to the erupting succedaneous tooth

·         BAD Q, hope you don’t get it

·         CAREFUL, because ‘J’ was also an option, which is the PM2 coming in to replace Primary M2

Ø  The first perm tooth to erupt is generally the Mn M1

§  The earliest indication of a mixed dentition consists of the primary dentition and the Mn M1s

·         The earliest indication is not the exfoliation of any primary tooth

Ø  The last perm incisors to erupt are the Mx laterals

Ø  Perm PM1 replaces primary M1

Ø  The earliest age by which the roots of the Mx PM1 are completely formed is 12-13 years

§  Typically eruption is 10, then 2-3 years for root completion

Ø  At age 26, the third molars are fully erupted with a complete root structure

Ø  The perm Mn arch is the only arch (prim or perm) in which the canine erupts before the tooth immediately distal to it

§  In Primary, Remember M1 is the distal tooth and it erupts at 12 months!!!!, canines in Mn at 16, Mx at 19 months

v  3 Cardinal Eruption Rules:

Ø  1)  Girls teeth erupt BEFORE Boys

Ø  2)  Mn erupt BEFORE Mx

Ø  3)  Teeth of slender kids erupt BEFORE fat kids, (so much to get through)

v  Teeth usually erupt in pairs – one on the left & one on the right

v  The follicles of the developing permanent incisors are in a position lingual to the deciduous roots

v  Eruption problems:

Ø  In cases of delayed resorption of primary incisors, the permanent incisors may be expected to erupt lingual to the normal arch form