Development of the Permanent Dentition Flashcards
Nolla’s 10 stages of Calcification (main ones)
2 - initial calcification
6 - eruptive movement begins (crown formation complete)
8 - alveolar crest pierced (2/3 root development)
9 - gingival margin pierced (3/4 root development)
Interval b/n stage 6 and full interdigitation is about 5 yrs
Eruption Sequence
Girls 5 months faster than boys
6,1,2,4,3,5,7 and 6,1,2,4,5,3,7 are most common in maxilla
(6,1),2,3,4,5,7 and (6,1),2,4,3,5,7 are most common in mandible
Time of Eruption
Tooth - Maxilla - Mandible
1 - (7-8) - (6-7) 2 - (8-9) - (7-8) 3 - (11-12) - (9-10) 4 - (10-11) - (10-12) 5 - (10-12) - (11-12) 6 - (6-7) - (6-7) 7 - (12-13) - (11-13) 8 - (17-21) - (17-21)
Calcification times
Birth - 1st molars 6m - ant teeth except max laterals 12m - max laterals 18m - 1st bicuspids 24m - 2nd bicuspids 30m - 2nd molars
Key times to remember - hard tissue
Hard tissue beings to enamel completion: 4-5 yrs, except 1st molar (3) and cuspid (6)
Hard tissue begins to root completion: 10 yrs except for cuspids (13)
Eruption to root completion: 3 years
Lines or Retzius
Incremental lines of rhythmic deposition of successive layers of normally calcified and hypocalcified enamel during tooth development
White, horizontal streaks
Start at incisal edge or cusp tips
Fluorosis
caused by excessive ingestion of fluoride during tooth formation
good to start early, but make sure it is just a brush of toothpaste
Fluorosis vs. Decalcification
F: horizontal striations
D: gingival lines
Factors Affecting eruption
Genetics - sequence & timing mostly genetically controlled
Nutrition
Premature Loss of Primary Tooth - may accelerate or slow the speed of eruption depending on the circumstances
Ectopic Eruption
abnormal direction of tooth eruption and can occur with any tooth
Ectopic Eruption: incisor
1s erupt and are large enough to take out one of the Bs. The remaining B is not mobile and should be extracted to prevent further midline deviation
Cuspid Impaction Facts
2-3% of adolescent population more in females and maxilla
2/3 of max impactions are palatal
85% of palatally impacted canines had sufficient space for eruption
Guidance theory: canine erupts along root of lateral incisor, serving as a guide, and if the root of lateral incisor is absent or malformed, canine will not erupt
Absence of Permanent Teeth
4-6% congenital absence
commonly missing in order:
1 - mand 2nd premolar
2 - max lateral incisor
3 - max 2nd premolar
Dens Invagnatus
Invagination of the enamel
Max permanent laterals most common, barrel shape
Possible communication to pulp chamber
Sealant or composite ASAP
An “End to End” Molar in the permanent dentition is a Class II molar relationship
AN “END TO END” MOLAR IN THE PERMANENT DENTITION IS A CLASS II MOLAR
Cuspid Classification
Neutro
Disto
Mesio
same as primary dentition
upper is a half step behind lowers
Divisions of Class II classification
Division I - excess OJ, protrusive profile, overangulated max incisors, lip under max 1s
Division II - rabbited max central incisors, minimal OJ, deep bite, overlapped max laterals, dec lower face height
Subdivision - 1 side
Changes in Arch Length and Overbite
Arch length decreases: late mesial shift, mesial drift, interproximal wear/ does not affect interarch relationships
Overbite: dec in primary dentition/ inc in mixed dentition/ OB/OJ relatively stable in adult
Changes in Arch Width
Intercanine and intermolar growth
- sig. inc b/n 3 and 13 yrs
- mand intercanine width established by 8 yrs
- after permanent teeth erupted, slight dec in arch width in intercanine area
max growth wider until 13, mand growth wider until 8
6 Keys to occlusion
1: Class * molar relationship
2: mesial crown angulation
3: proper crown inclination
4: no rotations
5: tight contacts
6: flat occlussal plane
Types of Faces
Brachycephalic - broad and short
Dolichocephalic - long and narrow
Mesocephalic - normal
