CH. 16 Dentition

what is the significance of lobe-finned fishes with supporting bones

lobe finned fishes (precursors of tetrapods) several bones:

• upper jaw = pre-maxilla (incisive bone), maxilla, lacrimal jugal, squamosal, quadrate

• lower jaw = dentary, splenial, angular, suprangular, articular, coronoid, preauricular

on land the skull became more simplified through fusion + elimination of bones

• in humans = 1 maxilla: 1 mandible

what are the 3 sets of dental succession

single set = monophyodonts

2-sets = diphyodont

multiple sets = polyphyodont

single set

monophyodont

• whales

2-sets

diphyodont

• mammals

multiple sets

polyphyodont

• elephant, kangaroo, manatees

what is significant about elephants teeth

elephants have 3 sets of molars (including one that regenerates) in old age when it stops erupting the elephant dies

dental formula

• 2 rows represent upper + lower arches

• 1 digit count per tooth (0 if empty) seperated by (.)

• human dental formula is 2.1.2.3/2.1.2.3

what is typical of the dental timeline

• all dental follicles formed before birth (doesn’t mean all teeth form within same timing)

• developmental timeline is symmetric between sides + very similar between arches (but not the same)

• root is completed years after crown erupts + long after eruption

what is the case for permanent teeth developmentally

• perm. teeth develop later than deciduous teeth in ALL phases but there is extensive overlap between them

how does the developing teeth form the arch

development from mesial to distal with in each tooth class with extensive overlap

• first molar (permanent) erupts earlier than other permanent teeth

• perm. molars 1-3 dont replace ANYTHING

what tooth marks mixed dentition

permanent molar 1 marks the start of mixed dentition

tooth eruption

tooth breaks the skin of the gingiva and becomes visible in the mouth

what kinds of movement allow for tooth eruption

tooth is moved by gradual changes in periodontal ligament attachments

what is the default occurrence for transitioning dendition

20 primary teeth are replaced with 32 permanent teeth

• buds of succedaneous teeth develop deep to primary teeth

• first molar is the first permanent tooth to erupt

• permanent canines erupt after premolars only in the maxillary arch

what is typical for tooth numbering

• most people have 20 milk teeth and 32 perm. teeth

• 20-23% lack one or more 3rd molars

hypodontia

• one or more tooth is missing (other than 3rd molar)

• 3.5-8% of the population

• typically missing 2nd premolar and lateral incisor

• usually describes children/developing dentition

oligodontia

• 5 or more missing teeth

• usually describes elderly/developmental issues/genetics

anodontia

• all deciduous/permanent teeth missing

• full denture prep (severe oligodontia develops into anodontia)

• usually part of genetic syndrome affecting ectoderm (smoking)

hyperdontia

• one or more supernumerary teeth

• usually posterior to last molar/ really anywhere usually dislocated ot a better location

which tooth is commonly impacted

• wisdom teeth

under what conditions is there safe impacted teeth

• may never erupt

• may not cause complications

when is extraction advised for impacted teeth

• may press roots of other teeth

• cause root/tooth resorption

• cause root crowding

• cause periodontal disease

• may contract caries